[Bug general/3997] SIGTRAP handler gets reset when single stepping

["mark at klomp dot org" <sourceware-bugzilla@sourceware.org>]

------- Additional Comments From mark at klomp dot org  2007-03-19 12:00 -------
This is a misfeature of ptrace single step. It uses SIGTRAP to signal that a
step is made. this used to work in older kernels. But newer kernels decided to
block the sig trap handler if the child wasn't using a reentrant sigtrap handler
(even though the ptracing debugger would of course swallow the signal and never
deliver it to the child itself). Resetting the child signal handler obviously
breaks out testcases. For now, to have minimal testing of sigtrap handler
stepping, we instrument the test programs to us SA_NODEFER. Also the
funit-breakpoints uses a simple SIGUSER handler to test signal stepping and
breakpointing.

The real solution for this problem, so we can single step also non-altered user
programs that use SIGTRAP, is to use a, non-existing yet, interface on top of
utrace that doesn't use SIGTRAP for reporting events to frysk.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=3997

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