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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2024-06-25 17:50:04 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2024-06-30 09:21:29 -0700 |
| commit | 769327258a141ba80ac8b96fce35c68631228370 (patch) | |
| tree | fae9fe4d5b62450f6ca163ecb467cbba00397c5d | |
| parent | 84dd4373d566df74fc77175ff76b1658089f43b5 (diff) | |
| download | linux-769327258a141ba80ac8b96fce35c68631228370.tar.gz linux-769327258a141ba80ac8b96fce35c68631228370.tar.bz2 linux-769327258a141ba80ac8b96fce35c68631228370.zip | |
x86-32: fix cmpxchg8b_emu build error with clang
The kernel test robot reported that clang no longer compiles the 32-bit
x86 kernel in some configurations due to commit 95ece48165c1
("locking/atomic/x86: Rewrite x86_32 arch_atomic64_{,fetch}_{and,or,xor}()
functions").
The build fails with
arch/x86/include/asm/cmpxchg_32.h:149:9: error: inline assembly requires more registers than available
and the reason seems to be that not only does the cmpxchg8b instruction
need four fixed registers (EDX:EAX and ECX:EBX), with the emulation
fallback the inline asm also wants a fifth fixed register for the
address (it uses %esi for that, but that's just a software convention
with cmpxchg8b_emu).
Avoiding using another pointer input to the asm (and just forcing it to
use the "0(%esi)" addressing that we end up requiring for the sw
fallback) seems to fix the issue.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202406230912.F6XFIyA6-lkp@intel.com/
Fixes: 95ece48165c1 ("locking/atomic/x86: Rewrite x86_32 arch_atomic64_{,fetch}_{and,or,xor}() functions")
Link: https://lore.kernel.org/all/202406230912.F6XFIyA6-lkp@intel.com/
Suggested-by: Uros Bizjak <ubizjak@gmail.com>
Reviewed-and-Tested-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | arch/x86/include/asm/cmpxchg_32.h | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h index ed2797f132ce..62cef2113ca7 100644 --- a/arch/x86/include/asm/cmpxchg_32.h +++ b/arch/x86/include/asm/cmpxchg_32.h @@ -93,10 +93,9 @@ static __always_inline bool __try_cmpxchg64_local(volatile u64 *ptr, u64 *oldp, \ asm volatile(ALTERNATIVE(_lock_loc \ "call cmpxchg8b_emu", \ - _lock "cmpxchg8b %[ptr]", X86_FEATURE_CX8) \ - : [ptr] "+m" (*(_ptr)), \ - "+a" (o.low), "+d" (o.high) \ - : "b" (n.low), "c" (n.high), "S" (_ptr) \ + _lock "cmpxchg8b %a[ptr]", X86_FEATURE_CX8) \ + : "+a" (o.low), "+d" (o.high) \ + : "b" (n.low), "c" (n.high), [ptr] "S" (_ptr) \ : "memory"); \ \ o.full; \ @@ -122,12 +121,11 @@ static __always_inline u64 arch_cmpxchg64_local(volatile u64 *ptr, u64 old, u64 \ asm volatile(ALTERNATIVE(_lock_loc \ "call cmpxchg8b_emu", \ - _lock "cmpxchg8b %[ptr]", X86_FEATURE_CX8) \ + _lock "cmpxchg8b %a[ptr]", X86_FEATURE_CX8) \ CC_SET(e) \ : CC_OUT(e) (ret), \ - [ptr] "+m" (*(_ptr)), \ "+a" (o.low), "+d" (o.high) \ - : "b" (n.low), "c" (n.high), "S" (_ptr) \ + : "b" (n.low), "c" (n.high), [ptr] "S" (_ptr) \ : "memory"); \ \ if (unlikely(!ret)) \ |