Messages in this thread | | | Date | Wed, 27 May 2020 11:28:43 -0700 | From | Fangrui Song <> | Subject | Re: [PATCH] arm64: fix clang integrated assembler build |
| |
On 2020-05-27, 'Nick Desaulniers' via Clang Built Linux wrote: >On Wed, May 27, 2020 at 7:14 AM Arnd Bergmann <arnd@arndb.de> wrote: >> >> clang and gas seem to interpret the symbols in memmove.S and >> memset.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. > >+ Bill, Fangrui, Jian >I think we saw this bug or a very similar bug internally around the >ordering of .weak to .global.
This may be another instance of https://sourceware.org/pipermail/binutils/2020-March/000299.html https://lore.kernel.org/linuxppc-dev/20200325164257.170229-1-maskray@google.com/
I haven't checked but there may be both a .globl directive and a .weak directive
>> Cc: stable@vger.kernel.org >> Signed-off-by: Arnd Bergmann <arnd@arndb.de> >> --- >> --- >> arch/arm64/lib/memcpy.S | 3 +-- >> arch/arm64/lib/memmove.S | 3 +-- >> arch/arm64/lib/memset.S | 3 +-- >> 3 files changed, 3 insertions(+), 6 deletions(-) >> >> diff --git a/arch/arm64/lib/memcpy.S b/arch/arm64/lib/memcpy.S >> index e0bf83d556f2..dc8d2a216a6e 100644 >> --- a/arch/arm64/lib/memcpy.S >> +++ b/arch/arm64/lib/memcpy.S >> @@ -56,9 +56,8 @@ >> stp \reg1, \reg2, [\ptr], \val >> .endm >> >> - .weak memcpy >> SYM_FUNC_START_ALIAS(__memcpy) >> -SYM_FUNC_START_PI(memcpy) >> +SYM_FUNC_START_WEAK_PI(memcpy) >> #include "copy_template.S" >> ret >> SYM_FUNC_END_PI(memcpy) >> diff --git a/arch/arm64/lib/memmove.S b/arch/arm64/lib/memmove.S >> index 02cda2e33bde..1035dce4bdaf 100644 >> --- a/arch/arm64/lib/memmove.S >> +++ b/arch/arm64/lib/memmove.S >> @@ -45,9 +45,8 @@ C_h .req x12 >> D_l .req x13 >> D_h .req x14 >> >> - .weak memmove >> SYM_FUNC_START_ALIAS(__memmove) >> -SYM_FUNC_START_PI(memmove) >> +SYM_FUNC_START_WEAK_PI(memmove) >> cmp dstin, src >> b.lo __memcpy >> add tmp1, src, count >> diff --git a/arch/arm64/lib/memset.S b/arch/arm64/lib/memset.S >> index 77c3c7ba0084..a9c1c9a01ea9 100644 >> --- a/arch/arm64/lib/memset.S >> +++ b/arch/arm64/lib/memset.S >> @@ -42,9 +42,8 @@ dst .req x8 >> tmp3w .req w9 >> tmp3 .req x9 >> >> - .weak memset >> SYM_FUNC_START_ALIAS(__memset) >> -SYM_FUNC_START_PI(memset) >> +SYM_FUNC_START_WEAK_PI(memset) >> mov dst, dstin /* Preserve return value. */ >> and A_lw, val, #255 >> orr A_lw, A_lw, A_lw, lsl #8 >> -- >> 2.26.2 > >-- >Thanks, >~Nick Desaulniers > >-- >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@googlegroups.com. >To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/CAKwvOdnNxj-MdKj3aWoefF2W9PPG-TSeNU4Ym-N8NODJB5Yw_w%40mail.gmail.com.
| |