[ltt-control.git] / lttng / lttngtrace.c

/*
 * lttngtrace.c
 *
 * lttngtrace starts/stop system wide tracing around program execution.
 *
 * Copyright (c) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * This file should be setuid root, and belong to a "tracing" group. Only users
 * part of the tracing group can trace and view the traces gathered.
 *
 * TODO: LTTng should support per-session tracepoint activation.
 * TODO: use mkstemp() and save last trace name in user's home directory.
 * TODO: drop priv + reenable standard signal handlers + call lttv at the end.
 */

#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <dirent.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <sys/types.h>

#if DEBUG
#define printf_dbg(fmt, args...)	printf(fmt, args)
#else
#define printf_dbg(fmt, ...)
#endif

static char *trace_path;
static char trace_path_pid[PATH_MAX];
static int autotrace;	/*
			 * Is the trace_path automatically chosen in /tmp ? Can
			 * we unlink if needed ?
			 */
static int sigfwd_pid;

static int recunlink(const char *dirname)
{
	DIR *dir;
	struct dirent *entry;
	char path[PATH_MAX];

	dir = opendir(dirname);
	if (dir == NULL) {
		if (errno == ENOENT)
			return 0;
		perror("Error opendir()");
		return -errno;
	}

	while ((entry = readdir(dir)) != NULL) {
		if (strcmp(entry->d_name, ".") && strcmp(entry->d_name, "..")) {
			snprintf(path, (size_t) PATH_MAX, "%s/%s", dirname,
				 entry->d_name);
			if (entry->d_type == DT_DIR)
				recunlink(path);
			else
				unlink(path);
		}
	}
	closedir(dir);
	rmdir(dirname);

	return 0;
}

static int start_tracing(void)
{
	int ret;
	char command[PATH_MAX];

	if (autotrace) {
		ret = recunlink(trace_path);
		if (ret)
			return ret;
	}

	/*
	 * Create the directory in /tmp to deal with races (refuse if fail).
	 * Only allow user and group to read the trace data (to limit
	 * information disclosure).
	 */
	ret = mkdir(trace_path, S_IRWXU|S_IRWXG);
	if (ret) {
		perror("Trace directory creation error");
		return ret;
	}
	ret = system("ltt-armall > /dev/null");
	if (ret)
		return ret;

	ret = snprintf(command, PATH_MAX - 1,
		       "lttctl -C -w %s autotrace1 > /dev/null",
		       trace_path);
	ret = ret < 0 ? ret : 0;
	if (ret)
		return ret;
	ret = system(command);
	if (ret)
		return ret;
}

static int stop_tracing(uid_t uid, gid_t egid)
{
	int ret;

	ret = system("lttctl -D autotrace1 > /dev/null");
	if (ret)
		return ret;
	ret = system("ltt-disarmall > /dev/null");
	if (ret)
		return ret;
	/* Hand the trace back to the user after tracing is over */
	ret = chown(trace_path, uid, egid);
	if (ret) {
		perror("chown error");
		return ret;
	}
}

static int write_child_pid(pid_t pid, uid_t uid, gid_t gid)
{
	int fd;
	FILE *fp;
	int ret;

	/* Create the file as exclusive to deal with /tmp file creation races */
	fd = open(trace_path_pid, O_WRONLY | O_CREAT | O_EXCL | O_TRUNC,
		  S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
	fp = fdopen(fd, "w");
	if (!fp) {
		perror("Error writing child pid");
		return -errno;
	}
	
	fprintf(fp, "%u", (unsigned int) pid);
	ret = fclose(fp);
	if (ret)
		perror("Error in fclose");
	/* Hand pid information file back to user */
	ret = chown(trace_path_pid, uid, gid);
	if (ret)
		perror("chown error");
	return ret;
}

static int parse_options(int argc, char *argv[], int *arg)
{
	int ret = 0;

	for (;;) {
		if (*arg >= argc
		    || argv[*arg][0] != '-'
		    || argv[*arg][0] == '\0'
		    || argv[*arg][1] == '\0'
		    || !strcmp(argv[*arg], "--"))
			break;
		switch (argv[*arg][1]) {
		case 'o':	if (*arg + 1 >= argc) {
					printf("Missing -o trace name\n");
					ret = -EINVAL;
					break;
				}
				trace_path = argv[*arg + 1];
				(*arg) += 2;
				break;
		default:	printf("Unknown option -%c\n", argv[*arg][1]);
				ret = -EINVAL;
				return ret;
		}
	}
	return ret;
}

static int init_trace_path(void)
{
	int ret;

	if (!trace_path) {
		trace_path = "/tmp/autotrace1";
		autotrace = 1;
	}
	ret = snprintf(trace_path_pid, PATH_MAX - 1, "%s/%s",
		       trace_path, "pid");
	ret = ret < 0 ? ret : 0;
	return ret;
}

static void sighandler(int signo, siginfo_t *siginfo, void *context)
{
	kill(sigfwd_pid, signo);
}

static int init_sighand(sigset_t *saved_mask)
{
	sigset_t sig_all_mask;
	int gret = 0, ret;

	/* Block signals */
	ret = sigfillset(&sig_all_mask);
	if (ret)
		perror("Error in sigfillset");
	gret = (gret == 0) ? ret : gret;
	ret = sigprocmask(SIG_SETMASK, &sig_all_mask, saved_mask);
	if (ret)
		perror("Error in sigprocmask");
	gret = (gret == 0) ? ret : gret;
	return gret;
}

static int forward_signals(pid_t pid, sigset_t *saved_mask)
{
	struct sigaction act;
	int gret = 0, ret;

	/* Forward SIGINT and SIGTERM */
	sigfwd_pid = pid;
	act.sa_sigaction = sighandler;
	act.sa_flags = SA_SIGINFO | SA_RESTART;
	sigemptyset(&act.sa_mask);
	ret = sigaction(SIGINT, &act, NULL);
	if (ret)
		perror("Error in sigaction");
	gret = (gret == 0) ? ret : gret;
	ret = sigaction(SIGTERM, &act, NULL);
	if (ret)
		perror("Error in sigaction");
	gret = (gret == 0) ? ret : gret;

	/* Reenable signals */
	ret = sigprocmask(SIG_SETMASK, saved_mask, NULL);
	if (ret)
		perror("Error in sigprocmask");
	gret = (gret == 0) ? ret : gret;
	return gret;
}

int main(int argc, char *argv[])
{
	uid_t euid, uid;
	gid_t egid, gid;
	pid_t pid;
	int gret = 0, ret = 0;
	int arg = 1;
	sigset_t saved_mask;

	if (argc < 2)
		return -ENOENT;

	euid = geteuid();
	uid = getuid();
	egid = getegid();
	gid = geteuid();

	if (euid != 0 && uid != 0) {
		printf("%s must be setuid root\n", argv[0]);
		return -EPERM;
	}

	printf_dbg("euid: %d\n", euid);
	printf_dbg("uid: %d\n", uid);
	printf_dbg("egid: %d\n", egid);
	printf_dbg("gid: %d\n", gid);

	if (arg < argc) {
		ret = parse_options(argc, argv, &arg);
		if (ret)
			return ret;
	}

	ret = init_trace_path();
	gret = (gret == 0) ? ret : gret;

	ret = init_sighand(&saved_mask);
	gret = (gret == 0) ? ret : gret;

	ret = start_tracing();
	if (ret)
		return ret;

	pid = fork();
	if (pid > 0) {		/* parent */
		int status;

		ret = forward_signals(pid, &saved_mask);
		gret = (gret == 0) ? ret : gret;
		pid = wait(&status);
		if (pid == -1)
			gret = (gret == 0) ? -errno : gret;

		ret = stop_tracing(uid, egid);
		gret = (gret == 0) ? ret : gret;
		ret = write_child_pid(pid, uid, egid);
		gret = (gret == 0) ? ret : gret;
	} else if (pid == 0) {	/* child */
		/* Drop root euid before executing child program */
		seteuid(uid);
		/* Reenable signals */
		ret = sigprocmask(SIG_SETMASK, &saved_mask, NULL);
		if (ret) {
			perror("Error in sigprocmask");
			return ret;
		}
		ret = execvp(argv[arg], &argv[arg]);
		if (ret)
			perror("Execution error");
		return ret;
	} else {		/* error */
		perror("Error in fork");
		return -errno;
	}
	return ret;
}
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	}