libpthread/nptl/init.c

   1 /* Copyright (C) 2002-2007, 2008, 2009 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    <http://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 <fork.h>
  32 #include <version.h>
  33 #include <smp.h>
  34 #include <lowlevellock.h>
  35 #include <bits/kernel-features.h>
  36 #include <stdio.h>
  37
  38 /* Size and alignment of static TLS block.  */
  39 size_t __static_tls_size;
  40 size_t __static_tls_align_m1;
  41
  42 #ifndef __ASSUME_SET_ROBUST_LIST
  43 /* Negative if we do not have the system call and we can use it.  */
  44 int __set_robust_list_avail;
  45 # define set_robust_list_not_avail() \
  46   __set_robust_list_avail = -1
  47 #else
  48 # define set_robust_list_not_avail() do { } while (0)
  49 #endif
  50
  51 #ifndef __ASSUME_FUTEX_CLOCK_REALTIME
  52 /* Nonzero if we do not have FUTEX_CLOCK_REALTIME.  */
  53 int __have_futex_clock_realtime;
  54 # define __set_futex_clock_realtime() \
  55   __have_futex_clock_realtime = 1
  56 #else
  57 #define __set_futex_clock_realtime() 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 /* For asynchronous cancellation we use a signal.  This is the handler.  */
  64 static void
  65 sigcancel_handler (int sig, siginfo_t *si, void *ctx)
  66 {
  67
  68   /* Safety check.  It would be possible to call this function for
  69      other signals and send a signal from another process.  This is not
  70      correct and might even be a security problem.  Try to catch as
  71      many incorrect invocations as possible.  */
  72   if (sig != SIGCANCEL
  73       || si->si_pid != getpid()
  74       || si->si_code != SI_TKILL)
  75     return;
  76
  77   struct pthread *self = THREAD_SELF;
  78
  79   int oldval = THREAD_GETMEM (self, cancelhandling);
  80   while (1)
  81     {
  82       /* We are canceled now.  When canceled by another thread this flag
  83          is already set but if the signal is directly send (internally or
  84          from another process) is has to be done here.  */
  85       int newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
  86
  87       if (oldval == newval || (oldval & EXITING_BITMASK) != 0)
  88         /* Already canceled or exiting.  */
  89         break;
  90
  91       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
  92                                               oldval);
  93       if (curval == oldval)
  94         {
  95           /* Set the return value.  */
  96           THREAD_SETMEM (self, result, PTHREAD_CANCELED);
  97
  98           /* Make sure asynchronous cancellation is still enabled.  */
  99           if ((newval & CANCELTYPE_BITMASK) != 0)
 100             /* Run the registered destructors and terminate the thread.  */
 101             __do_cancel ();
 102
 103           break;
 104         }
 105
 106       oldval = curval;
 107     }
 108 }
 109
 110
 111 struct xid_command *__xidcmd attribute_hidden;
 112
 113 /* For asynchronous cancellation we use a signal.  This is the handler.  */
 114 static void
 115 sighandler_setxid (int sig, siginfo_t *si, void *ctx)
 116 {
 117
 118   /* Safety check.  It would be possible to call this function for
 119      other signals and send a signal from another process.  This is not
 120      correct and might even be a security problem.  Try to catch as
 121      many incorrect invocations as possible.  */
 122   if (sig != SIGSETXID
 123       || si->si_pid != getpid()
 124       || si->si_code != SI_TKILL)
 125     return;
 126
 127   INTERNAL_SYSCALL_DECL (err);
 128   INTERNAL_SYSCALL_NCS (__xidcmd->syscall_no, err, 3, __xidcmd->id[0],
 129                         __xidcmd->id[1], __xidcmd->id[2]);
 130
 131   /* Reset the SETXID flag.  */
 132   struct pthread *self = THREAD_SELF;
 133   int flags, newval;
 134   do
 135     {
 136       flags = THREAD_GETMEM (self, cancelhandling);
 137       newval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling,
 138                                           flags & ~SETXID_BITMASK, flags);
 139     }
 140   while (flags != newval);
 141
 142   /* And release the futex.  */
 143   self->setxid_futex = 1;
 144   lll_futex_wake (&self->setxid_futex, 1, LLL_PRIVATE);
 145
 146   if (atomic_decrement_val (&__xidcmd->cntr) == 0)
 147     lll_futex_wake (&__xidcmd->cntr, 1, LLL_PRIVATE);
 148 }
 149
 150
 151 /* When using __thread for this, we do it in libc so as not
 152    to give libpthread its own TLS segment just for this.  */
 153 extern void **__libc_dl_error_tsd (void) __attribute__ ((const));
 154
 155
 156 /* This can be set by the debugger before initialization is complete.  */
 157 static bool __nptl_initial_report_events __attribute_used__;
 158
 159 void __pthread_initialize_minimal_internal (void) attribute_hidden;
 160 void
 161 __pthread_initialize_minimal_internal (void)
 162 {
 163   static int initialized = 0;
 164
 165   if (initialized)
 166     return;
 167   initialized = 1;
 168
 169   /* Minimal initialization of the thread descriptor.  */
 170   struct pthread *pd = THREAD_SELF;
 171   INTERNAL_SYSCALL_DECL (err);
 172   pd->tid = INTERNAL_SYSCALL (set_tid_address, err, 1, &pd->tid);
 173   THREAD_SETMEM (pd, specific[0], &pd->specific_1stblock[0]);
 174   THREAD_SETMEM (pd, user_stack, true);
 175   if (LLL_LOCK_INITIALIZER != 0)
 176     THREAD_SETMEM (pd, lock, LLL_LOCK_INITIALIZER);
 177
 178   /* Initialize the robust mutex data.  */
 179 #ifdef __PTHREAD_MUTEX_HAVE_PREV
 180   pd->robust_prev = &pd->robust_head;
 181 #endif
 182   pd->robust_head.list = &pd->robust_head;
 183 #ifdef __NR_set_robust_list
 184   pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock)
 185                                   - offsetof (pthread_mutex_t,
 186                                               __data.__list.__next));
 187   int res = INTERNAL_SYSCALL (set_robust_list, err, 2, &pd->robust_head,
 188                               sizeof (struct robust_list_head));
 189   if (INTERNAL_SYSCALL_ERROR_P (res, err))
 190 #endif
 191     set_robust_list_not_avail ();
 192
 193 #ifndef __ASSUME_PRIVATE_FUTEX
 194   /* Private futexes are always used (at least internally) so that
 195      doing the test once this early is beneficial.  */
 196   {
 197     int word = 0;
 198     word = INTERNAL_SYSCALL (futex, err, 3, &word,
 199                             FUTEX_WAKE | FUTEX_PRIVATE_FLAG, 1);
 200     if (!INTERNAL_SYSCALL_ERROR_P (word, err))
 201       THREAD_SETMEM (pd, header.private_futex, FUTEX_PRIVATE_FLAG);
 202   }
 203
 204   /* Private futexes have been introduced earlier than the
 205      FUTEX_CLOCK_REALTIME flag.  We don't have to run the test if we
 206      know the former are not supported.  This also means we know the
 207      kernel will return ENOSYS for unknown operations.  */
 208   if (THREAD_GETMEM (pd, header.private_futex) != 0)
 209 #endif
 210 #ifndef __ASSUME_FUTEX_CLOCK_REALTIME
 211     {
 212       int word = 0;
 213       /* NB: the syscall actually takes six parameters.  The last is the
 214          bit mask.  But since we will not actually wait at all the value
 215          is irrelevant.  Given that passing six parameters is difficult
 216          on some architectures we just pass whatever random value the
 217          calling convention calls for to the kernel.  It causes no harm.  */
 218       word = INTERNAL_SYSCALL (futex, err, 5, &word,
 219                                FUTEX_WAIT_BITSET | FUTEX_CLOCK_REALTIME
 220                                | FUTEX_PRIVATE_FLAG, 1, NULL, 0);
 221       assert (INTERNAL_SYSCALL_ERROR_P (word, err));
 222       if (INTERNAL_SYSCALL_ERRNO (word, err) != ENOSYS)
 223         __set_futex_clock_realtime ();
 224     }
 225 #endif
 226
 227   /* Set initial thread's stack block from 0 up to __libc_stack_end.
 228      It will be bigger than it actually is, but for unwind.c/pt-longjmp.c
 229      purposes this is good enough.  */
 230   THREAD_SETMEM (pd, stackblock_size, (size_t) __libc_stack_end);
 231
 232   /* Initialize the list of all running threads with the main thread.  */
 233   INIT_LIST_HEAD (&__stack_user);
 234   list_add (&pd->list, &__stack_user);
 235
 236   /* Before initializing __stack_user, the debugger could not find us and
 237      had to set __nptl_initial_report_events.  Propagate its setting.  */
 238   THREAD_SETMEM (pd, report_events, __nptl_initial_report_events);
 239
 240   /* Install the cancellation signal handler.  If for some reason we
 241      cannot install the handler we do not abort.  Maybe we should, but
 242      it is only asynchronous cancellation which is affected.  */
 243   struct sigaction sa;
 244   sa.sa_sigaction = sigcancel_handler;
 245   sa.sa_flags = SA_SIGINFO;
 246   __sigemptyset (&sa.sa_mask);
 247
 248   (void) __libc_sigaction (SIGCANCEL, &sa, NULL);
 249
 250   /* Install the handle to change the threads' uid/gid.  */
 251   sa.sa_sigaction = sighandler_setxid;
 252   sa.sa_flags = SA_SIGINFO | SA_RESTART;
 253
 254   (void) __libc_sigaction (SIGSETXID, &sa, NULL);
 255
 256   /* The parent process might have left the signals blocked.  Just in
 257      case, unblock it.  We reuse the signal mask in the sigaction
 258      structure.  It is already cleared.  */
 259   __sigaddset (&sa.sa_mask, SIGCANCEL);
 260   __sigaddset (&sa.sa_mask, SIGSETXID);
 261   (void) INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_UNBLOCK, &sa.sa_mask,
 262                            NULL, _NSIG / 8);
 263
 264   /* Get the size of the static and alignment requirements for the TLS
 265      block.  */
 266   size_t static_tls_align;
 267   _dl_get_tls_static_info (&__static_tls_size, &static_tls_align);
 268
 269   /* Make sure the size takes all the alignments into account.  */
 270   if (STACK_ALIGN > static_tls_align)
 271     static_tls_align = STACK_ALIGN;
 272   __static_tls_align_m1 = static_tls_align - 1;
 273
 274   __static_tls_size = roundup (__static_tls_size, static_tls_align);
 275
 276   /* Determine the default allowed stack size.  This is the size used
 277      in case the user does not specify one.  */
 278   struct rlimit limit;
 279   if (getrlimit (RLIMIT_STACK, &limit) != 0
 280       || limit.rlim_cur == RLIM_INFINITY)
 281     /* The system limit is not usable.  Use a user-specified or
 282        architecture-specific default.  */
 283     limit.rlim_cur = __PTHREADS_STACK_DEFAULT_SIZE__;
 284   if (limit.rlim_cur < PTHREAD_STACK_MIN)
 285     /* The system limit is unusably small.
 286        Use the minimal size acceptable.  */
 287     limit.rlim_cur = PTHREAD_STACK_MIN;
 288
 289   /* Do not exceed the user-specified or architecture-specific default */
 290   if (limit.rlim_cur > __PTHREADS_STACK_DEFAULT_SIZE__)
 291     limit.rlim_cur = __PTHREADS_STACK_DEFAULT_SIZE__;
 292
 293   /* Make sure it meets the minimum size that allocate_stack
 294      (allocatestack.c) will demand, which depends on the page size.  */
 295   #ifdef SHARED
 296   extern size_t GLRO(dl_pagesize);
 297   const uintptr_t pagesz = GLRO(dl_pagesize);
 298   #else
 299   const uintptr_t pagesz = sysconf (_SC_PAGESIZE);
 300   #endif
 301   const size_t minstack = pagesz + __static_tls_size + MINIMAL_REST_STACK;
 302   if (limit.rlim_cur < minstack)
 303     limit.rlim_cur = minstack;
 304
 305   /* Round the resource limit up to page size.  */
 306   limit.rlim_cur = (limit.rlim_cur + pagesz - 1) & -pagesz;
 307   __default_stacksize = limit.rlim_cur;
 308
 309 #ifdef SHARED
 310   /* Transfer the old value from the dynamic linker's internal location.  */
 311   *__libc_dl_error_tsd () = *(*GL(dl_error_catch_tsd)) ();
 312   GL(dl_error_catch_tsd) = &__libc_dl_error_tsd;
 313
 314 #endif
 315
 316   GL(dl_init_static_tls) = &__pthread_init_static_tls;
 317
 318   /* Register the fork generation counter with the libc.  */
 319 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
 320   __libc_multiple_threads_ptr =
 321 #endif
 322     __libc_pthread_init (&__fork_generation, __reclaim_stacks);
 323
 324   /* Determine whether the machine is SMP or not.  */
 325   __is_smp = is_smp_system ();
 326
 327   /* uClibc-specific stdio initialization for threads. */
 328   {
 329     FILE *fp;
 330     _stdio_user_locking = 0;       /* 2 if threading not initialized */
 331     for (fp = _stdio_openlist; fp != NULL; fp = fp->__nextopen) {
 332       if (fp->__user_locking != 1) {
 333         fp->__user_locking = 0;
 334       }
 335     }
 336   }
 337 }
 338 strong_alias (__pthread_initialize_minimal_internal,
 339               __pthread_initialize_minimal)
 340
 341 size_t
 342 __pthread_get_minstack (const pthread_attr_t *attr)
 343 {
 344   return __static_tls_size + PTHREAD_STACK_MIN;
 345 }