diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2026-01-05 10:02:32 +0100 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2026-01-20 12:34:58 +0100 |
| commit | 53ed3d91a141f5c8b3bce45b0004fbbfefe77956 (patch) | |
| tree | 11d84d35cfb529750bcd3406066a34e0fd5fb75e | |
| parent | 59cac9d52b885cbeba45fa455417b03dfb03eaa7 (diff) | |
x86/segment: Use MOVL when reading segment registers
Use MOVL when reading segment registers to avoid 0x66 operand-size override
insn prefix. The segment value is always 16-bit and gets zero-extended to the
full 32-bit size.
Example:
4e4: 66 8c c0 mov %es,%ax
4e7: 66 89 83 80 0b 00 00 mov %ax,0xb80(%rbx)
4e4: 8c c0 mov %es,%eax
4e6: 66 89 83 80 0b 00 00 mov %ax,0xb80(%rbx)
Also, use the %k0 modifier which generates the SImode (signed integer)
register name for the target register.
[ bp: Extend and clarify commit message. ]
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Link: https://patch.msgid.link/20260105090422.6243-1-ubizjak@gmail.com
| -rw-r--r-- | arch/x86/include/asm/segment.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h index f59ae7186940..9f5be2bbd291 100644 --- a/arch/x86/include/asm/segment.h +++ b/arch/x86/include/asm/segment.h @@ -348,7 +348,7 @@ static inline void __loadsegment_fs(unsigned short value) * Save a segment register away: */ #define savesegment(seg, value) \ - asm("mov %%" #seg ",%0":"=r" (value) : : "memory") + asm("movl %%" #seg ",%k0" : "=r" (value) : : "memory") #endif /* !__ASSEMBLER__ */ #endif /* __KERNEL__ */ |