Add PTRACE_VFORK to trace vfork events.

First, PL_FLAG_FORKED events now also set a PL_FLAG_VFORKED flag when
the new child was created via vfork() rather than fork().  Second, a
new PL_FLAG_VFORK_DONE event can now be enabled via the PTRACE_VFORK
event mask.  This new stop is reported after the vfork parent resumes
due to the child calling exit or exec.  Debuggers can use this stop to
reinsert breakpoints in the vfork parent process before it resumes.

Reviewed by:	kib
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D7045

1 files changed, 126 insertions, 0 deletions

diff --git a/tests/sys/kern/ptrace_test.c b/tests/sys/kern/ptrace_test.c
index be978edf06d4..dede0f84f4aa 100644
--- a/tests/sys/kern/ptrace_test.c
+++ b/tests/sys/kern/ptrace_test.c
@@ -1549,6 +1549,130 @@ ATF_TC_BODY(ptrace__event_mask, tc)
 	ATF_REQUIRE(errno == ECHILD);
 }
 
+/*
+ * Verify that the expected ptrace events are reported for PTRACE_VFORK.
+ */
+ATF_TC_WITHOUT_HEAD(ptrace__ptrace_vfork);
+ATF_TC_BODY(ptrace__ptrace_vfork, tc)
+{
+	struct ptrace_lwpinfo pl;
+	pid_t fpid, wpid;
+	int events, status;
+
+	ATF_REQUIRE((fpid = fork()) != -1);
+	if (fpid == 0) {
+		trace_me();
+		follow_fork_parent(true);
+	}
+
+	/* The first wait() should report the stop from SIGSTOP. */
+	wpid = waitpid(fpid, &status, 0);
+	ATF_REQUIRE(wpid == fpid);
+	ATF_REQUIRE(WIFSTOPPED(status));
+	ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
+
+	ATF_REQUIRE(ptrace(PT_GET_EVENT_MASK, fpid, (caddr_t)&events,
+	    sizeof(events)) == 0);
+	events |= PTRACE_VFORK;
+	ATF_REQUIRE(ptrace(PT_SET_EVENT_MASK, fpid, (caddr_t)&events,
+	    sizeof(events)) == 0);
+	
+	/* Continue the child ignoring the SIGSTOP. */
+	ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) != -1);
+
+	/* The next event should report the end of the vfork. */
+	wpid = wait(&status);
+	ATF_REQUIRE(wpid == fpid);
+	ATF_REQUIRE(WIFSTOPPED(status));
+	ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
+	ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
+	ATF_REQUIRE((pl.pl_flags & PL_FLAG_VFORK_DONE) != 0);
+
+	ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) != -1);
+
+	wpid = wait(&status);
+	ATF_REQUIRE(wpid == fpid);
+	ATF_REQUIRE(WIFEXITED(status));
+	ATF_REQUIRE(WEXITSTATUS(status) == 1);
+
+	wpid = wait(&status);
+	ATF_REQUIRE(wpid == -1);
+	ATF_REQUIRE(errno == ECHILD);
+}
+
+ATF_TC_WITHOUT_HEAD(ptrace__ptrace_vfork_follow);
+ATF_TC_BODY(ptrace__ptrace_vfork_follow, tc)
+{
+	struct ptrace_lwpinfo pl[2];
+	pid_t children[2], fpid, wpid;
+	int events, status;
+
+	ATF_REQUIRE((fpid = fork()) != -1);
+	if (fpid == 0) {
+		trace_me();
+		follow_fork_parent(true);
+	}
+
+	/* Parent process. */
+	children[0] = fpid;
+
+	/* The first wait() should report the stop from SIGSTOP. */
+	wpid = waitpid(children[0], &status, 0);
+	ATF_REQUIRE(wpid == children[0]);
+	ATF_REQUIRE(WIFSTOPPED(status));
+	ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
+
+	ATF_REQUIRE(ptrace(PT_GET_EVENT_MASK, children[0], (caddr_t)&events,
+	    sizeof(events)) == 0);
+	events |= PTRACE_FORK | PTRACE_VFORK;
+	ATF_REQUIRE(ptrace(PT_SET_EVENT_MASK, children[0], (caddr_t)&events,
+	    sizeof(events)) == 0);
+
+	/* Continue the child ignoring the SIGSTOP. */
+	ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
+
+	/* Wait for both halves of the fork event to get reported. */
+	children[1] = handle_fork_events(children[0], pl);
+	ATF_REQUIRE(children[1] > 0);
+
+	ATF_REQUIRE((pl[0].pl_flags & PL_FLAG_VFORKED) != 0);
+
+	ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
+	ATF_REQUIRE(ptrace(PT_CONTINUE, children[1], (caddr_t)1, 0) != -1);
+
+	/*
+	 * The child can't exit until the grandchild reports status, so the
+	 * grandchild should report its exit first to the debugger.
+	 */
+	wpid = waitpid(children[1], &status, 0);
+	ATF_REQUIRE(wpid == children[1]);
+	ATF_REQUIRE(WIFEXITED(status));
+	ATF_REQUIRE(WEXITSTATUS(status) == 2);
+
+	/*
+	 * The child should report it's vfork() completion before it
+	 * exits.
+	 */
+	wpid = wait(&status);
+	ATF_REQUIRE(wpid == children[0]);
+	ATF_REQUIRE(WIFSTOPPED(status));
+	ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
+	ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl[0], sizeof(pl[0])) !=
+	    -1);
+	ATF_REQUIRE((pl[0].pl_flags & PL_FLAG_VFORK_DONE) != 0);
+
+	ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1);
+
+	wpid = wait(&status);
+	ATF_REQUIRE(wpid == children[0]);
+	ATF_REQUIRE(WIFEXITED(status));
+	ATF_REQUIRE(WEXITSTATUS(status) == 1);
+
+	wpid = wait(&status);
+	ATF_REQUIRE(wpid == -1);
+	ATF_REQUIRE(errno == ECHILD);
+}
+
 ATF_TP_ADD_TCS(tp)
 {
 
@@ -1574,6 +1698,8 @@ ATF_TP_ADD_TCS(tp)
 	ATF_TP_ADD_TC(tp, ptrace__ptrace_exec_disable);
 	ATF_TP_ADD_TC(tp, ptrace__ptrace_exec_enable);
 	ATF_TP_ADD_TC(tp, ptrace__event_mask);
+	ATF_TP_ADD_TC(tp, ptrace__ptrace_vfork);
+	ATF_TP_ADD_TC(tp, ptrace__ptrace_vfork_follow);
 
 	return (atf_no_error());
 }