add syscall unit tests

Add tests for io_uring_setup, io_uring_register and io_uring_enter.
The test coverage is nowhere near complete and the reporting is not
uniform.  But, it's a start.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

4 files changed, 978 insertions, 2 deletions

diff --git a/test/Makefile b/test/Makefile
index 8d8a65f..e1af59a 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -1,10 +1,12 @@
 CFLAGS ?= -g -O2 -Wall -D_GNU_SOURCE -L../src/
 
-all_targets += io_uring-test io_uring-cp poll poll-cancel ring-leak fsync
+all_targets += io_uring-test io_uring-cp poll poll-cancel ring-leak fsync \
+	io_uring_setup io_uring_register io_uring_enter
 
 all: $(all_targets)
 
-test_srcs := io_uring-test.c io_uring-cp.c poll.c poll-cancel.c ring-leak.c fsync.c
+test_srcs := io_uring-test.c io_uring-cp.c poll.c poll-cancel.c ring-leak.c \
+	fsync.c io_uring_setup.c io_uring_register.c io_uring_enter.c
 
 test_objs := $(patsubst %.c,%.ol,$(test_srcs))
 
@@ -20,5 +22,11 @@ ring-leak: ring-leak.c
 	$(CC) $(CFLAGS) -o $@ ring-leak.c -luring
 fsync: fsync.c
 	$(CC) $(CFLAGS) -o $@ fsync.c -luring
+io_uring_setup: io_uring_setup.c
+	$(CC) $(CFLAGS) -o $@ io_uring_setup.c -luring
+io_uring_register: io_uring_register.c
+	$(CC) $(CFLAGS) -o $@ io_uring_register.c -luring
+io_uring_enter: io_uring_enter.c
+	$(CC) $(CFLAGS) -o $@ io_uring_enter.c -luring
 clean:
 	rm -f $(all_targets) $(test_objs)
diff --git a/test/io_uring_enter.c b/test/io_uring_enter.c
new file mode 100644
index 0000000..a86eeaa
--- /dev/null
+++ b/test/io_uring_enter.c
@@ -0,0 +1,282 @@
+/*
+ * io_uring_enter.c
+ *
+ * Description: Unit tests for the io_uring_enter system call.
+ *
+ * Copyright 2019, Red Hat, Inc.
+ * Author: Jeff Moyer <jmoyer@redhat.com>
+ */
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/sysinfo.h>
+#include <poll.h>
+#include <assert.h>
+#include <sys/uio.h>
+#include <sys/mman.h>
+#include <linux/mman.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <limits.h>
+#include <sys/time.h>
+#include "../src/liburing.h"
+#include "../src/barrier.h"
+
+#define IORING_MAX_ENTRIES 4096
+
+int
+expect_failed_submit(struct io_uring *ring, int error)
+{
+	int ret;
+
+	ret = io_uring_submit(ring);
+	if (ret == 1) {
+		printf("expected failure, but io_uring_submit succeeded.\n");
+		return 1;
+	}
+
+	if (errno != error) {
+		printf("expected %d, got %d\n", error, errno);
+		return 1;
+	}
+
+	return 0;
+}
+
+int
+expect_fail(int fd, unsigned int to_submit, unsigned int min_complete,
+	    unsigned int flags, sigset_t *sig, int error)
+{
+	int ret;
+
+	ret = io_uring_enter(fd, to_submit, min_complete, flags, sig);
+	if (ret != -1) {
+		printf("expected %s, but call succeeded\n", strerror(error));
+		return 1;
+	}
+
+	if (errno != error) {
+		printf("expected %d, got %d\n", error, errno);
+		return 1;
+	}
+
+	return 0;
+}
+
+int
+try_io_uring_enter(int fd, unsigned int to_submit, unsigned int min_complete,
+		   unsigned int flags, sigset_t *sig, int expect, int error)
+{
+	int ret;
+
+	printf("io_uring_enter(%d, %u, %u, %u, %p)\n", fd, to_submit,
+	       min_complete, flags, sig);
+
+	if (expect == -1)
+		return expect_fail(fd, to_submit, min_complete,
+				   flags, sig, error);
+
+	ret = io_uring_enter(fd, to_submit, min_complete, flags, sig);
+	if (ret != expect) {
+		printf("Expected %d, got %d\n", expect, errno);
+		return 1;
+	}
+
+	return 0;
+}
+
+/*
+ * prep a read I/O.  index is treated like a block number.
+ */
+int
+setup_file(off_t len)
+{
+	int fd, ret;
+	static char template[32] = "/tmp/io_uring_enter-test.XXXXXX";
+	char buf[4096];
+
+	fd = mkstemp(template);
+	if (fd < 0) {
+		perror("mkstemp");
+		exit(1);
+	}
+	ret = ftruncate(fd, len);
+	if (ret < 0) {
+		perror("ftruncate");
+		exit(1);
+	}
+
+	ret = read(fd, buf, 4096);
+	if (ret != 4096) {
+		printf("read returned %d, expected 4096\n", ret);
+		exit(1);
+	}
+
+	return fd;
+}
+
+void
+io_prep_read(struct io_uring_sqe *sqe, int fd, off_t offset, size_t len)
+{
+	struct iovec *iov;
+
+	iov = malloc(sizeof(*iov));
+	assert(iov);
+
+	iov->iov_base = malloc(len);
+	assert(iov->iov_base);
+	iov->iov_len = len;
+
+	io_uring_prep_readv(sqe, fd, iov, 1, offset);
+	io_uring_sqe_set_data(sqe, iov); // free on completion
+}
+
+void
+reap_events(struct io_uring *ring, unsigned nr)
+{
+	int ret;
+	unsigned left = nr;
+	struct io_uring_cqe *cqe;
+	struct iovec *iov;
+	struct timeval start, now, elapsed;
+
+	printf("Reaping %u I/Os\n", nr);
+	gettimeofday(&start, NULL);
+	while (left) {
+		ret = io_uring_wait_completion(ring, &cqe);
+		if (ret < 0) {
+			printf("io_uring_wait_completion returned %d\n", ret);
+			printf("expected success\n");
+			exit(1);
+		}
+		if (cqe->res != 4096)
+			printf("cqe->res: %d, expected 4096\n", cqe->res);
+		iov = (struct iovec *)cqe->user_data;
+		free(iov->iov_base);
+		free(iov);
+		left--;
+
+		gettimeofday(&now, NULL);
+		timersub(&now, &start, &elapsed);
+		if (elapsed.tv_sec > 10) {
+			printf("Timed out waiting for I/Os to complete.\n");
+			printf("%u expected, %u completed\n", nr, left);
+			break;
+		}
+	}
+}
+
+void
+submit_io(struct io_uring *ring, unsigned nr)
+{
+	int fd, ret;
+	off_t file_len;
+	unsigned i;
+	struct io_uring_sqe *sqe;
+
+	printf("Allocating %u sqes\n", nr);
+	file_len = nr * 4096;
+	fd = setup_file(file_len);
+	for (i = 0; i < nr; i++) {
+		/* allocate an sqe */
+		sqe = io_uring_get_sqe(ring);
+		/* fill it in */
+		io_prep_read(sqe, fd, i * 4096, 4096);
+	}
+
+	/* submit the I/Os */
+	printf("Submitting %u I/Os\n", nr);
+	ret = io_uring_submit(ring);
+	if (ret < 0) {
+		perror("io_uring_enter");
+		exit(1);
+	}
+	printf("Done\n");
+}
+
+int
+main(int argc, char **argv)
+{
+	int ret;
+	unsigned int status = 0;
+	struct io_uring ring;
+	struct io_uring_sq *sq = &ring.sq;
+	unsigned ktail, mask, index;
+	unsigned sq_entries;
+	unsigned completed, dropped;
+
+	ret = io_uring_queue_init(IORING_MAX_ENTRIES, &ring, 0);
+	if (ret < 0) {
+		perror("io_uring_queue_init");
+		exit(1);
+	}
+	mask = *sq->kring_mask;
+
+	/* invalid flags */
+	status |= try_io_uring_enter(ring.ring_fd, 1, 0, ~0U, NULL, -1, EINVAL);
+
+	/* invalid fd, EBADF */
+	status |= try_io_uring_enter(-1, 0, 0, 0, NULL, -1, EBADF);
+
+	/* valid, non-ring fd, EOPNOTSUPP */
+	status |= try_io_uring_enter(0, 0, 0, 0, NULL, -1, EOPNOTSUPP);
+
+	/* to_submit: 0, flags: 0;  should get back 0. */
+	status |= try_io_uring_enter(ring.ring_fd, 1, 0, 0, NULL, 0, 0);
+
+	/* fill the sq ring */
+	sq_entries = *ring.sq.kring_entries;
+	submit_io(&ring, sq_entries);
+	printf("Waiting for %u events\n", sq_entries);
+	ret = io_uring_enter(ring.ring_fd, 0, sq_entries,
+			     IORING_ENTER_GETEVENTS, NULL);
+	if (ret < 0) {
+		perror("io_uring_enter");
+		status = 1;
+	} else {
+		/*
+		 * This is a non-IOPOLL ring, which means that io_uring_enter
+		 * should not return until min_complete events are available
+		 * in the completion queue.
+		 */
+		completed = *ring.cq.ktail - *ring.cq.khead;
+		if (completed != sq_entries) {
+			printf("Submitted %u I/Os, but only got %u completions\n",
+			       sq_entries, completed);
+			status = 1;
+		}
+		reap_events(&ring, sq_entries);
+	}
+
+	/*
+	 * Add an invalid index to the submission queue.  This should
+	 * result in the dropped counter increasing.
+	 */
+	printf("Submitting invalid sqe index.\n");
+	index = *sq->kring_entries + 1; // invalid index
+	dropped = *sq->kdropped;
+	ktail = *sq->ktail;
+	sq->array[ktail & mask] = index;
+	++ktail;
+	write_barrier();
+	*sq->ktail = ktail;
+	write_barrier();
+
+	ret = io_uring_enter(ring.ring_fd, 1, 0, 0, NULL);
+	/* now check to see if our sqe was dropped */
+	if (*sq->kdropped == dropped) {
+		printf("dropped counter did not increase\n");
+		status = 1;
+	}
+
+	if (!status) {
+		printf("PASS\n");
+		return 0;
+	}
+
+	printf("FAIL\n");
+	return -1;
+}
diff --git a/test/io_uring_register.c b/test/io_uring_register.c
new file mode 100644
index 0000000..30a225b
--- /dev/null
+++ b/test/io_uring_register.c
@@ -0,0 +1,525 @@
+/*
+ * io_uring_register.c
+ *
+ * Description: Unit tests for the io_uring_register system call.
+ *
+ * Copyright 2019, Red Hat, Inc.
+ * Author: Jeff Moyer <jmoyer@redhat.com>
+ */
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/sysinfo.h>
+#include <poll.h>
+#include <assert.h>
+#include <sys/uio.h>
+#include <sys/mman.h>
+#include <linux/mman.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <limits.h>
+#include "../src/liburing.h"
+
+static int pagesize;
+static rlim_t mlock_limit;
+static int devnull;
+
+int
+expect_fail(int fd, unsigned int opcode, void *arg,
+	    unsigned int nr_args, int error)
+{
+	int ret;
+
+	printf("io_uring_register(%d, %u, %p, %u)\n",
+	       fd, opcode, arg, nr_args);
+	ret = io_uring_register(fd, opcode, arg, nr_args);
+	if (ret != -1) {
+		int ret2 = 0;
+
+		printf("expected %s, but call succeeded\n", strerror(error));
+		if (opcode == IORING_REGISTER_BUFFERS) {
+			ret2 = io_uring_register(fd, IORING_UNREGISTER_BUFFERS,
+						 0, 0);
+		} else if (opcode == IORING_REGISTER_FILES) {
+			ret2 = io_uring_register(fd, IORING_UNREGISTER_FILES,
+						 0, 0);
+		}
+		if (ret2) {
+			printf("internal error: failed to unregister\n");
+			exit(1);
+		}
+		return 1;
+	}
+
+	if (errno != error) {
+		printf("expected %d, got %d\n", error, errno);
+		return 1;
+	}
+	return 0;
+}
+
+int
+new_io_uring(int entries, struct io_uring_params *p)
+{
+	int fd;
+
+	fd = io_uring_setup(entries, p);
+	if (fd < 0) {
+		perror("io_uring_setup");
+		exit(1);
+	}
+	return fd;
+}
+
+#define MAXFDS (UINT_MAX * sizeof(int))
+
+void *
+map_filebacked(size_t size)
+{
+	int fd, ret;
+	void *addr;
+	char template[32] = "io_uring_register-test-XXXXXXXX";
+
+	fd = mkstemp(template);
+	if (fd < 0) {
+		perror("mkstemp");
+		return NULL;
+	}
+	unlink(template);
+
+	ret = ftruncate(fd, size);
+	if (ret < 0) {
+		perror("ftruncate");
+		close(fd);
+		return NULL;
+	}
+
+	addr = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+	if (addr == MAP_FAILED) {
+		perror("mmap");
+		close(fd);
+		return NULL;
+	}
+
+	close(fd);
+	return addr;
+}
+
+/*
+ * NOTE: this is now limited by SCM_MAX_FD (253).  Keep the code for now,
+ * but probably should augment it to test 253 and 254, specifically.
+ */
+int
+test_max_fds(int uring_fd)
+{
+	int status = 1;
+	int ret;
+	void *fd_as; /* file descriptor address space */
+	int fdtable_fd; /* fd for the file that will be mapped over and over */
+	int io_fd; /* the valid fd for I/O -- /dev/null */
+	int *fds; /* used to map the file into the address space */
+	char template[32] = "io_uring_register-test-XXXXXXXX";
+	unsigned long long i, nr_maps, nr_fds;
+
+	/*
+	 * First, mmap anonymous the full size.  That will guarantee the
+	 * mapping will fit in the memory area selected by mmap.  Then,
+	 * over-write that mapping using a file-backed mapping, 128MiB at
+	 * a time using MAP_FIXED.
+	 */
+	fd_as = mmap(NULL, UINT_MAX * sizeof(int), PROT_READ|PROT_WRITE,
+		     MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+	if (fd_as == MAP_FAILED) {
+		perror("mmap fd_as");
+		exit(1);
+	}
+	printf("allocated %lu bytes of address space\n", UINT_MAX * sizeof(int));
+
+	fdtable_fd = mkstemp(template);
+	if (fdtable_fd < 0) {
+		perror("mkstemp");
+		exit(1);
+	}
+	unlink(template);
+	ret = ftruncate(fdtable_fd, 128*1024*1024);
+	if (ret < 0) {
+		perror("ftruncate");
+		exit(1);
+	}
+
+	io_fd = open("/dev/null", O_RDWR);
+	if (io_fd < 0) {
+		perror("open /dev/null");
+		exit(1);
+	}
+	fds = mmap(fd_as, 128*1024*1024, PROT_READ|PROT_WRITE,
+		   MAP_SHARED|MAP_FIXED, fdtable_fd, 0);
+	if (fds == MAP_FAILED) {
+		perror("mmap fdtable");
+		exit(1);
+	}
+
+	/* fill the fd table */
+	nr_fds = 128*1024*1024 / sizeof(int);
+	for (i = 0; i < nr_fds; i++)
+		fds[i] = io_fd;
+
+	/* map the file through the rest of the address space */
+	nr_maps = (UINT_MAX * sizeof(int)) / (128*1024*1024);
+	for (i = 0; i < nr_maps; i++) {
+		fds = &fds[nr_fds]; /* advance fds by 128MiB */
+		fds = mmap(fds, 128*1024*1024, PROT_READ|PROT_WRITE,
+			   MAP_SHARED|MAP_FIXED, fdtable_fd, 0);
+		if (fds == MAP_FAILED) {
+			printf("mmap failed at offset %lu\n", (char *)fd_as - (char *)fds);
+			exit(1);
+		}
+	}
+
+	/* Now fd_as points to the file descriptor array. */
+	/*
+	 * We may not be able to map all of these files.  Let's back off
+	 * until success.
+	 */
+	nr_fds = UINT_MAX;
+	while (nr_fds) {
+		ret = io_uring_register(uring_fd, IORING_REGISTER_FILES,
+					fd_as, nr_fds);
+		if (ret != 0) {
+			nr_fds /= 2;
+			continue;
+		}
+		printf("io_uring_register(%d, IORING_REGISTER_FILES, %p, %llu)"
+		       "...succeeded\n", uring_fd, fd_as, nr_fds);
+		status = 0;
+		printf("io_uring_register(%d, IORING_UNREGISTER_FILES, 0, 0)...",
+		       uring_fd);
+		ret = io_uring_register(uring_fd, IORING_UNREGISTER_FILES, 0, 0);
+		if (ret < 0) {
+			ret = errno;
+			printf("failed\n");
+			errno = ret;
+			perror("io_uring_register UNREGISTER_FILES");
+			exit(1);
+		}
+		printf("succeeded\n");
+		break;
+	}
+
+	close(io_fd);
+	close(fdtable_fd);
+	ret = munmap(fd_as, UINT_MAX * sizeof(int));
+	if (ret != 0) {
+		printf("munmap(%lu) failed\n", UINT_MAX * sizeof(int));
+		exit(1);
+	}
+
+	return status;
+}
+
+int
+test_memlock_exceeded(int fd)
+{
+	int ret;
+	void *buf;
+	struct iovec iov;
+
+	iov.iov_len = mlock_limit * 2;
+	buf = malloc(iov.iov_len);
+	assert(buf);
+	iov.iov_base = buf;
+
+	while (iov.iov_len) {
+		ret = io_uring_register(fd, IORING_REGISTER_BUFFERS, &iov, 1);
+		if (ret < 0) {
+			if (errno == ENOMEM) {
+				printf("io_uring_register of %lu bytes failed "
+				       "with ENOMEM (expected).\n", iov.iov_len);
+				iov.iov_len /= 2;
+				continue;
+			}
+			printf("expected success or EFAULT, got %d\n", errno);
+			free(buf);
+			return 1;
+		}
+		printf("successfully registered %lu bytes (%d).\n",
+		       iov.iov_len, ret);
+		ret = io_uring_register(fd, IORING_UNREGISTER_BUFFERS, NULL, 0);
+		if (ret != 0) {
+			printf("error: unregister failed with %d\n", errno);
+			free(buf);
+			return 1;
+		}
+		break;
+	}
+	if (!iov.iov_len)
+		printf("Unable to register buffers.  Check memlock rlimit.\n");
+
+	free(buf);
+	return 0;
+}
+
+int
+test_iovec_nr(int fd)
+{
+	int i, ret, status = 0;
+	unsigned int nr = UIO_MAXIOV + 1;
+	struct iovec *iovs;
+	void *buf;
+
+	buf = malloc(pagesize);
+	assert(buf);
+
+	iovs = malloc(nr * sizeof(struct iovec));
+	assert(iovs);
+
+	for (i = 0; i < nr; i++) {
+		iovs[i].iov_base = buf;
+		iovs[i].iov_len = pagesize;
+	}
+
+	status |= expect_fail(fd, IORING_REGISTER_BUFFERS, iovs, nr, EINVAL);
+
+	/* reduce to UIO_MAXIOV */
+	nr--;
+	printf("io_uring_register(%d, %u, %p, %u)\n",
+	       fd, IORING_REGISTER_BUFFERS, iovs, nr);
+	ret = io_uring_register(fd, IORING_REGISTER_BUFFERS, iovs, nr);
+	if (ret != 0) {
+		printf("expected success, got %d\n", errno);
+		status = 1;
+	} else
+		io_uring_register(fd, IORING_UNREGISTER_BUFFERS, 0, 0);
+
+	free(buf);
+	free(iovs);
+	return status;
+}
+
+/*
+ * io_uring limit is 1G.  iov_len limit is ~OUL, I think
+ */
+int
+test_iovec_size(int fd)
+{
+	unsigned int status = 0;
+	int ret;
+	struct iovec iov;
+	void *buf;
+
+	/* NULL pointer for base */
+	iov.iov_base = 0;
+	iov.iov_len = 4096;
+	status |= expect_fail(fd, IORING_REGISTER_BUFFERS, &iov, 1, EFAULT);
+
+	/* valid base, 0 length */
+	iov.iov_base = &buf;
+	iov.iov_len = 0;
+	status |= expect_fail(fd, IORING_REGISTER_BUFFERS, &iov, 1, EFAULT);
+
+	/* valid base, length exceeds size */
+	/* this requires an unampped page directly after buf */
+	buf = mmap(NULL, 2 * pagesize, PROT_READ|PROT_WRITE,
+		   MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	assert(buf != MAP_FAILED);
+	ret = munmap(buf + pagesize, pagesize);
+	assert(ret == 0);
+	iov.iov_base = buf;
+	iov.iov_len = 2 * pagesize;
+	status |= expect_fail(fd, IORING_REGISTER_BUFFERS, &iov, 1, EFAULT);
+	munmap(buf, pagesize);
+
+	/* huge page */
+	buf = mmap(NULL, 2*1024*1024, PROT_READ|PROT_WRITE,
+		   MAP_PRIVATE | MAP_HUGETLB | MAP_HUGE_2MB | MAP_ANONYMOUS,
+		   -1, 0);
+	if (buf == MAP_FAILED) {
+		printf("Unable to map a huge page.  Try increasing "
+		       "/proc/sys/vm/nr_hugepages by at least 1.\n");
+		printf("Skipping the hugepage test\n");
+	} else {
+		/*
+		 * This should succeed, so long as RLIMIT_MEMLOCK is
+		 * not exceeded
+		 */
+		iov.iov_base = buf;
+		iov.iov_len = 2*1024*1024;
+		ret = io_uring_register(fd, IORING_REGISTER_BUFFERS, &iov, 1);
+		if (ret < 0) {
+			if (errno == ENOMEM)
+				printf("Unable to test registering of a huge "
+				       "page.  Try increasing the "
+				       "RLIMIT_MEMLOCK resource limit by at "
+				       "least 2MB.");
+			else {
+				printf("expected success, got %d\n", errno);
+				status = 1;
+			}
+		} else {
+			printf("Success!\n");
+			ret = io_uring_register(fd, IORING_UNREGISTER_BUFFERS,
+						0, 0);
+			if (ret < 0) {
+				perror("io_uring_unregister");
+				status = 1;
+			}
+		}
+	}
+	ret = munmap(iov.iov_base, iov.iov_len);
+	assert(ret == 0);
+
+	/* file-backed buffers -- not supported */
+	buf = map_filebacked(2*1024*1024);
+	if (!buf)
+		status = 1;
+	iov.iov_base = buf;
+	iov.iov_len = 2*1024*1024;
+	printf("reserve file-backed buffers\n");
+	status |= expect_fail(fd, IORING_REGISTER_BUFFERS, &iov, 1, EOPNOTSUPP);
+	munmap(buf, 2*1024*1024);
+
+	/* bump up against the soft limit and make sure we get EFAULT
+	 * or whatever we're supposed to get.  NOTE: this requires
+	 * running the test as non-root. */
+	if (getuid() != 0)
+		status |= test_memlock_exceeded(fd);
+
+	return status;
+}
+
+void
+dump_sqe(struct io_uring_sqe *sqe)
+{
+	printf("\topcode: %d\n", sqe->opcode);
+	printf("\tflags:  0x%.8x\n", sqe->flags);
+	printf("\tfd:     %d\n", sqe->fd);
+	if (sqe->opcode == IORING_OP_POLL_ADD)
+		printf("\tpoll_events: 0x%.8x\n", sqe->poll_events);
+}
+
+int
+ioring_poll(struct io_uring *ring, int fd, int fixed)
+{
+	int ret;
+	struct io_uring_sqe *sqe;
+	struct io_uring_cqe *cqe;
+
+	sqe = io_uring_get_sqe(ring);
+	memset(sqe, 0, sizeof(*sqe));
+	sqe->opcode = IORING_OP_POLL_ADD;
+	if (fixed)
+		sqe->flags = IOSQE_FIXED_FILE;
+	sqe->fd = fd;
+	sqe->poll_events = POLLIN|POLLOUT;
+
+	printf("io_uring_submit:\n");
+	dump_sqe(sqe);
+	ret = io_uring_submit(ring);
+	if (ret != 1) {
+		printf("failed to submit poll sqe: %d.\n", errno);
+		return 1;
+	}
+
+	ret = io_uring_wait_completion(ring, &cqe);
+	if (ret < 0) {
+		printf("io_uring_wait_completion failed with %d\n", ret);
+		return 1;
+	}
+	if (cqe->res != POLLOUT) {
+		printf("io_uring_wait_completion: expected 0x%.8x, got 0x%.8x\n",
+		       POLLOUT, cqe->res);
+		return 1;
+	}
+
+	return 0;
+}
+
+int
+test_poll_ringfd(void)
+{
+	int status = 0;
+	int ret;
+	int fd;
+	struct io_uring ring;
+
+	ret = io_uring_queue_init(1, &ring, 0);
+	if (ret) {
+		perror("io_uring_queue_init");
+		return 1;
+	}
+	fd = ring.ring_fd;
+
+	/* try polling the ring fd */
+	status = ioring_poll(&ring, fd, 0);
+
+	/*
+	 * now register the ring fd, and try the poll again.  This should
+	 * fail, because the kernel does not allow registering of the
+	 * ring_fd.
+	 */
+	status |= expect_fail(fd, IORING_REGISTER_FILES, &fd, 1, EBADF);
+
+	/* tear down queue */
+	io_uring_queue_exit(&ring);
+
+	return status;
+}
+
+int
+main(int argc, char **argv)
+{
+	int fd, ret;
+	unsigned int status = 0;
+	struct io_uring_params p;
+	struct rlimit rlim;
+
+	/* setup globals */
+	pagesize = getpagesize();
+	ret = getrlimit(RLIMIT_MEMLOCK, &rlim);
+	if (ret < 0) {
+		perror("getrlimit");
+		return 1;
+	}
+	mlock_limit = rlim.rlim_cur;
+	printf("RELIMIT_MEMLOCK: %lu (%lu)\n", rlim.rlim_cur, rlim.rlim_max);
+	devnull = open("/dev/null", O_RDWR);
+	if (devnull < 0) {
+		perror("open /dev/null");
+		exit(1);
+	}
+
+	/* invalid fd */
+	status |= expect_fail(-1, 0, NULL, 0, EBADF);
+	/* valid fd that is not an io_uring fd */
+	status |= expect_fail(devnull, 0, NULL, 0, EOPNOTSUPP);
+
+	/* invalid opcode */
+	memset(&p, 0, sizeof(p));
+	fd = new_io_uring(1, &p);
+	ret = expect_fail(fd, ~0U, NULL, 0, EINVAL);
+	if (ret) {
+		/* if this succeeds, tear down the io_uring instance
+		 * and start clean for the next test. */
+		close(fd);
+		fd = new_io_uring(1, &p);
+	}
+
+	/* IORING_REGISTER_BUFFERS */
+	status |= test_iovec_size(fd);
+	status |= test_iovec_nr(fd);
+	/* IORING_REGISTER_FILES */
+	status |= test_max_fds(fd);
+	close(fd);
+	/* uring poll on the uring fd */
+	status |= test_poll_ringfd();
+
+	if (!status)
+		printf("PASS\n");
+	else
+		printf("FAIL\n");
+
+	return status;
+}
diff --git a/test/io_uring_setup.c b/test/io_uring_setup.c
new file mode 100644
index 0000000..2b76402
--- /dev/null
+++ b/test/io_uring_setup.c
@@ -0,0 +1,161 @@
+/*
+ * io_uring_setup.c
+ *
+ * Description: Unit tests for the io_uring_setup system call.
+ *
+ * Copyright 2019, Red Hat, Inc.
+ * Author: Jeff Moyer <jmoyer@redhat.com>
+ */
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/sysinfo.h>
+#include "../src/liburing.h"
+
+/*
+ * Attempt the call with the given args.  Return 0 when expect matches
+ * the return value of the system call, 1 otherwise.
+ */
+char *
+flags_string(struct io_uring_params *p)
+{
+	static char flagstr[64];
+	int add_pipe = 0;
+
+	memset(flagstr, 0, sizeof(flagstr));
+
+	if (!p || p->flags == 0)
+		return "none";
+
+	/*
+	 * If unsupported flags are present, just print the bitmask.
+	 */
+	if (p->flags & ~(IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL |
+			 IORING_SETUP_SQ_AFF)) {
+		snprintf(flagstr, 64, "0x%.8x", p->flags);
+		return flagstr;
+	}
+
+	if (p->flags & IORING_SETUP_IOPOLL) {
+		strncat(flagstr, "IORING_SETUP_IOPOLL", 64 - strlen(flagstr));
+		add_pipe = 1;
+	}
+	if (p->flags & IORING_SETUP_SQPOLL) {
+		if (add_pipe)
+			strncat(flagstr, "|", 64 - strlen(flagstr));
+		strncat(flagstr, "IORING_SETUP_SQPOLL", 64 - strlen(flagstr));
+	}
+	if (p->flags & IORING_SETUP_SQ_AFF) {
+		if (add_pipe)
+			strncat(flagstr, "|", 64 - strlen(flagstr));
+		strncat(flagstr, "IORING_SETUP_SQ_AFF", 64 - strlen(flagstr));
+	}
+
+	return flagstr;
+}
+
+char *
+dump_resv(struct io_uring_params *p)
+{
+	static char resvstr[4096];
+
+	if (!p)
+		return "";
+
+	sprintf(resvstr, "0x%.8x 0x%.8x 0x%.8x 0x%.8x 0x%.8x", p->resv[0],
+		p->resv[1], p->resv[2], p->resv[3], p->resv[4]);
+
+	return resvstr;
+}
+
+/* bogus: setup returns a valid fd on success... expect can't predict the
+   fd we'll get, so this really only takes 1 parameter: error */
+int
+try_io_uring_setup(unsigned entries, struct io_uring_params *p, int expect, int error)
+{
+	int ret;
+
+	printf("io_uring_setup(%u, %p), flags: %s, resv: %s, sq_thread_cpu: %u\n",
+	       entries, p, flags_string(p), dump_resv(p),
+	       p ? p->sq_thread_cpu : 0);
+
+	ret = io_uring_setup(entries, p);
+	if (ret != expect) {
+		printf("expected %d, got %d\n", expect, ret);
+		/* if we got a valid uring, close it */
+		if (ret > 0)
+			close(ret);
+		return 1;
+	}
+	if (expect == -1 && error != errno) {
+		printf("expected errno %d, got %d\n", error, errno);
+		return 1;
+	}
+
+	return 0;
+}
+
+int
+main(int argc, char **argv)
+{
+	int fd;
+	unsigned int status = 0;
+	struct io_uring_params p;
+
+	memset(&p, 0, sizeof(p));
+	status |= try_io_uring_setup(0, &p, -1, EINVAL);
+	status |= try_io_uring_setup(1, NULL, -1, EFAULT);
+
+	/* resv array is non-zero */
+	memset(&p, 0, sizeof(p));
+	p.resv[0] = p.resv[1] = p.resv[2] = p.resv[3] = p.resv[4] = 1;
+	status |= try_io_uring_setup(1, &p, -1, EINVAL);
+
+	/* invalid flags */
+	memset(&p, 0, sizeof(p));
+	p.flags = ~0U;
+	status |= try_io_uring_setup(1, &p, -1, EINVAL);
+
+	/* IORING_SETUP_SQ_AFF set but not IORING_SETUP_SQPOLL */
+	memset(&p, 0, sizeof(p));
+	p.flags = IORING_SETUP_SQ_AFF;
+	status |= try_io_uring_setup(1, &p, -1, EINVAL);
+
+	/* attempt to bind to invalid cpu */
+	memset(&p, 0, sizeof(p));
+	p.flags = IORING_SETUP_SQPOLL | IORING_SETUP_SQ_AFF;
+	p.sq_thread_cpu = get_nprocs_conf();
+	status |= try_io_uring_setup(1, &p, -1, EINVAL);
+
+	/* I think we can limit a process to a set of cpus.  I assume
+	 * we shouldn't be able to setup a kernel thread outside of that.
+	 * try to do that. (task->cpus_allowed) */
+
+	/* read/write on io_uring_fd */
+	memset(&p, 0, sizeof(p));
+	fd = io_uring_setup(1, &p);
+	if (fd < 0) {
+		printf("io_uring_setup failed with %d, expected success\n",
+		       errno);
+		status = 1;
+	} else {
+		char buf[4096];
+		int ret;
+		ret = read(fd, buf, 4096);
+		if (ret >= 0) {
+			printf("read from io_uring fd succeeded.  expected fail\n");
+			status = 1;
+		}
+	}
+
+	if (!status) {
+		printf("PASS\n");
+		return 0;
+	}
+
+	printf("FAIL\n");
+	return -1;
+}