diff mbox series

[1/3] Makefile.compiler: s/KBUILD_CFLAGS/KBUILD_AFLAGS/ for as-option

Message ID 20220826181035.859042-2-ndesaulniers@google.com (mailing list archive)
State New, archived
Headers show
Series fix debug info for asm and DEBUG_INFO_SPLIT | expand

Commit Message

Nick Desaulniers Aug. 26, 2022, 6:10 p.m. UTC 
as-instr uses KBUILD_AFLAGS, but as-option uses KBUILD_CFLAGS.  This can
cause as-option to fail unexpectedly because clang will emit
-Werror,-Wunused-command-line-argument for various -m and -f flags for
assembler sources.

Callers of as-option (and as-instr) likely want to be adding flags to
KBUILD_AFLAGS/aflags-y, not KBUILD_CFLAGS/cflags-y.

Link: https://github.com/ClangBuiltLinux/linux/issues/1699
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 arch/x86/boot/compressed/Makefile | 5 +++--
 scripts/Makefile.compiler         | 6 +++---
 2 files changed, 6 insertions(+), 5 deletions(-)

Comments

Nathan Chancellor Aug. 26, 2022, 6:21 p.m. UTC | #1 
Hi Nick,

I think the title would be a little more readable if it was:

Makefile.compiler: Use KBUILD_AFLAGS for as-option

On Fri, Aug 26, 2022 at 11:10:33AM -0700, Nick Desaulniers wrote:
> as-instr uses KBUILD_AFLAGS, but as-option uses KBUILD_CFLAGS.  This can
> cause as-option to fail unexpectedly because clang will emit
> -Werror,-Wunused-command-line-argument for various -m and -f flags for
> assembler sources.
> 
> Callers of as-option (and as-instr) likely want to be adding flags to
> KBUILD_AFLAGS/aflags-y, not KBUILD_CFLAGS/cflags-y.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1699
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
>  arch/x86/boot/compressed/Makefile | 5 +++--
>  scripts/Makefile.compiler         | 6 +++---
>  2 files changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index 35ce1a64068b..fb3db714a028 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -48,8 +48,6 @@ KBUILD_CFLAGS += -Wno-pointer-sign
>  KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
>  KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
>  KBUILD_CFLAGS += -D__DISABLE_EXPORTS
> -# Disable relocation relaxation in case the link is not PIE.
> -KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
>  KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
>  
>  # sev.c indirectly inludes inat-table.h which is generated during
> @@ -58,6 +56,9 @@ KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
>  CFLAGS_sev.o += -I$(objtree)/arch/x86/lib/
>  
>  KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
> +# Disable relocation relaxation in case the link is not PIE.
> +KBUILD_AFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
> +

Commit 09e43968db40 ("x86/boot/compressed: Disable relocation
relaxation") added this to address
https://github.com/ClangBuiltLinux/linux/issues/1121, is it correct to
move it to only being used for the .S files in arch/x86/boot/compressed?

>  GCOV_PROFILE := n
>  UBSAN_SANITIZE :=n
>  
> diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> index 94d0d40cddb3..d1739f0d3ce3 100644
> --- a/scripts/Makefile.compiler
> +++ b/scripts/Makefile.compiler
> @@ -29,13 +29,13 @@ try-run = $(shell set -e;		\
>  	fi)
>  
>  # as-option
> -# Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
> +# Usage: aflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
>  
>  as-option = $(call try-run,\
> -	$(CC) $(KBUILD_CFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))
> +	$(CC) $(KBUILD_AFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))
>  
>  # as-instr
> -# Usage: cflags-y += $(call as-instr,instr,option1,option2)
> +# Usage: aflags-y += $(call as-instr,instr,option1,option2)
>  
>  as-instr = $(call try-run,\
>  	printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))
> -- 
> 2.37.2.672.g94769d06f0-goog
>
Nick Desaulniers Aug. 26, 2022, 6:34 p.m. UTC | #2 
On Fri, Aug 26, 2022 at 11:21 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Nick,
>
> I think the title would be a little more readable if it was:
>
> Makefile.compiler: Use KBUILD_AFLAGS for as-option

Thanks, yeah that looks better; I expect a v2 of this series will be necessary.

>
> On Fri, Aug 26, 2022 at 11:10:33AM -0700, Nick Desaulniers wrote:
> > as-instr uses KBUILD_AFLAGS, but as-option uses KBUILD_CFLAGS.  This can
> > cause as-option to fail unexpectedly because clang will emit
> > -Werror,-Wunused-command-line-argument for various -m and -f flags for
> > assembler sources.
> >
> > Callers of as-option (and as-instr) likely want to be adding flags to
> > KBUILD_AFLAGS/aflags-y, not KBUILD_CFLAGS/cflags-y.
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1699
> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> > ---
> >  arch/x86/boot/compressed/Makefile | 5 +++--
> >  scripts/Makefile.compiler         | 6 +++---
> >  2 files changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> > index 35ce1a64068b..fb3db714a028 100644
> > --- a/arch/x86/boot/compressed/Makefile
> > +++ b/arch/x86/boot/compressed/Makefile
> > @@ -48,8 +48,6 @@ KBUILD_CFLAGS += -Wno-pointer-sign
> >  KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
> >  KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
> >  KBUILD_CFLAGS += -D__DISABLE_EXPORTS
> > -# Disable relocation relaxation in case the link is not PIE.
> > -KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
> >  KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
> >
> >  # sev.c indirectly inludes inat-table.h which is generated during
> > @@ -58,6 +56,9 @@ KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
> >  CFLAGS_sev.o += -I$(objtree)/arch/x86/lib/
> >
> >  KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
> > +# Disable relocation relaxation in case the link is not PIE.
> > +KBUILD_AFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
> > +
>
> Commit 09e43968db40 ("x86/boot/compressed: Disable relocation
> relaxation") added this to address
> https://github.com/ClangBuiltLinux/linux/issues/1121, is it correct to
> move it to only being used for the .S files in arch/x86/boot/compressed?

+ Arvind

Hmm...that makes me think we might need two different as-option flags;
one that does use KBUILD_CFLAGS, and whose result is meant to be added
to cflags-y, then another that uses KBUILD_AFLAGS and is added to
aflagsy-y.

(My patch 2/3 in the series would use the latter)

Let's see what thoughts Masahiro has.

>
> >  GCOV_PROFILE := n
> >  UBSAN_SANITIZE :=n
> >
> > diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> > index 94d0d40cddb3..d1739f0d3ce3 100644
> > --- a/scripts/Makefile.compiler
> > +++ b/scripts/Makefile.compiler
> > @@ -29,13 +29,13 @@ try-run = $(shell set -e;         \
> >       fi)
> >
> >  # as-option
> > -# Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
> > +# Usage: aflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
> >
> >  as-option = $(call try-run,\
> > -     $(CC) $(KBUILD_CFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))
> > +     $(CC) $(KBUILD_AFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))
> >
> >  # as-instr
> > -# Usage: cflags-y += $(call as-instr,instr,option1,option2)
> > +# Usage: aflags-y += $(call as-instr,instr,option1,option2)
> >
> >  as-instr = $(call try-run,\
> >       printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))
> > --
> > 2.37.2.672.g94769d06f0-goog
> >
Masahiro Yamada Aug. 28, 2022, 5:20 p.m. UTC | #3 
On Sat, Aug 27, 2022 at 3:35 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Fri, Aug 26, 2022 at 11:21 AM Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > Hi Nick,
> >
> > I think the title would be a little more readable if it was:
> >
> > Makefile.compiler: Use KBUILD_AFLAGS for as-option
>
> Thanks, yeah that looks better; I expect a v2 of this series will be necessary.
>
> >
> > On Fri, Aug 26, 2022 at 11:10:33AM -0700, Nick Desaulniers wrote:
> > > as-instr uses KBUILD_AFLAGS, but as-option uses KBUILD_CFLAGS.  This can
> > > cause as-option to fail unexpectedly because clang will emit
> > > -Werror,-Wunused-command-line-argument for various -m and -f flags for
> > > assembler sources.
> > >
> > > Callers of as-option (and as-instr) likely want to be adding flags to
> > > KBUILD_AFLAGS/aflags-y, not KBUILD_CFLAGS/cflags-y.

Indeed, it has been weird since the day-1 of as-option.

commit cad8244840d1a148f638925758afd1cdf81fc839
Author: Paul Mundt <lethal@linux-sh.org>
Date:   Mon Jan 16 22:14:19 2006 -0800

    [PATCH] sh: Move CPU subtype configuration to its own Kconfig








> > >
> > > Link: https://github.com/ClangBuiltLinux/linux/issues/1699
> > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> > > ---
> > >  arch/x86/boot/compressed/Makefile | 5 +++--
> > >  scripts/Makefile.compiler         | 6 +++---
> > >  2 files changed, 6 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> > > index 35ce1a64068b..fb3db714a028 100644
> > > --- a/arch/x86/boot/compressed/Makefile
> > > +++ b/arch/x86/boot/compressed/Makefile
> > > @@ -48,8 +48,6 @@ KBUILD_CFLAGS += -Wno-pointer-sign
> > >  KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
> > >  KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
> > >  KBUILD_CFLAGS += -D__DISABLE_EXPORTS
> > > -# Disable relocation relaxation in case the link is not PIE.
> > > -KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
> > >  KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
> > >
> > >  # sev.c indirectly inludes inat-table.h which is generated during
> > > @@ -58,6 +56,9 @@ KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
> > >  CFLAGS_sev.o += -I$(objtree)/arch/x86/lib/
> > >
> > >  KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
> > > +# Disable relocation relaxation in case the link is not PIE.
> > > +KBUILD_AFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
> > > +
> >
> > Commit 09e43968db40 ("x86/boot/compressed: Disable relocation
> > relaxation") added this to address
> > https://github.com/ClangBuiltLinux/linux/issues/1121, is it correct to
> > move it to only being used for the .S files in arch/x86/boot/compressed?

Good catch!


>
> + Arvind
>
> Hmm...that makes me think we might need two different as-option flags;
> one that does use KBUILD_CFLAGS, and whose result is meant to be added
> to cflags-y, then another that uses KBUILD_AFLAGS and is added to
> aflagsy-y.
>
> (My patch 2/3 in the series would use the latter)
>
> Let's see what thoughts Masahiro has.


How about this?

KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)

    to

KBUILD_CFLAGS += $(call cc-option,-Wa$(comma)-mrelax-relocations=no)


You can insert this one-liner before this patch.




In Kconfig, -Wa,<as-option> is tested by cc-option.
(See commit 4d0831e8a029c03f49f434f28b8faef9f0bd403f)





--
Best Regards
Masahiro Yamada
diff mbox series

Patch

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 35ce1a64068b..fb3db714a028 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -48,8 +48,6 @@  KBUILD_CFLAGS += -Wno-pointer-sign
 KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
 KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
 KBUILD_CFLAGS += -D__DISABLE_EXPORTS
-# Disable relocation relaxation in case the link is not PIE.
-KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
 KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
 
 # sev.c indirectly inludes inat-table.h which is generated during
@@ -58,6 +56,9 @@  KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
 CFLAGS_sev.o += -I$(objtree)/arch/x86/lib/
 
 KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
+# Disable relocation relaxation in case the link is not PIE.
+KBUILD_AFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
+
 GCOV_PROFILE := n
 UBSAN_SANITIZE :=n
 
diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index 94d0d40cddb3..d1739f0d3ce3 100644
--- a/scripts/Makefile.compiler
+++ b/scripts/Makefile.compiler
@@ -29,13 +29,13 @@  try-run = $(shell set -e;		\
 	fi)
 
 # as-option
-# Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
+# Usage: aflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
 
 as-option = $(call try-run,\
-	$(CC) $(KBUILD_CFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))
+	$(CC) $(KBUILD_AFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))
 
 # as-instr
-# Usage: cflags-y += $(call as-instr,instr,option1,option2)
+# Usage: aflags-y += $(call as-instr,instr,option1,option2)
 
 as-instr = $(call try-run,\
 	printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))