Linux Audio

Check our new training course

Loading...
Note: File does not exist in v4.10.11.
  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}