Re: perf seg fault

[Adrian Hunter]

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.