1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
3 #define _GNU_SOURCE
4 #include <test_progs.h>
5 #include <bpf/btf.h>
6 #include <fcntl.h>
7 #include <unistd.h>
8 #include <linux/unistd.h>
9 #include <linux/mount.h>
10 #include <sys/syscall.h>
11 #include "bpf/libbpf_internal.h"
12
13 static inline int sys_fsopen(const char *fsname, unsigned flags)
14 {
15 return syscall(__NR_fsopen, fsname, flags);
16 }
17
18 static inline int sys_fsconfig(int fs_fd, unsigned cmd, const char *key, const void *val, int aux)
19 {
20 return syscall(__NR_fsconfig, fs_fd, cmd, key, val, aux);
21 }
22
23 static inline int sys_fsmount(int fs_fd, unsigned flags, unsigned ms_flags)
24 {
25 return syscall(__NR_fsmount, fs_fd, flags, ms_flags);
26 }
27
28 __attribute__((unused))
29 static inline int sys_move_mount(int from_dfd, const char *from_path,
30 int to_dfd, const char *to_path,
31 unsigned int ms_flags)
32 {
33 return syscall(__NR_move_mount, from_dfd, from_path, to_dfd, to_path, ms_flags);
34 }
35
36 static void bpf_obj_pinning_detached(void)
37 {
38 LIBBPF_OPTS(bpf_obj_pin_opts, pin_opts);
39 LIBBPF_OPTS(bpf_obj_get_opts, get_opts);
40 int fs_fd = -1, mnt_fd = -1;
41 int map_fd = -1, map_fd2 = -1;
42 int zero = 0, src_value, dst_value, err;
43 const char *map_name = "fsmount_map";
44
45 /* A bunch of below UAPI calls are constructed based on reading:
46 * https://brauner.io/2023/02/28/mounting-into-mount-namespaces.html
47 */
48
49 /* create VFS context */
50 fs_fd = sys_fsopen("bpf", 0);
51 if (!ASSERT_GE(fs_fd, 0, "fs_fd"))
52 goto cleanup;
53
54 /* instantiate FS object */
55 err = sys_fsconfig(fs_fd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
56 if (!ASSERT_OK(err, "fs_create"))
57 goto cleanup;
58
59 /* create O_PATH fd for detached mount */
60 mnt_fd = sys_fsmount(fs_fd, 0, 0);
61 if (!ASSERT_GE(mnt_fd, 0, "mnt_fd"))
62 goto cleanup;
63
64 /* If we wanted to expose detached mount in the file system, we'd do
65 * something like below. But the whole point is that we actually don't
66 * even have to expose BPF FS in the file system to be able to work
67 * (pin/get objects) with it.
68 *
69 * err = sys_move_mount(mnt_fd, "", -EBADF, mnt_path, MOVE_MOUNT_F_EMPTY_PATH);
70 * if (!ASSERT_OK(err, "move_mount"))
71 * goto cleanup;
72 */
73
74 /* create BPF map to pin */
75 map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, map_name, 4, 4, 1, NULL);
76 if (!ASSERT_GE(map_fd, 0, "map_fd"))
77 goto cleanup;
78
79 /* pin BPF map into detached BPF FS through mnt_fd */
80 pin_opts.file_flags = BPF_F_PATH_FD;
81 pin_opts.path_fd = mnt_fd;
82 err = bpf_obj_pin_opts(map_fd, map_name, &pin_opts);
83 if (!ASSERT_OK(err, "map_pin"))
84 goto cleanup;
85
86 /* get BPF map from detached BPF FS through mnt_fd */
87 get_opts.file_flags = BPF_F_PATH_FD;
88 get_opts.path_fd = mnt_fd;
89 map_fd2 = bpf_obj_get_opts(map_name, &get_opts);
90 if (!ASSERT_GE(map_fd2, 0, "map_get"))
91 goto cleanup;
92
93 /* update map through one FD */
94 src_value = 0xcafebeef;
95 err = bpf_map_update_elem(map_fd, &zero, &src_value, 0);
96 ASSERT_OK(err, "map_update");
97
98 /* check values written/read through different FDs do match */
99 dst_value = 0;
100 err = bpf_map_lookup_elem(map_fd2, &zero, &dst_value);
101 ASSERT_OK(err, "map_lookup");
102 ASSERT_EQ(dst_value, src_value, "map_value_eq1");
103 ASSERT_EQ(dst_value, 0xcafebeef, "map_value_eq2");
104
105 cleanup:
106 if (map_fd >= 0)
107 ASSERT_OK(close(map_fd), "close_map_fd");
108 if (map_fd2 >= 0)
109 ASSERT_OK(close(map_fd2), "close_map_fd2");
110 if (fs_fd >= 0)
111 ASSERT_OK(close(fs_fd), "close_fs_fd");
112 if (mnt_fd >= 0)
113 ASSERT_OK(close(mnt_fd), "close_mnt_fd");
114 }
115
116 enum path_kind
117 {
118 PATH_STR_ABS,
119 PATH_STR_REL,
120 PATH_FD_REL,
121 };
122
123 static void validate_pin(int map_fd, const char *map_name, int src_value,
124 enum path_kind path_kind)
125 {
126 LIBBPF_OPTS(bpf_obj_pin_opts, pin_opts);
127 char abs_path[PATH_MAX], old_cwd[PATH_MAX];
128 const char *pin_path = NULL;
129 int zero = 0, dst_value, map_fd2, err;
130
131 snprintf(abs_path, sizeof(abs_path), "/sys/fs/bpf/%s", map_name);
132 old_cwd[0] = '\0';
133
134 switch (path_kind) {
135 case PATH_STR_ABS:
136 /* absolute path */
137 pin_path = abs_path;
138 break;
139 case PATH_STR_REL:
140 /* cwd + relative path */
141 ASSERT_OK_PTR(getcwd(old_cwd, sizeof(old_cwd)), "getcwd");
142 ASSERT_OK(chdir("/sys/fs/bpf"), "chdir");
143 pin_path = map_name;
144 break;
145 case PATH_FD_REL:
146 /* dir fd + relative path */
147 pin_opts.file_flags = BPF_F_PATH_FD;
148 pin_opts.path_fd = open("/sys/fs/bpf", O_PATH);
149 ASSERT_GE(pin_opts.path_fd, 0, "path_fd");
150 pin_path = map_name;
151 break;
152 }
153
154 /* pin BPF map using specified path definition */
155 err = bpf_obj_pin_opts(map_fd, pin_path, &pin_opts);
156 ASSERT_OK(err, "obj_pin");
157
158 /* cleanup */
159 if (path_kind == PATH_FD_REL && pin_opts.path_fd >= 0)
160 close(pin_opts.path_fd);
161 if (old_cwd[0])
162 ASSERT_OK(chdir(old_cwd), "restore_cwd");
163
164 map_fd2 = bpf_obj_get(abs_path);
165 if (!ASSERT_GE(map_fd2, 0, "map_get"))
166 goto cleanup;
167
168 /* update map through one FD */
169 err = bpf_map_update_elem(map_fd, &zero, &src_value, 0);
170 ASSERT_OK(err, "map_update");
171
172 /* check values written/read through different FDs do match */
173 dst_value = 0;
174 err = bpf_map_lookup_elem(map_fd2, &zero, &dst_value);
175 ASSERT_OK(err, "map_lookup");
176 ASSERT_EQ(dst_value, src_value, "map_value_eq");
177 cleanup:
178 if (map_fd2 >= 0)
179 ASSERT_OK(close(map_fd2), "close_map_fd2");
180 unlink(abs_path);
181 }
182
183 static void validate_get(int map_fd, const char *map_name, int src_value,
184 enum path_kind path_kind)
185 {
186 LIBBPF_OPTS(bpf_obj_get_opts, get_opts);
187 char abs_path[PATH_MAX], old_cwd[PATH_MAX];
188 const char *pin_path = NULL;
189 int zero = 0, dst_value, map_fd2, err;
190
191 snprintf(abs_path, sizeof(abs_path), "/sys/fs/bpf/%s", map_name);
192 /* pin BPF map using specified path definition */
193 err = bpf_obj_pin(map_fd, abs_path);
194 if (!ASSERT_OK(err, "pin_map"))
195 return;
196
197 old_cwd[0] = '\0';
198
199 switch (path_kind) {
200 case PATH_STR_ABS:
201 /* absolute path */
202 pin_path = abs_path;
203 break;
204 case PATH_STR_REL:
205 /* cwd + relative path */
206 ASSERT_OK_PTR(getcwd(old_cwd, sizeof(old_cwd)), "getcwd");
207 ASSERT_OK(chdir("/sys/fs/bpf"), "chdir");
208 pin_path = map_name;
209 break;
210 case PATH_FD_REL:
211 /* dir fd + relative path */
212 get_opts.file_flags = BPF_F_PATH_FD;
213 get_opts.path_fd = open("/sys/fs/bpf", O_PATH);
214 ASSERT_GE(get_opts.path_fd, 0, "path_fd");
215 pin_path = map_name;
216 break;
217 }
218
219 map_fd2 = bpf_obj_get_opts(pin_path, &get_opts);
220 if (!ASSERT_GE(map_fd2, 0, "map_get"))
221 goto cleanup;
222
223 /* cleanup */
224 if (path_kind == PATH_FD_REL && get_opts.path_fd >= 0)
225 close(get_opts.path_fd);
226 if (old_cwd[0])
227 ASSERT_OK(chdir(old_cwd), "restore_cwd");
228
229 /* update map through one FD */
230 err = bpf_map_update_elem(map_fd, &zero, &src_value, 0);
231 ASSERT_OK(err, "map_update");
232
233 /* check values written/read through different FDs do match */
234 dst_value = 0;
235 err = bpf_map_lookup_elem(map_fd2, &zero, &dst_value);
236 ASSERT_OK(err, "map_lookup");
237 ASSERT_EQ(dst_value, src_value, "map_value_eq");
238 cleanup:
239 if (map_fd2 >= 0)
240 ASSERT_OK(close(map_fd2), "close_map_fd2");
241 unlink(abs_path);
242 }
243
244 static void bpf_obj_pinning_mounted(enum path_kind path_kind)
245 {
246 const char *map_name = "mounted_map";
247 int map_fd;
248
249 /* create BPF map to pin */
250 map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, map_name, 4, 4, 1, NULL);
251 if (!ASSERT_GE(map_fd, 0, "map_fd"))
252 return;
253
254 validate_pin(map_fd, map_name, 100 + (int)path_kind, path_kind);
255 validate_get(map_fd, map_name, 200 + (int)path_kind, path_kind);
256 ASSERT_OK(close(map_fd), "close_map_fd");
257 }
258
259 void test_bpf_obj_pinning()
260 {
261 if (test__start_subtest("detached"))
262 bpf_obj_pinning_detached();
263 if (test__start_subtest("mounted-str-abs"))
264 bpf_obj_pinning_mounted(PATH_STR_ABS);
265 if (test__start_subtest("mounted-str-rel"))
266 bpf_obj_pinning_mounted(PATH_STR_REL);
267 if (test__start_subtest("mounted-fd-rel"))
268 bpf_obj_pinning_mounted(PATH_FD_REL);
269 }
270
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.