[PATCH 26/33] x86/kvm: Add stack frame dependency to test_cc() inline asm

[Josh Poimboeuf]

With some configs, gcc doesn't inline test_cc().  When that happens, it
doesn't create a stack frame before inserting the call instruction.
This breaks frame pointer convention if CONFIG_FRAME_POINTER is enabled
and 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.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Gleb Natapov <gleb@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
---
 arch/x86/kvm/emulate.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index aa4d726..7dba65a 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -972,11 +972,13 @@ static int em_bsr_c(struct x86_emulate_ctxt *ctxt)
 static u8 test_cc(unsigned int condition, unsigned long flags)
 {
 	u8 rc;
+	register void *__sp asm(_ASM_SP);
 	void (*fop)(void) = (void *)em_setcc + 4 * (condition & 0xf);
 
 	flags = (flags & EFLAGS_MASK) | X86_EFLAGS_IF;
 	asm("push %[flags]; popf; call *%[fastop]"
-	    : "=a"(rc) : [fastop]"r"(fop), [flags]"r"(flags));
+	    : "=a"(rc), "+r"(__sp)
+	    : [fastop]"r"(fop), [flags]"r"(flags));
 	return rc;
 }
 
-- 
2.4.3