[PATCH] kbuild: Fix 'no symbols' warning when CONFIG_TRIM_UNUSD_KSYMS=y

[Masahiro Yamada]

When CONFIG_TRIM_UNUSED_KSYMS is enabled, I see some warnings like this:

nm: arch/x86/entry/vdso/vdso32/note.o: no symbols

$NM (both GNU nm and llvm-nm) warns when no symbol is found in the
object. Suppress the stderr.

Fixes: bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
Signed-off-by: Masahiro Yamada <masa...@kernel.org>
---

scripts/gen_ksymdeps.sh | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/scripts/gen_ksymdeps.sh b/scripts/gen_ksymdeps.sh
index 1324986e1362..5493124e8ee6 100755
--- a/scripts/gen_ksymdeps.sh
+++ b/scripts/gen_ksymdeps.sh
@@ -4,7 +4,10 @@
set -e

# List of exported symbols
-ksyms=$($NM $1 | sed -n 's/.*__ksym_marker_\(.*\)/\1/p' | tr A-Z a-z)
+#
+# If the object has no symbol, $NM warns 'no symbols'.
+# Suppress the stdout.
+ksyms=$($NM $1 2>/dev/null | sed -n 's/.*__ksym_marker_\(.*\)/\1/p' | tr A-Z a-z)

if [ -z "$ksyms" ]; then
exit 0
--
2.30.2

[Nathan Chancellor]

On 8/14/2021 4:41 PM, Masahiro Yamada wrote:
> When CONFIG_TRIM_UNUSED_KSYMS is enabled, I see some warnings like this:
>
> nm: arch/x86/entry/vdso/vdso32/note.o: no symbols
>
> $NM (both GNU nm and llvm-nm) warns when no symbol is found in the
> object. Suppress the stderr.
>
> Fixes: bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
> Signed-off-by: Masahiro Yamada <masa...@kernel.org>

Reviewed-by: Nathan Chancellor <nat...@kernel.org>

[Fāng-ruì Sòng]

On Sat, Aug 14, 2021 at 6:15 PM Nathan Chancellor <nat...@kernel.org> wrote:
>
> On 8/14/2021 4:41 PM, Masahiro Yamada wrote:
> > When CONFIG_TRIM_UNUSED_KSYMS is enabled, I see some warnings like this:
> >
> > nm: arch/x86/entry/vdso/vdso32/note.o: no symbols
> >
> > $NM (both GNU nm and llvm-nm) warns when no symbol is found in the
> > object. Suppress the stderr.
> >
> > Fixes: bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
> > Signed-off-by: Masahiro Yamada <masa...@kernel.org>

LGTM.

FWIW binutils>=2.37 `nm -q` can be used to suppress "no symbols"
https://sourceware.org/bugzilla/show_bug.cgi?id=27408

llvm-nm>=13.0.0 supports -q as well.

> Reviewed-by: Nathan Chancellor <nat...@kernel.org>
>
> > ---
> >
> > scripts/gen_ksymdeps.sh | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/scripts/gen_ksymdeps.sh b/scripts/gen_ksymdeps.sh
> > index 1324986e1362..5493124e8ee6 100755
> > --- a/scripts/gen_ksymdeps.sh
> > +++ b/scripts/gen_ksymdeps.sh
> > @@ -4,7 +4,10 @@
> > set -e
> >
> > # List of exported symbols
> > -ksyms=$($NM $1 | sed -n 's/.*__ksym_marker_\(.*\)/\1/p' | tr A-Z a-z)
> > +#
> > +# If the object has no symbol, $NM warns 'no symbols'.
> > +# Suppress the stdout.
> > +ksyms=$($NM $1 2>/dev/null | sed -n 's/.*__ksym_marker_\(.*\)/\1/p' | tr A-Z a-z)
> >
> > if [ -z "$ksyms" ]; then
> > exit 0
> >
>

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--
宋方睿

[Nicolas Pitre]

You mean stderr.


Nicolas

[Masahiro Yamada]

On Sun, Aug 15, 2021 at 12:18 PM Fāng-ruì Sòng <mas...@google.com> wrote:
>
> On Sat, Aug 14, 2021 at 6:15 PM Nathan Chancellor <nat...@kernel.org> wrote:
> >
> > On 8/14/2021 4:41 PM, Masahiro Yamada wrote:
> > > When CONFIG_TRIM_UNUSED_KSYMS is enabled, I see some warnings like this:
> > >
> > > nm: arch/x86/entry/vdso/vdso32/note.o: no symbols
> > >
> > > $NM (both GNU nm and llvm-nm) warns when no symbol is found in the
> > > object. Suppress the stderr.
> > >
> > > Fixes: bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
> > > Signed-off-by: Masahiro Yamada <masa...@kernel.org>
>
> LGTM.
>
> FWIW binutils>=2.37 `nm -q` can be used to suppress "no symbols"
> https://sourceware.org/bugzilla/show_bug.cgi?id=27408
>
> llvm-nm>=13.0.0 supports -q as well.

Thanks for the info.
Perhaps, I can note the future migration to -q
in a comment.






--
Best Regards
Masahiro Yamada

[Masahiro Yamada]

My bad - I will fix it in v2.
Thanks.

[Masahiro Yamada]

When CONFIG_TRIM_UNUSED_KSYMS is enabled, I see some warnings like this:

nm: arch/x86/entry/vdso/vdso32/note.o: no symbols

$NM (both GNU nm and llvm-nm) warns when no symbol is found in the
object. Suppress the stderr.

Fangrui Song mentioned binutils>=2.37 `nm -q` can be used to suppress
"no symbols" [1], and llvm-nm>=13.0.0 supports -q as well.

We cannot use it for now, but note it as a TODO.

[1]: https://sourceware.org/bugzilla/show_bug.cgi?id=27408

Fixes: bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
Signed-off-by: Masahiro Yamada <masa...@kernel.org>

Reviewed-by: Nathan Chancellor <nat...@kernel.org>
---

Changes in v2:
- Add TODO
- Fix 'stdout' to 'stderr' in the comment

scripts/gen_ksymdeps.sh | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/scripts/gen_ksymdeps.sh b/scripts/gen_ksymdeps.sh
index 1324986e1362..725e8c9c1b53 100755
--- a/scripts/gen_ksymdeps.sh
+++ b/scripts/gen_ksymdeps.sh
@@ -4,7 +4,13 @@

set -e

# List of exported symbols
-ksyms=$($NM $1 | sed -n 's/.*__ksym_marker_\(.*\)/\1/p' | tr A-Z a-z)
+#
+# If the object has no symbol, $NM warns 'no symbols'.

+# Suppress the stderr.
+# TODO:
+# Use -q instead of 2>/dev/null when we upgrade the minimum version of
+# binutils to 2.37, llvm to 13.0.0.

+ksyms=$($NM $1 2>/dev/null | sed -n 's/.*__ksym_marker_\(.*\)/\1/p' | tr A-Z a-z)

if [ -z "$ksyms" ]; then
exit 0
--

2.30.2