namespaces.c

  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 <sys/types.h>
 10#include <sys/stat.h>
 11#include <fcntl.h>
 12#include <limits.h>
 13#include <sched.h>
 14#include <stdlib.h>
 15#include <stdio.h>
 16#include <string.h>
 17#include <unistd.h>
 18#include <asm/bug.h>
 19#include <linux/kernel.h>
 20#include <linux/zalloc.h>
 21
 22static const char *perf_ns__names[] = {
 23	[NET_NS_INDEX]		= "net",
 24	[UTS_NS_INDEX]		= "uts",
 25	[IPC_NS_INDEX]		= "ipc",
 26	[PID_NS_INDEX]		= "pid",
 27	[USER_NS_INDEX]		= "user",
 28	[MNT_NS_INDEX]		= "mnt",
 29	[CGROUP_NS_INDEX]	= "cgroup",
 30};
 31
 32const char *perf_ns__name(unsigned int id)
 33{
 34	if (id >= ARRAY_SIZE(perf_ns__names))
 35		return "UNKNOWN";
 36	return perf_ns__names[id];
 37}
 38
 39struct namespaces *namespaces__new(struct perf_record_namespaces *event)
 40{
 41	struct namespaces *namespaces;
 42	u64 link_info_size = ((event ? event->nr_namespaces : NR_NAMESPACES) *
 43			      sizeof(struct perf_ns_link_info));
 44
 45	namespaces = zalloc(sizeof(struct namespaces) + link_info_size);
 46	if (!namespaces)
 47		return NULL;
 48
 49	namespaces->end_time = -1;
 50
 51	if (event)
 52		memcpy(namespaces->link_info, event->link_info, link_info_size);
 53
 54	return namespaces;
 55}
 56
 57void namespaces__free(struct namespaces *namespaces)
 58{
 59	free(namespaces);
 60}
 61
 62static int nsinfo__get_nspid(pid_t *tgid, pid_t *nstgid, bool *in_pidns, const char *path)
 63{
 64	FILE *f = NULL;
 65	char *statln = NULL;
 66	size_t linesz = 0;
 67	char *nspid;
 68
 69	f = fopen(path, "r");
 70	if (f == NULL)
 71		return -1;
 72
 73	while (getline(&statln, &linesz, f) != -1) {
 74		/* Use tgid if CONFIG_PID_NS is not defined. */
 75		if (strstr(statln, "Tgid:") != NULL) {
 76			*tgid = (pid_t)strtol(strrchr(statln, '\t'), NULL, 10);
 77			*nstgid = *tgid;
 78		}
 79
 80		if (strstr(statln, "NStgid:") != NULL) {
 81			nspid = strrchr(statln, '\t');
 82			*nstgid = (pid_t)strtol(nspid, NULL, 10);
 83			/*
 84			 * If innermost tgid is not the first, process is in a different
 85			 * PID namespace.
 86			 */
 87			*in_pidns = (statln + sizeof("NStgid:") - 1) != nspid;
 88			break;
 89		}
 90	}
 91
 92	fclose(f);
 93	free(statln);
 94	return 0;
 95}
 96
 97int nsinfo__init(struct nsinfo *nsi)
 98{
 99	char oldns[PATH_MAX];
100	char spath[PATH_MAX];
101	char *newns = NULL;
102	struct stat old_stat;
103	struct stat new_stat;
104	int rv = -1;
105
106	if (snprintf(oldns, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
107		return rv;
108
109	if (asprintf(&newns, "/proc/%d/ns/mnt", nsinfo__pid(nsi)) == -1)
110		return rv;
111
112	if (stat(oldns, &old_stat) < 0)
113		goto out;
114
115	if (stat(newns, &new_stat) < 0)
116		goto out;
117
118	/* Check if the mount namespaces differ, if so then indicate that we
119	 * want to switch as part of looking up dso/map data.
120	 */
121	if (old_stat.st_ino != new_stat.st_ino) {
122		RC_CHK_ACCESS(nsi)->need_setns = true;
123		RC_CHK_ACCESS(nsi)->mntns_path = newns;
124		newns = NULL;
125	}
126
127	/* If we're dealing with a process that is in a different PID namespace,
128	 * attempt to work out the innermost tgid for the process.
129	 */
130	if (snprintf(spath, PATH_MAX, "/proc/%d/status", nsinfo__pid(nsi)) >= PATH_MAX)
131		goto out;
132
133	rv = nsinfo__get_nspid(&RC_CHK_ACCESS(nsi)->tgid, &RC_CHK_ACCESS(nsi)->nstgid,
134			       &RC_CHK_ACCESS(nsi)->in_pidns, spath);
135
136out:
137	free(newns);
138	return rv;
139}
140
141static struct nsinfo *nsinfo__alloc(void)
142{
143	struct nsinfo *res;
144	RC_STRUCT(nsinfo) *nsi;
145
146	nsi = calloc(1, sizeof(*nsi));
147	if (ADD_RC_CHK(res, nsi))
148		refcount_set(&nsi->refcnt, 1);
149
150	return res;
151}
152
153struct nsinfo *nsinfo__new(pid_t pid)
154{
155	struct nsinfo *nsi;
156
157	if (pid == 0)
158		return NULL;
159
160	nsi = nsinfo__alloc();
161	if (!nsi)
162		return NULL;
163
164	RC_CHK_ACCESS(nsi)->pid = pid;
165	RC_CHK_ACCESS(nsi)->tgid = pid;
166	RC_CHK_ACCESS(nsi)->nstgid = pid;
167	nsinfo__clear_need_setns(nsi);
168	RC_CHK_ACCESS(nsi)->in_pidns = false;
169	/* Init may fail if the process exits while we're trying to look at its
170	 * proc information. In that case, save the pid but don't try to enter
171	 * the namespace.
172	 */
173	if (nsinfo__init(nsi) == -1)
174		nsinfo__clear_need_setns(nsi);
175
176	return nsi;
177}
178
179static const char *nsinfo__mntns_path(const struct nsinfo *nsi)
180{
181	return RC_CHK_ACCESS(nsi)->mntns_path;
182}
183
184struct nsinfo *nsinfo__copy(const struct nsinfo *nsi)
185{
186	struct nsinfo *nnsi;
187
188	if (nsi == NULL)
189		return NULL;
190
191	nnsi = nsinfo__alloc();
192	if (!nnsi)
193		return NULL;
194
195	RC_CHK_ACCESS(nnsi)->pid = nsinfo__pid(nsi);
196	RC_CHK_ACCESS(nnsi)->tgid = nsinfo__tgid(nsi);
197	RC_CHK_ACCESS(nnsi)->nstgid = nsinfo__nstgid(nsi);
198	RC_CHK_ACCESS(nnsi)->need_setns = nsinfo__need_setns(nsi);
199	RC_CHK_ACCESS(nnsi)->in_pidns = nsinfo__in_pidns(nsi);
200	if (nsinfo__mntns_path(nsi)) {
201		RC_CHK_ACCESS(nnsi)->mntns_path = strdup(nsinfo__mntns_path(nsi));
202		if (!RC_CHK_ACCESS(nnsi)->mntns_path) {
203			nsinfo__put(nnsi);
204			return NULL;
205		}
206	}
207
208	return nnsi;
209}
210
211static refcount_t *nsinfo__refcnt(struct nsinfo *nsi)
212{
213	return &RC_CHK_ACCESS(nsi)->refcnt;
214}
215
216static void nsinfo__delete(struct nsinfo *nsi)
217{
218	if (nsi) {
219		WARN_ONCE(refcount_read(nsinfo__refcnt(nsi)) != 0, "nsinfo refcnt unbalanced\n");
220		zfree(&RC_CHK_ACCESS(nsi)->mntns_path);
221		RC_CHK_FREE(nsi);
222	}
223}
224
225struct nsinfo *nsinfo__get(struct nsinfo *nsi)
226{
227	struct nsinfo *result;
228
229	if (RC_CHK_GET(result, nsi))
230		refcount_inc(nsinfo__refcnt(nsi));
231
232	return result;
233}
234
235void nsinfo__put(struct nsinfo *nsi)
236{
237	if (nsi && refcount_dec_and_test(nsinfo__refcnt(nsi)))
238		nsinfo__delete(nsi);
239	else
240		RC_CHK_PUT(nsi);
241}
242
243bool nsinfo__need_setns(const struct nsinfo *nsi)
244{
245	return RC_CHK_ACCESS(nsi)->need_setns;
246}
247
248void nsinfo__clear_need_setns(struct nsinfo *nsi)
249{
250	RC_CHK_ACCESS(nsi)->need_setns = false;
251}
252
253pid_t nsinfo__tgid(const struct nsinfo  *nsi)
254{
255	return RC_CHK_ACCESS(nsi)->tgid;
256}
257
258pid_t nsinfo__nstgid(const struct nsinfo  *nsi)
259{
260	return RC_CHK_ACCESS(nsi)->nstgid;
261}
262
263pid_t nsinfo__pid(const struct nsinfo  *nsi)
264{
265	return RC_CHK_ACCESS(nsi)->pid;
266}
267
268bool nsinfo__in_pidns(const struct nsinfo *nsi)
269{
270	return RC_CHK_ACCESS(nsi)->in_pidns;
271}
272
273void nsinfo__set_in_pidns(struct nsinfo *nsi)
274{
275	RC_CHK_ACCESS(nsi)->in_pidns = true;
276}
277
278void nsinfo__mountns_enter(struct nsinfo *nsi,
279				  struct nscookie *nc)
280{
281	char curpath[PATH_MAX];
282	int oldns = -1;
283	int newns = -1;
284	char *oldcwd = NULL;
285
286	if (nc == NULL)
287		return;
288
289	nc->oldns = -1;
290	nc->newns = -1;
291
292	if (!nsi || !nsinfo__need_setns(nsi))
293		return;
294
295	if (!getcwd(curpath, sizeof(curpath)))
296		return;
297
298	oldcwd = strdup(curpath);
299	if (!oldcwd)
300		return;
301
302	oldns = open("/proc/self/ns/mnt", O_RDONLY);
303	if (oldns < 0)
304		goto errout;
305
306	newns = open(nsinfo__mntns_path(nsi), O_RDONLY);
307	if (newns < 0)
308		goto errout;
309
310	if (setns(newns, CLONE_NEWNS) < 0)
311		goto errout;
312
313	nc->oldcwd = oldcwd;
314	nc->oldns = oldns;
315	nc->newns = newns;
316	return;
317
318errout:
319	free(oldcwd);
320	if (oldns > -1)
321		close(oldns);
322	if (newns > -1)
323		close(newns);
324}
325
326void nsinfo__mountns_exit(struct nscookie *nc)
327{
328	if (nc == NULL || nc->oldns == -1 || nc->newns == -1 || !nc->oldcwd)
329		return;
330
331	setns(nc->oldns, CLONE_NEWNS);
332
333	if (nc->oldcwd) {
334		WARN_ON_ONCE(chdir(nc->oldcwd));
335		zfree(&nc->oldcwd);
336	}
337
338	if (nc->oldns > -1) {
339		close(nc->oldns);
340		nc->oldns = -1;
341	}
342
343	if (nc->newns > -1) {
344		close(nc->newns);
345		nc->newns = -1;
346	}
347}
348
349char *nsinfo__realpath(const char *path, struct nsinfo *nsi)
350{
351	char *rpath;
352	struct nscookie nsc;
353
354	nsinfo__mountns_enter(nsi, &nsc);
355	rpath = realpath(path, NULL);
356	nsinfo__mountns_exit(&nsc);
357
358	return rpath;
359}
360
361int nsinfo__stat(const char *filename, struct stat *st, struct nsinfo *nsi)
362{
363	int ret;
364	struct nscookie nsc;
365
366	nsinfo__mountns_enter(nsi, &nsc);
367	ret = stat(filename, st);
368	nsinfo__mountns_exit(&nsc);
369
370	return ret;
371}
372
373bool nsinfo__is_in_root_namespace(void)
374{
375	pid_t tgid = 0, nstgid = 0;
376	bool in_pidns = false;
377
378	nsinfo__get_nspid(&tgid, &nstgid, &in_pidns, "/proc/self/status");
379	return !in_pidns;
380}