On Thu, 8 Jun 2017 22:43:54 +0900 Masami Hiramatsu <mhira...@kernel.org> wrote:
> On Thu, 1 Jun 2017 16:18:15 +0530 > "Naveen N. Rao" <naveen.n....@linux.vnet.ibm.com> wrote: > > > This fixes a crash when function_graph and jprobes are used together. > > This is essentially commit 237d28db036e ("ftrace/jprobes/x86: Fix > > conflict between jprobes and function graph tracing"), but for powerpc. > > > > Jprobes breaks function_graph tracing since the jprobe hook needs to use > > jprobe_return(), which never returns back to the hook, but instead to > > the original jprobe'd function. The solution is to momentarily pause > > function_graph tracing before invoking the jprobe hook and re-enable it > > when returning back to the original jprobe'd function. > > > > Fixes: 6794c78243bfd ("powerpc64: port of the function graph tracer") > > Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com> > > Acked-by: Masami Hiramatsu <mhira...@kernel.org> For what it's worth... Acked-by: Steven Rostedt (VMware) <rost...@goodmis.org> -- Steve > > Thanks! > > > --- > > v2: No changes since v1. > > > > arch/powerpc/kernel/kprobes.c | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c > > index e1fb95385a9e..0554d6e66194 100644 > > --- a/arch/powerpc/kernel/kprobes.c > > +++ b/arch/powerpc/kernel/kprobes.c > > @@ -610,6 +610,15 @@ int setjmp_pre_handler(struct kprobe *p, struct > > pt_regs *regs) > > regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc); > > #endif > > > > + /* > > + * jprobes use jprobe_return() which skips the normal return > > + * path of the function, and this messes up the accounting of the > > + * function graph tracer. > > + * > > + * Pause function graph tracing while performing the jprobe function. > > + */ > > + pause_graph_tracing(); > > + > > return 1; > > } > > NOKPROBE_SYMBOL(setjmp_pre_handler); > > @@ -635,6 +644,8 @@ int longjmp_break_handler(struct kprobe *p, struct > > pt_regs *regs) > > * saved regs... > > */ > > memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs)); > > + /* It's OK to start function graph tracing again */ > > + unpause_graph_tracing(); > > preempt_enable_no_resched(); > > return 1; > > } > > -- > > 2.12.2 > > > >