On Tue, May 08, 2018 at 06:21:36PM +0300, Alexey Budankov wrote: > > Store user space frame-pointer value (BP register) into Perf trace > on a sample for a process so the value becomes available when > unwinding call stacks for functions gaining event samples. > > Signed-off-by: Alexey Budankov <alexey.budan...@linux.intel.com> > --- > arch/x86/kernel/perf_regs.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c > index e47b2dbbdef3..8d68658eff7f 100644 > --- a/arch/x86/kernel/perf_regs.c > +++ b/arch/x86/kernel/perf_regs.c > @@ -156,7 +156,13 @@ void perf_get_regs_user(struct perf_regs *regs_user,
> * Most system calls don't save these registers, don't report them. ^^^ that worries me and is the reason for the '-1's below. However I think with all the PTI rework this might no longer be true. The Changelog needs to state that user_regs->bp is in fact valid and ideally point to the commits that makes it so. Also this patch should update that comment. Cc Andy who keeps better track of all that than me. > */ > regs_user_copy->bx = -1; > - regs_user_copy->bp = -1; > + /* > + * Store user space frame-pointer value on sample > + * to facilitate stack unwinding for cases when > + * user space executable code has such support > + * enabled at compile time; > + */ > + regs_user_copy->bp = user_regs->bp; > regs_user_copy->r12 = -1; > regs_user_copy->r13 = -1; > regs_user_copy->r14 = -1;
