[v3,1/4] lib: Add tst_fd iterator

diff --git a/include/tst_fd.h b/include/tst_fd.h
new file mode 100644
index 000000000..2183ea068
--- /dev/null
+++ b/include/tst_fd.h
@@ -0,0 +1,61 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/*
+ * Copyright (C) 2023 Cyril Hrubis <chrubis@suse.cz>
+ */
+
+#ifndef TST_FD_H__
+#define TST_FD_H__
+
+enum tst_fd_type {
+	TST_FD_FILE,
+	TST_FD_PATH,
+	TST_FD_DIR,
+	TST_FD_DEV_ZERO,
+	TST_FD_PROC_MAPS,
+	TST_FD_PIPE_READ,
+	TST_FD_PIPE_WRITE,
+	TST_FD_UNIX_SOCK,
+	TST_FD_INET_SOCK,
+	TST_FD_EPOLL,
+	TST_FD_EVENTFD,
+	TST_FD_SIGNALFD,
+	TST_FD_TIMERFD,
+	TST_FD_PIDFD,
+	TST_FD_FANOTIFY,
+	TST_FD_INOTIFY,
+	TST_FD_USERFAULTFD,
+	TST_FD_PERF_EVENT,
+	TST_FD_IO_URING,
+	TST_FD_BPF_MAP,
+	TST_FD_FSOPEN,
+	TST_FD_FSPICK,
+	TST_FD_OPEN_TREE,
+	TST_FD_MEMFD,
+	TST_FD_MEMFD_SECRET,
+	TST_FD_MAX,
+};
+
+struct tst_fd {
+	enum tst_fd_type type;
+	int fd;
+	/* used by the library, do not touch! */
+	long priv;
+};
+
+#define TST_FD_INIT {.type = TST_FD_FILE, .fd = -1}
+
+/*
+ * Advances the iterator to the next fd type, returns zero at the end.
+ */
+int tst_fd_next(struct tst_fd *fd);
+
+#define TST_FD_FOREACH(fd) \
+	for (struct tst_fd fd = TST_FD_INIT; tst_fd_next(&fd); )
+
+/*
+ * Returns human readable name for the file descriptor type.
+ */
+const char *tst_fd_desc(struct tst_fd *fd);
+
+#endif /* TST_FD_H__ */
diff --git a/include/tst_test.h b/include/tst_test.h
index 0c3171e5b..fda696eeb 100644
--- a/include/tst_test.h
+++ b/include/tst_test.h
@@ -44,6 +44,7 @@ 
 #include "tst_taint.h"
 #include "tst_memutils.h"
 #include "tst_arch.h"
+#include "tst_fd.h"
 
 /*
  * Reports testcase result.
diff --git a/lib/tst_fd.c b/lib/tst_fd.c
new file mode 100644
index 000000000..b0d6fb1d6
--- /dev/null
+++ b/lib/tst_fd.c
@@ -0,0 +1,325 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/*
+ * Copyright (C) 2023 Cyril Hrubis <chrubis@suse.cz>
+ */
+
+#define TST_NO_DEFAULT_MAIN
+
+#include <sys/epoll.h>
+#include <sys/eventfd.h>
+#include <sys/signalfd.h>
+#include <sys/timerfd.h>
+#include <sys/fanotify.h>
+#include <sys/inotify.h>
+#include <linux/perf_event.h>
+
+#include "tst_test.h"
+#include "tst_safe_macros.h"
+
+#include "lapi/pidfd.h"
+#include "lapi/io_uring.h"
+#include "lapi/bpf.h"
+#include "lapi/fsmount.h"
+
+#include "tst_fd.h"
+
+struct tst_fd_desc {
+	void (*open_fd)(struct tst_fd *fd);
+	void (*destroy)(struct tst_fd *fd);
+	const char *desc;
+};
+
+static void open_file(struct tst_fd *fd)
+{
+	fd->fd = SAFE_OPEN("fd_file", O_RDWR | O_CREAT, 0666);
+	SAFE_UNLINK("fd_file");
+}
+
+static void open_path(struct tst_fd *fd)
+{
+	int tfd;
+
+	tfd = SAFE_CREAT("fd_file", 0666);
+	SAFE_CLOSE(tfd);
+
+	fd->fd = SAFE_OPEN("fd_file", O_PATH);
+
+	SAFE_UNLINK("fd_file");
+}
+
+static void open_dir(struct tst_fd *fd)
+{
+	SAFE_MKDIR("fd_dir", 0700);
+	fd->fd = SAFE_OPEN("fd_dir", O_DIRECTORY);
+	SAFE_RMDIR("fd_dir");
+}
+
+static void open_dev_zero(struct tst_fd *fd)
+{
+	fd->fd = SAFE_OPEN("/dev/zero", O_RDONLY);
+}
+
+static void open_proc_self_maps(struct tst_fd *fd)
+{
+	fd->fd = SAFE_OPEN("/proc/self/maps", O_RDONLY);
+}
+
+static void open_pipe_read(struct tst_fd *fd)
+{
+	int pipe[2];
+
+	SAFE_PIPE(pipe);
+	fd->fd = pipe[0];
+	fd->priv = pipe[1];
+}
+
+static void open_pipe_write(struct tst_fd *fd)
+{
+	int pipe[2];
+
+	SAFE_PIPE(pipe);
+	fd->fd = pipe[1];
+	fd->priv = pipe[0];
+}
+
+static void destroy_pipe(struct tst_fd *fd)
+{
+	SAFE_CLOSE(fd->priv);
+}
+
+static void open_unix_sock(struct tst_fd *fd)
+{
+	fd->fd = SAFE_SOCKET(AF_UNIX, SOCK_STREAM, 0);
+}
+
+static void open_inet_sock(struct tst_fd *fd)
+{
+	fd->fd = SAFE_SOCKET(AF_INET, SOCK_STREAM, 0);
+}
+
+static void open_epoll(struct tst_fd *fd)
+{
+	fd->fd = epoll_create(1);
+
+	if (fd->fd < 0)
+		tst_brk(TBROK | TERRNO, "epoll_create()");
+}
+
+static void open_eventfd(struct tst_fd *fd)
+{
+	fd->fd = eventfd(0, 0);
+
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_signalfd(struct tst_fd *fd)
+{
+	sigset_t sfd_mask;
+	sigemptyset(&sfd_mask);
+
+	fd->fd = signalfd(-1, &sfd_mask, 0);
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_timerfd(struct tst_fd *fd)
+{
+	fd->fd = timerfd_create(CLOCK_REALTIME, 0);
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_pidfd(struct tst_fd *fd)
+{
+	fd->fd = pidfd_open(getpid(), 0);
+	if (fd->fd < 0)
+		tst_brk(TBROK | TERRNO, "pidfd_open()");
+}
+
+static void open_fanotify(struct tst_fd *fd)
+{
+	fd->fd = fanotify_init(FAN_CLASS_NOTIF, O_RDONLY);
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_inotify(struct tst_fd *fd)
+{
+	fd->fd = inotify_init();
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_userfaultfd(struct tst_fd *fd)
+{
+	fd->fd = syscall(__NR_userfaultfd, 0);
+
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_perf_event(struct tst_fd *fd)
+{
+	struct perf_event_attr pe_attr = {
+		.type = PERF_TYPE_SOFTWARE,
+		.size = sizeof(struct perf_event_attr),
+		.config = PERF_COUNT_SW_CPU_CLOCK,
+		.disabled = 1,
+		.exclude_kernel = 1,
+		.exclude_hv = 1,
+	};
+
+	fd->fd = syscall(__NR_perf_event_open, &pe_attr, 0, -1, -1, 0);
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_io_uring(struct tst_fd *fd)
+{
+	struct io_uring_params uring_params = {};
+
+	fd->fd = io_uring_setup(1, &uring_params);
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_bpf_map(struct tst_fd *fd)
+{
+	union bpf_attr array_attr = {
+		.map_type = BPF_MAP_TYPE_ARRAY,
+		.key_size = 4,
+		.value_size = 8,
+		.max_entries = 1,
+	};
+
+	fd->fd = bpf(BPF_MAP_CREATE, &array_attr, sizeof(array_attr));
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_fsopen(struct tst_fd *fd)
+{
+	fd->fd = fsopen("ext2", 0);
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_fspick(struct tst_fd *fd)
+{
+	fd->fd = fspick(AT_FDCWD, "/", 0);
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_open_tree(struct tst_fd *fd)
+{
+	fd->fd = open_tree(AT_FDCWD, "/", 0);
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_memfd(struct tst_fd *fd)
+{
+	fd->fd = syscall(__NR_memfd_create, "ltp_memfd", 0);
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static void open_memfd_secret(struct tst_fd *fd)
+{
+	fd->fd = syscall(__NR_memfd_secret, 0);
+	if (fd->fd < 0) {
+		tst_res(TCONF | TERRNO,
+			"Skipping %s", tst_fd_desc(fd));
+	}
+}
+
+static struct tst_fd_desc fd_desc[] = {
+	[TST_FD_FILE] = {.open_fd = open_file, .desc = "file"},
+	[TST_FD_PATH] = {.open_fd = open_path, .desc = "O_PATH file"},
+	[TST_FD_DIR] = {.open_fd = open_dir, .desc = "directory"},
+	[TST_FD_DEV_ZERO] = {.open_fd = open_dev_zero, .desc = "/dev/zero"},
+	[TST_FD_PROC_MAPS] = {.open_fd = open_proc_self_maps, .desc = "/proc/self/maps"},
+	[TST_FD_PIPE_READ] = {.open_fd = open_pipe_read, .desc = "pipe read end", .destroy = destroy_pipe},
+	[TST_FD_PIPE_WRITE] = {.open_fd = open_pipe_write, .desc = "pipe write end", .destroy = destroy_pipe},
+	[TST_FD_UNIX_SOCK] = {.open_fd = open_unix_sock, .desc = "unix socket"},
+	[TST_FD_INET_SOCK] = {.open_fd = open_inet_sock, .desc = "inet socket"},
+	[TST_FD_EPOLL] = {.open_fd = open_epoll, .desc = "epoll"},
+	[TST_FD_EVENTFD] = {.open_fd = open_eventfd, .desc = "eventfd"},
+	[TST_FD_SIGNALFD] = {.open_fd = open_signalfd, .desc = "signalfd"},
+	[TST_FD_TIMERFD] = {.open_fd = open_timerfd, .desc = "timerfd"},
+	[TST_FD_PIDFD] = {.open_fd = open_pidfd, .desc = "pidfd"},
+	[TST_FD_FANOTIFY] = {.open_fd = open_fanotify, .desc = "fanotify"},
+	[TST_FD_INOTIFY] = {.open_fd = open_inotify, .desc = "inotify"},
+	[TST_FD_USERFAULTFD] = {.open_fd = open_userfaultfd, .desc = "userfaultfd"},
+	[TST_FD_PERF_EVENT] = {.open_fd = open_perf_event, .desc = "perf event"},
+	[TST_FD_IO_URING] = {.open_fd = open_io_uring, .desc = "io uring"},
+	[TST_FD_BPF_MAP] = {.open_fd = open_bpf_map, .desc = "bpf map"},
+	[TST_FD_FSOPEN] = {.open_fd = open_fsopen, .desc = "fsopen"},
+	[TST_FD_FSPICK] = {.open_fd = open_fspick, .desc = "fspick"},
+	[TST_FD_OPEN_TREE] = {.open_fd = open_open_tree, .desc = "open_tree"},
+	[TST_FD_MEMFD] = {.open_fd = open_memfd, .desc = "memfd"},
+	[TST_FD_MEMFD_SECRET] = {.open_fd = open_memfd_secret, .desc = "memfd secret"},
+};
+
+const char *tst_fd_desc(struct tst_fd *fd)
+{
+	if (fd->type >= ARRAY_SIZE(fd_desc))
+		return "invalid";
+
+	return fd_desc[fd->type].desc;
+}
+
+int tst_fd_next(struct tst_fd *fd)
+{
+	size_t len = ARRAY_SIZE(fd_desc);
+
+	if (fd->fd >= 0) {
+		SAFE_CLOSE(fd->fd);
+
+		if (fd_desc[fd->type].destroy)
+			fd_desc[fd->type].destroy(fd);
+
+		fd->type++;
+	}
+
+	for (;;) {
+		if (fd->type >= len)
+			return 0;
+
+		fd_desc[fd->type].open_fd(fd);
+
+		if (fd->fd >= 0)
+			return 1;
+
+		fd->type++;
+	}
+}