[PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[Nathan Chancellor]

Hi all,

Clang can emit a few different warnings when it encounters a flag that it
recognizes but does not support internally. These warnings are elevated to
errors within {as,cc}-option via -Werror to catch unsupported flags that should
not be added to KBUILD_{A,C}FLAGS; see commit c3f0d0bc5b01 ("kbuild, LLVMLinux:
Add -Werror to cc-option to support clang").

If an unsupported flag is unconditionally to KBUILD_{A,C}FLAGS, all subsequent
{as,cc}-option will always fail, preventing supported and even potentially
necessary flags from getting adding to the tool flags.

One would expect these warnings to be visible in the kernel build logs since
they are added to KBUILD_{A,C}FLAGS but unfortunately, these warnings are
hidden with clang's -Qunused-arguments flag, which is added to KBUILD_CPPFLAGS
and used for both compiling and assembling files.

Patches 1-4 address the internal inconsistencies of invoking the assembler
within kbuild by using KBUILD_AFLAGS consistently and using '-x
assembler-with-cpp' over '-x assembler'. This matches how assembly files are
built across the kernel and helps avoid problems in situations where macro
definitions or warning flags are present in KBUILD_AFLAGS, which cause
instances of -Wunused-command-line-argument when the preprocessor is not called
to consume them. There were a couple of places in architecture code where this
change would break things so those are fixed first.

Patches 5-12 clean up warnings that will show up when -Qunused-argument is
dropped. I hope none of these are controversial.

Patch 13 turns two warnings into errors so that the presence of unused flags
cannot be easily ignored.

Patch 14 drops -Qunused-argument. This is done last so that it can be easily
reverted if need be.

This series has seen my personal test framework, which tests several different
configurations and architectures, with LLVM tip of tree (16.0.0). I have done
defconfig, allmodconfig, and allnoconfig builds for arm, arm64, i386, mips,
powerpc, riscv, s390, and x86_64 with GCC 12.2.0 as well but I am hoping the
rest of the test infrastructure will catch any lurking problems.

I would like this series to stay together so that there is no opportunity for
breakage so please consider giving acks so that this can be carried via the
kbuild tree (and many thanks to the people who have already provided such
tags).

---
Changes in v2:
- Pick up tags where provided (thank you everyone!)
- Patch 6 and 9: Clarify that '-s' is a compiler flag that is only relevant to
  the linking phase and remove all mention of the assembler's '-s' flag, as the
  assembler is never directly invoked (Nick, Segher)
- Patch 7: Move '-z noexecstack' into new ldflags-y variable (Nick)
- Patch 8: Reword commit message to explain the problem in a clearer manner
  (Nick)
- Link to v1: https://lore.kernel.org/r/20221228-drop-qunused-arguments-v1-0-658cbc8fc592@kernel.org

---
Nathan Chancellor (12):
      MIPS: Always use -Wa,-msoft-float and eliminate GAS_HAS_SET_HARDFLOAT
      MIPS: Prefer cc-option for additions to cflags
      powerpc: Remove linker flag from KBUILD_AFLAGS
      powerpc/vdso: Remove unused '-s' flag from ASFLAGS
      powerpc/vdso: Improve linker flags
      powerpc/vdso: Remove an unsupported flag from vgettimeofday-32.o with clang
      s390/vdso: Drop unused '-s' flag from KBUILD_AFLAGS_64
      s390/vdso: Drop '-shared' from KBUILD_CFLAGS_64
      s390/purgatory: Remove unused '-MD' and unnecessary '-c' flags
      drm/amd/display: Do not add '-mhard-float' to dml_ccflags for clang
      kbuild: Turn a couple more of clang's unused option warnings into errors
      kbuild: Stop using '-Qunused-arguments' with clang

Nick Desaulniers (2):
      x86/boot/compressed: prefer cc-option for CFLAGS additions
      kbuild: Update assembler calls to use proper flags and language target

 Makefile                                    |  1 -
 arch/mips/Makefile                          | 13 ++-------
 arch/mips/include/asm/asmmacro-32.h         |  4 +--
 arch/mips/include/asm/asmmacro.h            | 42 ++++++++++++++---------------
 arch/mips/include/asm/fpregdef.h            | 14 ----------
 arch/mips/include/asm/mipsregs.h            | 20 +++-----------
 arch/mips/kernel/genex.S                    |  2 +-
 arch/mips/kernel/r2300_fpu.S                |  4 +--
 arch/mips/kernel/r4k_fpu.S                  | 12 ++++-----
 arch/mips/kvm/fpu.S                         |  6 ++---
 arch/mips/loongson2ef/Platform              |  2 +-
 arch/powerpc/Makefile                       |  2 +-
 arch/powerpc/kernel/vdso/Makefile           | 25 +++++++++++------
 arch/s390/kernel/vdso64/Makefile            |  4 +--
 arch/s390/purgatory/Makefile                |  2 +-
 arch/x86/boot/compressed/Makefile           |  2 +-
 drivers/gpu/drm/amd/display/dc/dml/Makefile |  3 ++-
 scripts/Kconfig.include                     |  2 +-
 scripts/Makefile.clang                      |  2 ++
 scripts/Makefile.compiler                   |  8 +++---
 scripts/as-version.sh                       |  2 +-
 21 files changed, 74 insertions(+), 98 deletions(-)
---
base-commit: 88603b6dc419445847923fcb7fe5080067a30f98
change-id: 20221228-drop-qunused-arguments-0c5c7dae54fb

Best regards,
-- 
Nathan Chancellor <nathan@kernel.org>

[PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Nathan Chancellor]

When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
points out that KBUILD_AFLAGS contains a linker flag, which will be
used:

  clang: error: -Wl,-a32: 'linker' input unused [-Werror,-Wunused-command-line-argument]

This was likely supposed to be '-Wa,-a$(BITS)'. However, this change is
unnecessary, as all supported versions of clang and gcc will pass '-a64'
or '-a32' to GNU as based on the value of '-m'; the behavior of the
latest stable release of the oldest supported major version of each
compiler is shown below and each compiler's latest release exhibits the
same behavior (GCC 12.2.0 and Clang 15.0.6).

  $ powerpc64-linux-gcc --version | head -1
  powerpc64-linux-gcc (GCC) 5.5.0

  $ powerpc64-linux-gcc -m64 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
  .../as -a64 -mppc64 -many -mbig -o /dev/null /tmp/cctwuBzZ.s

  $ powerpc64-linux-gcc -m32 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
  .../as -a32 -mppc -many -mbig -o /dev/null /tmp/ccaZP4mF.sg

  $ clang --version | head -1
  Ubuntu clang version 11.1.0-++20211011094159+1fdec59bffc1-1~exp1~20211011214622.5

  $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
    -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
   "/usr/bin/powerpc64-linux-gnu-as" "-a64" "-mppc64" "-many" "-o" "/dev/null" "/tmp/null-80267c.s"

  $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
    -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
   "/usr/bin/powerpc64-linux-gnu-as" "-a32" "-mppc" "-many" "-o" "/dev/null" "/tmp/null-ab8f8d.s"

Remove this flag altogether to avoid future issues.

Fixes: 1421dc6d4829 ("powerpc/kbuild: Use flags variables rather than overriding LD/CC/AS")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---
Cc: mpe@ellerman.id.au
Cc: npiggin@gmail.com
Cc: christophe.leroy@csgroup.eu
Cc: linuxppc-dev@lists.ozlabs.org
---
 arch/powerpc/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index dc4cbf0a5ca9..4fd630efe39d 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -90,7 +90,7 @@ aflags-$(CONFIG_CPU_LITTLE_ENDIAN)	+= -mlittle-endian
 
 ifeq ($(HAS_BIARCH),y)
 KBUILD_CFLAGS	+= -m$(BITS)
-KBUILD_AFLAGS	+= -m$(BITS) -Wl,-a$(BITS)
+KBUILD_AFLAGS	+= -m$(BITS)
 KBUILD_LDFLAGS	+= -m elf$(BITS)$(LDEMULATION)
 endif
 

-- 
2.39.0

[PATCH v2 06/14] powerpc/vdso: Remove unused '-s' flag from ASFLAGS

[Nathan Chancellor]

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 '-c', which
stops the compilation pipeline before linking, so '-s' can be safely
dropped from ASFLAGS.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
---
Cc: mpe@ellerman.id.au
Cc: npiggin@gmail.com
Cc: christophe.leroy@csgroup.eu
Cc: linuxppc-dev@lists.ozlabs.org

As I mentioned before, it is possible that we should add '-s' to
ldflags-y in the following patch but I assume someone would have noticed
by now if that was a problem.
---
 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

[PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Nathan Chancellor]

When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
are several warnings in the PowerPC vDSO:

  clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
  clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
  clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]

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

The first group of warnings point out that linker flags were being added
to all invocations of $(CC), even though they will only be used during
the final vDSO link. Move those flags to ldflags-y.

The second group of warnings are compiler or assembler flags that will
be unused during linking. Filter them out from KBUILD_CFLAGS so that
they are not used during linking.

Additionally, '-z noexecstack' was added directly to the ld_and_check
rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
but now that there is a common ldflags variable, it can be moved there.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---
Cc: mpe@ellerman.id.au
Cc: npiggin@gmail.com
Cc: christophe.leroy@csgroup.eu
Cc: linuxppc-dev@lists.ozlabs.org
---
 arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
index 45c0cc5d34b6..4337b3aa9171 100644
--- a/arch/powerpc/kernel/vdso/Makefile
+++ b/arch/powerpc/kernel/vdso/Makefile
@@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
 UBSAN_SANITIZE := n
 KASAN_SANITIZE := n
 
-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
+ccflags-y := -fno-common -fno-builtin
+ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
+ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
+# Filter flags that clang will warn are unused for linking
+ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
+
+CC32FLAGS := -m32
+LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
 AS32FLAGS := -D__VDSO32__
 
-CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
+LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
 AS64FLAGS := -D__VDSO64__
 
 targets += vdso32.lds
@@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
 
 # actual build commands
 quiet_cmd_vdso32ld_and_check = VDSO32L $@
-      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
+      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
 quiet_cmd_vdso32as = VDSO32A $@
       cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
 quiet_cmd_vdso32cc = VDSO32C $@
       cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
 
 quiet_cmd_vdso64ld_and_check = VDSO64L $@
-      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
+      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
 quiet_cmd_vdso64as = VDSO64A $@
       cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $<
 

-- 
2.39.0

[PATCH v2 08/14] powerpc/vdso: Remove an unsupported flag from vgettimeofday-32.o with clang

[Nathan Chancellor]

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

  clang-16: error: argument unused during compilation: '-fno-stack-clash-protection' [-Werror,-Wunused-command-line-argument]

This warning happens because vgettimeofday-32.c gets its base CFLAGS
from the main kernel, which may contain flags that are only supported on
a 64-bit target but not a 32-bit one, which is the case here.
-fstack-clash-protection and its negation are only suppported by the
64-bit powerpc target but that flag is included in an invocation for a
32-bit powerpc target, so clang points out that while the flag is one
that it recognizes, it is not actually used by this compiler job.

To eliminate the warning, remove -fno-stack-clash-protection from
vgettimeofday-32.c's CFLAGS when using clang, as has been done for other
flags previously.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---
Cc: mpe@ellerman.id.au
Cc: npiggin@gmail.com
Cc: christophe.leroy@csgroup.eu
Cc: linuxppc-dev@lists.ozlabs.org
---
 arch/powerpc/kernel/vdso/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
index 4337b3aa9171..e78a57e0a6c0 100644
--- a/arch/powerpc/kernel/vdso/Makefile
+++ b/arch/powerpc/kernel/vdso/Makefile
@@ -16,6 +16,11 @@ ifneq ($(c-gettimeofday-y),)
   CFLAGS_vgettimeofday-32.o += -ffreestanding -fasynchronous-unwind-tables
   CFLAGS_REMOVE_vgettimeofday-32.o = $(CC_FLAGS_FTRACE)
   CFLAGS_REMOVE_vgettimeofday-32.o += -mcmodel=medium -mabi=elfv1 -mabi=elfv2 -mcall-aixdesc
+  # This flag is supported by clang for 64-bit but not 32-bit so it will cause
+  # an unused command line flag warning for this file.
+  ifdef CONFIG_CC_IS_CLANG
+  CFLAGS_REMOVE_vgettimeofday-32.o += -fno-stack-clash-protection
+  endif
   CFLAGS_vgettimeofday-64.o += -include $(c-gettimeofday-y)
   CFLAGS_vgettimeofday-64.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
   CFLAGS_vgettimeofday-64.o += $(call cc-option, -fno-stack-protector)

-- 
2.39.0

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Sedat Dilek]

On Thu, Jan 12, 2023 at 4:06 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> are several warnings in the PowerPC vDSO:
>
>   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
>
>   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
>   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
>
> The first group of warnings point out that linker flags were being added
> to all invocations of $(CC), even though they will only be used during
> the final vDSO link. Move those flags to ldflags-y.
>
> The second group of warnings are compiler or assembler flags that will
> be unused during linking. Filter them out from KBUILD_CFLAGS so that
> they are not used during linking.
>
> Additionally, '-z noexecstack' was added directly to the ld_and_check
> rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
> but now that there is a common ldflags variable, it can be moved there.
>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> Cc: mpe@ellerman.id.au
> Cc: npiggin@gmail.com
> Cc: christophe.leroy@csgroup.eu
> Cc: linuxppc-dev@lists.ozlabs.org
> ---
>  arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> index 45c0cc5d34b6..4337b3aa9171 100644
> --- a/arch/powerpc/kernel/vdso/Makefile
> +++ b/arch/powerpc/kernel/vdso/Makefile
> @@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
>  UBSAN_SANITIZE := n
>  KASAN_SANITIZE := n
>
> -ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
> -ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> -
> -CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> +ccflags-y := -fno-common -fno-builtin
> +ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
> +ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> +# Filter flags that clang will warn are unused for linking
> +ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
> +
> +CC32FLAGS := -m32
> +LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
>  AS32FLAGS := -D__VDSO32__
>
> -CC64FLAGS := -Wl,-soname=linux-vdso64.so.1

Set CC64FLAGS := -m64 ?

> +LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
>  AS64FLAGS := -D__VDSO64__
>
>  targets += vdso32.lds
> @@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
>
>  # actual build commands
>  quiet_cmd_vdso32ld_and_check = VDSO32L $@
> -      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> +      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
>  quiet_cmd_vdso32as = VDSO32A $@
>        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
>  quiet_cmd_vdso32cc = VDSO32C $@
>        cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
>
>  quiet_cmd_vdso64ld_and_check = VDSO64L $@
> -      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> +      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)

If no CC64FLAGS := xxx is set, this can go?

-Sedat-

>  quiet_cmd_vdso64as = VDSO64A $@
>        cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $<
>
>
> --
> 2.39.0
>

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Nathan Chancellor]

Hi Sedat,

On Thu, Jan 12, 2023 at 07:02:30PM +0100, Sedat Dilek wrote:
> On Thu, Jan 12, 2023 at 4:06 AM Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> > are several warnings in the PowerPC vDSO:
> >
> >   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> >
> >   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
> >
> > The first group of warnings point out that linker flags were being added
> > to all invocations of $(CC), even though they will only be used during
> > the final vDSO link. Move those flags to ldflags-y.
> >
> > The second group of warnings are compiler or assembler flags that will
> > be unused during linking. Filter them out from KBUILD_CFLAGS so that
> > they are not used during linking.
> >
> > Additionally, '-z noexecstack' was added directly to the ld_and_check
> > rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
> > but now that there is a common ldflags variable, it can be moved there.
> >
> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > ---
> > Cc: mpe@ellerman.id.au
> > Cc: npiggin@gmail.com
> > Cc: christophe.leroy@csgroup.eu
> > Cc: linuxppc-dev@lists.ozlabs.org
> > ---
> >  arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
> >  1 file changed, 11 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> > index 45c0cc5d34b6..4337b3aa9171 100644
> > --- a/arch/powerpc/kernel/vdso/Makefile
> > +++ b/arch/powerpc/kernel/vdso/Makefile
> > @@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
> >  UBSAN_SANITIZE := n
> >  KASAN_SANITIZE := n
> >
> > -ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
> > -ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > -
> > -CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> > +ccflags-y := -fno-common -fno-builtin
> > +ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
> > +ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > +# Filter flags that clang will warn are unused for linking
> > +ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
> > +
> > +CC32FLAGS := -m32
> > +LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
> >  AS32FLAGS := -D__VDSO32__
> >
> > -CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
> 
> Set CC64FLAGS := -m64 ?

I do not think it is necessary. ldflags-y is filtered from
KBUILD_CFLAGS, which should already include '-m64' (search for
'HAS_BIARCH' in arch/powerpc/Makefile). We would have seen a problem
with this already if a 32-bit target (powerpc-linux-gnu-) CROSS_COMPILE
value since $(c_flags) uses the main kernel's CROSS_COMPILE value.

> > +LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
> >  AS64FLAGS := -D__VDSO64__
> >
> >  targets += vdso32.lds
> > @@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
> >
> >  # actual build commands
> >  quiet_cmd_vdso32ld_and_check = VDSO32L $@
> > -      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > +      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> >  quiet_cmd_vdso32as = VDSO32A $@
> >        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
> >  quiet_cmd_vdso32cc = VDSO32C $@
> >        cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
> >
> >  quiet_cmd_vdso64ld_and_check = VDSO64L $@
> > -      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > +      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> 
> If no CC64FLAGS := xxx is set, this can go?

Good catch! CC64FLAGS can be removed. Masahiro, I am happy to send a v3
when I am back online next week but if you are able to fix it up during
application, please feel free to do so (once the PowerPC folks give
their Acks of course).

> >  quiet_cmd_vdso64as = VDSO64A $@
> >        cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $<
> >
> >
> > --
> > 2.39.0
> >

Thanks for the review, cheers!
Nathan

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Sedat Dilek]

On Thu, Jan 12, 2023 at 7:21 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Sedat,
>
> On Thu, Jan 12, 2023 at 07:02:30PM +0100, Sedat Dilek wrote:
> > On Thu, Jan 12, 2023 at 4:06 AM Nathan Chancellor <nathan@kernel.org> wrote:
> > >
> > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> > > are several warnings in the PowerPC vDSO:
> > >
> > >   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> > >
> > >   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
> > >
> > > The first group of warnings point out that linker flags were being added
> > > to all invocations of $(CC), even though they will only be used during
> > > the final vDSO link. Move those flags to ldflags-y.
> > >
> > > The second group of warnings are compiler or assembler flags that will
> > > be unused during linking. Filter them out from KBUILD_CFLAGS so that
> > > they are not used during linking.
> > >
> > > Additionally, '-z noexecstack' was added directly to the ld_and_check
> > > rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
> > > but now that there is a common ldflags variable, it can be moved there.
> > >
> > > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > > ---
> > > Cc: mpe@ellerman.id.au
> > > Cc: npiggin@gmail.com
> > > Cc: christophe.leroy@csgroup.eu
> > > Cc: linuxppc-dev@lists.ozlabs.org
> > > ---
> > >  arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
> > >  1 file changed, 11 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> > > index 45c0cc5d34b6..4337b3aa9171 100644
> > > --- a/arch/powerpc/kernel/vdso/Makefile
> > > +++ b/arch/powerpc/kernel/vdso/Makefile
> > > @@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
> > >  UBSAN_SANITIZE := n
> > >  KASAN_SANITIZE := n
> > >
> > > -ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
> > > -ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > -
> > > -CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> > > +ccflags-y := -fno-common -fno-builtin
> > > +ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
> > > +ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > +# Filter flags that clang will warn are unused for linking
> > > +ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
> > > +
> > > +CC32FLAGS := -m32
> > > +LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
> > >  AS32FLAGS := -D__VDSO32__
> > >
> > > -CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
> >
> > Set CC64FLAGS := -m64 ?
>
> I do not think it is necessary. ldflags-y is filtered from
> KBUILD_CFLAGS, which should already include '-m64' (search for
> 'HAS_BIARCH' in arch/powerpc/Makefile). We would have seen a problem
> with this already if a 32-bit target (powerpc-linux-gnu-) CROSS_COMPILE
> value since $(c_flags) uses the main kernel's CROSS_COMPILE value.
>

Happy new 2023 Nathan,

that vdso Makefiles are hard to read.

Looks like x86/vdso explicitly sets -m32 and filter-out -m64 for the
32-bit case.

Best regards,
-Sedat-

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/entry/vdso/Makefile

> > > +LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
> > >  AS64FLAGS := -D__VDSO64__
> > >
> > >  targets += vdso32.lds
> > > @@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
> > >
> > >  # actual build commands
> > >  quiet_cmd_vdso32ld_and_check = VDSO32L $@
> > > -      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > +      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> > >  quiet_cmd_vdso32as = VDSO32A $@
> > >        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
> > >  quiet_cmd_vdso32cc = VDSO32C $@
> > >        cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
> > >
> > >  quiet_cmd_vdso64ld_and_check = VDSO64L $@
> > > -      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > +      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> >
> > If no CC64FLAGS := xxx is set, this can go?
>
> Good catch! CC64FLAGS can be removed. Masahiro, I am happy to send a v3
> when I am back online next week but if you are able to fix it up during
> application, please feel free to do so (once the PowerPC folks give
> their Acks of course).
>
> > >  quiet_cmd_vdso64as = VDSO64A $@
> > >        cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $<
> > >
> > >
> > > --
> > > 2.39.0
> > >
>
> Thanks for the review, cheers!
> Nathan

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Masahiro Yamada]

On Fri, Jan 13, 2023 at 3:21 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Sedat,
>
> On Thu, Jan 12, 2023 at 07:02:30PM +0100, Sedat Dilek wrote:
> > On Thu, Jan 12, 2023 at 4:06 AM Nathan Chancellor <nathan@kernel.org> wrote:
> > >
> > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> > > are several warnings in the PowerPC vDSO:
> > >
> > >   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> > >
> > >   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
> > >
> > > The first group of warnings point out that linker flags were being added
> > > to all invocations of $(CC), even though they will only be used during
> > > the final vDSO link. Move those flags to ldflags-y.
> > >
> > > The second group of warnings are compiler or assembler flags that will
> > > be unused during linking. Filter them out from KBUILD_CFLAGS so that
> > > they are not used during linking.
> > >
> > > Additionally, '-z noexecstack' was added directly to the ld_and_check
> > > rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
> > > but now that there is a common ldflags variable, it can be moved there.
> > >
> > > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > > ---
> > > Cc: mpe@ellerman.id.au
> > > Cc: npiggin@gmail.com
> > > Cc: christophe.leroy@csgroup.eu
> > > Cc: linuxppc-dev@lists.ozlabs.org
> > > ---
> > >  arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
> > >  1 file changed, 11 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> > > index 45c0cc5d34b6..4337b3aa9171 100644
> > > --- a/arch/powerpc/kernel/vdso/Makefile
> > > +++ b/arch/powerpc/kernel/vdso/Makefile
> > > @@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
> > >  UBSAN_SANITIZE := n
> > >  KASAN_SANITIZE := n
> > >
> > > -ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
> > > -ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > -
> > > -CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> > > +ccflags-y := -fno-common -fno-builtin
> > > +ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
> > > +ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > +# Filter flags that clang will warn are unused for linking
> > > +ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
> > > +
> > > +CC32FLAGS := -m32
> > > +LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
> > >  AS32FLAGS := -D__VDSO32__
> > >
> > > -CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
> >
> > Set CC64FLAGS := -m64 ?
>
> I do not think it is necessary. ldflags-y is filtered from
> KBUILD_CFLAGS, which should already include '-m64' (search for
> 'HAS_BIARCH' in arch/powerpc/Makefile). We would have seen a problem
> with this already if a 32-bit target (powerpc-linux-gnu-) CROSS_COMPILE
> value since $(c_flags) uses the main kernel's CROSS_COMPILE value.
>
> > > +LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
> > >  AS64FLAGS := -D__VDSO64__
> > >
> > >  targets += vdso32.lds
> > > @@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
> > >
> > >  # actual build commands
> > >  quiet_cmd_vdso32ld_and_check = VDSO32L $@
> > > -      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > +      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> > >  quiet_cmd_vdso32as = VDSO32A $@
> > >        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
> > >  quiet_cmd_vdso32cc = VDSO32C $@
> > >        cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
> > >
> > >  quiet_cmd_vdso64ld_and_check = VDSO64L $@
> > > -      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > +      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> >
> > If no CC64FLAGS := xxx is set, this can go?
>
> Good catch! CC64FLAGS can be removed. Masahiro, I am happy to send a v3
> when I am back online next week but if you are able to fix it up during
> application, please feel free to do so (once the PowerPC folks give
> their Acks of course).




I removed CC64FLAGS locally.




Just two comments.

- Is 7f3d349065d0c643f7f7013fbf9bc9f2c90b675f
  applicable to powerpc too?

  Maybe, as a follow-up cleanup, use $(LD)
  and remove -Wl, prefixes.


- ldflags-y still pulls $(KBUILD_CFLAGS).
  Potentially, a new flag addition to KBUILD_CFLAGS
  may trigger a new -Wunused-command-line-argument warning.

  I hope somebody takes a closer look at which flags
  are really needed for the linker.







> > >  quiet_cmd_vdso64as = VDSO64A $@
> > >        cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $<
> > >
> > >
> > > --
> > > 2.39.0
> > >
>
> Thanks for the review, cheers!
> Nathan



-- 
Best Regards
Masahiro Yamada

Re: [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[Masahiro Yamada]

On Thu, Jan 12, 2023 at 12:05 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi all,
>
> Clang can emit a few different warnings when it encounters a flag that it
> recognizes but does not support internally. These warnings are elevated to
> errors within {as,cc}-option via -Werror to catch unsupported flags that should
> not be added to KBUILD_{A,C}FLAGS; see commit c3f0d0bc5b01 ("kbuild, LLVMLinux:
> Add -Werror to cc-option to support clang").
>
> If an unsupported flag is unconditionally to KBUILD_{A,C}FLAGS, all subsequent
> {as,cc}-option will always fail, preventing supported and even potentially
> necessary flags from getting adding to the tool flags.
>
> One would expect these warnings to be visible in the kernel build logs since
> they are added to KBUILD_{A,C}FLAGS but unfortunately, these warnings are
> hidden with clang's -Qunused-arguments flag, which is added to KBUILD_CPPFLAGS
> and used for both compiling and assembling files.
>
> Patches 1-4 address the internal inconsistencies of invoking the assembler
> within kbuild by using KBUILD_AFLAGS consistently and using '-x
> assembler-with-cpp' over '-x assembler'. This matches how assembly files are
> built across the kernel and helps avoid problems in situations where macro
> definitions or warning flags are present in KBUILD_AFLAGS, which cause
> instances of -Wunused-command-line-argument when the preprocessor is not called
> to consume them. There were a couple of places in architecture code where this
> change would break things so those are fixed first.
>
> Patches 5-12 clean up warnings that will show up when -Qunused-argument is
> dropped. I hope none of these are controversial.
>
> Patch 13 turns two warnings into errors so that the presence of unused flags
> cannot be easily ignored.
>
> Patch 14 drops -Qunused-argument. This is done last so that it can be easily
> reverted if need be.
>
> This series has seen my personal test framework, which tests several different
> configurations and architectures, with LLVM tip of tree (16.0.0). I have done
> defconfig, allmodconfig, and allnoconfig builds for arm, arm64, i386, mips,
> powerpc, riscv, s390, and x86_64 with GCC 12.2.0 as well but I am hoping the
> rest of the test infrastructure will catch any lurking problems.
>
> I would like this series to stay together so that there is no opportunity for
> breakage so please consider giving acks so that this can be carried via the
> kbuild tree (and many thanks to the people who have already provided such
> tags).


All applied to linux-kbuild. Thanks.

I left small comments in 07/14.








> ---
> Changes in v2:
> - Pick up tags where provided (thank you everyone!)
> - Patch 6 and 9: Clarify that '-s' is a compiler flag that is only relevant to
>   the linking phase and remove all mention of the assembler's '-s' flag, as the
>   assembler is never directly invoked (Nick, Segher)
> - Patch 7: Move '-z noexecstack' into new ldflags-y variable (Nick)
> - Patch 8: Reword commit message to explain the problem in a clearer manner
>   (Nick)
> - Link to v1: https://lore.kernel.org/r/20221228-drop-qunused-arguments-v1-0-658cbc8fc592@kernel.org
>
> ---
> Nathan Chancellor (12):
>       MIPS: Always use -Wa,-msoft-float and eliminate GAS_HAS_SET_HARDFLOAT
>       MIPS: Prefer cc-option for additions to cflags
>       powerpc: Remove linker flag from KBUILD_AFLAGS
>       powerpc/vdso: Remove unused '-s' flag from ASFLAGS
>       powerpc/vdso: Improve linker flags
>       powerpc/vdso: Remove an unsupported flag from vgettimeofday-32.o with clang
>       s390/vdso: Drop unused '-s' flag from KBUILD_AFLAGS_64
>       s390/vdso: Drop '-shared' from KBUILD_CFLAGS_64
>       s390/purgatory: Remove unused '-MD' and unnecessary '-c' flags
>       drm/amd/display: Do not add '-mhard-float' to dml_ccflags for clang
>       kbuild: Turn a couple more of clang's unused option warnings into errors
>       kbuild: Stop using '-Qunused-arguments' with clang
>
> Nick Desaulniers (2):
>       x86/boot/compressed: prefer cc-option for CFLAGS additions
>       kbuild: Update assembler calls to use proper flags and language target
>
>  Makefile                                    |  1 -
>  arch/mips/Makefile                          | 13 ++-------
>  arch/mips/include/asm/asmmacro-32.h         |  4 +--
>  arch/mips/include/asm/asmmacro.h            | 42 ++++++++++++++---------------
>  arch/mips/include/asm/fpregdef.h            | 14 ----------
>  arch/mips/include/asm/mipsregs.h            | 20 +++-----------
>  arch/mips/kernel/genex.S                    |  2 +-
>  arch/mips/kernel/r2300_fpu.S                |  4 +--
>  arch/mips/kernel/r4k_fpu.S                  | 12 ++++-----
>  arch/mips/kvm/fpu.S                         |  6 ++---
>  arch/mips/loongson2ef/Platform              |  2 +-
>  arch/powerpc/Makefile                       |  2 +-
>  arch/powerpc/kernel/vdso/Makefile           | 25 +++++++++++------
>  arch/s390/kernel/vdso64/Makefile            |  4 +--
>  arch/s390/purgatory/Makefile                |  2 +-
>  arch/x86/boot/compressed/Makefile           |  2 +-
>  drivers/gpu/drm/amd/display/dc/dml/Makefile |  3 ++-
>  scripts/Kconfig.include                     |  2 +-
>  scripts/Makefile.clang                      |  2 ++
>  scripts/Makefile.compiler                   |  8 +++---
>  scripts/as-version.sh                       |  2 +-
>  21 files changed, 74 insertions(+), 98 deletions(-)
> ---
> base-commit: 88603b6dc419445847923fcb7fe5080067a30f98
> change-id: 20221228-drop-qunused-arguments-0c5c7dae54fb
>
> Best regards,
> --
> Nathan Chancellor <nathan@kernel.org>
>


--
Best Regards
Masahiro Yamada

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Nathan Chancellor]

On Mon, Jan 23, 2023 at 02:27:51AM +0900, Masahiro Yamada wrote:
> On Fri, Jan 13, 2023 at 3:21 AM Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > Hi Sedat,
> >
> > On Thu, Jan 12, 2023 at 07:02:30PM +0100, Sedat Dilek wrote:
> > > On Thu, Jan 12, 2023 at 4:06 AM Nathan Chancellor <nathan@kernel.org> wrote:
> > > >
> > > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> > > > are several warnings in the PowerPC vDSO:
> > > >
> > > >   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > > >   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > > >   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> > > >
> > > >   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
> > > >   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
> > > >
> > > > The first group of warnings point out that linker flags were being added
> > > > to all invocations of $(CC), even though they will only be used during
> > > > the final vDSO link. Move those flags to ldflags-y.
> > > >
> > > > The second group of warnings are compiler or assembler flags that will
> > > > be unused during linking. Filter them out from KBUILD_CFLAGS so that
> > > > they are not used during linking.
> > > >
> > > > Additionally, '-z noexecstack' was added directly to the ld_and_check
> > > > rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
> > > > but now that there is a common ldflags variable, it can be moved there.
> > > >
> > > > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > > > ---
> > > > Cc: mpe@ellerman.id.au
> > > > Cc: npiggin@gmail.com
> > > > Cc: christophe.leroy@csgroup.eu
> > > > Cc: linuxppc-dev@lists.ozlabs.org
> > > > ---
> > > >  arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
> > > >  1 file changed, 11 insertions(+), 7 deletions(-)
> > > >
> > > > diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> > > > index 45c0cc5d34b6..4337b3aa9171 100644
> > > > --- a/arch/powerpc/kernel/vdso/Makefile
> > > > +++ b/arch/powerpc/kernel/vdso/Makefile
> > > > @@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
> > > >  UBSAN_SANITIZE := n
> > > >  KASAN_SANITIZE := n
> > > >
> > > > -ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
> > > > -ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > > -
> > > > -CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> > > > +ccflags-y := -fno-common -fno-builtin
> > > > +ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
> > > > +ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > > +# Filter flags that clang will warn are unused for linking
> > > > +ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
> > > > +
> > > > +CC32FLAGS := -m32
> > > > +LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
> > > >  AS32FLAGS := -D__VDSO32__
> > > >
> > > > -CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
> > >
> > > Set CC64FLAGS := -m64 ?
> >
> > I do not think it is necessary. ldflags-y is filtered from
> > KBUILD_CFLAGS, which should already include '-m64' (search for
> > 'HAS_BIARCH' in arch/powerpc/Makefile). We would have seen a problem
> > with this already if a 32-bit target (powerpc-linux-gnu-) CROSS_COMPILE
> > value since $(c_flags) uses the main kernel's CROSS_COMPILE value.
> >
> > > > +LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
> > > >  AS64FLAGS := -D__VDSO64__
> > > >
> > > >  targets += vdso32.lds
> > > > @@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
> > > >
> > > >  # actual build commands
> > > >  quiet_cmd_vdso32ld_and_check = VDSO32L $@
> > > > -      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > > +      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> > > >  quiet_cmd_vdso32as = VDSO32A $@
> > > >        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
> > > >  quiet_cmd_vdso32cc = VDSO32C $@
> > > >        cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
> > > >
> > > >  quiet_cmd_vdso64ld_and_check = VDSO64L $@
> > > > -      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > > +      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> > >
> > > If no CC64FLAGS := xxx is set, this can go?
> >
> > Good catch! CC64FLAGS can be removed. Masahiro, I am happy to send a v3
> > when I am back online next week but if you are able to fix it up during
> > application, please feel free to do so (once the PowerPC folks give
> > their Acks of course).
> 
> I removed CC64FLAGS locally.

Thank you!

> Just two comments.
> 
> - Is 7f3d349065d0c643f7f7013fbf9bc9f2c90b675f
>   applicable to powerpc too?
> 
>   Maybe, as a follow-up cleanup, use $(LD)
>   and remove -Wl, prefixes.

Yes, that should be possible to do here as well. Nick attempted it some
time ago but there was some complications with older tools, so we
decided to use ld.lld via the compiler in commit 4406b12214f6
("powerpc/vdso: Link with ld.lld when requested").

> - ldflags-y still pulls $(KBUILD_CFLAGS).
>   Potentially, a new flag addition to KBUILD_CFLAGS
>   may trigger a new -Wunused-command-line-argument warning.

Right, this is certainly possible. Hopefully it will not happen
frequently enough to be problematic.

>   I hope somebody takes a closer look at which flags
>   are really needed for the linker.

This is definitely not a bad idea.

Cheers,
Nathan

Re: [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[Naresh Kamboju]

Hi Nathan,

On Thu, 12 Jan 2023 at 08:35, Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi all,
>
> Clang can emit a few different warnings when it encounters a flag that it
> recognizes but does not support internally. These warnings are elevated to
> errors within {as,cc}-option via -Werror to catch unsupported flags that should
> not be added to KBUILD_{A,C}FLAGS; see commit c3f0d0bc5b01 ("kbuild, LLVMLinux:
> Add -Werror to cc-option to support clang").
>
> If an unsupported flag is unconditionally to KBUILD_{A,C}FLAGS, all subsequent
> {as,cc}-option will always fail, preventing supported and even potentially
> necessary flags from getting adding to the tool flags.
>
> One would expect these warnings to be visible in the kernel build logs since
> they are added to KBUILD_{A,C}FLAGS but unfortunately, these warnings are
> hidden with clang's -Qunused-arguments flag, which is added to KBUILD_CPPFLAGS
> and used for both compiling and assembling files.
>
> Patches 1-4 address the internal inconsistencies of invoking the assembler
> within kbuild by using KBUILD_AFLAGS consistently and using '-x
> assembler-with-cpp' over '-x assembler'. This matches how assembly files are
> built across the kernel and helps avoid problems in situations where macro
> definitions or warning flags are present in KBUILD_AFLAGS, which cause
> instances of -Wunused-command-line-argument when the preprocessor is not called
> to consume them. There were a couple of places in architecture code where this
> change would break things so those are fixed first.
>
> Patches 5-12 clean up warnings that will show up when -Qunused-argument is
> dropped. I hope none of these are controversial.
>
> Patch 13 turns two warnings into errors so that the presence of unused flags
> cannot be easily ignored.
>
> Patch 14 drops -Qunused-argument. This is done last so that it can be easily
> reverted if need be.
>
> This series has seen my personal test framework, which tests several different
> configurations and architectures, with LLVM tip of tree (16.0.0). I have done
> defconfig, allmodconfig, and allnoconfig builds for arm, arm64, i386, mips,
> powerpc, riscv, s390, and x86_64 with GCC 12.2.0 as well but I am hoping the
> rest of the test infrastructure will catch any lurking problems.
>
> I would like this series to stay together so that there is no opportunity for
> breakage so please consider giving acks so that this can be carried via the
> kbuild tree (and many thanks to the people who have already provided such
> tags).
>
> ---
> Changes in v2:
> - Pick up tags where provided (thank you everyone!)
> - Patch 6 and 9: Clarify that '-s' is a compiler flag that is only relevant to
>   the linking phase and remove all mention of the assembler's '-s' flag, as the
>   assembler is never directly invoked (Nick, Segher)
> - Patch 7: Move '-z noexecstack' into new ldflags-y variable (Nick)
> - Patch 8: Reword commit message to explain the problem in a clearer manner
>   (Nick)
> - Link to v1: https://lore.kernel.org/r/20221228-drop-qunused-arguments-v1-0-658cbc8fc592@kernel.org
>
> ---
> Nathan Chancellor (12):
>       MIPS: Always use -Wa,-msoft-float and eliminate GAS_HAS_SET_HARDFLOAT
>       MIPS: Prefer cc-option for additions to cflags
>       powerpc: Remove linker flag from KBUILD_AFLAGS
>       powerpc/vdso: Remove unused '-s' flag from ASFLAGS
>       powerpc/vdso: Improve linker flags
>       powerpc/vdso: Remove an unsupported flag from vgettimeofday-32.o with clang
>       s390/vdso: Drop unused '-s' flag from KBUILD_AFLAGS_64
>       s390/vdso: Drop '-shared' from KBUILD_CFLAGS_64
>       s390/purgatory: Remove unused '-MD' and unnecessary '-c' flags
>       drm/amd/display: Do not add '-mhard-float' to dml_ccflags for clang
>       kbuild: Turn a couple more of clang's unused option warnings into errors
>       kbuild: Stop using '-Qunused-arguments' with clang
>
> Nick Desaulniers (2):
>       x86/boot/compressed: prefer cc-option for CFLAGS additions
>       kbuild: Update assembler calls to use proper flags and language target
>
>  Makefile                                    |  1 -
>  arch/mips/Makefile                          | 13 ++-------
>  arch/mips/include/asm/asmmacro-32.h         |  4 +--
>  arch/mips/include/asm/asmmacro.h            | 42 ++++++++++++++---------------
>  arch/mips/include/asm/fpregdef.h            | 14 ----------
>  arch/mips/include/asm/mipsregs.h            | 20 +++-----------
>  arch/mips/kernel/genex.S                    |  2 +-
>  arch/mips/kernel/r2300_fpu.S                |  4 +--
>  arch/mips/kernel/r4k_fpu.S                  | 12 ++++-----
>  arch/mips/kvm/fpu.S                         |  6 ++---
>  arch/mips/loongson2ef/Platform              |  2 +-
>  arch/powerpc/Makefile                       |  2 +-
>  arch/powerpc/kernel/vdso/Makefile           | 25 +++++++++++------
>  arch/s390/kernel/vdso64/Makefile            |  4 +--
>  arch/s390/purgatory/Makefile                |  2 +-
>  arch/x86/boot/compressed/Makefile           |  2 +-
>  drivers/gpu/drm/amd/display/dc/dml/Makefile |  3 ++-
>  scripts/Kconfig.include                     |  2 +-
>  scripts/Makefile.clang                      |  2 ++
>  scripts/Makefile.compiler                   |  8 +++---
>  scripts/as-version.sh                       |  2 +-
>  21 files changed, 74 insertions(+), 98 deletions(-)


FYI,
[ please provide comments, feedback and improvements on build/ ltp smoke tests ]

LKFT test farm have fetched your patch series [1]
[PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS
 [1] https://lore.kernel.org/llvm/20221228-drop-qunused-arguments-v2-0-9adbddd20d86@kernel.org/

Following build warnings and errors reported.

sh:
gcc-11-defconfig — FAIL
gcc-11-shx3_defconfig — FAIL
https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221835/suite/build/tests/

mainline getting passed.
https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-defconfig/history/
https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-shx3_defconfig/history/

Build error:
In function 'follow_pmd_mask',
    inlined from 'follow_pud_mask' at /builds/linux/mm/gup.c:735:9,
    inlined from 'follow_p4d_mask' at /builds/linux/mm/gup.c:752:9,
    inlined from 'follow_page_mask' at /builds/linux/mm/gup.c:809:9:
/builds/linux/include/linux/compiler_types.h:358:45: error: call to
'__compiletime_assert_263' declared with attribute error: Unsupported
access size for {READ,WRITE}_ONCE().
  358 |         _compiletime_assert(condition, msg,
__compiletime_assert_, __COUNTER__)


s390:
clang-15-defconfig — FAIL
https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221913/suite/build/tests/

mainline getting passed.
https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14300495/suite/build/test/clang-15-defconfig/history/

Build error:
make --silent --keep-going --jobs=8
O=/home/tuxbuild/.cache/tuxmake/builds/1/build LLVM_IAS=0 ARCH=s390
CROSS_COMPILE=s390x-linux-gnu- 'HOSTCC=sccache clang' 'CC=sccache
clang'
`.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
defined in discarded section `.exit.text' of fs/fuse/inode.o
`.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
defined in discarded section `.exit.text' of fs/fuse/inode.o
`.exit.text' referenced in section `__bug_table' of crypto/algboss.o:
defined in discarded section `.exit.text' of crypto/algboss.o
`.exit.text' referenced in section `__bug_table' of drivers/scsi/sd.o:
defined in discarded section `.exit.text' of drivers/scsi/sd.o
`.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
defined in discarded section `.exit.text' of drivers/md/md.o
`.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
defined in discarded section `.exit.text' of drivers/md/md.o
`.exit.text' referenced in section `.altinstructions' of
drivers/md/md.o: defined in discarded section `.exit.text' of
drivers/md/md.o
`.exit.text' referenced in section `.altinstructions' of
drivers/md/md.o: defined in discarded section `.exit.text' of
drivers/md/md.o
`.exit.text' referenced in section `.altinstructions' of
net/iucv/iucv.o: defined in discarded section `.exit.text' of
net/iucv/iucv.o
`.exit.text' referenced in section `__bug_table' of
drivers/s390/cio/qdio_thinint.o: defined in discarded section
`.exit.text' of drivers/s390/cio/qdio_thinint.o
`.exit.text' referenced in section `__bug_table' of
drivers/s390/net/qeth_l3_main.o: defined in discarded section
`.exit.text' of drivers/s390/net/qeth_l3_main.o
`.exit.text' referenced in section `__bug_table' of
drivers/s390/net/qeth_l3_main.o: defined in discarded section
`.exit.text' of drivers/s390/net/qeth_l3_main.o
s390x-linux-gnu-ld: BFD (GNU Binutils for Debian) 2.35.2 assertion
fail ../../bfd/elf64-s390.c:3349
make[2]: *** [/builds/linux/scripts/Makefile.vmlinux:34: vmlinux] Error 1

But,
Build and boot pass on arm64, arm, x86_64 and i386.
Build test performed for mips, parisc, riscv, s390, sh, sparc and
powerpc (known build errors for maple_defconfig and cell_defconfig),

Please refer following link for detailed build, boot, LTP smoketest.
https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/?failures_only=false&results_layout=table#!#test-results

Best regards
Naresh Kamboju

--
Linaro LKFT
https://lkft.linaro.org

> ---
> base-commit: 88603b6dc419445847923fcb7fe5080067a30f98
> change-id: 20221228-drop-qunused-arguments-0c5c7dae54fb
>
> Best regards,
> --
> Nathan Chancellor <nathan@kernel.org>
>
>

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Segher Boessenkool]

Hi!

On Wed, Jan 11, 2023 at 08:05:04PM -0700, Nathan Chancellor wrote:
> When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> are several warnings in the PowerPC vDSO:
> 
>   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> 
>   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
>   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]

There is nothing wrong with the warnings, but as usual, -Werror is very
counterproductive.

> The first group of warnings point out that linker flags were being added
> to all invocations of $(CC), even though they will only be used during
> the final vDSO link. Move those flags to ldflags-y.

Which is explicitly allowed, and won't do anything, so nothing harmful
either.  It is not a bad idea to avoid this if that is trivial to do,
of course.

> The second group of warnings are compiler or assembler flags that will
> be unused during linking. Filter them out from KBUILD_CFLAGS so that
> they are not used during linking.

And here it is even more obviously fine.  If you need obfuscation like
in your patch, it is better not to do this imo.

The warning text "linker input unused" is misleading btw.  It would be
good to warn about that, if it was true: very likely the user didn't
intend what he wrote.  But a linker input is an object file, or perhaps
a linker script.  These things are just compiler flags.


Segher

Re: [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[Nathan Chancellor]

Hi Naresh,

On Mon, Jan 23, 2023 at 07:28:10PM +0530, Naresh Kamboju wrote:
> FYI,
> [ please provide comments, feedback and improvements on build/ ltp smoke tests ]
> 
> LKFT test farm have fetched your patch series [1]
> [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS
>  [1] https://lore.kernel.org/llvm/20221228-drop-qunused-arguments-v2-0-9adbddd20d86@kernel.org/

Thank you a lot for testing this series, it is much appreciated!

It looks like this was applied on top of 6.2-rc3 if I am reading your
logs right but your mainline testing is recent, 6.2-rc5. I think the
errors you are seeing here are just existing mainline regressions that
were later fixed.

> Following build warnings and errors reported.
> 
> sh:
> gcc-11-defconfig — FAIL
> gcc-11-shx3_defconfig — FAIL
> https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221835/suite/build/tests/
> 
> mainline getting passed.
> https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-defconfig/history/
> https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-shx3_defconfig/history/
> 
> Build error:
> In function 'follow_pmd_mask',
>     inlined from 'follow_pud_mask' at /builds/linux/mm/gup.c:735:9,
>     inlined from 'follow_p4d_mask' at /builds/linux/mm/gup.c:752:9,
>     inlined from 'follow_page_mask' at /builds/linux/mm/gup.c:809:9:
> /builds/linux/include/linux/compiler_types.h:358:45: error: call to
> '__compiletime_assert_263' declared with attribute error: Unsupported
> access size for {READ,WRITE}_ONCE().
>   358 |         _compiletime_assert(condition, msg,
> __compiletime_assert_, __COUNTER__)

I think this was fixed with mainline commit 526970be53d5 ("sh/mm: Fix
pmd_t for real"), released in 6.2-rc4. You can see a previous build
failing in the same manner:

https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc3-9-g5a41237ad1d4/testrun/14056384/suite/build/tests/

> s390:
> clang-15-defconfig — FAIL
> https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221913/suite/build/tests/
> 
> mainline getting passed.
> https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14300495/suite/build/test/clang-15-defconfig/history/
> 
> Build error:
> make --silent --keep-going --jobs=8
> O=/home/tuxbuild/.cache/tuxmake/builds/1/build LLVM_IAS=0 ARCH=s390
> CROSS_COMPILE=s390x-linux-gnu- 'HOSTCC=sccache clang' 'CC=sccache
> clang'
> `.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
> defined in discarded section `.exit.text' of fs/fuse/inode.o
> `.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
> defined in discarded section `.exit.text' of fs/fuse/inode.o
> `.exit.text' referenced in section `__bug_table' of crypto/algboss.o:
> defined in discarded section `.exit.text' of crypto/algboss.o
> `.exit.text' referenced in section `__bug_table' of drivers/scsi/sd.o:
> defined in discarded section `.exit.text' of drivers/scsi/sd.o
> `.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
> defined in discarded section `.exit.text' of drivers/md/md.o
> `.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
> defined in discarded section `.exit.text' of drivers/md/md.o
> `.exit.text' referenced in section `.altinstructions' of
> drivers/md/md.o: defined in discarded section `.exit.text' of
> drivers/md/md.o
> `.exit.text' referenced in section `.altinstructions' of
> drivers/md/md.o: defined in discarded section `.exit.text' of
> drivers/md/md.o
> `.exit.text' referenced in section `.altinstructions' of
> net/iucv/iucv.o: defined in discarded section `.exit.text' of
> net/iucv/iucv.o
> `.exit.text' referenced in section `__bug_table' of
> drivers/s390/cio/qdio_thinint.o: defined in discarded section
> `.exit.text' of drivers/s390/cio/qdio_thinint.o
> `.exit.text' referenced in section `__bug_table' of
> drivers/s390/net/qeth_l3_main.o: defined in discarded section
> `.exit.text' of drivers/s390/net/qeth_l3_main.o
> `.exit.text' referenced in section `__bug_table' of
> drivers/s390/net/qeth_l3_main.o: defined in discarded section
> `.exit.text' of drivers/s390/net/qeth_l3_main.o
> s390x-linux-gnu-ld: BFD (GNU Binutils for Debian) 2.35.2 assertion
> fail ../../bfd/elf64-s390.c:3349
> make[2]: *** [/builds/linux/scripts/Makefile.vmlinux:34: vmlinux] Error 1

This should be fixed with mainline commit a494398bde27 ("s390: define
RUNTIME_DISCARD_EXIT to fix link error with GNU ld < 2.36"), released in
6.2-rc4 as well. Same as before, visible in mainline at one point
without this series:

https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc3-9-g5a41237ad1d4/testrun/14057142/suite/build/tests/

> But,
> Build and boot pass on arm64, arm, x86_64 and i386.
> Build test performed for mips, parisc, riscv, s390, sh, sparc and
> powerpc (known build errors for maple_defconfig and cell_defconfig),

Good to hear!

Please consider retesting this series on top of 6.2-rc5 or testing the
current kbuild tree, which has this series applied in it:

https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/log/?h=for-next

Cheers,
Nathan

Re: [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[Naresh Kamboju]

Hi Nathan,

On Mon, 23 Jan 2023 at 21:41, Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Naresh,
>
> On Mon, Jan 23, 2023 at 07:28:10PM +0530, Naresh Kamboju wrote:
> > FYI,
> > [ please provide comments, feedback and improvements on build/ ltp smoke tests ]
> >
> > LKFT test farm have fetched your patch series [1]
> > [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS
> >  [1] https://lore.kernel.org/llvm/20221228-drop-qunused-arguments-v2-0-9adbddd20d86@kernel.org/
>
> Thank you a lot for testing this series, it is much appreciated!
>
> It looks like this was applied on top of 6.2-rc3 if I am reading your
> logs right but your mainline testing is recent, 6.2-rc5. I think the
> errors you are seeing here are just existing mainline regressions that
> were later fixed.
>
> > Following build warnings and errors reported.
> >
> > sh:
> > gcc-11-defconfig — FAIL
> > gcc-11-shx3_defconfig — FAIL
> > https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221835/suite/build/tests/
> >
> > mainline getting passed.
> > https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-defconfig/history/
> > https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-shx3_defconfig/history/
> >
> > Build error:
> > In function 'follow_pmd_mask',
> >     inlined from 'follow_pud_mask' at /builds/linux/mm/gup.c:735:9,
> >     inlined from 'follow_p4d_mask' at /builds/linux/mm/gup.c:752:9,
> >     inlined from 'follow_page_mask' at /builds/linux/mm/gup.c:809:9:
> > /builds/linux/include/linux/compiler_types.h:358:45: error: call to
> > '__compiletime_assert_263' declared with attribute error: Unsupported
> > access size for {READ,WRITE}_ONCE().
> >   358 |         _compiletime_assert(condition, msg,
> > __compiletime_assert_, __COUNTER__)
>
> I think this was fixed with mainline commit 526970be53d5 ("sh/mm: Fix
> pmd_t for real"), released in 6.2-rc4. You can see a previous build
> failing in the same manner:
>
> https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc3-9-g5a41237ad1d4/testrun/14056384/suite/build/tests/
>
> > s390:
> > clang-15-defconfig — FAIL
> > https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221913/suite/build/tests/
> >
> > mainline getting passed.
> > https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14300495/suite/build/test/clang-15-defconfig/history/
> >
> > Build error:
> > make --silent --keep-going --jobs=8
> > O=/home/tuxbuild/.cache/tuxmake/builds/1/build LLVM_IAS=0 ARCH=s390
> > CROSS_COMPILE=s390x-linux-gnu- 'HOSTCC=sccache clang' 'CC=sccache
> > clang'
> > `.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
> > defined in discarded section `.exit.text' of fs/fuse/inode.o
> > `.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
> > defined in discarded section `.exit.text' of fs/fuse/inode.o
> > `.exit.text' referenced in section `__bug_table' of crypto/algboss.o:
> > defined in discarded section `.exit.text' of crypto/algboss.o
> > `.exit.text' referenced in section `__bug_table' of drivers/scsi/sd.o:
> > defined in discarded section `.exit.text' of drivers/scsi/sd.o
> > `.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
> > defined in discarded section `.exit.text' of drivers/md/md.o
> > `.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
> > defined in discarded section `.exit.text' of drivers/md/md.o
> > `.exit.text' referenced in section `.altinstructions' of
> > drivers/md/md.o: defined in discarded section `.exit.text' of
> > drivers/md/md.o
> > `.exit.text' referenced in section `.altinstructions' of
> > drivers/md/md.o: defined in discarded section `.exit.text' of
> > drivers/md/md.o
> > `.exit.text' referenced in section `.altinstructions' of
> > net/iucv/iucv.o: defined in discarded section `.exit.text' of
> > net/iucv/iucv.o
> > `.exit.text' referenced in section `__bug_table' of
> > drivers/s390/cio/qdio_thinint.o: defined in discarded section
> > `.exit.text' of drivers/s390/cio/qdio_thinint.o
> > `.exit.text' referenced in section `__bug_table' of
> > drivers/s390/net/qeth_l3_main.o: defined in discarded section
> > `.exit.text' of drivers/s390/net/qeth_l3_main.o
> > `.exit.text' referenced in section `__bug_table' of
> > drivers/s390/net/qeth_l3_main.o: defined in discarded section
> > `.exit.text' of drivers/s390/net/qeth_l3_main.o
> > s390x-linux-gnu-ld: BFD (GNU Binutils for Debian) 2.35.2 assertion
> > fail ../../bfd/elf64-s390.c:3349
> > make[2]: *** [/builds/linux/scripts/Makefile.vmlinux:34: vmlinux] Error 1
>
> This should be fixed with mainline commit a494398bde27 ("s390: define
> RUNTIME_DISCARD_EXIT to fix link error with GNU ld < 2.36"), released in
> 6.2-rc4 as well. Same as before, visible in mainline at one point
> without this series:
>
> https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc3-9-g5a41237ad1d4/testrun/14057142/suite/build/tests/
>
> > But,
> > Build and boot pass on arm64, arm, x86_64 and i386.
> > Build test performed for mips, parisc, riscv, s390, sh, sparc and
> > powerpc (known build errors for maple_defconfig and cell_defconfig),
>
> Good to hear!
>
> Please consider retesting this series on top of 6.2-rc5 or testing the
> current kbuild tree, which has this series applied in it:

This is the perfect place to test.

> https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/log/?h=for-next

Build test pass on arm, arm64, i386, mips, parisc, powerpc, riscv, s390, sh,
sparc and x86_64.
Boot and LTP smoke pass on qemu-arm64, qemu-armv7, qemu-i386 and qemu-x86_64.

  Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
  Tested-by: Anders Roxell <anders.roxell@linaro.org>

Please refer to the following link for details of testing.
  https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/linux-kbuild_masahiroy-branch-kbuild-20230124/?failures_only=false&results_layout=table#!#test-results

metadata:
  git_describe : v6.2-rc5-46-ga778c9dd138b
  git_repo : https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git
  git_sha : a778c9dd138b4f4410779705b444d58ce6f8fc44
  git_short_log : a778c9dd138b ("builddeb: clean generated package content")

--
Linaro LKFT
https://lkft.linaro.org

>
> Cheers,
> Nathan

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Nathan Chancellor]

On Mon, Jan 23, 2023 at 09:07:16AM -0600, Segher Boessenkool wrote:
> Hi!
> 
> On Wed, Jan 11, 2023 at 08:05:04PM -0700, Nathan Chancellor wrote:
> > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> > are several warnings in the PowerPC vDSO:
> > 
> >   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> > 
> >   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
> 
> There is nothing wrong with the warnings, but as usual, -Werror is very
> counterproductive.
> 
> > The first group of warnings point out that linker flags were being added
> > to all invocations of $(CC), even though they will only be used during
> > the final vDSO link. Move those flags to ldflags-y.
> 
> Which is explicitly allowed, and won't do anything, so nothing harmful
> either.  It is not a bad idea to avoid this if that is trivial to do,
> of course.

I think this patch shows that it is trivial to do this, the primary core
of the diff is only a few lines.

> > The second group of warnings are compiler or assembler flags that will
> > be unused during linking. Filter them out from KBUILD_CFLAGS so that
> > they are not used during linking.
> 
> And here it is even more obviously fine.  If you need obfuscation like
> in your patch, it is better not to do this imo.

I do not think this patch really obfuscates anything? The filtering is
pretty clear to me.

If this is a real objection to the patch, I suppose we could just
localize '-Qunused-arguments' to this Makefile and be done with it but I
do not think this change is a bad solution to the problem either.

Cheers,
Nathan

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Segher Boessenkool]

On Tue, Jan 24, 2023 at 09:14:52AM -0700, Nathan Chancellor wrote:
> On Mon, Jan 23, 2023 at 09:07:16AM -0600, Segher Boessenkool wrote:
> > And here it is even more obviously fine.  If you need obfuscation like
> > in your patch, it is better not to do this imo.
> 
> I do not think this patch really obfuscates anything? The filtering is
> pretty clear to me.

And not having such filtering is more obvious and more clear.

It doesn't matter much for just this patch of course, but it will make
the code significantly harder to read (and deal with in other ways) if
this continues.

> If this is a real objection to the patch, I suppose we could just
> localize '-Qunused-arguments' to this Makefile and be done with it but I
> do not think this change is a bad solution to the problem either.

It is a comment about the direction this patch is moving us in.  I don't
think it is a good idea at all to try to avoid all warnings, and even
more so it is a bad idea to make objectively worse source code just to
appease a trigger-happy and questionable warning.

As I said, you can often avoid warnings by writing better code, like
part of the patch did.  That is a good reaction to warnings.  Making
worse code to avoid warnings is not a good idea normally.

Just don't use -Werror by default, and don't make other people suffer
its yoke!


Segher

Re: [PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Michael Ellerman]

Nathan Chancellor <nathan@kernel.org> writes:
> When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> points out that KBUILD_AFLAGS contains a linker flag, which will be
> used:

Should that say "unused" ?

>   clang: error: -Wl,-a32: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>
> This was likely supposed to be '-Wa,-a$(BITS)'. However, this change is
> unnecessary, as all supported versions of clang and gcc will pass '-a64'
> or '-a32' to GNU as based on the value of '-m'; the behavior of the
> latest stable release of the oldest supported major version of each
> compiler is shown below and each compiler's latest release exhibits the
> same behavior (GCC 12.2.0 and Clang 15.0.6).
>
>   $ powerpc64-linux-gcc --version | head -1
>   powerpc64-linux-gcc (GCC) 5.5.0
>
>   $ powerpc64-linux-gcc -m64 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
>   .../as -a64 -mppc64 -many -mbig -o /dev/null /tmp/cctwuBzZ.s
>
>   $ powerpc64-linux-gcc -m32 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
>   .../as -a32 -mppc -many -mbig -o /dev/null /tmp/ccaZP4mF.sg
>
>   $ clang --version | head -1
>   Ubuntu clang version 11.1.0-++20211011094159+1fdec59bffc1-1~exp1~20211011214622.5
>
>   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
>     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
>    "/usr/bin/powerpc64-linux-gnu-as" "-a64" "-mppc64" "-many" "-o" "/dev/null" "/tmp/null-80267c.s"
>
>   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
>     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
>    "/usr/bin/powerpc64-linux-gnu-as" "-a32" "-mppc" "-many" "-o" "/dev/null" "/tmp/null-ab8f8d.s"
>
> Remove this flag altogether to avoid future issues.
>
> Fixes: 1421dc6d4829 ("powerpc/kbuild: Use flags variables rather than overriding LD/CC/AS")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> Cc: mpe@ellerman.id.au

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers

Re: [PATCH v2 06/14] powerpc/vdso: Remove unused '-s' flag from ASFLAGS

[Michael Ellerman]

Nathan Chancellor <nathan@kernel.org> writes:
> 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 '-c', which
> stops the compilation pipeline before linking, so '-s' can be safely
> dropped from ASFLAGS.
>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
> ---
> Cc: mpe@ellerman.id.au

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers

Re: [PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Masahiro Yamada]

On Wed, Jan 25, 2023 at 1:11 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
>
> Nathan Chancellor <nathan@kernel.org> writes:
> > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > points out that KBUILD_AFLAGS contains a linker flag, which will be
> > used:
>
> Should that say "unused" ?



Nathan, shall I fix it up locally?
(it will change the commit hash, though.)





>
> >   clang: error: -Wl,-a32: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> >
> > This was likely supposed to be '-Wa,-a$(BITS)'. However, this change is
> > unnecessary, as all supported versions of clang and gcc will pass '-a64'
> > or '-a32' to GNU as based on the value of '-m'; the behavior of the
> > latest stable release of the oldest supported major version of each
> > compiler is shown below and each compiler's latest release exhibits the
> > same behavior (GCC 12.2.0 and Clang 15.0.6).
> >
> >   $ powerpc64-linux-gcc --version | head -1
> >   powerpc64-linux-gcc (GCC) 5.5.0
> >
> >   $ powerpc64-linux-gcc -m64 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
> >   .../as -a64 -mppc64 -many -mbig -o /dev/null /tmp/cctwuBzZ.s
> >
> >   $ powerpc64-linux-gcc -m32 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
> >   .../as -a32 -mppc -many -mbig -o /dev/null /tmp/ccaZP4mF.sg
> >
> >   $ clang --version | head -1
> >   Ubuntu clang version 11.1.0-++20211011094159+1fdec59bffc1-1~exp1~20211011214622.5
> >
> >   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
> >     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
> >    "/usr/bin/powerpc64-linux-gnu-as" "-a64" "-mppc64" "-many" "-o" "/dev/null" "/tmp/null-80267c.s"
> >
> >   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
> >     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
> >    "/usr/bin/powerpc64-linux-gnu-as" "-a32" "-mppc" "-many" "-o" "/dev/null" "/tmp/null-ab8f8d.s"
> >
> > Remove this flag altogether to avoid future issues.
> >
> > Fixes: 1421dc6d4829 ("powerpc/kbuild: Use flags variables rather than overriding LD/CC/AS")
> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > ---
> > Cc: mpe@ellerman.id.au
>
> Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
>
> cheers



-- 
Best Regards
Masahiro Yamada

Re: [PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Nathan Chancellor]

On Thu, Jan 26, 2023 at 10:29:54AM +0900, Masahiro Yamada wrote:
> On Wed, Jan 25, 2023 at 1:11 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
> >
> > Nathan Chancellor <nathan@kernel.org> writes:
> > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > > points out that KBUILD_AFLAGS contains a linker flag, which will be
> > > used:
> >
> > Should that say "unused" ?
> 
> 
> 
> Nathan, shall I fix it up locally?
> (it will change the commit hash, though.)

Yes please, if you would not mind. Sorry about that and thank you for
spotting it Michael!

Since you have to rebase to fix it, you can include Michael's acks?

Cheers,
Nathan

> > >   clang: error: -Wl,-a32: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > >
> > > This was likely supposed to be '-Wa,-a$(BITS)'. However, this change is
> > > unnecessary, as all supported versions of clang and gcc will pass '-a64'
> > > or '-a32' to GNU as based on the value of '-m'; the behavior of the
> > > latest stable release of the oldest supported major version of each
> > > compiler is shown below and each compiler's latest release exhibits the
> > > same behavior (GCC 12.2.0 and Clang 15.0.6).
> > >
> > >   $ powerpc64-linux-gcc --version | head -1
> > >   powerpc64-linux-gcc (GCC) 5.5.0
> > >
> > >   $ powerpc64-linux-gcc -m64 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
> > >   .../as -a64 -mppc64 -many -mbig -o /dev/null /tmp/cctwuBzZ.s
> > >
> > >   $ powerpc64-linux-gcc -m32 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
> > >   .../as -a32 -mppc -many -mbig -o /dev/null /tmp/ccaZP4mF.sg
> > >
> > >   $ clang --version | head -1
> > >   Ubuntu clang version 11.1.0-++20211011094159+1fdec59bffc1-1~exp1~20211011214622.5
> > >
> > >   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
> > >     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
> > >    "/usr/bin/powerpc64-linux-gnu-as" "-a64" "-mppc64" "-many" "-o" "/dev/null" "/tmp/null-80267c.s"
> > >
> > >   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
> > >     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
> > >    "/usr/bin/powerpc64-linux-gnu-as" "-a32" "-mppc" "-many" "-o" "/dev/null" "/tmp/null-ab8f8d.s"
> > >
> > > Remove this flag altogether to avoid future issues.
> > >
> > > Fixes: 1421dc6d4829 ("powerpc/kbuild: Use flags variables rather than overriding LD/CC/AS")
> > > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > > ---
> > > Cc: mpe@ellerman.id.au
> >
> > Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
> >
> > cheers
> 
> 
> 
> -- 
> Best Regards
> Masahiro Yamada

Re: [PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Masahiro Yamada]

On Thu, Jan 26, 2023 at 11:07 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> On Thu, Jan 26, 2023 at 10:29:54AM +0900, Masahiro Yamada wrote:
> > On Wed, Jan 25, 2023 at 1:11 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
> > >
> > > Nathan Chancellor <nathan@kernel.org> writes:
> > > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > > > points out that KBUILD_AFLAGS contains a linker flag, which will be
> > > > used:
> > >
> > > Should that say "unused" ?
> >
> >
> >
> > Nathan, shall I fix it up locally?
> > (it will change the commit hash, though.)
>
> Yes please, if you would not mind. Sorry about that and thank you for
> spotting it Michael!
>
> Since you have to rebase to fix it, you can include Michael's acks?
>
> Cheers,
> Nathan



Done.








-- 
Best Regards
Masahiro Yamada

Re: [PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Michael Ellerman]

Masahiro Yamada <masahiroy@kernel.org> writes:
> On Thu, Jan 26, 2023 at 11:07 AM Nathan Chancellor <nathan@kernel.org> wrote:
>>
>> On Thu, Jan 26, 2023 at 10:29:54AM +0900, Masahiro Yamada wrote:
>> > On Wed, Jan 25, 2023 at 1:11 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
>> > >
>> > > Nathan Chancellor <nathan@kernel.org> writes:
>> > > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
>> > > > points out that KBUILD_AFLAGS contains a linker flag, which will be
>> > > > used:
>> > >
>> > > Should that say "unused" ?
>> >
>> >
>> >
>> > Nathan, shall I fix it up locally?
>> > (it will change the commit hash, though.)
>>
>> Yes please, if you would not mind. Sorry about that and thank you for
>> spotting it Michael!
>>
>> Since you have to rebase to fix it, you can include Michael's acks?
>>
>> Cheers,
>> Nathan
>
> Done.

Thanks.

cheers