[06/14] powerpc/vdso: Remove unused '-s' flag from ASFLAGS

Commit Message

Nathan Chancellor Jan. 4, 2023, 7:54 p.m. UTC

When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
warns that ASFLAGS contains '-s', which is a linking phase option, so it
is unused.

  clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]

Looking at the GAS sources, '-s' is only useful when targeting Solaris
and it is ignored for the powerpc target so just drop the flag
altogether, as it is not needed.

Signed-off-by: Nathan Chancellor <[e-mail]>
---
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
---
 arch/powerpc/kernel/vdso/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Nick Desaulniers Jan. 9, 2023, 9:58 p.m. UTC | #1

On Wed, Jan 4, 2023 at 11:55 AM Nathan Chancellor <[e-mail]> wrote:
>
> When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> warns that ASFLAGS contains '-s', which is a linking phase option, so it
> is unused.
>
>   clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
>
> Looking at the GAS sources, '-s' is only useful when targeting Solaris
> and it is ignored for the powerpc target so just drop the flag
> altogether, as it is not needed.

Do you have any more info where you found this?  I don't see -s
documented as an assembler flag.
https://sourceware.org/binutils/docs/as/PowerPC_002dOpts.html
https://sourceware.org/binutils/docs/as/Invoking.html

The patch seems fine to me, but what was this ever supposed to be?
FWICT it predates git history (looking at
arch/powerpc/kernel/vdso32/Makefile at fc15351d9d63)

Reviewed-by: Nick Desaulniers <[e-mail]>

>
> Signed-off-by: Nathan Chancellor <[e-mail]>
> ---
> Cc: [e-mail]
> Cc: [e-mail]
> Cc: [e-mail]
> Cc: [e-mail]
> ---
>  arch/powerpc/kernel/vdso/Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> index 6a977b0d8ffc..45c0cc5d34b6 100644
> --- a/arch/powerpc/kernel/vdso/Makefile
> +++ b/arch/powerpc/kernel/vdso/Makefile
> @@ -51,10 +51,10 @@ ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
>  ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
>
>  CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> -AS32FLAGS := -D__VDSO32__ -s
> +AS32FLAGS := -D__VDSO32__
>
>  CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
> -AS64FLAGS := -D__VDSO64__ -s
> +AS64FLAGS := -D__VDSO64__
>
>  targets += vdso32.lds
>  CPPFLAGS_vdso32.lds += -P -C -Upowerpc
>
> --
> 2.39.0

Nathan Chancellor Jan. 9, 2023, 10:15 p.m. UTC | #2

On Mon, Jan 09, 2023 at 01:58:32PM -0800, Nick Desaulniers wrote:
> On Wed, Jan 4, 2023 at 11:55 AM Nathan Chancellor <[e-mail]> wrote:
> >
> > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > warns that ASFLAGS contains '-s', which is a linking phase option, so it
> > is unused.
> >
> >   clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
> >
> > Looking at the GAS sources, '-s' is only useful when targeting Solaris
> > and it is ignored for the powerpc target so just drop the flag
> > altogether, as it is not needed.
> 
> Do you have any more info where you found this?  I don't see -s
> documented as an assembler flag.
> https://sourceware.org/binutils/docs/as/PowerPC_002dOpts.html
> https://sourceware.org/binutils/docs/as/Invoking.html

Sure thing, sorry I did not include it initially. See the section from
line 1284 to 1291 or search for "case 's':":

https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gas/config/tc-ppc.c;h=9450fa74de1b61542c9a18babf8c8f621ef904fb;hb=HEAD

> The patch seems fine to me, but what was this ever supposed to be?
> FWICT it predates git history (looking at
> arch/powerpc/kernel/vdso32/Makefile at fc15351d9d63)

Right, I could not figure it out either, it has been there since the
vDSO was introduced back in 2005 (I was three days away from 10!) and
there is no comment about it so *shrug*:

https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=054eb7153aeb84cc92da84210cf93b0e2a34811b

If someone else's archeological skills are better and can provide more
information, I am happy to include that.

> Reviewed-by: Nick Desaulniers <[e-mail]>

Thanks as always for the review! I'll include this and a note about
where in binutils I found that information for v2.

> >
> > Signed-off-by: Nathan Chancellor <[e-mail]>
> > ---
> > Cc: [e-mail]
> > Cc: [e-mail]
> > Cc: [e-mail]
> > Cc: [e-mail]
> > ---
> >  arch/powerpc/kernel/vdso/Makefile | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> > index 6a977b0d8ffc..45c0cc5d34b6 100644
> > --- a/arch/powerpc/kernel/vdso/Makefile
> > +++ b/arch/powerpc/kernel/vdso/Makefile
> > @@ -51,10 +51,10 @@ ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
> >  ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> >
> >  CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> > -AS32FLAGS := -D__VDSO32__ -s
> > +AS32FLAGS := -D__VDSO32__
> >
> >  CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
> > -AS64FLAGS := -D__VDSO64__ -s
> > +AS64FLAGS := -D__VDSO64__
> >
> >  targets += vdso32.lds
> >  CPPFLAGS_vdso32.lds += -P -C -Upowerpc
> >
> > --
> > 2.39.0
> 
> 
> 
> -- 
> Thanks,
> ~Nick Desaulniers

Nick Desaulniers Jan. 9, 2023, 10:21 p.m. UTC | #3

On Mon, Jan 9, 2023 at 2:15 PM Nathan Chancellor <[e-mail]> wrote:
>
> On Mon, Jan 09, 2023 at 01:58:32PM -0800, Nick Desaulniers wrote:
> > On Wed, Jan 4, 2023 at 11:55 AM Nathan Chancellor <[e-mail]> wrote:
> > >
> > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > > warns that ASFLAGS contains '-s', which is a linking phase option, so it
> > > is unused.
> > >
> > >   clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
> > >
> > > Looking at the GAS sources, '-s' is only useful when targeting Solaris
> > > and it is ignored for the powerpc target so just drop the flag
> > > altogether, as it is not needed.
> >
> > Do you have any more info where you found this?  I don't see -s
> > documented as an assembler flag.
> > https://sourceware.org/binutils/docs/as/PowerPC_002dOpts.html
> > https://sourceware.org/binutils/docs/as/Invoking.html
>
> Sure thing, sorry I did not include it initially. See the section from
> line 1284 to 1291 or search for "case 's':":
>
> https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gas/config/tc-ppc.c;h=9450fa74de1b61542c9a18babf8c8f621ef904fb;hb=HEAD
>
> > The patch seems fine to me, but what was this ever supposed to be?
> > FWICT it predates git history (looking at
> > arch/powerpc/kernel/vdso32/Makefile at fc15351d9d63)
>
> Right, I could not figure it out either, it has been there since the
> vDSO was introduced back in 2005 (I was three days away from 10!) and
> there is no comment about it so *shrug*:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=054eb7153aeb84cc92da84210cf93b0e2a34811b
>
> If someone else's archeological skills are better and can provide more
> information, I am happy to include that.
>
> > Reviewed-by: Nick Desaulniers <[e-mail]>
>
> Thanks as always for the review! I'll include this and a note about
> where in binutils I found that information for v2.

Yeah, I think the comment from binutils sources would be good to add
to a v2 commit message. Thanks!

Segher Boessenkool Jan. 9, 2023, 10:23 p.m. UTC | #4

Hi!  Happy new year all.

On Mon, Jan 09, 2023 at 01:58:32PM -0800, Nick Desaulniers wrote:
> On Wed, Jan 4, 2023 at 11:55 AM Nathan Chancellor <[e-mail]> wrote:
> >
> > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > warns that ASFLAGS contains '-s', which is a linking phase option, so it
> > is unused.
> >
> >   clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
> >
> > Looking at the GAS sources, '-s' is only useful when targeting Solaris
> > and it is ignored for the powerpc target so just drop the flag
> > altogether, as it is not needed.
> 
> Do you have any more info where you found this?  I don't see -s
> documented as an assembler flag.
> https://sourceware.org/binutils/docs/as/PowerPC_002dOpts.html
> https://sourceware.org/binutils/docs/as/Invoking.html

It is required by POSIX (for the c99 command, anyway).  It *also* is
required to be supported when producing object files (so when no linking
is done).

It is a GCC flag, and documented just fine:
https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#index-s

(Yes, that says it is for linking; but the option is allowed without
error of any kind always).

(ASFLAGS sounds like it is for assembler commands, but it really is
for compiler commands that just happen to get .S input files).

> The patch seems fine to me, but what was this ever supposed to be?
> FWICT it predates git history (looking at
> arch/powerpc/kernel/vdso32/Makefile at fc15351d9d63)

Yeah, good question.  This compiler flag does the moral equivalent of
strip -s (aka --strip-all).  Maybe this was needed at some point, or
the symbol or debug info was just annoying (during bringup or similar)?

> Reviewed-by: Nick Desaulniers <[e-mail]>
Reviewed-by: Segher Boessenkool <[e-mail]>


Segher

Nathan Chancellor Jan. 9, 2023, 10:37 p.m. UTC | #5

On Mon, Jan 09, 2023 at 04:23:37PM -0600, Segher Boessenkool wrote:
> Hi!  Happy new year all.
> 
> On Mon, Jan 09, 2023 at 01:58:32PM -0800, Nick Desaulniers wrote:
> > On Wed, Jan 4, 2023 at 11:55 AM Nathan Chancellor <[e-mail]> wrote:
> > >
> > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > > warns that ASFLAGS contains '-s', which is a linking phase option, so it
> > > is unused.
> > >
> > >   clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
> > >
> > > Looking at the GAS sources, '-s' is only useful when targeting Solaris
> > > and it is ignored for the powerpc target so just drop the flag
> > > altogether, as it is not needed.
> > 
> > Do you have any more info where you found this?  I don't see -s
> > documented as an assembler flag.
> > https://sourceware.org/binutils/docs/as/PowerPC_002dOpts.html
> > https://sourceware.org/binutils/docs/as/Invoking.html
> 
> It is required by POSIX (for the c99 command, anyway).  It *also* is
> required to be supported when producing object files (so when no linking
> is done).
> 
> It is a GCC flag, and documented just fine:
> https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#index-s
> 
> (Yes, that says it is for linking; but the option is allowed without
> error of any kind always).
> 
> (ASFLAGS sounds like it is for assembler commands, but it really is
> for compiler commands that just happen to get .S input files).
> 
> > The patch seems fine to me, but what was this ever supposed to be?
> > FWICT it predates git history (looking at
> > arch/powerpc/kernel/vdso32/Makefile at fc15351d9d63)
> 
> Yeah, good question.  This compiler flag does the moral equivalent of
> strip -s (aka --strip-all).  Maybe this was needed at some point, or
> the symbol or debug info was just annoying (during bringup or similar)?
> 
> > Reviewed-by: Nick Desaulniers <[e-mail]>
> Reviewed-by: Segher Boessenkool <[e-mail]>

Thank you for the review and extra explanation! I had kind of expanded
on this in the s390 version of this patch [1], I will go ahead and do
the same thing for the powerpc version too.

[1]: https://lore.kernel.org/llvm/[e-mail]/

Cheers,
Nathan

Segher Boessenkool Jan. 9, 2023, 10:47 p.m. UTC | #6

On Mon, Jan 09, 2023 at 03:37:53PM -0700, Nathan Chancellor wrote:
> On Mon, Jan 09, 2023 at 04:23:37PM -0600, Segher Boessenkool wrote:
> > Hi!  Happy new year all.
> > 
> > On Mon, Jan 09, 2023 at 01:58:32PM -0800, Nick Desaulniers wrote:
> > > On Wed, Jan 4, 2023 at 11:55 AM Nathan Chancellor <[e-mail]> wrote:
> > > >
> > > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > > > warns that ASFLAGS contains '-s', which is a linking phase option, so it
> > > > is unused.
> > > >
> > > >   clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
> > > >
> > > > Looking at the GAS sources, '-s' is only useful when targeting Solaris
> > > > and it is ignored for the powerpc target so just drop the flag
> > > > altogether, as it is not needed.
> > > 
> > > Do you have any more info where you found this?  I don't see -s
> > > documented as an assembler flag.
> > > https://sourceware.org/binutils/docs/as/PowerPC_002dOpts.html
> > > https://sourceware.org/binutils/docs/as/Invoking.html
> > 
> > It is required by POSIX (for the c99 command, anyway).  It *also* is
> > required to be supported when producing object files (so when no linking
> > is done).
> > 
> > It is a GCC flag, and documented just fine:
> > https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#index-s
> > 
> > (Yes, that says it is for linking; but the option is allowed without
> > error of any kind always).
> > 
> > (ASFLAGS sounds like it is for assembler commands, but it really is
> > for compiler commands that just happen to get .S input files).
> > 
> > > The patch seems fine to me, but what was this ever supposed to be?
> > > FWICT it predates git history (looking at
> > > arch/powerpc/kernel/vdso32/Makefile at fc15351d9d63)
> > 
> > Yeah, good question.  This compiler flag does the moral equivalent of
> > strip -s (aka --strip-all).  Maybe this was needed at some point, or
> > the symbol or debug info was just annoying (during bringup or similar)?
> > 
> > > Reviewed-by: Nick Desaulniers <[e-mail]>
> > Reviewed-by: Segher Boessenkool <[e-mail]>
> 
> Thank you for the review and extra explanation! I had kind of expanded
> on this in the s390 version of this patch [1], I will go ahead and do
> the same thing for the powerpc version too.
> 
> [1]: https://lore.kernel.org/llvm/[e-mail]/

The underwhelming GCC source code for this is
https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/gcc.cc;h=d629ca5e424ad3120be13e82b9f38b7bf8f1cdf2;hb=HEAD#l1148
which says that the -s flag is passed through unmodified to the linker
when invoking the linker.  See #l603 for the %{s} specs syntax.

This is not a flag to the assembler at all.  It is a flag to the
compiler, which passes it on to the linker :-)

> > (ASFLAGS sounds like it is for assembler commands, but it really is
> > for compiler commands that just happen to get .S input files).


Segher

Nick Desaulniers Jan. 9, 2023, 11:14 p.m. UTC | #7

On Mon, Jan 9, 2023 at 2:29 PM Segher Boessenkool
<[e-mail]> wrote:
>
> Hi!  Happy new year all.

HNY Segher! :)

>
> On Mon, Jan 09, 2023 at 01:58:32PM -0800, Nick Desaulniers wrote:
> > On Wed, Jan 4, 2023 at 11:55 AM Nathan Chancellor <[e-mail]> wrote:
> > >
> > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > > warns that ASFLAGS contains '-s', which is a linking phase option, so it
> > > is unused.
> > >
> > >   clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
> > >
> > > Looking at the GAS sources, '-s' is only useful when targeting Solaris
> > > and it is ignored for the powerpc target so just drop the flag
> > > altogether, as it is not needed.
> >
> > Do you have any more info where you found this?  I don't see -s
> > documented as an assembler flag.
> > https://sourceware.org/binutils/docs/as/PowerPC_002dOpts.html
> > https://sourceware.org/binutils/docs/as/Invoking.html
>
> It is required by POSIX (for the c99 command, anyway).  It *also* is
> required to be supported when producing object files (so when no linking
> is done).
>
> It is a GCC flag, and documented just fine:
> https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#index-s
>
> (Yes, that says it is for linking; but the option is allowed without
> error of any kind always).
>
> (ASFLAGS sounds like it is for assembler commands, but it really is
> for compiler commands that just happen to get .S input files).
>
> > The patch seems fine to me, but what was this ever supposed to be?
> > FWICT it predates git history (looking at
> > arch/powerpc/kernel/vdso32/Makefile at fc15351d9d63)
>
> Yeah, good question.  This compiler flag does the moral equivalent of
> strip -s (aka --strip-all).  Maybe this was needed at some point, or
> the symbol or debug info was just annoying (during bringup or similar)?

Ah right! Ok then, I think we might keep the patch's diff, but update
the commit message to mention this is a linker flag that's unused
since the compiler is being invoked but not the linker (the compiler
is being used as the driver to assemble a single assembler source
without linking it; linking is then driven by the linker in a separate
make rule).

Then we might want to revisit that s390 patch, too?
https://lore.kernel.org/llvm/[e-mail]/

>
> > Reviewed-by: Nick Desaulniers <[e-mail]>
> Reviewed-by: Segher Boessenkool <[e-mail]>
>
>
> Segher

Andreas Schwab Jan. 10, 2023, 12:22 a.m. UTC | #8

On Jan 09 2023, Segher Boessenkool wrote:

> It is required by POSIX (for the c99 command, anyway).  It *also* is
> required to be supported when producing object files (so when no linking
> is done).
>
> It is a GCC flag, and documented just fine:
> https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#index-s

Most assembler flags are unrelated to the flags passed to the compiler
driver, and -s is no exception.  POSIX has nothing to say about the
sub-commands of the compiler anyway.

Segher Boessenkool Jan. 10, 2023, 12:43 a.m. UTC | #9

On Tue, Jan 10, 2023 at 01:22:38AM +0100, Andreas Schwab wrote:
> On Jan 09 2023, Segher Boessenkool wrote:
> 
> > It is required by POSIX (for the c99 command, anyway).  It *also* is
> > required to be supported when producing object files (so when no linking
> > is done).
> >
> > It is a GCC flag, and documented just fine:
> > https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#index-s
> 
> Most assembler flags are unrelated to the flags passed to the compiler
> driver, and -s is no exception.  POSIX has nothing to say about the
> sub-commands of the compiler anyway.

But this is not an assembler flag!

quiet_cmd_vdso32as = VDSO32A $@
      cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<

where

ifdef CROSS32_COMPILE
    VDSOCC := $(CROSS32_COMPILE)gcc
else
    VDSOCC := $(CC)
endif


The name of the make variable AS32FLAGS is a bit misleading.  This
variable does not hold arguments to as, it holds arguments to the
compiler driver, "gcc".


Segher

Nathan Chancellor Jan. 10, 2023, 12:51 a.m. UTC | #10

On Mon, Jan 09, 2023 at 03:14:33PM -0800, Nick Desaulniers wrote:
> On Mon, Jan 9, 2023 at 2:29 PM Segher Boessenkool
> <[e-mail]> wrote:
> >
> > Hi!  Happy new year all.
> 
> HNY Segher! :)
> 
> >
> > On Mon, Jan 09, 2023 at 01:58:32PM -0800, Nick Desaulniers wrote:
> > > On Wed, Jan 4, 2023 at 11:55 AM Nathan Chancellor <[e-mail]> wrote:
> > > >
> > > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > > > warns that ASFLAGS contains '-s', which is a linking phase option, so it
> > > > is unused.
> > > >
> > > >   clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
> > > >
> > > > Looking at the GAS sources, '-s' is only useful when targeting Solaris
> > > > and it is ignored for the powerpc target so just drop the flag
> > > > altogether, as it is not needed.
> > >
> > > Do you have any more info where you found this?  I don't see -s
> > > documented as an assembler flag.
> > > https://sourceware.org/binutils/docs/as/PowerPC_002dOpts.html
> > > https://sourceware.org/binutils/docs/as/Invoking.html
> >
> > It is required by POSIX (for the c99 command, anyway).  It *also* is
> > required to be supported when producing object files (so when no linking
> > is done).
> >
> > It is a GCC flag, and documented just fine:
> > https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#index-s
> >
> > (Yes, that says it is for linking; but the option is allowed without
> > error of any kind always).
> >
> > (ASFLAGS sounds like it is for assembler commands, but it really is
> > for compiler commands that just happen to get .S input files).
> >
> > > The patch seems fine to me, but what was this ever supposed to be?
> > > FWICT it predates git history (looking at
> > > arch/powerpc/kernel/vdso32/Makefile at fc15351d9d63)
> >
> > Yeah, good question.  This compiler flag does the moral equivalent of
> > strip -s (aka --strip-all).  Maybe this was needed at some point, or
> > the symbol or debug info was just annoying (during bringup or similar)?
> 
> Ah right! Ok then, I think we might keep the patch's diff, but update
> the commit message to mention this is a linker flag that's unused
> since the compiler is being invoked but not the linker (the compiler
> is being used as the driver to assemble a single assembler source
> without linking it; linking is then driven by the linker in a separate
> make rule).

Yes, sorry, I thought that was clear with the "which is a linking phase
option" comment in the commit message but clearly not :)

> Then we might want to revisit that s390 patch, too?
> https://lore.kernel.org/llvm/[e-mail]/

So for this patch, I have

  When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
  warns:

    clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]

  The compiler's '-s' flag is a linking option (it is passed along to the
  linker directly), which means it does nothing when the linker is not
  invoked by the compiler. The kernel builds all .o files with either '-c'
  or '-S', which do not run the linker, so '-s' can be safely dropped from
  ASFLAGS.

as a new commit message. Is that sufficient for everyone? If so, I'll
adjust the s390 commit to match, as it is the same exact problem.

Alternatively, if '-s' should actually remain around, we could move it
to ldflags-y, which is added in patch 7. However, I assume that nobody
has noticed that it has not been doing its job for a while, so it should
be safe to remove.

Cheers,
Nathan

Segher Boessenkool Jan. 10, 2023, 11:45 a.m. UTC | #11

On Mon, Jan 09, 2023 at 05:51:23PM -0700, Nathan Chancellor wrote:
> So for this patch, I have
> 
>   When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
>   warns:
> 
>     clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
> 
>   The compiler's '-s' flag is a linking option (it is passed along to the
>   linker directly), which means it does nothing when the linker is not
>   invoked by the compiler. The kernel builds all .o files with either '-c'
>   or '-S', which do not run the linker, so '-s' can be safely dropped from
>   ASFLAGS.
> 
> as a new commit message. Is that sufficient for everyone? If so, I'll
> adjust the s390 commit to match, as it is the same exact problem.

Almost?  -S doesn't write .o files, it writes a .s file.  To go from an
assembler file (.s, or .S if you want to run the C preprocessor on non-C
code for some strange reason, the assembler macro facilities are vastly
superior) to an object file is just -c as well.

> Alternatively, if '-s' should actually remain around, we could move it
> to ldflags-y, which is added in patch 7. However, I assume that nobody
> has noticed that it has not been doing its job for a while, so it should
> be safe to remove.

+1


Segher

Nathan Chancellor Jan. 10, 2023, 3:02 p.m. UTC | #12

On Tue, Jan 10, 2023 at 05:45:23AM -0600, Segher Boessenkool wrote:
> On Mon, Jan 09, 2023 at 05:51:23PM -0700, Nathan Chancellor wrote:
> > So for this patch, I have
> > 
> >   When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> >   warns:
> > 
> >     clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
> > 
> >   The compiler's '-s' flag is a linking option (it is passed along to the
> >   linker directly), which means it does nothing when the linker is not
> >   invoked by the compiler. The kernel builds all .o files with either '-c'
> >   or '-S', which do not run the linker, so '-s' can be safely dropped from
> >   ASFLAGS.
> > 
> > as a new commit message. Is that sufficient for everyone? If so, I'll
> > adjust the s390 commit to match, as it is the same exact problem.
> 
> Almost?  -S doesn't write .o files, it writes a .s file.  To go from an
> assembler file (.s, or .S if you want to run the C preprocessor on non-C
> code for some strange reason, the assembler macro facilities are vastly
> superior) to an object file is just -c as well.

Heh, right, that is what I get for not paying attention and rushing at
the end of my day :) thanks for being pendantic, I will get that ironed
out for v2, which I should have out later today or tomorrow, time
permitting.

Cheers,
Nathan

Patch

diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
index 6a977b0d8ffc..45c0cc5d34b6 100644
--- a/arch/powerpc/kernel/vdso/Makefile
+++ b/arch/powerpc/kernel/vdso/Makefile
@@ -51,10 +51,10 @@  ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
 ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
 
 CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
-AS32FLAGS := -D__VDSO32__ -s
+AS32FLAGS := -D__VDSO32__
 
 CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
-AS64FLAGS := -D__VDSO64__ -s
+AS64FLAGS := -D__VDSO64__
 
 targets += vdso32.lds
 CPPFLAGS_vdso32.lds += -P -C -Upowerpc