path: root/libpthread/nptl/init.c

/* Copyright (C) 2002-2007, 2008, 2009 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/param.h>
#include <sys/resource.h>
#include <pthreadP.h>
#include <atomic.h>
#include <ldsodefs.h>
#include <tls.h>
#include <fork.h>
#include <version.h>
#include <smp.h>
#include <lowlevellock.h>
#include <bits/kernel-features.h>
#include <stdio.h>

/* Size and alignment of static TLS block.  */
size_t __static_tls_size;
size_t __static_tls_align_m1;

#ifndef __ASSUME_SET_ROBUST_LIST
/* Negative if we do not have the system call and we can use it.  */
int __set_robust_list_avail;
# define set_robust_list_not_avail() \
  __set_robust_list_avail = -1
#else
# define set_robust_list_not_avail() do { } while (0)
#endif

#ifndef __ASSUME_FUTEX_CLOCK_REALTIME
/* Nonzero if we do not have FUTEX_CLOCK_REALTIME.  */
int __have_futex_clock_realtime;
# define __set_futex_clock_realtime() \
  __have_futex_clock_realtime = 1
#else
#define __set_futex_clock_realtime() do { } while (0)
#endif

/* Version of the library, used in libthread_db to detect mismatches.  */
static const char nptl_version[] __attribute_used__ = VERSION;

/* For asynchronous cancellation we use a signal.  This is the handler.  */
static void
sigcancel_handler (int sig, siginfo_t *si, void *ctx)
{

  /* Safety check.  It would be possible to call this function for
     other signals and send a signal from another process.  This is not
     correct and might even be a security problem.  Try to catch as
     many incorrect invocations as possible.  */
  if (sig != SIGCANCEL
      || si->si_pid != getpid()
      || si->si_code != SI_TKILL)
    return;

  struct pthread *self = THREAD_SELF;

  int oldval = THREAD_GETMEM (self, cancelhandling);
  while (1)
    {
      /* We are canceled now.  When canceled by another thread this flag
	 is already set but if the signal is directly send (internally or
	 from another process) is has to be done here.  */
      int newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;

      if (oldval == newval || (oldval & EXITING_BITMASK) != 0)
	/* Already canceled or exiting.  */
	break;

      int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
					      oldval);
      if (curval == oldval)
	{
	  /* Set the return value.  */
	  THREAD_SETMEM (self, result, PTHREAD_CANCELED);

	  /* Make sure asynchronous cancellation is still enabled.  */
	  if ((newval & CANCELTYPE_BITMASK) != 0)
	    /* Run the registered destructors and terminate the thread.  */
	    __do_cancel ();

	  break;
	}

      oldval = curval;
    }
}


struct xid_command *__xidcmd attribute_hidden;

/* For asynchronous cancellation we use a signal.  This is the handler.  */
static void
sighandler_setxid (int sig, siginfo_t *si, void *ctx)
{

  /* Safety check.  It would be possible to call this function for
     other signals and send a signal from another process.  This is not
     correct and might even be a security problem.  Try to catch as
     many incorrect invocations as possible.  */
  if (sig != SIGSETXID
      || si->si_pid != getpid()
      || si->si_code != SI_TKILL)
    return;

  INTERNAL_SYSCALL_DECL (err);
  INTERNAL_SYSCALL_NCS (__xidcmd->syscall_no, err, 3, __xidcmd->id[0],
			__xidcmd->id[1], __xidcmd->id[2]);

  /* Reset the SETXID flag.  */
  struct pthread *self = THREAD_SELF;
  int flags, newval;
  do
    {
      flags = THREAD_GETMEM (self, cancelhandling);
      newval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling,
					  flags & ~SETXID_BITMASK, flags);
    }
  while (flags != newval);

  /* And release the futex.  */
  self->setxid_futex = 1;
  lll_futex_wake (&self->setxid_futex, 1, LLL_PRIVATE);

  if (atomic_decrement_val (&__xidcmd->cntr) == 0)
    lll_futex_wake (&__xidcmd->cntr, 1, LLL_PRIVATE);
}


/* When using __thread for this, we do it in libc so as not
   to give libpthread its own TLS segment just for this.  */
extern void **__libc_dl_error_tsd (void) __attribute__ ((const));


/* This can be set by the debugger before initialization is complete.  */
static bool __nptl_initial_report_events __attribute_used__;

void __pthread_initialize_minimal_internal (void) attribute_hidden;
void
__pthread_initialize_minimal_internal (void)
{
  static int initialized = 0;

  if (initialized)
    return;
  initialized = 1;

  /* Minimal initialization of the thread descriptor.  */
  struct pthread *pd = THREAD_SELF;
  INTERNAL_SYSCALL_DECL (err);
  pd->tid = INTERNAL_SYSCALL (set_tid_address, err, 1, &pd->tid);
  THREAD_SETMEM (pd, specific[0], &pd->specific_1stblock[0]);
  THREAD_SETMEM (pd, user_stack, true);
  if (LLL_LOCK_INITIALIZER != 0)
    THREAD_SETMEM (pd, lock, LLL_LOCK_INITIALIZER);

  /* Initialize the robust mutex data.  */
#ifdef __PTHREAD_MUTEX_HAVE_PREV
  pd->robust_prev = &pd->robust_head;
#endif
  pd->robust_head.list = &pd->robust_head;
#ifdef __NR_set_robust_list
  pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock)
				  - offsetof (pthread_mutex_t,
					      __data.__list.__next));
  int res = INTERNAL_SYSCALL (set_robust_list, err, 2, &pd->robust_head,
			      sizeof (struct robust_list_head));
  if (INTERNAL_SYSCALL_ERROR_P (res, err))
#endif
    set_robust_list_not_avail ();

#ifndef __ASSUME_PRIVATE_FUTEX
  /* Private futexes are always used (at least internally) so that
     doing the test once this early is beneficial.  */
  {
    int word = 0;
    word = INTERNAL_SYSCALL (futex, err, 3, &word,
			    FUTEX_WAKE | FUTEX_PRIVATE_FLAG, 1);
    if (!INTERNAL_SYSCALL_ERROR_P (word, err))
      THREAD_SETMEM (pd, header.private_futex, FUTEX_PRIVATE_FLAG);
  }

  /* Private futexes have been introduced earlier than the
     FUTEX_CLOCK_REALTIME flag.  We don't have to run the test if we
     know the former are not supported.  This also means we know the
     kernel will return ENOSYS for unknown operations.  */
  if (THREAD_GETMEM (pd, header.private_futex) != 0)
#endif
#ifndef __ASSUME_FUTEX_CLOCK_REALTIME
    {
      int word = 0;
      /* NB: the syscall actually takes six parameters.  The last is the
	 bit mask.  But since we will not actually wait at all the value
	 is irrelevant.  Given that passing six parameters is difficult
	 on some architectures we just pass whatever random value the
	 calling convention calls for to the kernel.  It causes no harm.  */
      word = INTERNAL_SYSCALL (futex, err, 5, &word,
			       FUTEX_WAIT_BITSET | FUTEX_CLOCK_REALTIME
			       | FUTEX_PRIVATE_FLAG, 1, NULL, 0);
      assert (INTERNAL_SYSCALL_ERROR_P (word, err));
      if (INTERNAL_SYSCALL_ERRNO (word, err) != ENOSYS)
	__set_futex_clock_realtime ();
    }
#endif

  /* Set initial thread's stack block from 0 up to __libc_stack_end.
     It will be bigger than it actually is, but for unwind.c/pt-longjmp.c
     purposes this is good enough.  */
  THREAD_SETMEM (pd, stackblock_size, (size_t) __libc_stack_end);

  /* Initialize the list of all running threads with the main thread.  */
  INIT_LIST_HEAD (&__stack_user);
  list_add (&pd->list, &__stack_user);

  /* Before initializing __stack_user, the debugger could not find us and
     had to set __nptl_initial_report_events.  Propagate its setting.  */
  THREAD_SETMEM (pd, report_events, __nptl_initial_report_events);

  /* Install the cancellation signal handler.  If for some reason we
     cannot install the handler we do not abort.  Maybe we should, but
     it is only asynchronous cancellation which is affected.  */
  struct sigaction sa;
  sa.sa_sigaction = sigcancel_handler;
  sa.sa_flags = SA_SIGINFO;
  __sigemptyset (&sa.sa_mask);

  (void) __libc_sigaction (SIGCANCEL, &sa, NULL);

  /* Install the handle to change the threads' uid/gid.  */
  sa.sa_sigaction = sighandler_setxid;
  sa.sa_flags = SA_SIGINFO | SA_RESTART;

  (void) __libc_sigaction (SIGSETXID, &sa, NULL);

  /* The parent process might have left the signals blocked.  Just in
     case, unblock it.  We reuse the signal mask in the sigaction
     structure.  It is already cleared.  */
  __sigaddset (&sa.sa_mask, SIGCANCEL);
  __sigaddset (&sa.sa_mask, SIGSETXID);
  (void) INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_UNBLOCK, &sa.sa_mask,
			   NULL, _NSIG / 8);

  /* Get the size of the static and alignment requirements for the TLS
     block.  */
  size_t static_tls_align;
  _dl_get_tls_static_info (&__static_tls_size, &static_tls_align);

  /* Make sure the size takes all the alignments into account.  */
  if (STACK_ALIGN > static_tls_align)
    static_tls_align = STACK_ALIGN;
  __static_tls_align_m1 = static_tls_align - 1;

  __static_tls_size = roundup (__static_tls_size, static_tls_align);

  /* Determine the default allowed stack size.  This is the size used
     in case the user does not specify one.  */
  struct rlimit limit;
  if (getrlimit (RLIMIT_STACK, &limit) != 0
      || limit.rlim_cur == RLIM_INFINITY)
    /* The system limit is not usable.  Use an architecture-specific
       default.  */
    limit.rlim_cur = ARCH_STACK_DEFAULT_SIZE;
  else if (limit.rlim_cur < PTHREAD_STACK_MIN)
    /* The system limit is unusably small.
       Use the minimal size acceptable.  */
    limit.rlim_cur = PTHREAD_STACK_MIN;

  /* Do not exceed architecture specific default */
  if (limit.rlim_cur > ARCH_STACK_DEFAULT_SIZE)
    limit.rlim_cur = ARCH_STACK_DEFAULT_SIZE;

  /* Make sure it meets the minimum size that allocate_stack
     (allocatestack.c) will demand, which depends on the page size.  */
  #ifdef SHARED
  extern size_t GLRO(dl_pagesize);
  const uintptr_t pagesz = GLRO(dl_pagesize);
  #else
  const uintptr_t pagesz = sysconf (_SC_PAGESIZE);
  #endif
  const size_t minstack = pagesz + __static_tls_size + MINIMAL_REST_STACK;
  if (limit.rlim_cur < minstack)
    limit.rlim_cur = minstack;

  /* Round the resource limit up to page size.  */
  limit.rlim_cur = (limit.rlim_cur + pagesz - 1) & -pagesz;
  __default_stacksize = limit.rlim_cur;

#ifdef SHARED
  /* Transfer the old value from the dynamic linker's internal location.  */
  *__libc_dl_error_tsd () = *(*GL(dl_error_catch_tsd)) ();
  GL(dl_error_catch_tsd) = &__libc_dl_error_tsd;

#endif

  GL(dl_init_static_tls) = &__pthread_init_static_tls;

  /* Register the fork generation counter with the libc.  */
#ifndef TLS_MULTIPLE_THREADS_IN_TCB
  __libc_multiple_threads_ptr =
#endif
    __libc_pthread_init (&__fork_generation, __reclaim_stacks);

  /* Determine whether the machine is SMP or not.  */
  __is_smp = is_smp_system ();

  /* uClibc-specific stdio initialization for threads. */
  {
    FILE *fp;
    _stdio_user_locking = 0;       /* 2 if threading not initialized */
    for (fp = _stdio_openlist; fp != NULL; fp = fp->__nextopen) {
      if (fp->__user_locking != 1) {
        fp->__user_locking = 0;
      }
    }
  }
}
strong_alias (__pthread_initialize_minimal_internal,
	      __pthread_initialize_minimal)

size_t
__pthread_get_minstack (const pthread_attr_t *attr)
{
  return __static_tls_size + PTHREAD_STACK_MIN;
}