xref: /openbmc/linux/tools/bpf/bpftool/tracelog.c (revision 246bdfa5)
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 
24 FILE *trace_pipe_fd;
25 char *buff;
26 
validate_tracefs_mnt(const char * mnt,unsigned long magic)27 static 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 
39 static bool
find_tracefs_mnt_single(unsigned long magic,char * mnt,const char * mntpt)40 find_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 
get_tracefs_pipe(char * mnt)57 static 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 
107 exit_found:
108 	strcat(mnt, pipe_name);
109 	return true;
110 }
111 
exit_tracelog(int signum)112 static 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 
do_tracelog(int argc,char ** argv)125 int 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