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

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

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index fa938ed96506dafb4683a75e0a14355352bdbb6c..daae5c6e7d0eddd7937233b7d874713175170cb9 100644 (file)
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -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"