[PATCH 53-55] (Was: Q: what user_enable_single_step() actually means?)

[Oleg Nesterov]

On 09/23, Roland McGrath wrote:
>
> It's a further oddity that you can single-step (or not) "into" the
> system call and then get a ptrace stop "inside" it, that being for
> PTRACE_EVENT_FORK et al.  From there, the thread register state shows
> it being after the syscall insn, but (in vanilla ptrace, and at the
> time of report_clone callbacks at utrace level) without the return
> value register having been written yet.

And how we can implement this?

regs->ax is updated right after "call *sys_call_table[]", and we
report PTRACE_EVENT_FORK or PTRACE_EVENT_EXEC much later.


Oh. What if we change utrace_report_exec() and tracehook_report_clone_complete()
to use finish_resume_report() and actually stop?

This way all problems go away, and the stacked events are not needed.


The current logic which delays the stop adds so many complications...

Oleg.