nptl/nptl-init.c

   1 /* Copyright (C) 2002-2019 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <errno.h>
  21 #include <limits.h>
  22 #include <signal.h>
  23 #include <stdlib.h>
  24 #include <unistd.h>
  25 #include <sys/param.h>
  26 #include <sys/resource.h>
  27 #include <pthreadP.h>
  28 #include <atomic.h>
  29 #include <ldsodefs.h>
  30 #include <tls.h>
  31 #include <list.h>
  32 #include <fork.h>
  33 #include <version.h>
  34 #include <shlib-compat.h>
  35 #include <smp.h>
  36 #include <lowlevellock.h>
  37 #include <futex-internal.h>
  38 #include <kernel-features.h>
  39 #include <libc-pointer-arith.h>
  40 #include <pthread-pids.h>
  41 #include <pthread_mutex_conf.h>
  42
  43 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
  44 /* Pointer to the corresponding variable in libc.  */
  45 int *__libc_multiple_threads_ptr attribute_hidden;
  46 #endif
  47
  48 /* Size and alignment of static TLS block.  */
  49 size_t __static_tls_size;
  50 size_t __static_tls_align_m1;
  51
  52 #ifndef __ASSUME_SET_ROBUST_LIST
  53 /* Negative if we do not have the system call and we can use it.  */
  54 int __set_robust_list_avail;
  55 # define set_robust_list_not_avail() \
  56   __set_robust_list_avail = -1
  57 #else
  58 # define set_robust_list_not_avail() do { } while (0)
  59 #endif
  60
  61 /* Version of the library, used in libthread_db to detect mismatches.  */
  62 static const char nptl_version[] __attribute_used__ = VERSION;
  63
  64
  65 #ifdef SHARED
  66 static
  67 #else
  68 extern
  69 #endif
  70 void __nptl_set_robust (struct pthread *);
  71
  72 #ifdef SHARED
  73 static const struct pthread_functions pthread_functions =
  74   {
  75     .ptr_pthread_attr_getschedpolicy = __pthread_attr_getschedpolicy,
  76     .ptr_pthread_attr_setschedpolicy = __pthread_attr_setschedpolicy,
  77     .ptr_pthread_attr_getscope = __pthread_attr_getscope,
  78     .ptr_pthread_attr_setscope = __pthread_attr_setscope,
  79     .ptr_pthread_condattr_destroy = __pthread_condattr_destroy,
  80     .ptr_pthread_condattr_init = __pthread_condattr_init,
  81     .ptr___pthread_cond_broadcast = __pthread_cond_broadcast,
  82     .ptr___pthread_cond_destroy = __pthread_cond_destroy,
  83     .ptr___pthread_cond_init = __pthread_cond_init,
  84     .ptr___pthread_cond_signal = __pthread_cond_signal,
  85     .ptr___pthread_cond_wait = __pthread_cond_wait,
  86     .ptr___pthread_cond_timedwait = __pthread_cond_timedwait,
  87 # if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_3_2)
  88     .ptr___pthread_cond_broadcast_2_0 = __pthread_cond_broadcast_2_0,
  89     .ptr___pthread_cond_destroy_2_0 = __pthread_cond_destroy_2_0,
  90     .ptr___pthread_cond_init_2_0 = __pthread_cond_init_2_0,
  91     .ptr___pthread_cond_signal_2_0 = __pthread_cond_signal_2_0,
  92     .ptr___pthread_cond_wait_2_0 = __pthread_cond_wait_2_0,
  93     .ptr___pthread_cond_timedwait_2_0 = __pthread_cond_timedwait_2_0,
  94 # endif
  95     .ptr___pthread_exit = __pthread_exit,
  96     .ptr_pthread_getschedparam = __pthread_getschedparam,
  97     .ptr_pthread_setschedparam = __pthread_setschedparam,
  98     .ptr_pthread_mutex_destroy = __pthread_mutex_destroy,
  99     .ptr_pthread_mutex_init = __pthread_mutex_init,
 100     .ptr_pthread_mutex_lock = __pthread_mutex_lock,
 101     .ptr_pthread_mutex_unlock = __pthread_mutex_unlock,
 102     .ptr___pthread_setcancelstate = __pthread_setcancelstate,
 103     .ptr_pthread_setcanceltype = __pthread_setcanceltype,
 104     .ptr___pthread_cleanup_upto = __pthread_cleanup_upto,
 105     .ptr___pthread_once = __pthread_once,
 106     .ptr___pthread_rwlock_rdlock = __pthread_rwlock_rdlock,
 107     .ptr___pthread_rwlock_wrlock = __pthread_rwlock_wrlock,
 108     .ptr___pthread_rwlock_unlock = __pthread_rwlock_unlock,
 109     .ptr___pthread_key_create = __pthread_key_create,
 110     .ptr___pthread_getspecific = __pthread_getspecific,
 111     .ptr___pthread_setspecific = __pthread_setspecific,
 112     .ptr__pthread_cleanup_push_defer = __pthread_cleanup_push_defer,
 113     .ptr__pthread_cleanup_pop_restore = __pthread_cleanup_pop_restore,
 114     .ptr_nthreads = &__nptl_nthreads,
 115     .ptr___pthread_unwind = &__pthread_unwind,
 116     .ptr__nptl_deallocate_tsd = __nptl_deallocate_tsd,
 117 # ifdef SIGSETXID
 118     .ptr__nptl_setxid = __nptl_setxid,
 119 # endif
 120     .ptr_set_robust = __nptl_set_robust
 121   };
 122 # define ptr_pthread_functions &pthread_functions
 123 #else
 124 # define ptr_pthread_functions NULL
 125 #endif
 126
 127
 128 #ifdef SHARED
 129 static
 130 #endif
 131 void
 132 __nptl_set_robust (struct pthread *self)
 133 {
 134 #ifdef __NR_set_robust_list
 135   INTERNAL_SYSCALL_DECL (err);
 136   INTERNAL_SYSCALL (set_robust_list, err, 2, &self->robust_head,
 137                     sizeof (struct robust_list_head));
 138 #endif
 139 }
 140
 141
 142 #ifdef SIGCANCEL
 143 /* For asynchronous cancellation we use a signal.  This is the handler.  */
 144 static void
 145 sigcancel_handler (int sig, siginfo_t *si, void *ctx)
 146 {
 147   /* Safety check.  It would be possible to call this function for
 148      other signals and send a signal from another process.  This is not
 149      correct and might even be a security problem.  Try to catch as
 150      many incorrect invocations as possible.  */
 151   if (sig != SIGCANCEL
 152       || si->si_pid != __getpid()
 153       || si->si_code != SI_TKILL)
 154     return;
 155
 156   struct pthread *self = THREAD_SELF;
 157
 158   int oldval = THREAD_GETMEM (self, cancelhandling);
 159   while (1)
 160     {
 161       /* We are canceled now.  When canceled by another thread this flag
 162          is already set but if the signal is directly send (internally or
 163          from another process) is has to be done here.  */
 164       int newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
 165
 166       if (oldval == newval || (oldval & EXITING_BITMASK) != 0)
 167         /* Already canceled or exiting.  */
 168         break;
 169
 170       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
 171                                               oldval);
 172       if (curval == oldval)
 173         {
 174           /* Set the return value.  */
 175           THREAD_SETMEM (self, result, PTHREAD_CANCELED);
 176
 177           /* Make sure asynchronous cancellation is still enabled.  */
 178           if ((newval & CANCELTYPE_BITMASK) != 0)
 179             /* Run the registered destructors and terminate the thread.  */
 180             __do_cancel ();
 181
 182           break;
 183         }
 184
 185       oldval = curval;
 186     }
 187 }
 188 #endif
 189
 190
 191 #ifdef SIGSETXID
 192 struct xid_command *__xidcmd attribute_hidden;
 193
 194 /* We use the SIGSETXID signal in the setuid, setgid, etc. implementations to
 195    tell each thread to call the respective setxid syscall on itself.  This is
 196    the handler.  */
 197 static void
 198 sighandler_setxid (int sig, siginfo_t *si, void *ctx)
 199 {
 200   int result;
 201
 202   /* Safety check.  It would be possible to call this function for
 203      other signals and send a signal from another process.  This is not
 204      correct and might even be a security problem.  Try to catch as
 205      many incorrect invocations as possible.  */
 206   if (sig != SIGSETXID
 207       || si->si_pid != __getpid ()
 208       || si->si_code != SI_TKILL)
 209     return;
 210
 211   INTERNAL_SYSCALL_DECL (err);
 212   result = INTERNAL_SYSCALL_NCS (__xidcmd->syscall_no, err, 3, __xidcmd->id[0],
 213                                  __xidcmd->id[1], __xidcmd->id[2]);
 214   int error = 0;
 215   if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result, err)))
 216     error = INTERNAL_SYSCALL_ERRNO (result, err);
 217   __nptl_setxid_error (__xidcmd, error);
 218
 219   /* Reset the SETXID flag.  */
 220   struct pthread *self = THREAD_SELF;
 221   int flags, newval;
 222   do
 223     {
 224       flags = THREAD_GETMEM (self, cancelhandling);
 225       newval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling,
 226                                           flags & ~SETXID_BITMASK, flags);
 227     }
 228   while (flags != newval);
 229
 230   /* And release the futex.  */
 231   self->setxid_futex = 1;
 232   futex_wake (&self->setxid_futex, 1, FUTEX_PRIVATE);
 233
 234   if (atomic_decrement_val (&__xidcmd->cntr) == 0)
 235     futex_wake ((unsigned int *) &__xidcmd->cntr, 1, FUTEX_PRIVATE);
 236 }
 237 #endif
 238
 239
 240 /* When using __thread for this, we do it in libc so as not
 241    to give libpthread its own TLS segment just for this.  */
 242 extern void **__libc_dl_error_tsd (void) __attribute__ ((const));
 243
 244
 245 /* This can be set by the debugger before initialization is complete.  */
 246 static bool __nptl_initial_report_events __attribute_used__;
 247
 248 void
 249 __pthread_initialize_minimal_internal (void)
 250 {
 251   /* Minimal initialization of the thread descriptor.  */
 252   struct pthread *pd = THREAD_SELF;
 253   __pthread_initialize_pids (pd);
 254   THREAD_SETMEM (pd, specific[0], &pd->specific_1stblock[0]);
 255   THREAD_SETMEM (pd, user_stack, true);
 256
 257   /* Initialize the robust mutex data.  */
 258   {
 259 #if __PTHREAD_MUTEX_HAVE_PREV
 260     pd->robust_prev = &pd->robust_head;
 261 #endif
 262     pd->robust_head.list = &pd->robust_head;
 263 #ifdef __NR_set_robust_list
 264     pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock)
 265                                     - offsetof (pthread_mutex_t,
 266                                                 __data.__list.__next));
 267     INTERNAL_SYSCALL_DECL (err);
 268     int res = INTERNAL_SYSCALL (set_robust_list, err, 2, &pd->robust_head,
 269                                 sizeof (struct robust_list_head));
 270     if (INTERNAL_SYSCALL_ERROR_P (res, err))
 271 #endif
 272       set_robust_list_not_avail ();
 273   }
 274
 275   /* Set initial thread's stack block from 0 up to __libc_stack_end.
 276      It will be bigger than it actually is, but for unwind.c/pt-longjmp.c
 277      purposes this is good enough.  */
 278   THREAD_SETMEM (pd, stackblock_size, (size_t) __libc_stack_end);
 279
 280   /* Initialize the list of all running threads with the main thread.  */
 281   INIT_LIST_HEAD (&__stack_user);
 282   list_add (&pd->list, &__stack_user);
 283
 284   /* Before initializing __stack_user, the debugger could not find us and
 285      had to set __nptl_initial_report_events.  Propagate its setting.  */
 286   THREAD_SETMEM (pd, report_events, __nptl_initial_report_events);
 287
 288 #if defined SIGCANCEL || defined SIGSETXID
 289   struct sigaction sa;
 290   __sigemptyset (&sa.sa_mask);
 291
 292 # ifdef SIGCANCEL
 293   /* Install the cancellation signal handler.  If for some reason we
 294      cannot install the handler we do not abort.  Maybe we should, but
 295      it is only asynchronous cancellation which is affected.  */
 296   sa.sa_sigaction = sigcancel_handler;
 297   sa.sa_flags = SA_SIGINFO;
 298   (void) __libc_sigaction (SIGCANCEL, &sa, NULL);
 299 # endif
 300
 301 # ifdef SIGSETXID
 302   /* Install the handle to change the threads' uid/gid.  */
 303   sa.sa_sigaction = sighandler_setxid;
 304   sa.sa_flags = SA_SIGINFO | SA_RESTART;
 305   (void) __libc_sigaction (SIGSETXID, &sa, NULL);
 306 # endif
 307
 308   /* The parent process might have left the signals blocked.  Just in
 309      case, unblock it.  We reuse the signal mask in the sigaction
 310      structure.  It is already cleared.  */
 311 # ifdef SIGCANCEL
 312   __sigaddset (&sa.sa_mask, SIGCANCEL);
 313 # endif
 314 # ifdef SIGSETXID
 315   __sigaddset (&sa.sa_mask, SIGSETXID);
 316 # endif
 317   {
 318     INTERNAL_SYSCALL_DECL (err);
 319     (void) INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_UNBLOCK, &sa.sa_mask,
 320                              NULL, _NSIG / 8);
 321   }
 322 #endif
 323
 324   /* Get the size of the static and alignment requirements for the TLS
 325      block.  */
 326   size_t static_tls_align;
 327   _dl_get_tls_static_info (&__static_tls_size, &static_tls_align);
 328
 329   /* Make sure the size takes all the alignments into account.  */
 330   if (STACK_ALIGN > static_tls_align)
 331     static_tls_align = STACK_ALIGN;
 332   __static_tls_align_m1 = static_tls_align - 1;
 333
 334   __static_tls_size = roundup (__static_tls_size, static_tls_align);
 335
 336   /* Determine the default allowed stack size.  This is the size used
 337      in case the user does not specify one.  */
 338   struct rlimit limit;
 339   if (__getrlimit (RLIMIT_STACK, &limit) != 0
 340       || limit.rlim_cur == RLIM_INFINITY)
 341     /* The system limit is not usable.  Use an architecture-specific
 342        default.  */
 343     limit.rlim_cur = ARCH_STACK_DEFAULT_SIZE;
 344   else if (limit.rlim_cur < PTHREAD_STACK_MIN)
 345     /* The system limit is unusably small.
 346        Use the minimal size acceptable.  */
 347     limit.rlim_cur = PTHREAD_STACK_MIN;
 348
 349   /* Make sure it meets the minimum size that allocate_stack
 350      (allocatestack.c) will demand, which depends on the page size.  */
 351   const uintptr_t pagesz = GLRO(dl_pagesize);
 352   const size_t minstack = pagesz + __static_tls_size + MINIMAL_REST_STACK;
 353   if (limit.rlim_cur < minstack)
 354     limit.rlim_cur = minstack;
 355
 356   /* Round the resource limit up to page size.  */
 357   limit.rlim_cur = ALIGN_UP (limit.rlim_cur, pagesz);
 358   lll_lock (__default_pthread_attr_lock, LLL_PRIVATE);
 359   __default_pthread_attr.stacksize = limit.rlim_cur;
 360   __default_pthread_attr.guardsize = GLRO (dl_pagesize);
 361   lll_unlock (__default_pthread_attr_lock, LLL_PRIVATE);
 362
 363 #ifdef SHARED
 364   /* Make __rtld_lock_{,un}lock_recursive use pthread_mutex_{,un}lock,
 365      keep the lock count from the ld.so implementation.  */
 366   GL(dl_rtld_lock_recursive) = (void *) __pthread_mutex_lock;
 367   GL(dl_rtld_unlock_recursive) = (void *) __pthread_mutex_unlock;
 368   unsigned int rtld_lock_count = GL(dl_load_lock).mutex.__data.__count;
 369   GL(dl_load_lock).mutex.__data.__count = 0;
 370   while (rtld_lock_count-- > 0)
 371     __pthread_mutex_lock (&GL(dl_load_lock).mutex);
 372
 373   GL(dl_make_stack_executable_hook) = &__make_stacks_executable;
 374 #endif
 375
 376   GL(dl_init_static_tls) = &__pthread_init_static_tls;
 377
 378   GL(dl_wait_lookup_done) = &__wait_lookup_done;
 379
 380   /* Register the fork generation counter with the libc.  */
 381 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
 382   __libc_multiple_threads_ptr =
 383 #endif
 384     __libc_pthread_init (&__fork_generation, __reclaim_stacks,
 385                          ptr_pthread_functions);
 386
 387   /* Determine whether the machine is SMP or not.  */
 388   __is_smp = is_smp_system ();
 389
 390 #if HAVE_TUNABLES
 391   __pthread_tunables_init ();
 392 #endif
 393 }
 394 strong_alias (__pthread_initialize_minimal_internal,
 395               __pthread_initialize_minimal)
 396
 397
 398 /* This function is internal (it has a GLIBC_PRIVATE) version, but it
 399    is widely used (either via weak symbol, or dlsym) to obtain the
 400    __static_tls_size value.  This value is then used to adjust the
 401    value of the stack size attribute, so that applications receive the
 402    full requested stack size, not diminished by the TCB and static TLS
 403    allocation on the stack.  Once the TCB is separately allocated,
 404    this function should be removed or renamed (if it is still
 405    necessary at that point).  */
 406 size_t
 407 __pthread_get_minstack (const pthread_attr_t *attr)
 408 {
 409   return GLRO(dl_pagesize) + __static_tls_size + PTHREAD_STACK_MIN;
 410 }