Re: [PATCH v1]: perf/x86: store user space frame-pointer value on a sample

[Andi Kleen]

On Fri, Apr 06, 2018 at 10:06:26PM +0300, Alexey Budankov wrote:
> On 06.04.2018 18:31, Andi Kleen wrote:
> >> diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c
> >> index e47b2dbbdef3..9284048cf5b0 100644
> >> --- a/arch/x86/kernel/perf_regs.c
> >> +++ b/arch/x86/kernel/perf_regs.c
> >> @@ -157,6 +157,15 @@ void perf_get_regs_user(struct perf_regs *regs_user,
> >>  	 */
> >>  	regs_user_copy->bx = -1;
> >>  	regs_user_copy->bp = -1;
> >> +	if (user_64bit_mode(user_regs)) {
> > 
> > Why is it 64bit only? Should work on 32bit too.
> 
> bp register is a part of i386 syscall ABI 
> (http://man7.org/linux/man-pages/man2/syscall.2.html) 
> so not sure if it will make any sense for 32bit processes. 

Both 32bit and 64bit use the same frame pointer, if they
use frame pointer.

-Andi