On Wed, May 27, 2020 at 7:14 AM Arnd Bergmann <arnd@xxxxxxxx> 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. > > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> > --- > --- > 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
