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@xxxxxxxxx>
AuthorDate: Tue, 19 Mar 2024 18:16:46 +01:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Link: https://lore.kernel.org/r/20240319171714.76342-1-ubizjak@xxxxxxxxx
---
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:
|