Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756050AbbGPO3B (ORCPT ); Thu, 16 Jul 2015 10:29:01 -0400 Received: from foss.arm.com ([217.140.101.70]:43997 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755887AbbGPO27 (ORCPT ); Thu, 16 Jul 2015 10:28:59 -0400 Date: Thu, 16 Jul 2015 15:28:34 +0100 From: Mark Rutland To: AKASHI Takahiro Cc: Steven Rostedt , Jungseok Lee , Catalin Marinas , Will Deacon , "linux-kernel@vger.kernel.org" , "broonie@kernel.org" , "david.griego@linaro.org" , "olof@lixom.net" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [RFC 2/3] arm64: refactor save_stack_trace() Message-ID: <20150716142834.GD28631@leverpostej> References: <1436765375-7119-3-git-send-email-takahiro.akashi@linaro.org> <20150714093154.4d73e551@gandalf.local.home> <55A5A75A.1060401@linaro.org> <20150714225105.6c1e4f15@gandalf.local.home> <55A646EE.6030402@linaro.org> <20150715105536.42949ea9@gandalf.local.home> <20150715121337.3b31aa84@gandalf.local.home> <55A6FA82.9000901@linaro.org> <55A703F3.8050203@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55A703F3.8050203@linaro.org> Thread-Topic: [RFC 2/3] arm64: refactor save_stack_trace() Accept-Language: en-GB, en-US Content-Language: en-US User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3241 Lines: 97 On Thu, Jul 16, 2015 at 02:08:03AM +0100, AKASHI Takahiro wrote: > On 07/16/2015 09:27 AM, AKASHI Takahiro wrote: > > On 07/16/2015 01:13 AM, Steven Rostedt wrote: > >> On Wed, 15 Jul 2015 10:55:36 -0400 > >> Steven Rostedt wrote: > >> > >> > >>> I'll take a look at it and try to clean up the code. > >> > >> Does the following patch make sense for you? > > > > Looks nice. The patch greatly simplifies changes on arm64 side. > > As follows: > > - Takahiro AKASHI > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index c5534fa..868d6f1 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -15,6 +15,7 @@ > > #define MCOUNT_ADDR ((unsigned long)_mcount) > #define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE > +#define FTRACE_STACK_FRAME_OFFSET 4 /* sync it up with stacktrace.c */ Is there any reason we couldn't have the arch code dump the stack depth for each function when it walks the stack to generate the stack trace? That means we can provide a more precise result (because we know the layour of our own stackframes), and we only need walk the stack once to do so. The downside is that we need a new function per-arch to do so. Mark. > > #ifndef __ASSEMBLY__ > #include > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index 1da6029..2c1bf7d 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -260,6 +260,13 @@ static inline void ftrace_kill(void) { } > #endif /* CONFIG_FUNCTION_TRACER */ > > #ifdef CONFIG_STACK_TRACER > +/* > + * the offset value to add to return address from save_stack_trace() > + */ > +#ifndef FTRACE_STACK_FRAME_OFFSET > +#define FTRACE_STACK_FRAME_OFFSET 0 > +#endif > + > extern int stack_tracer_enabled; > int > stack_trace_sysctl(struct ctl_table *table, int write, > diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c > index 9384647..c5b9748 100644 > --- a/kernel/trace/trace_stack.c > +++ b/kernel/trace/trace_stack.c > @@ -105,7 +105,7 @@ check_stack(unsigned long ip, unsigned long *stack) > > /* Skip over the overhead of the stack tracer itself */ > for (i = 0; i < max_stack_trace.nr_entries; i++) { > - if (stack_dump_trace[i] == ip) > + if ((stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET) == ip) > break; > } > > @@ -131,7 +131,8 @@ check_stack(unsigned long ip, unsigned long *stack) > p = start; > > for (; p < top && i < max_stack_trace.nr_entries; p++) { > - if (*p == stack_dump_trace[i]) { > + if (*p == (stack_dump_trace[i] > + + FTRACE_STACK_FRAME_OFFSET)) { > stack_dump_trace[x] = stack_dump_trace[i++]; > this_size = stack_dump_index[x++] = > (top - p) * sizeof(unsigned long); > -- > 1.7.9.5 > > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/