Re: perf seg fault

[Adrian Hunter]

On 12/05/20 6:55 pm, Jiri Olsa wrote:
> On Tue, May 12, 2020 at 06:45:24PM +0300, Adrian Hunter wrote:
>> On 12/05/20 6:10 pm, Jiri Olsa wrote:
>>> On Tue, May 12, 2020 at 05:58:29PM +0300, Adrian Hunter wrote:
>>>> Forgot to cc mailing list
>>>>
>>>> On 12/05/20 5:50 pm, Adrian Hunter wrote:
>>>>> Hi
>>>>>
>>>>> I am getting a seg fault from your perf/core branch, as follows:
>>>>>
>>>>> # perf record uname
>>>>> Linux
>>>>> [ perf record: Woken up 1 times to write data ]
>>>>> [ perf record: Captured and wrote 0.005 MB perf.data (7 samples) ]
>>>>> perf: Segmentation fault
>>>>> Obtained 6 stack frames.
>>>>> [0x4e75b4]
>>>>> [0x5d1ad0]
>>>>> [0x5c9860]
>>>>> [0x4a6e5c]
>>>>> [0x5cb39b]
>>>>> [0x76c89f]
>>>>> Segmentation fault
>>>>>
>>>>> It goes away with --no-bpf-event:
>>>>>
>>>>> # perf record --no-bpf-event uname
>>>>> Linux
>>>>> [ perf record: Woken up 1 times to write data ]
>>>>> [ perf record: Captured and wrote 0.005 MB perf.data (7 samples) ]
>>>>> #
>>>>>
>>>>> kernel is from the same branch
>>>>>
>>>>> # uname -a
>>>>> Linux buildroot 5.7.0-rc2-00028-g0fdddf5a583a #165 SMP Tue May 12 16:27:53
>>>>> EEST 2020 x86_64 GNU/Linux
>>>>>
>>>>> # perf version --build-options
>>>>> perf version 5.6.g0fdddf5a583a
>>>>>                  dwarf: [ OFF ]  # HAVE_DWARF_SUPPORT
>>>>>     dwarf_getlocations: [ OFF ]  # HAVE_DWARF_GETLOCATIONS_SUPPORT
>>>>>                  glibc: [ on  ]  # HAVE_GLIBC_SUPPORT
>>>>>                   gtk2: [ OFF ]  # HAVE_GTK2_SUPPORT
>>>>>          syscall_table: [ on  ]  # HAVE_SYSCALL_TABLE_SUPPORT
>>>>>                 libbfd: [ on  ]  # HAVE_LIBBFD_SUPPORT
>>>>>                 libelf: [ on  ]  # HAVE_LIBELF_SUPPORT
>>>>>                libnuma: [ OFF ]  # HAVE_LIBNUMA_SUPPORT
>>>>> numa_num_possible_cpus: [ OFF ]  # HAVE_LIBNUMA_SUPPORT
>>>>>                libperl: [ OFF ]  # HAVE_LIBPERL_SUPPORT
>>>>>              libpython: [ OFF ]  # HAVE_LIBPYTHON_SUPPORT
>>>>>               libslang: [ on  ]  # HAVE_SLANG_SUPPORT
>>>>>              libcrypto: [ on  ]  # HAVE_LIBCRYPTO_SUPPORT
>>>>>              libunwind: [ OFF ]  # HAVE_LIBUNWIND_SUPPORT
>>>>>     libdw-dwarf-unwind: [ OFF ]  # HAVE_DWARF_SUPPORT
>>>>>                   zlib: [ OFF ]  # HAVE_ZLIB_SUPPORT
>>>>>                   lzma: [ OFF ]  # HAVE_LZMA_SUPPORT
>>>>>              get_cpuid: [ on  ]  # HAVE_AUXTRACE_SUPPORT
>>>>>                    bpf: [ OFF ]  # HAVE_LIBBPF_SUPPORT
>>>>>                    aio: [ on  ]  # HAVE_AIO_SUPPORT
>>>>>                   zstd: [ OFF ]  # HAVE_ZSTD_SUPPORT
>>>>>
>>>>>
>>>>> Any thoughts?
>>>
>>> hum, I don't see that, do you reproduce with DEBUG=1?
>>> to get more verbose backtrace
>>
>> It will require a kernel with support for bpf events otherwise the
>> --no-bpf-event option would have no effect.
> 
> ok, reproduced..  I think we need to think about better way,
> but this fixes the issue for me now
> 
> jirka
> 
> 
> ---
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 4d4502b7fea0..173012a25df3 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -2564,6 +2564,10 @@ int cmd_record(int argc, const char **argv)
>  	if (quiet)
>  		perf_quiet_option();
>  
> +#ifndef HAVE_LIBBPF_SUPPORT
> +	rec->opts.no_bpf_event = true;
> +#endif
> +
>  	/* Make system wide (-a) the default target. */
>  	if (!argc && target__none(&rec->opts.target))
>  		rec->opts.target.system_wide = true;
> 


Thank you!