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

Haibo Xu (Arm Technology China) Haibo.Xu at arm.com
Wed Mar 13 12:03:18 AEDT 2019

On 2019/3/12 20:09, Sudeep Holla wrote:
> On Mon, Mar 11, 2019 at 08:04:39PM -0700, Andy Lutomirski wrote:
>> On Mon, Mar 11, 2019 at 6:35 PM Haibo Xu (Arm Technology China)
>> <Haibo.Xu at arm.com> wrote:
> [...]
>>> For the PTRACE_SYSEMU_SINGLESTEP request, 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.That's why the old logic-{step = ((flags & (_TIF_SINGLESTEP |
>>> _TIF_SYSCALL_EMU)) == _TIF_SINGLESTEP)} here try to filter out the special
>>> Another way to make sure the logic is fine, you can run some tests with
>>> respect to both logic, and to check whether they have the same behavior.
>> tools/testing/selftests/x86/ptrace_syscall.c has a test intended to
>> exercise this.  Can one of you either confirm that it does exercise it
>> and that it still passes or can you improve the test?
> I did run the tests which didn't flag anything. I haven't looked at the
> details of test implementation, but seem to miss this case. I will see
> what can be improved(if it's possible). Also I think single_step_syscall
> is the one I need to look for this particular one. Both single_step_syscall
> ptrace_syscall reported no errors.
> --
> Regards,
> Sudeep

Since ptrace() system call do have so many request type, I'm not sure whether the
test cases have covered all of that. But here we'd better make sure the PTRACE_SYSEMU
and PTRACE_SYSEMU_SINGLESTEP requests are work correctly. May be you can verify them with
tests from Bin Lu(bin.lu at arm.com).

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