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 struct tracee {
  61         struct uloop_process proc;
  62         int in_syscall;
  63 };
  64
  65 static struct tracee tracer;
  66 static int *syscall_count;
  67 static struct blob_buf b;
  68 static int syscall_max;
  69 static int debug;
  70
  71 static int max_syscall = ARRAY_SIZE(syscall_names);
  72
  73 static void set_syscall(const char *name, int val)
  74 {
  75         int i;
  76
  77         for (i = 0; i < max_syscall; i++)
  78                 if (syscall_names[i] && !strcmp(syscall_names[i], name)) {
  79                         syscall_count[i] = val;
  80                         return;
  81                 }
  82 }
  83
  84 struct syscall {
  85         int syscall;
  86         int count;
  87 };
  88
  89 static int cmp_count(const void *a, const void *b)
  90 {
  91         return ((struct syscall*)b)->count - ((struct syscall*)a)->count;
  92 }
  93
  94 static void print_syscalls(int policy, const char *json)
  95 {
  96         void *c;
  97         int i;
  98
  99         set_syscall("rt_sigaction", 1);
 100         set_syscall("sigreturn", 1);
 101         set_syscall("rt_sigreturn", 1);
 102         set_syscall("exit_group", 1);
 103         set_syscall("exit", 1);
 104
 105         struct syscall sorted[ARRAY_SIZE(syscall_names)];
 106
 107         for (i = 0; i < ARRAY_SIZE(syscall_names); i++) {
 108                 sorted[i].syscall = i;
 109                 sorted[i].count = syscall_count[i];
 110         }
 111
 112         qsort(sorted, ARRAY_SIZE(syscall_names), sizeof(sorted[0]), cmp_count);
 113
 114         blob_buf_init(&b, 0);
 115         c = blobmsg_open_array(&b, "whitelist");
 116
 117         for (i = 0; i < ARRAY_SIZE(syscall_names); i++) {
 118                 int sc = sorted[i].syscall;
 119                 if (!sorted[i].count)
 120                         break;
 121                 if (syscall_names[sc]) {
 122                         if (debug)
 123                                 printf("syscall %d (%s) was called %d times\n",
 124                                         sc, syscall_names[sc], sorted[i].count);
 125                         blobmsg_add_string(&b, NULL, syscall_names[sc]);
 126                 } else {
 127                         ERROR("no name found for syscall(%d)\n", sc);
 128                 }
 129         }
 130         blobmsg_close_array(&b, c);
 131         blobmsg_add_u32(&b, "policy", policy);
 132         if (json) {
 133                 FILE *fp = fopen(json, "w");
 134                 if (fp) {
 135                         fprintf(fp, "%s", blobmsg_format_json_indent(b.head, true, 0));
 136                         fclose(fp);
 137                         INFO("saving syscall trace to %s\n", json);
 138                 } else {
 139                         ERROR("failed to open %s\n", json);
 140                 }
 141         } else {
 142                 printf("%s\n",
 143                         blobmsg_format_json_indent(b.head, true, 0));
 144         }
 145
 146 }
 147
 148 static void tracer_cb(struct uloop_process *c, int ret)
 149 {
 150         struct tracee *tracee = container_of(c, struct tracee, proc);
 151
 152         if (WIFSTOPPED(ret)) {
 153                 if (WSTOPSIG(ret) & 0x80) {
 154                         if (!tracee->in_syscall) {
 155                                 int syscall = ptrace(PTRACE_PEEKUSER, c->pid, reg_syscall_nr);
 156
 157                                 if (syscall < syscall_max) {
 158                                         syscall_count[syscall]++;
 159                                         if (debug)
 160                                                 fprintf(stderr, "%s()\n", syscall_names[syscall]);
 161                                 } else if (debug) {
 162                                         fprintf(stderr, "syscal(%d)\n", syscall);
 163                                 }
 164                         }
 165                         tracee->in_syscall = !tracee->in_syscall;
 166                 } else if ((ret >> 8) == (SIGTRAP | (PTRACE_EVENT_FORK << 8)) ||
 167                            (ret >> 8) == (SIGTRAP | (PTRACE_EVENT_VFORK << 8)) ||
 168                            (ret >> 8) == (SIGTRAP | (PTRACE_EVENT_CLONE << 8))) {
 169                         struct tracee *child = calloc(1, sizeof(struct tracee));
 170
 171                         ptrace(PTRACE_GETEVENTMSG, c->pid, 0, &child->proc.pid);
 172                         child->proc.cb = tracer_cb;
 173                         ptrace(PTRACE_SYSCALL, child->proc.pid, 0, 0);
 174                         uloop_process_add(&child->proc);
 175                         if (debug)
 176                                 fprintf(stderr, "Tracing new child %d\n", child->proc.pid);
 177                 }
 178         } else if (WIFEXITED(ret)) {
 179                 if (tracee == &tracer) {
 180                         uloop_end(); /* Main process exit */
 181                 } else {
 182                         if (debug)
 183                                 fprintf(stderr, "Child %d exited\n", tracee->proc.pid);
 184                         free(tracee);
 185                 }
 186                 return;
 187         }
 188
 189         ptrace(PTRACE_SYSCALL, c->pid, 0, 0);
 190         uloop_process_add(c);
 191 }
 192
 193 int main(int argc, char **argv, char **envp)
 194 {
 195         char *json = NULL;
 196         int status, ch, policy = EPERM;
 197         pid_t child;
 198
 199         while ((ch = getopt(argc, argv, "f:p:")) != -1) {
 200                 switch (ch) {
 201                 case 'f':
 202                         json = optarg;
 203                         break;
 204                 case 'p':
 205                         policy = atoi(optarg);
 206                         break;
 207                 }
 208         }
 209
 210         argc -= optind;
 211         argv += optind;
 212
 213         if (!argc)
 214                 return -1;
 215
 216         if (getenv("TRACE_DEBUG"))
 217                 debug = 1;
 218         unsetenv("TRACE_DEBUG");
 219
 220         child = fork();
 221
 222         if (child == 0) {
 223                 char **_argv = calloc(argc + 1, sizeof(char *));
 224                 char **_envp;
 225                 char *preload = "LD_PRELOAD=/lib/libpreload-trace.so";
 226                 int envc = 0;
 227                 int ret;
 228
 229                 memcpy(_argv, argv, argc * sizeof(char *));
 230
 231                 while (envp[envc++])
 232                         ;
 233
 234                 _envp = calloc(envc + 1, sizeof(char *));
 235                 memcpy(&_envp[1], envp, envc * sizeof(char *));
 236                 *_envp = preload;
 237
 238                 ret = execve(_argv[0], _argv, _envp);
 239                 ERROR("failed to exec %s: %s\n", _argv[0], strerror(errno));
 240
 241                 free(_argv);
 242                 free(_envp);
 243                 return ret;
 244         }
 245
 246         if (child < 0)
 247                 return -1;
 248
 249         syscall_max = ARRAY_SIZE(syscall_names);
 250         syscall_count = calloc(syscall_max, sizeof(int));
 251         waitpid(child, &status, 0);
 252         if (!WIFSTOPPED(status)) {
 253                 ERROR("failed to start %s\n", *argv);
 254                 return -1;
 255         }
 256
 257         ptrace(PTRACE_SETOPTIONS, child, 0,
 258                PTRACE_O_TRACESYSGOOD |
 259                PTRACE_O_TRACEFORK |
 260                PTRACE_O_TRACEVFORK |
 261                PTRACE_O_TRACECLONE);
 262         ptrace(PTRACE_SYSCALL, child, 0, 0);
 263
 264         uloop_init();
 265         tracer.proc.pid = child;
 266         tracer.proc.cb = tracer_cb;
 267         uloop_process_add(&tracer.proc);
 268         uloop_run();
 269         uloop_done();
 270
 271         if (!json)
 272                 if (asprintf(&json, "/tmp/%s.%u.json", basename(*argv), child) < 0)
 273                         ERROR("failed to allocate output path: %s\n", strerror(errno));
 274
 275         print_syscalls(policy, json);
 276
 277         return 0;
 278 }