Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Wed, 20 Mar 2024 11:21:40 -0000 | From | "tip-bot2 for Uros Bizjak" <> | Subject | [tip: x86/asm] x86/asm: Use "m" operand constraint in WRUSSQ asm template |
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The following commit has been merged into the x86/asm branch of tip:
Commit-ID: 648337147d3550c1ca3d1b500e66dbda12e2d836 Gitweb: https://git.kernel.org/tip/648337147d3550c1ca3d1b500e66dbda12e2d836 Author: Uros Bizjak <ubizjak@gmail.com> AuthorDate: Tue, 19 Mar 2024 18:16:46 +01:00 Committer: Ingo Molnar <mingo@kernel.org> CommitterDate: Wed, 20 Mar 2024 12:04:38 +01:00
x86/asm: Use "m" operand constraint in WRUSSQ asm template
The WRUSSQ instruction uses a memory operand, so use "m" operand constraint instead of forcing usage of pointer register using "r" constraint. The generated assembly code improves from:
6ece3: 48 8d 43 f8 lea -0x8(%rbx),%rax ... 6eceb: 66 48 0f 38 f5 18 wrussq %rbx,(%rax)
to:
6ecea: 66 48 0f 38 f5 43 f8 wrussq %rax,-0x8(%rbx)
Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Link: https://lore.kernel.org/r/20240319171714.76342-1-ubizjak@gmail.com --- arch/x86/include/asm/special_insns.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h index 0ee2ba5..aec6e2d 100644 --- a/arch/x86/include/asm/special_insns.h +++ b/arch/x86/include/asm/special_insns.h @@ -205,9 +205,9 @@ static inline void clwb(volatile void *__p) #ifdef CONFIG_X86_USER_SHADOW_STACK static inline int write_user_shstk_64(u64 __user *addr, u64 val) { - asm goto("1: wrussq %[val], (%[addr])\n" + asm goto("1: wrussq %[val], %[addr]\n" _ASM_EXTABLE(1b, %l[fail]) - :: [addr] "r" (addr), [val] "r" (val) + :: [addr] "m" (*addr), [val] "r" (val) :: fail); return 0; fail:
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