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Date: Mon, 6 Feb 2023 11:40:32 +0800
From: Yang Jihong <yangjihong1@...wei.com>
To: Namhyung Kim <namhyung@...nel.org>
CC: <acme@...nel.org>, <linux-perf-users@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <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,
On 2023/2/6 10:44, Namhyung Kim wrote:
> Hello,
>
> On Sun, Feb 5, 2023 at 5:29 PM Yang Jihong <yangjihong1@...wei.com> wrote:
>>
>> Hello,
>>
>> Ping again, please take time to review, thanks.
>
> Sorry for the late reply. Now it looks good to me.
Thanks for the review.
Thanks,
Yang.
>
>>
>>
>> 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>
>
> Acked-by: Namhyung Kim <namhyung@...nel.org>
>
> Thanks,
> Namhyung
>
>
>>>> ---
>>>>
>>>> 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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