1// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2/* Copyright (c) 2015-2017 Daniel Borkmann */
3/* Copyright (c) 2018 Netronome Systems, Inc. */
4
5#include <errno.h>
6#include <limits.h>
7#include <signal.h>
8#include <stdio.h>
9#include <string.h>
10#include <unistd.h>
11#include <linux/magic.h>
12#include <fcntl.h>
13#include <sys/vfs.h>
14
15#include "main.h"
16
17#ifndef TRACEFS_MAGIC
18# define TRACEFS_MAGIC	0x74726163
19#endif
20
21#define _textify(x)	#x
22#define textify(x)	_textify(x)
23
24FILE *trace_pipe_fd;
25char *buff;
26
27static int validate_tracefs_mnt(const char *mnt, unsigned long magic)
28{
29	struct statfs st_fs;
30
31	if (statfs(mnt, &st_fs) < 0)
32		return -ENOENT;
33	if ((unsigned long)st_fs.f_type != magic)
34		return -ENOENT;
35
36	return 0;
37}
38
39static bool
40find_tracefs_mnt_single(unsigned long magic, char *mnt, const char *mntpt)
41{
42	size_t src_len;
43
44	if (validate_tracefs_mnt(mntpt, magic))
45		return false;
46
47	src_len = strlen(mntpt);
48	if (src_len + 1 >= PATH_MAX) {
49		p_err("tracefs mount point name too long");
50		return false;
51	}
52
53	strcpy(mnt, mntpt);
54	return true;
55}
56
57static bool get_tracefs_pipe(char *mnt)
58{
59	static const char * const known_mnts[] = {
60		"/sys/kernel/debug/tracing",
61		"/sys/kernel/tracing",
62		"/tracing",
63		"/trace",
64	};
65	const char *pipe_name = "/trace_pipe";
66	const char *fstype = "tracefs";
67	char type[100], format[32];
68	const char * const *ptr;
69	bool found = false;
70	FILE *fp;
71
72	for (ptr = known_mnts; ptr < known_mnts + ARRAY_SIZE(known_mnts); ptr++)
73		if (find_tracefs_mnt_single(TRACEFS_MAGIC, mnt, *ptr))
74			goto exit_found;
75
76	fp = fopen("/proc/mounts", "r");
77	if (!fp)
78		return false;
79
80	/* Allow room for NULL terminating byte and pipe file name */
81	snprintf(format, sizeof(format), "%%*s %%%zds %%99s %%*s %%*d %%*d\\n",
82		 PATH_MAX - strlen(pipe_name) - 1);
83	while (fscanf(fp, format, mnt, type) == 2)
84		if (strcmp(type, fstype) == 0) {
85			found = true;
86			break;
87		}
88	fclose(fp);
89
90	/* The string from fscanf() might be truncated, check mnt is valid */
91	if (found && validate_tracefs_mnt(mnt, TRACEFS_MAGIC))
92		goto exit_found;
93
94	if (block_mount)
95		return false;
96
97	p_info("could not find tracefs, attempting to mount it now");
98	/* Most of the time, tracefs is automatically mounted by debugfs at
99	 * /sys/kernel/debug/tracing when we try to access it. If we could not
100	 * find it, it is likely that debugfs is not mounted. Let's give one
101	 * attempt at mounting just tracefs at /sys/kernel/tracing.
102	 */
103	strcpy(mnt, known_mnts[1]);
104	if (mount_tracefs(mnt))
105		return false;
106
107exit_found:
108	strcat(mnt, pipe_name);
109	return true;
110}
111
112static void exit_tracelog(int signum)
113{
114	fclose(trace_pipe_fd);
115	free(buff);
116
117	if (json_output) {
118		jsonw_end_array(json_wtr);
119		jsonw_destroy(&json_wtr);
120	}
121
122	exit(0);
123}
124
125int do_tracelog(int argc, char **argv)
126{
127	const struct sigaction act = {
128		.sa_handler = exit_tracelog
129	};
130	char trace_pipe[PATH_MAX];
131	size_t buff_len = 0;
132
133	if (json_output)
134		jsonw_start_array(json_wtr);
135
136	if (!get_tracefs_pipe(trace_pipe))
137		return -1;
138
139	trace_pipe_fd = fopen(trace_pipe, "r");
140	if (!trace_pipe_fd) {
141		p_err("could not open trace pipe: %s", strerror(errno));
142		return -1;
143	}
144
145	sigaction(SIGHUP, &act, NULL);
146	sigaction(SIGINT, &act, NULL);
147	sigaction(SIGTERM, &act, NULL);
148	while (1) {
149		ssize_t ret;
150
151		ret = getline(&buff, &buff_len, trace_pipe_fd);
152		if (ret <= 0) {
153			p_err("failed to read content from trace pipe: %s",
154			      strerror(errno));
155			break;
156		}
157		if (json_output)
158			jsonw_string(json_wtr, buff);
159		else
160			printf("%s", buff);
161	}
162
163	fclose(trace_pipe_fd);
164	free(buff);
165	return -1;
166}
167