Messages in this thread | | | Date | Sun, 19 Jan 2014 16:29:22 +0100 | From | Oleg Nesterov <> | Subject | Re: [RFC/PATCH] Implement new PTRACE_EVENT_SYSCALL_{ENTER,EXIT} |
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On 01/19, Sergio Durigan Junior wrote: > > On Friday, January 10 2014, Oleg Nesterov wrote: > > > So suppose that gdb does ptrace(PTRACE_SINGLESTEP) and the tracee > > executes the "syscall" insn. What it should report? > [...] > > But what should syscall-exit do? Should it still report SIGSEGV as > > it currently does, or should it report _SYSCALL_EXIT instead (if > > PTRACE_O_SYSCALL_EXIT of course), or should it report both? > > Both only if _SYSCALL_EXIT is set. Otherwise, stick to the current > behavior, I guess.
OK, both. In which order? Probably _EXIT first. But this looks a bit strange. Suppose that the tracee reports _EXIT, then debugger does ptrace(PTRACE_CONT), should the tracee report SIGTRAP?
SIGTRAP before _EXIT looks a bit strange too... Single-step trap should be reported after insn, but we are still in syscall.
So perhaps _EXIT should win and do not report the step?
> Isn't it what my current patch does, by the way?
I forgot how this patch looks so I can be easily wrong, but iirc no. Note that tracehook_report_syscall_exit() doesn't even call ptrace_report_syscall() if step == T.
Btw, if you send v2, please CC Michael Kerrisk <mtk.manpages@gmail.com>.
Oleg.
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