167 lines · 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_MAGIC18# define TRACEFS_MAGIC 0x7472616319#endif20 21#define _textify(x) #x22#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 bool40find_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 at99 * /sys/kernel/debug/tracing when we try to access it. If we could not100 * find it, it is likely that debugfs is not mounted. Let's give one101 * 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_tracelog129 };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 else160 printf("%s", buff);161 }162 163 fclose(trace_pipe_fd);164 free(buff);165 return -1;166}167