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> --- 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