[PATCH v2 00/13] kbuild: second round of Clang LTO refactoring
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Masahiro Yamada
Aug 31, 2021, 3:40:42 AM8/31/21
to linux-...@vger.kernel.org, Masahiro Yamada, Michal Marek, Nathan Chancellor, Nick Desaulniers, clang-bu...@googlegroups.com, linux-...@vger.kernel.org
Masahiro Yamada (13):
kbuild: move objtool_args back to scripts/Makefile.build
kbuild: rename __objtool_obj to objtool
kbuild: store the objtool command in *.cmd files
kbuild: factor out OBJECT_FILES_NON_STANDARD check into a macro
kbuild: detect objtool update without using .SECONDEXPANSION
kbuild: reuse $(cmd_objtool) for cmd_cc_lto_link_modules
kbuild: do not create built-in.a.symversions or lib.a.symversions
kbuild: build modules in the same way with/without Clang LTO
kbuild: add cmd_and_savecmd macro
kbuild: rebuild modules when objtool is updated for CONFIG_LTO_CLANG
kbuild: always postpone CRC links for module versioning
kbuild: merge cmd_modversions_c and cmd_modversions_S
kbuild: merge cmd_ar_builtin and cmd_ar_module
scripts/Kbuild.include | 6 +-
scripts/Makefile.build | 207 ++++++++++++++++----------------------
scripts/Makefile.lib | 27 ++---
scripts/Makefile.modfinal | 4 +-
scripts/Makefile.modpost | 7 +-
scripts/link-vmlinux.sh | 31 +++---
scripts/merge-symvers.pl | 52 ++++++++++
scripts/mod/modpost.c | 6 +-
8 files changed, 175 insertions(+), 165 deletions(-)
create mode 100644 scripts/merge-symvers.pl
--
2.30.2
Masahiro Yamada
Aug 31, 2021, 3:40:42 AM8/31/21
to linux-...@vger.kernel.org, Masahiro Yamada, Michal Marek, Nathan Chancellor, Nick Desaulniers, clang-bu...@googlegroups.com, linux-...@vger.kernel.org
For CONFIG_LTO_CLANG=y, the objtool processing is not possible at the
compilation, hence postponed by the link time.
Reuse $(cmd_objtool) for CONFIG_LTO_CLANG=y by defining objtool-enabled
properly.
For CONFIG_LTO_CLANG=y:
objtool-enabled is off for %.o compilation
objtool-enabled is on for %.lto link
For CONFIG_LTO_CLANG=n:
objtool-enabled is on for %.o compilation
(but, it depends on OBJECT_FILE_NON_STANDARD)
Set part-of-module := y for %.lto.o to avoid repeating --module.
Signed-off-by: Masahiro Yamada <masa...@kernel.org>
---
scripts/Makefile.build | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 21b55f37a23f..afc906cd7256 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -236,20 +236,26 @@ objtool_args = \
$(if $(CONFIG_X86_SMAP), --uaccess) \
$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount)
-ifndef CONFIG_LTO_CLANG
+cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $@)
+cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
+
+endif # CONFIG_STACK_VALIDATION
+
+ifdef CONFIG_LTO_CLANG
+
+# Skip objtool for LLVM bitcode
+$(obj)/%o: objtool-enabled :=
+
+else
# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
# 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
# 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
-objtool-enabled = $(if $(filter-out y%, \
+$(obj)/%o: objtool-enabled = $(if $(filter-out y%, \
$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y)
-cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $@)
-cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
-
-endif # CONFIG_LTO_CLANG
-endif # CONFIG_STACK_VALIDATION
+endif
ifdef CONFIG_TRIM_UNUSED_KSYMS
cmd_gen_ksymdeps = \
@@ -289,13 +295,13 @@ cmd_cc_lto_link_modules = \
$(LD) $(ld_flags) -r -o $@ \
$(shell [ -s $(@:.lto.o=.o.symversions) ] && \
echo -T $(@:.lto.o=.o.symversions)) \
- --whole-archive $(filter-out FORCE,$^)
+ --whole-archive $(filter-out FORCE,$^) \
+ $(cmd_objtool)
-ifdef CONFIG_STACK_VALIDATION
# objtool was skipped for LLVM bitcode, run it now that we have compiled
# modules into native code
-cmd_cc_lto_link_modules += ; $(objtool) $(objtool_args) --module $@
-endif
+$(obj)/%.lto.o: objtool-enabled = y
+$(obj)/%.lto.o: part-of-module := y
$(obj)/%.lto.o: $(obj)/%.o FORCE
$(call if_changed,cc_lto_link_modules)
--
2.30.2
compilation, hence postponed by the link time.
Reuse $(cmd_objtool) for CONFIG_LTO_CLANG=y by defining objtool-enabled
properly.
For CONFIG_LTO_CLANG=y:
objtool-enabled is off for %.o compilation
objtool-enabled is on for %.lto link
For CONFIG_LTO_CLANG=n:
objtool-enabled is on for %.o compilation
(but, it depends on OBJECT_FILE_NON_STANDARD)
Set part-of-module := y for %.lto.o to avoid repeating --module.
Signed-off-by: Masahiro Yamada <masa...@kernel.org>
---
scripts/Makefile.build | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 21b55f37a23f..afc906cd7256 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -236,20 +236,26 @@ objtool_args = \
$(if $(CONFIG_X86_SMAP), --uaccess) \
$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount)
-ifndef CONFIG_LTO_CLANG
+cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $@)
+cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
+
+endif # CONFIG_STACK_VALIDATION
+
+ifdef CONFIG_LTO_CLANG
+
+# Skip objtool for LLVM bitcode
+$(obj)/%o: objtool-enabled :=
+
+else
# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
# 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
# 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
-objtool-enabled = $(if $(filter-out y%, \
+$(obj)/%o: objtool-enabled = $(if $(filter-out y%, \
$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y)
-cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $@)
-cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
-
-endif # CONFIG_LTO_CLANG
-endif # CONFIG_STACK_VALIDATION
+endif
ifdef CONFIG_TRIM_UNUSED_KSYMS
cmd_gen_ksymdeps = \
@@ -289,13 +295,13 @@ cmd_cc_lto_link_modules = \
$(LD) $(ld_flags) -r -o $@ \
$(shell [ -s $(@:.lto.o=.o.symversions) ] && \
echo -T $(@:.lto.o=.o.symversions)) \
- --whole-archive $(filter-out FORCE,$^)
+ --whole-archive $(filter-out FORCE,$^) \
+ $(cmd_objtool)
-ifdef CONFIG_STACK_VALIDATION
# objtool was skipped for LLVM bitcode, run it now that we have compiled
# modules into native code
-cmd_cc_lto_link_modules += ; $(objtool) $(objtool_args) --module $@
-endif
+$(obj)/%.lto.o: objtool-enabled = y
+$(obj)/%.lto.o: part-of-module := y
$(obj)/%.lto.o: $(obj)/%.o FORCE
$(call if_changed,cc_lto_link_modules)
--
2.30.2
Masahiro Yamada
Aug 31, 2021, 3:40:43 AM8/31/21
to linux-...@vger.kernel.org, Masahiro Yamada, Michal Marek, Nathan Chancellor, Nick Desaulniers, clang-bu...@googlegroups.com, linux-...@vger.kernel.org
When Clang LTO is enabled, additional intermediate files *.lto.o are
created because LLVM bitcode must be converted to ELF before modpost.
For non-LTO builds:
$(LD) $(LD)
objects ---> <modname>.o -----> <modname>.ko
|
<modname>.mod.o ---/
For Clang LTO builds:
$(AR) $(LD) $(LD)
objects ---> <modname>.o ---> <modname>.lto.o -----> <modname>.ko
|
<modname>.mod.o --/
Since the Clang LTO introduction, Kbuild code is complicated due to
CONFIG_LTO_CLANG conditionals sprinkled everywhere.
Another confusion for Clang LTO builds is, <modname>.o is an archive
that contains LLVM bitcode files. The suffix should be .a instead of .o
To clean up the code, unify the build process of modules, as follows:
$(AR) $(LD) $(LD)
objects ---> <modname>.a ---> <modname>.prelink.o -----> <modname>.ko
|
<modname>.mod.o ------/
Here, 'objects' are either ELF or LLVM bitcode. <modname>.a is an archive,
<modname>.prelink.o is ELF.
scripts/Makefile.build | 100 +++++++++++++++++---------------------
scripts/Makefile.lib | 11 ++---
scripts/Makefile.modfinal | 4 +-
scripts/Makefile.modpost | 7 +--
scripts/mod/modpost.c | 6 +--
5 files changed, 56 insertions(+), 72 deletions(-)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 3ad1b1227371..cdc09e9080ca 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -88,9 +88,7 @@ endif
targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
-ifdef CONFIG_LTO_CLANG
-targets-for-modules += $(patsubst %.o, %.lto.o, $(filter %.o, $(obj-m)))
-endif
+targets-for-modules += $(patsubst %.o, %.prelink.o, $(filter %.o, $(obj-m)))
ifdef need-modorder
targets-for-modules += $(obj)/modules.order
@@ -243,9 +241,12 @@ endif # CONFIG_STACK_VALIDATION
ifdef CONFIG_LTO_CLANG
-# Skip objtool for LLVM bitcode
+# Skip objtool LLVM bitcode
$(obj)/%o: objtool-enabled :=
+# Run objtool now that we have compiled modules into native code
+$(obj)/%.prelink.o: objtool-enabled := y
+
+
endif
ifdef CONFIG_TRIM_UNUSED_KSYMS
@@ -287,32 +290,12 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
$(call if_changed_rule,cc_o_c)
$(call cmd,force_checksrc)
-ifdef CONFIG_LTO_CLANG
-# Module .o files may contain LLVM bitcode, compile them into native code
-# before ELF processing
-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 $(filter-out FORCE,$^) \
- $(cmd_objtool)
-
-# objtool was skipped for LLVM bitcode, run it now that we have compiled
-# modules into native code
-$(obj)/%.lto.o: objtool-enabled = y
-$(obj)/%.lto.o: part-of-module := y
-
-$(obj)/%.lto.o: $(obj)/%.o FORCE
- $(call if_changed,cc_lto_link_modules)
-endif
-
cmd_mod = { \
echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \
$(undefined_syms) echo; \
} > $@
-$(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE
+$(obj)/%.mod: $(obj)/%.prelink.o FORCE
$(call if_changed,mod)
quiet_cmd_cc_lst_c = MKLST $@
@@ -416,17 +399,6 @@ $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
$(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ;
$(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
-# combine symversions for later processing
-ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
- cmd_update_lto_symversions = \
- rm -f $@.symversions \
- $(foreach n, $(filter-out FORCE,$^), \
- $(if $(shell test -s $(n).symversions && echo y), \
- ; 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)
#
@@ -446,10 +418,10 @@ $(obj)/built-in.a: $(real-obj-y) FORCE
# modules.order unless contained modules are updated.
cmd_modules_order = { $(foreach m, $(real-prereqs), \
- $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.o,%.ko,$m));) :; } \
+ $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.a,%.ko,$m));) :; } \
| $(AWK) '!x[$$0]++' - > $@
-$(obj)/modules.order: $(obj-m) FORCE
+$(obj)/modules.order: $(modules) FORCE
$(call if_changed,modules_order)
#
@@ -458,26 +430,44 @@ $(obj)/modules.order: $(obj-m) FORCE
$(obj)/lib.a: $(lib-y) FORCE
$(call if_changed,ar)
-# NOTE:
-# 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 = \
- $(cmd_update_lto_symversions); \
- rm -f $@; \
- $(AR) cDPrsT $@ $(filter %.o,$^)
-else
-quiet_cmd_link_multi-m = LD [M] $@
- cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
+#
+# Rule to prelink modules
+#
+
+ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
+
+cmd_merge_symver = $(PERL) scripts/merge-symvers.pl -a $(AR) -o $@ $<
+
+$(obj)/%.prelink.symversions: $(obj)/%.a FORCE
+ $(call if_changed,merge_symver)
+
+targets += $(patsubst %.a, %.prelink.symversions, $(modules))
+
+$(obj)/%.prelink.o: ld_flags += --script=$(filter %.symversions,$^)
+module-symver = $(obj)/%.prelink.symversions
+
endif
-$(multi-obj-m): FORCE
- $(call if_changed,link_multi-m)
-$(call multi_depend, $(multi-obj-m), .o, -objs -y -m)
+quiet_cmd_ld_o_a = LD [M] $@
+ cmd_ld_o_a = $(LD) $(ld_flags) -r -o $@ --whole-archive $< $(cmd_objtool)
+
+$(obj)/%.prelink.o: part-of-module := y
+
+$(obj)/%.prelink.o: $(obj)/%.a $(module-symver) FORCE
+ $(call if_changed,ld_o_a)
+
+quiet_cmd_ar_module = AR [M] $@
+ cmd_ar_module = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
+
+$(modules-single): %.a: %.o FORCE
+ $(call if_changed,ar_module)
+
+$(modules-multi): FORCE
+ $(call if_changed,ar_module)
+$(call multi_depend, $(modules-multi), .a, -objs -y -m)
+
+targets += $(modules-single) $(modules-multi)
-targets += $(multi-obj-m)
targets := $(filter-out $(PHONY), $(targets))
# Add intermediate targets:
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 34c4c11c4bc1..5074922db82d 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -106,6 +106,10 @@ multi-dtb-y := $(addprefix $(obj)/, $(multi-dtb-y))
real-dtb-y := $(addprefix $(obj)/, $(real-dtb-y))
subdir-ym := $(addprefix $(obj)/,$(subdir-ym))
+modules := $(patsubst %.o, %.a, $(obj-m))
+modules-multi := $(sort $(patsubst %.o, %.a, $(multi-obj-m)))
+modules-single := $(sort $(filter-out $(modules-multi), $(filter %.a, $(modules))))
+
# Finds the multi-part object the current object will be linked into.
# If the object belongs to two or more multi-part objects, list them all.
modname-multi = $(sort $(foreach m,$(multi-obj-ym),\
@@ -225,13 +229,6 @@ dtc_cpp_flags = -Wp,-MMD,$(depfile).pre.tmp -nostdinc \
$(addprefix -I,$(DTC_INCLUDE)) \
-undef -D__DTS__
-ifeq ($(CONFIG_LTO_CLANG),y)
-# With CONFIG_LTO_CLANG, .o files in modules might be LLVM bitcode, so we
-# need to run LTO to compile them into native code (.lto.o) before further
-# processing.
-mod-prelink-ext := .lto
-endif
-
# Useful for describing the dependency of composite objects
# Usage:
# $(call multi_depend, multi_used_targets, suffix_to_remove, suffix_to_add)
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index ff805777431c..1b6401f53662 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -9,7 +9,7 @@ __modfinal:
include include/config/auto.conf
include $(srctree)/scripts/Kbuild.include
-# for c_flags and mod-prelink-ext
+# for c_flags
include $(srctree)/scripts/Makefile.lib
# find all modules listed in modules.order
@@ -55,7 +55,7 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \
# Re-generate module BTFs if either module's .ko or vmlinux changed
-$(modules): %.ko: %$(mod-prelink-ext).o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE
+$(modules): %.ko: %.prelink.o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE
+$(call if_changed_except,ld_ko_o,vmlinux)
ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+$(if $(newer-prereqs),$(call cmd,btf_ko))
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index eef56d629799..11883b31c615 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -41,9 +41,6 @@ __modpost:
include include/config/auto.conf
include $(srctree)/scripts/Kbuild.include
-# for mod-prelink-ext
-include $(srctree)/scripts/Makefile.lib
-
MODPOST = scripts/mod/modpost \
$(if $(CONFIG_MODVERSIONS),-m) \
$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \
@@ -128,9 +125,9 @@ endif
# 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$$/$(mod-prelink-ext)\.o/' $< | $(MODPOST) -T -
+ cmd_modpost = sed 's/ko$$/prelink.o/' $< | $(MODPOST) -T -
-$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(mod-prelink-ext).o) FORCE
+$(output-symdump): $(MODORDER) $(input-symdump) $(modules:ko=prelink.o) FORCE
$(call if_changed,modpost)
targets += $(output-symdump)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index a26139aa57fd..56cd9b7a5dd0 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2000,9 +2000,9 @@ 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';
+ /* strip trailing .prelink */
+ if (strends(tmp, ".prelink"))
+ tmp[strlen(tmp) - 8] = '\0';
mod = new_module(tmp);
free(tmp);
}
--
2.30.2
created because LLVM bitcode must be converted to ELF before modpost.
For non-LTO builds:
$(LD) $(LD)
objects ---> <modname>.o -----> <modname>.ko
|
<modname>.mod.o ---/
For Clang LTO builds:
$(AR) $(LD) $(LD)
objects ---> <modname>.o ---> <modname>.lto.o -----> <modname>.ko
|
<modname>.mod.o --/
Since the Clang LTO introduction, Kbuild code is complicated due to
CONFIG_LTO_CLANG conditionals sprinkled everywhere.
Another confusion for Clang LTO builds is, <modname>.o is an archive
that contains LLVM bitcode files. The suffix should be .a instead of .o
To clean up the code, unify the build process of modules, as follows:
$(AR) $(LD) $(LD)
objects ---> <modname>.a ---> <modname>.prelink.o -----> <modname>.ko
|
<modname>.mod.o ------/
Here, 'objects' are either ELF or LLVM bitcode. <modname>.a is an archive,
<modname>.prelink.o is ELF.
scripts/Makefile.build | 100 +++++++++++++++++---------------------
scripts/Makefile.lib | 11 ++---
scripts/Makefile.modfinal | 4 +-
scripts/Makefile.modpost | 7 +--
scripts/mod/modpost.c | 6 +--
5 files changed, 56 insertions(+), 72 deletions(-)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 3ad1b1227371..cdc09e9080ca 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -88,9 +88,7 @@ endif
targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
-ifdef CONFIG_LTO_CLANG
-targets-for-modules += $(patsubst %.o, %.lto.o, $(filter %.o, $(obj-m)))
-endif
+targets-for-modules += $(patsubst %.o, %.prelink.o, $(filter %.o, $(obj-m)))
ifdef need-modorder
targets-for-modules += $(obj)/modules.order
@@ -243,9 +241,12 @@ endif # CONFIG_STACK_VALIDATION
ifdef CONFIG_LTO_CLANG
-# Skip objtool for LLVM bitcode
+# Skip objtool LLVM bitcode
$(obj)/%o: objtool-enabled :=
+# Run objtool now that we have compiled modules into native code
+$(obj)/%.prelink.o: objtool-enabled := y
+
else
# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
@@ -255,6 +256,8 @@ else
# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
$(obj)/%o: objtool-enabled = $(if $(filter-out y%, \
$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y)
+$(obj)/%.prelink.o: objtool-enabled :=
$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y)
+
endif
ifdef CONFIG_TRIM_UNUSED_KSYMS
@@ -287,32 +290,12 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
$(call if_changed_rule,cc_o_c)
$(call cmd,force_checksrc)
-ifdef CONFIG_LTO_CLANG
-# Module .o files may contain LLVM bitcode, compile them into native code
-# before ELF processing
-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,$^) \
- $(cmd_objtool)
-
-# objtool was skipped for LLVM bitcode, run it now that we have compiled
-# modules into native code
-$(obj)/%.lto.o: objtool-enabled = y
-$(obj)/%.lto.o: part-of-module := y
-
-$(obj)/%.lto.o: $(obj)/%.o FORCE
- $(call if_changed,cc_lto_link_modules)
-endif
-
cmd_mod = { \
echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \
$(undefined_syms) echo; \
} > $@
-$(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE
+$(obj)/%.mod: $(obj)/%.prelink.o FORCE
$(call if_changed,mod)
quiet_cmd_cc_lst_c = MKLST $@
@@ -416,17 +399,6 @@ $(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
-ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
- cmd_update_lto_symversions = \
- rm -f $@.symversions \
- $(foreach n, $(filter-out FORCE,$^), \
- $(if $(shell test -s $(n).symversions && echo y), \
- ; 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)
#
@@ -446,10 +418,10 @@ $(obj)/built-in.a: $(real-obj-y) FORCE
# modules.order unless contained modules are updated.
cmd_modules_order = { $(foreach m, $(real-prereqs), \
- $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.o,%.ko,$m));) :; } \
+ $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.a,%.ko,$m));) :; } \
| $(AWK) '!x[$$0]++' - > $@
-$(obj)/modules.order: $(obj-m) FORCE
+$(obj)/modules.order: $(modules) FORCE
$(call if_changed,modules_order)
#
@@ -458,26 +430,44 @@ $(obj)/modules.order: $(obj-m) FORCE
$(obj)/lib.a: $(lib-y) FORCE
$(call if_changed,ar)
-# NOTE:
-# 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 = \
- $(cmd_update_lto_symversions); \
- rm -f $@; \
- $(AR) cDPrsT $@ $(filter %.o,$^)
-else
-quiet_cmd_link_multi-m = LD [M] $@
- cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
+#
+# Rule to prelink modules
+#
+
+ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
+
+cmd_merge_symver = $(PERL) scripts/merge-symvers.pl -a $(AR) -o $@ $<
+
+$(obj)/%.prelink.symversions: $(obj)/%.a FORCE
+ $(call if_changed,merge_symver)
+
+targets += $(patsubst %.a, %.prelink.symversions, $(modules))
+
+$(obj)/%.prelink.o: ld_flags += --script=$(filter %.symversions,$^)
+module-symver = $(obj)/%.prelink.symversions
+
endif
-$(multi-obj-m): FORCE
- $(call if_changed,link_multi-m)
-$(call multi_depend, $(multi-obj-m), .o, -objs -y -m)
+quiet_cmd_ld_o_a = LD [M] $@
+ cmd_ld_o_a = $(LD) $(ld_flags) -r -o $@ --whole-archive $< $(cmd_objtool)
+
+$(obj)/%.prelink.o: part-of-module := y
+
+$(obj)/%.prelink.o: $(obj)/%.a $(module-symver) FORCE
+ $(call if_changed,ld_o_a)
+
+quiet_cmd_ar_module = AR [M] $@
+ cmd_ar_module = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
+
+$(modules-single): %.a: %.o FORCE
+ $(call if_changed,ar_module)
+
+$(modules-multi): FORCE
+ $(call if_changed,ar_module)
+$(call multi_depend, $(modules-multi), .a, -objs -y -m)
+
+targets += $(modules-single) $(modules-multi)
-targets += $(multi-obj-m)
targets := $(filter-out $(PHONY), $(targets))
# Add intermediate targets:
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 34c4c11c4bc1..5074922db82d 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -106,6 +106,10 @@ multi-dtb-y := $(addprefix $(obj)/, $(multi-dtb-y))
real-dtb-y := $(addprefix $(obj)/, $(real-dtb-y))
subdir-ym := $(addprefix $(obj)/,$(subdir-ym))
+modules := $(patsubst %.o, %.a, $(obj-m))
+modules-multi := $(sort $(patsubst %.o, %.a, $(multi-obj-m)))
+modules-single := $(sort $(filter-out $(modules-multi), $(filter %.a, $(modules))))
+
# Finds the multi-part object the current object will be linked into.
# If the object belongs to two or more multi-part objects, list them all.
modname-multi = $(sort $(foreach m,$(multi-obj-ym),\
@@ -225,13 +229,6 @@ dtc_cpp_flags = -Wp,-MMD,$(depfile).pre.tmp -nostdinc \
$(addprefix -I,$(DTC_INCLUDE)) \
-undef -D__DTS__
-ifeq ($(CONFIG_LTO_CLANG),y)
-# With CONFIG_LTO_CLANG, .o files in modules might be LLVM bitcode, so we
-# need to run LTO to compile them into native code (.lto.o) before further
-# processing.
-mod-prelink-ext := .lto
-endif
-
# Useful for describing the dependency of composite objects
# Usage:
# $(call multi_depend, multi_used_targets, suffix_to_remove, suffix_to_add)
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index ff805777431c..1b6401f53662 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -9,7 +9,7 @@ __modfinal:
include include/config/auto.conf
include $(srctree)/scripts/Kbuild.include
-# for c_flags and mod-prelink-ext
+# for c_flags
include $(srctree)/scripts/Makefile.lib
# find all modules listed in modules.order
@@ -55,7 +55,7 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \
# Re-generate module BTFs if either module's .ko or vmlinux changed
-$(modules): %.ko: %$(mod-prelink-ext).o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE
+$(modules): %.ko: %.prelink.o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE
+$(call if_changed_except,ld_ko_o,vmlinux)
ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+$(if $(newer-prereqs),$(call cmd,btf_ko))
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index eef56d629799..11883b31c615 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -41,9 +41,6 @@ __modpost:
include include/config/auto.conf
include $(srctree)/scripts/Kbuild.include
-# for mod-prelink-ext
-include $(srctree)/scripts/Makefile.lib
-
MODPOST = scripts/mod/modpost \
$(if $(CONFIG_MODVERSIONS),-m) \
$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \
@@ -128,9 +125,9 @@ endif
# 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$$/$(mod-prelink-ext)\.o/' $< | $(MODPOST) -T -
+ cmd_modpost = sed 's/ko$$/prelink.o/' $< | $(MODPOST) -T -
-$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(mod-prelink-ext).o) FORCE
+$(output-symdump): $(MODORDER) $(input-symdump) $(modules:ko=prelink.o) FORCE
$(call if_changed,modpost)
targets += $(output-symdump)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index a26139aa57fd..56cd9b7a5dd0 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2000,9 +2000,9 @@ 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';
+ /* strip trailing .prelink */
+ if (strends(tmp, ".prelink"))
+ tmp[strlen(tmp) - 8] = '\0';
mod = new_module(tmp);
free(tmp);
}
--
2.30.2
Masahiro Yamada
Aug 31, 2021, 3:41:23 AM8/31/21
to linux-...@vger.kernel.org, Masahiro Yamada, Kees Cook, Michal Marek, Nathan Chancellor, Nick Desaulniers, clang-bu...@googlegroups.com, linux-...@vger.kernel.org
Now cmd_modversions_c and cmd_modversions_S are similar.
The latter uses $(OBJDUMP) -h, but it can be replaced with $(NM).
$(NM) works for both ELF and LLVM bitcode (if $(NM) is llvm-nm).
Signed-off-by: Masahiro Yamada <masa...@kernel.org>
Reviewed-by: Kees Cook <kees...@chromium.org>
---
scripts/Makefile.build | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 50a6765c9a14..4d12f83389ce 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -166,13 +166,16 @@ ifdef CONFIG_MODVERSIONS
# 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 = \
+cmd_modversions = \
if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then \
- $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
+ $(call cmd_gensymtypes_$(1),$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
> $@.symversions; \
else \
rm -f $@.symversions; \
fi;
+
+cmd_modversions_c = $(call cmd_modversions,c)
+
endif
ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
@@ -337,14 +340,8 @@ ifdef CONFIG_ASM_MODVERSIONS
# versioning matches the C process described above, with difference that
# we parse asm-prototypes.h C header to get function definitions.
+cmd_modversions_S = $(call cmd_modversions,S)
-cmd_modversions_S = \
- if $(OBJDUMP) -h $@ | grep -q __ksymtab; then \
- $(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
- > $@.symversions; \
- else \
- rm -rf $@.symversions; \
- fi
endif
$(obj)/%.o: $(src)/%.S FORCE
--
2.30.2
The latter uses $(OBJDUMP) -h, but it can be replaced with $(NM).
$(NM) works for both ELF and LLVM bitcode (if $(NM) is llvm-nm).
Signed-off-by: Masahiro Yamada <masa...@kernel.org>
Reviewed-by: Kees Cook <kees...@chromium.org>
---
scripts/Makefile.build | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 50a6765c9a14..4d12f83389ce 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -166,13 +166,16 @@ ifdef CONFIG_MODVERSIONS
# 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 = \
+cmd_modversions = \
if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then \
- $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
+ $(call cmd_gensymtypes_$(1),$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
> $@.symversions; \
else \
rm -f $@.symversions; \
fi;
+
+cmd_modversions_c = $(call cmd_modversions,c)
+
endif
ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
@@ -337,14 +340,8 @@ ifdef CONFIG_ASM_MODVERSIONS
# versioning matches the C process described above, with difference that
# we parse asm-prototypes.h C header to get function definitions.
+cmd_modversions_S = $(call cmd_modversions,S)
-cmd_modversions_S = \
- if $(OBJDUMP) -h $@ | grep -q __ksymtab; then \
- $(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
- > $@.symversions; \
- else \
- rm -rf $@.symversions; \
- fi
endif
$(obj)/%.o: $(src)/%.S FORCE
--
2.30.2
Masahiro Yamada
Aug 31, 2021, 3:41:23 AM8/31/21
to linux-...@vger.kernel.org, Masahiro Yamada, Kees Cook, Michal Marek, Nathan Chancellor, Nick Desaulniers, clang-bu...@googlegroups.com, linux-...@vger.kernel.org
When CONFIG_MODVERSIONS=y, the CRCs of EXPORT_SYMBOL are linked into
*.o files in-place.
It is impossible for Clang LTO because *.o files are not ELF, but LLVM
bitcode. The CRCs are stored in separate *.symversions files, and then
supplied to the modpost link.
Let's do so for CONFIG_LTO_CLANG=n, and unify the module versioning code.
Signed-off-by: Masahiro Yamada <masa...@kernel.org>
Reviewed-by: Kees Cook <kees...@chromium.org>
---
scripts/Makefile.build | 32 ++++++--------------------------
scripts/link-vmlinux.sh | 22 ++++++++++++++--------
2 files changed, 20 insertions(+), 34 deletions(-)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index b94dfc87b7fa..50a6765c9a14 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -158,17 +158,12 @@ quiet_cmd_cc_o_c = CC $(quiet_modtag) $@
ifdef CONFIG_MODVERSIONS
# When module versioning is enabled the following steps are executed:
# o compile a <file>.o from <file>.c
-# o if <file>.o doesn't contain a __ksymtab version, i.e. does
-# not export symbols, it's done.
+# o if <file>.o doesn't contain __ksymtab* symbols, i.e. does
+# not export symbols, create an empty *.symversions
# o otherwise, we calculate symbol versions using the good old
# genksyms on the preprocessed source and postprocess them in a way
# that they are usable as a linker script
-# o generate .tmp_<file>.o from <file>.o using the linker to
-# replace the unresolved symbols __crc_exported_symbol with
-# the actual value of the checksum generated by genksyms
-# o remove .tmp_<file>.o to <file>.o
-ifdef CONFIG_LTO_CLANG
@@ -178,18 +173,6 @@ cmd_modversions_c = \
-cmd_modversions_c = \
- > $(@D)/.tmp_$(@F:.o=.ver); \
- \
- $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@ \
- -T $(@D)/.tmp_$(@F:.o=.ver); \
- mv -f $(@D)/.tmp_$(@F) $@; \
- rm -f $(@D)/.tmp_$(@F:.o=.ver); \
- fi
-endif
endif
ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
@@ -358,12 +341,9 @@ ifdef CONFIG_ASM_MODVERSIONS
cmd_modversions_S = \
- > $(@D)/.tmp_$(@F:.o=.ver); \
- \
- $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@ \
- -T $(@D)/.tmp_$(@F:.o=.ver); \
- mv -f $(@D)/.tmp_$(@F) $@; \
- rm -f $(@D)/.tmp_$(@F:.o=.ver); \
+ > $@.symversions; \
+ else \
+ rm -rf $@.symversions; \
fi
endif
@@ -434,7 +414,7 @@ $(obj)/lib.a: $(lib-y) FORCE
# Rule to prelink modules
#
-ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
+ifdef CONFIG_MODVERSIONS
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 0cc6a03f2cb1..366af3a9d039 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -52,8 +52,7 @@ gen_initcalls()
> .tmp_initcalls.lds
}
-# If CONFIG_LTO_CLANG is selected, collect generated symbol versions into
-# .tmp_symversions.lds
+# Collect generated symbol versions into .tmp_symversions.lds
gen_symversions()
{
info GEN .tmp_symversions.lds
@@ -75,14 +74,13 @@ modpost_link()
${KBUILD_VMLINUX_LIBS} \
--end-group"
+ if [ -n "${CONFIG_MODVERSIONS}" ]; then
+ lds="${lds} -T .tmp_symversions.lds"
+ fi
+
if [ -n "${CONFIG_LTO_CLANG}" ]; then
gen_initcalls
- lds="-T .tmp_initcalls.lds"
-
- if [ -n "${CONFIG_MODVERSIONS}" ]; then
- gen_symversions
- lds="${lds} -T .tmp_symversions.lds"
- fi
+ lds="${lds} -T .tmp_initcalls.lds"
# This might take a while, so indicate that we're doing
# an LTO link
@@ -179,6 +177,10 @@ vmlinux_link()
ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
+ if [ -n "${CONFIG_MODVERSIONS}" ]; then
+ ldflags="${ldflags} ${wl}--script=.tmp_symversions.lds"
+ fi
+
# The kallsyms linking does not need debug symbols included.
if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
ldflags="${ldflags} ${wl}--strip-debug"
@@ -332,6 +334,10 @@ fi;
# final build of init/
${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1
+if [ -n "${CONFIG_MODVERSIONS}" ]; then
+ gen_symversions
+fi
+
#link vmlinux.o
modpost_link vmlinux.o
objtool_link vmlinux.o
--
2.30.2
*.o files in-place.
It is impossible for Clang LTO because *.o files are not ELF, but LLVM
bitcode. The CRCs are stored in separate *.symversions files, and then
supplied to the modpost link.
Let's do so for CONFIG_LTO_CLANG=n, and unify the module versioning code.
Signed-off-by: Masahiro Yamada <masa...@kernel.org>
Reviewed-by: Kees Cook <kees...@chromium.org>
---
scripts/link-vmlinux.sh | 22 ++++++++++++++--------
2 files changed, 20 insertions(+), 34 deletions(-)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index b94dfc87b7fa..50a6765c9a14 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -158,17 +158,12 @@ quiet_cmd_cc_o_c = CC $(quiet_modtag) $@
ifdef CONFIG_MODVERSIONS
# When module versioning is enabled the following steps are executed:
# o compile a <file>.o from <file>.c
-# o if <file>.o doesn't contain a __ksymtab version, i.e. does
-# not export symbols, it's done.
+# o if <file>.o doesn't contain __ksymtab* symbols, i.e. does
+# not export symbols, create an empty *.symversions
# o otherwise, we calculate symbol versions using the good old
# genksyms on the preprocessed source and postprocess them in a way
# that they are usable as a linker script
-# o generate .tmp_<file>.o from <file>.o using the linker to
-# replace the unresolved symbols __crc_exported_symbol with
-# 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 = \
# to the kernel and/or modules at the end.
@@ -178,18 +173,6 @@ cmd_modversions_c = \
else \
rm -f $@.symversions; \
fi;
-else
rm -f $@.symversions; \
fi;
-cmd_modversions_c = \
- if $(OBJDUMP) -h $@ | grep -q __ksymtab; then \
- $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
- > $(@D)/.tmp_$(@F:.o=.ver); \
- \
- $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@ \
- -T $(@D)/.tmp_$(@F:.o=.ver); \
- mv -f $(@D)/.tmp_$(@F) $@; \
- rm -f $(@D)/.tmp_$(@F:.o=.ver); \
- fi
-endif
endif
ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
@@ -358,12 +341,9 @@ ifdef CONFIG_ASM_MODVERSIONS
cmd_modversions_S = \
if $(OBJDUMP) -h $@ | grep -q __ksymtab; then \
$(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
- > $(@D)/.tmp_$(@F:.o=.ver); \
- \
- $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@ \
- -T $(@D)/.tmp_$(@F:.o=.ver); \
- mv -f $(@D)/.tmp_$(@F) $@; \
- rm -f $(@D)/.tmp_$(@F:.o=.ver); \
+ > $@.symversions; \
+ else \
+ rm -rf $@.symversions; \
fi
endif
@@ -434,7 +414,7 @@ $(obj)/lib.a: $(lib-y) FORCE
# Rule to prelink modules
#
-ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
+ifdef CONFIG_MODVERSIONS
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 0cc6a03f2cb1..366af3a9d039 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -52,8 +52,7 @@ gen_initcalls()
> .tmp_initcalls.lds
}
-# If CONFIG_LTO_CLANG is selected, collect generated symbol versions into
-# .tmp_symversions.lds
+# Collect generated symbol versions into .tmp_symversions.lds
gen_symversions()
{
info GEN .tmp_symversions.lds
@@ -75,14 +74,13 @@ modpost_link()
${KBUILD_VMLINUX_LIBS} \
--end-group"
+ if [ -n "${CONFIG_MODVERSIONS}" ]; then
+ lds="${lds} -T .tmp_symversions.lds"
+ fi
+
if [ -n "${CONFIG_LTO_CLANG}" ]; then
gen_initcalls
- lds="-T .tmp_initcalls.lds"
-
- if [ -n "${CONFIG_MODVERSIONS}" ]; then
- gen_symversions
- lds="${lds} -T .tmp_symversions.lds"
- fi
+ lds="${lds} -T .tmp_initcalls.lds"
# This might take a while, so indicate that we're doing
# an LTO link
@@ -179,6 +177,10 @@ vmlinux_link()
ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
+ if [ -n "${CONFIG_MODVERSIONS}" ]; then
+ ldflags="${ldflags} ${wl}--script=.tmp_symversions.lds"
+ fi
+
# The kallsyms linking does not need debug symbols included.
if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
ldflags="${ldflags} ${wl}--strip-debug"
@@ -332,6 +334,10 @@ fi;
# final build of init/
${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1
+if [ -n "${CONFIG_MODVERSIONS}" ]; then
+ gen_symversions
+fi
+
#link vmlinux.o
modpost_link vmlinux.o
objtool_link vmlinux.o
--
2.30.2
Kees Cook
Aug 31, 2021, 1:35:32 PM8/31/21
to Masahiro Yamada, linux-...@vger.kernel.org, Michal Marek, Nathan Chancellor, Nick Desaulniers, clang-bu...@googlegroups.com, linux-...@vger.kernel.org
the "%.lto.o" rule?
Kees Cook
Kees Cook
Aug 31, 2021, 1:39:18 PM8/31/21
to Masahiro Yamada, linux-...@vger.kernel.org, Michal Marek, Nathan Chancellor, Nick Desaulniers, clang-bu...@googlegroups.com, linux-...@vger.kernel.org
On Tue, Aug 31, 2021 at 04:39:59PM +0900, Masahiro Yamada wrote:
> When Clang LTO is enabled, additional intermediate files *.lto.o are
> created because LLVM bitcode must be converted to ELF before modpost.
>
> For non-LTO builds:
>
> $(LD) $(LD)
> objects ---> <modname>.o -----> <modname>.ko
> |
> <modname>.mod.o ---/
>
> For Clang LTO builds:
>
> $(AR) $(LD) $(LD)
> objects ---> <modname>.o ---> <modname>.lto.o -----> <modname>.ko
> |
> <modname>.mod.o --/
>
> Since the Clang LTO introduction, Kbuild code is complicated due to
> CONFIG_LTO_CLANG conditionals sprinkled everywhere.
>
> Another confusion for Clang LTO builds is, <modname>.o is an archive
> that contains LLVM bitcode files. The suffix should be .a instead of .o
>
> To clean up the code, unify the build process of modules, as follows:
>
> $(AR) $(LD) $(LD)
> objects ---> <modname>.a ---> <modname>.prelink.o -----> <modname>.ko
> |
> <modname>.mod.o ------/
>
> Here, 'objects' are either ELF or LLVM bitcode. <modname>.a is an archive,
> <modname>.prelink.o is ELF.
This is a good diagram and helps me understand what's happening here. Do
> When Clang LTO is enabled, additional intermediate files *.lto.o are
> created because LLVM bitcode must be converted to ELF before modpost.
>
> For non-LTO builds:
>
> $(LD) $(LD)
> objects ---> <modname>.o -----> <modname>.ko
> |
> <modname>.mod.o ---/
>
> For Clang LTO builds:
>
> $(AR) $(LD) $(LD)
> objects ---> <modname>.o ---> <modname>.lto.o -----> <modname>.ko
> |
> <modname>.mod.o --/
>
> Since the Clang LTO introduction, Kbuild code is complicated due to
> CONFIG_LTO_CLANG conditionals sprinkled everywhere.
>
> Another confusion for Clang LTO builds is, <modname>.o is an archive
> that contains LLVM bitcode files. The suffix should be .a instead of .o
>
> To clean up the code, unify the build process of modules, as follows:
>
> $(AR) $(LD) $(LD)
> objects ---> <modname>.a ---> <modname>.prelink.o -----> <modname>.ko
> |
> <modname>.mod.o ------/
>
> Here, 'objects' are either ELF or LLVM bitcode. <modname>.a is an archive,
> <modname>.prelink.o is ELF.
you think there's a place for it somewhere in the kbuild documentation?
>
> Signed-off-by: Masahiro Yamada <masa...@kernel.org>
My question about speed changes also applies to this, since there's now
a new step for non-LTO builds. I think you said it wasn't a meaningful
change in speed, but I think it'd be worth mentioning performance
changes in this commit message.
> ---
>
> scripts/Makefile.build | 100 +++++++++++++++++---------------------
> scripts/Makefile.lib | 11 ++---
> scripts/Makefile.modfinal | 4 +-
> scripts/Makefile.modpost | 7 +--
> scripts/mod/modpost.c | 6 +--
> 5 files changed, 56 insertions(+), 72 deletions(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 3ad1b1227371..cdc09e9080ca 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -88,9 +88,7 @@ endif
>
> targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
>
> -ifdef CONFIG_LTO_CLANG
> -targets-for-modules += $(patsubst %.o, %.lto.o, $(filter %.o, $(obj-m)))
> -endif
> +targets-for-modules += $(patsubst %.o, %.prelink.o, $(filter %.o, $(obj-m)))
>
> ifdef need-modorder
> targets-for-modules += $(obj)/modules.order
> @@ -243,9 +241,12 @@ endif # CONFIG_STACK_VALIDATION
>
> ifdef CONFIG_LTO_CLANG
>
> -# Skip objtool for LLVM bitcode
> +# Skip objtool LLVM bitcode
--
Kees Cook
Nick Desaulniers
Aug 31, 2021, 1:46:38 PM8/31/21
to Masahiro Yamada, linux-...@vger.kernel.org, Michal Marek, Nathan Chancellor, clang-bu...@googlegroups.com, linux-...@vger.kernel.org
On Tue, Aug 31, 2021 at 12:40 AM Masahiro Yamada <masa...@kernel.org> wrote:
>
> When Clang LTO is enabled, additional intermediate files *.lto.o are
> created because LLVM bitcode must be converted to ELF before modpost.
>
> For non-LTO builds:
>
> $(LD) $(LD)
> objects ---> <modname>.o -----> <modname>.ko
> |
> <modname>.mod.o ---/
>
> For Clang LTO builds:
>
> $(AR) $(LD) $(LD)
> objects ---> <modname>.o ---> <modname>.lto.o -----> <modname>.ko
> |
> <modname>.mod.o --/
Is it worth modifying the diagram to note that objects in non-LTO
>
> When Clang LTO is enabled, additional intermediate files *.lto.o are
> created because LLVM bitcode must be converted to ELF before modpost.
>
> For non-LTO builds:
>
> $(LD) $(LD)
> objects ---> <modname>.o -----> <modname>.ko
> |
> <modname>.mod.o ---/
>
> For Clang LTO builds:
>
> $(AR) $(LD) $(LD)
> objects ---> <modname>.o ---> <modname>.lto.o -----> <modname>.ko
> |
> <modname>.mod.o --/
builds are <objects>.o, while for LTO builds, they are <objects>.bc?
If we're not using the .bc file suffix, can we?
>
> Since the Clang LTO introduction, Kbuild code is complicated due to
> CONFIG_LTO_CLANG conditionals sprinkled everywhere.
>
> Another confusion for Clang LTO builds is, <modname>.o is an archive
> that contains LLVM bitcode files. The suffix should be .a instead of .o
>
> To clean up the code, unify the build process of modules, as follows:
>
> $(AR) $(LD) $(LD)
> objects ---> <modname>.a ---> <modname>.prelink.o -----> <modname>.ko
> |
> <modname>.mod.o ------/
> $(obj)/%o: objtool-enabled :=
>
> +# Run objtool now that we have compiled modules into native code
> +$(obj)/%.prelink.o: objtool-enabled := y
> +
> else
>
> # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
> @@ -255,6 +256,8 @@ else
> $(obj)/%o: objtool-enabled = $(if $(filter-out y%, \
> $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y)
>
> +$(obj)/%.prelink.o: objtool-enabled :=
.prelink.o?
Thanks,
~Nick Desaulniers
Masahiro Yamada
Sep 2, 2021, 8:40:06 PM9/2/21
to Kees Cook, Linux Kbuild mailing list, Michal Marek, Nathan Chancellor, Nick Desaulniers, clang-built-linux, Linux Kernel Mailing List
No, it is not intentional.
I will fix "%o" to "%.o"
> (And it later overridden by the "%.lto.o" rule?
While building %.lto.o, we want to set objtool-enabled.
But, we want to cancel it for %.o
--
Best Regards
Masahiro Yamada
Kees Cook
Sep 2, 2021, 9:49:10 PM9/2/21
to Masahiro Yamada, Linux Kbuild mailing list, Michal Marek, Nathan Chancellor, Nick Desaulniers, clang-built-linux, Linux Kernel Mailing List
Reviewed-by: Kees Cook <kees...@chromium.org>
Thanks!
-Kees
>
>
> > (And it later overridden by the "%.lto.o" rule?
>
> No, opposite.
>
> While building %.lto.o, we want to set objtool-enabled.
> But, we want to cancel it for %.o
>
>
>
>
> --
> Best Regards
> Masahiro Yamada
>
> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-li...@googlegroups.com.
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--
Kees Cook
Josh Poimboeuf
Sep 4, 2021, 3:11:37 PM9/4/21
to Masahiro Yamada, linux-...@vger.kernel.org, Michal Marek, Nathan Chancellor, Nick Desaulniers, clang-bu...@googlegroups.com, linux-...@vger.kernel.org
On Tue, Aug 31, 2021 at 04:39:57PM +0900, Masahiro Yamada wrote:
> For CONFIG_LTO_CLANG=y, the objtool processing is not possible at the
> compilation, hence postponed by the link time.
>
> Reuse $(cmd_objtool) for CONFIG_LTO_CLANG=y by defining objtool-enabled
> properly.
>
> For CONFIG_LTO_CLANG=y:
>
> objtool-enabled is off for %.o compilation
> objtool-enabled is on for %.lto link
>
> For CONFIG_LTO_CLANG=n:
>
> objtool-enabled is on for %.o compilation
> (but, it depends on OBJECT_FILE_NON_STANDARD)
>
> Set part-of-module := y for %.lto.o to avoid repeating --module.
>
> Signed-off-by: Masahiro Yamada <masa...@kernel.org>
With Kees' suggested fix:
> compilation, hence postponed by the link time.
>
> Reuse $(cmd_objtool) for CONFIG_LTO_CLANG=y by defining objtool-enabled
> properly.
>
> For CONFIG_LTO_CLANG=y:
>
> objtool-enabled is off for %.o compilation
> objtool-enabled is on for %.lto link
>
> For CONFIG_LTO_CLANG=n:
>
> objtool-enabled is on for %.o compilation
> (but, it depends on OBJECT_FILE_NON_STANDARD)
>
> Set part-of-module := y for %.lto.o to avoid repeating --module.
>
> Signed-off-by: Masahiro Yamada <masa...@kernel.org>
Acked-by: Josh Poimboeuf <jpoi...@redhat.com>
--
Josh
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