diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2022-06-28 18:16:12 +0200 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2022-08-15 19:18:12 +0200 |
| commit | 4630535c64725bcd722eb59fb8d92be8db943d3d (patch) | |
| tree | 5e1e91f790fcf678c1d33d7b89575d29b7d0456e /arch | |
| parent | x86: Fix various duplicate-word comment typos (diff) | |
| download | linux-4630535c64725bcd722eb59fb8d92be8db943d3d.tar.xz linux-4630535c64725bcd722eb59fb8d92be8db943d3d.zip | |
x86/uaccess: Improve __try_cmpxchg64_user_asm() for x86_32
Improve __try_cmpxcgh64_user_asm() for !CONFIG_CC_HAS_ASM_GOTO_TIED_OUTPUT
by relaxing the output register constraint from "c" to "q" constraint,
which allows the compiler to choose between %ecx or %ebx register.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220628161612.7993-1-ubizjak@gmail.com
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/uaccess.h | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 913e593a3b45..b0583c1da14f 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -448,7 +448,7 @@ do { \ #ifdef CONFIG_X86_32 /* - * Unlike the normal CMPXCHG, hardcode ECX for both success/fail and error. + * Unlike the normal CMPXCHG, use output GPR for both success/fail and error. * There are only six GPRs available and four (EAX, EBX, ECX, and EDX) are * hardcoded by CMPXCHG8B, leaving only ESI and EDI. If the compiler uses * both ESI and EDI for the memory operand, compilation will fail if the error @@ -461,11 +461,12 @@ do { \ __typeof__(*(_ptr)) __new = (_new); \ asm volatile("\n" \ "1: " LOCK_PREFIX "cmpxchg8b %[ptr]\n" \ - "mov $0, %%ecx\n\t" \ - "setz %%cl\n" \ + "mov $0, %[result]\n\t" \ + "setz %b[result]\n" \ "2:\n" \ - _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG, %%ecx) \ - : [result]"=c" (__result), \ + _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG, \ + %[result]) \ + : [result] "=q" (__result), \ "+A" (__old), \ [ptr] "+m" (*_ptr) \ : "b" ((u32)__new), \ |