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Date: Wed, 1 Nov 2017 22:17:26 +0100 From: Willy Tarreau <w@....eu> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, linux@...ck-us.net Cc: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>, Michael Ellerman <mpe@...erman.id.au>, Willy Tarreau <w@....eu> Subject: [PATCH 3.10 026/139] powerpc/kprobes: Pause function_graph tracing during jprobes handling From: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> commit a9f8553e935f26cb5447f67e280946b0923cd2dc upstream. 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: 6794c78243bf ("powerpc64: port of the function graph tracer") Cc: stable@...r.kernel.org Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com> Acked-by: Masami Hiramatsu <mhiramat@...nel.org> Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org> Signed-off-by: Michael Ellerman <mpe@...erman.id.au> Signed-off-by: Willy Tarreau <w@....eu> --- 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 11f5b03..762c10d 100644 --- a/arch/powerpc/kernel/kprobes.c +++ b/arch/powerpc/kernel/kprobes.c @@ -529,6 +529,15 @@ int __kprobes 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; } @@ -551,6 +560,8 @@ int __kprobes 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; } -- 2.8.0.rc2.1.gbe9624a
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