Make sure that the new debugger doesn't get the old values in
ptrace_context or engine->flags if it re-uses the self-detaching
engine.
In particular, we should clear tracee->exit_code. The new debugger
should not see it via do_wait() until the tracee stops again. This
is racy, but ->exit_code changes were always racy in ptrace. Hopefully
sooner or later ptrace will not use ->exit_code at all.
Perhaps we should move this reinitialization into ptrace_attach_task(),
we will see.
Perhaps, instead of utrace_control() ptrace_detach_task() should use
ptrace_wake_up() which clears SIGNAL_STOP_STOPPED. This is wrong, but
more compatible with the current implementation. I dunno.
---
kernel/ptrace.c | 9 +++++++++
1 file changed, 9 insertions(+)
--- PU/kernel/ptrace.c~82_RESET_CONTEXT_ON_DETACH 2009-10-10
17:13:37.000000000 +0200
+++ PU/kernel/ptrace.c 2009-10-10 17:43:28.000000000 +0200
@@ -109,7 +109,16 @@ static void ptrace_detach_task(struct ta
case PTRACE_EVENT_SIGNAL:
if (valid_signal(sig))
context->signr = sig;
+ context->options = 0;
+ context->eventmsg = 0;
context->stop_code = 0;
+ /* make sure do_wait() can't succeed */
+ tracee->exit_code = 0;
+ utrace_set_events(tracee, engine,
UTRACE_EVENT(QUIESCE));
+ /*
+ * once we set UTRACE_DETACH we don't own this engine,
+ * utrace_set_events() also acts as a memory barrier.
+ */
context->resume = UTRACE_DETACH;
action = UTRACE_RESUME;
break;
