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(mnt: mntpt, magic))
45 return false;
46
47 src_len = strlen(mntpt);
48 if (src_len + 1 >= PATH_MAX) {
49 p_err(fmt: "tracefs mount point name too long");
50 return false;
51 }
52
53 strcpy(p: mnt, q: mntpt);
54 return true;
55}
56
57static bool get_tracefs_pipe(char *mnt)
58{
59 static const char * const known_mnts[] = {
60 "/sys/kernel/tracing",
61 "/sys/kernel/debug/tracing",
62 };
63 const char *pipe_name = "/trace_pipe";
64 const char *fstype = "tracefs";
65 char type[100], format[32];
66 const char * const *ptr;
67 bool found = false;
68 FILE *fp;
69
70 for (ptr = known_mnts; ptr < known_mnts + ARRAY_SIZE(known_mnts); ptr++)
71 if (find_tracefs_mnt_single(TRACEFS_MAGIC, mnt, mntpt: *ptr))
72 goto exit_found;
73
74 fp = fopen("/proc/mounts", "r");
75 if (!fp)
76 return false;
77
78 /* Allow room for NULL terminating byte and pipe file name */
79 snprintf(buf: format, size: sizeof(format), fmt: "%%*s %%%zus %%99s %%*s %%*d %%*d\\n",
80 PATH_MAX - strlen(pipe_name) - 1);
81 while (fscanf(fp, format, mnt, type) == 2)
82 if (strcmp(type, fstype) == 0) {
83 found = true;
84 break;
85 }
86 fclose(fp);
87
88 /* The string from fscanf() might be truncated, check mnt is valid */
89 if (found && validate_tracefs_mnt(mnt, TRACEFS_MAGIC))
90 goto exit_found;
91
92 if (block_mount)
93 return false;
94
95 p_info(fmt: "could not find tracefs, attempting to mount it now");
96 strcpy(p: mnt, q: known_mnts[0]);
97 if (mount_tracefs(target: mnt))
98 return false;
99
100exit_found:
101 strcat(p: mnt, q: pipe_name);
102 return true;
103}
104
105static void exit_tracelog(int signum)
106{
107 fclose(trace_pipe_fd);
108 free(buff);
109
110 if (json_output) {
111 jsonw_end_array(self: json_wtr);
112 jsonw_destroy(self_p: &json_wtr);
113 }
114
115 exit(0);
116}
117
118int do_tracelog(int argc, char **argv)
119{
120 const struct sigaction act = {
121 .sa_handler = exit_tracelog
122 };
123 char trace_pipe[PATH_MAX];
124 size_t buff_len = 0;
125
126 if (json_output)
127 jsonw_start_array(self: json_wtr);
128
129 if (!get_tracefs_pipe(mnt: trace_pipe))
130 return -1;
131
132 trace_pipe_fd = fopen(trace_pipe, "r");
133 if (!trace_pipe_fd) {
134 p_err(fmt: "could not open trace pipe: %s", strerror(errno));
135 return -1;
136 }
137
138 sigaction(SIGHUP, &act, NULL);
139 sigaction(SIGINT, &act, NULL);
140 sigaction(SIGTERM, &act, NULL);
141 while (1) {
142 ssize_t ret;
143
144 ret = getline(&buff, &buff_len, trace_pipe_fd);
145 if (ret <= 0) {
146 p_err(fmt: "failed to read content from trace pipe: %s",
147 strerror(errno));
148 break;
149 }
150 if (json_output)
151 jsonw_string(self: json_wtr, value: buff);
152 else
153 printf("%s", buff);
154 }
155
156 fclose(trace_pipe_fd);
157 free(buff);
158 return -1;
159}
160

source code of linux/tools/bpf/bpftool/tracelog.c