On Fri, Mar 04, 2016 at 02:39:38AM +0300, Dmitry V. Levin wrote: > On Wed, Mar 02, 2016 at 09:29:24PM -0500, Rich Felker wrote: > > On Thu, Mar 03, 2016 at 05:16:18AM +0300, Dmitry V. Levin wrote: > > > On Wed, Mar 02, 2016 at 08:28:30PM -0500, Rich Felker wrote: > [...] > > > > What should be done about daemonized tracer mode? > > > > > > If we could switch stack before clone and then switch stack back in the > > > child process, it would be a relatively simple change. > > > Otherwise I don't see any simple options. > > > > I think it's possible to switch stack in the parent via sigaltstack > > and raise, after which the cloned child can longjmp back to the stack > > that was the parent's. > > This might work. Whatever signal is chosen, its handler and mask would > have to be restored before the final execve call.
The handler and mask could be restored before even calling clone; actually, the whole machinery could be implemented as a wrapper for clone that lets you pick whether the child runs a new function on a new stack with the parent returning (like normal clone) or the parent runs a new function on a new stack (with the child returning). > > Alternatively the child could just re-enter > > main() on a new stack with a global var set to indicate that it's the > > tracer child. > > I think it would be too risky to let the main bulk of strace code run > on the new stack. Just in terms of stack size available? Or something else? Rich ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 _______________________________________________ Strace-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/strace-devel
