On 21/01/2016 23:49, Josh Poimboeuf wrote:
> 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.
If an __always_inline allocation works, that would be better.
Paolo
> 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;
> }
>
>
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