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.
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
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.
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
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
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Arnd Bergmann -
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