On Wed, May 27, 2020 at 1:57 PM Bill Wendling <morbo@xxxxxxxxxx> wrote: > > > > On Wed, May 27, 2020 at 11:04 AM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: >> >> On Wed, May 27, 2020 at 7:16 AM Arnd Bergmann <arnd@xxxxxxxx> wrote: >> > >> > clang and gas seem to interpret the symbols in memmove_64.S and >> > memset_64.S differently, such that clang does not make them >> > 'weak' as expected, which leads to a linker error, with both >> > ld.bfd and ld.lld: >> > >> > ld.lld: error: duplicate symbol: memmove >> > >>> defined at common.c >> > >>> kasan/common.o:(memmove) in archive mm/built-in.a >> > >>> defined at memmove.o:(__memmove) in archive arch/arm64/lib/lib.a >> > >> > ld.lld: error: duplicate symbol: memset >> > >>> defined at common.c >> > >>> kasan/common.o:(memset) in archive mm/built-in.a >> > >>> defined at memset.o:(__memset) in archive arch/arm64/lib/lib.a >> > >> > Copy the exact way these are written in memcpy_64.S, which does >> > not have the same problem. >> > >> > I don't know why this makes a difference, and it would be good >> > to have someone with a better understanding of assembler internals >> > review it. >> > >> > It might be either a bug in the kernel or a bug in the assembler, >> > no idea which one. My patch makes it work with all versions of >> > clang and gcc, which is probably helpful even if it's a workaround >> > for a clang bug. >> > >> > Cc: stable@xxxxxxxxxxxxxxx >> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> >> >> + Bill, Fangrui, Jian >> I think we saw this bug or a very similar bug internally around the >> ordering of .weak to .global. >> > I think that would be this patch by Fangrui: > > https://prodkernel-review.git.corp.google.com/c/kernel/release/9xx/+/292011 Thanks. That patch references this discussion: https://lore.kernel.org/linuxppc-dev/20200325164257.170229-1-maskray@xxxxxxxxxx/ > > -bw > >> >> > --- >> > arch/x86/lib/memmove_64.S | 4 ++-- >> > arch/x86/lib/memset_64.S | 4 ++-- >> > 2 files changed, 4 insertions(+), 4 deletions(-) >> > >> > diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S >> > index 7ff00ea64e4f..dcca01434be8 100644 >> > --- a/arch/x86/lib/memmove_64.S >> > +++ b/arch/x86/lib/memmove_64.S >> > @@ -26,8 +26,8 @@ >> > */ >> > .weak memmove >> > >> > -SYM_FUNC_START_ALIAS(memmove) >> > -SYM_FUNC_START(__memmove) >> > +SYM_FUNC_START_ALIAS(__memmove) >> > +SYM_FUNC_START_LOCAL(memmove) >> > >> > mov %rdi, %rax >> > >> > diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S >> > index 9ff15ee404a4..a97f2ea4e0b2 100644 >> > --- a/arch/x86/lib/memset_64.S >> > +++ b/arch/x86/lib/memset_64.S >> > @@ -19,8 +19,8 @@ >> > * >> > * rax original destination >> > */ >> > -SYM_FUNC_START_ALIAS(memset) >> > -SYM_FUNC_START(__memset) >> > +SYM_FUNC_START_ALIAS(__memset) >> > +SYM_FUNC_START_LOCAL(memset) >> > /* >> > * Some CPUs support enhanced REP MOVSB/STOSB feature. It is recommended >> > * to use it when possible. If not available, use fast string instructions. >> > -- >> > 2.26.2 >> > >> > -- >> > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. >> > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@xxxxxxxxxxxxxxxx. >> > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200527141553.1768675-1-arnd%40arndb.de. >> >> >> >> -- >> Thanks, >> ~Nick Desaulniers -- Thanks, ~Nick Desaulniers
