From 194a613088a8c9dae300dfb08433287cee803e8d Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Wed, 12 Mar 2025 13:38:44 +0100 Subject: [PATCH] x86/hweight: Use ASM_CALL_CONSTRAINT in inline asm() Use ASM_CALL_CONSTRAINT to prevent inline asm() that includes call instruction from being scheduled before the frame pointer gets set up by the containing function. This unconstrained scheduling might cause objtool to print a "call without frame pointer save/setup" warning. Current versions of compilers don't seem to trigger this condition, but without this constraint there's nothing to prevent the compiler from scheduling the insn in front of frame creation. Signed-off-by: Uros Bizjak Signed-off-by: Ingo Molnar Cc: "H. Peter Anvin" Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Linus Torvalds Link: https://lore.kernel.org/r/20250312123905.149298-2-ubizjak@gmail.com --- arch/x86/include/asm/arch_hweight.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/arch_hweight.h b/arch/x86/include/asm/arch_hweight.h index a11bb841c434..f233eb00f41f 100644 --- a/arch/x86/include/asm/arch_hweight.h +++ b/arch/x86/include/asm/arch_hweight.h @@ -17,7 +17,7 @@ static __always_inline unsigned int __arch_hweight32(unsigned int w) unsigned int res; asm (ALTERNATIVE("call __sw_hweight32", "popcntl %[val], %[cnt]", X86_FEATURE_POPCNT) - : [cnt] "=" REG_OUT (res) + : [cnt] "=" REG_OUT (res), ASM_CALL_CONSTRAINT : [val] REG_IN (w)); return res; @@ -45,7 +45,7 @@ static __always_inline unsigned long __arch_hweight64(__u64 w) unsigned long res; asm (ALTERNATIVE("call __sw_hweight64", "popcntq %[val], %[cnt]", X86_FEATURE_POPCNT) - : [cnt] "=" REG_OUT (res) + : [cnt] "=" REG_OUT (res), ASM_CALL_CONSTRAINT : [val] REG_IN (w)); return res;