trace/trace.c

   1 /*
   2  * Copyright (C) 2015 John Crispin <blogic@openwrt.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License version 2.1
   6  * as published by the Free Software Foundation
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #define _GNU_SOURCE
  15 #include <stddef.h>
  16 #include <sys/ptrace.h>
  17 #include <sys/user.h>
  18 #include <sys/wait.h>
  19 #include <sys/types.h>
  20 #include <unistd.h>
  21 #include <stdlib.h>
  22 #include <stdio.h>
  23 #include <errno.h>
  24 #include <string.h>
  25 #include <syslog.h>
  26
  27 #include <libubox/uloop.h>
  28 #include <libubox/blobmsg.h>
  29 #include <libubox/blobmsg_json.h>
  30
  31 #include "../syscall-names.h"
  32
  33 #define _offsetof(a, b) __builtin_offsetof(a,b)
  34 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
  35
  36 #ifdef __amd64__
  37 #define reg_syscall_nr  _offsetof(struct user, regs.orig_rax)
  38 #elif defined(__i386__)
  39 #define reg_syscall_nr  _offsetof(struct user, regs.orig_eax)
  40 #elif defined(__mips)
  41 # ifndef EF_REG2
  42 # define EF_REG2        8
  43 # endif
  44 #define reg_syscall_nr  (EF_REG2 / 4)
  45 #else
  46 #error tracing is not supported on this architecture
  47 #endif
  48
  49 #define INFO(fmt, ...) do { \
  50         fprintf(stderr, "utrace: "fmt, ## __VA_ARGS__); \
  51 } while (0)
  52
  53 #define ERROR(fmt, ...) do { \
  54         syslog(0, "utrace: "fmt, ## __VA_ARGS__); \
  55         fprintf(stderr, "utrace: "fmt, ## __VA_ARGS__); \
  56 } while (0)
  57
  58 static struct uloop_process tracer;
  59 static int *syscall_count;
  60 static struct blob_buf b;
  61 static int syscall_max;
  62 static int in_syscall;
  63 static int debug;
  64
  65 static int max_syscall = ARRAY_SIZE(syscall_names);
  66
  67 static void set_syscall(const char *name, int val)
  68 {
  69         int i;
  70
  71         for (i = 0; i < max_syscall; i++)
  72                 if (syscall_names[i] && !strcmp(syscall_names[i], name)) {
  73                         syscall_count[i] = val;
  74                         return;
  75                 }
  76 }
  77
  78 static void print_syscalls(int policy, const char *json)
  79 {
  80         void *c;
  81         int i;
  82
  83         set_syscall("rt_sigaction", 1);
  84         set_syscall("sigreturn", 1);
  85         set_syscall("rt_sigreturn", 1);
  86         set_syscall("exit_group", 1);
  87         set_syscall("exit", 1);
  88
  89         blob_buf_init(&b, 0);
  90         c = blobmsg_open_array(&b, "whitelist");
  91
  92         for (i = 0; i < ARRAY_SIZE(syscall_names); i++) {
  93                 if (!syscall_count[i])
  94                         continue;
  95                 if (syscall_names[i]) {
  96                         if (debug)
  97                                 printf("syscall %d (%s) was called %d times\n",
  98                                         i, syscall_names[i], syscall_count[i]);
  99                         blobmsg_add_string(&b, NULL, syscall_names[i]);
 100                 } else {
 101                         ERROR("no name found for syscall(%d)\n", i);
 102                 }
 103         }
 104         blobmsg_close_array(&b, c);
 105         blobmsg_add_u32(&b, "policy", policy);
 106         if (json) {
 107                 FILE *fp = fopen(json, "w");
 108                 if (fp) {
 109                         fprintf(fp, "%s", blobmsg_format_json_indent(b.head, true, 0));
 110                         fclose(fp);
 111                         INFO("saving syscall trace to %s\n", json);
 112                 } else {
 113                         ERROR("failed to open %s\n", json);
 114                 }
 115         } else {
 116                 printf("%s\n",
 117                         blobmsg_format_json_indent(b.head, true, 0));
 118         }
 119
 120 }
 121
 122 static void tracer_cb(struct uloop_process *c, int ret)
 123 {
 124         if (WIFSTOPPED(ret) && WSTOPSIG(ret) & 0x80) {
 125                 if (!in_syscall) {
 126                         int syscall = ptrace(PTRACE_PEEKUSER, c->pid, reg_syscall_nr);
 127
 128                         if (syscall < syscall_max) {
 129                                 syscall_count[syscall]++;
 130                                 if (debug)
 131                                         fprintf(stderr, "%s()\n", syscall_names[syscall]);
 132                         } else if (debug) {
 133                                 fprintf(stderr, "syscal(%d)\n", syscall);
 134                         }
 135                 }
 136                 in_syscall = !in_syscall;
 137         } else if (WIFEXITED(ret)) {
 138                 uloop_end();
 139                 return;
 140         }
 141         ptrace(PTRACE_SYSCALL, c->pid, 0, 0);
 142         uloop_process_add(&tracer);
 143 }
 144
 145 int main(int argc, char **argv, char **envp)
 146 {
 147         char *json = NULL;
 148         int status, ch, policy = EPERM;
 149         pid_t child;
 150
 151         while ((ch = getopt(argc, argv, "f:p:")) != -1) {
 152                 switch (ch) {
 153                 case 'f':
 154                         json = optarg;
 155                         break;
 156                 case 'p':
 157                         policy = atoi(optarg);
 158                         break;
 159                 }
 160         }
 161
 162         argc -= optind;
 163         argv += optind;
 164
 165         if (!argc)
 166                 return -1;
 167
 168         if (getenv("TRACE_DEBUG"))
 169                 debug = 1;
 170         unsetenv("TRACE_DEBUG");
 171
 172         child = fork();
 173
 174         if (child == 0) {
 175                 char **_argv = calloc(argc + 1, sizeof(char *));
 176                 char **_envp;
 177                 char preload[] = "LD_PRELOAD=/lib/libpreload-trace.so";
 178                 int envc = 1;
 179                 int ret;
 180
 181                 memcpy(_argv, argv, argc * sizeof(char *));
 182
 183                 while (envp[envc++])
 184                         ;
 185
 186                 _envp = calloc(envc, sizeof(char *));
 187                 memcpy(&_envp[1], _envp, envc * sizeof(char *));
 188                 *envp = preload;
 189
 190                 ret = execve(_argv[0], _argv, envp);
 191                 ERROR("failed to exec %s: %s\n", _argv[0], strerror(errno));
 192                 return ret;
 193         }
 194
 195         if (child < 0)
 196                 return -1;
 197
 198         syscall_max = ARRAY_SIZE(syscall_names);
 199         syscall_count = calloc(syscall_max, sizeof(int));
 200         waitpid(child, &status, 0);
 201         if (!WIFSTOPPED(status)) {
 202                 ERROR("failed to start %s\n", *argv);
 203                 return -1;
 204         }
 205
 206         ptrace(PTRACE_SETOPTIONS, child, 0, PTRACE_O_TRACESYSGOOD);
 207         ptrace(PTRACE_SYSCALL, child, 0, 0);
 208
 209         uloop_init();
 210         tracer.pid = child;
 211         tracer.cb = tracer_cb;
 212         uloop_process_add(&tracer);
 213         uloop_run();
 214         uloop_done();
 215
 216         if (!json)
 217                 if (asprintf(&json, "/tmp/%s.%u.json", basename(*argv), child) < 0)
 218                         ERROR("failed to allocate output path: %s\n", strerror(errno));
 219
 220         print_syscalls(policy, json);
 221
 222         return 0;
 223 }