nptl/nptl-init.c

   1 /* Copyright (C) 2002-2021 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 <lowlevellock.h>
  36 #include <futex-internal.h>
  37 #include <kernel-features.h>
  38 #include <libc-pointer-arith.h>
  39 #include <pthread-pids.h>
  40 #include <pthread_mutex_conf.h>
  41
  42 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
  43 /* Pointer to the corresponding variable in libc.  */
  44 int *__libc_multiple_threads_ptr attribute_hidden;
  45 #endif
  46
  47 /* Size and alignment of static TLS block.  */
  48 size_t __static_tls_size;
  49 size_t __static_tls_align_m1;
  50
  51 #ifndef __ASSUME_SET_ROBUST_LIST
  52 /* Negative if we do not have the system call and we can use it.  */
  53 int __set_robust_list_avail;
  54 # define set_robust_list_not_avail() \
  55   __set_robust_list_avail = -1
  56 #else
  57 # define set_robust_list_not_avail() do { } while (0)
  58 #endif
  59
  60 /* Version of the library, used in libthread_db to detect mismatches.  */
  61 static const char nptl_version[] __attribute_used__ = VERSION;
  62
  63
  64 #ifdef SHARED
  65 static
  66 #else
  67 extern
  68 #endif
  69 void __nptl_set_robust (struct pthread *);
  70
  71 #ifdef SHARED
  72 static const struct pthread_functions pthread_functions =
  73   {
  74     .ptr___pthread_cond_broadcast = __pthread_cond_broadcast,
  75     .ptr___pthread_cond_signal = __pthread_cond_signal,
  76     .ptr___pthread_cond_wait = __pthread_cond_wait,
  77     .ptr___pthread_cond_timedwait = __pthread_cond_timedwait,
  78 # if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_3_2)
  79     .ptr___pthread_cond_broadcast_2_0 = __pthread_cond_broadcast_2_0,
  80     .ptr___pthread_cond_signal_2_0 = __pthread_cond_signal_2_0,
  81     .ptr___pthread_cond_wait_2_0 = __pthread_cond_wait_2_0,
  82     .ptr___pthread_cond_timedwait_2_0 = __pthread_cond_timedwait_2_0,
  83 # endif
  84     .ptr___pthread_exit = __pthread_exit,
  85     .ptr_pthread_mutex_destroy = __pthread_mutex_destroy,
  86     .ptr_pthread_mutex_init = __pthread_mutex_init,
  87     .ptr_pthread_mutex_lock = __pthread_mutex_lock,
  88     .ptr_pthread_mutex_unlock = __pthread_mutex_unlock,
  89     .ptr___pthread_setcancelstate = __pthread_setcancelstate,
  90     .ptr_pthread_setcanceltype = __pthread_setcanceltype,
  91     .ptr___pthread_cleanup_upto = __pthread_cleanup_upto,
  92     .ptr___pthread_once = __pthread_once,
  93     .ptr___pthread_rwlock_rdlock = __pthread_rwlock_rdlock,
  94     .ptr___pthread_rwlock_wrlock = __pthread_rwlock_wrlock,
  95     .ptr___pthread_rwlock_unlock = __pthread_rwlock_unlock,
  96     .ptr___pthread_key_create = __pthread_key_create,
  97     .ptr___pthread_getspecific = __pthread_getspecific,
  98     .ptr___pthread_setspecific = __pthread_setspecific,
  99     .ptr__pthread_cleanup_push_defer = __pthread_cleanup_push_defer,
 100     .ptr__pthread_cleanup_pop_restore = __pthread_cleanup_pop_restore,
 101     .ptr_nthreads = &__nptl_nthreads,
 102     .ptr___pthread_unwind = &__pthread_unwind,
 103     .ptr__nptl_deallocate_tsd = __nptl_deallocate_tsd,
 104     .ptr__nptl_setxid = __nptl_setxid,
 105     .ptr_set_robust = __nptl_set_robust
 106   };
 107 # define ptr_pthread_functions &pthread_functions
 108 #else
 109 # define ptr_pthread_functions NULL
 110 #endif
 111
 112
 113 #ifdef SHARED
 114 static
 115 #endif
 116 void
 117 __nptl_set_robust (struct pthread *self)
 118 {
 119   INTERNAL_SYSCALL_CALL (set_robust_list, &self->robust_head,
 120                          sizeof (struct robust_list_head));
 121 }
 122
 123
 124 /* For asynchronous cancellation we use a signal.  This is the handler.  */
 125 static void
 126 sigcancel_handler (int sig, siginfo_t *si, void *ctx)
 127 {
 128   /* Safety check.  It would be possible to call this function for
 129      other signals and send a signal from another process.  This is not
 130      correct and might even be a security problem.  Try to catch as
 131      many incorrect invocations as possible.  */
 132   if (sig != SIGCANCEL
 133       || si->si_pid != __getpid()
 134       || si->si_code != SI_TKILL)
 135     return;
 136
 137   struct pthread *self = THREAD_SELF;
 138
 139   int oldval = THREAD_GETMEM (self, cancelhandling);
 140   while (1)
 141     {
 142       /* We are canceled now.  When canceled by another thread this flag
 143          is already set but if the signal is directly send (internally or
 144          from another process) is has to be done here.  */
 145       int newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
 146
 147       if (oldval == newval || (oldval & EXITING_BITMASK) != 0)
 148         /* Already canceled or exiting.  */
 149         break;
 150
 151       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
 152                                               oldval);
 153       if (curval == oldval)
 154         {
 155           /* Set the return value.  */
 156           THREAD_SETMEM (self, result, PTHREAD_CANCELED);
 157
 158           /* Make sure asynchronous cancellation is still enabled.  */
 159           if ((newval & CANCELTYPE_BITMASK) != 0)
 160             /* Run the registered destructors and terminate the thread.  */
 161             __do_cancel ();
 162
 163           break;
 164         }
 165
 166       oldval = curval;
 167     }
 168 }
 169
 170
 171 struct xid_command *__xidcmd attribute_hidden;
 172
 173 /* We use the SIGSETXID signal in the setuid, setgid, etc. implementations to
 174    tell each thread to call the respective setxid syscall on itself.  This is
 175    the handler.  */
 176 static void
 177 sighandler_setxid (int sig, siginfo_t *si, void *ctx)
 178 {
 179   int result;
 180
 181   /* Safety check.  It would be possible to call this function for
 182      other signals and send a signal from another process.  This is not
 183      correct and might even be a security problem.  Try to catch as
 184      many incorrect invocations as possible.  */
 185   if (sig != SIGSETXID
 186       || si->si_pid != __getpid ()
 187       || si->si_code != SI_TKILL)
 188     return;
 189
 190   result = INTERNAL_SYSCALL_NCS (__xidcmd->syscall_no, 3, __xidcmd->id[0],
 191                                  __xidcmd->id[1], __xidcmd->id[2]);
 192   int error = 0;
 193   if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result)))
 194     error = INTERNAL_SYSCALL_ERRNO (result);
 195   __nptl_setxid_error (__xidcmd, error);
 196
 197   /* Reset the SETXID flag.  */
 198   struct pthread *self = THREAD_SELF;
 199   int flags, newval;
 200   do
 201     {
 202       flags = THREAD_GETMEM (self, cancelhandling);
 203       newval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling,
 204                                           flags & ~SETXID_BITMASK, flags);
 205     }
 206   while (flags != newval);
 207
 208   /* And release the futex.  */
 209   self->setxid_futex = 1;
 210   futex_wake (&self->setxid_futex, 1, FUTEX_PRIVATE);
 211
 212   if (atomic_decrement_val (&__xidcmd->cntr) == 0)
 213     futex_wake ((unsigned int *) &__xidcmd->cntr, 1, FUTEX_PRIVATE);
 214 }
 215
 216
 217 /* When using __thread for this, we do it in libc so as not
 218    to give libpthread its own TLS segment just for this.  */
 219 extern void **__libc_dl_error_tsd (void) __attribute__ ((const));
 220
 221
 222 /* This can be set by the debugger before initialization is complete.  */
 223 static bool __nptl_initial_report_events __attribute_used__;
 224
 225 void
 226 __pthread_initialize_minimal_internal (void)
 227 {
 228   /* Minimal initialization of the thread descriptor.  */
 229   struct pthread *pd = THREAD_SELF;
 230   __pthread_initialize_pids (pd);
 231   THREAD_SETMEM (pd, specific[0], &pd->specific_1stblock[0]);
 232   THREAD_SETMEM (pd, user_stack, true);
 233
 234   /* Initialize the robust mutex data.  */
 235   {
 236 #if __PTHREAD_MUTEX_HAVE_PREV
 237     pd->robust_prev = &pd->robust_head;
 238 #endif
 239     pd->robust_head.list = &pd->robust_head;
 240     pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock)
 241                                     - offsetof (pthread_mutex_t,
 242                                                 __data.__list.__next));
 243     int res = INTERNAL_SYSCALL_CALL (set_robust_list, &pd->robust_head,
 244                                      sizeof (struct robust_list_head));
 245     if (INTERNAL_SYSCALL_ERROR_P (res))
 246       set_robust_list_not_avail ();
 247   }
 248
 249   /* Set initial thread's stack block from 0 up to __libc_stack_end.
 250      It will be bigger than it actually is, but for unwind.c/pt-longjmp.c
 251      purposes this is good enough.  */
 252   THREAD_SETMEM (pd, stackblock_size, (size_t) __libc_stack_end);
 253
 254   /* Before initializing GL (dl_stack_user), the debugger could not
 255      find us and had to set __nptl_initial_report_events.  Propagate
 256      its setting.  */
 257   THREAD_SETMEM (pd, report_events, __nptl_initial_report_events);
 258
 259   struct sigaction sa;
 260   __sigemptyset (&sa.sa_mask);
 261
 262   /* Install the cancellation signal handler.  If for some reason we
 263      cannot install the handler we do not abort.  Maybe we should, but
 264      it is only asynchronous cancellation which is affected.  */
 265   sa.sa_sigaction = sigcancel_handler;
 266   sa.sa_flags = SA_SIGINFO;
 267   (void) __libc_sigaction (SIGCANCEL, &sa, NULL);
 268
 269   /* Install the handle to change the threads' uid/gid.  */
 270   sa.sa_sigaction = sighandler_setxid;
 271   sa.sa_flags = SA_SIGINFO | SA_RESTART;
 272   (void) __libc_sigaction (SIGSETXID, &sa, NULL);
 273
 274   /* The parent process might have left the signals blocked.  Just in
 275      case, unblock it.  We reuse the signal mask in the sigaction
 276      structure.  It is already cleared.  */
 277   __sigaddset (&sa.sa_mask, SIGCANCEL);
 278   __sigaddset (&sa.sa_mask, SIGSETXID);
 279   INTERNAL_SYSCALL_CALL (rt_sigprocmask, SIG_UNBLOCK, &sa.sa_mask,
 280                          NULL, __NSIG_BYTES);
 281
 282   /* Get the size of the static and alignment requirements for the TLS
 283      block.  */
 284   size_t static_tls_align;
 285   _dl_get_tls_static_info (&__static_tls_size, &static_tls_align);
 286
 287   /* Make sure the size takes all the alignments into account.  */
 288   if (STACK_ALIGN > static_tls_align)
 289     static_tls_align = STACK_ALIGN;
 290   __static_tls_align_m1 = static_tls_align - 1;
 291
 292   __static_tls_size = roundup (__static_tls_size, static_tls_align);
 293
 294   /* Determine the default allowed stack size.  This is the size used
 295      in case the user does not specify one.  */
 296   struct rlimit limit;
 297   if (__getrlimit (RLIMIT_STACK, &limit) != 0
 298       || limit.rlim_cur == RLIM_INFINITY)
 299     /* The system limit is not usable.  Use an architecture-specific
 300        default.  */
 301     limit.rlim_cur = ARCH_STACK_DEFAULT_SIZE;
 302   else if (limit.rlim_cur < PTHREAD_STACK_MIN)
 303     /* The system limit is unusably small.
 304        Use the minimal size acceptable.  */
 305     limit.rlim_cur = PTHREAD_STACK_MIN;
 306
 307   /* Make sure it meets the minimum size that allocate_stack
 308      (allocatestack.c) will demand, which depends on the page size.  */
 309   const uintptr_t pagesz = GLRO(dl_pagesize);
 310   const size_t minstack = pagesz + __static_tls_size + MINIMAL_REST_STACK;
 311   if (limit.rlim_cur < minstack)
 312     limit.rlim_cur = minstack;
 313
 314   /* Round the resource limit up to page size.  */
 315   limit.rlim_cur = ALIGN_UP (limit.rlim_cur, pagesz);
 316   lll_lock (__default_pthread_attr_lock, LLL_PRIVATE);
 317   __default_pthread_attr.internal.stacksize = limit.rlim_cur;
 318   __default_pthread_attr.internal.guardsize = GLRO (dl_pagesize);
 319   lll_unlock (__default_pthread_attr_lock, LLL_PRIVATE);
 320
 321 #ifdef SHARED
 322   /* Make __rtld_lock_{,un}lock_recursive use pthread_mutex_{,un}lock,
 323      keep the lock count from the ld.so implementation.  */
 324   GL(dl_rtld_lock_recursive) = (void *) __pthread_mutex_lock;
 325   GL(dl_rtld_unlock_recursive) = (void *) __pthread_mutex_unlock;
 326   unsigned int rtld_lock_count = GL(dl_load_lock).mutex.__data.__count;
 327   GL(dl_load_lock).mutex.__data.__count = 0;
 328   while (rtld_lock_count-- > 0)
 329     __pthread_mutex_lock (&GL(dl_load_lock).mutex);
 330
 331   GL(dl_make_stack_executable_hook) = &__make_stacks_executable;
 332 #endif
 333
 334   GL(dl_init_static_tls) = &__pthread_init_static_tls;
 335
 336   /* Register the fork generation counter with the libc.  */
 337 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
 338   __libc_multiple_threads_ptr =
 339 #endif
 340     __libc_pthread_init (&__fork_generation, __reclaim_stacks,
 341                          ptr_pthread_functions);
 342
 343 #if HAVE_TUNABLES
 344   __pthread_tunables_init ();
 345 #endif
 346 }
 347 strong_alias (__pthread_initialize_minimal_internal,
 348               __pthread_initialize_minimal)
 349
 350
 351 /* This function is internal (it has a GLIBC_PRIVATE) version, but it
 352    is widely used (either via weak symbol, or dlsym) to obtain the
 353    __static_tls_size value.  This value is then used to adjust the
 354    value of the stack size attribute, so that applications receive the
 355    full requested stack size, not diminished by the TCB and static TLS
 356    allocation on the stack.  Once the TCB is separately allocated,
 357    this function should be removed or renamed (if it is still
 358    necessary at that point).  */
 359 size_t
 360 __pthread_get_minstack (const pthread_attr_t *attr)
 361 {
 362   return GLRO(dl_pagesize) + __static_tls_size + PTHREAD_STACK_MIN;
 363 }