Messages in this thread | | | From | Namhyung Kim <> | Date | Tue, 10 Jan 2023 11:21:54 -0800 | Subject | Re: [PATCH v2] perf record: Fix coredump with --overwrite and --max-size |
| |
On Sun, Jan 8, 2023 at 6:47 PM Yang Jihong <yangjihong1@huawei.com> wrote: > > Hello, > > On 2023/1/7 5:12, Namhyung Kim wrote: > > Hello, > > > > On Wed, Jan 4, 2023 at 8:09 PM Yang Jihong <yangjihong1@huawei.com> wrote: > >> > >> Hello, > >> > >> On 2023/1/4 0:50, Namhyung Kim wrote: > >>> On Mon, Jan 2, 2023 at 8:20 AM Arnaldo Carvalho de Melo <acme@kernel.org> wrote: > >>>> > >>>> Em Thu, Dec 29, 2022 at 12:47:28PM +0000, Yang Jihong escreveu: > >>>>> 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 1M -a -- sleep 1 > >>>>> [ perf record: Woken up 1 times to write data ] > >>>>> perf: Segmentation fault > >>>>> Obtained 1 stack frames. > >>>>> [0xc4c67f] > >>>>> Segmentation fault (core dumped) > >>>>> > >>>>> backtrace of the core file is as follows: > >>>>> > >>>>> #0 0x0000000000417990 in process_locked_synthesized_event (tool=0x0, event=0x15, sample=0x1de0, machine=0xf8) at builtin-record.c:630 > >>>>> #1 0x000000000057ee53 in perf_event__synthesize_threads (nr_threads_synthesize=21, mmap_data=<optimized out>, needs_mmap=<optimized out>, machine=0x17ad9b0, process=<optimized out>, tool=0x0) at util/synthetic-events.c:1950 > >>>>> #2 __machine__synthesize_threads (nr_threads_synthesize=0, data_mmap=<optimized out>, needs_mmap=<optimized out>, process=<optimized out>, threads=0x8, target=0x8, tool=0x0, machine=0x17ad9b0) at util/synthetic-events.c:1936 > >>>>> #3 machine__synthesize_threads (machine=0x17ad9b0, target=0x8, threads=0x8, needs_mmap=<optimized out>, data_mmap=<optimized out>, nr_threads_synthesize=0) at util/synthetic-events.c:1947 > >>>>> #4 0x000000000040165d in record__synthesize (tail=<optimized out>, rec=0xbe2520 <record>) at builtin-record.c:2010 > >>>>> #5 0x0000000000403989 in __cmd_record (argc=<optimized out>, argv=<optimized out>, rec=0xbe2520 <record>) at builtin-record.c:2810 > >>>>> #6 0x00000000004196ba in record__init_thread_user_masks (rec=0xbe2520 <record>, cpus=0x17a65f0) at builtin-record.c:3837 > >>>>> #7 record__init_thread_masks (rec=0xbe2520 <record>) at builtin-record.c:3938 > >>>>> #8 cmd_record (argc=1, argv=0x7ffdd692dc60) at builtin-record.c:4241 > >>>>> #9 0x00000000004b701d in pager_command_config (var=0x0, value=0x15 <error: Cannot access memory at address 0x15>, data=0x1de0) at perf.c:117 > >>>>> #10 0x00000000004b732b in get_leaf_frame_caller_aarch64 (sample=0xfffffffb, thread=0x0, usr_idx=<optimized out>) at util/arm64-frame-pointer-unwind-support.c:56 > >>>>> #11 0x0000000000406331 in execv_dashed_external (argv=0x7ffdd692d9e8) at perf.c:410 > >>>>> #12 run_argv (argcp=<synthetic pointer>, argv=<synthetic pointer>) at perf.c:431 > >>>>> #13 main (argc=<optimized out>, argv=0x7ffdd692d9e8) 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 only need to check the value of done first. > >>>>> Also add variable check in record__bytes_written for code hardening, > >>>>> and save bytes_written separately to reduce one calculation. > >>>>> > >>>>> Fixes: 6d57581659f7 ("perf record: Add support for limit perf output file size") > >>>>> Signed-off-by: Yang Jihong <yangjihong1@huawei.com> > >>>>> --- > >>>>> > >>>>> 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. > >>>> > >>>> Namhyung, are you ok with this now? > >>>> > >>>> - Arnaldo > >>>> > >>>>> tools/perf/builtin-record.c | 26 +++++++++++++++++--------- > >>>>> 1 file changed, 17 insertions(+), 9 deletions(-) > >>>>> > >>>>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c > >>>>> index 29dcd454b8e2..acba9e43e519 100644 > >>>>> --- a/tools/perf/builtin-record.c > >>>>> +++ b/tools/perf/builtin-record.c > >>>>> @@ -230,16 +230,29 @@ static u64 record__bytes_written(struct record *rec) > >>>>> u64 bytes_written = rec->bytes_written; > >>>>> struct record_thread *thread_data = rec->thread_data; > >>>>> > >>>>> + if (thread_data == NULL) > >>>>> + return bytes_written; > >>>>> + > >>> > >>> Then it won't count bytes written by threads, right? > >>> I think it needs to be saved somewhere. > >>> > >> I'm not sure here. Can you explain it more clearly, thanks :) > >> I can modify it accordingly. > >> > >> I think if thread_data == NULL, it is not thread data. > >> In this case, we just return rec->bytes_written. > > > > It can be thread data but freed before tail synthesis, right? > > In that case, I think it needs to add bytes_written by threads > > to calculate the correct data size. > Em... In the __cmd_record function, record__stop_threads is called > before record__free_thread_data, so if the thread has been freed, there > will be no thread data. > I think it's okay to ignore the situation you mentioned above.
Right, the thread data is already freed, but we need the size.
I think it didn't (and won't) update to rec->bytes_written for the data written by the threads (data.X file) because it's only for the main 'data' file. So record__bytes_written() will return a smaller number after the threads are gone. But I think it should return the total data size.
Thanks, Namhyung
| |