[Crash-utility] [PATCH] crash-extension/gcore: fix the failure of invalid structure member offset

[lijiang]

在 2020年08月28日 16:36, HAGIO KAZUHITO(萩尾　一仁) 写道:
> -----Original Message-----
>> Hi Lianbo,
>>
>> Please note that we still need to formulate a way to maintain
>> crash-extension outside a tarball.
>> I am preparing a RFC proposal and will share it shortly.
> 
> FYI, the maintainer of gcore is Daisuke (Hatayama-san), so I think he
> will review the patch and release a new version of gcore someday, and
> then we put it to the crash-extension repository.  As for gcore, this
> is the way Dave and Hatayama-san have done so far, IIRC.
> 
Good to know. Thanks.

>>
>> On Fri, Aug 28, 2020 at 9:34 AM Lianbo Jiang <lijiang at redhat.com> wrote:
>>>
>>> With kernel commit: <577d5cd7e585> ("x86/ioperm: Move iobitmap data into
>>> a struct"), the io_bitmap_max and io_bitmap_ptr have been changed. And
>>> move the iobitmap data into a struct io_bitmap.
>>>
>>> So, the crash-gcore-command needs to be updated accordingly, otherwise,
>>> the gcore will fail as below:
>>>
>>> crash> bt -t|grep -i task
>>> PID: 3968   TASK: ffff9e512e97af80  CPU: 86  COMMAND: "bash"
>>> crash> gcore 3968
>>>
>>> gcore: invalid structure member offset: thread_struct_io_bitmap_max
>>>        FILE: libgcore/gcore_x86.c  LINE: 846  FUNCTION: ioperm_active()
>>>
>>> [./crash] error trace: 7f31fca56108 => 7f31fca593b7 => 53a4e1 => 53a463
>>>
>>>   53a463: OFFSET_verify.part.27+51
>>>   53a4e1: OFFSET_verify+49
>>>
>>> gcore: invalid structure member offset: thread_struct_io_bitmap_max
>>>        FILE: libgcore/gcore_x86.c  LINE: 846  FUNCTION: ioperm_active()
>>>
>>> Failed.
>>>
>>> Signed-off-by: Lianbo Jiang <lijiang at redhat.com>
>>> ---
>>>  gcore.c | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>>
>>> diff --git a/gcore.c b/gcore.c
>>> index 27a11938026a..e3e41ecb435b 100644
>>> --- a/gcore.c
>>> +++ b/gcore.c
>>> @@ -487,6 +487,10 @@ static void gcore_offset_table_init(void)
>>>                 GCORE_MEMBER_OFFSET_INIT(thread_struct_xstate, "thread_struct", "i387");
>>>         GCORE_MEMBER_OFFSET_INIT(thread_struct_io_bitmap_max, "thread_struct", "io_bitmap_max");
>>>         GCORE_MEMBER_OFFSET_INIT(thread_struct_io_bitmap_ptr, "thread_struct", "io_bitmap_ptr");
>>> +       if (GCORE_INVALID_MEMBER(thread_struct_io_bitmap_max)) {
>>> +               GCORE_MEMBER_OFFSET_INIT(thread_struct_io_bitmap_max, "io_bitmap", "max");
>>> +               GCORE_MEMBER_OFFSET_INIT(thread_struct_io_bitmap_ptr, "io_bitmap", "bitmap");
>>> +       }
>>
>> Maybe its better to protect this with a kernel version check to
>> maintain backward compatibility. Something like:
>>
>> (THIS_KERNEL_VERSION < LINUX(4,2,0))
> 
> I've not looked at this yet, but generally we have to try to avoid
> using kernel version check as far as possible, because kernel version
> is fragile in distribution kernels, e.g. RHEL8 kernels are 4.18.0 but
> have many 5.x patches.
> 
Thanks for your comment, Kazu and Bhupesh.

Maybe, Hatayama-san has good suggestions, lets wait for the reply or fix.

Thanks.
Lianbo

> Thanks,
> Kazu
> 
>>
>> Thanks,
>> Bhupesh
>>
>>>         GCORE_MEMBER_OFFSET_INIT(user_regset_n, "user_regset", "n");
>>>         GCORE_MEMBER_OFFSET_INIT(vm_area_struct_anon_vma, "vm_area_struct", "anon_vma");
>>>         GCORE_MEMBER_OFFSET_INIT(vm_area_struct_vm_ops, "vm_area_struct", "vm_ops");
>>> --
>>> 2.17.1
>>>
>