[PATCH] x86: fix clang integrated assembler build

* [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


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