Re: [PATCH 3/6] x86: clean up _TIF_SYSCALL_EMU handling using ptrace_syscall_enter hook

Haibo Xu (Arm Technology China)
2019-03-05T02:15:03Z

On 2019/3/4 18:12, Sudeep Holla wrote:
> On Mon, Mar 04, 2019 at 08:25:28AM +0000, Haibo Xu (Arm Technology China) wrote:
>> On 2019/3/1 2:32, Sudeep Holla wrote:
>>> Now that we have a new hook ptrace_syscall_enter that can be called from
>>> syscall entry code and it handles PTRACE_SYSEMU in generic code, we
>>> can do some cleanup using the same in syscall_trace_enter.
>>>
>>> Further the extra logic to find single stepping PTRACE_SYSEMU_SINGLESTEP
>>> in syscall_slow_exit_work seems unnecessary. Let's remove the same.
>>
>> I think we should not change the logic here. Is so, it will double the report of syscall
>> when PTRACE_SYSEMU_SINGLESTEP is enabled.
>>
>
> I don't think that should happen, but I may be missing something.
> Can you explain how ?
>
> --
> Regards,
> Sudeep
>

When PTRACE_SYSEMU_SINGLESTEP is enabled, both the _TIF_SYSCALL_EMU and _TIF_SINGLESTEP
flags are set, but ptrace only need to report(send SIGTRAP) at the entry of a system call,
no need to report at the exit of a system call.

Regards,
Haibo
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