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objtool, x86/hweight: Remove ANNOTATE_IGNORE_ALTERNATIVE

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Since objtool's inception, frame pointer warnings have been manually
silenced for __arch_hweight*() to allow those functions' inline asm to
avoid using ASM_CALL_CONSTRAINT.

The potentially dubious reasoning for that decision over nine years ago
was that since !X86_FEATURE_POPCNT is exceedingly rare, it's not worth
hurting the code layout for a function call that will never happen on
the vast majority of systems.

However, those functions actually started using ASM_CALL_CONSTRAINT with
the following commit:

  194a613088 ("x86/hweight: Use ASM_CALL_CONSTRAINT in inline asm()")

And rightfully so, as it makes the code correct.  ASM_CALL_CONSTRAINT
will soon have no effect for non-FP configs anyway.

With ASM_CALL_CONSTRAINT in place, ANNOTATE_IGNORE_ALTERNATIVE no longer
has a purpose for the hweight functions.  Remove it.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/e7070dba3278c90f1a836b16157dcd34ccd21e21.1744318586.git.jpoimboe@kernel.org
This commit is contained in:
Josh Poimboeuf 2025-04-10 13:58:35 -07:00 • committed by Ingo Molnar
parent d51faee4bd
commit 7b3169dfa4
1 changed files with 2 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

6
arch/x86/include/asm/arch_hweight.h
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@ -16,8 +16,7 @@ static __always_inline unsigned int __arch_hweight32(unsigned int w)
{
unsigned int res;
asm_inline (ALTERNATIVE(ANNOTATE_IGNORE_ALTERNATIVE
"call __sw_hweight32",
asm_inline (ALTERNATIVE("call __sw_hweight32",
"popcntl %[val], %[cnt]", X86_FEATURE_POPCNT)
: [cnt] "=" REG_OUT (res), ASM_CALL_CONSTRAINT
: [val] REG_IN (w));
@ -46,8 +45,7 @@ static __always_inline unsigned long __arch_hweight64(__u64 w)
{
unsigned long res;
asm_inline (ALTERNATIVE(ANNOTATE_IGNORE_ALTERNATIVE
"call __sw_hweight64",
asm_inline (ALTERNATIVE("call __sw_hweight64",
"popcntq %[val], %[cnt]", X86_FEATURE_POPCNT)
: [cnt] "=" REG_OUT (res), ASM_CALL_CONSTRAINT
: [val] REG_IN (w));