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....
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 memcpySYM_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 memmoveSYM_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 memsetSYM_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-MdKj3aWoefF2....