1 files changed, 268 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_obj_pinning.c b/tools/testing/selftests/bpf/prog_tests/bpf_obj_pinning.c
new file mode 100644
index 000000000000..31f1e815f671
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_obj_pinning.c
@@ -0,0 +1,268 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+#define _GNU_SOURCE
+#include <test_progs.h>
+#include <bpf/btf.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <linux/unistd.h>
+#include <linux/mount.h>
+#include <sys/syscall.h>
+
+static inline int sys_fsopen(const char *fsname, unsigned flags)
+{
+	return syscall(__NR_fsopen, fsname, flags);
+}
+
+static inline int sys_fsconfig(int fs_fd, unsigned cmd, const char *key, const void *val, int aux)
+{
+	return syscall(__NR_fsconfig, fs_fd, cmd, key, val, aux);
+}
+
+static inline int sys_fsmount(int fs_fd, unsigned flags, unsigned ms_flags)
+{
+	return syscall(__NR_fsmount, fs_fd, flags, ms_flags);
+}
+
+__attribute__((unused))
+static inline int sys_move_mount(int from_dfd, const char *from_path,
+			         int to_dfd, const char *to_path,
+			         unsigned int ms_flags)
+{
+	return syscall(__NR_move_mount, from_dfd, from_path, to_dfd, to_path, ms_flags);
+}
+
+static void bpf_obj_pinning_detached(void)
+{
+	LIBBPF_OPTS(bpf_obj_pin_opts, pin_opts);
+	LIBBPF_OPTS(bpf_obj_get_opts, get_opts);
+	int fs_fd = -1, mnt_fd = -1;
+	int map_fd = -1, map_fd2 = -1;
+	int zero = 0, src_value, dst_value, err;
+	const char *map_name = "fsmount_map";
+
+	/* A bunch of below UAPI calls are constructed based on reading:
+	 * https://brauner.io/2023/02/28/mounting-into-mount-namespaces.html
+	 */
+
+	/* create VFS context */
+	fs_fd = sys_fsopen("bpf", 0);
+	if (!ASSERT_GE(fs_fd, 0, "fs_fd"))
+		goto cleanup;
+
+	/* instantiate FS object */
+	err = sys_fsconfig(fs_fd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
+	if (!ASSERT_OK(err, "fs_create"))
+		goto cleanup;
+
+	/* create O_PATH fd for detached mount */
+	mnt_fd = sys_fsmount(fs_fd, 0, 0);
+	if (!ASSERT_GE(mnt_fd, 0, "mnt_fd"))
+		goto cleanup;
+
+	/* If we wanted to expose detached mount in the file system, we'd do
+	 * something like below. But the whole point is that we actually don't
+	 * even have to expose BPF FS in the file system to be able to work
+	 * (pin/get objects) with it.
+	 *
+	 * err = sys_move_mount(mnt_fd, "", -EBADF, mnt_path, MOVE_MOUNT_F_EMPTY_PATH);
+	 * if (!ASSERT_OK(err, "move_mount"))
+	 *	goto cleanup;
+	 */
+
+	/* create BPF map to pin */
+	map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, map_name, 4, 4, 1, NULL);
+	if (!ASSERT_GE(map_fd, 0, "map_fd"))
+		goto cleanup;
+
+	/* pin BPF map into detached BPF FS through mnt_fd */
+	pin_opts.file_flags = BPF_F_PATH_FD;
+	pin_opts.path_fd = mnt_fd;
+	err = bpf_obj_pin_opts(map_fd, map_name, &pin_opts);
+	if (!ASSERT_OK(err, "map_pin"))
+		goto cleanup;
+
+	/* get BPF map from detached BPF FS through mnt_fd */
+	get_opts.file_flags = BPF_F_PATH_FD;
+	get_opts.path_fd = mnt_fd;
+	map_fd2 = bpf_obj_get_opts(map_name, &get_opts);
+	if (!ASSERT_GE(map_fd2, 0, "map_get"))
+		goto cleanup;
+
+	/* update map through one FD */
+	src_value = 0xcafebeef;
+	err = bpf_map_update_elem(map_fd, &zero, &src_value, 0);
+	ASSERT_OK(err, "map_update");
+
+	/* check values written/read through different FDs do match */
+	dst_value = 0;
+	err = bpf_map_lookup_elem(map_fd2, &zero, &dst_value);
+	ASSERT_OK(err, "map_lookup");
+	ASSERT_EQ(dst_value, src_value, "map_value_eq1");
+	ASSERT_EQ(dst_value, 0xcafebeef, "map_value_eq2");
+
+cleanup:
+	if (map_fd >= 0)
+		ASSERT_OK(close(map_fd), "close_map_fd");
+	if (map_fd2 >= 0)
+		ASSERT_OK(close(map_fd2), "close_map_fd2");
+	if (fs_fd >= 0)
+		ASSERT_OK(close(fs_fd), "close_fs_fd");
+	if (mnt_fd >= 0)
+		ASSERT_OK(close(mnt_fd), "close_mnt_fd");
+}
+
+enum path_kind
+{
+	PATH_STR_ABS,
+	PATH_STR_REL,
+	PATH_FD_REL,
+};
+
+static void validate_pin(int map_fd, const char *map_name, int src_value,
+			 enum path_kind path_kind)
+{
+	LIBBPF_OPTS(bpf_obj_pin_opts, pin_opts);
+	char abs_path[PATH_MAX], old_cwd[PATH_MAX];
+	const char *pin_path = NULL;
+	int zero = 0, dst_value, map_fd2, err;
+
+	snprintf(abs_path, sizeof(abs_path), "/sys/fs/bpf/%s", map_name);
+	old_cwd[0] = '\0';
+
+	switch (path_kind) {
+	case PATH_STR_ABS:
+		/* absolute path */
+		pin_path = abs_path;
+		break;
+	case PATH_STR_REL:
+		/* cwd + relative path */
+		ASSERT_OK_PTR(getcwd(old_cwd, sizeof(old_cwd)), "getcwd");
+		ASSERT_OK(chdir("/sys/fs/bpf"), "chdir");
+		pin_path = map_name;
+		break;
+	case PATH_FD_REL:
+		/* dir fd + relative path */
+		pin_opts.file_flags = BPF_F_PATH_FD;
+		pin_opts.path_fd = open("/sys/fs/bpf", O_PATH);
+		ASSERT_GE(pin_opts.path_fd, 0, "path_fd");
+		pin_path = map_name;
+		break;
+	}
+
+	/* pin BPF map using specified path definition */
+	err = bpf_obj_pin_opts(map_fd, pin_path, &pin_opts);
+	ASSERT_OK(err, "obj_pin");
+
+	/* cleanup */
+	if (pin_opts.path_fd >= 0)
+		close(pin_opts.path_fd);
+	if (old_cwd[0])
+		ASSERT_OK(chdir(old_cwd), "restore_cwd");
+
+	map_fd2 = bpf_obj_get(abs_path);
+	if (!ASSERT_GE(map_fd2, 0, "map_get"))
+		goto cleanup;
+
+	/* update map through one FD */
+	err = bpf_map_update_elem(map_fd, &zero, &src_value, 0);
+	ASSERT_OK(err, "map_update");
+
+	/* check values written/read through different FDs do match */
+	dst_value = 0;
+	err = bpf_map_lookup_elem(map_fd2, &zero, &dst_value);
+	ASSERT_OK(err, "map_lookup");
+	ASSERT_EQ(dst_value, src_value, "map_value_eq");
+cleanup:
+	if (map_fd2 >= 0)
+		ASSERT_OK(close(map_fd2), "close_map_fd2");
+	unlink(abs_path);
+}
+
+static void validate_get(int map_fd, const char *map_name, int src_value,
+			 enum path_kind path_kind)
+{
+	LIBBPF_OPTS(bpf_obj_get_opts, get_opts);
+	char abs_path[PATH_MAX], old_cwd[PATH_MAX];
+	const char *pin_path = NULL;
+	int zero = 0, dst_value, map_fd2, err;
+
+	snprintf(abs_path, sizeof(abs_path), "/sys/fs/bpf/%s", map_name);
+	/* pin BPF map using specified path definition */
+	err = bpf_obj_pin(map_fd, abs_path);
+	if (!ASSERT_OK(err, "pin_map"))
+		return;
+
+	old_cwd[0] = '\0';
+
+	switch (path_kind) {
+	case PATH_STR_ABS:
+		/* absolute path */
+		pin_path = abs_path;
+		break;
+	case PATH_STR_REL:
+		/* cwd + relative path */
+		ASSERT_OK_PTR(getcwd(old_cwd, sizeof(old_cwd)), "getcwd");
+		ASSERT_OK(chdir("/sys/fs/bpf"), "chdir");
+		pin_path = map_name;
+		break;
+	case PATH_FD_REL:
+		/* dir fd + relative path */
+		get_opts.file_flags = BPF_F_PATH_FD;
+		get_opts.path_fd = open("/sys/fs/bpf", O_PATH);
+		ASSERT_GE(get_opts.path_fd, 0, "path_fd");
+		pin_path = map_name;
+		break;
+	}
+
+	map_fd2 = bpf_obj_get_opts(pin_path, &get_opts);
+	if (!ASSERT_GE(map_fd2, 0, "map_get"))
+		goto cleanup;
+
+	/* cleanup */
+	if (get_opts.path_fd >= 0)
+		close(get_opts.path_fd);
+	if (old_cwd[0])
+		ASSERT_OK(chdir(old_cwd), "restore_cwd");
+
+	/* update map through one FD */
+	err = bpf_map_update_elem(map_fd, &zero, &src_value, 0);
+	ASSERT_OK(err, "map_update");
+
+	/* check values written/read through different FDs do match */
+	dst_value = 0;
+	err = bpf_map_lookup_elem(map_fd2, &zero, &dst_value);
+	ASSERT_OK(err, "map_lookup");
+	ASSERT_EQ(dst_value, src_value, "map_value_eq");
+cleanup:
+	if (map_fd2 >= 0)
+		ASSERT_OK(close(map_fd2), "close_map_fd2");
+	unlink(abs_path);
+}
+
+static void bpf_obj_pinning_mounted(enum path_kind path_kind)
+{
+	const char *map_name = "mounted_map";
+	int map_fd;
+
+	/* create BPF map to pin */
+	map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, map_name, 4, 4, 1, NULL);
+	if (!ASSERT_GE(map_fd, 0, "map_fd"))
+		return;
+
+	validate_pin(map_fd, map_name, 100 + (int)path_kind, path_kind);
+	validate_get(map_fd, map_name, 200 + (int)path_kind, path_kind);
+	ASSERT_OK(close(map_fd), "close_map_fd");
+}
+
+void test_bpf_obj_pinning()
+{
+	if (test__start_subtest("detached"))
+		bpf_obj_pinning_detached();
+	if (test__start_subtest("mounted-str-abs"))
+		bpf_obj_pinning_mounted(PATH_STR_ABS);
+	if (test__start_subtest("mounted-str-rel"))
+		bpf_obj_pinning_mounted(PATH_STR_REL);
+	if (test__start_subtest("mounted-fd-rel"))
+		bpf_obj_pinning_mounted(PATH_FD_REL);
+}