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 #ifndef PTRACE_EVENT_STOP
  28 /* PTRACE_EVENT_STOP is defined in linux/ptrace.h, but this header
  29  * collides with musl's sys/ptrace.h */
  30 #define PTRACE_EVENT_STOP 128
  31 #endif
  32
  33 #include <libubox/uloop.h>
  34 #include <libubox/blobmsg.h>
  35 #include <libubox/blobmsg_json.h>
  36
  37 #include "../syscall-names.h"
  38
  39 #define _offsetof(a, b) __builtin_offsetof(a,b)
  40 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
  41
  42 #ifdef __amd64__
  43 #define reg_syscall_nr  _offsetof(struct user, regs.orig_rax)
  44 #elif defined(__i386__)
  45 #define reg_syscall_nr  _offsetof(struct user, regs.orig_eax)
  46 #elif defined(__mips)
  47 # ifndef EF_REG2
  48 # define EF_REG2        8
  49 # endif
  50 #define reg_syscall_nr  (EF_REG2 / 4)
  51 #elif defined(__arm__)
  52 #define reg_syscall_nr  _offsetof(struct user, regs.uregs[7])
  53 #else
  54 #error tracing is not supported on this architecture
  55 #endif
  56
  57 #define INFO(fmt, ...) do { \
  58         fprintf(stderr, "utrace: "fmt, ## __VA_ARGS__); \
  59 } while (0)
  60
  61 #define ERROR(fmt, ...) do { \
  62         syslog(LOG_ERR, "utrace: "fmt, ## __VA_ARGS__); \
  63         fprintf(stderr, "utrace: "fmt, ## __VA_ARGS__); \
  64 } while (0)
  65
  66 struct tracee {
  67         struct uloop_process proc;
  68         int in_syscall;
  69 };
  70
  71 static struct tracee tracer;
  72 static int *syscall_count;
  73 static struct blob_buf b;
  74 static int syscall_max;
  75 static int debug;
  76
  77 static int max_syscall = ARRAY_SIZE(syscall_names);
  78
  79 static void set_syscall(const char *name, int val)
  80 {
  81         int i;
  82
  83         for (i = 0; i < max_syscall; i++)
  84                 if (syscall_names[i] && !strcmp(syscall_names[i], name)) {
  85                         syscall_count[i] = val;
  86                         return;
  87                 }
  88 }
  89
  90 struct syscall {
  91         int syscall;
  92         int count;
  93 };
  94
  95 static int cmp_count(const void *a, const void *b)
  96 {
  97         return ((struct syscall*)b)->count - ((struct syscall*)a)->count;
  98 }
  99
 100 static void print_syscalls(int policy, const char *json)
 101 {
 102         void *c;
 103         int i;
 104
 105         set_syscall("rt_sigaction", 1);
 106         set_syscall("sigreturn", 1);
 107         set_syscall("rt_sigreturn", 1);
 108         set_syscall("exit_group", 1);
 109         set_syscall("exit", 1);
 110
 111         struct syscall sorted[ARRAY_SIZE(syscall_names)];
 112
 113         for (i = 0; i < ARRAY_SIZE(syscall_names); i++) {
 114                 sorted[i].syscall = i;
 115                 sorted[i].count = syscall_count[i];
 116         }
 117
 118         qsort(sorted, ARRAY_SIZE(syscall_names), sizeof(sorted[0]), cmp_count);
 119
 120         blob_buf_init(&b, 0);
 121         c = blobmsg_open_array(&b, "whitelist");
 122
 123         for (i = 0; i < ARRAY_SIZE(syscall_names); i++) {
 124                 int sc = sorted[i].syscall;
 125                 if (!sorted[i].count)
 126                         break;
 127                 if (syscall_names[sc]) {
 128                         if (debug)
 129                                 printf("syscall %d (%s) was called %d times\n",
 130                                         sc, syscall_names[sc], sorted[i].count);
 131                         blobmsg_add_string(&b, NULL, syscall_names[sc]);
 132                 } else {
 133                         ERROR("no name found for syscall(%d)\n", sc);
 134                 }
 135         }
 136         blobmsg_close_array(&b, c);
 137         blobmsg_add_u32(&b, "policy", policy);
 138         if (json) {
 139                 FILE *fp = fopen(json, "w");
 140                 if (fp) {
 141                         fprintf(fp, "%s", blobmsg_format_json_indent(b.head, true, 0));
 142                         fclose(fp);
 143                         INFO("saving syscall trace to %s\n", json);
 144                 } else {
 145                         ERROR("failed to open %s\n", json);
 146                 }
 147         } else {
 148                 printf("%s\n",
 149                         blobmsg_format_json_indent(b.head, true, 0));
 150         }
 151
 152 }
 153
 154 static void tracer_cb(struct uloop_process *c, int ret)
 155 {
 156         struct tracee *tracee = container_of(c, struct tracee, proc);
 157         int inject_signal = 0;
 158
 159         /* We explicitely check for events in upper 16 bits, because
 160          * musl (as opposed to glibc) does not report
 161          * PTRACE_EVENT_STOP as WIFSTOPPED */
 162         if (WIFSTOPPED(ret) || (ret >> 16)) {
 163                 if (WSTOPSIG(ret) & 0x80) {
 164                         if (!tracee->in_syscall) {
 165                                 int syscall = ptrace(PTRACE_PEEKUSER, c->pid, reg_syscall_nr);
 166
 167                                 if (syscall < syscall_max) {
 168                                         syscall_count[syscall]++;
 169                                         if (debug)
 170                                                 fprintf(stderr, "%s()\n", syscall_names[syscall]);
 171                                 } else if (debug) {
 172                                         fprintf(stderr, "syscal(%d)\n", syscall);
 173                                 }
 174                         }
 175                         tracee->in_syscall = !tracee->in_syscall;
 176                 } else if ((ret >> 8) == (SIGTRAP | (PTRACE_EVENT_FORK << 8)) ||
 177                            (ret >> 8) == (SIGTRAP | (PTRACE_EVENT_VFORK << 8)) ||
 178                            (ret >> 8) == (SIGTRAP | (PTRACE_EVENT_CLONE << 8))) {
 179                         struct tracee *child = calloc(1, sizeof(struct tracee));
 180
 181                         ptrace(PTRACE_GETEVENTMSG, c->pid, 0, &child->proc.pid);
 182                         child->proc.cb = tracer_cb;
 183                         ptrace(PTRACE_SYSCALL, child->proc.pid, 0, 0);
 184                         uloop_process_add(&child->proc);
 185                         if (debug)
 186                                 fprintf(stderr, "Tracing new child %d\n", child->proc.pid);
 187                 } else if ((ret >> 16) == PTRACE_EVENT_STOP) {
 188                         /* Nothing special to do here */
 189                 } else {
 190                         inject_signal = WSTOPSIG(ret);
 191                         if (debug)
 192                                 fprintf(stderr, "Injecting signal %d into pid %d\n",
 193                                         inject_signal, tracee->proc.pid);
 194                 }
 195         } else if (WIFEXITED(ret) || (WIFSIGNALED(ret) && WTERMSIG(ret))) {
 196                 if (tracee == &tracer) {
 197                         uloop_end(); /* Main process exit */
 198                 } else {
 199                         if (debug)
 200                                 fprintf(stderr, "Child %d exited\n", tracee->proc.pid);
 201                         free(tracee);
 202                 }
 203                 return;
 204         }
 205
 206         ptrace(PTRACE_SYSCALL, c->pid, 0, inject_signal);
 207         uloop_process_add(c);
 208 }
 209
 210 int main(int argc, char **argv, char **envp)
 211 {
 212         char *json = NULL;
 213         int status, ch, policy = EPERM;
 214         pid_t child;
 215
 216         while ((ch = getopt(argc, argv, "f:p:")) != -1) {
 217                 switch (ch) {
 218                 case 'f':
 219                         json = optarg;
 220                         break;
 221                 case 'p':
 222                         policy = atoi(optarg);
 223                         break;
 224                 }
 225         }
 226
 227         argc -= optind;
 228         argv += optind;
 229
 230         if (!argc)
 231                 return -1;
 232
 233         if (getenv("TRACE_DEBUG"))
 234                 debug = 1;
 235         unsetenv("TRACE_DEBUG");
 236
 237         child = fork();
 238
 239         if (child == 0) {
 240                 char **_argv = calloc(argc + 1, sizeof(char *));
 241                 char **_envp;
 242                 char *preload = "LD_PRELOAD=/lib/libpreload-trace.so";
 243                 int envc = 0;
 244                 int ret;
 245
 246                 memcpy(_argv, argv, argc * sizeof(char *));
 247
 248                 while (envp[envc++])
 249                         ;
 250
 251                 _envp = calloc(envc + 1, sizeof(char *));
 252                 memcpy(&_envp[1], envp, envc * sizeof(char *));
 253                 *_envp = preload;
 254
 255                 ret = execve(_argv[0], _argv, _envp);
 256                 ERROR("failed to exec %s: %s\n", _argv[0], strerror(errno));
 257
 258                 free(_argv);
 259                 free(_envp);
 260                 return ret;
 261         }
 262
 263         if (child < 0)
 264                 return -1;
 265
 266         syscall_max = ARRAY_SIZE(syscall_names);
 267         syscall_count = calloc(syscall_max, sizeof(int));
 268         waitpid(child, &status, WUNTRACED);
 269         if (!WIFSTOPPED(status)) {
 270                 ERROR("failed to start %s\n", *argv);
 271                 return -1;
 272         }
 273
 274         ptrace(PTRACE_SEIZE, child, 0,
 275                PTRACE_O_TRACESYSGOOD |
 276                PTRACE_O_TRACEFORK |
 277                PTRACE_O_TRACEVFORK |
 278                PTRACE_O_TRACECLONE);
 279         ptrace(PTRACE_SYSCALL, child, 0, SIGCONT);
 280
 281         uloop_init();
 282         tracer.proc.pid = child;
 283         tracer.proc.cb = tracer_cb;
 284         uloop_process_add(&tracer.proc);
 285         uloop_run();
 286         uloop_done();
 287
 288         if (!json)
 289                 if (asprintf(&json, "/tmp/%s.%u.json", basename(*argv), child) < 0)
 290                         ERROR("failed to allocate output path: %s\n", strerror(errno));
 291
 292         print_syscalls(policy, json);
 293
 294         return 0;
 295 }