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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F083BC54EBE for ; Fri, 13 Jan 2023 07:05:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240697AbjAMHFB (ORCPT ); Fri, 13 Jan 2023 02:05:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241584AbjAMHE2 (ORCPT ); Fri, 13 Jan 2023 02:04:28 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0ADFF76223; Thu, 12 Jan 2023 22:53:10 -0800 (PST) Received: from kwepemm600003.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4NtXC56n2SzJrJR; Fri, 13 Jan 2023 14:51:45 +0800 (CST) Received: from [10.67.111.205] (10.67.111.205) by kwepemm600003.china.huawei.com (7.193.23.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.34; Fri, 13 Jan 2023 14:53:05 +0800 Subject: Re: [PATCH v2] perf record: Fix coredump with --overwrite and --max-size To: Namhyung Kim CC: Arnaldo Carvalho de Melo , , , , , , , , References: <20221229124728.66515-1-yangjihong1@huawei.com> From: Yang Jihong Message-ID: <58686bd7-6789-d1c4-a560-b8b0670212f3@huawei.com> Date: Fri, 13 Jan 2023 14:53:04 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.111.205] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemm600003.china.huawei.com (7.193.23.202) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On 2023/1/11 3:21, Namhyung Kim wrote: > On Sun, Jan 8, 2023 at 6:47 PM Yang Jihong wrote: >> >> Hello, >> >> On 2023/1/7 5:12, Namhyung Kim wrote: >>> Hello, >>> >>> On Wed, Jan 4, 2023 at 8:09 PM Yang Jihong wrote: >>>> >>>> Hello, >>>> >>>> On 2023/1/4 0:50, Namhyung Kim wrote: >>>>> On Mon, Jan 2, 2023 at 8:20 AM Arnaldo Carvalho de Melo wrote: >>>>>> >>>>>> Em Thu, Dec 29, 2022 at 12:47:28PM +0000, Yang Jihong escreveu: >>>>>>> When --overwrite and --max-size options of perf record are used together, >>>>>>> a segmentation fault occurs. The following is an example: >>>>>>> >>>>>>> # perf record -e sched:sched* --overwrite --max-size 1M -a -- sleep 1 >>>>>>> [ perf record: Woken up 1 times to write data ] >>>>>>> perf: Segmentation fault >>>>>>> Obtained 1 stack frames. >>>>>>> [0xc4c67f] >>>>>>> Segmentation fault (core dumped) >>>>>>> >>>>>>> backtrace of the core file is as follows: >>>>>>> >>>>>>> #0 0x0000000000417990 in process_locked_synthesized_event (tool=0x0, event=0x15, sample=0x1de0, machine=0xf8) at builtin-record.c:630 >>>>>>> #1 0x000000000057ee53 in perf_event__synthesize_threads (nr_threads_synthesize=21, mmap_data=, needs_mmap=, machine=0x17ad9b0, process=, tool=0x0) at util/synthetic-events.c:1950 >>>>>>> #2 __machine__synthesize_threads (nr_threads_synthesize=0, data_mmap=, needs_mmap=, process=, threads=0x8, target=0x8, tool=0x0, machine=0x17ad9b0) at util/synthetic-events.c:1936 >>>>>>> #3 machine__synthesize_threads (machine=0x17ad9b0, target=0x8, threads=0x8, needs_mmap=, data_mmap=, nr_threads_synthesize=0) at util/synthetic-events.c:1947 >>>>>>> #4 0x000000000040165d in record__synthesize (tail=, rec=0xbe2520 ) at builtin-record.c:2010 >>>>>>> #5 0x0000000000403989 in __cmd_record (argc=, argv=, rec=0xbe2520 ) at builtin-record.c:2810 >>>>>>> #6 0x00000000004196ba in record__init_thread_user_masks (rec=0xbe2520 , cpus=0x17a65f0) at builtin-record.c:3837 >>>>>>> #7 record__init_thread_masks (rec=0xbe2520 ) at builtin-record.c:3938 >>>>>>> #8 cmd_record (argc=1, argv=0x7ffdd692dc60) at builtin-record.c:4241 >>>>>>> #9 0x00000000004b701d in pager_command_config (var=0x0, value=0x15 , data=0x1de0) at perf.c:117 >>>>>>> #10 0x00000000004b732b in get_leaf_frame_caller_aarch64 (sample=0xfffffffb, thread=0x0, usr_idx=) at util/arm64-frame-pointer-unwind-support.c:56 >>>>>>> #11 0x0000000000406331 in execv_dashed_external (argv=0x7ffdd692d9e8) at perf.c:410 >>>>>>> #12 run_argv (argcp=, argv=) at perf.c:431 >>>>>>> #13 main (argc=, argv=0x7ffdd692d9e8) at perf.c:562 >>>>>>> >>>>>>> The reason is that record__bytes_written accesses the freed memory rec->thread_data, >>>>>>> The process is as follows: >>>>>>> __cmd_record >>>>>>> -> record__free_thread_data >>>>>>> -> zfree(&rec->thread_data) // free rec->thread_data >>>>>>> -> record__synthesize >>>>>>> -> perf_event__synthesize_id_index >>>>>>> -> process_synthesized_event >>>>>>> -> record__write >>>>>>> -> record__bytes_written // access rec->thread_data >>>>>>> >>>>>>> we only need to check the value of done first. >>>>>>> Also add variable check in record__bytes_written for code hardening, >>>>>>> and save bytes_written separately to reduce one calculation. >>>>>>> >>>>>>> Fixes: 6d57581659f7 ("perf record: Add support for limit perf output file size") >>>>>>> Signed-off-by: Yang Jihong >>>>>>> --- >>>>>>> >>>>>>> Changes since v1: >>>>>>> - Add variable check in record__bytes_written for code hardening. >>>>>>> - Save bytes_written separately to reduce one calculation. >>>>>>> - Remove rec->opts.tail_synthesize check. >>>>>> >>>>>> Namhyung, are you ok with this now? >>>>>> >>>>>> - Arnaldo >>>>>> >>>>>>> tools/perf/builtin-record.c | 26 +++++++++++++++++--------- >>>>>>> 1 file changed, 17 insertions(+), 9 deletions(-) >>>>>>> >>>>>>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c >>>>>>> index 29dcd454b8e2..acba9e43e519 100644 >>>>>>> --- a/tools/perf/builtin-record.c >>>>>>> +++ b/tools/perf/builtin-record.c >>>>>>> @@ -230,16 +230,29 @@ static u64 record__bytes_written(struct record *rec) >>>>>>> u64 bytes_written = rec->bytes_written; >>>>>>> struct record_thread *thread_data = rec->thread_data; >>>>>>> >>>>>>> + if (thread_data == NULL) >>>>>>> + return bytes_written; >>>>>>> + >>>>> >>>>> Then it won't count bytes written by threads, right? >>>>> I think it needs to be saved somewhere. >>>>> >>>> I'm not sure here. Can you explain it more clearly, thanks :) >>>> I can modify it accordingly. >>>> >>>> I think if thread_data == NULL, it is not thread data. >>>> In this case, we just return rec->bytes_written. >>> >>> It can be thread data but freed before tail synthesis, right? >>> In that case, I think it needs to add bytes_written by threads >>> to calculate the correct data size. >> Em... In the __cmd_record function, record__stop_threads is called >> before record__free_thread_data, so if the thread has been freed, there >> will be no thread data. >> I think it's okay to ignore the situation you mentioned above. > > Right, the thread data is already freed, but we need the size. > > I think it didn't (and won't) update to rec->bytes_written for the data > written by the threads (data.X file) because it's only for the main > 'data' file. So record__bytes_written() will return a smaller number > after the threads are gone. But I think it should return the total > data size. > Yes, the total data size including data.X file should be returned here to fit the semantics, so there's a problem here, too. will fix in next version. Thanks, Yang