Add a few regression tests for mlock(2).

These are intended to exercise some rarely executed code paths.

MFC after:	2 weeks

tests/sys/vm/Makefile

@@ -4,6 +4,7 @@ PACKAGE=	tests
 
 TESTSDIR=	${TESTSBASE}/sys/vm
 
-ATF_TESTS_C+=	mmap_test
+ATF_TESTS_C+=	mlock_test \
+		mmap_test
 
 .include <bsd.test.mk>

tests/sys/vm/mlock_test.c

@@ -0,0 +1,174 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2019 Mark Johnston <markj@FreeBSD.org>
+ *
+ * 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 AUTHOR 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 AUTHOR 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>
+__FBSDID("$FreeBSD$");
+
+#include <sys/mman.h>
+#include <sys/ptrace.h>
+#include <sys/wait.h>
+
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <atf-c.h>
+
+static void
+test_wired_copy_on_write(void *addr, size_t len)
+{
+	int status, val;
+	pid_t pid;
+
+	pid = fork();
+	if (pid == -1)
+		atf_tc_fail("fork() failed: %s", strerror(errno));
+	if (pid == 0) {
+		if (mlock(addr, len) != 0)
+			_exit(1);
+		if (ptrace(PT_TRACE_ME, 0, NULL, 0) != 0)
+			_exit(2);
+		if (raise(SIGSTOP) != 0)
+			_exit(3);
+		if (munlock(addr, len) != 0)
+			_exit(4);
+		_exit(0);
+	}
+
+	ATF_REQUIRE(waitpid(pid, &status, 0) == pid);
+	ATF_REQUIRE_MSG(!WIFEXITED(status),
+	    "child exited with status %d", WEXITSTATUS(status));
+	ATF_REQUIRE(WIFSTOPPED(status));
+	ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
+
+	errno = 0;
+	val = ptrace(PT_READ_D, pid, addr, 0);
+	ATF_REQUIRE(errno == 0);
+	ATF_REQUIRE(ptrace(PT_WRITE_D, pid, addr, val) == 0);
+	ATF_REQUIRE(ptrace(PT_CONTINUE, pid, (caddr_t)1, 0) == 0);
+	ATF_REQUIRE(waitpid(pid, &status, 0) == pid);
+	ATF_REQUIRE(WIFEXITED(status));
+	ATF_REQUIRE_MSG(WEXITSTATUS(status) == 0,
+	    "child exited with status %d", WSTOPSIG(status));
+}
+
+/*
+ * Use ptrace(2) to trigger a copy-on-write fault of anonymous memory.
+ */
+ATF_TC_WITHOUT_HEAD(mlock__copy_on_write_anon);
+ATF_TC_BODY(mlock__copy_on_write_anon, tc)
+{
+	char *addr;
+	int len;
+
+	len = getpagesize();
+	addr = mmap(NULL, len, PROT_READ, MAP_ANON, -1, 0);
+	ATF_REQUIRE(addr != MAP_FAILED);
+
+	test_wired_copy_on_write(addr, len);
+}
+
+/*
+ * Use ptrace(2) to trigger a copy-on-write fault of a read-only text page.
+ */
+ATF_TC_WITHOUT_HEAD(mlock__copy_on_write_vnode);
+ATF_TC_BODY(mlock__copy_on_write_vnode, tc)
+{
+	void *addr;
+	int len;
+
+	len = getpagesize();
+	addr = (void *)((uintptr_t)test_wired_copy_on_write & ~(len - 1));
+
+	test_wired_copy_on_write(addr, len);
+}
+
+/*
+ * Try truncating and then resizing an mlock()ed mapping.
+ */
+ATF_TC_WITHOUT_HEAD(mlock__truncate_and_resize);
+ATF_TC_BODY(mlock__truncate_and_resize, tc)
+{
+	char filename[16];
+	char *addr;
+	int fd, i, len;
+
+	snprintf(filename, sizeof(filename), "tmp.XXXXXX");
+	fd = mkstemp(filename);
+	ATF_REQUIRE(fd >= 0);
+	ATF_REQUIRE(unlink(filename) == 0);
+
+	len = getpagesize();
+	ATF_REQUIRE(ftruncate(fd, len) == 0);
+
+	addr = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	ATF_REQUIRE(addr != MAP_FAILED);
+	ATF_REQUIRE(mlock(addr, len) == 0);
+	memset(addr, 1, len);
+	ATF_REQUIRE(ftruncate(fd, 0) == 0);
+	ATF_REQUIRE(ftruncate(fd, len) == 0);
+	for (i = 0; i < len; i++)
+		ATF_REQUIRE(addr[i] == 0);
+	ATF_REQUIRE(munlock(addr, len) == 0);
+}
+
+/*
+ * Make sure that we can munlock() a truncated mapping.
+ */
+ATF_TC_WITHOUT_HEAD(mlock__truncate_and_unlock);
+ATF_TC_BODY(mlock__truncate_and_unlock, tc)
+{
+	char filename[16];
+	void *addr;
+	int fd, len;
+
+	snprintf(filename, sizeof(filename), "tmp.XXXXXX");
+	fd = mkstemp(filename);
+	ATF_REQUIRE(fd >= 0);
+	ATF_REQUIRE(unlink(filename) == 0);
+
+	len = getpagesize();
+	ATF_REQUIRE(ftruncate(fd, len) == 0);
+
+	addr = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	ATF_REQUIRE(addr != MAP_FAILED);
+	ATF_REQUIRE(mlock(addr, len) == 0);
+	ATF_REQUIRE(ftruncate(fd, 0) == 0);
+	ATF_REQUIRE(munlock(addr, len) == 0);
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+	ATF_TP_ADD_TC(tp, mlock__copy_on_write_anon);
+	ATF_TP_ADD_TC(tp, mlock__copy_on_write_vnode);
+	ATF_TP_ADD_TC(tp, mlock__truncate_and_resize);
+	ATF_TP_ADD_TC(tp, mlock__truncate_and_unlock);
+
+	return (atf_no_error());
+}