sysdeps/mach/hurd/brk.c

   1 /* Copyright (C) 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <errno.h>
  21 #include <hurd.h>
  22 #include <hurd/resource.h>
  23 #include <cthreads.h>           /* For `struct mutex'.  */
  24
  25
  26 /* Initial maximum size of the data segment (32MB, which is arbitrary).  */
  27 #define DATA_SIZE       (32 * 1024 * 1024)
  28
  29
  30 /* Up to the page including this address is allocated from the kernel.
  31    This address is the data resource limit.  */
  32 vm_address_t _hurd_data_end;
  33
  34 /* Up to this address is actually available to the user.
  35    Pages beyond the one containing this address allow no access.  */
  36 vm_address_t _hurd_brk;
  37
  38 struct mutex _hurd_brk_lock;
  39
  40 extern int __data_start, _end;
  41
  42
  43 /* Set the end of the process's data space to INADDR.
  44    Return 0 if successful, -1 if not.  */
  45 int
  46 DEFUN(__brk, (inaddr), PTR inaddr)
  47 {
  48   int ret;
  49   HURD_CRITICAL_BEGIN;
  50   __mutex_lock (&_hurd_brk_lock);
  51   ret = _hurd_set_brk ((vm_address_t) inaddr);
  52   __mutex_unlock (&_hurd_brk_lock);
  53   HURD_CRITICAL_END;
  54   return ret;
  55 }
  56 weak_alias (__brk, brk)
  57
  58
  59 int
  60 _hurd_set_brk (vm_address_t addr)
  61 {
  62   error_t err;
  63   vm_address_t pagend = round_page (addr);
  64   vm_address_t pagebrk = round_page (_hurd_brk);
  65   long int rlimit;
  66
  67   if (pagend <= pagebrk)
  68     {
  69       if (pagend < pagebrk)
  70         /* Make that memory inaccessible.  */
  71         __vm_protect (__mach_task_self (), pagend, pagebrk - pagend,
  72                       0, VM_PROT_NONE);
  73       _hurd_brk = addr;
  74       return 0;
  75     }
  76
  77   __mutex_lock (&_hurd_rlimit_lock);
  78   rlimit = _hurd_rlimits[RLIMIT_DATA].rlim_cur;
  79   __mutex_unlock (&_hurd_rlimit_lock);
  80
  81   if (addr - (vm_address_t) &__data_start > rlimit)
  82     {
  83       /* Need to increase the resource limit.  */
  84       errno = ENOMEM;
  85       return -1;
  86     }
  87
  88   /* Make the memory accessible.  */
  89   if (err = __vm_protect (__mach_task_self (), pagebrk, pagend - pagebrk,
  90                           0, VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE))
  91     {
  92       errno = err;
  93       return -1;
  94     }
  95
  96   _hurd_brk = addr;
  97   return 0;
  98 }
  99
 100 static void
 101 init_brk (void)
 102 {
 103   vm_address_t pagend;
 104
 105   __mutex_init (&_hurd_brk_lock);
 106
 107   /* If _hurd_brk is already set, don't change it.  The assumption is that
 108      it was set in a previous run before something like Emacs's unexec was
 109      called and dumped all the data up to the break at that point.  */
 110   if (_hurd_brk == 0)
 111     _hurd_brk = (vm_address_t) &_end;
 112
 113   pagend = round_page (_hurd_brk);
 114
 115   _hurd_data_end = (vm_address_t) &__data_start + DATA_SIZE;
 116
 117   if (pagend < _hurd_data_end)
 118     {
 119       /* We use vm_map to allocate and change permissions atomically.  */
 120       if (__vm_map (__mach_task_self (), &pagend, _hurd_data_end - pagend,
 121                     0, 0, MACH_PORT_NULL, 0, 0,
 122                     0, VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE,
 123                     VM_INHERIT_COPY))
 124         /* Couldn't allocate the memory.  The break will be very short.  */
 125         _hurd_data_end = pagend;
 126     }
 127
 128   (void) &init_brk;             /* Avoid ``defined but not used'' warning.  */
 129 }
 130 text_set_element (_hurd_preinit_hook, init_brk);