lib: Add mlibc

Signed-off-by: Ian Moffett <ian@osmora.org>

63 files changed, 3534 insertions, 0 deletions

diff --git a/lib/mlibc/tests/posix/abort.c b/lib/mlibc/tests/posix/abort.c
new file mode 100644
index 0000000..5f7bb7d
--- /dev/null
+++ b/lib/mlibc/tests/posix/abort.c
@@ -0,0 +1,21 @@
+#include <signal.h>
+#include <assert.h>
+#include <stdlib.h>
+
+void handler(int sig, siginfo_t *info, void *ctx) {
+	(void)sig;
+	(void)info;
+	(void)ctx;
+}
+
+int main() {
+	struct sigaction sa;
+	sa.sa_sigaction = handler;
+	sa.sa_flags = SA_SIGINFO;
+	sigemptyset(&sa.sa_mask);
+
+	int ret = sigaction(SIGABRT, &sa, NULL);
+	assert(!ret);
+
+	abort();
+}
diff --git a/lib/mlibc/tests/posix/accept4.c b/lib/mlibc/tests/posix/accept4.c
new file mode 100644
index 0000000..ba593ee
--- /dev/null
+++ b/lib/mlibc/tests/posix/accept4.c
@@ -0,0 +1,123 @@
+#include <unistd.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdbool.h>
+#include <errno.h>
+
+#ifdef USE_HOST_LIBC
+#define TEST_PORT 31337
+#else
+#define TEST_PORT 42069
+#endif
+
+static struct sockaddr_in connect_addr, accept_addr;
+static int listen_fd;
+
+int permutations[] = {
+	0,
+	SOCK_CLOEXEC,
+	SOCK_NONBLOCK,
+	SOCK_CLOEXEC | SOCK_NONBLOCK,
+};
+
+static bool run_test(int flags)
+{
+	int connect_fd;
+	int fd_flags, access;
+	socklen_t addrlen;
+
+	connect_fd = socket(AF_INET, SOCK_STREAM, 0);
+	connect(connect_fd, (struct sockaddr *)&connect_addr, sizeof(connect_addr));
+	addrlen = sizeof(accept_addr);
+
+	int accept_fd = accept4(listen_fd, (struct sockaddr *)&accept_addr, &addrlen, flags);
+
+	if(accept_fd == -1) {
+		fprintf(stderr, "accept4 failed: %s\n", strerror(errno));
+		goto cleanup;
+	}
+
+	fd_flags = fcntl(accept_fd, F_GETFD);
+	if(!(!!(fd_flags & FD_CLOEXEC) == !!(flags & SOCK_CLOEXEC))) {
+		fprintf(stderr, "CLOEXEC mismatch, got %d instead of %d\n", !!(fd_flags & FD_CLOEXEC), !!(flags & SOCK_CLOEXEC));
+		goto cleanup;
+	}
+
+	access = fcntl(accept_fd, F_GETFL);
+	if(!(!!(access & O_NONBLOCK) == !!(flags & SOCK_NONBLOCK))) {
+		fprintf(stderr, "NONBLOCK flag mismatch, %d vs %d\n", !!(access & O_NONBLOCK), !!(flags & SOCK_NONBLOCK));
+		goto cleanup;
+	}
+
+	close(accept_fd);
+	close(connect_fd);
+
+	fprintf(stderr, "tested CLOEXEC %d, NONBLOCK %d\n", !!(flags & SOCK_CLOEXEC), !!(flags & SOCK_NONBLOCK));
+	return true;
+
+cleanup:
+	close(accept_fd);
+	close(connect_fd);
+	return false;
+}
+
+static int socket_setup(void)
+{
+	struct sockaddr_in addr;
+	int reuseaddr;
+
+	memset(&addr, 0, sizeof(struct sockaddr_in));
+	addr.sin_family = AF_INET;
+	addr.sin_addr.s_addr = htonl(INADDR_ANY);
+	addr.sin_port = htons(TEST_PORT);
+
+	int socket_fd = socket(AF_INET, SOCK_STREAM, 0);
+
+	if(socket_fd == -1) {
+		fprintf(stderr, "socket failed: %s\n", strerror(errno));
+		exit(1);
+	}
+
+	reuseaddr = 1;
+	int ret = setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &reuseaddr, sizeof(reuseaddr));
+
+	if(ret == -1) {
+		fprintf(stderr, "setsockopt failed: %s\n", strerror(errno));
+		exit(1);
+	}
+
+	ret = bind(socket_fd, (struct sockaddr *)&addr, sizeof(struct sockaddr_in));
+
+	if(ret == -1) {
+		fprintf(stderr, "bind failed: %s\n", strerror(errno));
+		exit(1);
+	}
+
+	ret = listen(socket_fd, 5);
+
+	if(ret == -1) {
+		fprintf(stderr, "listen failed: %s\n", strerror(errno));
+		exit(1);
+	}
+
+	return socket_fd;
+}
+
+int main() {
+	memset(&connect_addr, 0, sizeof(connect_addr));
+	connect_addr.sin_family = AF_INET;
+	connect_addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+	connect_addr.sin_port = htons(TEST_PORT);
+
+	for(size_t i = 0; i < 4; i++) {
+		listen_fd = socket_setup();
+		if(!run_test(permutations[i])) {
+			exit(1);
+		}
+		close(listen_fd);
+	}
+}
diff --git a/lib/mlibc/tests/posix/access.c b/lib/mlibc/tests/posix/access.c
new file mode 100644
index 0000000..e0c9f45
--- /dev/null
+++ b/lib/mlibc/tests/posix/access.c
@@ -0,0 +1,30 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <fcntl.h>
+
+#ifdef USE_HOST_LIBC
+#define TEST_FILE "access-host-libc.tmp"
+#else
+#define TEST_FILE "access.tmp"
+#endif
+
+int main() {
+	// Make sure that it wasn't created by a previous test run
+	unlink(TEST_FILE);
+
+	assert(access(TEST_FILE, F_OK) == -1);
+	assert(access(TEST_FILE, W_OK) == -1);
+	assert(access(TEST_FILE, R_OK) == -1);
+	assert(access(TEST_FILE, X_OK) == -1);
+
+	close(open(TEST_FILE, O_CREAT | O_RDWR, 0666));
+
+	assert(access(TEST_FILE, F_OK) == 0);
+	assert(access(TEST_FILE, W_OK) == 0);
+	assert(access(TEST_FILE, R_OK) == 0);
+	assert(access(TEST_FILE, X_OK) == -1);
+
+	unlink(TEST_FILE);
+}
diff --git a/lib/mlibc/tests/posix/alarm.c b/lib/mlibc/tests/posix/alarm.c
new file mode 100644
index 0000000..b8a43e3
--- /dev/null
+++ b/lib/mlibc/tests/posix/alarm.c
@@ -0,0 +1,34 @@
+#include <signal.h>
+#include <assert.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+static volatile int alarms_fired = 0;
+
+static void sigalrm_handler(int signal) {
+	if(signal == SIGALRM)
+		alarms_fired++;
+}
+
+int main() {
+	signal(SIGALRM, sigalrm_handler);
+
+	alarms_fired = 0;
+
+	unsigned int ret = alarm(10);
+	assert(!ret);
+
+	sleep(1);
+
+	ret = alarm(1);
+	assert(ret == 9);
+
+	sleep(2);
+
+	if(alarms_fired != 1) {
+		fprintf(stderr, "alarm handler fired %u times instead of 1\n", alarms_fired);
+		exit(1);
+	}
+}
diff --git a/lib/mlibc/tests/posix/basename.c b/lib/mlibc/tests/posix/basename.c
new file mode 100644
index 0000000..260bf90
--- /dev/null
+++ b/lib/mlibc/tests/posix/basename.c
@@ -0,0 +1,17 @@
+#include <assert.h>
+#include <libgen.h>
+#include <string.h>
+
+int main() {
+	/* intentionally a macro: basename modifies its argument */
+#define test_string(x, expectval) do {                         \
+		char str[] = x;                                \
+		assert(strcmp(basename(str), expectval) == 0); \
+	} while (0)
+
+	test_string("/usr/lib", "lib");
+	test_string("/usr/", "usr");
+	test_string("/", "/");
+	test_string(".", ".");
+	test_string("..", "..");
+}
diff --git a/lib/mlibc/tests/posix/dprintf.c b/lib/mlibc/tests/posix/dprintf.c
new file mode 100644
index 0000000..4746edb
--- /dev/null
+++ b/lib/mlibc/tests/posix/dprintf.c
@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <assert.h>
+#include <errno.h>
+
+#ifdef USE_HOST_LIBC
+#define TEST_FILE "dprintf-host-libc.tmp"
+#else
+#define TEST_FILE "dprintf.tmp"
+#endif
+
+int main() {
+	int fd = open(TEST_FILE, O_RDWR | O_CREAT, 0666);
+	assert(fd > -1);
+
+	int ret = dprintf(fd, "aaa");
+	assert(ret == 3);
+
+	// Check if we can read back the same things.
+	// Also checks to see if the fd is still open,
+	// which is issue #199.
+
+	off_t seek = lseek(fd, 0, SEEK_SET);
+	assert(seek == 0);
+
+	char buf[3];
+	ssize_t num_read = read(fd, buf, 3);
+
+	assert(num_read == 3);
+	assert(buf[0] == 'a'
+		&& buf[1] == 'a'
+		&& buf[2] == 'a');
+
+	// All the tests pass, now we can unlink the file.
+	ret = unlink(TEST_FILE);
+	assert(ret == 0);
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/fdopen.c b/lib/mlibc/tests/posix/fdopen.c
new file mode 100644
index 0000000..1066bfb
--- /dev/null
+++ b/lib/mlibc/tests/posix/fdopen.c
@@ -0,0 +1,37 @@
+#include <stdio.h>
+#include <assert.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#define TEST_FILE "fdopen.tmp"
+
+int main() {
+	int fd = open(TEST_FILE, O_CREAT | O_RDWR, 0666);
+	assert(fd >= 0);
+
+	char *str = "mlibc fdopen test";
+	assert(write(fd, str, strlen(str)));
+
+	// Seek to the beginning, then reopen with fdopen in append mode.
+	lseek(fd, 0, SEEK_SET);
+	FILE *file = fdopen(fd, "a");
+	assert(file);
+
+	// Append and close.
+	str = " appended";
+	fwrite(str, strlen(str), 1, file);
+	fflush(file);
+	fclose(file);
+
+	// Open it again and check that the append succeeded.
+	fd = open(TEST_FILE, O_RDONLY);
+	assert(fd >= 0);
+	file = fdopen(fd, "r");
+	assert(file);
+	str = "mlibc fdopen test appended";
+	char buf[100] = {0};
+	assert(fread(buf, 1, strlen(str), file));
+	assert(!strcmp(buf, str));
+	fclose(file);
+}
diff --git a/lib/mlibc/tests/posix/ffs.c b/lib/mlibc/tests/posix/ffs.c
new file mode 100644
index 0000000..3f7ba84
--- /dev/null
+++ b/lib/mlibc/tests/posix/ffs.c
@@ -0,0 +1,18 @@
+#include <assert.h>
+#include <strings.h>
+#include <limits.h>
+
+int main(void){
+    assert(ffs(0x8000) == 16);
+    assert(ffs(0) == 0);
+	assert(ffs(INT_MAX - 1) ==  2);
+	assert(ffs(INT_MAX) == 1);
+	assert(ffs(INT_MIN) == (int)(sizeof(int) * CHAR_BIT));
+	assert(ffs(INT_MIN + 1) == 1);
+
+	for (int i = 1; i < 0x1000; i++) {
+		assert(ffs(i) - 1 == __builtin_ctz(i));
+	}
+
+    return 0;
+}
diff --git a/lib/mlibc/tests/posix/flockfile.c b/lib/mlibc/tests/posix/flockfile.c
new file mode 100644
index 0000000..982311e
--- /dev/null
+++ b/lib/mlibc/tests/posix/flockfile.c
@@ -0,0 +1,35 @@
+#include <assert.h>
+#include <time.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <unistd.h>
+
+static void *worker(void *arg) {
+	(void)arg;
+	flockfile(stdout);
+	fputs_unlocked("hello from worker", stdout);
+	funlockfile(stdout);
+	return NULL;
+}
+
+int main() {
+	// Check that recursive locking works.
+	assert(!ftrylockfile(stdout));
+	flockfile(stdout);
+	flockfile(stdout);
+	funlockfile(stdout);
+	funlockfile(stdout);
+	funlockfile(stdout);
+
+	assert(!ftrylockfile(stdout));
+
+	pthread_t thread;
+	int ret = pthread_create(&thread, NULL, &worker, NULL);
+	assert(!ret);
+
+	sleep(1);
+	funlockfile(stdout);
+
+	assert(!pthread_join(thread, NULL));
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/fmemopen.c b/lib/mlibc/tests/posix/fmemopen.c
new file mode 100644
index 0000000..4d5046e
--- /dev/null
+++ b/lib/mlibc/tests/posix/fmemopen.c
@@ -0,0 +1,150 @@
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <assert.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define BUFFER0_SIZE 0x1000
+#define BUFFER1 "Hello world"
+#define BUFFER1_SIZE (sizeof(BUFFER1))
+
+int main() {
+	// test seek with mode "r"
+	FILE *f = fmemopen(NULL, BUFFER0_SIZE, "r");
+	assert(f);
+
+	int ret = fseek(f, 0, SEEK_END);
+	assert(!ret);
+	long pos = ftell(f);
+	fprintf(stderr, "pos = %ld\n", pos);
+	// Despite the fact that this is correct behavior (see below),
+	// this sometimes fails on glibc; newlib seems to get this wrong, too.
+	// to quote what posix says about it:
+	// > The stream shall also maintain the size of the current buffer contents;
+	// > use of fseek() or fseeko() on the stream with SEEK_END shall seek relative to this size.
+	// > For modes r and r+ the size shall be set to the value given by the size argument.
+#if !defined(__GLIBC__)
+	assert(pos == BUFFER0_SIZE);
+#endif
+
+	fclose(f);
+
+	// test seek with mode "w"
+	f = fmemopen(NULL, BUFFER0_SIZE, "w");
+	assert(f);
+
+	ret = fseek(f, 0, SEEK_END);
+	assert(!ret);
+	pos = ftell(f);
+	assert(pos == 0);
+
+	fclose(f);
+
+	// test seek with mode "a" and a NULL buffer
+	f = fmemopen(NULL, BUFFER0_SIZE, "a");
+	assert(f);
+
+	ret = fseek(f, 0, SEEK_END);
+	assert(!ret);
+	pos = ftell(f);
+	assert(pos == 0);
+
+	fclose(f);
+
+	// test seek with mode "a" and a buffer containing a '\0'
+	f = fmemopen(BUFFER1, BUFFER1_SIZE + 2, "a");
+	assert(f);
+
+	pos = ftell(f);
+	assert(pos == (long) (BUFFER1_SIZE - 1));
+
+	ret = fseek(f, 0, SEEK_SET);
+	assert(!ret);
+	pos = ftell(f);
+	assert(!pos);
+
+	ret = fseek(f, 0, SEEK_END);
+	assert(!ret);
+	pos = ftell(f);
+	assert(pos == (long) (BUFFER1_SIZE - 1));
+
+	fclose(f);
+
+	// test seek with mode "a" and a buffer not containing a '\0'
+	f = fmemopen(BUFFER1, BUFFER1_SIZE - 2, "a");
+	assert(f);
+
+	ret = fseek(f, 0, SEEK_END);
+	assert(!ret);
+	pos = ftell(f);
+	assert(pos == (long) (BUFFER1_SIZE - 2));
+
+	fclose(f);
+
+	f = fmemopen(BUFFER1, BUFFER1_SIZE, "r");
+	assert(f);
+
+	ret = fseek(f, 0, SEEK_SET);
+	assert(!ret);
+
+	char buf[BUFFER1_SIZE];
+	int read = fread(buf, 1, BUFFER1_SIZE - 2, f);
+	assert(read == BUFFER1_SIZE - 2);
+	assert(!strncmp(BUFFER1, buf, BUFFER1_SIZE - 2));
+
+	fseek(f, 0, SEEK_END);
+
+	read = fread(buf, 1, 2, f);
+	assert(read == 0);
+	assert(feof(f));
+
+	fclose(f);
+
+	// Open a buffer for read+write
+	char *buf1 = strdup(BUFFER1);
+	f = fmemopen(buf1, BUFFER1_SIZE, "w+");
+	assert(f);
+	assert(strlen(BUFFER1) == BUFFER1_SIZE - 1);
+
+	// seek to somewhere in the middle of the buffer
+	fseek(f, BUFFER1_SIZE - 5, SEEK_SET);
+	// write as much data to it as possible
+	read = fwrite(BUFFER1, 1, 9, f);
+	rewind(f);
+
+	// seek the the same position in the middle of the buffer
+	ret = fseek(f, BUFFER1_SIZE - 5, SEEK_SET);
+	assert(!ret);
+	memset(buf, 0, BUFFER1_SIZE);
+	// read what we just wrote
+	read = fread(buf, 1, 5, f);
+	// check that the write got correctly truncated
+	fprintf(stderr, "buf '%s' (%zu)\n", buf, strlen(buf));
+	assert(!strncmp(BUFFER1, buf, 4) && strlen(buf) == 4);
+
+	fclose(f);
+	free(buf1);
+
+	char *buf2 = strdup(BUFFER1);
+	f = fmemopen(buf2, 0, "r");
+	assert(f || errno == EINVAL);
+
+	if(f) {
+		memset(buf, 0, BUFFER1_SIZE);
+		read = fread(buf, 10, 1, f);
+		assert(!read);
+		rewind(f);
+
+		read = fwrite(BUFFER1, 1, 12, f);
+		assert(read == 0);
+
+		fclose(f);
+	}
+	free(buf2);
+
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/fopencookie.c b/lib/mlibc/tests/posix/fopencookie.c
new file mode 100644
index 0000000..4325038
--- /dev/null
+++ b/lib/mlibc/tests/posix/fopencookie.c
@@ -0,0 +1,69 @@
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+struct testcookie {
+	bool read;
+	bool write;
+	bool seek;
+	bool close;
+};
+
+ssize_t cookie_read(void *c, char *buf, size_t size) {
+	(void) buf;
+	struct testcookie *cookie = c;
+	cookie->read = true;
+	return size;
+}
+
+ssize_t cookie_write(void *c, const char *buf, size_t size) {
+	(void) buf;
+	struct testcookie *cookie = c;
+	cookie->write = true;
+	return size;
+}
+
+int cookie_seek(void *c, off64_t *offset, int whence) {
+	(void) offset;
+	(void) whence;
+	struct testcookie *cookie = c;
+	cookie->seek = true;
+	return 0;
+}
+
+int cookie_close(void *c) {
+	struct testcookie *cookie = c;
+	cookie->close = true;
+	return 0;
+}
+
+int main() {
+	struct testcookie cookie = { false, false, false, false };
+
+	cookie_io_functions_t funcs = {
+		.read = cookie_read,
+		.write = cookie_write,
+		.seek = cookie_seek,
+		.close = cookie_close,
+	};
+
+	FILE *stream = fopencookie(&cookie, "w+", funcs);
+	assert(stream);
+
+	unsigned char buf[1];
+	int ret = fread(buf, 1, 1, stream);
+	assert(ret == 1);
+	ret = fwrite(buf, 1, 1, stream);
+	assert(ret == 1);
+	ret = fseek(stream, 0, SEEK_SET);
+	assert(!ret);
+
+	ret = fclose(stream);
+	assert(!ret);
+
+	assert(cookie.read && cookie.write && cookie.seek && cookie.close);
+}
diff --git a/lib/mlibc/tests/posix/getaddrinfo.c b/lib/mlibc/tests/posix/getaddrinfo.c
new file mode 100644
index 0000000..d52c93f
--- /dev/null
+++ b/lib/mlibc/tests/posix/getaddrinfo.c
@@ -0,0 +1,52 @@
+#include <netdb.h>
+#include <assert.h>
+#include <stddef.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <stdio.h>
+
+int main() {
+	struct addrinfo *res = NULL;
+	struct addrinfo hints = {0};
+	hints.ai_family = AF_UNSPEC;
+	hints.ai_socktype = SOCK_STREAM;
+	hints.ai_protocol = IPPROTO_TCP;
+
+	int ret = getaddrinfo(NULL, "443", &hints, &res);
+	assert(ret == 0);
+
+	struct sockaddr_in *addr = (struct sockaddr_in*)(res[0].ai_addr);
+	assert(addr->sin_port == htons(443));
+	assert(res[0].ai_socktype == SOCK_STREAM);
+	assert(res[0].ai_protocol == IPPROTO_TCP);
+
+	freeaddrinfo(res);
+	res = NULL;
+
+	/* check we can resolve any domain */
+	ret = getaddrinfo("example.net", NULL, &hints, &res);
+	assert(ret == 0);
+
+	freeaddrinfo(res);
+	res = NULL;
+
+	hints.ai_flags = AI_NUMERICHOST;
+	ret = getaddrinfo("10.10.10.10", NULL, &hints, &res);
+	assert(ret == 0);
+
+	addr = (struct sockaddr_in*)res[0].ai_addr;
+	assert((addr->sin_addr.s_addr & 0xFF) == 10);
+	assert(((addr->sin_addr.s_addr >> 8) & 0xFF) == 10);
+	assert(((addr->sin_addr.s_addr >> 16) & 0xFF) == 10);
+	assert(((addr->sin_addr.s_addr >> 24) & 0xFF) == 10);
+
+	freeaddrinfo(res);
+	res = NULL;
+
+	ret = getaddrinfo("example.net", NULL, &hints, &res);
+	assert(ret == EAI_NONAME);
+
+	freeaddrinfo(res);
+
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/getcwd.c b/lib/mlibc/tests/posix/getcwd.c
new file mode 100644
index 0000000..f3ba8da
--- /dev/null
+++ b/lib/mlibc/tests/posix/getcwd.c
@@ -0,0 +1,22 @@
+#include <assert.h>
+#include <limits.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+int main() {
+	char buf[PATH_MAX];
+	char *ret = getcwd(buf, PATH_MAX);
+
+	assert(ret);
+	assert((strlen(ret) == strlen(buf)) && strlen(ret));
+	assert(!strcmp(ret, buf));
+
+	char *ret2 = getcwd(NULL, 0);
+	assert(ret2);
+	assert(strlen(ret2));
+	assert(!strcmp(ret, ret2));
+	free(ret2);
+
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/getdelim.c b/lib/mlibc/tests/posix/getdelim.c
new file mode 100644
index 0000000..bc43ef6
--- /dev/null
+++ b/lib/mlibc/tests/posix/getdelim.c
@@ -0,0 +1,90 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <unistd.h>
+#include <string.h>
+
+#ifdef USE_HOST_LIBC
+#define TEST_FILE "getdelim-host-libc.tmp"
+#else
+#define TEST_FILE "getdelim.tmp"
+#endif
+
+int main(void) {
+	FILE *fp;
+	char *line = NULL;
+	size_t len = 0;
+	ssize_t read;
+
+	// We have to open the file for writing and then reading separately,
+	// as mlibc doesn't allow us to do both at the same time (yet).
+	fp = fopen(TEST_FILE, "w");
+	assert(fp);
+	fputs("foo\nbar\nbaz\nquux\n", fp);
+	fclose(fp);
+
+	fp = fopen(TEST_FILE, "r");
+	assert(fp);
+	while ((read = getline(&line, &len, fp)) != -1) {
+		printf("read line of length %zd, capacity %zu\n", read, len);
+	}
+	assert(!ferror(fp));
+	free(line);
+	fclose(fp);
+
+	size_t nchars = 10000;
+	fp = fopen(TEST_FILE, "w");
+	assert(fp);
+	for (size_t i = 0; i < nchars; i++)
+		fputc('a', fp);
+	fputc('b', fp);
+	fclose(fp);
+
+	line = NULL;
+	len = 0;
+	fp = fopen(TEST_FILE, "r");
+	assert(fp);
+	while ((read = getdelim(&line, &len, 'b', fp)) != -1) {
+		printf("read line of length %zd, capacity %zu\n", read, len);
+		assert((size_t)read == nchars + 1);
+	}
+
+	assert(len > nchars + 1);
+	assert(!ferror(fp));
+	assert(feof(fp));
+
+	assert(getdelim(&line, &len, 'b', fp) == -1);
+	assert(feof(fp));
+
+	free(line);
+	fclose(fp);
+
+	fp = fopen(TEST_FILE, "w");
+	assert(fp);
+	assert(fwrite("1234ef\0f", 1, 8, fp) == 8);
+	fclose(fp);
+
+	fp = fopen(TEST_FILE, "r");
+	assert(fp);
+
+	/* test with line = NULL and large len */
+	line = NULL;
+	len = (size_t) ~0;
+	assert(getdelim(&line, &len, 'e', fp) == 5);
+	assert(!memcmp(line, "1234e", 6));
+	assert(5 < len);
+
+	/* test handling of internal nulls */
+	assert(getdelim(&line, &len, 'e', fp) == 3);
+	assert(!memcmp(line, "f\0f", 4));
+	assert(3 < len);
+
+	/* test handling of EOF */
+	assert(getdelim(&line, &len, 'e', fp) == -1);
+
+	free(line);
+	fclose(fp);
+
+	// Delete the file
+	unlink(TEST_FILE);
+}
diff --git a/lib/mlibc/tests/posix/getnameinfo.c b/lib/mlibc/tests/posix/getnameinfo.c
new file mode 100644
index 0000000..d22a0eb
--- /dev/null
+++ b/lib/mlibc/tests/posix/getnameinfo.c
@@ -0,0 +1,22 @@
+#include <netdb.h>
+#include <assert.h>
+#include <arpa/inet.h>
+#include <stddef.h>
+#include <string.h>
+
+int main() {
+	struct sockaddr_in addr;
+	addr.sin_family = AF_INET;
+	assert(inet_pton(AF_INET, "127.0.0.1", &addr.sin_addr));
+
+	char host[64];
+	assert(!getnameinfo((struct sockaddr*)&addr, sizeof(addr), host,
+				sizeof(host), NULL, 0, 0));
+
+	assert(inet_pton(AF_INET, "8.8.8.8", &addr.sin_addr));
+
+	assert(!getnameinfo((struct sockaddr*)&addr, sizeof(addr), host,
+				sizeof(host), NULL, 0, 0));
+	assert(!strcmp(host, "dns.google"));
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/getservbyname.c b/lib/mlibc/tests/posix/getservbyname.c
new file mode 100644
index 0000000..8c51710
--- /dev/null
+++ b/lib/mlibc/tests/posix/getservbyname.c
@@ -0,0 +1,27 @@
+#include <assert.h>
+#include <netdb.h>
+#include <string.h>
+#include <arpa/inet.h>
+
+int main() {
+	struct servent *ret = getservbyname("http", "tcp");
+	assert(ret);
+	assert(!strcmp("http", ret->s_name));
+	assert(ret->s_port == htons(80));
+	assert(!strcmp("tcp", ret->s_proto));
+
+	ret = getservbyname("http", NULL);
+	assert(ret);
+	assert(!strcmp("http", ret->s_name));
+	assert(ret->s_port == htons(80));
+	assert(!strcmp("tcp", ret->s_proto));
+
+	ret = getservbyname("babel", "udp");
+	assert(ret);
+	ret = getservbyname("babel", "tcp");
+	assert(!ret);
+
+	ret = getservbyname("", NULL);
+	assert(!ret);
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/getservbyport.c b/lib/mlibc/tests/posix/getservbyport.c
new file mode 100644
index 0000000..f522d71
--- /dev/null
+++ b/lib/mlibc/tests/posix/getservbyport.c
@@ -0,0 +1,28 @@
+#include <netdb.h>
+#include <arpa/inet.h>
+#include <string.h>
+#include <assert.h>
+#include <stdio.h>
+
+int main() {
+	struct servent *ret = getservbyport(htons(80), "tcp");
+	assert(ret);
+	assert(!strcmp("http", ret->s_name));
+	assert(ret->s_port == htons(80));
+	assert(!strcmp("tcp", ret->s_proto));
+
+	ret = getservbyport(htons(80), NULL);
+	assert(ret);
+	assert(!strcmp("http", ret->s_name));
+	assert(ret->s_port == htons(80));
+	assert(!strcmp("tcp", ret->s_proto));
+
+	ret = getservbyport(htons(6696), "udp");
+	assert(ret);
+	ret = getservbyport(htons(6696), "tcp");
+	assert(!ret);
+
+	ret = getservbyport(htons(0), NULL);
+	assert(!ret);
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/grp.c b/lib/mlibc/tests/posix/grp.c
new file mode 100644
index 0000000..3d334fe
--- /dev/null
+++ b/lib/mlibc/tests/posix/grp.c
@@ -0,0 +1,110 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <grp.h>
+#include <unistd.h>
+#include <assert.h>
+#include <string.h>
+#include <errno.h>
+#include <stdbool.h>
+
+void check_root_group(struct group *grp) {
+	assert(grp);
+
+	printf("group name: %s\n", grp->gr_name);
+	fflush(stdout);
+
+	assert(grp->gr_gid == 0);
+	assert(!strcmp(grp->gr_name, "root"));
+
+	// Depending on your system, the root group may or may not contain the root user.
+	if (grp->gr_mem[0] != NULL) {
+		bool found = false;
+		for (size_t i = 0; grp->gr_mem[i] != NULL; i++) {
+			printf("group member: %s\n", grp->gr_mem[i]);
+			fflush(stdout);
+
+			if (!strcmp(grp->gr_mem[i], "root")) {
+				found = true;
+				break;
+			}
+		}
+		assert(found);
+	}
+}
+
+int main()
+{
+	struct group grp, *result = NULL;
+	char *buf;
+	size_t bufsize;
+	int s;
+	bool password = false;
+
+	bufsize = sysconf(_SC_GETGR_R_SIZE_MAX);
+	assert(bufsize > 0 && bufsize < 0x100000);
+
+	buf = malloc(bufsize);
+	assert(buf);
+
+	s = getgrnam_r("root", &grp, buf, bufsize, &result);
+	assert(!s);
+	check_root_group(result);
+
+	s = getgrgid_r(0, &grp, buf, bufsize, &result);
+	assert(!s);
+	check_root_group(result);
+
+	result = getgrnam("root");
+	check_root_group(result);
+
+	result = getgrgid(0);
+	check_root_group(result);
+
+	result = getgrnam("this_group_doesnt_exist");
+	assert(!result);
+#ifndef USE_HOST_LIBC
+	// This is not guaranteed.
+	assert(errno == ESRCH);
+#endif
+
+	s = getgrnam_r("this_group_doesnt_exist", &grp, buf, bufsize, &result);
+	assert(!result);
+#ifndef USE_HOST_LIBC
+	// This is not guaranteed.
+	assert(s == ESRCH);
+#endif
+
+	errno = 0;
+	setgrent();
+	assert(errno == 0);
+
+	result = getgrent();
+	assert(result);
+	grp.gr_name = strdup(result->gr_name);
+	if(result->gr_passwd) {
+		password = true;
+	}
+	grp.gr_passwd = strdup(result->gr_passwd);
+	grp.gr_gid = result->gr_gid;
+	assert(grp.gr_name);
+	if(password)
+		assert(grp.gr_passwd);
+
+	assert(grp.gr_name);
+	if(password)
+		assert(grp.gr_passwd);
+
+	endgrent();
+
+	result = getgrent();
+	assert(result);
+	assert(strcmp(result->gr_name, grp.gr_name) == 0);
+	if(password)
+		assert(strcmp(result->gr_passwd, grp.gr_passwd) == 0);
+	assert(result->gr_gid == grp.gr_gid);
+
+	free(grp.gr_name);
+	if(password)
+		free(grp.gr_passwd);
+	free(buf);
+}
diff --git a/lib/mlibc/tests/posix/if_indextoname.c b/lib/mlibc/tests/posix/if_indextoname.c
new file mode 100644
index 0000000..15dc12a
--- /dev/null
+++ b/lib/mlibc/tests/posix/if_indextoname.c
@@ -0,0 +1,11 @@
+#include <assert.h>
+#include <net/if.h>
+#include <stdio.h>
+
+int main() {
+	char name[IF_NAMESIZE];
+
+	assert(name == if_indextoname(1, name));
+	printf("test: name '%s'\n", name);
+	assert(1 == if_nametoindex(name));
+}
diff --git a/lib/mlibc/tests/posix/index.c b/lib/mlibc/tests/posix/index.c
new file mode 100644
index 0000000..63be75d
--- /dev/null
+++ b/lib/mlibc/tests/posix/index.c
@@ -0,0 +1,20 @@
+#include <assert.h>
+#include <strings.h>
+#include <stddef.h>
+
+int main() {
+  char str[] = "This is a sample string";
+  char *pch;
+  // The character 's' is at position 4, 7, 11 and 18
+  pch = index(str, 's');
+  assert(pch - str + 1 == 4);
+  pch = index(pch + 1, 's');
+  assert(pch - str + 1 == 7);
+  pch = index(pch + 1, 's');
+  assert(pch - str + 1 == 11);
+  pch = index(pch + 1, 's');
+  assert(pch - str + 1 == 18);
+  pch = index(pch + 1, 's');
+  assert(pch == NULL);
+  return 0;
+}
diff --git a/lib/mlibc/tests/posix/inet_ntop.c b/lib/mlibc/tests/posix/inet_ntop.c
new file mode 100644
index 0000000..feca26c
--- /dev/null
+++ b/lib/mlibc/tests/posix/inet_ntop.c
@@ -0,0 +1,30 @@
+#include <arpa/inet.h>
+#include <stdio.h>
+#include <assert.h>
+#include <string.h>
+
+int main() {
+	struct in_addr addr;
+	addr.s_addr = (1 << 24) |
+		(1 << 16) | (1 << 8) | 1;
+	char buf[INET_ADDRSTRLEN];
+	assert(inet_ntop(AF_INET, &addr, buf, INET_ADDRSTRLEN) != NULL);
+	assert(strncmp("1.1.1.1", buf, INET_ADDRSTRLEN) == 0);
+
+	struct in6_addr addr2 = { .s6_addr = {0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0x1, 0, 0, 0, 0, 0, 0x1} };
+	char buf2[INET6_ADDRSTRLEN];
+	assert(inet_ntop(AF_INET6, &addr2, buf2, INET6_ADDRSTRLEN) != NULL);
+	assert(strncmp("2001:db8::1:0:0:1", buf2, INET6_ADDRSTRLEN) == 0);
+
+	struct in6_addr addr3 = { .s6_addr = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1} };
+	char buf3[INET6_ADDRSTRLEN];
+	assert(inet_ntop(AF_INET6, &addr3, buf3, INET6_ADDRSTRLEN) != NULL);
+	assert(strncmp("::1", buf3, INET6_ADDRSTRLEN) == 0);
+
+	struct in6_addr addr4 = { .s6_addr = {0x20, 0x1, 0xd, 0xb8, 00, 00, 00, 0x1, 00, 0x1, 00, 0x1, 00, 0x1, 00, 0x1} };
+	char buf4[INET6_ADDRSTRLEN];
+	assert(inet_ntop(AF_INET6, &addr4, buf4, INET6_ADDRSTRLEN) != NULL);
+	assert(strncmp("2001:db8:0:1:1:1:1:1", buf4, INET6_ADDRSTRLEN) == 0);
+
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/inet_pton.c b/lib/mlibc/tests/posix/inet_pton.c
new file mode 100644
index 0000000..6c0f342
--- /dev/null
+++ b/lib/mlibc/tests/posix/inet_pton.c
@@ -0,0 +1,16 @@
+#include <arpa/inet.h>
+#include <assert.h>
+
+int main() {
+	struct in_addr addr;
+	assert(inet_pton(AF_INET, "1.1.1.1", &addr));
+	assert((addr.s_addr & 0xFF) == 1);
+	assert(((addr.s_addr >> 8) & 0xFF) == 1);
+	assert(((addr.s_addr >> 16) & 0xFF) == 1);
+	assert(((addr.s_addr >> 24) & 0xFF) == 1);
+
+	assert(!inet_pton(AF_INET, "256.999.1234.555", &addr));
+	assert(!inet_pton(AF_INET, "a.b.c.d", &addr));
+	return 0;
+}
+
diff --git a/lib/mlibc/tests/posix/memrchr.c b/lib/mlibc/tests/posix/memrchr.c
new file mode 100644
index 0000000..99e3e25
--- /dev/null
+++ b/lib/mlibc/tests/posix/memrchr.c
@@ -0,0 +1,25 @@
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+int main () {
+	char str[] = "The Last Supper by Leonardo da Vinci";
+	char *str_temp;
+
+	// Test strstr
+	str_temp = strstr(str, "Supper"); /* Find a substring in the string */
+	assert(!strcmp(str_temp, "Supper by Leonardo da Vinci"));
+
+	/* Following calls use memory APIs for the above tasks */
+	// Test memchr
+	str_temp = (char *)memchr((void *)str, 'L', strlen(str));
+	assert(!strcmp(str_temp, "Last Supper by Leonardo da Vinci"));
+
+	// Test memrchr
+	str_temp = (char *)memrchr((void *)str, 'L', strlen(str));
+	assert(!strcmp(str_temp, "Leonardo da Vinci"));
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/mkstemp.c b/lib/mlibc/tests/posix/mkstemp.c
new file mode 100644
index 0000000..d06783e
--- /dev/null
+++ b/lib/mlibc/tests/posix/mkstemp.c
@@ -0,0 +1,70 @@
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+
+void validate_pattern(char *p) {
+	assert(memcmp(p, "XXXXXX", 6));
+	assert(memchr(p, 0, 6) == NULL);
+
+	for (int i = 0; i < 6; i++) {
+		assert(isalnum(p[i]));
+	}
+}
+
+int main() {
+	int ret;
+
+	// Make sure the patterns themselves cannot be chosen.  This
+	// *could* happen on glibc, or if we widen the character set
+	// used for generating random names. Odds are 1 in 60 billion,
+	// but I'd rather not worry about this.
+	ret = open("prefixXXXXXX", O_RDWR | O_CREAT | O_EXCL, 0600);
+	assert(ret >= 0 || (ret == -1 && errno == EEXIST));
+	ret = open("longprefixXXXXXXlongsuffix", O_RDWR | O_CREAT | O_EXCL, 0600);
+	assert(ret >= 0 || (ret == -1 && errno == EEXIST));
+
+	ret = mkstemp("short");
+	assert(ret == -1);
+	assert(errno == EINVAL);
+
+	ret = mkstemp("lessthan6XXX");
+	assert(ret == -1);
+	assert(errno == EINVAL);
+
+	ret = mkstemps("lessthan6XXXswithsuffix", 11);
+	assert(ret == -1);
+	assert(errno == EINVAL);
+
+	char *p = strdup("prefixXXXXXX");
+	ret = mkstemp(p);
+	// We can't really protect against EEXIST...
+	assert(ret >= 0 || (ret == -1 && errno == EEXIST));
+	assert(!memcmp(p, "prefix", 6));
+	assert(p[12] == 0);
+	validate_pattern(p + 6);
+
+	if (ret >= 0) {
+		ret = close(ret);
+		assert(!ret);
+	}
+	free(p);
+
+	p = strdup("longprefixXXXXXXlongsuffix");
+	ret = mkstemps(p, 10);
+	// We can't really protect against EEXIST...
+	assert(ret >= 0 || (ret == -1 && errno == EEXIST));
+	assert(!memcmp(p, "longprefix", 10));
+	assert(!memcmp(p + 16, "longsuffix", 10));
+	assert(p[26] == 0);
+	validate_pattern(p + 10);
+
+	if (ret >= 0) {
+		ret = close(ret);
+		assert(!ret);
+	}
+	free(p);
+}
diff --git a/lib/mlibc/tests/posix/open_memstream.c b/lib/mlibc/tests/posix/open_memstream.c
new file mode 100644
index 0000000..0347003
--- /dev/null
+++ b/lib/mlibc/tests/posix/open_memstream.c
@@ -0,0 +1,65 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+
+#define WRITE_NO 1024
+
+int main() {
+	size_t size;
+	char *buf;
+
+	FILE *fp = open_memstream(&buf, &size);
+	assert(fp);
+
+	char c = 'A';
+	for (size_t i = 0; i < WRITE_NO; i++)
+		assert(fwrite(&c, sizeof(char), 1, fp) == 1);
+
+	// Flush the file to update the pointers.
+	assert(!fflush(fp));
+
+	assert(size == WRITE_NO);
+	for (size_t i = 0; i < size; i++)
+		assert(buf[i] == c);
+
+	// Check if the stream maintains a null-bye at the end.
+	assert(buf[size] == '\0');
+
+	// Stream should be expanded, size should be == 2*WRITE_NO.
+	assert(!fseek(fp, WRITE_NO, SEEK_END));
+	assert(!fflush(fp));
+	assert(size == 2*WRITE_NO);
+	assert(buf[size] == '\0');
+
+	// Check if it's filled with zero's.
+	for (size_t i = WRITE_NO; i < size; i++)
+		assert(buf[i] == '\0');
+
+	// Go back and overwrite the 0's with 'B'.
+	assert(!fseek(fp, -WRITE_NO, SEEK_CUR));
+	c = 'B';
+	for (size_t i = 0; i < WRITE_NO; i++)
+		assert(fwrite(&c, sizeof(char), 1, fp) == 1);
+
+	// Check if that happened.
+	assert(size == 2*WRITE_NO);
+	for (size_t i = WRITE_NO; i < size; i++)
+		assert(buf[i] == c);
+	assert(buf[size] == '\0');
+
+	// Go to the front and write 'B'.
+	assert(!fseek(fp, 0, SEEK_SET));
+	for (size_t i = 0; i < WRITE_NO; i++)
+		assert(fwrite(&c, sizeof(char), 1, fp) == 1);
+
+	// Check if that happened.
+	assert(size == 2*WRITE_NO);
+	for (size_t i = 0; i < size; i++)
+		assert(buf[i] == c);
+	assert(buf[size] == '\0');
+
+	// Close the file, we have tested everything.
+	assert(!fclose(fp));
+	free(buf);
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/pause.c b/lib/mlibc/tests/posix/pause.c
new file mode 100644
index 0000000..054c5a4
--- /dev/null
+++ b/lib/mlibc/tests/posix/pause.c
@@ -0,0 +1,49 @@
+#include <assert.h>
+#include <signal.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <sys/wait.h>
+
+static void noop(int x) {
+	(void)x;
+}
+
+int main() {
+	signal(SIGUSR1, &noop);
+
+	int pid;
+	switch(pid = fork()) {
+	case -1:
+		perror("fork");
+		abort();
+	case 0:
+		pause();
+		assert(errno == EINTR);
+		return 0;
+	default:
+		while (1) {
+			usleep(100);
+			kill(pid, SIGUSR1);
+			usleep(100);
+			int status;
+
+			errno = 0;
+			if (waitpid(-1, &status, WNOHANG) <= 0) {
+				if (errno && errno != EAGAIN) {
+					perror("wait");
+					kill(pid, SIGKILL);
+				}
+				continue;
+			}
+
+			if (!WIFEXITED(status)) {
+				printf("wait returned %x\n", status);
+				abort();
+			}
+
+			return WEXITSTATUS(status);
+		}
+	}
+}
diff --git a/lib/mlibc/tests/posix/popen.c b/lib/mlibc/tests/posix/popen.c
new file mode 100644
index 0000000..87bbde2
--- /dev/null
+++ b/lib/mlibc/tests/posix/popen.c
@@ -0,0 +1,42 @@
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+#include <unistd.h>
+
+#ifdef USE_HOST_LIBC
+#define TEST_FILE "popen-host-libc.tmp"
+#else
+#define TEST_FILE "popen.tmp"
+#endif
+
+#define TEST_STRING1 "the quick brown fox jumps over the lazy dog"
+#define TEST_STRING1_LEN 43
+#define TEST_STRING2 "Lorem ipsum dolor sit amet, consectetur adipiscing elit"
+#define TEST_STRING2_LEN 55
+
+int main() {
+	// Test reading
+	FILE *f1 = popen("echo -n '" TEST_STRING1 "'", "r");
+	assert(f1);
+	char buf1[TEST_STRING1_LEN];
+	assert(fread(buf1, 1, TEST_STRING1_LEN, f1) == TEST_STRING1_LEN);
+	assert(memcmp(buf1, TEST_STRING1, TEST_STRING1_LEN) == 0);
+	pclose(f1);
+
+	// Test writing
+	FILE *f2 = popen("cat - > " TEST_FILE, "w");
+	assert(f2);
+	assert(fwrite(TEST_STRING2, 1, TEST_STRING2_LEN, f2) == TEST_STRING2_LEN);
+	pclose(f2);
+
+	// Read test file back
+	FILE *test_file = fopen(TEST_FILE, "r");
+	assert(test_file);
+	char buf2[TEST_STRING2_LEN];
+	assert(fread(buf2, 1, TEST_STRING2_LEN, test_file) == TEST_STRING2_LEN);
+	assert(memcmp(buf2, TEST_STRING2, TEST_STRING2_LEN) == 0);
+	fclose(test_file);
+	assert(unlink(TEST_FILE) == 0);
+
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/posix-timer.c b/lib/mlibc/tests/posix/posix-timer.c
new file mode 100644
index 0000000..d097818
--- /dev/null
+++ b/lib/mlibc/tests/posix/posix-timer.c
@@ -0,0 +1,47 @@
+#include <assert.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/time.h>
+#include <time.h>
+
+int main() {
+	struct sigevent evp;
+	memset(&evp, 0, sizeof(evp));
+
+	sigset_t set;
+	sigemptyset(&set);
+	sigaddset(&set, SIGUSR1);
+	sigprocmask(SIG_BLOCK, &set, 0);
+	evp.sigev_notify = SIGEV_SIGNAL;
+	evp.sigev_signo = SIGUSR1;
+
+	struct timeval start;
+	gettimeofday(&start, NULL);
+
+	timer_t timer;
+	if (timer_create(CLOCK_MONOTONIC, &evp, &timer)) {
+		perror("timer_create");
+		exit(1);
+	}
+
+	struct itimerspec spec;
+	memset(&spec, 0, sizeof(spec));
+	spec.it_value.tv_sec = 1;
+	spec.it_value.tv_nsec = 0;
+
+	int sig;
+	timer_settime(timer, 0, &spec, NULL);
+	sigwait(&set, &sig);
+
+	struct timeval end;
+	gettimeofday(&end, NULL);
+	timer_delete(timer);
+
+	double diff = end.tv_sec - start.tv_sec;
+	diff += (end.tv_usec - start.tv_usec) / 1000000.0;
+	assert(diff >= 1.0);
+
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/posix_memalign.c b/lib/mlibc/tests/posix/posix_memalign.c
new file mode 100644
index 0000000..34652b9
--- /dev/null
+++ b/lib/mlibc/tests/posix/posix_memalign.c
@@ -0,0 +1,21 @@
+#include <stdlib.h>
+#include <assert.h>
+#include <stdint.h>
+#include <errno.h>
+
+int main() {
+	void *p = NULL;
+
+	// align must be a power of two
+	assert(posix_memalign(&p, 3, 1) == EINVAL && p == NULL);
+
+	// align must be a multiple of sizeof(void *)
+	assert(posix_memalign(&p, sizeof(void *) / 2, 8) == EINVAL && p == NULL);
+
+	assert(posix_memalign(&p, sizeof(void *), sizeof(void *)) == 0 && p != NULL && (uintptr_t)p % sizeof(void *) == 0);
+	free(p);
+	assert(posix_memalign(&p, 256, 1) == 0 && p != NULL && (uintptr_t)p % 256 == 0);
+	free(p);
+	assert(posix_memalign(&p, 256, 256) == 0 && p != NULL && (uintptr_t)p % 256 == 0);
+	free(p);
+}
diff --git a/lib/mlibc/tests/posix/posix_spawn.c b/lib/mlibc/tests/posix/posix_spawn.c
new file mode 100644
index 0000000..cc5ccff
--- /dev/null
+++ b/lib/mlibc/tests/posix/posix_spawn.c
@@ -0,0 +1,38 @@
+#include <stdlib.h>
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <unistd.h>
+#include <spawn.h>
+#include <sys/wait.h>
+
+extern char **environ;
+
+void run_cmd(char *cmd)
+{
+    pid_t pid;
+    char *argv[] = {"sh", "-c", cmd, NULL};
+    int status;
+    printf("Run command: %s\n", cmd);
+    status = posix_spawn(&pid, "/bin/sh", NULL, NULL, argv, environ);
+    if(status == 0) {
+        printf("Child pid: %i\n", pid);
+        if(waitpid(pid, &status, 0) != -1) {
+            printf("Child exited with status %i\n", status);
+        printf("Child exit status: %i\n", WEXITSTATUS(status));
+        assert(WEXITSTATUS(status) == 0);
+        } else {
+            perror("waitpid");
+        assert(0 == 1);
+        }
+    } else {
+        printf("posix_spawn: %s\n", strerror(status));
+    assert(0 == 1);
+    }
+}
+
+int main() {
+    run_cmd(":");
+    return 0;
+}
diff --git a/lib/mlibc/tests/posix/pthread_atfork.c b/lib/mlibc/tests/posix/pthread_atfork.c
new file mode 100644
index 0000000..45be136
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_atfork.c
@@ -0,0 +1,54 @@
+#include <assert.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/wait.h>
+
+_Atomic int prepare_order = 0;
+_Atomic int parent_order = 0;
+_Atomic int child_order = 0;
+
+static void prepare1() { prepare_order = 1; }
+static void prepare2() { prepare_order = 2; }
+
+static void parent1() { parent_order = 1; }
+static void parent2() { parent_order = 2; }
+
+static void child1() { child_order = 1; }
+static void child2() { child_order = 2; }
+
+int main() {
+	assert(!pthread_atfork(prepare1, parent1, child1));
+	assert(!pthread_atfork(prepare2, parent2, child2));
+
+	pid_t pid = fork();
+	assert(pid >= 0);
+
+	if (!pid) {
+		assert(child_order == 2);
+		exit(0);
+	} else {
+		assert(prepare_order == 1);
+		assert(parent_order == 2);
+
+		while (1) {
+			int status = 0;
+
+			int ret = waitpid(pid, &status, 0);
+
+			if (ret == -1 && errno == EINTR)
+				continue;
+
+			assert(ret > 0);
+
+			if (WIFSIGNALED(status) && WTERMSIG(status) == SIGABRT)
+				return 1;
+
+			return WEXITSTATUS(status);
+		}
+	}
+
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/pthread_attr.c b/lib/mlibc/tests/posix/pthread_attr.c
new file mode 100644
index 0000000..c901a90
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_attr.c
@@ -0,0 +1,157 @@
+#include <pthread.h>
+#include <assert.h>
+#include <errno.h>
+#include <alloca.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <signal.h>
+
+static void test_detachstate() {
+	pthread_attr_t attr;
+	assert(!pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED));
+	int detachstate;
+	assert(!pthread_attr_getdetachstate(&attr, &detachstate));
+	assert(detachstate == PTHREAD_CREATE_DETACHED);
+	assert(pthread_attr_setdetachstate(&attr, 2* (PTHREAD_CREATE_DETACHED +
+				PTHREAD_CREATE_JOINABLE)) == EINVAL);
+}
+
+static void *stacksize_worker(void *arg) {
+	size_t default_stacksize = (*(size_t*)arg);
+	size_t alloc_size = default_stacksize + default_stacksize/2;
+	void *area = alloca(alloc_size);
+	// If the allocated stack was not enough this will crash.
+	*(volatile int*)(area + alloc_size) = 1;
+	return NULL;
+}
+
+static void test_stacksize() {
+	pthread_attr_t attr;
+	assert(!pthread_attr_init(&attr));
+	size_t stacksize;
+	assert(!pthread_attr_getstacksize(&attr, &stacksize));
+	assert(!pthread_attr_setstacksize(&attr, stacksize * 2));
+	pthread_t thread;
+	assert(!pthread_create(&thread, &attr, stacksize_worker, &stacksize));
+	assert(!pthread_join(thread, NULL));
+}
+
+static void test_guardsize() {
+	pthread_attr_t attr;
+	assert(!pthread_attr_init(&attr));
+	assert(!pthread_attr_setguardsize(&attr, 0));
+	size_t guardsize;
+	assert(!pthread_attr_getguardsize(&attr, &guardsize));
+	assert(!guardsize);
+}
+
+static void test_scope() {
+	pthread_attr_t attr;
+	assert(!pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM));
+	int scope;
+	assert(!pthread_attr_getscope(&attr, &scope));
+	assert(scope == PTHREAD_SCOPE_SYSTEM);
+	assert(pthread_attr_setscope(&attr, 2* (PTHREAD_SCOPE_SYSTEM +
+				PTHREAD_SCOPE_PROCESS)) == EINVAL);
+}
+
+static void test_inheritsched() {
+	pthread_attr_t attr;
+	assert(!pthread_attr_setinheritsched(&attr, PTHREAD_INHERIT_SCHED));
+	int inheritsched;
+	assert(!pthread_attr_getinheritsched(&attr, &inheritsched));
+	assert(inheritsched == PTHREAD_INHERIT_SCHED);
+	assert(pthread_attr_setinheritsched(&attr, 2* (PTHREAD_INHERIT_SCHED +
+				PTHREAD_EXPLICIT_SCHED)) == EINVAL);
+}
+
+static void test_schedparam() {
+	pthread_attr_t attr;
+	struct sched_param init_param = {0};
+	assert(!pthread_attr_setschedparam(&attr, &init_param));
+	struct sched_param param = {1};
+	assert(!pthread_attr_getschedparam(&attr, &param));
+	assert(param.sched_priority == init_param.sched_priority);
+}
+
+static void test_schedpolicy() {
+	pthread_attr_t attr;
+	assert(!pthread_attr_setschedpolicy(&attr, SCHED_FIFO));
+	int policy;
+	assert(!pthread_attr_getschedpolicy(&attr, &policy));
+	assert(policy == SCHED_FIFO);
+	assert(pthread_attr_setinheritsched(&attr, 2* (SCHED_FIFO + SCHED_RR +
+				SCHED_OTHER)) == EINVAL);
+}
+
+static void *stackaddr_worker(void *arg) {
+	void *addr = *(void**)arg;
+
+	void *sp;
+#if defined(__x86_64__)
+	asm volatile ("mov %%rsp, %0" : "=r"(sp));
+#elif defined(__i386__)
+	asm volatile ("mov %%esp, %0" : "=r"(sp));
+#elif defined(__aarch64__)
+	asm volatile ("mov %0, sp" : "=r"(sp));
+#elif defined (__riscv)
+	asm volatile ("mv %0, sp" : "=r"(sp));
+#else
+#	error Unknown architecture
+#endif
+
+	// Check if our stack pointer is in a sane range.
+	assert(sp > addr);
+	return NULL;
+}
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+static void test_stackaddr() {
+	pthread_attr_t attr;
+	assert(!pthread_attr_init(&attr));
+	size_t size;
+	assert(!pthread_attr_getstacksize(&attr, &size));
+	void *addr = mmap(NULL, size, PROT_READ | PROT_WRITE,
+				MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	assert(!pthread_attr_setstack(&attr, addr, size));
+	assert(!pthread_attr_setguardsize(&attr, 0));
+	void *new_addr;
+	size_t new_size;
+	assert(!pthread_attr_getstack(&attr, &new_addr, &new_size));
+	assert(new_addr == addr);
+	assert(new_size == size);
+
+	pthread_t thread;
+	assert(!pthread_create(&thread, &attr, stackaddr_worker, &addr));
+	assert(!pthread_join(thread, NULL));
+}
+#pragma GCC diagnostic pop
+
+#if !defined(USE_HOST_LIBC) || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 32)
+static void test_stack() {
+	pthread_attr_t attr;
+	void *stackaddr = (void*)1;
+	size_t stacksize = PTHREAD_STACK_MIN;
+
+	assert(!pthread_attr_setstack(&attr, stackaddr, stacksize));
+	void *new_addr;
+	size_t new_size;
+	assert(!pthread_attr_getstack(&attr, &new_addr, &new_size));
+	assert(new_addr == stackaddr);
+	assert(new_size == stacksize);
+}
+#endif
+
+int main() {
+	test_detachstate();
+	test_stacksize();
+	test_guardsize();
+	test_scope();
+	test_inheritsched();
+	test_schedparam();
+	test_schedpolicy();
+	test_stackaddr();
+#if !defined(USE_HOST_LIBC) || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 32)
+	test_stack();
+#endif
+}
diff --git a/lib/mlibc/tests/posix/pthread_barrier.c b/lib/mlibc/tests/posix/pthread_barrier.c
new file mode 100644
index 0000000..213ba8f
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_barrier.c
@@ -0,0 +1,56 @@
+#include <pthread.h>
+#include <unistd.h>
+#include <assert.h>
+
+pthread_barrier_t barrier;
+_Atomic int hitBarrierCount, pastBarrierCount;
+
+static void *worker(void *arg) {
+	(void)arg;
+	hitBarrierCount++;
+	pthread_barrier_wait(&barrier);
+	pastBarrierCount++;
+	return NULL;
+}
+
+int main() {
+	// pthread_barrierattr_t
+	pthread_barrierattr_t attr;
+	pthread_barrierattr_init(&attr);
+
+	int pshared;
+	pthread_barrierattr_getpshared(&attr, &pshared);
+	assert(pshared == PTHREAD_PROCESS_PRIVATE);
+
+	pthread_barrierattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
+	pthread_barrierattr_getpshared(&attr, &pshared);
+	assert(pshared == PTHREAD_PROCESS_SHARED);
+
+	pthread_barrierattr_setpshared(&attr, PTHREAD_PROCESS_PRIVATE);
+	pthread_barrierattr_getpshared(&attr, &pshared);
+	assert(pshared == PTHREAD_PROCESS_PRIVATE);
+
+	// pthread_barrier_t
+	pthread_barrier_init(&barrier, &attr, 3);
+	pthread_barrierattr_destroy(&attr);
+
+	pthread_t thread1;
+	int ret = pthread_create(&thread1, NULL, &worker, NULL);
+	assert(!ret);
+
+	pthread_t thread2;
+	ret = pthread_create(&thread2, NULL, &worker, NULL);
+	assert(!ret);
+
+	sleep(1);
+
+	// Make sure the barrier actually stops threads from proceeding.
+	assert(pastBarrierCount == 0);
+	assert(hitBarrierCount <= 2);
+
+	hitBarrierCount++;
+	pthread_barrier_wait(&barrier);
+	assert(hitBarrierCount == 3);
+
+	pthread_barrier_destroy(&barrier);
+}
diff --git a/lib/mlibc/tests/posix/pthread_cancel.c b/lib/mlibc/tests/posix/pthread_cancel.c
new file mode 100644
index 0000000..ca4ca34
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_cancel.c
@@ -0,0 +1,150 @@
+#include <assert.h>
+#include <pthread.h>
+#include <unistd.h>
+
+_Atomic int worker_ready = 0;
+_Atomic int main_ready = 0;
+
+static void *worker1(void *arg) {
+	(void)arg;
+	assert(!pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL));
+	assert(!pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, NULL));
+
+	worker_ready = 1;
+
+	while (1) sleep(1);
+
+	return NULL;
+}
+
+static void *worker2(void *arg) {
+	(void) arg;
+	assert(!pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL));
+
+	worker_ready = 1;
+
+	while(!main_ready);
+
+	// Cancellation point - we should cancel right now
+	sleep(1);
+
+	assert(!"Expected to be cancelled!");
+	__builtin_unreachable();
+}
+
+static void *worker3(void *arg) {
+	(void) arg;
+	assert(!pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL));
+
+	worker_ready = 1;
+
+	while(!main_ready);
+
+	// Cancellation point - we should cancel right now
+	pthread_testcancel();
+
+	assert(!"Expected to be cancelled!");
+	__builtin_unreachable();
+}
+
+static void *worker4(void *arg) {
+	(void) arg;
+	assert(!pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL));
+
+	worker_ready = 1;
+	sleep(1);
+
+	// We expect to be canceled during the sleep
+
+	assert(!"Expected to be cancelled!");
+	__builtin_unreachable();
+}
+
+static void *worker5(void *arg) {
+	assert(!pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL));
+
+	worker_ready = 1;
+
+	while(!main_ready);
+
+	// Cancellation point - we should NOT cancel right now
+	pthread_testcancel();
+
+	int *arg_int = (int*)arg;
+	*arg_int = 1;
+
+	return NULL;
+}
+
+static void check_result(pthread_t thread) {
+
+	void *ret_val = NULL;
+	int ret = pthread_join(thread, &ret_val);
+	assert(!ret);
+	assert(ret_val == PTHREAD_CANCELED);
+}
+
+int main() {
+	pthread_t thread;
+	int ret = pthread_create(&thread, NULL, &worker1, NULL);
+	assert(!ret);
+
+	while (!worker_ready);
+	ret = pthread_cancel(thread);
+	assert(!ret);
+	check_result(thread);
+
+	main_ready = 0;
+	worker_ready = 0;
+	main_ready = 0;
+	ret = pthread_create(&thread, NULL, &worker2, NULL);
+	assert(!ret);
+
+	while(!worker_ready);
+	ret = pthread_cancel(thread);
+	assert(!ret);
+	main_ready = 1;
+	check_result(thread);
+
+	main_ready = 0;
+	worker_ready = 0;
+	main_ready = 0;
+	ret = pthread_create(&thread, NULL, &worker3, NULL);
+	assert(!ret);
+
+	while(!worker_ready);
+	ret = pthread_cancel(thread);
+	assert(!ret);
+	main_ready = 1;
+	check_result(thread);
+
+	worker_ready = 0;
+	main_ready = 0;
+	ret = pthread_create(&thread, NULL, &worker4, NULL);
+	assert(!ret);
+
+	while(!worker_ready);
+	ret = pthread_cancel(thread);
+	assert(!ret);
+	main_ready = 1;
+	check_result(thread);
+
+	// Test for bug where pthread_testcancel() was not checking if
+	// cancellation was triggered properly.
+	worker_ready = 0;
+	int pthread_arg = 0;
+	main_ready = 0;
+	ret = pthread_create(&thread, NULL, &worker5, &pthread_arg);
+	assert(!ret);
+
+	while(!worker_ready);
+	main_ready = 1;
+
+	void *ret_val = NULL;
+	ret = pthread_join(thread, &ret_val);
+	assert(!ret);
+	assert(!ret_val);
+	assert(pthread_arg == 1);
+
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/pthread_cleanup.c b/lib/mlibc/tests/posix/pthread_cleanup.c
new file mode 100644
index 0000000..b6136aa
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_cleanup.c
@@ -0,0 +1,42 @@
+#include <stdint.h>
+#include <assert.h>
+#include <pthread.h>
+
+_Atomic uintptr_t cleanup_val = 0;
+
+static void cleanup(void *arg) {
+	cleanup_val = (uintptr_t)arg;
+}
+
+static void *worker(void *arg) {
+	(void)arg;
+
+	pthread_cleanup_push(cleanup, (void *)1);
+	pthread_cleanup_push(cleanup, (void *)2);
+	pthread_cleanup_push(cleanup, (void *)3);
+	pthread_cleanup_push(cleanup, (void *)4);
+
+	pthread_cleanup_pop(1);
+	assert(cleanup_val == 4);
+
+	pthread_cleanup_pop(0);
+	assert(cleanup_val == 4);
+
+	pthread_exit(NULL);
+
+	pthread_cleanup_pop(0);
+	pthread_cleanup_pop(0);
+
+	return NULL;
+}
+
+int main() {
+	pthread_t thread;
+	assert(!pthread_create(&thread, NULL, &worker, NULL));
+	assert(!pthread_join(thread, NULL));
+
+	assert(cleanup_val == 1);
+
+	return 0;
+}
+
diff --git a/lib/mlibc/tests/posix/pthread_cond.c b/lib/mlibc/tests/posix/pthread_cond.c
new file mode 100644
index 0000000..6203928
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_cond.c
@@ -0,0 +1,106 @@
+#include <assert.h>
+#include <errno.h>
+#include <pthread.h>
+#include <unistd.h>
+
+_Atomic int waiting, should_exit;
+pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
+pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
+
+static void *worker(void *arg) {
+	(void)arg;
+	pthread_mutex_lock(&mtx);
+	++waiting;
+	while (!should_exit)
+		pthread_cond_wait(&cond, &mtx);
+	pthread_mutex_unlock(&mtx);
+	return NULL;
+}
+
+static void test_broadcast_wakes_all() {
+	pthread_t t1, t2;
+	pthread_create(&t1, NULL, &worker, NULL);
+	pthread_create(&t2, NULL, &worker, NULL);
+
+	// Wait until the workers have actually entered the cond_wait
+	// before doing a broadcast.
+	while (waiting != 2 || pthread_mutex_trylock(&mtx) == EBUSY)
+		usleep(150000); // 150ms
+
+	should_exit = 1;
+	assert(!pthread_cond_broadcast(&cond));
+	pthread_mutex_unlock(&mtx);
+
+	pthread_join(t1, NULL);
+	pthread_join(t2, NULL);
+}
+
+static void test_timedwait_timedout() {
+	// Use CLOCK_MONOTONIC.
+	pthread_condattr_t attr;
+	pthread_condattr_init(&attr);
+	assert(!pthread_condattr_setclock(&attr, CLOCK_MONOTONIC));
+
+	struct timespec before_now;
+	assert(!clock_gettime(CLOCK_MONOTONIC, &before_now));
+	before_now.tv_nsec -= 10000;
+
+	pthread_mutex_lock(&mtx);
+	int e = pthread_cond_timedwait(&cond, &mtx, &before_now);
+	assert(e == ETIMEDOUT);
+	pthread_mutex_unlock(&mtx);
+
+	long nanos_per_second = 1000000000;
+	struct timespec after_now;
+	assert(!clock_gettime(CLOCK_MONOTONIC, &after_now));
+	after_now.tv_nsec += nanos_per_second / 10; // 100ms
+	if (after_now.tv_nsec >= nanos_per_second) {
+		after_now.tv_nsec -= nanos_per_second;
+		after_now.tv_sec++;
+	}
+
+	pthread_mutex_lock(&mtx);
+	e = pthread_cond_timedwait(&cond, &mtx, &after_now);
+	assert(e == ETIMEDOUT);
+	pthread_mutex_unlock(&mtx);
+
+	after_now.tv_nsec += nanos_per_second;
+	pthread_mutex_lock(&mtx);
+	e = pthread_cond_timedwait(&cond, &mtx, &after_now);
+	assert(e == EINVAL);
+	pthread_mutex_unlock(&mtx);
+}
+
+static void test_attr() {
+	pthread_condattr_t attr;
+	pthread_condattr_init(&attr);
+
+	clockid_t clock;
+	assert(!pthread_condattr_getclock(&attr, &clock));
+	assert(clock == CLOCK_REALTIME);
+	assert(!pthread_condattr_setclock(&attr, CLOCK_MONOTONIC));
+	assert(!pthread_condattr_getclock(&attr, &clock));
+	assert(clock == CLOCK_MONOTONIC);
+
+	int pshared;
+	assert(!pthread_condattr_getpshared(&attr, &pshared));
+	assert(pshared == PTHREAD_PROCESS_PRIVATE);
+	assert(!pthread_condattr_setpshared(&attr, PTHREAD_PROCESS_SHARED));
+	assert(!pthread_condattr_getpshared(&attr, &pshared));
+	assert(pshared == PTHREAD_PROCESS_SHARED);
+
+	pthread_condattr_destroy(&attr);
+	pthread_condattr_init(&attr);
+
+	// Make sure that we can create a pthread_cond_t with an attr.
+	pthread_cond_t cond;
+	pthread_cond_init(&cond, &attr);
+	pthread_cond_destroy(&cond);
+	pthread_condattr_destroy(&attr);
+}
+
+int main() {
+	test_attr();
+	test_broadcast_wakes_all();
+	test_timedwait_timedout();
+}
diff --git a/lib/mlibc/tests/posix/pthread_create.c b/lib/mlibc/tests/posix/pthread_create.c
new file mode 100644
index 0000000..b78674f
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_create.c
@@ -0,0 +1,22 @@
+#include <assert.h>
+#include <time.h>
+#include <pthread.h>
+
+int variable = 0;
+
+static void *worker(void *arg) {
+	(void) arg;
+	variable = 1;
+	return NULL;
+}
+
+int main() {
+	pthread_t thread;
+	int ret = pthread_create(&thread, NULL, &worker, NULL);
+	assert(!ret);
+
+	ret = pthread_join(thread, NULL);
+	assert(!ret);
+	assert(variable == 1);
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/pthread_key.c b/lib/mlibc/tests/posix/pthread_key.c
new file mode 100644
index 0000000..40bd882
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_key.c
@@ -0,0 +1,95 @@
+#include <assert.h>
+#include <pthread.h>
+#include <errno.h>
+#include <limits.h>
+
+_Atomic int dtors_entered = 0;
+pthread_key_t key3;
+
+static void dtor1(void *arg) {
+	(void)arg;
+	dtors_entered++;
+
+	// Set the key during destruction to trigger dtor2 (as it only runs if
+	// the key value is non-NULL).
+	assert(!pthread_setspecific(key3, &key3));
+	assert(pthread_getspecific(key3) == &key3);
+}
+
+static void dtor2(void *arg) {
+	(void)arg;
+	dtors_entered++;
+}
+
+static void *worker1(void *arg) {
+	(void)arg;
+
+	pthread_key_t key1, key2;
+	assert(!pthread_key_create(&key1, NULL));
+	assert(!pthread_key_create(&key2, dtor1));
+	assert(!pthread_key_create(&key3, dtor2));
+
+	assert(!pthread_setspecific(key1, &key1));
+	assert(pthread_getspecific(key1) == &key1);
+
+	assert(!pthread_setspecific(key2, &key2));
+	assert(pthread_getspecific(key2) == &key2);
+
+	pthread_exit(0);
+	return NULL;
+}
+
+static void dtor3(void *arg) {
+	(void)arg;
+
+	// Make sure that we can create and destroy keys inside the dtor.
+	pthread_key_t dtorKey;
+	assert(!pthread_key_create(&dtorKey, NULL));
+
+	assert(!pthread_setspecific(dtorKey, &dtorKey));
+	assert(pthread_getspecific(dtorKey) == &dtorKey);
+
+	assert(!pthread_key_delete(dtorKey));
+}
+
+static void *worker2(void *arg) {
+	(void)arg;
+
+	pthread_key_t key;
+	assert(!pthread_key_create(&key, dtor3));
+
+	assert(!pthread_setspecific(key, &key));
+	assert(pthread_getspecific(key) == &key);
+
+	pthread_exit(0);
+	return NULL;
+}
+
+int main() {
+	// NOTE that the EINVAL return from pthread_setspecific is mlibc-specific,
+	// POSIX specifies that accessing an invalid key is undefined behavior.
+
+	assert(pthread_getspecific(PTHREAD_KEYS_MAX) == NULL);
+	assert(pthread_setspecific(PTHREAD_KEYS_MAX, NULL) == EINVAL);
+
+	pthread_key_t key;
+	assert(!pthread_key_create(&key, NULL));
+	assert(!pthread_setspecific(key, &key));
+	assert(pthread_getspecific(key) == &key);
+	assert(!pthread_key_delete(key));
+
+	pthread_t thread;
+	assert(!pthread_create(&thread, NULL, &worker1, NULL));
+	assert(!pthread_join(thread, NULL));
+
+	assert(pthread_getspecific(key) == NULL);
+	assert(!pthread_setspecific(key, &key));
+	assert(pthread_getspecific(key) == &key);
+
+	assert(dtors_entered == 2);
+
+	assert(!pthread_create(&thread, NULL, &worker2, NULL));
+	assert(!pthread_join(thread, NULL));
+
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/pthread_kill.c b/lib/mlibc/tests/posix/pthread_kill.c
new file mode 100644
index 0000000..b740b70
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_kill.c
@@ -0,0 +1,46 @@
+#include <assert.h>
+#include <pthread.h>
+#include <signal.h>
+
+_Atomic int handler_ready = 0;
+_Atomic int thread_signal_ran = 0;
+
+static void sig_handler(int sig, siginfo_t *info, void *ctx) {
+	(void)sig;
+	(void)info;
+	(void)ctx;
+
+	thread_signal_ran = 1;
+}
+
+static void *worker(void *arg) {
+	(void)arg;
+
+	struct sigaction sa;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_sigaction = sig_handler;
+	sa.sa_flags = SA_SIGINFO;
+	assert(!sigaction(SIGUSR1, &sa, NULL));
+
+	handler_ready = 1;
+
+	while (!thread_signal_ran)
+		;
+
+	return NULL;
+}
+
+int main() {
+	pthread_t thread;
+	assert(!pthread_create(&thread, NULL, &worker, NULL));
+
+	while (!handler_ready)
+		;
+
+	assert(!pthread_kill(thread, SIGUSR1));
+	assert(!pthread_join(thread, NULL));
+
+	assert(thread_signal_ran);
+
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/pthread_mutex.c b/lib/mlibc/tests/posix/pthread_mutex.c
new file mode 100644
index 0000000..0a9b82f
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_mutex.c
@@ -0,0 +1,101 @@
+#include <pthread.h>
+#include <assert.h>
+#include <errno.h>
+
+#define TEST_ATTR(attr, field, value) ({ \
+		int x; \
+		assert(!pthread_mutexattr_set ## field (&(attr), (value))); \
+		assert(!pthread_mutexattr_get ## field (&(attr), &x)); \
+		assert(x == (value)); \
+	})
+
+int variable;
+pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+
+static void *worker(void *arg) {
+	(void)arg;
+	pthread_mutex_lock(&mutex);
+	variable = 1;
+	pthread_mutex_unlock(&mutex);
+	return NULL;
+}
+
+static void testAttr() {
+	pthread_mutexattr_t attr;
+	pthread_mutexattr_init(&attr);
+
+	TEST_ATTR(attr, type, PTHREAD_MUTEX_DEFAULT);
+	TEST_ATTR(attr, type, PTHREAD_MUTEX_NORMAL);
+	TEST_ATTR(attr, type, PTHREAD_MUTEX_ERRORCHECK);
+	TEST_ATTR(attr, type, PTHREAD_MUTEX_RECURSIVE);
+
+	TEST_ATTR(attr, robust, PTHREAD_MUTEX_STALLED);
+	TEST_ATTR(attr, robust, PTHREAD_MUTEX_ROBUST);
+
+	TEST_ATTR(attr, protocol, PTHREAD_PRIO_NONE);
+	TEST_ATTR(attr, protocol, PTHREAD_PRIO_INHERIT);
+	TEST_ATTR(attr, protocol, PTHREAD_PRIO_PROTECT);
+
+	TEST_ATTR(attr, pshared, PTHREAD_PROCESS_PRIVATE);
+	TEST_ATTR(attr, pshared, PTHREAD_PROCESS_SHARED);
+
+	// TODO: sched_get_priority* is unimplemented.
+	// int prio = sched_get_priority_max(SCHED_FIFO);
+	// TEST_ATTR(attr, prioceiling, prio);
+
+	pthread_mutexattr_destroy(&attr);
+}
+
+static void testNormal() {
+	pthread_mutexattr_t attr;
+	pthread_mutexattr_init(&attr);
+	pthread_mutex_init(&mutex, &attr);
+	pthread_mutexattr_destroy(&attr);
+
+	pthread_mutex_lock(&mutex);
+	variable = 0;
+
+	pthread_t thread;
+	int ret = pthread_create(&thread, NULL, &worker, NULL);
+	assert(!ret);
+
+	assert(pthread_mutex_trylock(&mutex) == EBUSY);
+	pthread_mutex_unlock(&mutex);
+
+	ret = pthread_join(thread, NULL);
+	assert(!ret);
+	assert(variable == 1);
+
+	pthread_mutex_destroy(&mutex);
+}
+
+static void testRecursive() {
+	pthread_mutexattr_t attr;
+	pthread_mutexattr_init(&attr);
+	pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
+	pthread_mutex_init(&mutex, &attr);
+	pthread_mutexattr_destroy(&attr);
+
+	pthread_mutex_lock(&mutex);
+	variable = 0;
+
+	pthread_t thread;
+	int ret = pthread_create(&thread, NULL, &worker, NULL);
+	assert(!ret);
+
+	assert(pthread_mutex_trylock(&mutex) == 0);
+	pthread_mutex_unlock(&mutex);
+	pthread_mutex_unlock(&mutex);
+
+	ret = pthread_join(thread, NULL);
+	assert(!ret);
+	assert(variable == 1);
+
+	pthread_mutex_destroy(&mutex);
+}
+
+int main() {
+	testAttr();
+	testNormal();
+	testRecursive();
+}
diff --git a/lib/mlibc/tests/posix/pthread_rwlock.c b/lib/mlibc/tests/posix/pthread_rwlock.c
new file mode 100644
index 0000000..5316372
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_rwlock.c
@@ -0,0 +1,114 @@
+#include <assert.h>
+#include <errno.h>
+#include <pthread.h>
+
+static void test_write_lock_unlock() {
+	int res;
+	pthread_rwlock_t rw = PTHREAD_RWLOCK_INITIALIZER;
+	res = pthread_rwlock_wrlock(&rw);
+	assert(!res);
+	res = pthread_rwlock_unlock(&rw);
+	assert(!res);
+}
+
+static void test_read_lock_unlock() {
+	int res;
+	pthread_rwlock_t rw = PTHREAD_RWLOCK_INITIALIZER;
+	res = pthread_rwlock_rdlock(&rw);
+	assert(!res);
+	res = pthread_rwlock_unlock(&rw);
+	assert(!res);
+}
+
+static void test_write_trylock_unlock() {
+	int res;
+	pthread_rwlock_t rw = PTHREAD_RWLOCK_INITIALIZER;
+	res = pthread_rwlock_trywrlock(&rw);
+	assert(!res);
+	res = pthread_rwlock_unlock(&rw);
+	assert(!res);
+}
+
+static void test_read_trylock_unlock() {
+	int res;
+	pthread_rwlock_t rw = PTHREAD_RWLOCK_INITIALIZER;
+	res = pthread_rwlock_tryrdlock(&rw);
+	assert(!res);
+	res = pthread_rwlock_unlock(&rw);
+	assert(!res);
+}
+
+static void test_write_prevents_read() {
+	int res;
+	pthread_rwlock_t rw = PTHREAD_RWLOCK_INITIALIZER;
+	res = pthread_rwlock_wrlock(&rw);
+	assert(!res);
+	res = pthread_rwlock_tryrdlock(&rw);
+	assert(res == EBUSY);
+	res = pthread_rwlock_unlock(&rw);
+	assert(!res);
+}
+
+static void test_write_prevents_write() {
+	int res;
+	pthread_rwlock_t rw = PTHREAD_RWLOCK_INITIALIZER;
+	res = pthread_rwlock_wrlock(&rw);
+	assert(!res);
+	res = pthread_rwlock_trywrlock(&rw);
+	assert(res == EBUSY);
+	res = pthread_rwlock_unlock(&rw);
+	assert(!res);
+}
+
+static void test_read_prevents_write() {
+	int res;
+	pthread_rwlock_t rw = PTHREAD_RWLOCK_INITIALIZER;
+	res = pthread_rwlock_rdlock(&rw);
+	assert(!res);
+	res = pthread_rwlock_trywrlock(&rw);
+	assert(res == EBUSY);
+	res = pthread_rwlock_unlock(&rw);
+	assert(!res);
+}
+
+static void test_read_allows_read() {
+	int res;
+	pthread_rwlock_t rw = PTHREAD_RWLOCK_INITIALIZER;
+	res = pthread_rwlock_rdlock(&rw);
+	assert(!res);
+	res = pthread_rwlock_tryrdlock(&rw);
+	assert(!res);
+	res = pthread_rwlock_unlock(&rw);
+	assert(!res);
+}
+
+static void test_attr() {
+	pthread_rwlockattr_t attr;
+	pthread_rwlockattr_init(&attr);
+
+	int pshared;
+	pthread_rwlockattr_getpshared(&attr, &pshared);
+	assert(pshared == PTHREAD_PROCESS_PRIVATE);
+
+	pthread_rwlockattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
+	pthread_rwlockattr_getpshared(&attr, &pshared);
+	assert(pshared == PTHREAD_PROCESS_SHARED);
+
+	pthread_rwlockattr_setpshared(&attr, PTHREAD_PROCESS_PRIVATE);
+	pthread_rwlockattr_getpshared(&attr, &pshared);
+	assert(pshared == PTHREAD_PROCESS_PRIVATE);
+
+	pthread_rwlockattr_destroy(&attr);
+}
+
+int main() {
+	test_write_lock_unlock();
+	test_read_lock_unlock();
+	test_write_trylock_unlock();
+	test_read_trylock_unlock();
+	test_write_prevents_read();
+	test_write_prevents_write();
+	test_read_prevents_write();
+	test_read_allows_read();
+	test_attr();
+}
diff --git a/lib/mlibc/tests/posix/pthread_schedparam.c b/lib/mlibc/tests/posix/pthread_schedparam.c
new file mode 100644
index 0000000..dde70fb
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_schedparam.c
@@ -0,0 +1,32 @@
+#include <assert.h>
+#include <errno.h>
+#include <pthread.h>
+#include <stdlib.h>
+
+int main() {
+	struct sched_param param = {
+		.sched_priority = 100,
+	};
+
+	int policy = 0xDEADBEEF;
+
+	int ret = pthread_getschedparam(pthread_self(), &policy, &param);
+	assert(policy == SCHED_OTHER);
+	assert(!ret);
+
+	param.sched_priority = 10;
+
+	ret = pthread_setschedparam(pthread_self(), SCHED_FIFO, &param);
+	assert(!ret || ret == EPERM);
+
+	if(ret == EPERM) {
+		exit(0);
+	}
+
+	param.sched_priority = 0xDEADBEEF;
+
+	ret = pthread_getschedparam(pthread_self(), &policy, &param);
+	assert(policy == SCHED_FIFO);
+	assert(param.sched_priority == 10);
+	assert(!ret);
+}
diff --git a/lib/mlibc/tests/posix/pthread_thread_local.c b/lib/mlibc/tests/posix/pthread_thread_local.c
new file mode 100644
index 0000000..90c6f72
--- /dev/null
+++ b/lib/mlibc/tests/posix/pthread_thread_local.c
@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <pthread.h>
+#include <assert.h>
+ 
+_Thread_local unsigned int counter = 9999; 
+_Thread_local unsigned int uninitialized;
+ 
+void *check_counter(void *arg)
+{
+	(void)arg;
+	fprintf(stderr, "counter for worker thread: %d, at %p\n", counter, &counter);
+	fflush(stderr);
+	assert(counter == 9999);
+
+	fprintf(stderr, "uninitialized data for worker thread: %d, at %p\n", uninitialized, &uninitialized);
+	fflush(stderr);
+	assert(uninitialized == 0);
+
+	++counter;
+	++uninitialized;
+	fprintf(stderr, "counter for worker thread: %d\n", counter);
+	fflush(stderr);
+	assert(counter == 10000);
+	assert(uninitialized == 1);
+	return NULL;
+}
+ 
+int main()
+{
+	fprintf(stderr, "counter for main thread: %d, at %p\n", counter, &counter);
+	fflush(stderr);
+	assert(counter == 9999);
+
+	fprintf(stderr, "uninitialized data for main thread: %d, at %p\n", uninitialized, &uninitialized);
+	fflush(stderr);
+	assert(uninitialized == 0);
+
+	++counter;
+	++uninitialized;
+	fprintf(stderr, "counter for main: %d\n", counter);
+	fflush(stderr);
+	assert(counter == 10000);
+	assert(uninitialized == 1);
+
+	pthread_t thd;
+	pthread_create(&thd, NULL, check_counter, NULL);
+	pthread_join(thd, NULL);
+
+	fprintf(stderr, "counter for main: %d\n", counter);
+	fflush(stderr);
+	assert(counter == 10000);
+	assert(uninitialized == 1);
+}
diff --git a/lib/mlibc/tests/posix/pwd.c b/lib/mlibc/tests/posix/pwd.c
new file mode 100644
index 0000000..a9ebd8e
--- /dev/null
+++ b/lib/mlibc/tests/posix/pwd.c
@@ -0,0 +1,88 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <pwd.h>
+#include <unistd.h>
+#include <assert.h>
+#include <string.h>
+#include <errno.h>
+
+int main()
+{
+	struct passwd pwd, *result = NULL;
+	char *buf;
+	size_t bufsize;
+	int s;
+
+	bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
+	assert(bufsize > 0 && bufsize < 0x100000);
+
+	buf = malloc(bufsize);
+	assert(buf);
+
+	s = getpwnam_r("root", &pwd, buf, bufsize, &result);
+	assert(!s);
+	assert(pwd.pw_uid == 0);
+	assert(!strcmp(pwd.pw_name, "root"));
+	assert(strlen(pwd.pw_passwd) <= 1000);
+
+	s = getpwuid_r(0, &pwd, buf, bufsize, &result);
+	assert(!s);
+	assert(pwd.pw_uid == 0);
+	assert(!strcmp(pwd.pw_name, "root"));
+	assert(strlen(pwd.pw_passwd) <= 1000);
+
+	result = getpwnam("root");
+	assert(result);
+	assert(result->pw_uid == 0);
+	assert(!strcmp(result->pw_name, "root"));
+	assert(strlen(result->pw_passwd) <= 1000);
+
+	result = getpwuid(0);
+	assert(result);
+	assert(result->pw_uid == 0);
+	assert(!strcmp(result->pw_name, "root"));
+	assert(strlen(result->pw_passwd) <= 1000);
+
+	errno = 0;
+	setpwent();
+	assert(errno == 0);
+
+	errno = 0;
+	result = getpwent();
+	assert(result);
+
+	pwd = *result;
+	pwd.pw_name = strdup(result->pw_name);
+	pwd.pw_passwd = strdup(result->pw_passwd);
+	pwd.pw_gecos = strdup(result->pw_gecos);
+	pwd.pw_dir = strdup(result->pw_dir);
+	pwd.pw_shell = strdup(result->pw_shell);
+	assert(pwd.pw_name);
+	assert(pwd.pw_passwd);
+	assert(pwd.pw_gecos);
+	assert(pwd.pw_dir);
+	assert(pwd.pw_shell);
+
+	errno = 0;
+	setpwent();
+	assert(errno == 0);
+
+	errno = 0;
+	result = getpwent();
+	assert(result);
+
+	assert(!strcmp(pwd.pw_name, result->pw_name));
+	assert(!strcmp(pwd.pw_passwd, result->pw_passwd));
+	assert(!strcmp(pwd.pw_gecos, result->pw_gecos));
+	assert(!strcmp(pwd.pw_dir, result->pw_dir));
+	assert(!strcmp(pwd.pw_shell, result->pw_shell));
+	assert(pwd.pw_uid == result->pw_uid);
+	assert(pwd.pw_gid == result->pw_gid);
+
+	free(buf);
+	free(pwd.pw_name);
+	free(pwd.pw_passwd);
+	free(pwd.pw_gecos);
+	free(pwd.pw_dir);
+	free(pwd.pw_shell);
+}
diff --git a/lib/mlibc/tests/posix/readv-writev.c b/lib/mlibc/tests/posix/readv-writev.c
new file mode 100644
index 0000000..5025ce2
--- /dev/null
+++ b/lib/mlibc/tests/posix/readv-writev.c
@@ -0,0 +1,51 @@
+#include <assert.h>
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/uio.h>
+
+#ifdef USE_HOST_LIBC
+#define TEST_FILE "readv-writev-host-libc.tmp"
+#else
+#define TEST_FILE "readv-writev.tmp"
+#endif
+
+int main() {
+	// Make sure that it wasn't created by a previous test run
+	unlink(TEST_FILE);
+
+	int fd = open(TEST_FILE, O_RDWR | O_CREAT, 0644);
+	assert(fd != -1);
+
+	char str0[] = "hello ";
+	char str1[] = "world!";
+
+	struct iovec bufs[2] = {
+		{
+			.iov_base = &str0,
+			.iov_len = strlen(str0),
+		},
+		{
+			.iov_base = &str1,
+			.iov_len = strlen(str1),
+		},
+	};
+
+	ssize_t written = writev(fd, bufs, 2);
+	assert(written == 12);
+
+	memset(&str0, 0, strlen(str0));
+	memset(&str1, 0, strlen(str1));
+
+	assert(!lseek(fd, 0, SEEK_SET));
+
+	ssize_t read = readv(fd, bufs, 2);
+	assert(read == 12);
+
+	assert(!strncmp(str0, "hello ", 7));
+	assert(!strncmp(str1, "world!", 7));
+
+	assert(!close(fd));
+
+	unlink(TEST_FILE);
+}
diff --git a/lib/mlibc/tests/posix/realpath.c b/lib/mlibc/tests/posix/realpath.c
new file mode 100644
index 0000000..e44de81
--- /dev/null
+++ b/lib/mlibc/tests/posix/realpath.c
@@ -0,0 +1,133 @@
+#include <unistd.h>
+#include <sys/stat.h>
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <signal.h>
+
+#ifdef USE_HOST_LIBC
+#define TEST_BASE "/tmp/mlibc-realpath-host-libc"
+#else
+#define TEST_BASE "/tmp/mlibc-realpath"
+#endif
+
+void prepare() {
+	assert(!mkdir(TEST_BASE "/", S_IRWXU));
+	assert(!mkdir(TEST_BASE "/dir1", S_IRWXU));
+	assert(!mkdir(TEST_BASE "/dir2", S_IRWXU));
+	assert(!symlink(TEST_BASE "/dir2/", TEST_BASE "/dir1/abs-link"));
+	assert(!chdir(TEST_BASE "/dir1"));
+	assert(!symlink("../dir2/", TEST_BASE "/dir1/rel-link"));
+}
+
+void cleanup(int do_assert) {
+	if (do_assert) {
+		assert(!unlink(TEST_BASE "/dir1/rel-link"));
+		assert(!unlink(TEST_BASE "/dir1/abs-link"));
+		assert(!rmdir(TEST_BASE "/dir2"));
+		assert(!rmdir(TEST_BASE "/dir1"));
+		assert(!rmdir(TEST_BASE "/"));
+	} else {
+		unlink(TEST_BASE "/dir1/rel-link");
+		unlink(TEST_BASE "/dir1/abs-link");
+		rmdir(TEST_BASE "/dir2");
+		rmdir(TEST_BASE "/dir1");
+		rmdir(TEST_BASE "/");
+	}
+}
+
+void signal_handler(int sig, siginfo_t *info, void *ctx) {
+	(void)sig;
+	(void)info;
+	(void)ctx;
+
+	cleanup(0);
+
+	struct sigaction sa;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_handler = SIG_DFL;
+	sa.sa_flags = 0;
+
+	sigaction(SIGABRT, &sa, NULL);
+	abort();
+}
+
+int main() {
+	char *path;
+
+	struct sigaction sa;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_sigaction = signal_handler;
+	sa.sa_flags = SA_SIGINFO;
+	sigaction(SIGABRT, &sa, NULL);
+
+	prepare();
+
+	path = realpath(TEST_BASE "/dir1/", NULL);
+	assert(path);
+	assert(!strcmp(path, TEST_BASE "/dir1"));
+	free(path);
+
+	path = realpath(TEST_BASE "/dir1/../dir2", NULL);
+	assert(path);
+	assert(!strcmp(path, TEST_BASE "/dir2"));
+	free(path);
+
+	path = realpath(TEST_BASE "/dir1/abs-link/", NULL);
+	assert(path);
+	assert(!strcmp(path, TEST_BASE "/dir2"));
+	free(path);
+
+	path = realpath(TEST_BASE "/dir1/rel-link/", NULL);
+	assert(path);
+	assert(!strcmp(path, TEST_BASE "/dir2"));
+	free(path);
+
+	path = realpath(TEST_BASE "/dir1/abs-link/../", NULL);
+	assert(path);
+	assert(!strcmp(path, TEST_BASE ""));
+	free(path);
+
+	path = realpath(TEST_BASE "/dir1/rel-link/../", NULL);
+	assert(path);
+	assert(!strcmp(path, TEST_BASE ""));
+	free(path);
+
+	path = realpath(TEST_BASE "/dir1/abs-link/../dir1/abs-link/", NULL);
+	assert(path);
+	assert(!strcmp(path, TEST_BASE "/dir2"));
+	free(path);
+
+	path = realpath(TEST_BASE "/dir1/rel-link/../dir1/rel-link/", NULL);
+	assert(path);
+	assert(!strcmp(path, TEST_BASE "/dir2"));
+	free(path);
+
+	path = realpath(TEST_BASE "/dir1/abs-link/../dir1/rel-link/", NULL);
+	assert(path);
+	assert(!strcmp(path, TEST_BASE "/dir2"));
+	free(path);
+
+	path = realpath(TEST_BASE "/dir1/rel-link/../dir1/abs-link/", NULL);
+	assert(path);
+	assert(!strcmp(path, TEST_BASE "/dir2"));
+	free(path);
+
+	path = realpath("/tmp", NULL);
+	assert(path);
+	assert(!strcmp(path, "/tmp"));
+	free(path);
+
+	path = realpath("/", NULL);
+	assert(path);
+	assert(!strcmp(path, "/"));
+	free(path);
+
+	path = realpath("//", NULL);
+	assert(path);
+	assert(!strcmp(path, "/"));
+	free(path);
+
+	cleanup(1);
+}
diff --git a/lib/mlibc/tests/posix/regex.c b/lib/mlibc/tests/posix/regex.c
new file mode 100644
index 0000000..6c2ca3f
--- /dev/null
+++ b/lib/mlibc/tests/posix/regex.c
@@ -0,0 +1,30 @@
+#include <regex.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+ 
+int main(void) {
+	char *testString = "mlibc is the best best best libc";
+	char *pattern = "\\(be[a-z]t\\) \\1";
+
+	regex_t reg;
+	int rc = regcomp(&reg, pattern, 0);
+	assert(!rc);
+
+	regmatch_t matches[2];
+	rc = regexec(&reg, testString, 2, matches, 0);
+	assert(!rc);
+
+	printf("Whole pattern: \"%.*s\" at %zd-%zd.\n",
+		(int)(matches[0].rm_eo - matches[0].rm_so), &testString[matches[0].rm_so],
+		(ssize_t)matches[0].rm_so, (ssize_t)(matches[0].rm_eo - 1));
+	assert(matches[0].rm_so == 13 && matches[0].rm_eo == 22);
+
+	printf("Substring: \"%.*s\" at %zd-%zd.\n",
+		(int)(matches[1].rm_eo - matches[1].rm_so), &testString[matches[1].rm_so],
+		(ssize_t)matches[1].rm_so, (ssize_t)matches[1].rm_eo - 1);
+	assert(matches[1].rm_so == 13 && matches[1].rm_eo == 17);
+
+	regfree(&reg);
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/rindex.c b/lib/mlibc/tests/posix/rindex.c
new file mode 100644
index 0000000..0eb2f54
--- /dev/null
+++ b/lib/mlibc/tests/posix/rindex.c
@@ -0,0 +1,11 @@
+#include <strings.h>
+#include <assert.h>
+
+int main() {
+  char str[] = "This is a sample string";
+  char *pch;
+  pch = rindex(str, 's');
+  // The last occurence of 's' is at position 18
+  assert(pch - str + 1 == 18);
+  return 0;
+}
diff --git a/lib/mlibc/tests/posix/rlimits.c b/lib/mlibc/tests/posix/rlimits.c
new file mode 100644
index 0000000..3565521
--- /dev/null
+++ b/lib/mlibc/tests/posix/rlimits.c
@@ -0,0 +1,26 @@
+#include <sys/resource.h>
+#include <stdio.h>
+#include <errno.h>
+#include <assert.h>
+#include <string.h>
+
+int main() {
+	struct rlimit getlim, setlim;
+
+    setlim.rlim_cur = 16;
+    setlim.rlim_max = 4096;
+
+	int ret = setrlimit(RLIMIT_NOFILE, &setlim);
+
+    if(ret == -1) {
+        fprintf(stderr, "%s\n", strerror(errno));
+		assert(!ret);
+	}
+
+    assert(!getrlimit(RLIMIT_NOFILE, &getlim));
+
+	assert(setlim.rlim_cur == getlim.rlim_cur);
+	assert(setlim.rlim_max == getlim.rlim_max);
+
+    return 0;
+}
diff --git a/lib/mlibc/tests/posix/search.c b/lib/mlibc/tests/posix/search.c
new file mode 100644
index 0000000..6b68ef9
--- /dev/null
+++ b/lib/mlibc/tests/posix/search.c
@@ -0,0 +1,51 @@
+#include <search.h>
+#include <assert.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+static int compare(const void *pa, const void *pb) {
+	if (*(int*)pa < *(int*) pb)
+		return -1;
+	if (*(int*)pa > *(int*) pb)
+		return 1;
+	return 0;
+}
+
+static void check_key(int key, void *root) {
+	int keyp = key;
+	void *ret = tfind((void*) &keyp, &root, compare);
+	assert(ret);
+	assert(**((int **) ret) == key);
+}
+
+static void free_key(void *key) {
+	free(key);
+}
+
+int main() {
+	void *root = NULL;
+	for (int i = 0; i < 12; i++) {
+		int *ptr = malloc(sizeof(int));
+		assert(ptr);
+		*ptr = i;
+
+		void *ret = tsearch((void*) ptr, &root, compare);
+		assert(ret);
+		assert(**((int **) ret) == i);
+	}
+
+	// Test a couple of keys
+	check_key(1, root);
+	check_key(5, root);
+	check_key(10, root);
+
+	// Verify NULL on non-existent key
+	int key = -1;
+	void *ret = tfind((void*) &key, &root, compare);
+	assert(ret == NULL);
+
+	// tdelete is not implemented yet (#351)
+	(void)free_key;
+	// tdestroy(root, free_key);
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/setpriority.c b/lib/mlibc/tests/posix/setpriority.c
new file mode 100644
index 0000000..11cb7ed
--- /dev/null
+++ b/lib/mlibc/tests/posix/setpriority.c
@@ -0,0 +1,27 @@
+#include <assert.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/resource.h>
+#include <unistd.h>
+
+int main() {
+	errno = 0;
+	int original_priority = getpriority(PRIO_PROCESS, getpid());
+
+	assert(original_priority != -1 || !errno);
+
+	int ret = setpriority(PRIO_PROCESS, getpid(), original_priority + 1);
+
+	if(ret) {
+		fprintf(stderr, "%s", strerror(errno));
+		exit(1);
+	}
+
+	errno = 0;
+	int new_priority = getpriority(PRIO_PROCESS, getpid());
+
+	assert(new_priority != -1 || !errno);
+	assert(new_priority == original_priority + 1);
+}
diff --git a/lib/mlibc/tests/posix/sigaltstack.c b/lib/mlibc/tests/posix/sigaltstack.c
new file mode 100644
index 0000000..bebcc30
--- /dev/null
+++ b/lib/mlibc/tests/posix/sigaltstack.c
@@ -0,0 +1,55 @@
+#include <assert.h>
+#include <setjmp.h>
+#include <signal.h>
+#include <stdlib.h>
+
+static jmp_buf env;
+static char *sigStack;
+
+static void sig_handler(int sig, siginfo_t *info, void *ctx) {
+	(void)sig;
+	(void)info;
+	(void)ctx;
+
+	longjmp(env, 1);
+}
+
+int main() {
+	if (setjmp(env)) {
+		free(sigStack);
+		return 0;
+	}
+
+	sigStack = malloc(SIGSTKSZ);
+
+	stack_t ss;
+	ss.ss_sp = sigStack;
+	ss.ss_size = SIGSTKSZ;
+	ss.ss_flags = 0;
+
+	assert(!sigaltstack(&ss, NULL));
+
+	struct sigaction sa;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = SA_SIGINFO | SA_ONSTACK;
+	sa.sa_sigaction = sig_handler;
+
+	assert(!sigaction(SIGSEGV, &sa, NULL));
+
+	// This is used to trash the stack to ensure sigaltstack actually switched stacks.
+#if defined(__x86_64__)
+	asm volatile ("mov $0, %rsp\n"
+			"\t" "push $0");
+#elif defined(__i386__)
+	asm volatile ("mov $0, %esp\n"
+			"\t" "push $0");
+#elif defined(__aarch64__)
+	asm volatile ("mov sp, %0\n"
+			"\t" "stp x0, x1, [sp, #-16]!" :: "r"((uint64_t)0));
+#elif defined(__riscv) && __riscv_xlen == 64
+	asm volatile ("li sp, 0\n"
+			"\t" "sd zero, 0(sp)");
+#else
+#	error Unknown architecture
+#endif
+}
diff --git a/lib/mlibc/tests/posix/sigsuspend.c b/lib/mlibc/tests/posix/sigsuspend.c
new file mode 100644
index 0000000..09b9a1e
--- /dev/null
+++ b/lib/mlibc/tests/posix/sigsuspend.c
@@ -0,0 +1,53 @@
+#include <assert.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <signal.h>
+#include <errno.h>
+
+_Atomic int handler_ready = 0;
+_Atomic int thread_signal_ran = 0;
+
+static void sig_handler(int sig, siginfo_t *info, void *ctx) {
+	(void)sig;
+	(void)info;
+	(void)ctx;
+
+	thread_signal_ran = 1;
+}
+
+static void *worker(void *arg) {
+	(void)arg;
+
+	struct sigaction sa;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_sigaction = sig_handler;
+	sa.sa_flags = SA_SIGINFO;
+	assert(!sigaction(SIGUSR1, &sa, NULL));
+
+	handler_ready = 1;
+
+	sigset_t set;
+	sigfillset(&set);
+	sigdelset(&set, SIGUSR1);
+
+	assert(sigsuspend(&set));
+	assert(thread_signal_ran);
+	assert(errno == EINTR);
+
+	return NULL;
+}
+
+int main() {
+	pthread_t thread;
+	assert(!pthread_create(&thread, NULL, &worker, NULL));
+
+	while (!handler_ready)
+		;
+
+	sleep(1);
+
+	assert(!pthread_kill(thread, SIGUSR1));
+	assert(!pthread_join(thread, NULL));
+
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/sigtimedwait.c b/lib/mlibc/tests/posix/sigtimedwait.c
new file mode 100644
index 0000000..4793fc1
--- /dev/null
+++ b/lib/mlibc/tests/posix/sigtimedwait.c
@@ -0,0 +1,91 @@
+#include <stdio.h>
+
+#include <assert.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/wait.h>
+#include <errno.h>
+
+pid_t parent;
+pid_t child;
+
+int fds[2];
+
+void parent_fn() {
+	int res;
+
+	sigset_t set;
+	sigemptyset(&set);
+	sigaddset(&set, SIGUSR2);
+	sigprocmask(SIG_BLOCK, &set, NULL);
+
+	res = write(fds[1], "!", 1);
+	assert(res == 1);
+
+	siginfo_t info;
+	res = sigwaitinfo(&set, &info);
+	assert(res == SIGUSR2);
+	assert(info.si_signo == SIGUSR2);
+
+	res = write(fds[1], "!", 1);
+	assert(res == 1);
+
+	// XXX: This may not be long enough to get scheduled
+	struct timespec tout = {1, 0};
+	res = sigtimedwait(&set, &info, &tout);
+	assert(res == SIGUSR2);
+	assert(info.si_signo == SIGUSR2);
+
+	res = write(fds[1], "!", 1);
+	assert(res == 1);
+
+	int sig;
+	res = sigwait(&set, &sig);
+	assert(res == 0);
+	assert(sig == SIGUSR2);
+
+	res = write(fds[1], "!", 1);
+	assert(res == 1);
+
+	res = sigtimedwait(&set, &info, &tout);
+	assert(res < 0);
+	assert(errno == EAGAIN);
+
+	int wsts;
+	res = waitpid(child, &wsts, 0);
+	assert(res >= 0);
+}
+
+void child_fn() {
+	int res;
+	char c;
+
+	res = read(fds[0], &c, 1);
+	assert(res == 1);
+	kill(parent, SIGUSR2);
+	res = read(fds[0], &c, 1);
+	assert(res == 1);
+	kill(parent, SIGUSR2);
+	res = read(fds[0], &c, 1);
+	assert(res == 1);
+	kill(parent, SIGUSR2);
+	res = read(fds[0], &c, 1);
+	assert(res == 1);
+}
+
+int main() {
+	int res;
+
+	parent = getpid();
+	assert(parent > 0);
+
+	res = pipe(fds);
+	assert(res == 0);
+
+	child = fork();
+	assert(child >= 0);
+	if (child)
+		parent_fn();
+	else
+		child_fn();
+}
diff --git a/lib/mlibc/tests/posix/strdupa.c b/lib/mlibc/tests/posix/strdupa.c
new file mode 100644
index 0000000..c79de8e
--- /dev/null
+++ b/lib/mlibc/tests/posix/strdupa.c
@@ -0,0 +1,14 @@
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <assert.h>
+#include <string.h>
+
+int main() {
+	char test[19] = "Hello mlibc World!";
+	char *alloca_ed = strdupa(test);
+	assert(!strcmp(test, alloca_ed));
+
+	char *trimmed = strndupa(test, 5);
+	assert(!strcmp("Hello", trimmed));
+}
diff --git a/lib/mlibc/tests/posix/string.c b/lib/mlibc/tests/posix/string.c
new file mode 100644
index 0000000..9c6e036
--- /dev/null
+++ b/lib/mlibc/tests/posix/string.c
@@ -0,0 +1,29 @@
+#include <string.h>
+#include <assert.h>
+
+int main() {
+	char buf[4];
+
+	// stpncpy
+	assert(stpncpy(buf, "", 4) == buf);
+	assert(!strcmp(buf, ""));
+	
+	assert(stpncpy(buf, "123", 4) == buf + 3);
+	assert(!strcmp(buf, "123"));
+	
+	assert(stpncpy(buf, "12", 4) == buf + 2);
+	assert(buf[0] == '1' && buf[1] == '2' && buf[2] == '\0' && buf[3] == '\0');
+
+	assert(stpncpy(buf, "123456", 4) == buf + 4);
+	assert(buf[0] == '1' && buf[1] == '2' && buf[2] == '3' && buf[3] == '4');
+
+	// stpcpy
+	assert(stpcpy(buf, "") == buf);
+	assert(!strcmp(buf, ""));
+	
+	assert(stpcpy(buf, "12") == buf + 2);
+	assert(!strcmp(buf, "12"));
+	
+	assert(stpcpy(buf, "123") == buf + 3);
+	assert(!strcmp(buf, "123"));
+}
diff --git a/lib/mlibc/tests/posix/system.c b/lib/mlibc/tests/posix/system.c
new file mode 100644
index 0000000..d5d6317
--- /dev/null
+++ b/lib/mlibc/tests/posix/system.c
@@ -0,0 +1,18 @@
+#include <assert.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+
+int main() {
+	int res;
+
+	res = system("true");
+	assert(WIFEXITED(res));
+	assert(WEXITSTATUS(res) == 0);
+
+	res = system("false");
+	assert(WIFEXITED(res));
+	assert(WEXITSTATUS(res) == 1);
+
+	res = system(NULL);
+	assert(res == 1);
+}
diff --git a/lib/mlibc/tests/posix/time.c b/lib/mlibc/tests/posix/time.c
new file mode 100644
index 0000000..add7b92
--- /dev/null
+++ b/lib/mlibc/tests/posix/time.c
@@ -0,0 +1,191 @@
+#include <assert.h>
+#include <locale.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#define BUF_SIZE 1024
+
+int main() {
+	struct tm tm = {0};
+	char buf[BUF_SIZE];
+
+	char *a = strptime("%", "%%", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(strftime(buf, BUF_SIZE, "%%", &tm) == 1);
+	assert(!strcmp(buf, "%"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("1991-11-21", "%F", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_mday == 21);
+	assert(tm.tm_mon == 10);
+	assert(tm.tm_wday == 4);
+	assert(tm.tm_yday == 324);
+	assert(strftime(buf, BUF_SIZE, "%F", &tm) == 10);
+	assert(!strcmp(buf, "1991-11-21"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("10/19/91", "%D", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_mday == 19);
+	assert(tm.tm_mon  == 9);
+	assert(tm.tm_year == 91);
+	assert(tm.tm_wday == 6);
+	assert(tm.tm_yday == 291);
+	assert(strftime(buf, BUF_SIZE, "%D", &tm) == 8);
+	assert(!strcmp(buf, "10/19/91"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("15:23", "%R", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_min  == 23);
+	assert(tm.tm_hour == 15);
+	assert(strftime(buf, BUF_SIZE, "%R", &tm) == 5);
+	assert(!strcmp(buf, "15:23"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("17:12:56", "%T", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_sec  == 56);
+	assert(tm.tm_min  == 12);
+	assert(tm.tm_hour == 17);
+	assert(strftime(buf, BUF_SIZE, "%T", &tm) == 8);
+	assert(!strcmp(buf, "17:12:56"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("10", "%m", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_yday == 272);
+	assert(strftime(buf, BUF_SIZE, "%m", &tm) == 2);
+	assert(!strcmp(buf, "10"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("14 83", "%C %y", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_year == -417);
+	assert(strftime(buf, BUF_SIZE, "%C %y", &tm) == 5);
+	assert(!strcmp(buf, "14 83"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("32 16", "%y %C", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_year == -268);
+	assert(tm.tm_wday == 3);
+	assert(strftime(buf, BUF_SIZE, "%y %C", &tm) == 5);
+	assert(!strcmp(buf, "32 16"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("12", "%C", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_year == -700);
+	assert(tm.tm_wday == 5);
+	assert(strftime(buf, BUF_SIZE, "%C", &tm) == 2);
+	assert(!strcmp(buf, "12"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("1683-9-23", "%F", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_mday == 23);
+	assert(tm.tm_mon  == 8);
+	assert(tm.tm_year == -217);
+	assert(tm.tm_wday == 4);
+	assert(tm.tm_yday == 265);
+	assert(strftime(buf, BUF_SIZE, "%F", &tm) == 10);
+	assert(!strcmp(buf, "1683-09-23"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("14 53", "%H%t%S", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_sec  == 53);
+	assert(tm.tm_hour == 14);
+	assert(strftime(buf, BUF_SIZE, "%H%t%S", &tm) == 5);
+	assert(!strcmp(buf, "14	53"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("24", "%H", &tm);
+	assert(a == NULL);
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("0", "%I", &tm);
+	assert(a == NULL);
+	memset(&tm, 0, sizeof(tm));
+
+	setlocale(LC_TIME, "en_US.UTF-8");
+	a = strptime("10 21 PM", "%I %M %p", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_hour == 22);
+	assert(tm.tm_min  == 21);
+	assert(strftime(buf, BUF_SIZE, "%I %M %p", &tm) == 8);
+	assert(!strcmp(buf, "10 21 PM"));
+	memset(&tm, 0, sizeof(tm));
+
+	tm.tm_min = 23;
+	assert(strftime(buf, BUF_SIZE, "%I %M", &tm) == 5);
+	assert(!strcmp(buf, "12 23"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("January", "%h", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_mon == 0);
+	assert(strftime(buf, BUF_SIZE, "%h %b", &tm) == 7);
+	assert(!strcmp(buf, "Jan Jan"));
+	assert(strftime(buf, BUF_SIZE, "%B", &tm) == 7);
+	assert(!strcmp(buf, "January"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("2", "%j", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_yday == 1);
+	assert(strftime(buf, BUF_SIZE, "%j", &tm) == 3);
+	assert(!strcmp(buf, "002"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("Wednesday", "%A", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_wday == 3);
+	assert(strftime(buf, BUF_SIZE, "%A", &tm) == 9);
+	assert(!strcmp(buf, "Wednesday"));
+	memset(&tm, 0, sizeof(tm));
+
+	a = strptime("11:51:13 PM", "%r", &tm);
+	assert(a != NULL);
+	assert(*a == '\0');
+	assert(tm.tm_hour == 23);
+	assert(tm.tm_min == 51);
+	assert(tm.tm_sec == 13);
+	assert(strftime(buf, BUF_SIZE, "%r", &tm) == 11);
+	assert(!strcmp(buf, "11:51:13 PM"));
+	memset(&tm, 0, sizeof(tm));
+
+	tm.tm_hour = 0;
+	tm.tm_min = 51;
+	tm.tm_sec = 13;
+	assert(strftime(buf, BUF_SIZE, "%r", &tm) == 11);
+	assert(!strcmp(buf, "12:51:13 AM"));
+	memset(&tm, 0, sizeof(tm));
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat"
+	assert(strftime(buf, BUF_SIZE, "%", &tm) == 1);
+	fprintf(stderr, "%s\n", buf);
+	assert(!strcmp(buf, "%"));
+	memset(&tm, 0, sizeof(tm));
+#pragma GCC diagnostic pop
+}
diff --git a/lib/mlibc/tests/posix/timer.c b/lib/mlibc/tests/posix/timer.c
new file mode 100644
index 0000000..f39e928
--- /dev/null
+++ b/lib/mlibc/tests/posix/timer.c
@@ -0,0 +1,25 @@
+#include <stdio.h>
+#include <sys/time.h>
+#include <assert.h>
+
+int main() {
+	struct timeval a = {0, 0};
+	struct timeval b = {0, 0};
+	struct timeval res = {0, 0};
+	a.tv_sec = 10;
+	assert(timerisset(&a) == 1);
+	timerclear(&a);
+	assert(timerisset(&a) == 0);
+	a.tv_sec = 40;
+	a.tv_usec = 500;
+	b.tv_sec = 10;
+	b.tv_usec = 20;
+	timeradd(&a, &b, &res);
+	assert(res.tv_sec == 50);
+	assert(res.tv_usec == 520);
+	timerclear(&res);
+	timersub(&a, &b, &res);
+	assert(res.tv_sec == 30);
+	assert(res.tv_usec == 480);
+	return 0;
+}
diff --git a/lib/mlibc/tests/posix/vfork.c b/lib/mlibc/tests/posix/vfork.c
new file mode 100644
index 0000000..5f8b71d
--- /dev/null
+++ b/lib/mlibc/tests/posix/vfork.c
@@ -0,0 +1,28 @@
+#include <assert.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+void prevent_atforks(void){
+	exit(1);
+}
+
+int main() {
+	pid_t pid;
+	int status;
+	assert(!pthread_atfork(prevent_atforks, NULL, NULL));
+
+	switch (pid = vfork()) {
+	case -1:
+		perror("vfork");
+		abort();
+	case 0:
+		_exit(12);
+	default: break;
+	}
+
+	assert(wait(&status) == pid);
+	assert(WIFEXITED(status) && WEXITSTATUS(status) == 12);
+}
diff --git a/lib/mlibc/tests/posix/waitid.c b/lib/mlibc/tests/posix/waitid.c
new file mode 100644
index 0000000..e69b1ef
--- /dev/null
+++ b/lib/mlibc/tests/posix/waitid.c
@@ -0,0 +1,20 @@
+#include <assert.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+siginfo_t si;
+
+int main() {
+	int pid = fork();
+
+	if(!pid)
+		exit(69);
+
+	int ret = waitid(P_ALL, 0, &si, WEXITED);
+	assert(ret == 0);
+	assert(si.si_pid == pid);
+	assert(si.si_signo == SIGCHLD);
+	assert(si.si_code == CLD_EXITED);
+}
\ No newline at end of file
diff --git a/lib/mlibc/tests/posix/wcwidth.c b/lib/mlibc/tests/posix/wcwidth.c
new file mode 100644
index 0000000..2e6fc8c
--- /dev/null
+++ b/lib/mlibc/tests/posix/wcwidth.c
@@ -0,0 +1,67 @@
+#include <assert.h>
+#include <locale.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <wchar.h>
+
+#if UINTPTR_MAX == UINT64_MAX
+#define WCHAR_SPEC ""
+#else
+#define WCHAR_SPEC "l"
+#endif
+
+/*
+ * The code in this test is taken from https://github.com/termux/wcwidth/,
+ * under the following license:
+ *
+ * Copyright (C) Fredrik Fornwall 2016.
+ * Distributed under the MIT License.
+ *
+ * Implementation of wcwidth(3) as a C port of:
+ * https://github.com/jquast/wcwidth
+ *
+ * Report issues at:
+ * https://github.com/termux/wcwidth
+ */
+
+static int tests_run;
+static int test_failures;
+
+void assertWidthIs(int expected_width, wchar_t c) {
+	tests_run++;
+	int actual_width = wcwidth(c);
+	if (actual_width != expected_width) {
+		fprintf(stderr, "ERROR: wcwidth(U+%04" WCHAR_SPEC "x, '%lc') returned %d, expected %d\n", c, (wint_t) c, actual_width, expected_width);
+		test_failures++;
+	}
+}
+
+int main() {
+	setlocale(LC_CTYPE, "C.UTF-8");
+	assertWidthIs(1, 'a');
+	assertWidthIs(1, L'ö');
+
+	// Some wide:
+	assertWidthIs(2, L'Ａ');
+	assertWidthIs(2, L'Ｂ');
+	assertWidthIs(2, L'Ｃ');
+	assertWidthIs(2, L'中');
+	assertWidthIs(2, L'文');
+	assertWidthIs(2, 0x679C);
+	assertWidthIs(2, 0x679D);
+	assertWidthIs(2, 0x2070E);
+	assertWidthIs(2, 0x20731);
+
+#ifndef USE_HOST_LIBC
+	assertWidthIs(1, 0x11A3);
+#endif
+
+	assertWidthIs(2, 0x1F428); // Koala emoji.
+	assertWidthIs(2, 0x231a);  // Watch emoji.
+
+	if (test_failures > 0) printf("%d tests FAILED, ", test_failures);
+	printf("%d tests OK\n", tests_run - test_failures);
+	return (test_failures == 0) ? 0 : 1;
+}
diff --git a/lib/mlibc/tests/posix/wordexp.c b/lib/mlibc/tests/posix/wordexp.c
new file mode 100644
index 0000000..063a374
--- /dev/null
+++ b/lib/mlibc/tests/posix/wordexp.c
@@ -0,0 +1,140 @@
+#include <assert.h>
+#include <limits.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <pwd.h>
+#include <unistd.h>
+#include <wordexp.h>
+
+static const char *wordexp_return_stringify(int val, int *should_free);
+
+struct we_test {
+	int expected_return;
+	const char *words;
+	int flags;
+	const char *wordv[16];
+	size_t wordc;
+} test_cases[] = {
+	/* (unbalanced) pairs */
+	{WRDE_SYNTAX, "\\", 0, {NULL}, 0},
+	{WRDE_SYNTAX, "\'", 0, {NULL}, 0},
+	{0, "\'\'", 0, {""}, 1},
+	{0, "\'\"\'", 0, {"\""}, 1},
+	{WRDE_SYNTAX, "\"\'", 0, {NULL}, 0},
+
+	/* numbers & calculations */
+	{0, "$((5+5))", 0, {"10"}, 1},
+	{0, "$((-5+5))", 0, {"0"}, 1},
+	{0, "$((010))", 0, {"8"}, 1},
+	{0, "$((0x10))", 0, {"16"}, 1},
+
+	/* errant symbols */
+	{WRDE_BADCHAR, "(string", WRDE_NOCMD, {NULL}, 0},
+	{WRDE_BADCHAR, "string)", WRDE_NOCMD, {NULL}, 0},
+	{WRDE_BADCHAR, "{string", WRDE_NOCMD, {NULL}, 0},
+	{WRDE_BADCHAR, "string}", WRDE_NOCMD, {NULL}, 0},
+	{WRDE_BADCHAR, "<string", WRDE_NOCMD, {NULL}, 0},
+	{WRDE_BADCHAR, "string>", WRDE_NOCMD, {NULL}, 0},
+	{WRDE_BADCHAR, "string|", WRDE_NOCMD, {NULL}, 0},
+	{WRDE_BADCHAR, "string;", WRDE_NOCMD, {NULL}, 0},
+	{WRDE_BADCHAR, "string&", WRDE_NOCMD, {NULL}, 0},
+
+	/* command substitution with WRDE_NOCMD */
+	{WRDE_CMDSUB, "$(pwd)", WRDE_NOCMD, {NULL}, 0},
+
+	/* env vars */
+	{WRDE_BADVAL, "$DOES_NOT_EXIST", WRDE_UNDEF, {NULL}, 0},
+
+	/* normal arguments */
+	{0, "arg1 arg2", 0, {"arg1", "arg2"}, 2},
+	{-1, NULL, 0, {NULL}, 0},
+};
+
+int main() {
+	wordexp_t we;
+
+	wordexp("$(pwd)", &we, 0);
+	char *cwd = getcwd(NULL, 0);
+	assert(!strcmp(cwd, we.we_wordv[0]));
+	wordfree(&we);
+	free(cwd);
+
+	char *home;
+	assert(asprintf(&home, "%s/.config", getenv("HOME")) != -1);
+	wordexp("$HOME ~ ~/.config", &we, WRDE_REUSE);
+	assert(!strcmp(getenv("HOME"), we.we_wordv[0]));
+	assert(!strcmp(getenv("HOME"), we.we_wordv[1]));
+	assert(!strcmp(home, we.we_wordv[2]));
+	free(home);
+	wordfree(&we);
+
+	struct passwd *pw = getpwnam("root");
+	assert(asprintf(&home, "%s/.config", pw->pw_dir) != -1);
+	wordexp("~root ~root/.config", &we, WRDE_REUSE);
+	assert(!strcmp(pw->pw_dir, we.we_wordv[0]));
+	assert(!strcmp(home, we.we_wordv[1]));
+	free(home);
+	wordfree(&we);
+
+	size_t i = 0;
+
+	for(struct we_test *test = &test_cases[i]; test->expected_return != -1; test = &test_cases[++i]) {
+		wordexp_t test_we;
+
+		int should_free;
+		const char *expected = wordexp_return_stringify(test->expected_return, &should_free);
+		fprintf(stderr, "TESTCASE %zu: '%s' with flags %d expected to return %s\n", i, test->words, test->flags, expected);
+		int test_ret = wordexp(test->words, &test_we, test->flags);
+
+		if(test_ret != test->expected_return) {
+			fprintf(stderr, "\twordexp() returned %s, but we expect %s\n", wordexp_return_stringify(test_ret, &should_free), wordexp_return_stringify(test->expected_return, &should_free));
+		}
+
+		assert(test_ret == test->expected_return);
+
+		if(test_ret != 0)
+			continue;
+
+		assert(test_we.we_wordc == test->wordc);
+
+		for(size_t j = 0; j < 16 && j < test->wordc; j++) {
+			assert(test->wordv[j] && test_we.we_wordv[j]);
+			assert(!strcmp(test->wordv[j], test_we.we_wordv[j]));
+		}
+
+		wordfree(&test_we);
+		if (should_free)
+			free((void *)expected);
+	}
+
+	exit(EXIT_SUCCESS);
+}
+
+struct wordexp_return_val {
+	int val;
+	const char *string;
+} wordexp_return_vals[] = {
+	{0, "WRDE_SUCCESS"},
+	{WRDE_BADCHAR, "WRDE_BADCHAR"},
+	{WRDE_BADVAL, "WRDE_BADVAL"},
+	{WRDE_CMDSUB, "WRDE_CMDSUB"},
+	{WRDE_SYNTAX, "WRDE_SYNTAX"},
+	{-1, NULL},
+};
+
+static const char *wordexp_return_stringify(int val, int *should_free) {
+	for(size_t i = 0; wordexp_return_vals[i].val != -1 || wordexp_return_vals[i].string; i++) {
+		if(wordexp_return_vals[i].val == val) {
+			*should_free = 0;
+			return wordexp_return_vals[i].string;
+		}
+	}
+
+	char *unknown;
+	assert(asprintf(&unknown, "unknown return value %d", val) != -1);
+	*should_free = 1;
+
+	return unknown;
+}