From: Joel Stanley joel@jms.id.au
[ Upstream commit ee9d21b3b3583712029a0db65a4b7c081d08d3b3 ]
When building with clang crt0's _zimage_start is not marked weak, which breaks the build when linking the kernel image:
$ objdump -t arch/powerpc/boot/crt0.o |grep _zimage_start$ 0000000000000058 g .text 0000000000000000 _zimage_start
ld: arch/powerpc/boot/wrapper.a(crt0.o): in function '_zimage_start': (.text+0x58): multiple definition of '_zimage_start'; arch/powerpc/boot/pseries-head.o:(.text+0x0): first defined here
Clang requires the .weak directive to appear after the symbol is declared. The binutils manual says:
This directive sets the weak attribute on the comma separated list of symbol names. If the symbols do not already exist, they will be created.
So it appears this is different with clang. The only reference I could see for this was an OpenBSD mailing list post[1].
Changing it to be after the declaration fixes building with Clang, and still works with GCC.
$ objdump -t arch/powerpc/boot/crt0.o |grep _zimage_start$ 0000000000000058 w .text 0000000000000000 _zimage_start
Reported to clang as https://bugs.llvm.org/show_bug.cgi?id=38921
[1] https://groups.google.com/forum/#%21topic/fa.openbsd.tech/PAgKKen2YCY
Signed-off-by: Joel Stanley joel@jms.id.au Reviewed-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/boot/crt0.S | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/boot/crt0.S b/arch/powerpc/boot/crt0.S index 14de4f8778a7..8539ac93b0de 100644 --- a/arch/powerpc/boot/crt0.S +++ b/arch/powerpc/boot/crt0.S @@ -47,8 +47,10 @@ p_end: .long _end p_pstack: .long _platform_stack_top #endif
- .weak _zimage_start .globl _zimage_start + /* Clang appears to require the .weak directive to be after the symbol + * is defined. See https://bugs.llvm.org/show_bug.cgi?id=38921 */ + .weak _zimage_start _zimage_start: .globl _zimage_start_lib _zimage_start_lib: