glibc/nptl/pthread_getattr_np.c

/* Copyright (C) 2002, 2003 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, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <assert.h>
#include <errno.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
#include "pthreadP.h"
#include <lowlevellock.h>


int
pthread_getattr_np (thread_id, attr)
     pthread_t thread_id;
     pthread_attr_t *attr;
{
  struct pthread *thread = (struct pthread *) thread_id;
  struct pthread_attr *iattr = (struct pthread_attr *) attr;
  int ret = 0;

  /* We have to handle cancellation in the following code since we are
     locking another threads desriptor.  */
  pthread_cleanup_push ((void (*) (void *)) lll_unlock_wake_cb, &thread->lock);

  lll_lock (thread->lock);

  /* The thread library is responsible for keeping the values in the
     thread desriptor up-to-date in case the user changes them.  */
  memcpy (&iattr->schedparam, &thread->schedparam,
	  sizeof (struct sched_param));
  iattr->schedpolicy = thread->schedpolicy;

  /* Clear the flags work.  */
  iattr->flags = thread->flags;

  /* The thread might be detached by now.  */
  if (IS_DETACHED (thread))
    iattr->flags |= ATTR_FLAG_DETACHSTATE;

  /* This is the guardsize after adjusting it.  */
  iattr->guardsize = thread->guardsize;

  /* The sizes are subject to alignment.  */
  if (__builtin_expect (thread->stackblock != NULL, 1))
    {
      iattr->stacksize = thread->stackblock_size;
      iattr->stackaddr = (char *) thread->stackblock + iattr->stacksize;
    }
  else
    {
      /* No stack information available.  This must be for the initial
	 thread.  Get the info in some magical way.  */
      assert (thread->pid == thread->tid);

      /* Defined in ld.so.  */
      extern void *__libc_stack_end;

      /* Stack size limit.  */
      struct rlimit rl;

      /* The safest way to get the top of the stack is to read
	 /proc/self/maps and locate the line into which
	 __libc_stack_end falls.  */
      FILE *fp = fopen ("/proc/self/maps", "rc");
      if (fp == NULL)
	ret = errno;
      /* We need the limit of the stack in any case.  */
      else if (getrlimit (RLIMIT_STACK, &rl) != 0)
	ret = errno;
      else
	{
	  /* We need no locking.  */
	  __fsetlocking (fp, FSETLOCKING_BYCALLER);

	  /* Until we found an entry (which should always be the case)
	     mark the result as a failure.  */
	  ret = ENOENT;

	  char *line = NULL;
	  size_t linelen = 0;

	  while (! feof_unlocked (fp))
	    {
	      if (__getdelim (&line, &linelen, '\n', fp) <= 0)
		break;

	      uintptr_t from;
	      uintptr_t to;
	      if (sscanf (line, "%" SCNxPTR "-%" SCNxPTR, &from, &to) == 2
		  && from <= (uintptr_t) __libc_stack_end
		  && (uintptr_t) __libc_stack_end < to)
		{
		  /* Found the entry.  Now we have the info we need.  */
		  iattr->stacksize = rl.rlim_cur;
		  iattr->stackaddr = (void *) to;

		  /* We succeed and no need to look further.  */
		  ret = 0;
		  break;
		}
	    }

	  fclose (fp);
	  free (line);
	}
    }

  iattr->flags |= ATTR_FLAG_STACKADDR;

  lll_unlock (thread->lock);

  pthread_cleanup_pop (0);

  return ret;
}