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/types.h>
  18 #include <sys/user.h>
  19 #include <sys/wait.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 #elif defined(__arm__)
  46 #define reg_syscall_nr  _offsetof(struct user, regs.uregs[7])
  47 #else
  48 #error tracing is not supported on this architecture
  49 #endif
  50
  51 #define INFO(fmt, ...) do { \
  52         fprintf(stderr, "utrace: "fmt, ## __VA_ARGS__); \
  53 } while (0)
  54
  55 #define ERROR(fmt, ...) do { \
  56         syslog(LOG_ERR, "utrace: "fmt, ## __VA_ARGS__); \
  57         fprintf(stderr, "utrace: "fmt, ## __VA_ARGS__); \
  58 } while (0)
  59
  60 static struct uloop_process tracer;
  61 static int *syscall_count;
  62 static struct blob_buf b;
  63 static int syscall_max;
  64 static int in_syscall;
  65 static int debug;
  66
  67 static int max_syscall = ARRAY_SIZE(syscall_names);
  68
  69 static void set_syscall(const char *name, int val)
  70 {
  71         int i;
  72
  73         for (i = 0; i < max_syscall; i++)
  74                 if (syscall_names[i] && !strcmp(syscall_names[i], name)) {
  75                         syscall_count[i] = val;
  76                         return;
  77                 }
  78 }
  79
  80 static void print_syscalls(int policy, const char *json)
  81 {
  82         void *c;
  83         int i;
  84
  85         set_syscall("rt_sigaction", 1);
  86         set_syscall("sigreturn", 1);
  87         set_syscall("rt_sigreturn", 1);
  88         set_syscall("exit_group", 1);
  89         set_syscall("exit", 1);
  90
  91         blob_buf_init(&b, 0);
  92         c = blobmsg_open_array(&b, "whitelist");
  93
  94         for (i = 0; i < ARRAY_SIZE(syscall_names); i++) {
  95                 if (!syscall_count[i])
  96                         continue;
  97                 if (syscall_names[i]) {
  98                         if (debug)
  99                                 printf("syscall %d (%s) was called %d times\n",
 100                                         i, syscall_names[i], syscall_count[i]);
 101                         blobmsg_add_string(&b, NULL, syscall_names[i]);
 102                 } else {
 103                         ERROR("no name found for syscall(%d)\n", i);
 104                 }
 105         }
 106         blobmsg_close_array(&b, c);
 107         blobmsg_add_u32(&b, "policy", policy);
 108         if (json) {
 109                 FILE *fp = fopen(json, "w");
 110                 if (fp) {
 111                         fprintf(fp, "%s", blobmsg_format_json_indent(b.head, true, 0));
 112                         fclose(fp);
 113                         INFO("saving syscall trace to %s\n", json);
 114                 } else {
 115                         ERROR("failed to open %s\n", json);
 116                 }
 117         } else {
 118                 printf("%s\n",
 119                         blobmsg_format_json_indent(b.head, true, 0));
 120         }
 121
 122 }
 123
 124 static void tracer_cb(struct uloop_process *c, int ret)
 125 {
 126         if (WIFSTOPPED(ret) && WSTOPSIG(ret) & 0x80) {
 127                 if (!in_syscall) {
 128                         int syscall = ptrace(PTRACE_PEEKUSER, c->pid, reg_syscall_nr);
 129
 130                         if (syscall < syscall_max) {
 131                                 syscall_count[syscall]++;
 132                                 if (debug)
 133                                         fprintf(stderr, "%s()\n", syscall_names[syscall]);
 134                         } else if (debug) {
 135                                 fprintf(stderr, "syscal(%d)\n", syscall);
 136                         }
 137                 }
 138                 in_syscall = !in_syscall;
 139         } else if (WIFEXITED(ret)) {
 140                 uloop_end();
 141                 return;
 142         }
 143         ptrace(PTRACE_SYSCALL, c->pid, 0, 0);
 144         uloop_process_add(&tracer);
 145 }
 146
 147 int main(int argc, char **argv, char **envp)
 148 {
 149         char *json = NULL;
 150         int status, ch, policy = EPERM;
 151         pid_t child;
 152
 153         while ((ch = getopt(argc, argv, "f:p:")) != -1) {
 154                 switch (ch) {
 155                 case 'f':
 156                         json = optarg;
 157                         break;
 158                 case 'p':
 159                         policy = atoi(optarg);
 160                         break;
 161                 }
 162         }
 163
 164         argc -= optind;
 165         argv += optind;
 166
 167         if (!argc)
 168                 return -1;
 169
 170         if (getenv("TRACE_DEBUG"))
 171                 debug = 1;
 172         unsetenv("TRACE_DEBUG");
 173
 174         child = fork();
 175
 176         if (child == 0) {
 177                 char **_argv = calloc(argc + 1, sizeof(char *));
 178                 char **_envp;
 179                 char *preload = "LD_PRELOAD=/lib/libpreload-trace.so";
 180                 int envc = 1;
 181                 int ret;
 182
 183                 memcpy(_argv, argv, argc * sizeof(char *));
 184
 185                 while (envp[envc++])
 186                         ;
 187
 188                 _envp = calloc(envc, sizeof(char *));
 189                 memcpy(&_envp[1], _envp, envc * sizeof(char *));
 190                 *_envp = preload;
 191
 192                 ret = execve(_argv[0], _argv, _envp);
 193                 ERROR("failed to exec %s: %s\n", _argv[0], strerror(errno));
 194
 195                 free(_argv);
 196                 free(_envp);
 197                 return ret;
 198         }
 199
 200         if (child < 0)
 201                 return -1;
 202
 203         syscall_max = ARRAY_SIZE(syscall_names);
 204         syscall_count = calloc(syscall_max, sizeof(int));
 205         waitpid(child, &status, 0);
 206         if (!WIFSTOPPED(status)) {
 207                 ERROR("failed to start %s\n", *argv);
 208                 return -1;
 209         }
 210
 211         ptrace(PTRACE_SETOPTIONS, child, 0, PTRACE_O_TRACESYSGOOD);
 212         ptrace(PTRACE_SYSCALL, child, 0, 0);
 213
 214         uloop_init();
 215         tracer.pid = child;
 216         tracer.cb = tracer_cb;
 217         uloop_process_add(&tracer);
 218         uloop_run();
 219         uloop_done();
 220
 221         if (!json)
 222                 if (asprintf(&json, "/tmp/%s.%u.json", basename(*argv), child) < 0)
 223                         ERROR("failed to allocate output path: %s\n", strerror(errno));
 224
 225         print_syscalls(policy, json);
 226
 227         return 0;
 228 }