From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752957AbbJONWJ (ORCPT ); Thu, 15 Oct 2015 09:22:09 -0400 Received: from mail-pa0-f47.google.com ([209.85.220.47]:35779 "EHLO mail-pa0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751514AbbJONWH (ORCPT ); Thu, 15 Oct 2015 09:22:07 -0400 From: Jungseok Lee To: catalin.marinas@arm.com, will.deacon@arm.com, linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, AKASHI Takahiro , James Morse , Mark Rutland Subject: [PATCH] arm64: Synchonise dump_backtrace() with perf callchain Date: Thu, 15 Oct 2015 13:21:54 +0000 Message-Id: <1444915314-13649-1-git-send-email-jungseoklee85@gmail.com> X-Mailer: git-send-email 2.5.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org dump_backtrace() has its own backtrace logic unlike perf callchain which relies on walk_stackframe(). They behave differently when a symbol is recorded. Perf writes it down *before* calling unwind_frame(), but dump_backtrace() prints it out *after* unwind_frame(). As a result, the last valid symbol is not added to a list in case of dump_backtrace(). This patch catches up the last symbol as synchronising dump_backtrace() with perf callchain. However, the patch does not cover a case where MMU is disabled. That is, a physical address can be stored in stack frame, but it's not handled. For example, a swapper process falls into this case. Unlike a swapper from a secondary core, a swapper on a boot cpu, which starting from __mmap_switched(), can't be tracked down with a simple conversion, phys_to_virt(), because PC is retrieved from LR - 4, not LR. It is a big tradeoff to change both head.S and unwind_frame() structure for a few of symbols in *.S, so this hunk does not take care of the case. Cc: AKASHI Takahiro Cc: James Morse Cc: Mark Rutland Signed-off-by: Jungseok Lee --- arch/arm64/kernel/traps.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index f93aae5..4ddb928 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -103,12 +103,13 @@ static void dump_mem(const char *lvl, const char *str, unsigned long bottom, set_fs(fs); } -static void dump_backtrace_entry(unsigned long where, unsigned long stack) +static void dump_backtrace_entry(unsigned long where) { + /* + * The highest stack frame of a swapper process stores PC in a form + * of physical address, but this case is not handled. + */ print_ip_sym(where); - if (in_exception_text(where)) - dump_mem("", "Exception stack", stack, - stack + sizeof(struct pt_regs), false); } static void dump_instr(const char *lvl, struct pt_regs *regs) @@ -172,12 +173,17 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) pr_emerg("Call trace:\n"); while (1) { unsigned long where = frame.pc; + unsigned long stack; int ret; + dump_backtrace_entry(where); ret = unwind_frame(&frame); if (ret < 0) break; - dump_backtrace_entry(where, frame.sp); + stack = frame.sp; + if (in_exception_text(where)) + dump_mem("", "Exception stack", stack, + stack + sizeof(struct pt_regs), false); } } -- 2.5.0