diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2023-10-16 22:07:30 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2023-10-18 14:09:16 +0200 |
| commit | e39828d2c1c0781ccfcf742791daf88fdfa481ea (patch) | |
| tree | 85845061ad06c7d3c9eaa9511cddc804899ff916 /arch/x86 | |
| parent | 1d10f3aec2bb734b4b594afe8c1bd0aa656a7e4d (diff) | |
x86/percpu: Use the correct asm operand modifier in percpu_stable_op()
The "P" asm operand modifier is a x86 target-specific modifier.
When used for a constant, it drops all syntax-specific prefixes and
issues the bare constant. This modifier is not correct for address
handling, in this case a generic "a" operand modifier should be used.
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.
Clang allows only "i" and "r" operand constraints with an "a" modifier,
so the patch normalizes the modifier/constraint pair to "a"/"i"
which is consistent between both compilers.
The patch reduces code size of a test build by 4072 bytes:
text data bss dec hex filename
25523268 4388300 808452 30720020 1d4c014 vmlinux-old.o
25519196 4388300 808452 30715948 1d4b02c vmlinux-new.o
[ mingo: Changelog clarity. ]
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20231016200755.287403-1-ubizjak@gmail.com
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/include/asm/percpu.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h index 54746903b8c3..ac3220aeb779 100644 --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h @@ -194,9 +194,9 @@ do { \ #define percpu_stable_op(size, op, _var) \ ({ \ __pcpu_type_##size pfo_val__; \ - asm(__pcpu_op2_##size(op, __force_percpu_arg(P[var]), "%[val]") \ + asm(__pcpu_op2_##size(op, __force_percpu_arg(a[var]), "%[val]") \ : [val] __pcpu_reg_##size("=", pfo_val__) \ - : [var] "p" (&(_var))); \ + : [var] "i" (&(_var))); \ (typeof(_var))(unsigned long) pfo_val__; \ }) |