[PATCH v2] kern/tty_pty: Fix reporting EOF via kevent and add a test case

[Michał Górny <mgorny%gentoo.org@localhost>]

Fix the kernel pty driver to report closed slave via master's kevent
EVFILT_READ.  This behavior matches the behavior for pipes, is
consistent with how FreeBSD implements it and is relied upon by LLDB's
main loop implementation.
---
 sys/kern/tty_pty.c                            |  4 +
 tests/kernel/kqueue/read/Makefile             |  2 +
 tests/kernel/kqueue/read/t_pty_closed_slave.c | 94 +++++++++++++++++++
 3 files changed, 100 insertions(+)
 create mode 100644 tests/kernel/kqueue/read/t_pty_closed_slave.c

diff --git a/sys/kern/tty_pty.c b/sys/kern/tty_pty.c
index 1d60596124d3..94270381b5ab 100644
--- a/sys/kern/tty_pty.c
+++ b/sys/kern/tty_pty.c
@@ -938,6 +938,10 @@ filt_ptcread(struct knote *kn, long hint)
 		    ((pti->pt_flags & PF_UCNTL) && pti->pt_ucntl))
 			kn->kn_data++;
 	}
+	if (!ISSET(tp->t_state, TS_CARR_ON)) {
+		kn->kn_flags |= EV_EOF;
+		canread = 1;
+	}
 
 	if ((hint & NOTE_SUBMIT) == 0) {
 		mutex_spin_exit(&tty_lock);
diff --git a/tests/kernel/kqueue/read/Makefile b/tests/kernel/kqueue/read/Makefile
index 510ed45c486c..d1a321aeb003 100644
--- a/tests/kernel/kqueue/read/Makefile
+++ b/tests/kernel/kqueue/read/Makefile
@@ -10,8 +10,10 @@ TESTS_C=	t_fifo
 TESTS_C+=	t_file
 TESTS_C+=	t_file2
 TESTS_C+=	t_pipe
+TESTS_C+=	t_pty_closed_slave
 TESTS_C+=	t_ttypty
 
 LDADD.t_ttypty=	-lutil
+LDADD.t_pty_closed_slave=-lutil
 
 .include <bsd.test.mk>
diff --git a/tests/kernel/kqueue/read/t_pty_closed_slave.c b/tests/kernel/kqueue/read/t_pty_closed_slave.c
new file mode 100644
index 000000000000..1972103a2085
--- /dev/null
+++ b/tests/kernel/kqueue/read/t_pty_closed_slave.c
@@ -0,0 +1,94 @@
+/* $NetBSD$ */
+
+/*-
+ * Copyright (c) 2019 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__COPYRIGHT("@(#) Copyright (c) 2019\
+ The NetBSD Foundation, inc. All rights reserved.");
+__RCSID("$NetBSD$");
+
+#include <sys/event.h>
+#include <sys/time.h>
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <termios.h>
+#include <unistd.h>
+#include <util.h>
+
+#include <atf-c.h>
+
+#include "h_macros.h"
+
+ATF_TC(kevent);
+ATF_TC_HEAD(kevent, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+		"Checks EVFILT_READ reporting for slave tty being closed");
+}
+ATF_TC_BODY(kevent, tc)
+{
+	char slavetty[1024];
+	struct kevent event[1];
+	int amaster, aslave;
+	int kq, n;
+#if 0
+	int fl;
+#endif
+	struct timespec timeout = {5, 0};
+
+	RL(openpty(&amaster, &aslave, slavetty, NULL, NULL));
+
+	(void)printf("tty: openpty master %d slave %d tty '%s'\n",
+		amaster, aslave, slavetty);
+
+	RL(kq = kqueue());
+
+	EV_SET(&event[0], amaster, EVFILT_READ, EV_ADD|EV_ENABLE, 0, 0, 0);
+	RL(kevent(kq, event, 1, NULL, 0, NULL));
+
+	RL(close(aslave));
+
+	RL(n = kevent(kq, NULL, 0, event, 1, &timeout));
+
+	(void)printf("kevent num %d filt %d flags: %#x, fflags: %#x, "
+	    "data: %" PRId64 "\n", n, event[0].filter, event[0].flags,
+	    event[0].fflags, event[0].data);
+
+	ATF_REQUIRE_EQ(n, 1);
+	ATF_REQUIRE_EQ(event[0].filter, EVFILT_READ);
+	ATF_REQUIRE_EQ(event[0].flags & EV_EOF, EV_EOF);
+
+	(void)printf("tty: successful end\n");
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+	ATF_TP_ADD_TC(tp, kevent);
+
+	return atf_no_error();
+}
-- 
2.20.1