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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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