tracelog.c

  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/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, *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(format, sizeof(format), "%%*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("could not find tracefs, attempting to mount it now");
 96	strcpy(mnt, known_mnts[0]);
 97	if (mount_tracefs(mnt))
 98		return false;
 99
100exit_found:
101	strcat(mnt, 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(json_wtr);
112		jsonw_destroy(&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(json_wtr);
128
129	if (!get_tracefs_pipe(trace_pipe))
130		return -1;
131
132	trace_pipe_fd = fopen(trace_pipe, "r");
133	if (!trace_pipe_fd) {
134		p_err("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("failed to read content from trace pipe: %s",
147			      strerror(errno));
148			break;
149		}
150		if (json_output)
151			jsonw_string(json_wtr, buff);
152		else
153			printf("%s", buff);
154	}
155
156	fclose(trace_pipe_fd);
157	free(buff);
158	return -1;
159}