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Message-ID: <29a8e0bc-e90b-b371-962b-58a4b8c87f20@huawei.com> Date: Sat, 28 Jan 2023 09:27:04 +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, 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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