After commit 73cdf24e81e4 ("powerpc64: make clang cross-build
friendly"), building 64-bit little endian + CONFIG_COMPAT=y with clang
results in many warnings along the lines of:
$ cat arch/powerpc/configs/compat.config
CONFIG_COMPAT=y
$ make -skj"$(nproc)" ARCH=powerpc LLVM=1 ppc64le_defconfig compat.config
arch/powerpc/kernel/vdso/
...
In file included from <built-in>:4:
In file included from lib/vdso/gettimeofday.c:6:
In file included from include/vdso/datapage.h:15:
In file included from include/vdso/cache.h:5:
arch/powerpc/include/asm/cache.h:77:8: warning: unknown attribute
'patchable_function_entry' ignored [-Wunknown-attributes]
77 | static inline u32 l1_icache_bytes(void)
| ^~~~~~
include/linux/compiler_types.h:235:58: note: expanded from macro 'inline'
235 | #define inline inline __gnu_inline __inline_maybe_unused notrace
| ^~~~~~~
include/linux/compiler_types.h:215:34: note: expanded from macro 'notrace'
215 | #define notrace
__attribute__((patchable_function_entry(0, 0)))
|
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...
arch/powerpc/Makefile adds -DCC_USING_PATCHABLE_FUNCTION_ENTRY to
KBUILD_CPPFLAGS, which is inherited by the 32-bit vDSO. However, the
32-bit little endian target does not support
'-fpatchable-function-entry', resulting in the warnings above.
Remove -DCC_USING_PATCHABLE_FUNCTION_ENTRY from the 32-bit vDSO flags
when building with clang to avoid the warnings.
Fixes: 73cdf24e81e4 ("powerpc64: make clang cross-build friendly")
Signed-off-by: Nathan Chancellor <[email protected]>
---
arch/powerpc/kernel/vdso/Makefile | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/powerpc/kernel/vdso/Makefile
b/arch/powerpc/kernel/vdso/Makefile
index 8834dfe9d727..368759f81708 100644
--- a/arch/powerpc/kernel/vdso/Makefile
+++ b/arch/powerpc/kernel/vdso/Makefile
@@ -62,6 +62,12 @@ CC32FLAGSREMOVE += -fno-stack-clash-protection
# 32-bit one. clang validates the values passed to these arguments during
# parsing, even when -fno-stack-protector is passed afterwards.
CC32FLAGSREMOVE += -mstack-protector-guard%
+# ftrace is disabled for the vdso but arch/powerpc/Makefile adds this define to
+# KBUILD_CPPFLAGS, which enables use of the 'patchable_function_entry'
+# attribute in the 'inline' define via 'notrace'. This attribute is not
+# supported for the powerpcle target, resulting in many instances of
+# -Wunknown-attributes.
+CC32FLAGSREMOVE += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
endif
LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
AS32FLAGS := -D__VDSO32__
---
base-commit: 35e4f2a17eb40288f9bcdb09549fa04a63a96279
change-id: 20260311-ppc-vdso-drop-cc-using-pfe-define-clang-46d6f5041544
Best regards,
--
Nathan Chancellor <[email protected]>
