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 #include <limits.h>
  27
  28 #include <libubox/uloop.h>
  29 #include <libubox/blobmsg.h>
  30 #include <libubox/blobmsg_json.h>
  31
  32 #include "../syscall-names.h"
  33
  34 #define _offsetof(a, b) __builtin_offsetof(a,b)
  35 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
  36
  37 #ifdef __amd64__
  38 #define reg_syscall_nr  _offsetof(struct user, regs.orig_rax)
  39 #elif defined(__i386__)
  40 #define reg_syscall_nr  _offsetof(struct user, regs.orig_eax)
  41 #elif defined(__mips)
  42 # ifndef EF_REG2
  43 # define EF_REG2        8
  44 # endif
  45 #define reg_syscall_nr  (EF_REG2 / 4)
  46 #elif defined(__arm__)
  47 #define reg_syscall_nr  _offsetof(struct user, regs.uregs[7])
  48 #else
  49 #error tracing is not supported on this architecture
  50 #endif
  51
  52 #define INFO(fmt, ...) do { \
  53         fprintf(stderr, "utrace: "fmt, ## __VA_ARGS__); \
  54 } while (0)
  55
  56 #define ERROR(fmt, ...) do { \
  57         syslog(LOG_ERR, "utrace: "fmt, ## __VA_ARGS__); \
  58         fprintf(stderr, "utrace: "fmt, ## __VA_ARGS__); \
  59 } while (0)
  60
  61 static struct uloop_process tracer;
  62 static int *syscall_count;
  63 static struct blob_buf b;
  64 static int syscall_max;
  65 static int in_syscall;
  66 static int debug;
  67
  68 static int max_syscall = ARRAY_SIZE(syscall_names);
  69
  70 static void set_syscall(const char *name, int val)
  71 {
  72         int i;
  73
  74         for (i = 0; i < max_syscall; i++)
  75                 if (syscall_names[i] && !strcmp(syscall_names[i], name)) {
  76                         syscall_count[i] = val;
  77                         return;
  78                 }
  79 }
  80
  81 static void print_syscalls(int policy, const char *json)
  82 {
  83         void *c;
  84         int i;
  85
  86         set_syscall("rt_sigaction", 1);
  87         set_syscall("sigreturn", 1);
  88         set_syscall("rt_sigreturn", 1);
  89         set_syscall("exit_group", 1);
  90         set_syscall("exit", 1);
  91
  92         blob_buf_init(&b, 0);
  93         c = blobmsg_open_array(&b, "whitelist");
  94
  95         for (i = 0; i < ARRAY_SIZE(syscall_names); i++) {
  96                 if (!syscall_count[i])
  97                         continue;
  98                 if (syscall_names[i]) {
  99                         if (debug)
 100                                 printf("syscall %d (%s) was called %d times\n",
 101                                         i, syscall_names[i], syscall_count[i]);
 102                         blobmsg_add_string(&b, NULL, syscall_names[i]);
 103                 } else {
 104                         ERROR("no name found for syscall(%d)\n", i);
 105                 }
 106         }
 107         blobmsg_close_array(&b, c);
 108         blobmsg_add_u32(&b, "policy", policy);
 109         if (json) {
 110                 FILE *fp = fopen(json, "w");
 111                 if (fp) {
 112                         fprintf(fp, "%s", blobmsg_format_json_indent(b.head, true, 0));
 113                         fclose(fp);
 114                         INFO("saving syscall trace to %s\n", json);
 115                 } else {
 116                         ERROR("failed to open %s\n", json);
 117                 }
 118         } else {
 119                 printf("%s\n",
 120                         blobmsg_format_json_indent(b.head, true, 0));
 121         }
 122
 123 }
 124
 125 static void tracer_cb(struct uloop_process *c, int ret)
 126 {
 127         if (WIFSTOPPED(ret) && WSTOPSIG(ret) & 0x80) {
 128                 if (!in_syscall) {
 129                         int syscall = ptrace(PTRACE_PEEKUSER, c->pid, reg_syscall_nr);
 130
 131                         if (syscall < syscall_max) {
 132                                 syscall_count[syscall]++;
 133                                 if (debug)
 134                                         fprintf(stderr, "%s()\n", syscall_names[syscall]);
 135                         } else if (debug) {
 136                                 fprintf(stderr, "syscal(%d)\n", syscall);
 137                         }
 138                 }
 139                 in_syscall = !in_syscall;
 140         } else if (WIFEXITED(ret)) {
 141                 uloop_end();
 142                 return;
 143         }
 144         ptrace(PTRACE_SYSCALL, c->pid, 0, 0);
 145         uloop_process_add(&tracer);
 146 }
 147
 148 int main(int argc, char **argv, char **envp)
 149 {
 150         char *json = NULL;
 151         int status, ch, policy = EPERM;
 152         pid_t child;
 153
 154         while ((ch = getopt(argc, argv, "f:p:")) != -1) {
 155                 switch (ch) {
 156                 case 'f':
 157                         json = optarg;
 158                         break;
 159                 case 'p':
 160                         policy = atoi(optarg);
 161                         break;
 162                 }
 163         }
 164
 165         argc -= optind;
 166         argv += optind;
 167
 168         if (!argc)
 169                 return -1;
 170
 171         if (getenv("TRACE_DEBUG"))
 172                 debug = 1;
 173         unsetenv("TRACE_DEBUG");
 174
 175         child = fork();
 176
 177         if (child == 0) {
 178                 char **_argv = calloc(argc + 1, sizeof(char *));
 179                 char **_envp;
 180                 char *preload = "LD_PRELOAD=/lib/libpreload-trace.so";
 181                 int envc = 1;
 182                 int ret;
 183
 184                 memcpy(_argv, argv, argc * sizeof(char *));
 185
 186                 while (envp[envc++])
 187                         ;
 188
 189                 _envp = calloc(envc, sizeof(char *));
 190                 memcpy(&_envp[1], _envp, envc * sizeof(char *));
 191                 *_envp = preload;
 192
 193                 ret = execve(_argv[0], _argv, _envp);
 194                 ERROR("failed to exec %s: %s\n", _argv[0], strerror(errno));
 195
 196                 free(_argv);
 197                 free(_envp);
 198                 return ret;
 199         }
 200
 201         if (child < 0)
 202                 return -1;
 203
 204         syscall_max = ARRAY_SIZE(syscall_names);
 205         syscall_count = calloc(syscall_max, sizeof(int));
 206         waitpid(child, &status, 0);
 207         if (!WIFSTOPPED(status)) {
 208                 ERROR("failed to start %s\n", *argv);
 209                 return -1;
 210         }
 211
 212         ptrace(PTRACE_SETOPTIONS, child, 0, PTRACE_O_TRACESYSGOOD);
 213         ptrace(PTRACE_SYSCALL, child, 0, 0);
 214
 215         uloop_init();
 216         tracer.pid = child;
 217         tracer.cb = tracer_cb;
 218         uloop_process_add(&tracer);
 219         uloop_run();
 220         uloop_done();
 221
 222         if (!json)
 223                 if (asprintf(&json, "/tmp/%s.%u.json", basename(*argv), child) < 0)
 224                         ERROR("failed to allocate output path: %s\n", strerror(errno));
 225
 226         print_syscalls(policy, json);
 227
 228         return 0;
 229 }