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x86/asm: Use %a instead of %P operand modifier in asm templates

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The "P" asm operand modifier is a x86 target-specific modifier.

For x86_64, when used with a symbol reference, the "%P" modifier
emits "sym" instead of "sym(%rip)". This property is currently
used to issue bare symbol reference.

The generic "a" operand modifier should be used instead. The "a"
asm operand modifier substitutes a memory reference, with the
actual operand treated as address.  For x86_64, when a symbol is
provided, the "a" modifier emits "sym(%rip)" instead of "sym",
enabling shorter %rip-relative addressing.

Also note that unlike GCC, clang emits %rip-relative symbol
reference with "P" asm operand modifier, so the patch also unifies
symbol handling with both compilers.

No functional changes intended.

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/20240319104418.284519-4-ubizjak@gmail.com
This commit is contained in:
Uros Bizjak 2024-03-19 11:40:14 +01:00 • committed by Ingo Molnar
parent 41cd2e1ee9
commit d689863c1a
1 changed files with 1 additions and 1 deletions
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2
arch/x86/include/asm/cpufeature.h
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@ -172,7 +172,7 @@ static __always_inline bool _static_cpu_has(u16 bit)
ALTERNATIVE_TERNARY("jmp 6f", %c[feature], "", "jmp %l[t_no]")
".pushsection .altinstr_aux,\"ax\"\n"
"6:\n"
" testb %[bitnum]," _ASM_RIP(%P[cap_byte]) "\n"
" testb %[bitnum], %a[cap_byte]\n"
" jnz %l[t_yes]\n"
" jmp %l[t_no]\n"
".popsection\n"