xref: /linux/tools/perf/util/namespaces.c (revision 8e07e0e3964ca4e23ce7b68e2096fe660a888942) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *
4  * Copyright (C) 2017 Hari Bathini, IBM Corporation
5  */
6 
7 #include "namespaces.h"
8 #include "event.h"
9 #include "get_current_dir_name.h"
10 #include <sys/types.h>
11 #include <sys/stat.h>
12 #include <fcntl.h>
13 #include <limits.h>
14 #include <sched.h>
15 #include <stdlib.h>
16 #include <stdio.h>
17 #include <string.h>
18 #include <unistd.h>
19 #include <asm/bug.h>
20 #include <linux/kernel.h>
21 #include <linux/zalloc.h>
22 
23 static const char *perf_ns__names[] = {
24 	[NET_NS_INDEX]		= "net",
25 	[UTS_NS_INDEX]		= "uts",
26 	[IPC_NS_INDEX]		= "ipc",
27 	[PID_NS_INDEX]		= "pid",
28 	[USER_NS_INDEX]		= "user",
29 	[MNT_NS_INDEX]		= "mnt",
30 	[CGROUP_NS_INDEX]	= "cgroup",
31 };
32 
33 const char *perf_ns__name(unsigned int id)
34 {
35 	if (id >= ARRAY_SIZE(perf_ns__names))
36 		return "UNKNOWN";
37 	return perf_ns__names[id];
38 }
39 
40 struct namespaces *namespaces__new(struct perf_record_namespaces *event)
41 {
42 	struct namespaces *namespaces;
43 	u64 link_info_size = ((event ? event->nr_namespaces : NR_NAMESPACES) *
44 			      sizeof(struct perf_ns_link_info));
45 
46 	namespaces = zalloc(sizeof(struct namespaces) + link_info_size);
47 	if (!namespaces)
48 		return NULL;
49 
50 	namespaces->end_time = -1;
51 
52 	if (event)
53 		memcpy(namespaces->link_info, event->link_info, link_info_size);
54 
55 	return namespaces;
56 }
57 
58 void namespaces__free(struct namespaces *namespaces)
59 {
60 	free(namespaces);
61 }
62 
63 static int nsinfo__get_nspid(pid_t *tgid, pid_t *nstgid, bool *in_pidns, const char *path)
64 {
65 	FILE *f = NULL;
66 	char *statln = NULL;
67 	size_t linesz = 0;
68 	char *nspid;
69 
70 	f = fopen(path, "r");
71 	if (f == NULL)
72 		return -1;
73 
74 	while (getline(&statln, &linesz, f) != -1) {
75 		/* Use tgid if CONFIG_PID_NS is not defined. */
76 		if (strstr(statln, "Tgid:") != NULL) {
77 			*tgid = (pid_t)strtol(strrchr(statln, '\t'), NULL, 10);
78 			*nstgid = *tgid;
79 		}
80 
81 		if (strstr(statln, "NStgid:") != NULL) {
82 			nspid = strrchr(statln, '\t');
83 			*nstgid = (pid_t)strtol(nspid, NULL, 10);
84 			/*
85 			 * If innermost tgid is not the first, process is in a different
86 			 * PID namespace.
87 			 */
88 			*in_pidns = (statln + sizeof("NStgid:") - 1) != nspid;
89 			break;
90 		}
91 	}
92 
93 	fclose(f);
94 	free(statln);
95 	return 0;
96 }
97 
98 int nsinfo__init(struct nsinfo *nsi)
99 {
100 	char oldns[PATH_MAX];
101 	char spath[PATH_MAX];
102 	char *newns = NULL;
103 	struct stat old_stat;
104 	struct stat new_stat;
105 	int rv = -1;
106 
107 	if (snprintf(oldns, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
108 		return rv;
109 
110 	if (asprintf(&newns, "/proc/%d/ns/mnt", nsinfo__pid(nsi)) == -1)
111 		return rv;
112 
113 	if (stat(oldns, &old_stat) < 0)
114 		goto out;
115 
116 	if (stat(newns, &new_stat) < 0)
117 		goto out;
118 
119 	/* Check if the mount namespaces differ, if so then indicate that we
120 	 * want to switch as part of looking up dso/map data.
121 	 */
122 	if (old_stat.st_ino != new_stat.st_ino) {
123 		RC_CHK_ACCESS(nsi)->need_setns = true;
124 		RC_CHK_ACCESS(nsi)->mntns_path = newns;
125 		newns = NULL;
126 	}
127 
128 	/* If we're dealing with a process that is in a different PID namespace,
129 	 * attempt to work out the innermost tgid for the process.
130 	 */
131 	if (snprintf(spath, PATH_MAX, "/proc/%d/status", nsinfo__pid(nsi)) >= PATH_MAX)
132 		goto out;
133 
134 	rv = nsinfo__get_nspid(&RC_CHK_ACCESS(nsi)->tgid, &RC_CHK_ACCESS(nsi)->nstgid,
135 			       &RC_CHK_ACCESS(nsi)->in_pidns, spath);
136 
137 out:
138 	free(newns);
139 	return rv;
140 }
141 
142 static struct nsinfo *nsinfo__alloc(void)
143 {
144 	struct nsinfo *res;
145 	RC_STRUCT(nsinfo) *nsi;
146 
147 	nsi = calloc(1, sizeof(*nsi));
148 	if (ADD_RC_CHK(res, nsi))
149 		refcount_set(&nsi->refcnt, 1);
150 
151 	return res;
152 }
153 
154 struct nsinfo *nsinfo__new(pid_t pid)
155 {
156 	struct nsinfo *nsi;
157 
158 	if (pid == 0)
159 		return NULL;
160 
161 	nsi = nsinfo__alloc();
162 	if (!nsi)
163 		return NULL;
164 
165 	RC_CHK_ACCESS(nsi)->pid = pid;
166 	RC_CHK_ACCESS(nsi)->tgid = pid;
167 	RC_CHK_ACCESS(nsi)->nstgid = pid;
168 	nsinfo__clear_need_setns(nsi);
169 	RC_CHK_ACCESS(nsi)->in_pidns = false;
170 	/* Init may fail if the process exits while we're trying to look at its
171 	 * proc information. In that case, save the pid but don't try to enter
172 	 * the namespace.
173 	 */
174 	if (nsinfo__init(nsi) == -1)
175 		nsinfo__clear_need_setns(nsi);
176 
177 	return nsi;
178 }
179 
180 static const char *nsinfo__mntns_path(const struct nsinfo *nsi)
181 {
182 	return RC_CHK_ACCESS(nsi)->mntns_path;
183 }
184 
185 struct nsinfo *nsinfo__copy(const struct nsinfo *nsi)
186 {
187 	struct nsinfo *nnsi;
188 
189 	if (nsi == NULL)
190 		return NULL;
191 
192 	nnsi = nsinfo__alloc();
193 	if (!nnsi)
194 		return NULL;
195 
196 	RC_CHK_ACCESS(nnsi)->pid = nsinfo__pid(nsi);
197 	RC_CHK_ACCESS(nnsi)->tgid = nsinfo__tgid(nsi);
198 	RC_CHK_ACCESS(nnsi)->nstgid = nsinfo__nstgid(nsi);
199 	RC_CHK_ACCESS(nnsi)->need_setns = nsinfo__need_setns(nsi);
200 	RC_CHK_ACCESS(nnsi)->in_pidns = nsinfo__in_pidns(nsi);
201 	if (nsinfo__mntns_path(nsi)) {
202 		RC_CHK_ACCESS(nnsi)->mntns_path = strdup(nsinfo__mntns_path(nsi));
203 		if (!RC_CHK_ACCESS(nnsi)->mntns_path) {
204 			nsinfo__put(nnsi);
205 			return NULL;
206 		}
207 	}
208 
209 	return nnsi;
210 }
211 
212 static refcount_t *nsinfo__refcnt(struct nsinfo *nsi)
213 {
214 	return &RC_CHK_ACCESS(nsi)->refcnt;
215 }
216 
217 static void nsinfo__delete(struct nsinfo *nsi)
218 {
219 	if (nsi) {
220 		WARN_ONCE(refcount_read(nsinfo__refcnt(nsi)) != 0, "nsinfo refcnt unbalanced\n");
221 		zfree(&RC_CHK_ACCESS(nsi)->mntns_path);
222 		RC_CHK_FREE(nsi);
223 	}
224 }
225 
226 struct nsinfo *nsinfo__get(struct nsinfo *nsi)
227 {
228 	struct nsinfo *result;
229 
230 	if (RC_CHK_GET(result, nsi))
231 		refcount_inc(nsinfo__refcnt(nsi));
232 
233 	return result;
234 }
235 
236 void nsinfo__put(struct nsinfo *nsi)
237 {
238 	if (nsi && refcount_dec_and_test(nsinfo__refcnt(nsi)))
239 		nsinfo__delete(nsi);
240 	else
241 		RC_CHK_PUT(nsi);
242 }
243 
244 bool nsinfo__need_setns(const struct nsinfo *nsi)
245 {
246 	return RC_CHK_ACCESS(nsi)->need_setns;
247 }
248 
249 void nsinfo__clear_need_setns(struct nsinfo *nsi)
250 {
251 	RC_CHK_ACCESS(nsi)->need_setns = false;
252 }
253 
254 pid_t nsinfo__tgid(const struct nsinfo  *nsi)
255 {
256 	return RC_CHK_ACCESS(nsi)->tgid;
257 }
258 
259 pid_t nsinfo__nstgid(const struct nsinfo  *nsi)
260 {
261 	return RC_CHK_ACCESS(nsi)->nstgid;
262 }
263 
264 pid_t nsinfo__pid(const struct nsinfo  *nsi)
265 {
266 	return RC_CHK_ACCESS(nsi)->pid;
267 }
268 
269 pid_t nsinfo__in_pidns(const struct nsinfo  *nsi)
270 {
271 	return RC_CHK_ACCESS(nsi)->in_pidns;
272 }
273 
274 void nsinfo__mountns_enter(struct nsinfo *nsi,
275 				  struct nscookie *nc)
276 {
277 	char curpath[PATH_MAX];
278 	int oldns = -1;
279 	int newns = -1;
280 	char *oldcwd = NULL;
281 
282 	if (nc == NULL)
283 		return;
284 
285 	nc->oldns = -1;
286 	nc->newns = -1;
287 
288 	if (!nsi || !nsinfo__need_setns(nsi))
289 		return;
290 
291 	if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
292 		return;
293 
294 	oldcwd = get_current_dir_name();
295 	if (!oldcwd)
296 		return;
297 
298 	oldns = open(curpath, O_RDONLY);
299 	if (oldns < 0)
300 		goto errout;
301 
302 	newns = open(nsinfo__mntns_path(nsi), O_RDONLY);
303 	if (newns < 0)
304 		goto errout;
305 
306 	if (setns(newns, CLONE_NEWNS) < 0)
307 		goto errout;
308 
309 	nc->oldcwd = oldcwd;
310 	nc->oldns = oldns;
311 	nc->newns = newns;
312 	return;
313 
314 errout:
315 	free(oldcwd);
316 	if (oldns > -1)
317 		close(oldns);
318 	if (newns > -1)
319 		close(newns);
320 }
321 
322 void nsinfo__mountns_exit(struct nscookie *nc)
323 {
324 	if (nc == NULL || nc->oldns == -1 || nc->newns == -1 || !nc->oldcwd)
325 		return;
326 
327 	setns(nc->oldns, CLONE_NEWNS);
328 
329 	if (nc->oldcwd) {
330 		WARN_ON_ONCE(chdir(nc->oldcwd));
331 		zfree(&nc->oldcwd);
332 	}
333 
334 	if (nc->oldns > -1) {
335 		close(nc->oldns);
336 		nc->oldns = -1;
337 	}
338 
339 	if (nc->newns > -1) {
340 		close(nc->newns);
341 		nc->newns = -1;
342 	}
343 }
344 
345 char *nsinfo__realpath(const char *path, struct nsinfo *nsi)
346 {
347 	char *rpath;
348 	struct nscookie nsc;
349 
350 	nsinfo__mountns_enter(nsi, &nsc);
351 	rpath = realpath(path, NULL);
352 	nsinfo__mountns_exit(&nsc);
353 
354 	return rpath;
355 }
356 
357 int nsinfo__stat(const char *filename, struct stat *st, struct nsinfo *nsi)
358 {
359 	int ret;
360 	struct nscookie nsc;
361 
362 	nsinfo__mountns_enter(nsi, &nsc);
363 	ret = stat(filename, st);
364 	nsinfo__mountns_exit(&nsc);
365 
366 	return ret;
367 }
368 
369 bool nsinfo__is_in_root_namespace(void)
370 {
371 	pid_t tgid = 0, nstgid = 0;
372 	bool in_pidns = false;
373 
374 	nsinfo__get_nspid(&tgid, &nstgid, &in_pidns, "/proc/self/status");
375 	return !in_pidns;
376 }
377