Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753231AbbEHPiG (ORCPT ); Fri, 8 May 2015 11:38:06 -0400 Received: from foss.arm.com ([217.140.101.70]:53352 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752699AbbEHPiC (ORCPT ); Fri, 8 May 2015 11:38:02 -0400 Date: Fri, 8 May 2015 16:37:58 +0100 From: Will Deacon To: Hou Pengyang Cc: "a.p.zijlstra@chello.nl" , "paulus@samba.org" , "acme@kernel.org" , "mingo@redhat.com" , Catalin Marinas , "wannan0@huawei.com" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v4 2/2] arm64: perf: Fix callchain parse error with kernel tracepoint events Message-ID: <20150508153758.GG25587@arm.com> References: <1431063784-137600-1-git-send-email-houpengyang@huawei.com> <1431063784-137600-3-git-send-email-houpengyang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1431063784-137600-3-git-send-email-houpengyang@huawei.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2695 Lines: 65 On Fri, May 08, 2015 at 06:43:04AM +0100, Hou Pengyang wrote: > For ARM64, when tracing with tracepoint events, the IP and pstate are set > to 0, preventing the perf code parsing the callchain and resolving the > symbols correctly. > > ./perf record -e sched:sched_switch -g --call-graph dwarf ls > [ perf record: Captured and wrote 0.146 MB perf.data ] > ./perf report -f > Samples: 194 of event 'sched:sched_switch', Event count (approx.): 194 > Children Self Command Shared Object Symbol > 100.00% 100.00% ls [unknown] [.] 0000000000000000 > > The fix is to implement perf_arch_fetch_caller_regs for ARM64, which fills > several necessary registers used for callchain unwinding, including pc,sp, > fp and spsr . > > With this patch, callchain can be parsed correctly as follows: > > ...... > + 2.63% 0.00% ls [kernel.kallsyms] [k] vfs_symlink > + 2.63% 0.00% ls [kernel.kallsyms] [k] follow_down > + 2.63% 0.00% ls [kernel.kallsyms] [k] pfkey_get > + 2.63% 0.00% ls [kernel.kallsyms] [k] do_execveat_common.isra.33 > - 2.63% 0.00% ls [kernel.kallsyms] [k] pfkey_send_policy_notify > pfkey_send_policy_notify > pfkey_get > v9fs_vfs_rename > page_follow_link_light > link_path_walk > el0_svc_naked > ....... > > Signed-off-by: Hou Pengyang > --- > arch/arm64/include/asm/perf_event.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/arch/arm64/include/asm/perf_event.h b/arch/arm64/include/asm/perf_event.h > index d26d1d5..6471773 100644 > --- a/arch/arm64/include/asm/perf_event.h > +++ b/arch/arm64/include/asm/perf_event.h > @@ -24,4 +24,11 @@ extern unsigned long perf_misc_flags(struct pt_regs *regs); > #define perf_misc_flags(regs) perf_misc_flags(regs) > #endif > > +#define perf_arch_fetch_caller_regs(regs, __ip) { \ > + (regs)->pc = (__ip); \ > + (regs)->regs[AARCH64_INSN_REG_FP] = (unsigned long) __builtin_frame_address(0); \ Just a minor thing, but I'd rather we explicitly used '29' as the index here. The AARCH64_INSN_REG_FP is really for the instruction generation code used by BPF and I think it's better to be explicit about the register number here. Anyway, I've queued your arch/arm/ patch and Catalin can take this one for 4.2 once you've made the small change above and added my Ack. Thanks, Will -- 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/