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1 | /* |
2 | * Copyright (C) 2016 - Aravind HT <aravind.ht@gmail.com> | |
3 | * 2016 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
4 | * | |
5 | * This library is free software; you can redistribute it and/or | |
6 | * modify it under the terms of the GNU Lesser General Public | |
7 | * License as published by the Free Software Foundation; only | |
8 | * version 2.1 of the License. | |
9 | * | |
10 | * This library is distributed in the hope that it will be useful, | |
11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | * Lesser General Public License for more details. | |
14 | * | |
15 | * You should have received a copy of the GNU Lesser General Public | |
16 | * License along with this library; if not, write to the Free Software | |
17 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
18 | */ | |
19 | ||
20 | #define _GNU_SOURCE | |
21 | #include <limits.h> | |
22 | #include <stdio.h> | |
23 | #include <stdlib.h> | |
24 | #include <string.h> | |
25 | #include <sys/types.h> | |
26 | #include <unistd.h> | |
27 | #include <assert.h> | |
28 | #include <errno.h> | |
29 | #include <fcntl.h> | |
30 | #include <sys/select.h> | |
31 | #include <sys/resource.h> | |
32 | #include <sys/time.h> | |
33 | #include <fcntl.h> | |
34 | #include <pthread.h> | |
35 | #include <urcu/compiler.h> | |
36 | #include <urcu/tls-compat.h> | |
37 | ||
38 | #include <ust-fd.h> | |
39 | #include <helper.h> | |
40 | #include <lttng/ust-error.h> | |
41 | #include <usterr-signal-safe.h> | |
42 | ||
43 | #include "../liblttng-ust/compat.h" | |
44 | ||
45 | /* Operations on the fd set. */ | |
46 | #define IS_FD_VALID(fd) ((fd) >= 0 && (fd) < lttng_ust_max_fd) | |
47 | #define GET_FD_SET_FOR_FD(fd, fd_sets) (&((fd_sets)[(fd) / FD_SETSIZE])) | |
48 | #define CALC_INDEX_TO_SET(fd) ((fd) % FD_SETSIZE) | |
49 | ||
50 | /* Check fd validity before calling these. */ | |
51 | #define ADD_FD_TO_SET(fd, fd_sets) \ | |
52 | FD_SET(CALC_INDEX_TO_SET(fd), GET_FD_SET_FOR_FD(fd, fd_sets)) | |
53 | #define IS_FD_SET(fd, fd_sets) \ | |
54 | FD_ISSET(CALC_INDEX_TO_SET(fd), GET_FD_SET_FOR_FD(fd, fd_sets)) | |
55 | #define DEL_FD_FROM_SET(fd, fd_sets) \ | |
56 | FD_CLR(CALC_INDEX_TO_SET(fd), GET_FD_SET_FOR_FD(fd, fd_sets)) | |
57 | ||
58 | /* | |
59 | * Protect the lttng_fd_set. Nests within the ust_lock, and therefore | |
60 | * within the libc dl lock. Therefore, we need to fixup the TLS before | |
61 | * nesting into this lock. | |
62 | */ | |
63 | static pthread_mutex_t ust_safe_guard_fd_mutex = PTHREAD_MUTEX_INITIALIZER; | |
64 | /* | |
65 | * Track whether we are within lttng-ust or application, for close | |
66 | * system call override by LD_PRELOAD library. | |
67 | */ | |
68 | static DEFINE_URCU_TLS(int, thread_fd_tracking); | |
69 | ||
70 | /* fd_set used to book keep fd being used by lttng-ust. */ | |
71 | static fd_set *lttng_fd_set; | |
72 | static int lttng_ust_max_fd; | |
73 | static int num_fd_sets; | |
74 | ||
75 | /* | |
76 | * Force a read (imply TLS fixup for dlopen) of TLS variables. | |
77 | */ | |
78 | void lttng_ust_fixup_fd_tracker_tls(void) | |
79 | { | |
80 | asm volatile ("" : : "m" (URCU_TLS(thread_fd_tracking))); | |
81 | } | |
82 | ||
83 | /* | |
84 | * Allocate the fd set array based on the hard limit set for this | |
85 | * process. This will be called during the constructor execution | |
86 | * and will also be called in the child after fork via lttng_ust_init. | |
87 | */ | |
88 | void lttng_ust_init_fd_tracker(void) | |
89 | { | |
90 | struct rlimit rlim; | |
91 | int i; | |
92 | ||
93 | memset(&rlim, 0, sizeof(rlim)); | |
94 | /* Get the current possible max number of fd for this process. */ | |
95 | if (getrlimit(RLIMIT_NOFILE, &rlim) < 0) | |
96 | abort(); | |
97 | /* | |
98 | * FD set array size determined using the hard limit. Even if | |
99 | * the process wishes to increase its limit using setrlimit, it | |
100 | * can only do so with the softlimit which will be less than the | |
101 | * hard limit. | |
102 | */ | |
103 | lttng_ust_max_fd = rlim.rlim_max; | |
104 | num_fd_sets = lttng_ust_max_fd / FD_SETSIZE; | |
105 | if (lttng_ust_max_fd % FD_SETSIZE) | |
106 | ++num_fd_sets; | |
107 | if (lttng_fd_set != NULL) { | |
108 | free(lttng_fd_set); | |
109 | lttng_fd_set = NULL; | |
110 | } | |
111 | lttng_fd_set = malloc(num_fd_sets * (sizeof(fd_set))); | |
112 | if (!lttng_fd_set) | |
113 | abort(); | |
114 | for (i = 0; i < num_fd_sets; i++) | |
115 | FD_ZERO((<tng_fd_set[i])); | |
116 | } | |
117 | ||
118 | void lttng_ust_lock_fd_tracker(void) | |
119 | { | |
120 | URCU_TLS(thread_fd_tracking) = 1; | |
121 | /* | |
122 | * Ensure the compiler don't move the store after the close() | |
123 | * call in case close() would be marked as leaf. | |
124 | */ | |
125 | cmm_barrier(); | |
126 | pthread_mutex_lock(&ust_safe_guard_fd_mutex); | |
127 | } | |
128 | ||
129 | void lttng_ust_unlock_fd_tracker(void) | |
130 | { | |
131 | pthread_mutex_unlock(&ust_safe_guard_fd_mutex); | |
132 | /* | |
133 | * Ensure the compiler don't move the store before the close() | |
134 | * call, in case close() would be marked as leaf. | |
135 | */ | |
136 | cmm_barrier(); | |
137 | URCU_TLS(thread_fd_tracking) = 0; | |
138 | } | |
139 | ||
140 | /* | |
141 | * Needs to be called with ust_safe_guard_fd_mutex held when opening the fd. | |
142 | * Has strict checking of fd validity. | |
143 | */ | |
144 | void lttng_ust_add_fd_to_tracker(int fd) | |
145 | { | |
146 | assert(URCU_TLS(thread_fd_tracking)); | |
147 | /* Trying to add an fd which we can not accommodate. */ | |
148 | assert(IS_FD_VALID(fd)); | |
149 | /* Setting an fd thats already set. */ | |
150 | assert(!IS_FD_SET(fd, lttng_fd_set)); | |
151 | ||
152 | ADD_FD_TO_SET(fd, lttng_fd_set); | |
153 | } | |
154 | ||
155 | /* | |
156 | * Needs to be called with ust_safe_guard_fd_mutex held when opening the fd. | |
157 | * Has strict checking for fd validity. | |
158 | */ | |
159 | void lttng_ust_delete_fd_from_tracker(int fd) | |
160 | { | |
161 | assert(URCU_TLS(thread_fd_tracking)); | |
162 | /* Not a valid fd. */ | |
163 | assert(IS_FD_VALID(fd)); | |
164 | /* Deleting an fd which was not set. */ | |
165 | assert(IS_FD_SET(fd, lttng_fd_set)); | |
166 | ||
167 | DEL_FD_FROM_SET(fd, lttng_fd_set); | |
168 | } | |
169 | ||
170 | /* | |
171 | * Interface allowing applications to close arbitrary file descriptors. | |
172 | * We check if it is owned by lttng-ust, and return -1, errno=EBADF | |
173 | * instead of closing it if it is the case. | |
174 | */ | |
175 | int lttng_ust_safe_close_fd(int fd, int (*close_cb)(int fd)) | |
176 | { | |
177 | int ret = 0; | |
178 | ||
179 | lttng_ust_fixup_fd_tracker_tls(); | |
180 | ||
181 | /* | |
182 | * If called from lttng-ust, we directly call close without | |
183 | * validating whether the FD is part of the tracked set. | |
184 | */ | |
185 | if (URCU_TLS(thread_fd_tracking)) | |
186 | return close_cb(fd); | |
187 | ||
188 | lttng_ust_lock_fd_tracker(); | |
189 | if (IS_FD_VALID(fd) && IS_FD_SET(fd, lttng_fd_set)) { | |
190 | ret = -1; | |
191 | errno = EBADF; | |
192 | } else { | |
193 | ret = close_cb(fd); | |
194 | } | |
195 | lttng_ust_unlock_fd_tracker(); | |
196 | ||
197 | return ret; | |
198 | } | |
199 | ||
200 | #ifdef __OpenBSD__ | |
201 | static void set_close_success(int *p) | |
202 | { | |
203 | *p = 1; | |
204 | } | |
205 | static int test_close_success(const int *p) | |
206 | { | |
207 | return *p; | |
208 | } | |
209 | #else | |
210 | static void set_close_success(int *p __attribute__((unused))) | |
211 | { | |
212 | } | |
213 | static int test_close_success(const int *p __attribute__((unused))) | |
214 | { | |
215 | return 1; | |
216 | } | |
217 | #endif | |
218 | ||
219 | /* | |
220 | * Implement helper for closefrom() override. | |
221 | */ | |
222 | int lttng_ust_safe_closefrom_fd(int lowfd, int (*close_cb)(int fd)) | |
223 | { | |
224 | int ret = 0, close_success = 0, i; | |
225 | ||
226 | lttng_ust_fixup_fd_tracker_tls(); | |
227 | ||
228 | if (lowfd < 0) { | |
229 | /* | |
230 | * NetBSD return EBADF if fd is invalid. | |
231 | */ | |
232 | errno = EBADF; | |
233 | ret = -1; | |
234 | goto end; | |
235 | } | |
236 | /* | |
237 | * If called from lttng-ust, we directly call close without | |
238 | * validating whether the FD is part of the tracked set. | |
239 | */ | |
240 | if (URCU_TLS(thread_fd_tracking)) { | |
241 | for (i = lowfd; i < lttng_ust_max_fd; i++) { | |
242 | if (close_cb(i) < 0) { | |
243 | switch (errno) { | |
244 | case EBADF: | |
245 | continue; | |
246 | case EINTR: | |
247 | default: | |
248 | ret = -1; | |
249 | goto end; | |
250 | } | |
251 | } | |
252 | set_close_success(&close_success); | |
253 | } | |
254 | } else { | |
255 | lttng_ust_lock_fd_tracker(); | |
256 | for (i = lowfd; i < lttng_ust_max_fd; i++) { | |
257 | if (IS_FD_VALID(i) && IS_FD_SET(i, lttng_fd_set)) | |
258 | continue; | |
259 | if (close_cb(i) < 0) { | |
260 | switch (errno) { | |
261 | case EBADF: | |
262 | continue; | |
263 | case EINTR: | |
264 | default: | |
265 | ret = -1; | |
266 | lttng_ust_unlock_fd_tracker(); | |
267 | goto end; | |
268 | } | |
269 | } | |
270 | set_close_success(&close_success); | |
271 | } | |
272 | lttng_ust_unlock_fd_tracker(); | |
273 | } | |
274 | if (!test_close_success(&close_success)) { | |
275 | /* | |
276 | * OpenBSD return EBADF if fd is greater than all open | |
277 | * file descriptors. | |
278 | */ | |
279 | ret = -1; | |
280 | errno = EBADF; | |
281 | } | |
282 | end: | |
283 | return ret; | |
284 | } |