* [PATCH] x86: fix clang integrated assembler build
@ 2020-05-27 14:15 Arnd Bergmann
2020-05-27 18:04 ` Nick Desaulniers
0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2020-05-27 14:15 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86
Cc: Arnd Bergmann, stable, H. Peter Anvin, Jiri Slaby, Juergen Gross,
Herbert Xu, Tony Luck, linux-kernel, clang-built-linux
clang and gas seem to interpret the symbols in memmove_64.S and
memset_64.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/x86/lib/memmove_64.S | 4 ++--
arch/x86/lib/memset_64.S | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S
index 7ff00ea64e4f..dcca01434be8 100644
--- a/arch/x86/lib/memmove_64.S
+++ b/arch/x86/lib/memmove_64.S
@@ -26,8 +26,8 @@
*/
.weak memmove
-SYM_FUNC_START_ALIAS(memmove)
-SYM_FUNC_START(__memmove)
+SYM_FUNC_START_ALIAS(__memmove)
+SYM_FUNC_START_LOCAL(memmove)
mov %rdi, %rax
diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
index 9ff15ee404a4..a97f2ea4e0b2 100644
--- a/arch/x86/lib/memset_64.S
+++ b/arch/x86/lib/memset_64.S
@@ -19,8 +19,8 @@
*
* rax original destination
*/
-SYM_FUNC_START_ALIAS(memset)
-SYM_FUNC_START(__memset)
+SYM_FUNC_START_ALIAS(__memset)
+SYM_FUNC_START_LOCAL(memset)
/*
* Some CPUs support enhanced REP MOVSB/STOSB feature. It is recommended
* to use it when possible. If not available, use fast string instructions.
--
2.26.2
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] x86: fix clang integrated assembler build
2020-05-27 14:15 [PATCH] x86: fix clang integrated assembler build Arnd Bergmann
@ 2020-05-27 18:04 ` Nick Desaulniers
[not found] ` <CAGG=3QWwafjBUPaGLbJxyU7K65H0SnHBHZ-mnxtAC2A1xfjWYA@mail.gmail.com>
0 siblings, 1 reply; 3+ messages in thread
From: Nick Desaulniers @ 2020-05-27 18:04 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Thomas Gleixner, Ingo Molnar, Borislav Petkov,
maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT),
# 3.4.x, H. Peter Anvin, Jiri Slaby, Juergen Gross, Herbert Xu,
Tony Luck, LKML, clang-built-linux, Fangrui Song, Bill Wendling,
Jian Cai
On Wed, May 27, 2020 at 7:16 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> clang and gas seem to interpret the symbols in memmove_64.S and
> memset_64.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>
+ Bill, Fangrui, Jian
I think we saw this bug or a very similar bug internally around the
ordering of .weak to .global.
> ---
> arch/x86/lib/memmove_64.S | 4 ++--
> arch/x86/lib/memset_64.S | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S
> index 7ff00ea64e4f..dcca01434be8 100644
> --- a/arch/x86/lib/memmove_64.S
> +++ b/arch/x86/lib/memmove_64.S
> @@ -26,8 +26,8 @@
> */
> .weak memmove
>
> -SYM_FUNC_START_ALIAS(memmove)
> -SYM_FUNC_START(__memmove)
> +SYM_FUNC_START_ALIAS(__memmove)
> +SYM_FUNC_START_LOCAL(memmove)
>
> mov %rdi, %rax
>
> diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
> index 9ff15ee404a4..a97f2ea4e0b2 100644
> --- a/arch/x86/lib/memset_64.S
> +++ b/arch/x86/lib/memset_64.S
> @@ -19,8 +19,8 @@
> *
> * rax original destination
> */
> -SYM_FUNC_START_ALIAS(memset)
> -SYM_FUNC_START(__memset)
> +SYM_FUNC_START_ALIAS(__memset)
> +SYM_FUNC_START_LOCAL(memset)
> /*
> * Some CPUs support enhanced REP MOVSB/STOSB feature. It is recommended
> * to use it when possible. If not available, use fast string instructions.
> --
> 2.26.2
>
> --
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--
Thanks,
~Nick Desaulniers
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-05-27 14:15 [PATCH] x86: fix clang integrated assembler build Arnd Bergmann
2020-05-27 18:04 ` Nick Desaulniers
[not found] ` <CAGG=3QWwafjBUPaGLbJxyU7K65H0SnHBHZ-mnxtAC2A1xfjWYA@mail.gmail.com>
2020-06-01 21:04 ` Nick Desaulniers
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