liblttng-ust-fork/ustfork.c

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2009  Pierre-Marc Fournier
   5  * Copyright (C) 2011-2012  Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   6  */
   7
   8 #include <lttng/ust-dlfcn.h>
   9 #include <unistd.h>
  10 #include <stdio.h>
  11 #include <signal.h>
  12 #include <sched.h>
  13 #include <stdarg.h>
  14 #include <errno.h>
  15
  16 #include <lttng/ust.h>
  17
  18 pid_t fork(void)
  19 {
  20         static pid_t (*plibc_func)(void) = NULL;
  21         sigset_t sigset;
  22         pid_t retval;
  23         int saved_errno;
  24
  25         if (plibc_func == NULL) {
  26                 plibc_func = dlsym(RTLD_NEXT, "fork");
  27                 if (plibc_func == NULL) {
  28                         fprintf(stderr, "libustfork: unable to find \"fork\" symbol\n");
  29                         errno = ENOSYS;
  30                         return -1;
  31                 }
  32         }
  33
  34         ust_before_fork(&sigset);
  35         /* Do the real fork */
  36         retval = plibc_func();
  37         saved_errno = errno;
  38         if (retval == 0) {
  39                 /* child */
  40                 ust_after_fork_child(&sigset);
  41         } else {
  42                 ust_after_fork_parent(&sigset);
  43         }
  44         errno = saved_errno;
  45         return retval;
  46 }
  47
  48 int daemon(int nochdir, int noclose)
  49 {
  50         static int (*plibc_func)(int nochdir, int noclose) = NULL;
  51         sigset_t sigset;
  52         int retval;
  53         int saved_errno;
  54
  55         if (plibc_func == NULL) {
  56                 plibc_func = dlsym(RTLD_NEXT, "daemon");
  57                 if (plibc_func == NULL) {
  58                         fprintf(stderr, "libustfork: unable to find \"daemon\" symbol\n");
  59                         errno = ENOSYS;
  60                         return -1;
  61                 }
  62         }
  63
  64         ust_before_fork(&sigset);
  65         /* Do the real daemon call */
  66         retval = plibc_func(nochdir, noclose);
  67         saved_errno = errno;
  68         if (retval == 0) {
  69                 /* child, parent called _exit() directly */
  70                 ust_after_fork_child(&sigset);
  71         } else {
  72                 /* on error in the parent */
  73                 ust_after_fork_parent(&sigset);
  74         }
  75         errno = saved_errno;
  76         return retval;
  77 }
  78
  79 int setuid(uid_t uid)
  80 {
  81         static int (*plibc_func)(uid_t uid) = NULL;
  82         int retval;
  83         int saved_errno;
  84
  85         if (plibc_func == NULL) {
  86                 plibc_func = dlsym(RTLD_NEXT, "setuid");
  87                 if (plibc_func == NULL) {
  88                         fprintf(stderr, "libustfork: unable to find \"setuid\" symbol\n");
  89                         errno = ENOSYS;
  90                         return -1;
  91                 }
  92         }
  93
  94         /* Do the real setuid */
  95         retval = plibc_func(uid);
  96         saved_errno = errno;
  97
  98         ust_after_setuid();
  99
 100         errno = saved_errno;
 101         return retval;
 102 }
 103
 104 int setgid(gid_t gid)
 105 {
 106         static int (*plibc_func)(gid_t gid) = NULL;
 107         int retval;
 108         int saved_errno;
 109
 110         if (plibc_func == NULL) {
 111                 plibc_func = dlsym(RTLD_NEXT, "setgid");
 112                 if (plibc_func == NULL) {
 113                         fprintf(stderr, "libustfork: unable to find \"setgid\" symbol\n");
 114                         errno = ENOSYS;
 115                         return -1;
 116                 }
 117         }
 118
 119         /* Do the real setgid */
 120         retval = plibc_func(gid);
 121         saved_errno = errno;
 122
 123         ust_after_setgid();
 124
 125         errno = saved_errno;
 126         return retval;
 127 }
 128
 129 int seteuid(uid_t euid)
 130 {
 131         static int (*plibc_func)(uid_t euid) = NULL;
 132         int retval;
 133         int saved_errno;
 134
 135         if (plibc_func == NULL) {
 136                 plibc_func = dlsym(RTLD_NEXT, "seteuid");
 137                 if (plibc_func == NULL) {
 138                         fprintf(stderr, "libustfork: unable to find \"seteuid\" symbol\n");
 139                         errno = ENOSYS;
 140                         return -1;
 141                 }
 142         }
 143
 144         /* Do the real seteuid */
 145         retval = plibc_func(euid);
 146         saved_errno = errno;
 147
 148         ust_after_seteuid();
 149
 150         errno = saved_errno;
 151         return retval;
 152 }
 153
 154 int setegid(gid_t egid)
 155 {
 156         static int (*plibc_func)(gid_t egid) = NULL;
 157         int retval;
 158         int saved_errno;
 159
 160         if (plibc_func == NULL) {
 161                 plibc_func = dlsym(RTLD_NEXT, "setegid");
 162                 if (plibc_func == NULL) {
 163                         fprintf(stderr, "libustfork: unable to find \"setegid\" symbol\n");
 164                         errno = ENOSYS;
 165                         return -1;
 166                 }
 167         }
 168
 169         /* Do the real setegid */
 170         retval = plibc_func(egid);
 171         saved_errno = errno;
 172
 173         ust_after_setegid();
 174
 175         errno = saved_errno;
 176         return retval;
 177 }
 178
 179 int setreuid(uid_t ruid, uid_t euid)
 180 {
 181         static int (*plibc_func)(uid_t ruid, uid_t euid) = NULL;
 182         int retval;
 183         int saved_errno;
 184
 185         if (plibc_func == NULL) {
 186                 plibc_func = dlsym(RTLD_NEXT, "setreuid");
 187                 if (plibc_func == NULL) {
 188                         fprintf(stderr, "libustfork: unable to find \"setreuid\" symbol\n");
 189                         errno = ENOSYS;
 190                         return -1;
 191                 }
 192         }
 193
 194         /* Do the real setreuid */
 195         retval = plibc_func(ruid, euid);
 196         saved_errno = errno;
 197
 198         ust_after_setreuid();
 199
 200         errno = saved_errno;
 201         return retval;
 202 }
 203
 204 int setregid(gid_t rgid, gid_t egid)
 205 {
 206         static int (*plibc_func)(gid_t rgid, gid_t egid) = NULL;
 207         int retval;
 208         int saved_errno;
 209
 210         if (plibc_func == NULL) {
 211                 plibc_func = dlsym(RTLD_NEXT, "setregid");
 212                 if (plibc_func == NULL) {
 213                         fprintf(stderr, "libustfork: unable to find \"setregid\" symbol\n");
 214                         errno = ENOSYS;
 215                         return -1;
 216                 }
 217         }
 218
 219         /* Do the real setregid */
 220         retval = plibc_func(rgid, egid);
 221         saved_errno = errno;
 222
 223         ust_after_setregid();
 224
 225         errno = saved_errno;
 226         return retval;
 227 }
 228
 229 #ifdef __linux__
 230
 231 struct user_desc;
 232
 233 struct ustfork_clone_info {
 234         int (*fn)(void *);
 235         void *arg;
 236         sigset_t sigset;
 237 };
 238
 239 static int clone_fn(void *arg)
 240 {
 241         struct ustfork_clone_info *info = (struct ustfork_clone_info *) arg;
 242
 243         /* clone is now done and we are in child */
 244         ust_after_fork_child(&info->sigset);
 245         return info->fn(info->arg);
 246 }
 247
 248 int clone(int (*fn)(void *), void *child_stack, int flags, void *arg, ...)
 249 {
 250         static int (*plibc_func)(int (*fn)(void *), void *child_stack,
 251                         int flags, void *arg, pid_t *ptid,
 252                         struct user_desc *tls, pid_t *ctid) = NULL;
 253         /* var args */
 254         pid_t *ptid;
 255         struct user_desc *tls;
 256         pid_t *ctid;
 257         /* end of var args */
 258         va_list ap;
 259         int retval;
 260         int saved_errno;
 261
 262         va_start(ap, arg);
 263         ptid = va_arg(ap, pid_t *);
 264         tls = va_arg(ap, struct user_desc *);
 265         ctid = va_arg(ap, pid_t *);
 266         va_end(ap);
 267
 268         if (plibc_func == NULL) {
 269                 plibc_func = dlsym(RTLD_NEXT, "clone");
 270                 if (plibc_func == NULL) {
 271                         fprintf(stderr, "libustfork: unable to find \"clone\" symbol.\n");
 272                         errno = ENOSYS;
 273                         return -1;
 274                 }
 275         }
 276
 277         if (flags & CLONE_VM) {
 278                 /*
 279                  * Creating a thread, no need to intervene, just pass on
 280                  * the arguments.
 281                  */
 282                 retval = plibc_func(fn, child_stack, flags, arg, ptid,
 283                                 tls, ctid);
 284                 saved_errno = errno;
 285         } else {
 286                 /* Creating a real process, we need to intervene. */
 287                 struct ustfork_clone_info info = { .fn = fn, .arg = arg };
 288
 289                 ust_before_fork(&info.sigset);
 290                 retval = plibc_func(clone_fn, child_stack, flags, &info,
 291                                 ptid, tls, ctid);
 292                 saved_errno = errno;
 293                 /* The child doesn't get here. */
 294                 ust_after_fork_parent(&info.sigset);
 295         }
 296         errno = saved_errno;
 297         return retval;
 298 }
 299
 300 int setns(int fd, int nstype)
 301 {
 302         static int (*plibc_func)(int fd, int nstype) = NULL;
 303         int retval;
 304         int saved_errno;
 305
 306         if (plibc_func == NULL) {
 307                 plibc_func = dlsym(RTLD_NEXT, "setns");
 308                 if (plibc_func == NULL) {
 309                         fprintf(stderr, "libustfork: unable to find \"setns\" symbol\n");
 310                         errno = ENOSYS;
 311                         return -1;
 312                 }
 313         }
 314
 315         /* Do the real setns */
 316         retval = plibc_func(fd, nstype);
 317         saved_errno = errno;
 318
 319         ust_after_setns();
 320
 321         errno = saved_errno;
 322         return retval;
 323 }
 324
 325 int unshare(int flags)
 326 {
 327         static int (*plibc_func)(int flags) = NULL;
 328         int retval;
 329         int saved_errno;
 330
 331         if (plibc_func == NULL) {
 332                 plibc_func = dlsym(RTLD_NEXT, "unshare");
 333                 if (plibc_func == NULL) {
 334                         fprintf(stderr, "libustfork: unable to find \"unshare\" symbol\n");
 335                         errno = ENOSYS;
 336                         return -1;
 337                 }
 338         }
 339
 340         /* Do the real setns */
 341         retval = plibc_func(flags);
 342         saved_errno = errno;
 343
 344         ust_after_unshare();
 345
 346         errno = saved_errno;
 347         return retval;
 348 }
 349
 350 int setresuid(uid_t ruid, uid_t euid, uid_t suid)
 351 {
 352         static int (*plibc_func)(uid_t ruid, uid_t euid, uid_t suid) = NULL;
 353         int retval;
 354         int saved_errno;
 355
 356         if (plibc_func == NULL) {
 357                 plibc_func = dlsym(RTLD_NEXT, "setresuid");
 358                 if (plibc_func == NULL) {
 359                         fprintf(stderr, "libustfork: unable to find \"setresuid\" symbol\n");
 360                         errno = ENOSYS;
 361                         return -1;
 362                 }
 363         }
 364
 365         /* Do the real setresuid */
 366         retval = plibc_func(ruid, euid, suid);
 367         saved_errno = errno;
 368
 369         ust_after_setresuid();
 370
 371         errno = saved_errno;
 372         return retval;
 373 }
 374
 375 int setresgid(gid_t rgid, gid_t egid, gid_t sgid)
 376 {
 377         static int (*plibc_func)(gid_t rgid, gid_t egid, gid_t sgid) = NULL;
 378         int retval;
 379         int saved_errno;
 380
 381         if (plibc_func == NULL) {
 382                 plibc_func = dlsym(RTLD_NEXT, "setresgid");
 383                 if (plibc_func == NULL) {
 384                         fprintf(stderr, "libustfork: unable to find \"setresgid\" symbol\n");
 385                         errno = ENOSYS;
 386                         return -1;
 387                 }
 388         }
 389
 390         /* Do the real setresgid */
 391         retval = plibc_func(rgid, egid, sgid);
 392         saved_errno = errno;
 393
 394         ust_after_setresgid();
 395
 396         errno = saved_errno;
 397         return retval;
 398 }
 399
 400 #elif defined (__FreeBSD__)
 401
 402 pid_t rfork(int flags)
 403 {
 404         static pid_t (*plibc_func)(void) = NULL;
 405         sigset_t sigset;
 406         pid_t retval;
 407         int saved_errno;
 408
 409         if (plibc_func == NULL) {
 410                 plibc_func = dlsym(RTLD_NEXT, "rfork");
 411                 if (plibc_func == NULL) {
 412                         fprintf(stderr, "libustfork: unable to find \"rfork\" symbol\n");
 413                         errno = ENOSYS;
 414                         return -1;
 415                 }
 416         }
 417
 418         ust_before_fork(&sigset);
 419         /* Do the real rfork */
 420         retval = plibc_func();
 421         saved_errno = errno;
 422         if (retval == 0) {
 423                 /* child */
 424                 ust_after_fork_child(&sigset);
 425         } else {
 426                 ust_after_fork_parent(&sigset);
 427         }
 428         errno = saved_errno;
 429         return retval;
 430 }
 431
 432 /*
 433  * On BSD, no need to override vfork, because it runs in the context of
 434  * the parent, with parent waiting until execve or exit is executed in
 435  * the child.
 436  */
 437
 438 #else
 439 #warning "Unknown OS. You might want to ensure that fork/clone/vfork/fork handling is complete."
 440 #endif