[PATCH] powerpc/boot: Disable power10 features after BOOTAFLAGS assignment

Nathan Chancellor nathan at kernel.org
Fri Apr 28 05:34:53 AEST 2023

When building the boot wrapper assembly files with clang after
commit 648a1783fe25 ("powerpc/boot: Fix boot wrapper code generation
with CONFIG_POWER10_CPU"), the following warnings appear for each file

  '-prefixed' is not a recognized feature for this target (ignoring feature)
  '-pcrel' is not a recognized feature for this target (ignoring feature)

While it is questionable whether or not LLVM should be emitting a
warning when passed negative versions of code generation flags when
building assembly files (since it does not emit a warning for the
altivec and vsx flags), it is easy enough to work around this by just
moving the disabled flags to BOOTCFLAGS after the assignment of
BOOTAFLAGS, so that they are not added when building assembly files.
Do so to silence the warnings.

Cc: stable at vger.kernel.org
Fixes: 648a1783fe25 ("powerpc/boot: Fix boot wrapper code generation with CONFIG_POWER10_CPU")
Link: https://github.com/ClangBuiltLinux/linux/issues/1839
Reviewed-by: Nicholas Piggin <npiggin at gmail.com>
Signed-off-by: Nathan Chancellor <nathan at kernel.org>
I do not think that 648a1783fe25 is truly to blame for this but the
Fixes tag will help the stable team ensure that this change gets
backported with 648a1783fe25. This is the minimal fix for the problem
but the true fix is separating AFLAGS and CFLAGS, which should be done
by this in-flight series by Nick:

 arch/powerpc/boot/Makefile | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/boot/Makefile b/arch/powerpc/boot/Makefile
index 85cde5bf04b7..771b79423bbc 100644
--- a/arch/powerpc/boot/Makefile
+++ b/arch/powerpc/boot/Makefile
@@ -34,8 +34,6 @@ endif
 BOOTCFLAGS    := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
 		 -fno-strict-aliasing -O2 -msoft-float -mno-altivec -mno-vsx \
-		 $(call cc-option,-mno-prefixed) $(call cc-option,-mno-pcrel) \
-		 $(call cc-option,-mno-mma) \
 		 $(call cc-option,-mno-spe) $(call cc-option,-mspe=no) \
 		 -pipe -fomit-frame-pointer -fno-builtin -fPIC -nostdinc \
@@ -71,6 +69,10 @@ BOOTAFLAGS	:= -D__ASSEMBLY__ $(BOOTCFLAGS) -nostdinc
+BOOTCFLAGS	+= $(call cc-option,-mno-prefixed) \
+		   $(call cc-option,-mno-pcrel) \
+		   $(call cc-option,-mno-mma)

base-commit: 169f8997968ab620d750d9a45e15c5288d498356
change-id: 20230427-remove-power10-args-from-boot-aflags-clang-268c43e8c1fc

Best regards,
Nathan Chancellor <nathan at kernel.org>

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