[lkml]   [2011]   [Sep]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: Why I want PTRACE_O_TRACESTOP option
    On Fri, September 9, 2011 14:26, Indan Zupancic wrote:
    > Hello,
    > On Fri, September 9, 2011 07:54, Denys Vlasenko wrote:
    >> On Friday 09 September 2011 02:18, Tejun Heo wrote:
    >>> Hello, Denys.
    >>> On Thu, Sep 08, 2011 at 06:50:01PM +0200, Denys Vlasenko wrote:
    >>> > Consider what will happen when a next ptrace fix will require
    >>> > a way to change ptrace API at runtime. A new option will likely
    >>> > be introduced, say, PTRACE_O_TRACEPONY, with next available
    >>> > bit position 7, and perhaps some new event will be generated,
    >>> > PTRACE_EVENT_PONY, with value.... yes, it can't be 7,
    >>> > PTRACE_EVENT_STOP took it. So it will probably be 8.
    >>> Then, just give it the next matching number.
    >> My point is that previously, ptrace behavior was modified by setting
    >> options. Why don't we use this mechanism? Why we invent a different
    >> wheel? Ptrace is ugly as-is, why complicate it even further?
    >> The argument was that SETOPTIONS wasn't suitable for modifying
    >> attach behavior, but this is fixed by "set options on SEIZE"
    >> patch. I don't see why we can't use options mechanist to affect
    >> group-stop behavior now.
    > I totally agree with Denys here.
    > It is very useful to set options atomically at SEIZE time. Having
    > SEIZE set some hidden option implicitly only makes things more
    > confusing and harder to explain what SEIZE does. Please apply Denys'
    > SEIZE API improvements.
    > Another important reason to make PTRACE_O_TRACESTOP an option is
    > because not everyone uses SEIZE: Users using PTRACE_TRACEME can't
    > set this option at all. For those PTRACE_O_TRACESTOP is needed.
    > Using PTRACE_TRACEME is the common case for both strace and gdb.

    PTRACE_O_TRACESTOP only makes sense if it also affects auto-attach
    SIGSTOPS, of course. I don't know if it does. It probably should.


     \ /
      Last update: 2011-09-09 15:03    [W:0.022 / U:12.216 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site