Commit | Line | Data |
---|---|---|
6f3a6fc5 MD |
1 | /* |
2 | * lttngtrace.c | |
3 | * | |
4 | * lttngtrace starts/stop system wide tracing around program execution. | |
5 | * | |
6 | * Copyright (c) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
7 | * | |
8 | * This program is free software; you can redistribute it and/or modify | |
9 | * it under the terms of the GNU General Public License as published by | |
10 | * the Free Software Foundation; either version 2 of the License, or | |
11 | * (at your option) any later version. | |
12 | * | |
13 | * This program is distributed in the hope that it will be useful, | |
14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | * GNU General Public License for more details. | |
17 | * | |
18 | * You should have received a copy of the GNU General Public License along | |
19 | * with this program; if not, write to the Free Software Foundation, Inc., | |
20 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. | |
21 | * | |
22 | * This file should be setuid root, and belong to a "tracing" group. Only users | |
23 | * part of the tracing group can trace and view the traces gathered. | |
24 | * | |
25 | * TODO: LTTng should support per-session tracepoint activation. | |
26 | * TODO: use mkstemp() and save last trace name in user's home directory. | |
c94203ed | 27 | * TODO: drop priv + reenable standard signal handlers + call lttv at the end. |
6f3a6fc5 MD |
28 | */ |
29 | ||
30 | #include <errno.h> | |
31 | #include <stdio.h> | |
32 | #include <fcntl.h> | |
33 | #include <signal.h> | |
34 | #include <unistd.h> | |
35 | #include <stdlib.h> | |
36 | #include <string.h> | |
37 | #include <limits.h> | |
38 | #include <dirent.h> | |
39 | #include <sys/wait.h> | |
40 | #include <sys/stat.h> | |
41 | #include <sys/types.h> | |
42 | ||
43 | #if DEBUG | |
44 | #define printf_dbg(fmt, args...) printf(fmt, args) | |
45 | #else | |
46 | #define printf_dbg(fmt, ...) | |
47 | #endif | |
48 | ||
49 | static char *trace_path; | |
50 | static char trace_path_pid[PATH_MAX]; | |
51 | static int autotrace; /* | |
52 | * Is the trace_path automatically chosen in /tmp ? Can | |
53 | * we unlink if needed ? | |
54 | */ | |
55 | static int sigfwd_pid; | |
56 | ||
57 | static int recunlink(const char *dirname) | |
58 | { | |
59 | DIR *dir; | |
60 | struct dirent *entry; | |
61 | char path[PATH_MAX]; | |
62 | ||
63 | dir = opendir(dirname); | |
64 | if (dir == NULL) { | |
65 | if (errno == ENOENT) | |
66 | return 0; | |
67 | perror("Error opendir()"); | |
68 | return -errno; | |
69 | } | |
70 | ||
71 | while ((entry = readdir(dir)) != NULL) { | |
72 | if (strcmp(entry->d_name, ".") && strcmp(entry->d_name, "..")) { | |
73 | snprintf(path, (size_t) PATH_MAX, "%s/%s", dirname, | |
74 | entry->d_name); | |
75 | if (entry->d_type == DT_DIR) | |
76 | recunlink(path); | |
77 | else | |
78 | unlink(path); | |
79 | } | |
80 | } | |
81 | closedir(dir); | |
82 | rmdir(dirname); | |
83 | ||
84 | return 0; | |
85 | } | |
86 | ||
87 | static int start_tracing(void) | |
88 | { | |
89 | int ret; | |
90 | char command[PATH_MAX]; | |
91 | ||
92 | if (autotrace) { | |
93 | ret = recunlink(trace_path); | |
94 | if (ret) | |
95 | return ret; | |
96 | } | |
97 | ||
98 | /* | |
99 | * Create the directory in /tmp to deal with races (refuse if fail). | |
100 | * Only allow user and group to read the trace data (to limit | |
101 | * information disclosure). | |
102 | */ | |
103 | ret = mkdir(trace_path, S_IRWXU|S_IRWXG); | |
104 | if (ret) { | |
105 | perror("Trace directory creation error"); | |
106 | return ret; | |
107 | } | |
108 | ret = system("ltt-armall > /dev/null"); | |
109 | if (ret) | |
110 | return ret; | |
111 | ||
112 | ret = snprintf(command, PATH_MAX - 1, | |
113 | "lttctl -C -w %s autotrace1 > /dev/null", | |
114 | trace_path); | |
115 | ret = ret < 0 ? ret : 0; | |
116 | if (ret) | |
117 | return ret; | |
118 | ret = system(command); | |
119 | if (ret) | |
120 | return ret; | |
121 | } | |
122 | ||
123 | static int stop_tracing(uid_t uid, gid_t egid) | |
124 | { | |
125 | int ret; | |
126 | ||
127 | ret = system("lttctl -D autotrace1 > /dev/null"); | |
128 | if (ret) | |
129 | return ret; | |
130 | ret = system("ltt-disarmall > /dev/null"); | |
131 | if (ret) | |
132 | return ret; | |
133 | /* Hand the trace back to the user after tracing is over */ | |
134 | ret = chown(trace_path, uid, egid); | |
135 | if (ret) { | |
136 | perror("chown error"); | |
137 | return ret; | |
138 | } | |
139 | } | |
140 | ||
141 | static int write_child_pid(pid_t pid, uid_t uid, gid_t gid) | |
142 | { | |
143 | int fd; | |
144 | FILE *fp; | |
145 | int ret; | |
146 | ||
147 | /* Create the file as exclusive to deal with /tmp file creation races */ | |
148 | fd = open(trace_path_pid, O_WRONLY | O_CREAT | O_EXCL | O_TRUNC, | |
149 | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP); | |
150 | fp = fdopen(fd, "w"); | |
151 | if (!fp) { | |
152 | perror("Error writing child pid"); | |
153 | return -errno; | |
154 | } | |
155 | ||
156 | fprintf(fp, "%u", (unsigned int) pid); | |
157 | ret = fclose(fp); | |
158 | if (ret) | |
159 | perror("Error in fclose"); | |
160 | /* Hand pid information file back to user */ | |
161 | ret = chown(trace_path_pid, uid, gid); | |
162 | if (ret) | |
163 | perror("chown error"); | |
164 | return ret; | |
165 | } | |
166 | ||
167 | static int parse_options(int argc, char *argv[], int *arg) | |
168 | { | |
169 | int ret = 0; | |
170 | ||
171 | for (;;) { | |
172 | if (*arg >= argc | |
173 | || argv[*arg][0] != '-' | |
174 | || argv[*arg][0] == '\0' | |
175 | || argv[*arg][1] == '\0' | |
176 | || !strcmp(argv[*arg], "--")) | |
177 | break; | |
178 | switch (argv[*arg][1]) { | |
179 | case 'o': if (*arg + 1 >= argc) { | |
180 | printf("Missing -o trace name\n"); | |
181 | ret = -EINVAL; | |
182 | break; | |
183 | } | |
184 | trace_path = argv[*arg + 1]; | |
185 | (*arg) += 2; | |
186 | break; | |
187 | default: printf("Unknown option -%c\n", argv[*arg][1]); | |
188 | ret = -EINVAL; | |
189 | return ret; | |
190 | } | |
191 | } | |
192 | return ret; | |
193 | } | |
194 | ||
195 | static int init_trace_path(void) | |
196 | { | |
197 | int ret; | |
198 | ||
199 | if (!trace_path) { | |
200 | trace_path = "/tmp/autotrace1"; | |
201 | autotrace = 1; | |
202 | } | |
203 | ret = snprintf(trace_path_pid, PATH_MAX - 1, "%s/%s", | |
204 | trace_path, "pid"); | |
205 | ret = ret < 0 ? ret : 0; | |
206 | return ret; | |
207 | } | |
208 | ||
209 | static void sighandler(int signo, siginfo_t *siginfo, void *context) | |
210 | { | |
211 | kill(sigfwd_pid, signo); | |
212 | } | |
213 | ||
214 | static int init_sighand(sigset_t *saved_mask) | |
215 | { | |
216 | sigset_t sig_all_mask; | |
217 | int gret = 0, ret; | |
218 | ||
219 | /* Block signals */ | |
220 | ret = sigfillset(&sig_all_mask); | |
221 | if (ret) | |
222 | perror("Error in sigfillset"); | |
223 | gret = (gret == 0) ? ret : gret; | |
224 | ret = sigprocmask(SIG_SETMASK, &sig_all_mask, saved_mask); | |
225 | if (ret) | |
226 | perror("Error in sigprocmask"); | |
227 | gret = (gret == 0) ? ret : gret; | |
228 | return gret; | |
229 | } | |
230 | ||
231 | static int forward_signals(pid_t pid, sigset_t *saved_mask) | |
232 | { | |
233 | struct sigaction act; | |
234 | int gret = 0, ret; | |
235 | ||
236 | /* Forward SIGINT and SIGTERM */ | |
237 | sigfwd_pid = pid; | |
238 | act.sa_sigaction = sighandler; | |
239 | act.sa_flags = SA_SIGINFO | SA_RESTART; | |
240 | sigemptyset(&act.sa_mask); | |
241 | ret = sigaction(SIGINT, &act, NULL); | |
242 | if (ret) | |
243 | perror("Error in sigaction"); | |
244 | gret = (gret == 0) ? ret : gret; | |
245 | ret = sigaction(SIGTERM, &act, NULL); | |
246 | if (ret) | |
247 | perror("Error in sigaction"); | |
248 | gret = (gret == 0) ? ret : gret; | |
249 | ||
250 | /* Reenable signals */ | |
251 | ret = sigprocmask(SIG_SETMASK, saved_mask, NULL); | |
252 | if (ret) | |
253 | perror("Error in sigprocmask"); | |
254 | gret = (gret == 0) ? ret : gret; | |
255 | return gret; | |
256 | } | |
257 | ||
258 | int main(int argc, char *argv[]) | |
259 | { | |
260 | uid_t euid, uid; | |
261 | gid_t egid, gid; | |
262 | pid_t pid; | |
263 | int gret = 0, ret = 0; | |
264 | int arg = 1; | |
265 | sigset_t saved_mask; | |
266 | ||
267 | if (argc < 2) | |
268 | return -ENOENT; | |
269 | ||
270 | euid = geteuid(); | |
271 | uid = getuid(); | |
272 | egid = getegid(); | |
273 | gid = geteuid(); | |
274 | ||
275 | if (euid != 0 && uid != 0) { | |
276 | printf("%s must be setuid root\n", argv[0]); | |
277 | return -EPERM; | |
278 | } | |
279 | ||
280 | printf_dbg("euid: %d\n", euid); | |
281 | printf_dbg("uid: %d\n", uid); | |
282 | printf_dbg("egid: %d\n", egid); | |
283 | printf_dbg("gid: %d\n", gid); | |
284 | ||
285 | if (arg < argc) { | |
286 | ret = parse_options(argc, argv, &arg); | |
287 | if (ret) | |
288 | return ret; | |
289 | } | |
290 | ||
291 | ret = init_trace_path(); | |
292 | gret = (gret == 0) ? ret : gret; | |
293 | ||
294 | ret = init_sighand(&saved_mask); | |
295 | gret = (gret == 0) ? ret : gret; | |
296 | ||
297 | ret = start_tracing(); | |
298 | if (ret) | |
299 | return ret; | |
300 | ||
301 | pid = fork(); | |
302 | if (pid > 0) { /* parent */ | |
303 | int status; | |
304 | ||
305 | ret = forward_signals(pid, &saved_mask); | |
306 | gret = (gret == 0) ? ret : gret; | |
307 | pid = wait(&status); | |
308 | if (pid == -1) | |
309 | gret = (gret == 0) ? -errno : gret; | |
310 | ||
311 | ret = stop_tracing(uid, egid); | |
312 | gret = (gret == 0) ? ret : gret; | |
313 | ret = write_child_pid(pid, uid, egid); | |
314 | gret = (gret == 0) ? ret : gret; | |
315 | } else if (pid == 0) { /* child */ | |
316 | /* Drop root euid before executing child program */ | |
317 | seteuid(uid); | |
318 | /* Reenable signals */ | |
319 | ret = sigprocmask(SIG_SETMASK, &saved_mask, NULL); | |
320 | if (ret) { | |
321 | perror("Error in sigprocmask"); | |
322 | return ret; | |
323 | } | |
324 | ret = execvp(argv[arg], &argv[arg]); | |
325 | if (ret) | |
326 | perror("Execution error"); | |
327 | return ret; | |
328 | } else { /* error */ | |
329 | perror("Error in fork"); | |
330 | return -errno; | |
331 | } | |
332 | return ret; | |
333 | } |