diff options
authorJosh Poimboeuf <>2016-03-09 12:59:50 -0600
committerPaolo Bonzini <>2016-05-10 18:16:50 +0200
commit4548f63e65116458da5245d89aa213b4f8b2ab16 (patch)
parent5e1b59abef69e405eabfbe0ad09ad6b6e5303c7d (diff)
x86/kvm: Add stack frame dependency to fastop() inline asm
The kbuild test robot reported this objtool warning [1]: arch/x86/kvm/emulate.o: warning: objtool: fastop()+0x69: call without frame pointer save/setup The issue seems to be caused by CONFIG_PROFILE_ALL_BRANCHES. With that option, for some reason gcc decides not to create a stack frame in fastop() before doing the inline asm call, which can result in a bad stack trace. Force a stack frame to be created if CONFIG_FRAME_POINTER is enabled by listing the stack pointer as an output operand for the inline asm statement. This change has no effect for !CONFIG_PROFILE_ALL_BRANCHES. [1] Reported-by: kbuild test robot <> Signed-off-by: Josh Poimboeuf <> Acked-by: Ingo Molnar <> Signed-off-by: Paolo Bonzini <>
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 0f6294376fbd..a2f24af3c999 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5110,13 +5110,17 @@ static void fetch_possible_mmx_operand(struct x86_emulate_ctxt *ctxt,
static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *))
+ register void *__sp asm(_ASM_SP);
ulong flags = (ctxt->eflags & EFLAGS_MASK) | X86_EFLAGS_IF;
if (!(ctxt->d & ByteOp))
fop += __ffs(ctxt->dst.bytes) * FASTOP_SIZE;
asm("push %[flags]; popf; call *%[fastop]; pushf; pop %[flags]\n"
: "+a"(ctxt->dst.val), "+d"(ctxt->src.val), [flags]"+D"(flags),
- [fastop]"+S"(fop)
+ [fastop]"+S"(fop), "+r"(__sp)
: "c"(ctxt->src2.val));
ctxt->eflags = (ctxt->eflags & ~EFLAGS_MASK) | (flags & EFLAGS_MASK);
if (!fop) /* exception is returned in fop variable */
return emulate_de(ctxt);