diff mbox series

arm64: fix clang integrated assembler build

Message ID 20200527141435.1716510-1-arnd@arndb.de (mailing list archive)
State New, archived
Headers show
Series arm64: fix clang integrated assembler build | expand

Commit Message

Arnd Bergmann May 27, 2020, 2:14 p.m. UTC 
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(-)

Comments

Nick Desaulniers May 27, 2020, 6:03 p.m. UTC | #1 
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 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
Fangrui Song May 27, 2020, 6:28 p.m. UTC | #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.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
>
>-- 
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diff mbox series

Patch

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