whiterose

linux unikernel
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namespaces.c (5152B)


      1 /*
      2  * This program is free software; you can redistribute it and/or modify
      3  * it under the terms of the GNU General Public License, version 2, as
      4  * published by the Free Software Foundation.
      5  *
      6  * Copyright (C) 2017 Hari Bathini, IBM Corporation
      7  */
      8 
      9 #include "namespaces.h"
     10 #include "util.h"
     11 #include "event.h"
     12 #include <sys/types.h>
     13 #include <sys/stat.h>
     14 #include <fcntl.h>
     15 #include <limits.h>
     16 #include <sched.h>
     17 #include <stdlib.h>
     18 #include <stdio.h>
     19 #include <string.h>
     20 #include <unistd.h>
     21 #include <asm/bug.h>
     22 
     23 struct namespaces *namespaces__new(struct namespaces_event *event)
     24 {
     25 	struct namespaces *namespaces;
     26 	u64 link_info_size = ((event ? event->nr_namespaces : NR_NAMESPACES) *
     27 			      sizeof(struct perf_ns_link_info));
     28 
     29 	namespaces = zalloc(sizeof(struct namespaces) + link_info_size);
     30 	if (!namespaces)
     31 		return NULL;
     32 
     33 	namespaces->end_time = -1;
     34 
     35 	if (event)
     36 		memcpy(namespaces->link_info, event->link_info, link_info_size);
     37 
     38 	return namespaces;
     39 }
     40 
     41 void namespaces__free(struct namespaces *namespaces)
     42 {
     43 	free(namespaces);
     44 }
     45 
     46 int nsinfo__init(struct nsinfo *nsi)
     47 {
     48 	char oldns[PATH_MAX];
     49 	char spath[PATH_MAX];
     50 	char *newns = NULL;
     51 	char *statln = NULL;
     52 	struct stat old_stat;
     53 	struct stat new_stat;
     54 	FILE *f = NULL;
     55 	size_t linesz = 0;
     56 	int rv = -1;
     57 
     58 	if (snprintf(oldns, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
     59 		return rv;
     60 
     61 	if (asprintf(&newns, "/proc/%d/ns/mnt", nsi->pid) == -1)
     62 		return rv;
     63 
     64 	if (stat(oldns, &old_stat) < 0)
     65 		goto out;
     66 
     67 	if (stat(newns, &new_stat) < 0)
     68 		goto out;
     69 
     70 	/* Check if the mount namespaces differ, if so then indicate that we
     71 	 * want to switch as part of looking up dso/map data.
     72 	 */
     73 	if (old_stat.st_ino != new_stat.st_ino) {
     74 		nsi->need_setns = true;
     75 		nsi->mntns_path = newns;
     76 		newns = NULL;
     77 	}
     78 
     79 	/* If we're dealing with a process that is in a different PID namespace,
     80 	 * attempt to work out the innermost tgid for the process.
     81 	 */
     82 	if (snprintf(spath, PATH_MAX, "/proc/%d/status", nsi->pid) >= PATH_MAX)
     83 		goto out;
     84 
     85 	f = fopen(spath, "r");
     86 	if (f == NULL)
     87 		goto out;
     88 
     89 	while (getline(&statln, &linesz, f) != -1) {
     90 		/* Use tgid if CONFIG_PID_NS is not defined. */
     91 		if (strstr(statln, "Tgid:") != NULL) {
     92 			nsi->tgid = (pid_t)strtol(strrchr(statln, '\t'),
     93 						     NULL, 10);
     94 			nsi->nstgid = nsi->tgid;
     95 		}
     96 
     97 		if (strstr(statln, "NStgid:") != NULL) {
     98 			nsi->nstgid = (pid_t)strtol(strrchr(statln, '\t'),
     99 						     NULL, 10);
    100 			break;
    101 		}
    102 	}
    103 	rv = 0;
    104 
    105 out:
    106 	if (f != NULL)
    107 		(void) fclose(f);
    108 	free(statln);
    109 	free(newns);
    110 	return rv;
    111 }
    112 
    113 struct nsinfo *nsinfo__new(pid_t pid)
    114 {
    115 	struct nsinfo *nsi;
    116 
    117 	if (pid == 0)
    118 		return NULL;
    119 
    120 	nsi = calloc(1, sizeof(*nsi));
    121 	if (nsi != NULL) {
    122 		nsi->pid = pid;
    123 		nsi->tgid = pid;
    124 		nsi->nstgid = pid;
    125 		nsi->need_setns = false;
    126 		/* Init may fail if the process exits while we're trying to look
    127 		 * at its proc information.  In that case, save the pid but
    128 		 * don't try to enter the namespace.
    129 		 */
    130 		if (nsinfo__init(nsi) == -1)
    131 			nsi->need_setns = false;
    132 
    133 		refcount_set(&nsi->refcnt, 1);
    134 	}
    135 
    136 	return nsi;
    137 }
    138 
    139 struct nsinfo *nsinfo__copy(struct nsinfo *nsi)
    140 {
    141 	struct nsinfo *nnsi;
    142 
    143 	if (nsi == NULL)
    144 		return NULL;
    145 
    146 	nnsi = calloc(1, sizeof(*nnsi));
    147 	if (nnsi != NULL) {
    148 		nnsi->pid = nsi->pid;
    149 		nnsi->tgid = nsi->tgid;
    150 		nnsi->nstgid = nsi->nstgid;
    151 		nnsi->need_setns = nsi->need_setns;
    152 		if (nsi->mntns_path) {
    153 			nnsi->mntns_path = strdup(nsi->mntns_path);
    154 			if (!nnsi->mntns_path) {
    155 				free(nnsi);
    156 				return NULL;
    157 			}
    158 		}
    159 		refcount_set(&nnsi->refcnt, 1);
    160 	}
    161 
    162 	return nnsi;
    163 }
    164 
    165 void nsinfo__delete(struct nsinfo *nsi)
    166 {
    167 	zfree(&nsi->mntns_path);
    168 	free(nsi);
    169 }
    170 
    171 struct nsinfo *nsinfo__get(struct nsinfo *nsi)
    172 {
    173 	if (nsi)
    174 		refcount_inc(&nsi->refcnt);
    175 	return nsi;
    176 }
    177 
    178 void nsinfo__put(struct nsinfo *nsi)
    179 {
    180 	if (nsi && refcount_dec_and_test(&nsi->refcnt))
    181 		nsinfo__delete(nsi);
    182 }
    183 
    184 void nsinfo__mountns_enter(struct nsinfo *nsi,
    185 				  struct nscookie *nc)
    186 {
    187 	char curpath[PATH_MAX];
    188 	int oldns = -1;
    189 	int newns = -1;
    190 	char *oldcwd = NULL;
    191 
    192 	if (nc == NULL)
    193 		return;
    194 
    195 	nc->oldns = -1;
    196 	nc->newns = -1;
    197 
    198 	if (!nsi || !nsi->need_setns)
    199 		return;
    200 
    201 	if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
    202 		return;
    203 
    204 	oldcwd = get_current_dir_name();
    205 	if (!oldcwd)
    206 		return;
    207 
    208 	oldns = open(curpath, O_RDONLY);
    209 	if (oldns < 0)
    210 		goto errout;
    211 
    212 	newns = open(nsi->mntns_path, O_RDONLY);
    213 	if (newns < 0)
    214 		goto errout;
    215 
    216 	if (setns(newns, CLONE_NEWNS) < 0)
    217 		goto errout;
    218 
    219 	nc->oldcwd = oldcwd;
    220 	nc->oldns = oldns;
    221 	nc->newns = newns;
    222 	return;
    223 
    224 errout:
    225 	free(oldcwd);
    226 	if (oldns > -1)
    227 		close(oldns);
    228 	if (newns > -1)
    229 		close(newns);
    230 }
    231 
    232 void nsinfo__mountns_exit(struct nscookie *nc)
    233 {
    234 	if (nc == NULL || nc->oldns == -1 || nc->newns == -1 || !nc->oldcwd)
    235 		return;
    236 
    237 	setns(nc->oldns, CLONE_NEWNS);
    238 
    239 	if (nc->oldcwd) {
    240 		WARN_ON_ONCE(chdir(nc->oldcwd));
    241 		zfree(&nc->oldcwd);
    242 	}
    243 
    244 	if (nc->oldns > -1) {
    245 		close(nc->oldns);
    246 		nc->oldns = -1;
    247 	}
    248 
    249 	if (nc->newns > -1) {
    250 		close(nc->newns);
    251 		nc->newns = -1;
    252 	}
    253 }
    254 
    255 char *nsinfo__realpath(const char *path, struct nsinfo *nsi)
    256 {
    257 	char *rpath;
    258 	struct nscookie nsc;
    259 
    260 	nsinfo__mountns_enter(nsi, &nsc);
    261 	rpath = realpath(path, NULL);
    262 	nsinfo__mountns_exit(&nsc);
    263 
    264 	return rpath;
    265 }