[PATCH 00/22] add support for Clang LTO

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Sami Tolvanen

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Jun 24, 2020, 4:32:48 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
This patch series adds support for building x86_64 and arm64 kernels
with Clang's Link Time Optimization (LTO).

In addition to performance, the primary motivation for LTO is to allow
Clang's Control-Flow Integrity (CFI) to be used in the kernel. Google's
Pixel devices have shipped with LTO+CFI kernels since 2018.

Most of the patches are build system changes for handling LLVM bitcode,
which Clang produces with LTO instead of ELF object files, postponing
ELF processing until a later stage, and ensuring initcall ordering.

Note that first objtool patch in the series is already in linux-next,
but as it's needed with LTO, I'm including it also here to make testing
easier.

Sami Tolvanen (22):
objtool: use sh_info to find the base for .rela sections
kbuild: add support for Clang LTO
kbuild: lto: fix module versioning
kbuild: lto: fix recordmcount
kbuild: lto: postpone objtool
kbuild: lto: limit inlining
kbuild: lto: merge module sections
kbuild: lto: remove duplicate dependencies from .mod files
init: lto: ensure initcall ordering
init: lto: fix PREL32 relocations
pci: lto: fix PREL32 relocations
modpost: lto: strip .lto from module names
scripts/mod: disable LTO for empty.c
efi/libstub: disable LTO
drivers/misc/lkdtm: disable LTO for rodata.o
arm64: export CC_USING_PATCHABLE_FUNCTION_ENTRY
arm64: vdso: disable LTO
arm64: allow LTO_CLANG and THINLTO to be selected
x86, vdso: disable LTO only for vDSO
x86, ftrace: disable recordmcount for ftrace_make_nop
x86, relocs: Ignore L4_PAGE_OFFSET relocations
x86, build: allow LTO_CLANG and THINLTO to be selected

.gitignore | 1 +
Makefile | 27 ++-
arch/Kconfig | 65 +++++++
arch/arm64/Kconfig | 2 +
arch/arm64/Makefile | 1 +
arch/arm64/kernel/vdso/Makefile | 4 +-
arch/x86/Kconfig | 2 +
arch/x86/Makefile | 5 +
arch/x86/entry/vdso/Makefile | 5 +-
arch/x86/kernel/ftrace.c | 1 +
arch/x86/tools/relocs.c | 1 +
drivers/firmware/efi/libstub/Makefile | 2 +
drivers/misc/lkdtm/Makefile | 1 +
include/asm-generic/vmlinux.lds.h | 12 +-
include/linux/compiler-clang.h | 4 +
include/linux/compiler.h | 2 +-
include/linux/compiler_types.h | 4 +
include/linux/init.h | 78 +++++++-
include/linux/pci.h | 15 +-
kernel/trace/ftrace.c | 1 +
lib/Kconfig.debug | 2 +-
scripts/Makefile.build | 55 +++++-
scripts/Makefile.lib | 6 +-
scripts/Makefile.modfinal | 40 +++-
scripts/Makefile.modpost | 26 ++-
scripts/generate_initcall_order.pl | 270 ++++++++++++++++++++++++++
scripts/link-vmlinux.sh | 100 +++++++++-
scripts/mod/Makefile | 1 +
scripts/mod/modpost.c | 16 +-
scripts/mod/modpost.h | 9 +
scripts/mod/sumversion.c | 6 +-
scripts/module-lto.lds | 26 +++
scripts/recordmcount.c | 3 +-
tools/objtool/elf.c | 2 +-
34 files changed, 737 insertions(+), 58 deletions(-)
create mode 100755 scripts/generate_initcall_order.pl
create mode 100644 scripts/module-lto.lds


base-commit: 26e122e97a3d0390ebec389347f64f3730fdf48f
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:32:52 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen, Josh Poimboeuf
ELF doesn't require .rela section names to match the base section. Use
the section index in sh_info to find the section instead of looking it
up by name.

LLD, for example, generates a .rela section that doesn't match the base
section name when we merge sections in a linker script for a binary
compiled with -ffunction-sections.

Signed-off-by: Sami Tolvanen <samito...@google.com>
Signed-off-by: Josh Poimboeuf <jpoi...@redhat.com>
Reviewed-by: Kees Cook <kees...@chromium.org>
---
tools/objtool/elf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 84225679f96d..c1ba92abaa03 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -502,7 +502,7 @@ static int read_relas(struct elf *elf)
if (sec->sh.sh_type != SHT_RELA)
continue;

- sec->base = find_section_by_name(elf, sec->name + 5);
+ sec->base = find_section_by_index(elf, sec->sh.sh_info);
if (!sec->base) {
WARN("can't find base section for rela section %s",
sec->name);
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:32:56 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
This change adds build system support for Clang's Link Time
Optimization (LTO). With -flto, instead of ELF object files, Clang
produces LLVM bitcode, which is compiled into native code at link
time, allowing the final binary to be optimized globally. For more
details, see:

https://llvm.org/docs/LinkTimeOptimization.html

The Kconfig option CONFIG_LTO_CLANG is implemented as a choice,
which defaults to LTO being disabled. To use LTO, the architecture
must select ARCH_SUPPORTS_LTO_CLANG and support:

- compiling with Clang,
- compiling inline assembly with Clang's integrated assembler,
- and linking with LLD.

While using full LTO results in the best runtime performance, the
compilation is not scalable in time or memory. CONFIG_THINLTO
enables ThinLTO, which allows parallel optimization and faster
incremental builds. ThinLTO is used by default if the architecture
also selects ARCH_SUPPORTS_THINLTO:

https://clang.llvm.org/docs/ThinLTO.html

To enable LTO, LLVM tools must be used to handle bitcode files. The
easiest way is to pass the LLVM=1 option to make:

$ make LLVM=1 defconfig
$ scripts/config -e LTO_CLANG
$ make LLVM=1

Alternatively, at least the following LLVM tools must be used:

CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm

To prepare for LTO support with other compilers, common parts are
gated behind the CONFIG_LTO option, and LTO can be disabled for
specific files by filtering out CC_FLAGS_LTO.

Note that support for DYNAMIC_FTRACE and MODVERSIONS are added in
follow-up patches.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
Makefile | 16 ++++++++
arch/Kconfig | 66 +++++++++++++++++++++++++++++++
include/asm-generic/vmlinux.lds.h | 11 ++++--
scripts/Makefile.build | 9 ++++-
scripts/Makefile.modfinal | 9 ++++-
scripts/Makefile.modpost | 24 ++++++++++-
scripts/link-vmlinux.sh | 32 +++++++++++----
7 files changed, 151 insertions(+), 16 deletions(-)

diff --git a/Makefile b/Makefile
index ac2c61c37a73..0c7fe6fb2143 100644
--- a/Makefile
+++ b/Makefile
@@ -886,6 +886,22 @@ KBUILD_CFLAGS += $(CC_FLAGS_SCS)
export CC_FLAGS_SCS
endif

+ifdef CONFIG_LTO_CLANG
+ifdef CONFIG_THINLTO
+CC_FLAGS_LTO_CLANG := -flto=thin $(call cc-option, -fsplit-lto-unit)
+KBUILD_LDFLAGS += --thinlto-cache-dir=.thinlto-cache
+else
+CC_FLAGS_LTO_CLANG := -flto
+endif
+CC_FLAGS_LTO_CLANG += -fvisibility=default
+endif
+
+ifdef CONFIG_LTO
+CC_FLAGS_LTO := $(CC_FLAGS_LTO_CLANG)
+KBUILD_CFLAGS += $(CC_FLAGS_LTO)
+export CC_FLAGS_LTO
+endif
+
# arch Makefile may override CC so keep this after arch Makefile is included
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)

diff --git a/arch/Kconfig b/arch/Kconfig
index 8cc35dc556c7..e00b122293f8 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -552,6 +552,72 @@ config SHADOW_CALL_STACK
reading and writing arbitrary memory may be able to locate them
and hijack control flow by modifying the stacks.

+config LTO
+ bool
+
+config ARCH_SUPPORTS_LTO_CLANG
+ bool
+ help
+ An architecture should select this option if it supports:
+ - compiling with Clang,
+ - compiling inline assembly with Clang's integrated assembler,
+ - and linking with LLD.
+
+config ARCH_SUPPORTS_THINLTO
+ bool
+ help
+ An architecture should select this option if it supports Clang's
+ ThinLTO.
+
+config THINLTO
+ bool "Clang ThinLTO"
+ depends on LTO_CLANG && ARCH_SUPPORTS_THINLTO
+ default y
+ help
+ This option enables Clang's ThinLTO, which allows for parallel
+ optimization and faster incremental compiles. More information
+ can be found from Clang's documentation:
+
+ https://clang.llvm.org/docs/ThinLTO.html
+
+choice
+ prompt "Link Time Optimization (LTO)"
+ default LTO_NONE
+ help
+ This option enables Link Time Optimization (LTO), which allows the
+ compiler to optimize binaries globally.
+
+ If unsure, select LTO_NONE.
+
+config LTO_NONE
+ bool "None"
+
+config LTO_CLANG
+ bool "Clang's Link Time Optimization (EXPERIMENTAL)"
+ depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD
+ depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
+ depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
+ depends on ARCH_SUPPORTS_LTO_CLANG
+ depends on !FTRACE_MCOUNT_RECORD
+ depends on !KASAN
+ depends on !MODVERSIONS
+ select LTO
+ help
+ This option enables Clang's Link Time Optimization (LTO), which
+ allows the compiler to optimize the kernel globally. If you enable
+ this option, the compiler generates LLVM bitcode instead of ELF
+ object files, and the actual compilation from bitcode happens at
+ the LTO link step, which may take several minutes depending on the
+ kernel configuration. More information can be found from LLVM's
+ documentation:
+
+ https://llvm.org/docs/LinkTimeOptimization.html
+
+ To select this option, you also need to use LLVM tools to handle
+ the bitcode by passing LLVM=1 to make.
+
+endchoice
+
config HAVE_ARCH_WITHIN_STACK_FRAMES
bool
help
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index db600ef218d7..78079000c05a 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -89,15 +89,18 @@
* .data. We don't want to pull in .data..other sections, which Linux
* has defined. Same for text and bss.
*
+ * With LTO_CLANG, the linker also splits sections by default, so we need
+ * these macros to combine the sections during the final link.
+ *
* RODATA_MAIN is not used because existing code already defines .rodata.x
* sections to be brought in with rodata.
*/
-#ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
+#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG)
#define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
-#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..LPBX*
+#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral*
#define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]*
-#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]*
-#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]*
+#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L*
+#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..compoundliteral*
#define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]*
#else
#define TEXT_MAIN .text
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 2e8810b7e5ed..f307e708a1b7 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -108,7 +108,7 @@ endif
# ---------------------------------------------------------------------------

quiet_cmd_cc_s_c = CC $(quiet_modtag) $@
- cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) $(DISABLE_LTO) -fverbose-asm -S -o $@ $<
+ cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS) $(CC_FLAGS_LTO), $(c_flags)) -fverbose-asm -S -o $@ $<

$(obj)/%.s: $(src)/%.c FORCE
$(call if_changed_dep,cc_s_c)
@@ -424,8 +424,15 @@ $(obj)/lib.a: $(lib-y) FORCE
# Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
# module is turned into a multi object module, $^ will contain header file
# dependencies recorded in the .*.cmd file.
+ifdef CONFIG_LTO_CLANG
+quiet_cmd_link_multi-m = AR [M] $@
+cmd_link_multi-m = \
+ rm -f $@; \
+ $(AR) rcsTP$(KBUILD_ARFLAGS) $@ $(filter %.o,$^)
+else
quiet_cmd_link_multi-m = LD [M] $@
cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
+endif

$(multi-used-m): FORCE
$(call if_changed,link_multi-m)
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 411c1e600e7d..1005b147abd0 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -6,6 +6,7 @@
PHONY := __modfinal
__modfinal:

+include $(objtree)/include/config/auto.conf
include $(srctree)/scripts/Kbuild.include

# for c_flags
@@ -29,6 +30,12 @@ quiet_cmd_cc_o_c = CC [M] $@

ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)

+ifdef CONFIG_LTO_CLANG
+# With CONFIG_LTO_CLANG, reuse the object file we compiled for modpost to
+# avoid a second slow LTO link
+prelink-ext := .lto
+endif
+
quiet_cmd_ld_ko_o = LD [M] $@
cmd_ld_ko_o = \
$(LD) -r $(KBUILD_LDFLAGS) \
@@ -37,7 +44,7 @@ quiet_cmd_ld_ko_o = LD [M] $@
-o $@ $(filter %.o, $^); \
$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)

-$(modules): %.ko: %.o %.mod.o $(KBUILD_LDS_MODULE) FORCE
+$(modules): %.ko: %$(prelink-ext).o %.mod.o $(KBUILD_LDS_MODULE) FORCE
+$(call if_changed,ld_ko_o)

targets += $(modules) $(modules:.ko=.mod.o)
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 3651cbf6ad49..9ced8aecd579 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -102,12 +102,32 @@ $(input-symdump):
@echo >&2 'WARNING: Symbol version dump "$@" is missing.'
@echo >&2 ' Modules may not have dependencies or modversions.'

+ifdef CONFIG_LTO_CLANG
+# With CONFIG_LTO_CLANG, .o files might be LLVM bitcode, so we need to run
+# LTO to compile them into native code before running modpost
+prelink-ext = .lto
+
+quiet_cmd_cc_lto_link_modules = LTO [M] $@
+cmd_cc_lto_link_modules = \
+ $(LD) $(ld_flags) -r -o $@ \
+ --whole-archive $(filter-out FORCE,$^)
+
+%.lto.o: %.o FORCE
+ $(call if_changed,cc_lto_link_modules)
+
+PHONY += FORCE
+FORCE:
+
+endif
+
+modules := $(sort $(shell cat $(MODORDER)))
+
# Read out modules.order to pass in modpost.
# Otherwise, allmodconfig would fail with "Argument list too long".
quiet_cmd_modpost = MODPOST $@
- cmd_modpost = sed 's/ko$$/o/' $< | $(MODPOST) -T -
+ cmd_modpost = sed 's/\.ko$$/$(prelink-ext)\.o/' $< | $(MODPOST) -T -

-$(output-symdump): $(MODORDER) $(input-symdump) FORCE
+$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(prelink-ext).o) FORCE
$(call if_changed,modpost)

targets += $(output-symdump)
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 92dd745906f4..a681b3b6722e 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -52,6 +52,14 @@ modpost_link()
${KBUILD_VMLINUX_LIBS} \
--end-group"

+ if [ -n "${CONFIG_LTO_CLANG}" ]; then
+ # This might take a while, so indicate that we're doing
+ # an LTO link
+ info LTO ${1}
+ else
+ info LD ${1}
+ fi
+
${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${objects}
}

@@ -99,13 +107,22 @@ vmlinux_link()
fi

if [ "${SRCARCH}" != "um" ]; then
- objects="--whole-archive \
- ${KBUILD_VMLINUX_OBJS} \
- --no-whole-archive \
- --start-group \
- ${KBUILD_VMLINUX_LIBS} \
- --end-group \
- ${@}"
+ if [ -n "${CONFIG_LTO_CLANG}" ]; then
+ # Use vmlinux.o instead of performing the slow LTO
+ # link again.
+ objects="--whole-archive \
+ vmlinux.o \
+ --no-whole-archive \
+ ${@}"
+ else
+ objects="--whole-archive \
+ ${KBUILD_VMLINUX_OBJS} \
+ --no-whole-archive \
+ --start-group \
+ ${KBUILD_VMLINUX_LIBS} \
+ --end-group \
+ ${@}"
+ fi

${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux} \
${strip_debug#-Wl,} \
@@ -270,7 +287,6 @@ fi;
${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1

#link vmlinux.o
-info LD vmlinux.o
modpost_link vmlinux.o
objtool_link vmlinux.o

--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:01 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
With CONFIG_MODVERSIONS, version information is linked into each
compilation unit that exports symbols. With LTO, we cannot use this
method as all C code is compiled into LLVM bitcode instead. This
change collects symbol versions into .symversions files and merges
them in link-vmlinux.sh where they are all linked into vmlinux.o at
the same time.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
.gitignore | 1 +
Makefile | 3 ++-
arch/Kconfig | 1 -
scripts/Makefile.build | 33 +++++++++++++++++++++++++++++++--
scripts/Makefile.modpost | 2 ++
scripts/link-vmlinux.sh | 25 ++++++++++++++++++++++++-
6 files changed, 60 insertions(+), 5 deletions(-)

diff --git a/.gitignore b/.gitignore
index 87b9dd8a163b..51b02c2f2826 100644
--- a/.gitignore
+++ b/.gitignore
@@ -41,6 +41,7 @@
*.so.dbg
*.su
*.symtypes
+*.symversions
*.tab.[ch]
*.tar
*.xz
diff --git a/Makefile b/Makefile
index 0c7fe6fb2143..161ad0d1f77f 100644
--- a/Makefile
+++ b/Makefile
@@ -1793,7 +1793,8 @@ clean: $(clean-dirs)
-o -name '.tmp_*.o.*' \
-o -name '*.c.[012]*.*' \
-o -name '*.ll' \
- -o -name '*.gcno' \) -type f -print | xargs rm -f
+ -o -name '*.gcno' \
+ -o -name '*.*.symversions' \) -type f -print | xargs rm -f

# Generate tags for editors
# ---------------------------------------------------------------------------
diff --git a/arch/Kconfig b/arch/Kconfig
index e00b122293f8..87488fe1e6b8 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -600,7 +600,6 @@ config LTO_CLANG
depends on ARCH_SUPPORTS_LTO_CLANG
depends on !FTRACE_MCOUNT_RECORD
depends on !KASAN
- depends on !MODVERSIONS
select LTO
help
This option enables Clang's Link Time Optimization (LTO), which
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index f307e708a1b7..5c0bbb6ddfcf 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -163,6 +163,15 @@ ifdef CONFIG_MODVERSIONS
# the actual value of the checksum generated by genksyms
# o remove .tmp_<file>.o to <file>.o

+ifdef CONFIG_LTO_CLANG
+# Generate .o.symversions files for each .o with exported symbols, and link these
+# to the kernel and/or modules at the end.
+cmd_modversions_c = \
+ if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then \
+ $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
+ > $@.symversions; \
+ fi;
+else
cmd_modversions_c = \
if $(OBJDUMP) -h $@ | grep -q __ksymtab; then \
$(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
@@ -174,6 +183,7 @@ cmd_modversions_c = \
rm -f $(@D)/.tmp_$(@F:.o=.ver); \
fi
endif
+endif

ifdef CONFIG_FTRACE_MCOUNT_RECORD
ifndef CC_USING_RECORD_MCOUNT
@@ -389,6 +399,18 @@ $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
$(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ;
$(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;

+# combine symversions for later processing
+quiet_cmd_update_lto_symversions = SYMVER $@
+ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
+ cmd_update_lto_symversions = \
+ rm -f $@.symversions \
+ $(foreach n, $(filter-out FORCE,$^), \
+ $(if $(wildcard $(n).symversions), \
+ ; cat $(n).symversions >> $@.symversions))
+else
+ cmd_update_lto_symversions = echo >/dev/null
+endif
+
#
# Rule to compile a set of .o files into one .a file (without symbol table)
#
@@ -396,8 +418,11 @@ $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
quiet_cmd_ar_builtin = AR $@
cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)

+quiet_cmd_ar_and_symver = AR $@
+ cmd_ar_and_symver = $(cmd_update_lto_symversions); $(cmd_ar_builtin)
+
$(obj)/built-in.a: $(real-obj-y) FORCE
- $(call if_changed,ar_builtin)
+ $(call if_changed,ar_and_symver)

#
# Rule to create modules.order file
@@ -417,8 +442,11 @@ $(obj)/modules.order: $(obj-m) FORCE
#
# Rule to compile a set of .o files into one .a file (with symbol table)
#
+quiet_cmd_ar_lib = AR $@
+ cmd_ar_lib = $(cmd_update_lto_symversions); $(cmd_ar)
+
$(obj)/lib.a: $(lib-y) FORCE
- $(call if_changed,ar)
+ $(call if_changed,ar_lib)

# NOTE:
# Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
@@ -427,6 +455,7 @@ $(obj)/lib.a: $(lib-y) FORCE
ifdef CONFIG_LTO_CLANG
quiet_cmd_link_multi-m = AR [M] $@
cmd_link_multi-m = \
+ $(cmd_update_lto_symversions); \
rm -f $@; \
$(AR) rcsTP$(KBUILD_ARFLAGS) $@ $(filter %.o,$^)
else
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 9ced8aecd579..42dbdc2bbf73 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -110,6 +110,8 @@ prelink-ext = .lto
quiet_cmd_cc_lto_link_modules = LTO [M] $@
cmd_cc_lto_link_modules = \
$(LD) $(ld_flags) -r -o $@ \
+ $(shell [ -s $(@:.lto.o=.o.symversions) ] && \
+ echo -T $(@:.lto.o=.o.symversions)) \
--whole-archive $(filter-out FORCE,$^)

%.lto.o: %.o FORCE
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index a681b3b6722e..69a6d7254e28 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -39,11 +39,28 @@ info()
fi
}

+# If CONFIG_LTO_CLANG is selected, collect generated symbol versions into
+# .tmp_symversions.lds
+gen_symversions()
+{
+ info GEN .tmp_symversions.lds
+ rm -f .tmp_symversions.lds
+
+ for a in ${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}; do
+ for o in $(${AR} t $a 2>/dev/null); do
+ if [ -f ${o}.symversions ]; then
+ cat ${o}.symversions >> .tmp_symversions.lds
+ fi
+ done
+ done
+}
+
# Link of vmlinux.o used for section mismatch analysis
# ${1} output file
modpost_link()
{
local objects
+ local lds=""

objects="--whole-archive \
${KBUILD_VMLINUX_OBJS} \
@@ -53,6 +70,11 @@ modpost_link()
--end-group"

if [ -n "${CONFIG_LTO_CLANG}" ]; then
+ if [ -n "${CONFIG_MODVERSIONS}" ]; then
+ gen_symversions
+ lds="${lds} -T .tmp_symversions.lds"
+ fi
+
# This might take a while, so indicate that we're doing
# an LTO link
info LTO ${1}
@@ -60,7 +82,7 @@ modpost_link()
info LD ${1}
fi

- ${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${objects}
+ ${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${lds} ${objects}
}

objtool_link()
@@ -238,6 +260,7 @@ cleanup()
{
rm -f .btf.*
rm -f .tmp_System.map
+ rm -f .tmp_symversions.lds
rm -f .tmp_vmlinux*
rm -f System.map
rm -f vmlinux
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:04 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
With LTO, LLVM bitcode won't be compiled into native code until
modpost_link. This change postpones calls to recordmcount until after
this step.

In order to exclude specific functions from inspection, we add a new
code section .text..nomcount, which we tell recordmcount to ignore, and
a __nomcount attribute for moving functions to this section.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
Makefile | 2 +-
arch/Kconfig | 2 +-
include/asm-generic/vmlinux.lds.h | 1 +
include/linux/compiler-clang.h | 4 ++++
include/linux/compiler_types.h | 4 ++++
kernel/trace/ftrace.c | 1 +
scripts/Makefile.build | 9 +++++++++
scripts/Makefile.modfinal | 18 ++++++++++++++++--
scripts/link-vmlinux.sh | 29 +++++++++++++++++++++++++++++
scripts/recordmcount.c | 3 ++-
10 files changed, 68 insertions(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index 161ad0d1f77f..3a7e5e5c17b9 100644
--- a/Makefile
+++ b/Makefile
@@ -861,7 +861,7 @@ KBUILD_AFLAGS += $(CC_FLAGS_USING)
ifdef CONFIG_DYNAMIC_FTRACE
ifdef CONFIG_HAVE_C_RECORDMCOUNT
BUILD_C_RECORDMCOUNT := y
- export BUILD_C_RECORDMCOUNT
+ export BUILD_C_RECORDMCOUNT RECORDMCOUNT_WARN
endif
endif
endif
diff --git a/arch/Kconfig b/arch/Kconfig
index 87488fe1e6b8..85b2044b927d 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -598,7 +598,7 @@ config LTO_CLANG
depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
depends on ARCH_SUPPORTS_LTO_CLANG
- depends on !FTRACE_MCOUNT_RECORD
+ depends on !FTRACE_MCOUNT_RECORD || HAVE_C_RECORDMCOUNT
depends on !KASAN
select LTO
help
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 78079000c05a..a1c902b808d0 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -565,6 +565,7 @@
*(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \
NOINSTR_TEXT \
*(.text..refcount) \
+ *(.text..nomcount) \
*(.ref.text) \
MEM_KEEP(init.text*) \
MEM_KEEP(exit.text*) \
diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index ee37256ec8bd..fd78475c0642 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -55,3 +55,7 @@
#if __has_feature(shadow_call_stack)
# define __noscs __attribute__((__no_sanitize__("shadow-call-stack")))
#endif
+
+#if defined(CONFIG_LTO_CLANG) && defined(CONFIG_FTRACE_MCOUNT_RECORD)
+#define __nomcount __attribute__((__section__(".text..nomcount")))
+#endif
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index e368384445b6..1470c9703a25 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -233,6 +233,10 @@ struct ftrace_likely_data {
# define __noscs
#endif

+#ifndef __nomcount
+# define __nomcount
+#endif
+
#ifndef asm_volatile_goto
#define asm_volatile_goto(x...) asm goto(x)
#endif
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1903b80db6eb..8e3ddb8123d9 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6062,6 +6062,7 @@ static int ftrace_cmp_ips(const void *a, const void *b)
return 0;
}

+__nomcount
static int ftrace_process_locs(struct module *mod,
unsigned long *start,
unsigned long *end)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 5c0bbb6ddfcf..64e99f4baa5b 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -187,6 +187,9 @@ endif

ifdef CONFIG_FTRACE_MCOUNT_RECORD
ifndef CC_USING_RECORD_MCOUNT
+ifndef CC_USING_PATCHABLE_FUNCTION_ENTRY
+# With LTO, we postpone recordmcount until we compile a native binary
+ifndef CONFIG_LTO_CLANG
# compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
ifdef BUILD_C_RECORDMCOUNT
ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
@@ -200,6 +203,8 @@ sub_cmd_record_mcount = \
if [ $(@) != "scripts/mod/empty.o" ]; then \
$(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)"; \
fi;
+endif # CONFIG_LTO_CLANG
+
recordmcount_source := $(srctree)/scripts/recordmcount.c \
$(srctree)/scripts/recordmcount.h
else
@@ -209,11 +214,15 @@ sub_cmd_record_mcount = perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
"$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS)" \
"$(LD) $(KBUILD_LDFLAGS)" "$(NM)" "$(RM)" "$(MV)" \
"$(if $(part-of-module),1,0)" "$(@)";
+
recordmcount_source := $(srctree)/scripts/recordmcount.pl
endif # BUILD_C_RECORDMCOUNT
+ifndef CONFIG_LTO_CLANG
cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)), \
$(sub_cmd_record_mcount))
+endif # CONFIG_LTO_CLANG
endif # CC_USING_RECORD_MCOUNT
+endif # CC_USING_PATCHABLE_FUNCTION_ENTRY
endif # CONFIG_FTRACE_MCOUNT_RECORD

ifdef CONFIG_STACK_VALIDATION
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 1005b147abd0..d168f0cfe67c 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -34,10 +34,24 @@ ifdef CONFIG_LTO_CLANG
# With CONFIG_LTO_CLANG, reuse the object file we compiled for modpost to
# avoid a second slow LTO link
prelink-ext := .lto
-endif
+
+# ELF processing was skipped earlier because we didn't have native code,
+# so let's now process the prelinked binary before we link the module.
+
+ifdef CONFIG_FTRACE_MCOUNT_RECORD
+ifndef CC_USING_RECORD_MCOUNT
+ifndef CC_USING_PATCHABLE_FUNCTION_ENTRY
+cmd_ld_ko_o += $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) \
+ $(@:.ko=$(prelink-ext).o);
+
+endif # CC_USING_PATCHABLE_FUNCTION_ENTRY
+endif # CC_USING_RECORD_MCOUNT
+endif # CONFIG_FTRACE_MCOUNT_RECORD
+
+endif # CONFIG_LTO_CLANG

quiet_cmd_ld_ko_o = LD [M] $@
- cmd_ld_ko_o = \
+ cmd_ld_ko_o += \
$(LD) -r $(KBUILD_LDFLAGS) \
$(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE) \
$(addprefix -T , $(KBUILD_LDS_MODULE)) \
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 69a6d7254e28..c72f5d0238f1 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -108,6 +108,29 @@ objtool_link()
fi
}

+# If CONFIG_LTO_CLANG is selected, we postpone running recordmcount until
+# we have compiled LLVM IR to an object file.
+recordmcount()
+{
+ if [ "${CONFIG_LTO_CLANG} ${CONFIG_FTRACE_MCOUNT_RECORD}" != "y y" ]; then
+ return
+ fi
+
+ if [ -n "${CC_USING_RECORD_MCOUNT}" ]; then
+ return
+ fi
+ if [ -n "${CC_USING_PATCHABLE_FUNCTION_ENTRY}" ]; then
+ return
+ fi
+
+ local flags=""
+
+ [ -n "${RECORDMCOUNT_WARN}" ] && flags="-w"
+
+ info MCOUNT $*
+ ${objtree}/scripts/recordmcount ${flags} $*
+}
+
# Link of vmlinux
# ${1} - output file
# ${2}, ${3}, ... - optional extra .o files
@@ -316,6 +339,12 @@ objtool_link vmlinux.o
# modpost vmlinux.o to check for section mismatches
${MAKE} -f "${srctree}/scripts/Makefile.modpost" MODPOST_VMLINUX=1

+if [ -n "${CONFIG_LTO_CLANG}" ]; then
+ # If we postponed ELF processing steps due to LTO, process
+ # vmlinux.o instead.
+ recordmcount vmlinux.o
+fi
+
info MODINFO modules.builtin.modinfo
${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo
info GEN modules.builtin
diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
index 7225107a9aaf..9e9f10b4d649 100644
--- a/scripts/recordmcount.c
+++ b/scripts/recordmcount.c
@@ -404,7 +404,8 @@ static uint32_t (*w2)(uint16_t);
/* Names of the sections that could contain calls to mcount. */
static int is_mcounted_section_name(char const *const txtname)
{
- return strncmp(".text", txtname, 5) == 0 ||
+ return (strncmp(".text", txtname, 5) == 0 &&
+ strcmp(".text..nomcount", txtname) != 0) ||
strcmp(".init.text", txtname) == 0 ||
strcmp(".ref.text", txtname) == 0 ||
strcmp(".sched.text", txtname) == 0 ||
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:07 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
With LTO, LLVM bitcode won't be compiled into native code until
modpost_link, or modfinal for modules. This change postpones calls
to objtool until after these steps.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
include/linux/compiler.h | 2 +-
lib/Kconfig.debug | 2 +-
scripts/Makefile.build | 2 ++
scripts/Makefile.modfinal | 15 +++++++++++++++
4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 30827f82ad62..12b115152532 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -120,7 +120,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
/* Annotate a C jump table to allow objtool to follow the code flow */
#define __annotate_jump_table __section(.rodata..c_jump_table)

-#ifdef CONFIG_DEBUG_ENTRY
+#if defined(CONFIG_DEBUG_ENTRY) || defined(CONFIG_LTO_CLANG)
/* Begin/end of an instrumentation safe region */
#define instrumentation_begin() ({ \
asm volatile("%c0:\n\t" \
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9ad9210d70a1..9fdba71c135a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -399,7 +399,7 @@ config STACK_VALIDATION

config VMLINUX_VALIDATION
bool
- depends on STACK_VALIDATION && DEBUG_ENTRY && !PARAVIRT
+ depends on STACK_VALIDATION && (DEBUG_ENTRY || LTO_CLANG) && !PARAVIRT
default y

config DEBUG_FORCE_WEAK_PER_CPU
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 64e99f4baa5b..82977350f5a6 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -226,6 +226,7 @@ endif # CC_USING_PATCHABLE_FUNCTION_ENTRY
endif # CONFIG_FTRACE_MCOUNT_RECORD

ifdef CONFIG_STACK_VALIDATION
+ifndef CONFIG_LTO_CLANG
ifneq ($(SKIP_STACK_VALIDATION),1)

__objtool_obj := $(objtree)/tools/objtool/objtool
@@ -258,6 +259,7 @@ objtool_obj = $(if $(patsubst y%,, \
$(__objtool_obj))

endif # SKIP_STACK_VALIDATION
+endif # CONFIG_LTO_CLANG
endif # CONFIG_STACK_VALIDATION

# Rebuild all objects when objtool changes, or is enabled/disabled.
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index d168f0cfe67c..9f1df2f1fab5 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -48,6 +48,21 @@ endif # CC_USING_PATCHABLE_FUNCTION_ENTRY
endif # CC_USING_RECORD_MCOUNT
endif # CONFIG_FTRACE_MCOUNT_RECORD

+ifdef CONFIG_STACK_VALIDATION
+ifneq ($(SKIP_STACK_VALIDATION),1)
+cmd_ld_ko_o += \
+ $(objtree)/tools/objtool/objtool \
+ $(if $(CONFIG_UNWINDER_ORC),orc generate,check) \
+ --module \
+ $(if $(CONFIG_FRAME_POINTER),,--no-fp) \
+ $(if $(CONFIG_GCOV_KERNEL),--no-unreachable,) \
+ $(if $(CONFIG_RETPOLINE),--retpoline,) \
+ $(if $(CONFIG_X86_SMAP),--uaccess,) \
+ $(@:.ko=$(prelink-ext).o);
+
+endif # SKIP_STACK_VALIDATION
+endif # CONFIG_STACK_VALIDATION
+
endif # CONFIG_LTO_CLANG

quiet_cmd_ld_ko_o = LD [M] $@
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:10 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen, George Burgess IV
This change limits function inlining across translation unit
boundaries in order to reduce the binary size with LTO.

The -import-instr-limit flag defines a size limit, as the number
of LLVM IR instructions, for importing functions from other TUs.
The default value is 100, and decreasing it to 5 reduces the size
of a stripped arm64 defconfig vmlinux by 11%.

Suggested-by: George Burgess IV <gb...@google.com>
Signed-off-by: Sami Tolvanen <samito...@google.com>
---
Makefile | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/Makefile b/Makefile
index 3a7e5e5c17b9..ee66513a5b66 100644
--- a/Makefile
+++ b/Makefile
@@ -894,6 +894,10 @@ else
CC_FLAGS_LTO_CLANG := -flto
endif
CC_FLAGS_LTO_CLANG += -fvisibility=default
+
+# Limit inlining across translation units to reduce binary size
+LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5
+KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG)
endif

ifdef CONFIG_LTO
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:11 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
LLD always splits sections with LTO, which increases module sizes. This
change adds a linker script that merges the split sections in the final
module and discards the .eh_frame section that LLD may generate.

Suggested-by: Nick Desaulniers <ndesau...@google.com>
Signed-off-by: Sami Tolvanen <samito...@google.com>
---
Makefile | 2 ++
scripts/module-lto.lds | 26 ++++++++++++++++++++++++++
2 files changed, 28 insertions(+)
create mode 100644 scripts/module-lto.lds

diff --git a/Makefile b/Makefile
index ee66513a5b66..9ffec5fe1737 100644
--- a/Makefile
+++ b/Makefile
@@ -898,6 +898,8 @@ CC_FLAGS_LTO_CLANG += -fvisibility=default
# Limit inlining across translation units to reduce binary size
LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5
KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG)
+
+KBUILD_LDS_MODULE += $(srctree)/scripts/module-lto.lds
endif

ifdef CONFIG_LTO
diff --git a/scripts/module-lto.lds b/scripts/module-lto.lds
new file mode 100644
index 000000000000..65884c652bf2
--- /dev/null
+++ b/scripts/module-lto.lds
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and
+ * -ffunction-sections, which increases the size of the final module.
+ * Merge the split sections in the final binary.
+ */
+SECTIONS {
+ __patchable_function_entries : { *(__patchable_function_entries) }
+
+ .bss : {
+ *(.bss .bss.[0-9a-zA-Z_]*)
+ *(.bss..L* .bss..compoundliteral*)
+ }
+
+ .data : {
+ *(.data .data.[0-9a-zA-Z_]*)
+ *(.data..L* .data..compoundliteral*)
+ }
+
+ .rodata : {
+ *(.rodata .rodata.[0-9a-zA-Z_]*)
+ *(.rodata..L* .rodata..compoundliteral*)
+ }
+
+ .text : { *(.text .text.[0-9a-zA-Z_]*) }
+}
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:13 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
With LTO, llvm-nm prints out symbols for each archive member
separately, which results in a lot of duplicate dependencies in the
.mod file when CONFIG_TRIM_UNUSED_SYMS is enabled. When a module
consists of several compilation units, the output can exceed the
default xargs command size limit and split the dependency list to
multiple lines, which results in used symbols getting trimmed.

This change removes duplicate dependencies, which will reduce the
probability of this happening and makes .mod files smaller and
easier to read.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
scripts/Makefile.build | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 82977350f5a6..82b465ce3ca0 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -291,7 +291,7 @@ endef

# List module undefined symbols (or empty line if not enabled)
ifdef CONFIG_TRIM_UNUSED_KSYMS
-cmd_undef_syms = $(NM) $< | sed -n 's/^ *U //p' | xargs echo
+cmd_undef_syms = $(NM) $< | sed -n 's/^ *U //p' | sort -u | xargs echo
else
cmd_undef_syms = echo
endif
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:16 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
With LTO, the compiler doesn't necessarily obey the link order for
initcalls, and initcall variables need globally unique names to avoid
collisions at link time.

This change exports __KBUILD_MODNAME and adds the initcall_id() macro,
which uses it together with __COUNTER__ and __LINE__ to help ensure
these variables have unique names, and moves each variable to its own
section when LTO is enabled, so the correct order can be specified using
a linker script.

The generate_initcall_ordering.pl script uses nm to find initcalls from
the object files passed to the linker, and generates a linker script
that specifies the intended order. With LTO, the script is called in
link-vmlinux.sh.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
include/linux/init.h | 52 +++++-
scripts/Makefile.lib | 6 +-
scripts/generate_initcall_order.pl | 270 +++++++++++++++++++++++++++++
scripts/link-vmlinux.sh | 14 ++
4 files changed, 333 insertions(+), 9 deletions(-)
create mode 100755 scripts/generate_initcall_order.pl

diff --git a/include/linux/init.h b/include/linux/init.h
index 212fc9e2f691..af638cd6dd52 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -184,19 +184,57 @@ extern bool initcall_debug;
* as KEEP() in the linker script.
*/

+/* Format: <modname>__<counter>_<line>_<fn> */
+#define __initcall_id(fn) \
+ __PASTE(__KBUILD_MODNAME, \
+ __PASTE(__, \
+ __PASTE(__COUNTER__, \
+ __PASTE(_, \
+ __PASTE(__LINE__, \
+ __PASTE(_, fn))))))
+
+/* Format: __<prefix>__<iid><id> */
+#define __initcall_name(prefix, __iid, id) \
+ __PASTE(__, \
+ __PASTE(prefix, \
+ __PASTE(__, \
+ __PASTE(__iid, id))))
+
+#ifdef CONFIG_LTO_CLANG
+/*
+ * With LTO, the compiler doesn't necessarily obey link order for
+ * initcalls. In order to preserve the correct order, we add each
+ * variable into its own section and generate a linker script (in
+ * scripts/link-vmlinux.sh) to specify the order of the sections.
+ */
+#define __initcall_section(__sec, __iid) \
+ #__sec ".init.." #__iid
+#else
+#define __initcall_section(__sec, __iid) \
+ #__sec ".init"
+#endif
+
#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-#define ___define_initcall(fn, id, __sec) \
+#define ____define_initcall(fn, __name, __sec) \
__ADDRESSABLE(fn) \
- asm(".section \"" #__sec ".init\", \"a\" \n" \
- "__initcall_" #fn #id ": \n" \
+ asm(".section \"" __sec "\", \"a\" \n" \
+ __stringify(__name) ": \n" \
".long " #fn " - . \n" \
".previous \n");
#else
-#define ___define_initcall(fn, id, __sec) \
- static initcall_t __initcall_##fn##id __used \
- __attribute__((__section__(#__sec ".init"))) = fn;
+#define ____define_initcall(fn, __name, __sec) \
+ static initcall_t __name __used \
+ __attribute__((__section__(__sec))) = fn;
#endif

+#define __unique_initcall(fn, id, __sec, __iid) \
+ ____define_initcall(fn, \
+ __initcall_name(initcall, __iid, id), \
+ __initcall_section(__sec, __iid))
+
+#define ___define_initcall(fn, id, __sec) \
+ __unique_initcall(fn, id, __sec, __initcall_id(fn))
+
#define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)

/*
@@ -236,7 +274,7 @@ extern bool initcall_debug;
#define __exitcall(fn) \
static exitcall_t __exitcall_##fn __exit_call = fn

-#define console_initcall(fn) ___define_initcall(fn,, .con_initcall)
+#define console_initcall(fn) ___define_initcall(fn, con, .con_initcall)

struct obs_kernel_param {
const char *str;
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 99ac59c59826..17447354b543 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -106,9 +106,11 @@ target-stem = $(basename $(patsubst $(obj)/%,%,$@))
# These flags are needed for modversions and compiling, so we define them here
# $(modname_flags) defines KBUILD_MODNAME as the name of the module it will
# end up in (or would, if it gets compiled in)
-name-fix = $(call stringify,$(subst $(comma),_,$(subst -,_,$1)))
+name-fix-token = $(subst $(comma),_,$(subst -,_,$1))
+name-fix = $(call stringify,$(call name-fix-token,$1))
basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
-modname_flags = -DKBUILD_MODNAME=$(call name-fix,$(modname))
+modname_flags = -DKBUILD_MODNAME=$(call name-fix,$(modname)) \
+ -D__KBUILD_MODNAME=$(call name-fix-token,$(modname))
modfile_flags = -DKBUILD_MODFILE=$(call stringify,$(modfile))

orig_c_flags = $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) \
diff --git a/scripts/generate_initcall_order.pl b/scripts/generate_initcall_order.pl
new file mode 100755
index 000000000000..fe83aec2b51e
--- /dev/null
+++ b/scripts/generate_initcall_order.pl
@@ -0,0 +1,270 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+#
+# Generates a linker script that specifies the correct initcall order.
+#
+# Copyright (C) 2019 Google LLC
+
+use strict;
+use warnings;
+use IO::Handle;
+use IO::Select;
+use POSIX ":sys_wait_h";
+
+my $nm = $ENV{'NM'} || die "$0: ERROR: NM not set?";
+my $objtree = $ENV{'objtree'} || '.';
+
+## currently active child processes
+my $jobs = {}; # child process pid -> file handle
+## results from child processes
+my $results = {}; # object index -> [ { level, secname }, ... ]
+
+## reads _NPROCESSORS_ONLN to determine the maximum number of processes to
+## start
+sub get_online_processors {
+ open(my $fh, "getconf _NPROCESSORS_ONLN 2>/dev/null |")
+ or die "$0: ERROR: failed to execute getconf: $!";
+ my $procs = <$fh>;
+ close($fh);
+
+ if (!($procs =~ /^\d+$/)) {
+ return 1;
+ }
+
+ return int($procs);
+}
+
+## writes results to the parent process
+## format: <file index> <initcall level> <base initcall section name>
+sub write_results {
+ my ($index, $initcalls) = @_;
+
+ # sort by the counter value to ensure the order of initcalls within
+ # each object file is correct
+ foreach my $counter (sort { $a <=> $b } keys(%{$initcalls})) {
+ my $level = $initcalls->{$counter}->{'level'};
+
+ # section name for the initcall function
+ my $secname = $initcalls->{$counter}->{'module'} . '__' .
+ $counter . '_' .
+ $initcalls->{$counter}->{'line'} . '_' .
+ $initcalls->{$counter}->{'function'};
+
+ print "$index $level $secname\n";
+ }
+}
+
+## reads a result line from a child process and adds it to the $results array
+sub read_results{
+ my ($fh) = @_;
+
+ # each child prints out a full line w/ autoflush and exits after the
+ # last line, so even if buffered I/O blocks here, it shouldn't block
+ # very long
+ my $data = <$fh>;
+
+ if (!defined($data)) {
+ return 0;
+ }
+
+ chomp($data);
+
+ my ($index, $level, $secname) = $data =~
+ /^(\d+)\ ([^\ ]+)\ (.*)$/;
+
+ if (!defined($index) ||
+ !defined($level) ||
+ !defined($secname)) {
+ die "$0: ERROR: child process returned invalid data: $data\n";
+ }
+
+ $index = int($index);
+
+ if (!exists($results->{$index})) {
+ $results->{$index} = [];
+ }
+
+ push (@{$results->{$index}}, {
+ 'level' => $level,
+ 'secname' => $secname
+ });
+
+ return 1;
+}
+
+## finds initcalls from an object file or all object files in an archive, and
+## writes results back to the parent process
+sub find_initcalls {
+ my ($index, $file) = @_;
+
+ die "$0: ERROR: file $file doesn't exist?" if (! -f $file);
+
+ open(my $fh, "\"$nm\" --defined-only \"$file\" 2>/dev/null |")
+ or die "$0: ERROR: failed to execute \"$nm\": $!";
+
+ my $initcalls = {};
+
+ while (<$fh>) {
+ chomp;
+
+ # check for the start of a new object file (if processing an
+ # archive)
+ my ($path)= $_ =~ /^(.+)\:$/;
+
+ if (defined($path)) {
+ write_results($index, $initcalls);
+ $initcalls = {};
+ next;
+ }
+
+ # look for an initcall
+ my ($module, $counter, $line, $symbol) = $_ =~
+ /[a-z]\s+__initcall__(\S*)__(\d+)_(\d+)_(.*)$/;
+
+ if (!defined($module)) {
+ $module = ''
+ }
+
+ if (!defined($counter) ||
+ !defined($line) ||
+ !defined($symbol)) {
+ next;
+ }
+
+ # parse initcall level
+ my ($function, $level) = $symbol =~
+ /^(.*)((early|rootfs|con|[0-9])s?)$/;
+
+ die "$0: ERROR: invalid initcall name $symbol in $file($path)"
+ if (!defined($function) || !defined($level));
+
+ $initcalls->{$counter} = {
+ 'module' => $module,
+ 'line' => $line,
+ 'function' => $function,
+ 'level' => $level,
+ };
+ }
+
+ close($fh);
+ write_results($index, $initcalls);
+}
+
+## waits for any child process to complete, reads the results, and adds them to
+## the $results array for later processing
+sub wait_for_results {
+ my ($select) = @_;
+
+ my $pid = 0;
+ do {
+ # unblock children that may have a full write buffer
+ foreach my $fh ($select->can_read(0)) {
+ read_results($fh);
+ }
+
+ # check for children that have exited, read the remaining data
+ # from them, and clean up
+ $pid = waitpid(-1, WNOHANG);
+ if ($pid > 0) {
+ if (!exists($jobs->{$pid})) {
+ next;
+ }
+
+ my $fh = $jobs->{$pid};
+ $select->remove($fh);
+
+ while (read_results($fh)) {
+ # until eof
+ }
+
+ close($fh);
+ delete($jobs->{$pid});
+ }
+ } while ($pid > 0);
+}
+
+## forks a child to process each file passed in the command line and collects
+## the results
+sub process_files {
+ my $index = 0;
+ my $njobs = get_online_processors();
+ my $select = IO::Select->new();
+
+ while (my $file = shift(@ARGV)) {
+ # fork a child process and read it's stdout
+ my $pid = open(my $fh, '-|');
+
+ if (!defined($pid)) {
+ die "$0: ERROR: failed to fork: $!";
+ } elsif ($pid) {
+ # save the child process pid and the file handle
+ $select->add($fh);
+ $jobs->{$pid} = $fh;
+ } else {
+ # in the child process
+ STDOUT->autoflush(1);
+ find_initcalls($index, "$objtree/$file");
+ exit;
+ }
+
+ $index++;
+
+ # limit the number of children to $njobs
+ if (scalar(keys(%{$jobs})) >= $njobs) {
+ wait_for_results($select);
+ }
+ }
+
+ # wait for the remaining children to complete
+ while (scalar(keys(%{$jobs})) > 0) {
+ wait_for_results($select);
+ }
+}
+
+sub generate_initcall_lds() {
+ process_files();
+
+ my $sections = {}; # level -> [ secname, ...]
+
+ # sort results to retain link order and split to sections per
+ # initcall level
+ foreach my $index (sort { $a <=> $b } keys(%{$results})) {
+ foreach my $result (@{$results->{$index}}) {
+ my $level = $result->{'level'};
+
+ if (!exists($sections->{$level})) {
+ $sections->{$level} = [];
+ }
+
+ push(@{$sections->{$level}}, $result->{'secname'});
+ }
+ }
+
+ die "$0: ERROR: no initcalls?" if (!keys(%{$sections}));
+
+ # print out a linker script that defines the order of initcalls for
+ # each level
+ print "SECTIONS {\n";
+
+ foreach my $level (sort(keys(%{$sections}))) {
+ my $section;
+
+ if ($level eq 'con') {
+ $section = '.con_initcall.init';
+ } else {
+ $section = ".initcall${level}.init";
+ }
+
+ print "\t${section} : {\n";
+
+ foreach my $secname (@{$sections->{$level}}) {
+ print "\t\t*(${section}..${secname}) ;\n";
+ }
+
+ print "\t}\n";
+ }
+
+ print "}\n";
+}
+
+generate_initcall_lds();
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index c72f5d0238f1..42c73e24e820 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -39,6 +39,16 @@ info()
fi
}

+# Generate a linker script to ensure correct ordering of initcalls.
+gen_initcalls()
+{
+ info GEN .tmp_initcalls.lds
+
+ ${srctree}/scripts/generate_initcall_order.pl \
+ ${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS} \
+ > .tmp_initcalls.lds
+}
+
# If CONFIG_LTO_CLANG is selected, collect generated symbol versions into
# .tmp_symversions.lds
gen_symversions()
@@ -70,6 +80,9 @@ modpost_link()
--end-group"

if [ -n "${CONFIG_LTO_CLANG}" ]; then
+ gen_initcalls
+ lds="-T .tmp_initcalls.lds"
+
if [ -n "${CONFIG_MODVERSIONS}" ]; then
gen_symversions
lds="${lds} -T .tmp_symversions.lds"
@@ -283,6 +296,7 @@ cleanup()
{
rm -f .btf.*
rm -f .tmp_System.map
+ rm -f .tmp_initcalls.lds
rm -f .tmp_symversions.lds
rm -f .tmp_vmlinux*
rm -f System.map
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:17 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
With LTO, the compiler can rename static functions to avoid global
naming collisions. As initcall functions are typically static,
renaming can break references to them in inline assembly. This
change adds a global stub with a stable name for each initcall to
fix the issue when PREL32 relocations are used.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
include/linux/init.h | 30 ++++++++++++++++++++++++++----
1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/include/linux/init.h b/include/linux/init.h
index af638cd6dd52..5b4bdc5a8399 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -209,26 +209,48 @@ extern bool initcall_debug;
*/
#define __initcall_section(__sec, __iid) \
#__sec ".init.." #__iid
+
+/*
+ * With LTO, the compiler can rename static functions to avoid
+ * global naming collisions. We use a global stub function for
+ * initcalls to create a stable symbol name whose address can be
+ * taken in inline assembly when PREL32 relocations are used.
+ */
+#define __initcall_stub(fn, __iid, id) \
+ __initcall_name(initstub, __iid, id)
+
+#define __define_initcall_stub(__stub, fn) \
+ int __init __stub(void) \
+ { \
+ return fn(); \
+ } \
+ __ADDRESSABLE(__stub)
#else
#define __initcall_section(__sec, __iid) \
#__sec ".init"
+
+#define __initcall_stub(fn, __iid, id) fn
+
+#define __define_initcall_stub(__stub, fn) \
+ __ADDRESSABLE(fn)
#endif

#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-#define ____define_initcall(fn, __name, __sec) \
- __ADDRESSABLE(fn) \
+#define ____define_initcall(fn, __stub, __name, __sec) \
+ __define_initcall_stub(__stub, fn) \
asm(".section \"" __sec "\", \"a\" \n" \
__stringify(__name) ": \n" \
- ".long " #fn " - . \n" \
+ ".long " __stringify(__stub) " - . \n" \
".previous \n");
#else
-#define ____define_initcall(fn, __name, __sec) \
+#define ____define_initcall(fn, __unused, __name, __sec) \
static initcall_t __name __used \
__attribute__((__section__(__sec))) = fn;
#endif

#define __unique_initcall(fn, id, __sec, __iid) \
____define_initcall(fn, \
+ __initcall_stub(fn, __iid, id), \
__initcall_name(initcall, __iid, id), \
__initcall_section(__sec, __iid))

--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:19 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
With LTO, the compiler can rename static functions to avoid global
naming collisions. As PCI fixup functions are typically static,
renaming can break references to them in inline assembly. This
change adds a global stub to DECLARE_PCI_FIXUP_SECTION to fix the
issue when PREL32 relocations are used.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
include/linux/pci.h | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index c79d83304e52..1e65e16f165a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1909,19 +1909,24 @@ enum pci_fixup_pass {
};

#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-#define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
- class_shift, hook) \
- __ADDRESSABLE(hook) \
+#define ___DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
+ class_shift, hook, stub) \
+ void stub(struct pci_dev *dev) { hook(dev); } \
asm(".section " #sec ", \"a\" \n" \
".balign 16 \n" \
".short " #vendor ", " #device " \n" \
".long " #class ", " #class_shift " \n" \
- ".long " #hook " - . \n" \
+ ".long " #stub " - . \n" \
".previous \n");
+
+#define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
+ class_shift, hook, stub) \
+ ___DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
+ class_shift, hook, stub)
#define DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
class_shift, hook) \
__DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
- class_shift, hook)
+ class_shift, hook, __UNIQUE_ID(hook))
#else
/* Anonymous variables would be nice... */
#define DECLARE_PCI_FIXUP_SECTION(section, name, vendor, device, class, \
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:21 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen, Bill Wendling
With LTO, everything is compiled into LLVM bitcode, so we have to link
each module into native code before modpost. Kbuild uses the .lto.o
suffix for these files, which also ends up in module information. This
change strips the unnecessary .lto suffix from the module name.

Suggested-by: Bill Wendling <mo...@google.com>
Signed-off-by: Sami Tolvanen <samito...@google.com>
---
scripts/mod/modpost.c | 16 +++++++---------
scripts/mod/modpost.h | 9 +++++++++
scripts/mod/sumversion.c | 6 +++++-
3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 6aea65c65745..8352f8a1a138 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -17,7 +17,6 @@
#include <ctype.h>
#include <string.h>
#include <limits.h>
-#include <stdbool.h>
#include <errno.h>
#include "modpost.h"
#include "../../include/linux/license.h"
@@ -80,14 +79,6 @@ modpost_log(enum loglevel loglevel, const char *fmt, ...)
exit(1);
}

-static inline bool strends(const char *str, const char *postfix)
-{
- if (strlen(str) < strlen(postfix))
- return false;
-
- return strcmp(str + strlen(str) - strlen(postfix), postfix) == 0;
-}
-
void *do_nofail(void *ptr, const char *expr)
{
if (!ptr)
@@ -1975,6 +1966,10 @@ static char *remove_dot(char *s)
size_t m = strspn(s + n + 1, "0123456789");
if (m && (s[n + m] == '.' || s[n + m] == 0))
s[n] = 0;
+
+ /* strip trailing .lto */
+ if (strends(s, ".lto"))
+ s[strlen(s) - 4] = '\0';
}
return s;
}
@@ -1998,6 +1993,9 @@ static void read_symbols(const char *modname)
/* strip trailing .o */
tmp = NOFAIL(strdup(modname));
tmp[strlen(tmp) - 2] = '\0';
+ /* strip trailing .lto */
+ if (strends(tmp, ".lto"))
+ tmp[strlen(tmp) - 4] = '\0';
mod = new_module(tmp);
free(tmp);
}
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 3aa052722233..fab30d201f9e 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -2,6 +2,7 @@
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
+#include <stdbool.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
@@ -180,6 +181,14 @@ static inline unsigned int get_secindex(const struct elf_info *info,
return info->symtab_shndx_start[sym - info->symtab_start];
}

+static inline bool strends(const char *str, const char *postfix)
+{
+ if (strlen(str) < strlen(postfix))
+ return false;
+
+ return strcmp(str + strlen(str) - strlen(postfix), postfix) == 0;
+}
+
/* file2alias.c */
extern unsigned int cross_build;
void handle_moddevtable(struct module *mod, struct elf_info *info,
diff --git a/scripts/mod/sumversion.c b/scripts/mod/sumversion.c
index d587f40f1117..760e6baa7eda 100644
--- a/scripts/mod/sumversion.c
+++ b/scripts/mod/sumversion.c
@@ -391,10 +391,14 @@ void get_src_version(const char *modname, char sum[], unsigned sumlen)
struct md4_ctx md;
char *fname;
char filelist[PATH_MAX + 1];
+ int postfix_len = 1;
+
+ if (strends(modname, ".lto.o"))
+ postfix_len = 5;

/* objects for a module are listed in the first line of *.mod file. */
snprintf(filelist, sizeof(filelist), "%.*smod",
- (int)strlen(modname) - 1, modname);
+ (int)strlen(modname) - postfix_len, modname);

buf = read_text_file(filelist);

--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:22 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
With CONFIG_LTO_CLANG, clang generates LLVM IR instead of ELF object
files. As empty.o is used for probing target properties, disable LTO
for it to produce an object file instead.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
scripts/mod/Makefile | 1 +
1 file changed, 1 insertion(+)

diff --git a/scripts/mod/Makefile b/scripts/mod/Makefile
index 296b6a3878b2..b6e3b40c6eeb 100644
--- a/scripts/mod/Makefile
+++ b/scripts/mod/Makefile
@@ -1,5 +1,6 @@
# SPDX-License-Identifier: GPL-2.0
OBJECT_FILES_NON_STANDARD := y
+CFLAGS_REMOVE_empty.o += $(CC_FLAGS_LTO)

hostprogs := modpost mk_elfconfig
always-y := $(hostprogs) empty.o
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:24 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
With CONFIG_LTO_CLANG, we produce LLVM bitcode instead of ELF object
files. Since LTO is not really needed here and the Makefile assumes we
produce an object file, disable LTO for libstub.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
drivers/firmware/efi/libstub/Makefile | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 75daaf20374e..95e12002cc7c 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -35,6 +35,8 @@ KBUILD_CFLAGS := $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \

# remove SCS flags from all objects in this directory
KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
+# disable LTO
+KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))

GCOV_PROFILE := n
# Sanitizer runtimes are unavailable and cannot be linked here.
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:26 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
Disable LTO for rodata.o to allow objcopy to be used to
manipulate sections.

Signed-off-by: Sami Tolvanen <samito...@google.com>
Acked-by: Kees Cook <kees...@chromium.org>
---
drivers/misc/lkdtm/Makefile | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/misc/lkdtm/Makefile b/drivers/misc/lkdtm/Makefile
index c70b3822013f..dd4c936d4d73 100644
--- a/drivers/misc/lkdtm/Makefile
+++ b/drivers/misc/lkdtm/Makefile
@@ -13,6 +13,7 @@ lkdtm-$(CONFIG_LKDTM) += cfi.o

KASAN_SANITIZE_stackleak.o := n
KCOV_INSTRUMENT_rodata.o := n
+CFLAGS_REMOVE_rodata.o += $(CC_FLAGS_LTO)

OBJCOPYFLAGS :=
OBJCOPYFLAGS_rodata_objcopy.o := \
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:28 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
Since arm64 does not use -pg in CC_FLAGS_FTRACE with
DYNAMIC_FTRACE_WITH_REGS, skip running recordmcount by
exporting CC_USING_PATCHABLE_FUNCTION_ENTRY.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
arch/arm64/Makefile | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index a0d94d063fa8..fc6c20a10291 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -115,6 +115,7 @@ endif
ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_REGS),y)
KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
CC_FLAGS_FTRACE := -fpatchable-function-entry=2
+ export CC_USING_PATCHABLE_FUNCTION_ENTRY := 1
endif

# Default value
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:29 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
Filter out CC_FLAGS_LTO for the vDSO.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
arch/arm64/kernel/vdso/Makefile | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index 556d424c6f52..cfad4c296ca1 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -29,8 +29,8 @@ ldflags-y := -shared -nostdlib -soname=linux-vdso.so.1 --hash-style=sysv \
ccflags-y := -fno-common -fno-builtin -fno-stack-protector -ffixed-x18
ccflags-y += -DDISABLE_BRANCH_PROFILING

-CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS)
-KBUILD_CFLAGS += $(DISABLE_LTO)
+CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) \
+ $(CC_FLAGS_LTO)
KASAN_SANITIZE := n
UBSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD := y
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:32 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
Allow CONFIG_LTO_CLANG and CONFIG_THINLTO to be enabled.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
arch/arm64/Kconfig | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index a4a094bedcb2..e1961653964d 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -72,6 +72,8 @@ config ARM64
select ARCH_USE_SYM_ANNOTATIONS
select ARCH_SUPPORTS_MEMORY_FAILURE
select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK
+ select ARCH_SUPPORTS_LTO_CLANG
+ select ARCH_SUPPORTS_THINLTO
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && (GCC_VERSION >= 50000 || CC_IS_CLANG)
select ARCH_SUPPORTS_NUMA_BALANCING
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:33 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
Remove the undefined DISABLE_LTO flag from the vDSO, and filter out
CC_FLAGS_LTO flags instead where needed.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
arch/x86/entry/vdso/Makefile | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 04e65f0698f6..67f60662830a 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -9,8 +9,6 @@ ARCH_REL_TYPE_ABS := R_X86_64_JUMP_SLOT|R_X86_64_GLOB_DAT|R_X86_64_RELATIVE|
ARCH_REL_TYPE_ABS += R_386_GLOB_DAT|R_386_JMP_SLOT|R_386_RELATIVE
include $(srctree)/lib/vdso/Makefile

-KBUILD_CFLAGS += $(DISABLE_LTO)
-
# Sanitizer runtimes are unavailable and cannot be linked here.
KASAN_SANITIZE := n
UBSAN_SANITIZE := n
@@ -92,7 +90,7 @@ ifneq ($(RETPOLINE_VDSO_CFLAGS),)
endif
endif

-$(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
+$(vobjs): KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)

#
# vDSO code runs in userspace and -pg doesn't help with profiling anyway.
@@ -150,6 +148,7 @@ KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS_32))
+KBUILD_CFLAGS_32 := $(filter-out $(CC_FLAGS_LTO),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic
KBUILD_CFLAGS_32 += $(call cc-option, -fno-stack-protector)
KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:35 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
Ignore mcount relocations in ftrace_make_nop.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
arch/x86/kernel/ftrace.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 51504566b3a6..c3b28b81277b 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -121,6 +121,7 @@ ftrace_modify_code_direct(unsigned long ip, const char *old_code,
return 0;
}

+__nomcount
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long ip = rec->ip;
--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:37 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
L4_PAGE_OFFSET is a constant value, so don't warn about absolute
relocations.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
arch/x86/tools/relocs.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index ce7188cbdae5..8f3bf34840ce 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -47,6 +47,7 @@ static const char * const sym_regex_kernel[S_NSYMTYPES] = {
[S_ABS] =
"^(xen_irq_disable_direct_reloc$|"
"xen_save_fl_direct_reloc$|"
+ "L4_PAGE_OFFSET|"
"VDSO|"
"__crc_)",

--
2.27.0.212.ge8ba1cc988-goog

Sami Tolvanen

unread,
Jun 24, 2020, 4:33:38 PM6/24/20
to Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, Sami Tolvanen
Allow CONFIG_LTO_CLANG and CONFIG_THINLTO to be enabled.

Signed-off-by: Sami Tolvanen <samito...@google.com>
---
arch/x86/Kconfig | 2 ++
arch/x86/Makefile | 5 +++++
2 files changed, 7 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6a0cc524882d..df335b1f9c31 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -92,6 +92,8 @@ config X86
select ARCH_SUPPORTS_ACPI
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
+ select ARCH_SUPPORTS_LTO_CLANG if X86_64
+ select ARCH_SUPPORTS_THINLTO if X86_64
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_QUEUED_RWLOCKS
select ARCH_USE_QUEUED_SPINLOCKS
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 00e378de8bc0..a1abc1e081ad 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -188,6 +188,11 @@ ifdef CONFIG_X86_64
KBUILD_LDFLAGS += $(call ld-option, -z max-page-size=0x200000)
endif

+ifdef CONFIG_LTO_CLANG
+KBUILD_LDFLAGS += -plugin-opt=-code-model=kernel \
+ -plugin-opt=-stack-alignment=$(if $(CONFIG_X86_32),4,8)
+endif
+
# Workaround for a gcc prelease that unfortunately was shipped in a suse release
KBUILD_CFLAGS += -Wno-sign-compare
#
--
2.27.0.212.ge8ba1cc988-goog

Nick Desaulniers

unread,
Jun 24, 2020, 4:54:06 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
The kconfig change gates this on clang-11; do we still need the
cc-option check here, or can we hardcode the use of -fsplit-lto-unit?
Playing with the flag in godbolt, it looks like clang-8 had support
for this flag.

> +KBUILD_LDFLAGS += --thinlto-cache-dir=.thinlto-cache

It might be nice to have `make distclean` or even `make clean` scrub
the .thinlto-cache? Also, I verified that the `.gitignore` rule for
`.*` properly ignores this dir.
--
Thanks,
~Nick Desaulniers

Nick Desaulniers

unread,
Jun 24, 2020, 4:57:25 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samito...@google.com> wrote:
>
> With CONFIG_LTO_CLANG, clang generates LLVM IR instead of ELF object
> files. As empty.o is used for probing target properties, disable LTO
> for it to produce an object file instead.
>
> Signed-off-by: Sami Tolvanen <samito...@google.com>

Reviewed-by: Nick Desaulniers <ndesau...@google.com>

> ---
> scripts/mod/Makefile | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/scripts/mod/Makefile b/scripts/mod/Makefile
> index 296b6a3878b2..b6e3b40c6eeb 100644
> --- a/scripts/mod/Makefile
> +++ b/scripts/mod/Makefile
> @@ -1,5 +1,6 @@
> # SPDX-License-Identifier: GPL-2.0
> OBJECT_FILES_NON_STANDARD := y
> +CFLAGS_REMOVE_empty.o += $(CC_FLAGS_LTO)
>
> hostprogs := modpost mk_elfconfig
> always-y := $(hostprogs) empty.o
> --
> 2.27.0.212.ge8ba1cc988-goog
>


--
Thanks,
~Nick Desaulniers

Nick Desaulniers

unread,
Jun 24, 2020, 4:59:11 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samito...@google.com> wrote:
>
> Filter out CC_FLAGS_LTO for the vDSO.

Just curious about this patch (and the following one for x86's vdso),
do you happen to recall specifically what the issues with the vdso's
are?
--
Thanks,
~Nick Desaulniers

Nick Desaulniers

unread,
Jun 24, 2020, 5:02:12 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samito...@google.com> wrote:
>
> LLD always splits sections with LTO, which increases module sizes. This
> change adds a linker script that merges the split sections in the final
> module and discards the .eh_frame section that LLD may generate.

For discarding .eh_frame, Kees is currently fighting with a series
that I would really like to see land that enables warnings on orphan
section placement. I don't see any new flags to inhibit .eh_frame
generation, or discard it in the linker script, so I'd expect it to be
treated as an orphan section and kept. Was that missed, or should
that be removed from the commit message?
--
Thanks,
~Nick Desaulniers

Nick Desaulniers

unread,
Jun 24, 2020, 5:09:54 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT), Andi Kleen
On Wed, Jun 24, 2020 at 1:58 PM Nick Desaulniers
<ndesau...@google.com> wrote:
>
> On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samito...@google.com> wrote:
> >
> > Filter out CC_FLAGS_LTO for the vDSO.
>
> Just curious about this patch (and the following one for x86's vdso),
> do you happen to recall specifically what the issues with the vdso's
> are?

+ Andi (tangential, I actually have a bunch of tabs open with slides
from http://halobates.de/ right now)
58edae3aac9f2
67424d5a22124
$ git log -S DISABLE_LTO

>
> >
> > Signed-off-by: Sami Tolvanen <samito...@google.com>
> > ---
> > arch/arm64/kernel/vdso/Makefile | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
> > index 556d424c6f52..cfad4c296ca1 100644
> > --- a/arch/arm64/kernel/vdso/Makefile
> > +++ b/arch/arm64/kernel/vdso/Makefile
> > @@ -29,8 +29,8 @@ ldflags-y := -shared -nostdlib -soname=linux-vdso.so.1 --hash-style=sysv \
> > ccflags-y := -fno-common -fno-builtin -fno-stack-protector -ffixed-x18
> > ccflags-y += -DDISABLE_BRANCH_PROFILING
> >
> > -CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS)
> > -KBUILD_CFLAGS += $(DISABLE_LTO)
> > +CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) \
> > + $(CC_FLAGS_LTO)
> > KASAN_SANITIZE := n
> > UBSAN_SANITIZE := n
> > OBJECT_FILES_NON_STANDARD := y
> > --

--
Thanks,
~Nick Desaulniers

Nick Desaulniers

unread,
Jun 24, 2020, 5:13:59 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samito...@google.com> wrote:
>
> With LTO, llvm-nm prints out symbols for each archive member
> separately, which results in a lot of duplicate dependencies in the
> .mod file when CONFIG_TRIM_UNUSED_SYMS is enabled. When a module
> consists of several compilation units, the output can exceed the
> default xargs command size limit and split the dependency list to
> multiple lines, which results in used symbols getting trimmed.
>
> This change removes duplicate dependencies, which will reduce the
> probability of this happening and makes .mod files smaller and
> easier to read.
>
> Signed-off-by: Sami Tolvanen <samito...@google.com>

Reviewed-by: Nick Desaulniers <ndesau...@google.com>

> ---
> scripts/Makefile.build | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 82977350f5a6..82b465ce3ca0 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -291,7 +291,7 @@ endef
>
> # List module undefined symbols (or empty line if not enabled)
> ifdef CONFIG_TRIM_UNUSED_KSYMS
> -cmd_undef_syms = $(NM) $< | sed -n 's/^ *U //p' | xargs echo
> +cmd_undef_syms = $(NM) $< | sed -n 's/^ *U //p' | sort -u | xargs echo
> else
> cmd_undef_syms = echo
> endif
> --
> 2.27.0.212.ge8ba1cc988-goog
>


--
Thanks,
~Nick Desaulniers

Peter Zijlstra

unread,
Jun 24, 2020, 5:15:46 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org
On Wed, Jun 24, 2020 at 01:31:38PM -0700, Sami Tolvanen wrote:
> This patch series adds support for building x86_64 and arm64 kernels
> with Clang's Link Time Optimization (LTO).
>
> In addition to performance, the primary motivation for LTO is to allow
> Clang's Control-Flow Integrity (CFI) to be used in the kernel. Google's
> Pixel devices have shipped with LTO+CFI kernels since 2018.
>
> Most of the patches are build system changes for handling LLVM bitcode,
> which Clang produces with LTO instead of ELF object files, postponing
> ELF processing until a later stage, and ensuring initcall ordering.
>
> Note that first objtool patch in the series is already in linux-next,
> but as it's needed with LTO, I'm including it also here to make testing
> easier.

I'm very sad that yet again, memory ordering isn't addressed. LTO vastly
increases the range of the optimizer to wreck things.

Peter Zijlstra

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Jun 24, 2020, 5:19:18 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org
On Wed, Jun 24, 2020 at 01:31:43PM -0700, Sami Tolvanen wrote:
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 30827f82ad62..12b115152532 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -120,7 +120,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
> /* Annotate a C jump table to allow objtool to follow the code flow */
> #define __annotate_jump_table __section(.rodata..c_jump_table)
>
> -#ifdef CONFIG_DEBUG_ENTRY
> +#if defined(CONFIG_DEBUG_ENTRY) || defined(CONFIG_LTO_CLANG)
> /* Begin/end of an instrumentation safe region */
> #define instrumentation_begin() ({ \
> asm volatile("%c0:\n\t" \

Why would you be doing noinstr validation for lto builds? That doesn't
make sense.

> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 9ad9210d70a1..9fdba71c135a 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -399,7 +399,7 @@ config STACK_VALIDATION
>
> config VMLINUX_VALIDATION
> bool
> - depends on STACK_VALIDATION && DEBUG_ENTRY && !PARAVIRT
> + depends on STACK_VALIDATION && (DEBUG_ENTRY || LTO_CLANG) && !PARAVIRT
> default y
>

For that very same reason you shouldn't be excluding paravirt either.

> diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> index d168f0cfe67c..9f1df2f1fab5 100644
> --- a/scripts/Makefile.modfinal
> +++ b/scripts/Makefile.modfinal
> @@ -48,6 +48,21 @@ endif # CC_USING_PATCHABLE_FUNCTION_ENTRY
> endif # CC_USING_RECORD_MCOUNT
> endif # CONFIG_FTRACE_MCOUNT_RECORD
>
> +ifdef CONFIG_STACK_VALIDATION
> +ifneq ($(SKIP_STACK_VALIDATION),1)
> +cmd_ld_ko_o += \
> + $(objtree)/tools/objtool/objtool \
> + $(if $(CONFIG_UNWINDER_ORC),orc generate,check) \
> + --module \
> + $(if $(CONFIG_FRAME_POINTER),,--no-fp) \
> + $(if $(CONFIG_GCOV_KERNEL),--no-unreachable,) \
> + $(if $(CONFIG_RETPOLINE),--retpoline,) \
> + $(if $(CONFIG_X86_SMAP),--uaccess,) \
> + $(@:.ko=$(prelink-ext).o);
> +
> +endif # SKIP_STACK_VALIDATION
> +endif # CONFIG_STACK_VALIDATION

What about the objtool invocation from link-vmlinux.sh ?

Peter Zijlstra

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Jun 24, 2020, 5:20:59 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, George Burgess IV
On Wed, Jun 24, 2020 at 01:31:44PM -0700, Sami Tolvanen wrote:
> This change limits function inlining across translation unit
> boundaries in order to reduce the binary size with LTO.
>
> The -import-instr-limit flag defines a size limit, as the number
> of LLVM IR instructions, for importing functions from other TUs.
> The default value is 100, and decreasing it to 5 reduces the size
> of a stripped arm64 defconfig vmlinux by 11%.

Is that also the right number for x86? What about the effect on
performance? What did 6 do? or 4?

Peter Zijlstra

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Jun 24, 2020, 5:27:40 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org
On Wed, Jun 24, 2020 at 01:31:42PM -0700, Sami Tolvanen wrote:
> With LTO, LLVM bitcode won't be compiled into native code until
> modpost_link. This change postpones calls to recordmcount until after
> this step.
>
> In order to exclude specific functions from inspection, we add a new
> code section .text..nomcount, which we tell recordmcount to ignore, and
> a __nomcount attribute for moving functions to this section.

I'm confused, you only add this to functions in ftrace itself, which is
compiled with:

KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS))

and so should not have mcount/fentry sites anyway. So what's the point
of ignoring them further?

This Changelog does not explain.

Sami Tolvanen

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Jun 24, 2020, 5:29:10 PM6/24/20
to Nick Desaulniers, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
On Wed, Jun 24, 2020 at 01:53:52PM -0700, Nick Desaulniers wrote:
> On Wed, Jun 24, 2020 at 1:32 PM Sami Tolvanen <samito...@google.com> wrote:
> >
> > diff --git a/Makefile b/Makefile
> > index ac2c61c37a73..0c7fe6fb2143 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -886,6 +886,22 @@ KBUILD_CFLAGS += $(CC_FLAGS_SCS)
> > export CC_FLAGS_SCS
> > endif
> >
> > +ifdef CONFIG_LTO_CLANG
> > +ifdef CONFIG_THINLTO
> > +CC_FLAGS_LTO_CLANG := -flto=thin $(call cc-option, -fsplit-lto-unit)
>
> The kconfig change gates this on clang-11; do we still need the
> cc-option check here, or can we hardcode the use of -fsplit-lto-unit?
> Playing with the flag in godbolt, it looks like clang-8 had support
> for this flag.

True, we don't need cc-option here anymore. I'll remove it, thanks.

> > +KBUILD_LDFLAGS += --thinlto-cache-dir=.thinlto-cache
>
> It might be nice to have `make distclean` or even `make clean` scrub
> the .thinlto-cache? Also, I verified that the `.gitignore` rule for
> `.*` properly ignores this dir.

Sure, distclean sounds appropriate to me.

Sami

Sami Tolvanen

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Jun 24, 2020, 5:30:23 PM6/24/20
to Peter Zijlstra, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org
I believe Will has some thoughts about this, and patches, but I'll let
him talk about it.

Sami

Sami Tolvanen

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Jun 24, 2020, 5:31:36 PM6/24/20
to Nick Desaulniers, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
On Wed, Jun 24, 2020 at 02:01:59PM -0700, 'Nick Desaulniers' via Clang Built Linux wrote:
> On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samito...@google.com> wrote:
> >
> > LLD always splits sections with LTO, which increases module sizes. This
> > change adds a linker script that merges the split sections in the final
> > module and discards the .eh_frame section that LLD may generate.
>
> For discarding .eh_frame, Kees is currently fighting with a series
> that I would really like to see land that enables warnings on orphan
> section placement. I don't see any new flags to inhibit .eh_frame
> generation, or discard it in the linker script, so I'd expect it to be
> treated as an orphan section and kept. Was that missed, or should
> that be removed from the commit message?

It should be removed from the commit message, thanks for pointing it
out.

Sami

Nick Desaulniers

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Jun 24, 2020, 5:31:49 PM6/24/20
to Peter Zijlstra, Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
Hi Peter, could you expand on the issue for the folks on the thread?
I'm happy to try to hack something up in LLVM if we check that X does
or does not happen; maybe we can even come up with some concrete test
cases that can be added to LLVM's codebase?

--
Thanks,
~Nick Desaulniers

Sami Tolvanen

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Jun 24, 2020, 5:45:38 PM6/24/20
to Peter Zijlstra, Steven Rostedt, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org
Normally, recordmcount ignores each ftrace.o file, but since we are
running it on vmlinux.o, we need another way to stop it from looking
at references to mcount/fentry that are not calls. Here's a comment
from recordmcount.c:

/*
* The file kernel/trace/ftrace.o references the mcount
* function but does not call it. Since ftrace.o should
* not be traced anyway, we just skip it.
*/

But I agree, the commit message could use more defails. Also +Steven
for thoughts about this approach.

Sami

Sami Tolvanen

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Jun 24, 2020, 5:49:33 PM6/24/20
to Peter Zijlstra, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org
On Wed, Jun 24, 2020 at 11:19:08PM +0200, Peter Zijlstra wrote:
> On Wed, Jun 24, 2020 at 01:31:43PM -0700, Sami Tolvanen wrote:
> > diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> > index 30827f82ad62..12b115152532 100644
> > --- a/include/linux/compiler.h
> > +++ b/include/linux/compiler.h
> > @@ -120,7 +120,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
> > /* Annotate a C jump table to allow objtool to follow the code flow */
> > #define __annotate_jump_table __section(.rodata..c_jump_table)
> >
> > -#ifdef CONFIG_DEBUG_ENTRY
> > +#if defined(CONFIG_DEBUG_ENTRY) || defined(CONFIG_LTO_CLANG)
> > /* Begin/end of an instrumentation safe region */
> > #define instrumentation_begin() ({ \
> > asm volatile("%c0:\n\t" \
>
> Why would you be doing noinstr validation for lto builds? That doesn't
> make sense.

This is just to avoid a ton of noinstr warnings when we run objtool on
vmlinux.o, but I'm also fine with skipping noinstr validation with LTO.

> > +ifdef CONFIG_STACK_VALIDATION
> > +ifneq ($(SKIP_STACK_VALIDATION),1)
> > +cmd_ld_ko_o += \
> > + $(objtree)/tools/objtool/objtool \
> > + $(if $(CONFIG_UNWINDER_ORC),orc generate,check) \
> > + --module \
> > + $(if $(CONFIG_FRAME_POINTER),,--no-fp) \
> > + $(if $(CONFIG_GCOV_KERNEL),--no-unreachable,) \
> > + $(if $(CONFIG_RETPOLINE),--retpoline,) \
> > + $(if $(CONFIG_X86_SMAP),--uaccess,) \
> > + $(@:.ko=$(prelink-ext).o);
> > +
> > +endif # SKIP_STACK_VALIDATION
> > +endif # CONFIG_STACK_VALIDATION
>
> What about the objtool invocation from link-vmlinux.sh ?

What about it? The existing objtool_link invocation in link-vmlinux.sh
works fine for our purposes as well.

Sami

Sami Tolvanen

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Jun 24, 2020, 5:52:37 PM6/24/20
to Nick Desaulniers, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
On Wed, Jun 24, 2020 at 01:58:57PM -0700, 'Nick Desaulniers' via Clang Built Linux wrote:
> On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samito...@google.com> wrote:
> >
> > Filter out CC_FLAGS_LTO for the vDSO.
>
> Just curious about this patch (and the following one for x86's vdso),
> do you happen to recall specifically what the issues with the vdso's
> are?

I recall the compiler optimizing away functions at some point, but as
LTO is not really needed in the vDSO, it's just easiest to disable it
there.

Sami

Nick Desaulniers

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Jun 24, 2020, 6:05:39 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT), Bill Wendling
On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samito...@google.com> wrote:
>
> With LTO, everything is compiled into LLVM bitcode, so we have to link
> each module into native code before modpost. Kbuild uses the .lto.o
> suffix for these files, which also ends up in module information. This
> change strips the unnecessary .lto suffix from the module name.
>
> Suggested-by: Bill Wendling <mo...@google.com>
> Signed-off-by: Sami Tolvanen <samito...@google.com>
> ---
> scripts/mod/modpost.c | 16 +++++++---------
> scripts/mod/modpost.h | 9 +++++++++
> scripts/mod/sumversion.c | 6 +++++-
> 3 files changed, 21 insertions(+), 10 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 6aea65c65745..8352f8a1a138 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -17,7 +17,6 @@
> #include <ctype.h>
> #include <string.h>
> #include <limits.h>
> -#include <stdbool.h>

It looks like `bool` is used in the function signatures of other
functions in this TU, I'm not the biggest fan of hoisting the includes
out of the .c source into the header (I'd keep it in both), but I
don't feel strongly enough to NACK.

Reviewed-by: Nick Desaulniers <ndesau...@google.com>

> #include <errno.h>
> #include "modpost.h"
> #include "../../include/linux/license.h"
> @@ -80,14 +79,6 @@ modpost_log(enum loglevel loglevel, const char *fmt, ...)
> exit(1);
> }
>
> -static inline bool strends(const char *str, const char *postfix)
> -{
> - if (strlen(str) < strlen(postfix))
> - return false;
> -
> - return strcmp(str + strlen(str) - strlen(postfix), postfix) == 0;
> -}
> -
> void *do_nofail(void *ptr, const char *expr)
> {
> if (!ptr)
> @@ -1975,6 +1966,10 @@ static char *remove_dot(char *s)
> size_t m = strspn(s + n + 1, "0123456789");
> if (m && (s[n + m] == '.' || s[n + m] == 0))
> s[n] = 0;
> +
> + /* strip trailing .lto */
> + if (strends(s, ".lto"))
> + s[strlen(s) - 4] = '\0';
> }
> return s;
> }
> @@ -1998,6 +1993,9 @@ static void read_symbols(const char *modname)
> /* strip trailing .o */
> tmp = NOFAIL(strdup(modname));
> tmp[strlen(tmp) - 2] = '\0';
> + /* strip trailing .lto */
> + if (strends(tmp, ".lto"))
> + tmp[strlen(tmp) - 4] = '\0';
> mod = new_module(tmp);
> free(tmp);
> }
> diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
> index 3aa052722233..fab30d201f9e 100644
> --- a/scripts/mod/modpost.h
> +++ b/scripts/mod/modpost.h
> @@ -2,6 +2,7 @@
> #include <stdio.h>
> #include <stdlib.h>
> #include <stdarg.h>
> +#include <stdbool.h>
> #include <string.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> @@ -180,6 +181,14 @@ static inline unsigned int get_secindex(const struct elf_info *info,
> return info->symtab_shndx_start[sym - info->symtab_start];
> }
>
> +static inline bool strends(const char *str, const char *postfix)
> +{
> + if (strlen(str) < strlen(postfix))
> + return false;
> +
> + return strcmp(str + strlen(str) - strlen(postfix), postfix) == 0;
> +}
> +
> /* file2alias.c */
> extern unsigned int cross_build;
> void handle_moddevtable(struct module *mod, struct elf_info *info,
> diff --git a/scripts/mod/sumversion.c b/scripts/mod/sumversion.c
> index d587f40f1117..760e6baa7eda 100644
> --- a/scripts/mod/sumversion.c
> +++ b/scripts/mod/sumversion.c
> @@ -391,10 +391,14 @@ void get_src_version(const char *modname, char sum[], unsigned sumlen)
> struct md4_ctx md;
> char *fname;
> char filelist[PATH_MAX + 1];
> + int postfix_len = 1;
> +
> + if (strends(modname, ".lto.o"))
> + postfix_len = 5;
>
> /* objects for a module are listed in the first line of *.mod file. */
> snprintf(filelist, sizeof(filelist), "%.*smod",
> - (int)strlen(modname) - 1, modname);
> + (int)strlen(modname) - postfix_len, modname);
>
> buf = read_text_file(filelist);

kernel test robot

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Jun 24, 2020, 6:50:45 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, kbuil...@lists.01.org, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org
Hi Sami,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on 26e122e97a3d0390ebec389347f64f3730fdf48f]

url: https://github.com/0day-ci/linux/commits/Sami-Tolvanen/add-support-for-Clang-LTO/20200625-043816
base: 26e122e97a3d0390ebec389347f64f3730fdf48f
config: i386-alldefconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-13) 9.3.0
reproduce (this is a W=1 build):
# save the attached .config to linux build tree
make W=1 ARCH=i386

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <l...@intel.com>

All warnings (new ones prefixed by >>):

In file included from arch/x86/kernel/pci-dma.c:9:
>> include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_via_no_dac190' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
>> include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
>> include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
>> include/linux/pci.h:1949:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1949 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_final, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
>> arch/x86/kernel/pci-dma.c:154:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_CLASS_FINAL'
154 | DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--
In file included from arch/x86/kernel/quirks.c:6:
>> include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_ich_force_enable_hpet180' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
>> include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
>> include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1976:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1976 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_header, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
>> arch/x86/kernel/quirks.c:156:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_HEADER'
156 | DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ESB2_0,
| ^~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_ich_force_enable_hpet181' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
>> include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
>> include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1976:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1976 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_header, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/kernel/quirks.c:158:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_HEADER'
158 | DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ICH6_0,
| ^~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_ich_force_enable_hpet182' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
>> include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
>> include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1976:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1976 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_header, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/kernel/quirks.c:160:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_HEADER'
160 | DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ICH6_1,
| ^~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_ich_force_enable_hpet183' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1976:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1976 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_header, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/kernel/quirks.c:162:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_HEADER'
162 | DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ICH7_0,
| ^~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_ich_force_enable_hpet184' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1976:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1976 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_header, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/kernel/quirks.c:164:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_HEADER'
164 | DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ICH7_1,
| ^~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_ich_force_enable_hpet185' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1976:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1976 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_header, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/kernel/quirks.c:166:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_HEADER'
166 | DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ICH7_31,
| ^~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_ich_force_enable_hpet186' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
--
In file included from drivers/pci/vpd.c:8:
>> include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_quirk_f0_vpd_link180' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
>> include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
>> include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1941:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1941 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_early, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
>> drivers/pci/vpd.c:543:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_CLASS_EARLY'
543 | DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_INTEL, PCI_ANY_ID,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_quirk_blacklist_vpd181' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
>> include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
>> include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1979:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1979 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_final, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
>> drivers/pci/vpd.c:560:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_FINAL'
560 | DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LSI_LOGIC, 0x0060, quirk_blacklist_vpd);
| ^~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_quirk_blacklist_vpd182' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
>> include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
>> include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
>> include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1979:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1979 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_final, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/pci/vpd.c:561:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_FINAL'
561 | DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LSI_LOGIC, 0x007c, quirk_blacklist_vpd);
| ^~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_quirk_blacklist_vpd183' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1979:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1979 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_final, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/pci/vpd.c:562:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_FINAL'
562 | DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LSI_LOGIC, 0x0413, quirk_blacklist_vpd);
| ^~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_quirk_blacklist_vpd184' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1979:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1979 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_final, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/pci/vpd.c:563:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_FINAL'
563 | DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LSI_LOGIC, 0x0078, quirk_blacklist_vpd);
| ^~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_quirk_blacklist_vpd185' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~~~~~~
include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
1914 | void stub(struct pci_dev *dev) { hook(dev); } \
| ^~~~
include/linux/pci.h:1928:2: note: in expansion of macro '__DECLARE_PCI_FIXUP_SECTION'
1928 | __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:29: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/compiler-gcc.h:72:37: note: in expansion of macro '__PASTE'
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
| ^~~~~~~
include/linux/pci.h:1929:26: note: in expansion of macro '__UNIQUE_ID'
1929 | class_shift, hook, __UNIQUE_ID(hook))
| ^~~~~~~~~~~
include/linux/pci.h:1979:2: note: in expansion of macro 'DECLARE_PCI_FIXUP_SECTION'
1979 | DECLARE_PCI_FIXUP_SECTION(.pci_fixup_final, \
| ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/pci/vpd.c:564:1: note: in expansion of macro 'DECLARE_PCI_FIXUP_FINAL'
564 | DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LSI_LOGIC, 0x0079, quirk_blacklist_vpd);
| ^~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_quirk_blacklist_vpd186' [-Wmissing-prototypes]
72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
..

vim +/__DECLARE_PCI_FIXUP_SECTION +1928 include/linux/pci.h

^1da177e4c3f415 Linus Torvalds 2005-04-16 1910
c9d8b55fa019162 Ard Biesheuvel 2018-08-21 1911 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
b1b820bb0420d08 Sami Tolvanen 2020-06-24 1912 #define ___DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
b1b820bb0420d08 Sami Tolvanen 2020-06-24 1913 class_shift, hook, stub) \
b1b820bb0420d08 Sami Tolvanen 2020-06-24 @1914 void stub(struct pci_dev *dev) { hook(dev); } \
c9d8b55fa019162 Ard Biesheuvel 2018-08-21 1915 asm(".section " #sec ", \"a\" \n" \
c9d8b55fa019162 Ard Biesheuvel 2018-08-21 1916 ".balign 16 \n" \
c9d8b55fa019162 Ard Biesheuvel 2018-08-21 1917 ".short " #vendor ", " #device " \n" \
c9d8b55fa019162 Ard Biesheuvel 2018-08-21 1918 ".long " #class ", " #class_shift " \n" \
b1b820bb0420d08 Sami Tolvanen 2020-06-24 1919 ".long " #stub " - . \n" \
c9d8b55fa019162 Ard Biesheuvel 2018-08-21 1920 ".previous \n");
b1b820bb0420d08 Sami Tolvanen 2020-06-24 1921
b1b820bb0420d08 Sami Tolvanen 2020-06-24 1922 #define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
b1b820bb0420d08 Sami Tolvanen 2020-06-24 1923 class_shift, hook, stub) \
b1b820bb0420d08 Sami Tolvanen 2020-06-24 1924 ___DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
b1b820bb0420d08 Sami Tolvanen 2020-06-24 1925 class_shift, hook, stub)
c9d8b55fa019162 Ard Biesheuvel 2018-08-21 1926 #define DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
c9d8b55fa019162 Ard Biesheuvel 2018-08-21 1927 class_shift, hook) \
c9d8b55fa019162 Ard Biesheuvel 2018-08-21 @1928 __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
b1b820bb0420d08 Sami Tolvanen 2020-06-24 @1929 class_shift, hook, __UNIQUE_ID(hook))
c9d8b55fa019162 Ard Biesheuvel 2018-08-21 1930 #else
^1da177e4c3f415 Linus Torvalds 2005-04-16 1931 /* Anonymous variables would be nice... */
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1932 #define DECLARE_PCI_FIXUP_SECTION(section, name, vendor, device, class, \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1933 class_shift, hook) \
ecf61c78bd787b9 Michal Marek 2013-11-11 1934 static const struct pci_fixup __PASTE(__pci_fixup_##name,__LINE__) __used \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1935 __attribute__((__section__(#section), aligned((sizeof(void *))))) \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1936 = { vendor, device, class, class_shift, hook };
c9d8b55fa019162 Ard Biesheuvel 2018-08-21 1937 #endif
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1938
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1939 #define DECLARE_PCI_FIXUP_CLASS_EARLY(vendor, device, class, \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1940 class_shift, hook) \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1941 DECLARE_PCI_FIXUP_SECTION(.pci_fixup_early, \
ecf61c78bd787b9 Michal Marek 2013-11-11 1942 hook, vendor, device, class, class_shift, hook)
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1943 #define DECLARE_PCI_FIXUP_CLASS_HEADER(vendor, device, class, \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1944 class_shift, hook) \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1945 DECLARE_PCI_FIXUP_SECTION(.pci_fixup_header, \
ecf61c78bd787b9 Michal Marek 2013-11-11 1946 hook, vendor, device, class, class_shift, hook)
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1947 #define DECLARE_PCI_FIXUP_CLASS_FINAL(vendor, device, class, \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1948 class_shift, hook) \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 @1949 DECLARE_PCI_FIXUP_SECTION(.pci_fixup_final, \
ecf61c78bd787b9 Michal Marek 2013-11-11 1950 hook, vendor, device, class, class_shift, hook)
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1951 #define DECLARE_PCI_FIXUP_CLASS_ENABLE(vendor, device, class, \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1952 class_shift, hook) \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1953 DECLARE_PCI_FIXUP_SECTION(.pci_fixup_enable, \
ecf61c78bd787b9 Michal Marek 2013-11-11 1954 hook, vendor, device, class, class_shift, hook)
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1955 #define DECLARE_PCI_FIXUP_CLASS_RESUME(vendor, device, class, \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1956 class_shift, hook) \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1957 DECLARE_PCI_FIXUP_SECTION(.pci_fixup_resume, \
0aa0f5d1084ca1c Bjorn Helgaas 2017-12-02 1958 resume##hook, vendor, device, class, class_shift, hook)
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1959 #define DECLARE_PCI_FIXUP_CLASS_RESUME_EARLY(vendor, device, class, \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1960 class_shift, hook) \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1961 DECLARE_PCI_FIXUP_SECTION(.pci_fixup_resume_early, \
0aa0f5d1084ca1c Bjorn Helgaas 2017-12-02 1962 resume_early##hook, vendor, device, class, class_shift, hook)
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1963 #define DECLARE_PCI_FIXUP_CLASS_SUSPEND(vendor, device, class, \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1964 class_shift, hook) \
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1965 DECLARE_PCI_FIXUP_SECTION(.pci_fixup_suspend, \
0aa0f5d1084ca1c Bjorn Helgaas 2017-12-02 1966 suspend##hook, vendor, device, class, class_shift, hook)
7d2a01b87f1682f Andreas Noever 2014-06-03 1967 #define DECLARE_PCI_FIXUP_CLASS_SUSPEND_LATE(vendor, device, class, \
7d2a01b87f1682f Andreas Noever 2014-06-03 1968 class_shift, hook) \
7d2a01b87f1682f Andreas Noever 2014-06-03 1969 DECLARE_PCI_FIXUP_SECTION(.pci_fixup_suspend_late, \
0aa0f5d1084ca1c Bjorn Helgaas 2017-12-02 1970 suspend_late##hook, vendor, device, class, class_shift, hook)
f4ca5c6a56278ca Yinghai Lu 2012-02-23 1971

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuil...@lists.01.org
.config.gz

Nick Desaulniers

unread,
Jun 24, 2020, 7:04:02 PM6/24/20
to kernel test robot, Sami Tolvanen, Masahiro Yamada, Will Deacon, kbuil...@lists.01.org, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM
On Wed, Jun 24, 2020 at 3:50 PM kernel test robot <l...@intel.com> wrote:
>
> Hi Sami,
>
> Thank you for the patch! Perhaps something to improve:
>
> [auto build test WARNING on 26e122e97a3d0390ebec389347f64f3730fdf48f]
>
> url: https://github.com/0day-ci/linux/commits/Sami-Tolvanen/add-support-for-Clang-LTO/20200625-043816
> base: 26e122e97a3d0390ebec389347f64f3730fdf48f
> config: i386-alldefconfig (attached as .config)
> compiler: gcc-9 (Debian 9.3.0-13) 9.3.0
> reproduce (this is a W=1 build):
> # save the attached .config to linux build tree
> make W=1 ARCH=i386

Note: W=1 ^

>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <l...@intel.com>
>
> All warnings (new ones prefixed by >>):
>
> In file included from arch/x86/kernel/pci-dma.c:9:
> >> include/linux/compiler-gcc.h:72:45: warning: no previous prototype for '__UNIQUE_ID_via_no_dac190' [-Wmissing-prototypes]
> 72 | #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
> | ^~~~~~~~~~~~
> include/linux/pci.h:1914:7: note: in definition of macro '___DECLARE_PCI_FIXUP_SECTION'
> 1914 | void stub(struct pci_dev *dev) { hook(dev); } \
> | ^~~~

Should `stub` be qualified as `static inline`? https://godbolt.org/z/cPBXxW
Or should stub be declared in this header, but implemented in a .c
file? (I'm guessing the former, since the `hook` callback comes from
the macro).
--
Thanks,
~Nick Desaulniers

Nick Desaulniers

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Jun 24, 2020, 7:06:02 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
Sounds fishy; with extern linkage then I would think it's not safe to
eliminate functions. Probably unnecessary for the initial
implementation, and something we can follow up on, but always good to
have an answer to the inevitable question "why?" in the commit
message.
--
Thanks,
~Nick Desaulniers

Sami Tolvanen

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Jun 24, 2020, 7:21:45 PM6/24/20
to Nick Desaulniers, kernel test robot, Masahiro Yamada, Will Deacon, kbuil...@lists.01.org, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM
Does static inline guarantee that the compiler won't rename the symbol?
The purpose of this change is to have a stable symbol name, which we can
safely use in inline assembly.

Sami

Sami Tolvanen

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Jun 24, 2020, 7:37:31 PM6/24/20
to Peter Zijlstra, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org, linux-...@vger.kernel.org, linux-...@vger.kernel.org, linu...@vger.kernel.org, x...@kernel.org, George Burgess IV
On Wed, Jun 24, 2020 at 11:20:55PM +0200, Peter Zijlstra wrote:
> On Wed, Jun 24, 2020 at 01:31:44PM -0700, Sami Tolvanen wrote:
> > This change limits function inlining across translation unit
> > boundaries in order to reduce the binary size with LTO.
> >
> > The -import-instr-limit flag defines a size limit, as the number
> > of LLVM IR instructions, for importing functions from other TUs.
> > The default value is 100, and decreasing it to 5 reduces the size
> > of a stripped arm64 defconfig vmlinux by 11%.
>
> Is that also the right number for x86? What about the effect on
> performance? What did 6 do? or 4?

This is the size limit we decided on for Android after testing on
arm64, but the number is obviously a compromise between code size
and performance. I'd be happy to benchmark this further once other
concerns have been resolved.

Sami

Sami Tolvanen

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Jun 24, 2020, 7:40:05 PM6/24/20
to Nick Desaulniers, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
Sure. I can test this again with the current toolchain to see if there
are still problems.

Sami

Andi Kleen

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Jun 24, 2020, 7:51:46 PM6/24/20
to Nick Desaulniers, Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening, linux-arch, Linux ARM, Linux Kbuild mailing list, LKML, linu...@vger.kernel.org, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)
On Wed, Jun 24, 2020 at 02:09:40PM -0700, Nick Desaulniers wrote:
> On Wed, Jun 24, 2020 at 1:58 PM Nick Desaulniers
> <ndesau...@google.com> wrote:
> >
> > On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samito...@google.com> wrote:
> > >
> > > Filter out CC_FLAGS_LTO for the vDSO.
> >
> > Just curious about this patch (and the following one for x86's vdso),
> > do you happen to recall specifically what the issues with the vdso's
> > are?
>
> + Andi (tangential, I actually have a bunch of tabs open with slides
> from http://halobates.de/ right now)
> 58edae3aac9f2
> 67424d5a22124
> $ git log -S DISABLE_LTO

I think I did it originally because the vDSO linker step didn't do
all the magic needed for gcc LTO. But it also doesn't seem to be
very useful for just a few functions that don't have complex
interactions, and somewhat risky for violating some assumptions.

-Andi

kernel test robot

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Jun 24, 2020, 8:58:52 PM6/24/20
to Sami Tolvanen, Masahiro Yamada, Will Deacon, kbuil...@lists.01.org, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-bu...@googlegroups.com, kernel-h...@lists.openwall.com, linux...@vger.kernel.org, linux-ar...@lists.infradead.org
Hi Sami,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on 26e122e97a3d0390ebec389347f64f3730fdf48f]
config: m68k-defconfig (attached as .config)
compiler: m68k-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=m68k

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <l...@intel.com>

All error/warnings (new ones prefixed by >>):

In file included from arch/m68k/include/asm/io_mm.h:25,
from arch/m68k/include/asm/io.h:8,
from include/linux/io.h:13,
from include/linux/irq.h:20,
from include/asm-generic/hardirq.h:13,
from ./arch/m68k/include/generated/asm/hardirq.h:1,
from include/linux/hardirq.h:10,
from include/linux/interrupt.h:11,
from drivers/ide/gayle.c:13:
arch/m68k/include/asm/raw_io.h: In function 'raw_rom_outsb':
arch/m68k/include/asm/raw_io.h:83:7: warning: variable '__w' set but not used [-Wunused-but-set-variable]
83 | ({u8 __w, __v = (b); u32 _addr = ((u32) (addr)); \
| ^~~
arch/m68k/include/asm/raw_io.h:430:3: note: in expansion of macro 'rom_out_8'
430 | rom_out_8(port, *buf++);
| ^~~~~~~~~
arch/m68k/include/asm/raw_io.h: In function 'raw_rom_outsw':
arch/m68k/include/asm/raw_io.h:86:8: warning: variable '__w' set but not used [-Wunused-but-set-variable]
86 | ({u16 __w, __v = (w); u32 _addr = ((u32) (addr)); \
| ^~~
arch/m68k/include/asm/raw_io.h:448:3: note: in expansion of macro 'rom_out_be16'
448 | rom_out_be16(port, *buf++);
| ^~~~~~~~~~~~
arch/m68k/include/asm/raw_io.h: In function 'raw_rom_outsw_swapw':
arch/m68k/include/asm/raw_io.h:90:8: warning: variable '__w' set but not used [-Wunused-but-set-variable]
90 | ({u16 __w, __v = (w); u32 _addr = ((u32) (addr)); \
| ^~~
arch/m68k/include/asm/raw_io.h:466:3: note: in expansion of macro 'rom_out_le16'
466 | rom_out_le16(port, *buf++);
| ^~~~~~~~~~~~
In file included from arch/m68k/include/asm/bug.h:32,
from include/linux/bug.h:5,
from include/linux/mmdebug.h:5,
from include/linux/mm.h:9,
from drivers/ide/gayle.c:12:
include/linux/dma-mapping.h: In function 'dma_map_resource':
arch/m68k/include/asm/page_mm.h:169:49: warning: ordered comparison of pointer with null pointer [-Wextra]
169 | #define virt_addr_valid(kaddr) ((void *)(kaddr) >= (void *)PAGE_OFFSET && (void *)(kaddr) < high_memory)
| ^~
include/asm-generic/bug.h:144:27: note: in definition of macro 'WARN_ON_ONCE'
144 | int __ret_warn_once = !!(condition); \
| ^~~~~~~~~
arch/m68k/include/asm/page_mm.h:170:25: note: in expansion of macro 'virt_addr_valid'
170 | #define pfn_valid(pfn) virt_addr_valid(pfn_to_virt(pfn))
| ^~~~~~~~~~~~~~~
include/linux/dma-mapping.h:352:19: note: in expansion of macro 'pfn_valid'
352 | if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
| ^~~~~~~~~
In file included from <command-line>:
drivers/ide/gayle.c: At top level:
>> arch/m68k/include/asm/amigayle.h:57:66: error: pasting ")" and "__279_185_amiga_gayle_ide_driver_init" does not give a valid preprocessing token
57 | #define gayle (*(volatile struct GAYLE *)(zTwoBase+GAYLE_ADDRESS))
| ^
include/linux/compiler_types.h:53:23: note: in definition of macro '___PASTE'
53 | #define ___PASTE(a,b) a##b
| ^
>> include/linux/init.h:189:2: note: in expansion of macro '__PASTE'
189 | __PASTE(__KBUILD_MODNAME, \
| ^~~~~~~
>> <command-line>: note: in expansion of macro 'gayle'
>> include/linux/init.h:189:10: note: in expansion of macro '__KBUILD_MODNAME'
189 | __PASTE(__KBUILD_MODNAME, \
| ^~~~~~~~~~~~~~~~
>> include/linux/init.h:236:35: note: in expansion of macro '__initcall_id'
236 | __unique_initcall(fn, id, __sec, __initcall_id(fn))
| ^~~~~~~~~~~~~
include/linux/init.h:238:35: note: in expansion of macro '___define_initcall'
238 | #define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)
| ^~~~~~~~~~~~~~~~~~
include/linux/init.h:267:30: note: in expansion of macro '__define_initcall'
267 | #define device_initcall(fn) __define_initcall(fn, 6)
| ^~~~~~~~~~~~~~~~~
>> include/linux/init.h:272:24: note: in expansion of macro 'device_initcall'
272 | #define __initcall(fn) device_initcall(fn)
| ^~~~~~~~~~~~~~~
>> include/linux/module.h:88:24: note: in expansion of macro '__initcall'
88 | #define module_init(x) __initcall(x);
| ^~~~~~~~~~
include/linux/platform_device.h:271:1: note: in expansion of macro 'module_init'
271 | module_init(__platform_driver##_init); \
| ^~~~~~~~~~~
drivers/ide/gayle.c:185:1: note: in expansion of macro 'module_platform_driver_probe'
185 | module_platform_driver_probe(amiga_gayle_ide_driver, amiga_gayle_ide_probe);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/init.h:200:10: error: pasting "__" and "(" does not give a valid preprocessing token
200 | __PASTE(__, \
| ^~
include/linux/compiler_types.h:53:23: note: in definition of macro '___PASTE'
53 | #define ___PASTE(a,b) a##b
| ^
include/linux/init.h:200:2: note: in expansion of macro '__PASTE'
200 | __PASTE(__, \
| ^~~~~~~
>> include/linux/init.h:232:3: note: in expansion of macro '__initcall_name'
232 | __initcall_name(initcall, __iid, id), \
| ^~~~~~~~~~~~~~~
>> include/linux/init.h:236:2: note: in expansion of macro '__unique_initcall'
236 | __unique_initcall(fn, id, __sec, __initcall_id(fn))
| ^~~~~~~~~~~~~~~~~
include/linux/init.h:238:35: note: in expansion of macro '___define_initcall'
238 | #define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)
| ^~~~~~~~~~~~~~~~~~
include/linux/init.h:267:30: note: in expansion of macro '__define_initcall'
267 | #define device_initcall(fn) __define_initcall(fn, 6)
| ^~~~~~~~~~~~~~~~~
>> include/linux/init.h:272:24: note: in expansion of macro 'device_initcall'
272 | #define __initcall(fn) device_initcall(fn)
| ^~~~~~~~~~~~~~~
>> include/linux/module.h:88:24: note: in expansion of macro '__initcall'
88 | #define module_init(x) __initcall(x);
| ^~~~~~~~~~
include/linux/platform_device.h:271:1: note: in expansion of macro 'module_init'
271 | module_init(__platform_driver##_init); \
| ^~~~~~~~~~~
drivers/ide/gayle.c:185:1: note: in expansion of macro 'module_platform_driver_probe'
185 | module_platform_driver_probe(amiga_gayle_ide_driver, amiga_gayle_ide_probe);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from include/linux/printk.h:6,
from include/linux/kernel.h:15,
from include/asm-generic/bug.h:19,
from arch/m68k/include/asm/bug.h:32,
from include/linux/bug.h:5,
from include/linux/mmdebug.h:5,
from include/linux/mm.h:9,
from drivers/ide/gayle.c:12:
>> arch/m68k/include/asm/amigayle.h:57:16: error: expected declaration specifiers or '...' before '*' token
57 | #define gayle (*(volatile struct GAYLE *)(zTwoBase+GAYLE_ADDRESS))
| ^
include/linux/init.h:226:20: note: in definition of macro '____define_initcall'
226 | static initcall_t __name __used \
| ^~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/init.h:198:2: note: in expansion of macro '__PASTE'
198 | __PASTE(__, \
| ^~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/init.h:199:2: note: in expansion of macro '__PASTE'
199 | __PASTE(prefix, \
| ^~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/init.h:200:2: note: in expansion of macro '__PASTE'
200 | __PASTE(__, \
| ^~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
include/linux/init.h:201:2: note: in expansion of macro '__PASTE'
201 | __PASTE(__iid, id))))
| ^~~~~~~
>> include/linux/init.h:232:3: note: in expansion of macro '__initcall_name'
232 | __initcall_name(initcall, __iid, id), \
| ^~~~~~~~~~~~~~~
>> include/linux/init.h:236:2: note: in expansion of macro '__unique_initcall'
236 | __unique_initcall(fn, id, __sec, __initcall_id(fn))
| ^~~~~~~~~~~~~~~~~
include/linux/compiler_types.h:54:22: note: in expansion of macro '___PASTE'
54 | #define __PASTE(a,b) ___PASTE(a,b)
| ^~~~~~~~
>> include/linux/init.h:189:2: note: in expansion of macro '__PASTE'
189 | __PASTE(__KBUILD_MODNAME, \
| ^~~~~~~
>> <command-line>: note: in expansion of macro 'gayle'
>> include/linux/init.h:189:10: note: in expansion of macro '__KBUILD_MODNAME'
189 | __PASTE(__KBUILD_MODNAME, \
| ^~~~~~~~~~~~~~~~
>> include/linux/init.h:236:35: note: in expansion of macro '__initcall_id'
236 | __unique_initcall(fn, id, __sec, __initcall_id(fn))
| ^~~~~~~~~~~~~
include/linux/init.h:238:35: note: in expansion of macro '___define_initcall'
238 | #define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)
| ^~~~~~~~~~~~~~~~~~
include/linux/init.h:267:30: note: in expansion of macro '__define_initcall'
267 | #define device_initcall(fn) __define_initcall(fn, 6)
| ^~~~~~~~~~~~~~~~~
>> include/linux/init.h:272:24: note: in expansion of macro 'device_initcall'
272 | #define __initcall(fn) device_initcall(fn)
| ^~~~~~~~~~~~~~~
include/linux/module.h:88:24: note: in expansion of macro '__initcall'
88 | #define module_init(x) __initcall(x);
| ^~~~~~~~~~
include/linux/platform_device.h:271:1: note: in expansion of macro 'module_init'
271 | module_init(__platform_driver##_init); \
| ^~~~~~~~~~~
drivers/ide/gayle.c:185:1: note: in expansion of macro 'module_platform_driver_probe'
185 | module_platform_driver_probe(amiga_gayle_ide_driver, amiga_gayle_ide_probe);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from drivers/ide/gayle.c:19:
drivers/ide/gayle.c:185:30: warning: 'amiga_gayle_ide_driver_init' defined but not used [-Wunused-function]
185 | module_platform_driver_probe(amiga_gayle_ide_driver, amiga_gayle_ide_probe);
| ^~~~~~~~~~~~~~~~~~~~~~
include/linux/platform_device.h:266:19: note: in definition of macro 'module_platform_driver_probe'
266 | static int __init __platform_driver##_init(void) \
| ^~~~~~~~~~~~~~~~~

vim +200 include/linux/init.h

170
171 /*
172 * initcalls are now grouped by functionality into separate
173 * subsections. Ordering inside the subsections is determined
174 * by link order.
175 * For backwards compatibility, initcall() puts the call in
176 * the device init subsection.
177 *
178 * The `id' arg to __define_initcall() is needed so that multiple initcalls
179 * can point at the same handler without causing duplicate-symbol build errors.
180 *
181 * Initcalls are run by placing pointers in initcall sections that the
182 * kernel iterates at runtime. The linker can do dead code / data elimination
183 * and remove that completely, so the initcall sections have to be marked
184 * as KEEP() in the linker script.
185 */
186
187 /* Format: <modname>__<counter>_<line>_<fn> */
188 #define __initcall_id(fn) \
> 189 __PASTE(__KBUILD_MODNAME, \
190 __PASTE(__, \
191 __PASTE(__COUNTER__, \
192 __PASTE(_, \
193 __PASTE(__LINE__, \
194 __PASTE(_, fn))))))
195
196 /* Format: __<prefix>__<iid><id> */
197 #define __initcall_name(prefix, __iid, id) \
198 __PASTE(__, \
199 __PASTE(prefix, \
> 200 __PASTE(__, \
201 __PASTE(__iid, id))))
202
203 #ifdef CONFIG_LTO_CLANG
204 /*
205 * With LTO, the compiler doesn't necessarily obey link order for
206 * initcalls. In order to preserve the correct order, we add each
207 * variable into its own section and generate a linker script (in
208 * scripts/link-vmlinux.sh) to specify the order of the sections.
209 */
210 #define __initcall_section(__sec, __iid) \
211 #__sec ".init.." #__iid
212 #else
213 #define __initcall_section(__sec, __iid) \
214 #__sec ".init"
215 #endif
216
217 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
218 #define ____define_initcall(fn, __name, __sec) \
219 __ADDRESSABLE(fn) \
220 asm(".section \"" __sec "\", \"a\" \n" \
221 __stringify(__name) ": \n" \
222 ".long " #fn " - . \n" \
223 ".previous \n");
224 #else
225 #define ____define_initcall(fn, __name, __sec) \
2