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Message-ID: <ee213278-7e76-586b-0564-843dc7a3c84f@huawei.com>
Date: Mon, 6 Feb 2023 09:28:51 +0800
From: Yang Jihong <yangjihong1@...wei.com>
To: <acme@...nel.org>, <namhyung@...nel.org>,
<linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <peterz@...radead.org>, <mingo@...hat.com>, <mark.rutland@....com>,
<alexander.shishkin@...ux.intel.com>, <jolsa@...nel.org>,
<jiwei.sun@...driver.com>
Subject: Re: [PATCH v3] perf record: Fix segfault with --overwrite and
--max-size
Hello,
Ping again, please take time to review, thanks.
Thanks,
Yang
On 2023/1/28 9:27, Yang Jihong wrote:
> Hello,
>
> The data written by the thread (data.X file) has been saved as
> recommended in v2 patch. Please check whether it is feasible. Thank you.
>
> Thanks,
> Yang
>
> On 2023/1/13 15:38, Yang Jihong wrote:
>> 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 1K -a -- sleep 1
>> [ perf record: Woken up 1 times to write data ]
>> perf: Segmentation fault
>> Obtained 12 stack frames.
>> ./perf/perf(+0x197673) [0x55f99710b673]
>> /lib/x86_64-linux-gnu/libc.so.6(+0x3ef0f) [0x7fa45f3cff0f]
>> ./perf/perf(+0x8eb40) [0x55f997002b40]
>> ./perf/perf(+0x1f6882) [0x55f99716a882]
>> ./perf/perf(+0x794c2) [0x55f996fed4c2]
>> ./perf/perf(+0x7b7c7) [0x55f996fef7c7]
>> ./perf/perf(+0x9074b) [0x55f99700474b]
>> ./perf/perf(+0x12e23c) [0x55f9970a223c]
>> ./perf/perf(+0x12e54a) [0x55f9970a254a]
>> ./perf/perf(+0x7db60) [0x55f996ff1b60]
>> /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe6)
>> [0x7fa45f3b2c86]
>> ./perf/perf(+0x7dfe9) [0x55f996ff1fe9]
>> Segmentation fault (core dumped)
>>
>> backtrace of the core file is as follows:
>>
>> (gdb) bt
>> #0 record__bytes_written (rec=0x55f99755a200 <record>) at
>> builtin-record.c:234
>> #1 record__output_max_size_exceeded (rec=0x55f99755a200 <record>)
>> at builtin-record.c:242
>> #2 record__write (map=0x0, size=12816, bf=0x55f9978da2e0,
>> rec=0x55f99755a200 <record>) at builtin-record.c:263
>> #3 process_synthesized_event (tool=tool@...ry=0x55f99755a200
>> <record>, event=event@...ry=0x55f9978da2e0, sample=sample@...ry=0x0,
>> machine=machine@...ry=0x55f997893658) at builtin-record.c:618
>> #4 0x000055f99716a883 in __perf_event__synthesize_id_index
>> (tool=tool@...ry=0x55f99755a200 <record>,
>> process=process@...ry=0x55f997002aa0 <process_synthesized_event>,
>> evlist=0x55f9978928b0, machine=machine@...ry=0x55f997893658,
>> from=from@...ry=0) at util/synthetic-events.c:1895
>> #5 0x000055f99716a91f in perf_event__synthesize_id_index
>> (tool=tool@...ry=0x55f99755a200 <record>,
>> process=process@...ry=0x55f997002aa0 <process_synthesized_event>,
>> evlist=<optimized out>, machine=machine@...ry=0x55f997893658)
>> at util/synthetic-events.c:1905
>> #6 0x000055f996fed4c3 in record__synthesize (tail=tail@...ry=true,
>> rec=0x55f99755a200 <record>) at builtin-record.c:1997
>> #7 0x000055f996fef7c8 in __cmd_record (argc=argc@...ry=2,
>> argv=argv@...ry=0x7ffc67551260, rec=0x55f99755a200 <record>) at
>> builtin-record.c:2802
>> #8 0x000055f99700474c in cmd_record (argc=<optimized out>,
>> argv=0x7ffc67551260) at builtin-record.c:4258
>> #9 0x000055f9970a223d in run_builtin (p=0x55f997564d88
>> <commands+264>, argc=10, argv=0x7ffc67551260) at perf.c:330
>> #10 0x000055f9970a254b in handle_internal_command (argc=10,
>> argv=0x7ffc67551260) at perf.c:384
>> #11 0x000055f996ff1b61 in run_argv (argcp=<synthetic pointer>,
>> argv=<synthetic pointer>) at perf.c:428
>> #12 main (argc=<optimized out>, argv=0x7ffc67551260) 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 add a member variable "thread_bytes_written" in the struct "record"
>> to save the data size written by the threads.
>>
>> Fixes: 6d57581659f7 ("perf record: Add support for limit perf output
>> file size")
>> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
>> ---
>>
>> Changes since v2:
>> - Save data size written by threads to calculate the correct total
>> data size.
>> - Update commit message.
>>
>> 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.
>>
>> tools/perf/builtin-record.c | 16 ++++++----------
>> 1 file changed, 6 insertions(+), 10 deletions(-)
>>
>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
>> index 29dcd454b8e2..8374117e66f6 100644
>> --- a/tools/perf/builtin-record.c
>> +++ b/tools/perf/builtin-record.c
>> @@ -154,6 +154,7 @@ struct record {
>> struct perf_tool tool;
>> struct record_opts opts;
>> u64 bytes_written;
>> + u64 thread_bytes_written;
>> struct perf_data data;
>> struct auxtrace_record *itr;
>> struct evlist *evlist;
>> @@ -226,14 +227,7 @@ static bool switch_output_time(struct record *rec)
>> static u64 record__bytes_written(struct record *rec)
>> {
>> - int t;
>> - u64 bytes_written = rec->bytes_written;
>> - struct record_thread *thread_data = rec->thread_data;
>> -
>> - for (t = 0; t < rec->nr_threads; t++)
>> - bytes_written += thread_data[t].bytes_written;
>> -
>> - return bytes_written;
>> + return rec->bytes_written + rec->thread_bytes_written;
>> }
>> static bool record__output_max_size_exceeded(struct record *rec)
>> @@ -255,10 +249,12 @@ static int record__write(struct record *rec,
>> struct mmap *map __maybe_unused,
>> return -1;
>> }
>> - if (map && map->file)
>> + if (map && map->file) {
>> thread->bytes_written += size;
>> - else
>> + rec->thread_bytes_written += size;
>> + } else {
>> rec->bytes_written += size;
>> + }
>> if (record__output_max_size_exceeded(rec) && !done) {
>> fprintf(stderr, "[ perf record: perf size limit reached (%"
>> PRIu64 " KB),"
>>
>
> .
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