From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2899BC3A59B for ; Mon, 19 Aug 2019 08:18:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 02F7420874 for ; Mon, 19 Aug 2019 08:18:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727071AbfHSISI (ORCPT ); Mon, 19 Aug 2019 04:18:08 -0400 Received: from smtp2200-217.mail.aliyun.com ([121.197.200.217]:51141 "EHLO smtp2200-217.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726366AbfHSISH (ORCPT ); Mon, 19 Aug 2019 04:18:07 -0400 X-Alimail-AntiSpam: AC=CONTINUE;BC=0.07575988|-1;CH=green;DM=CONTINUE|CONTINUE|true|0.0307753-0.00242969-0.966795;FP=0|0|0|0|0|0|0|0;HT=e02c03302;MF=han_mao@c-sky.com;NM=1;PH=DS;RN=3;RT=3;SR=0;TI=SMTPD_---.FEWH.Ih_1566202681; Received: from localhost(mailfrom:han_mao@c-sky.com fp:SMTPD_---.FEWH.Ih_1566202681) by smtp.aliyun-inc.com(10.147.40.233); Mon, 19 Aug 2019 16:18:01 +0800 Date: Mon, 19 Aug 2019 16:18:01 +0800 From: Mao Han To: Paul Walmsley Cc: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH V3 0/3] riscv: Add perf callchain support Message-ID: <20190819081758.GA15999@vmh-VirtualBox> References: MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="zhXaljGHf11kAtnf" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --zhXaljGHf11kAtnf Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Hi Paul, On Fri, Aug 16, 2019 at 10:14:01AM -0700, Paul Walmsley wrote: > Hello Mao Han, > > On Fri, 17 May 2019, Mao Han wrote: > > > This patch set add perf callchain(FP/DWARF) support for RISC-V. > > It comes from the csky version callchain support with some > > slight modifications. The patchset base on Linux 5.1. > > > > CC: Palmer Dabbelt > > CC: linux-riscv > > CC: Christoph Hellwig > > CC: Guo Ren > > I tried these patches on v5.3-rc4, both on the HiFive Unleashed board > with a Debian-based rootfs and QEMU rv64 with a Fedora-based rootfs. For > QEMU, I used defconfig, and for the HiFive Unleashed, I added a few more > Kconfig directives; and on both, I enabled CONFIG_PERF_EVENTS. I built > the perf tools from the kernel tree. > > Upon running "/root/bin/perf record -e cpu-clock --call-graph fp > /bin/ls", I see the backtraces below. The first is on the HiFive > Unleashed, the second is on QEMU. > > Could you take a look and tell me if you see similar issues? And if not, > could you please walk me through your process for testing these patches on > rv64, so I can reproduce it here? > I'v tried the command line above and got similar issues with probability. unwind_frame_kernel can not stop unwind when fp is a quite large value(like 0x70aac93ff0eff584) which can pass the simple stack check. if (kstack_end((void *)frame->fp)) return -EPERM; if (frame->fp & 0x3 || frame->fp < TASK_SIZE) return -EPERM; handle_exception from arch/riscv/kernel/entry.S will use s0(fp) as temp register. The context for this frame is unpredictable. We may add more strict check in unwind_frame_kernel or keep s0 always 0 in handle_exception to fix this issue. Breakpoint 1, unwind_frame_kernel (frame=0xffffffe0000057a0 ) at arch/riscv/kernel/perf_callchain.c:14 14 { 1: /x *frame = {fp = 0xffffffe000005ee0, ra = 0xffffffe000124c90} (gdb) Continuing. Breakpoint 1, unwind_frame_kernel (frame=0xffffffe0000057a0 ) at arch/riscv/kernel/perf_callchain.c:14 14 { 1: /x *frame = {fp = 0xffffffe000124c74, ra = 0xffffffe000036cba} (gdb) Continuing. Breakpoint 1, unwind_frame_kernel (frame=0xffffffe0000057a0 ) at arch/riscv/kernel/perf_callchain.c:14 14 { 1: /x *frame = {fp = 0x70aac57ff0eff584, ra = 0x8082614d64ea740a} (gdb) Some time perf record can output perf.data correct. something like: # perf record -e cpu-clock --call-graph fp ls perf.data [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.012 MB perf.data (102 samples) ] # # perf report # To display the perf.data header info, please use --header/--header-only options. # # # Total Lost Samples: 0 # # Samples: 102 of event 'cpu-clock' # Event count (approx.): 25500000 # # Children Self Command Shared Object Symbol # ........ ........ ....... ................. ................................. # 30.39% 0.00% ls [kernel.kallsyms] [k] ret_from_exception | ---ret_from_exception | |--16.67%--do_page_fault | handle_mm_fault | __handle_mm_fault | | | |--9.80%--filemap_map_pages | | | | | |--3.92%--alloc_set_pte | | | page_add_file_rmap | | | | | --3.92%--filemap_map_pages | | | --0.98%--__do_fault | |--8.82%--schedule | __sched_text_start | finish_task_switch | --4.90%--__kprobes_text_start irq_exit irq_exit 28.43% 0.00% ls [kernel.kallsyms] [k] ret_from_syscall | ---ret_from_syscall | |--15.69%--__se_sys_execve | __do_execve_file | search_binary_handler.part.7 I previous tested these patch with a program(callchain_test.c) mostly running in userspace, so I didn't got this issues. Thanks, Mao Han --zhXaljGHf11kAtnf Content-Type: text/x-csrc; charset=us-ascii Content-Disposition: attachment; filename="callchain_test.c" #include void test_4(void) { volatile int i, j; for(i = 0; i < 10000000; i++) j=i; } void test_3(void) { volatile int i, j; test_4(); for(i = 0; i < 3000; i++) j=i; } void test_2(void) { volatile int i, j; test_3(); for(i = 0; i < 3000; i++) j=i; } void test_1(void) { volatile int i, j; test_2(); for(i = 0; i < 3000; i++) j=i; } int main(void) { test_1(); return 0; } --zhXaljGHf11kAtnf--