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Message-ID: <CAM9d7cj1v09Q0_AF2Oaa4+UU_YWB8OaaoeOZ-igoMTTFg4VZGg@mail.gmail.com>
Date: Sun, 5 Feb 2023 18:44:11 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Yang Jihong <yangjihong1@...wei.com>
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 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,
> 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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