On Tue, Sep 04, 2012 at 05:39:38PM +0200, Oleg Nesterov wrote: > > BTW, speaking of alpha, what about PTRACE_SINGLESTEP when the task is > > stopped > > on syscall entry/exit after previous PTRACE_SYSCALL, BTW? Looks like it > > will > > be like PTRACE_CONT until we hit the first signal, at which point it > > converts > > to singlesteping mode; unless I'm seriously misreading that code, we rely > > on ptrace_set_bpt() done shortly after returning from > > get_signal_to_deliver() > > if we found that we'd been singlestepping. Fine, but in this case we > > had been resumed *not* in get_signal_to_deliver()... > > Again, "single_stepping |= ptrace_cancel_bpt()" after get_signal_to_deliver() > should work I think... Not sure.
Umm... What would get us anywhere near get_signal_to_deliver() in this case? Look: we do PTRACE_SYSCALL and tracee stops on the way into the system call. We are blocked in ptrace_notify() called from syscall_trace(). Tracer does PTRACE_SINGLESTEP; that resumes the tracee and sets ->bpt_nsaved to -1. The 'data' argument of ptrace() is 0, so tracee->exit_code is 0 so no signals are sent. TIF_SYSCALL_TRACE is cleared. And we are off to execute the syscall and return to userland, without having hit do_signal() on the way out. No breakpoint insns are patched in, so we happily proceed to run the process until a signal arrives, same as we would with PTRACE_CONT. What am I missing here? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
