* strace.c [LINUX && PTRACE_EVENT_FORK] (trace): Handle Linux
PTRACE_EVENT_{FORK,VFORK,CLONE} events. If one signals that a
fork/vfork/clone happened, begin tracing the child process immediately
without waiting for the parent syscall to return. Set TCB_FORK_EVENT
so the syscall return doesn't try to attach to the child.
Signed-off-by: Jamie Lokier <ja...@shareable.org>
---
process.c | 5 ++---
strace.c | 35 +++++++++++++++++++++++++++++++++++
2 files changed, 37 insertions(+), 3 deletions(-)
diff --git a/process.c b/process.c
index e46957d..bfc4c9d 100644
--- a/process.c
+++ b/process.c
@@ -790,9 +790,8 @@ change_syscall(struct tcb *tcp, int new)
#ifdef LINUX
/*
* Called when we learn about a child process and know which parent
- * it's from. (Dubiously, pid here is int
- * because alloctcb() uses it, but syscall return values are unsigned
- * long and could overflow.)
+ * it's from. (Dubiously, pid here is int because alloctcb() uses it,
+ * but syscall return values are unsigned long and could overflow.)
*
* from_ptrace_event is set if called for PTRACE_EVENT_{FORK,VFORK,CLONE}.
* Then we know the child is attached and tracing despite CLONE_PTRACE
diff --git a/strace.c b/strace.c
index 5b44f1c..ac807f0 100644
--- a/strace.c
+++ b/strace.c
@@ -2580,6 +2580,41 @@ Process %d attached (waiting for parent)\n",
tcp->flags &= ~TCB_SUSPENDED;
continue;
}
+
+#if defined LINUX && defined PTRACE_EVENT_FORK
+ /*
+ * When there is a PTRACE_EVENT_*, WSTOPSIG(status) == SIGTRAP
+ * because that macro ignores the upper 16 bits, at least on
+ * Linux where these events occur.
+ *
+ * These events don't replace syscall entry and exit.
+ * They are additional events, in the middle.
+ */
+ if ((status >> 16) != 0) {
+ /* PTRACE_GETEVENTMSG takes pointer to unsigned long.*/
+ unsigned long child = 0;
+ if (followfork
+ /* FIXME: Should check it's a fork syscall. */
+ && (tcp->flags & TCB_INSYSCALL)
+ && ((status >> 16) == PTRACE_EVENT_FORK
+ || (status >> 16) == PTRACE_EVENT_VFORK
+ || (status >> 16) == PTRACE_EVENT_CLONE)
+ && ptrace(PTRACE_GETEVENTMSG, tcp->pid,
+ (char *) 1, (long) &child) == 0
+ && (int)child > 0 && (unsigned int)child == child) {
+ if (internal_fork_child(tcp, child, 1) < 0) {
+ cleanup();
+ return -1;
+ }
+ tcp->flags |= TCB_FORK_EVENT;
+ } else {
+ fprintf(stderr, "pid %d stray PTRACE_EVENT\n",
+ tcp->pid);
+ }
+ goto tracing;
+ }
+#endif /* LINUX && PTRACE_EVENT_FORK */
+
/* we handled the STATUS, we are permitted to interrupt now. */
if (interrupted)
return 0;
--
1.7.0.4
_______________________________________________
uClinux-dev mailing list
uClinux-dev@uclinux.org
http://mailman.uclinux.org/mailman/listinfo/uclinux-dev
This message was resent by uclinux-dev@uclinux.org
To unsubscribe see:
http://mailman.uclinux.org/mailman/options/uclinux-dev
