From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758111AbcAKDae (ORCPT ); Sun, 10 Jan 2016 22:30:34 -0500 Received: from ozlabs.org ([103.22.144.67]:34339 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757742AbcAKDac (ORCPT ); Sun, 10 Jan 2016 22:30:32 -0500 Message-ID: <1452483031.31943.6.camel@ellerman.id.au> Subject: Re: [RFC][PATCH] ppc: Implement save_stack_trace_regs() From: Michael Ellerman To: Steven Rostedt Cc: LKML , linuxppc-dev@lists.ozlabs.org, chuhu@redhat.com Date: Mon, 11 Jan 2016 14:30:31 +1100 In-Reply-To: <20160108175053.04e4296f@gandalf.local.home> References: <20151208135056.718b7668@gandalf.local.home> <1449620422.6028.6.camel@ellerman.id.au> <20151208192844.70fb33e6@gandalf.local.home> <1449622985.6028.8.camel@ellerman.id.au> <20151216122419.385f1306@gandalf.local.home> <20160108175053.04e4296f@gandalf.local.home> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5-1ubuntu3.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2016-01-08 at 17:50 -0500, Steven Rostedt wrote: > On Wed, 16 Dec 2015 12:24:19 -0500 > Steven Rostedt wrote: > > On Wed, 09 Dec 2015 12:03:05 +1100 > > Michael Ellerman wrote: > > > > > Should I take this via powerpc or do you want it to go in via tracing? > > > > > > > > You can take it. And you can replace the PT_R1 if you want. I just > > > > noticed that it was defined, and I try to use macro names instead of > > > > hard coded numbers. I was actually looking for a "PT_SP" :-) > > > > > > OK thanks. > > > > > > Looks like we actually have: > > > > > > #define kernel_stack_pointer(regs) ((regs)->gpr[1]) > > > > > > So that would be the most self documenting way to do it I guess, though I've > > > never actually seen that macro used anywhere before :) > > > > Hi, > > > > Are you going to take this, or do you want me to? Sorry, yep I'll take it. I trimmed the change log a bit, final version below. cheers powerpc: Implement save_stack_trace_regs() to enable kprobe stack tracing It has come to my attention that kprobe event stack tracing does not work on powerpc. You can see with the following: # cd /sys/kernel/debug/tracing # echo stacktrace > trace_options # echo 'p kfree' > kprobe_events # echo 1 > events/kprobes/enable Will print the following warning: save_stack_trace_regs() not implemented yet. Although save_stack_trace() (which normal event stack traces use) is implemented, save_stack_trace_regs() which kprobe events use is not. This is a cheap attempt to implement that function. Note, This may have issues if a task tries to get a stack trace from another task with its regs, because it just passes in "current" to save_context_stack(). But this does solve the issue with stack tracing kprobe events. Reported-by: Chunyu Hu Signed-off-by: Steven Rostedt Signed-off-by: Michael Ellerman diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c index ea43a347a104..4f24606afc3f 100644 --- a/arch/powerpc/kernel/stacktrace.c +++ b/arch/powerpc/kernel/stacktrace.c @@ -61,3 +61,10 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) save_context_stack(trace, tsk->thread.ksp, tsk, 0); } EXPORT_SYMBOL_GPL(save_stack_trace_tsk); + +void +save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace) +{ + save_context_stack(trace, regs->gpr[1], current, 0); +} +EXPORT_SYMBOL_GPL(save_stack_trace_regs);