powerpc/boot: Ensure _zimage_start is a weak symbol
authorJoel Stanley <joel@jms.id.au>
Fri, 14 Sep 2018 04:06:47 +0000 (13:36 +0930)
committerMichael Ellerman <mpe@ellerman.id.au>
Wed, 19 Sep 2018 12:08:12 +0000 (22:08 +1000)
commitee9d21b3b3583712029a0db65a4b7c081d08d3b3
treef25dba50ba38ae44be01a2ec1a50cb1f3a608780
parentcbc39809a398b1a30c2bdb0f3123eef18c28a729
powerpc/boot: Ensure _zimage_start is a weak symbol

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/#!topic/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>
arch/powerpc/boot/crt0.S