Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752207AbbKAIA5 (ORCPT ); Sun, 1 Nov 2015 03:00:57 -0500 Received: from mail-pa0-f52.google.com ([209.85.220.52]:33742 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750874AbbKAIAQ convert rfc822-to-8bit (ORCPT ); Sun, 1 Nov 2015 03:00:16 -0500 Subject: Re: [PATCH v4 3/6] arm64: ftrace: fix a stack tracer's output under function graph tracer Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: text/plain; charset=us-ascii From: Jungseok Lee In-Reply-To: <1446182741-31019-4-git-send-email-takahiro.akashi@linaro.org> Date: Sun, 1 Nov 2015 17:00:10 +0900 Cc: catalin.marinas@arm.com, will.deacon@arm.com, rostedt@goodmis.org, olof@lixom.net, broonie@kernel.org, david.griego@linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8BIT Message-Id: References: <1446182741-31019-1-git-send-email-takahiro.akashi@linaro.org> <1446182741-31019-4-git-send-email-takahiro.akashi@linaro.org> To: AKASHI Takahiro X-Mailer: Apple Mail (2.1283) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2660 Lines: 80 On Oct 30, 2015, at 2:25 PM, AKASHI Takahiro wrote: Hi Akashi, > Function graph tracer modifies a return address (LR) in a stack frame > to hook a function return. This will result in many useless entries > (return_to_handler) showing up in a stack tracer's output. > > This patch replaces such entries with originals values preserved in > current->ret_stack[]. > > Signed-off-by: AKASHI Takahiro > --- > arch/arm64/include/asm/ftrace.h | 2 ++ > arch/arm64/kernel/stacktrace.c | 21 +++++++++++++++++++++ > 2 files changed, 23 insertions(+) > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index 2b43e20..b7d597c 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -29,6 +29,8 @@ struct dyn_arch_ftrace { > > extern unsigned long ftrace_graph_call; > > +extern void return_to_handler(void); > + > static inline unsigned long ftrace_call_adjust(unsigned long addr) > { > /* > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index bc0689a..631c49d 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -17,6 +17,7 @@ > */ > #include > #include > +#include > #include > #include > > @@ -78,6 +79,9 @@ struct stack_trace_data { > struct stack_trace *trace; > unsigned int no_sched_functions; > unsigned int skip; > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > + unsigned int ret_stack_index; > +#endif > }; > > static int save_trace(struct stackframe *frame, void *d) > @@ -86,6 +90,20 @@ static int save_trace(struct stackframe *frame, void *d) > struct stack_trace *trace = data->trace; > unsigned long addr = frame->pc; > > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > + if (addr == (unsigned long)return_to_handler - AARCH64_INSN_SIZE) { > + /* > + * This is a case where function graph tracer has > + * modified a return address (LR) in a stack frame > + * to hook a function return. > + * So replace it to an original value. > + */ > + frame->pc = addr = > + current->ret_stack[data->ret_stack_index--].ret > + - AARCH64_INSN_SIZE; > + } > +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ > + This hunk would be affected as the commit, "ARM64: unwind: Fix PC calculation", e306dfd0, has been reverted. Best Regards Jungseok Lee-- 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/