sysdeps/mach/hurd/brk.c

   1 /* Copyright (C) 1991,92,93,94,95,96,97,99,2000 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <errno.h>
  20 #include <hurd.h>
  21 #include <hurd/resource.h>
  22 #include <cthreads.h>           /* For `struct mutex'.  */
  23
  24
  25 /* Initial maximum size of the data segment (this is arbitrary).  */
  26 #define DATA_SIZE       (128 * 1024 * 1024)
  27
  28 /* Up to the page including this address is allocated from the kernel.
  29    This address is the data resource limit.  */
  30 vm_address_t _hurd_data_end;
  31
  32 /* Up to this address is actually available to the user.
  33    Pages beyond the one containing this address allow no access.  */
  34 vm_address_t _hurd_brk = 0;
  35
  36 /* This name is used by the Linux crtbeginS.o for reasons you don't even
  37    want to think about it.  It's just easier to provide some definition for
  38    it than even to explain the braindamage involved.  */
  39 weak_alias (_hurd_brk, ___brk_addr)
  40
  41 struct mutex _hurd_brk_lock;
  42
  43 extern int __data_start, _end;
  44 weak_extern (__data_start)
  45 static vm_address_t static_data_start;
  46
  47
  48 /* Set the end of the process's data space to INADDR.
  49    Return 0 if successful, -1 if not.  */
  50 int
  51 __brk (void *inaddr)
  52 {
  53   int ret;
  54   HURD_CRITICAL_BEGIN;
  55   __mutex_lock (&_hurd_brk_lock);
  56   ret = _hurd_set_brk ((vm_address_t) inaddr);
  57   __mutex_unlock (&_hurd_brk_lock);
  58   HURD_CRITICAL_END;
  59   return ret;
  60 }
  61 weak_alias (__brk, brk)
  62
  63
  64 int
  65 _hurd_set_brk (vm_address_t addr)
  66 {
  67   error_t err;
  68   vm_address_t pagend = round_page (addr);
  69   vm_address_t pagebrk = round_page (_hurd_brk);
  70   long int rlimit;
  71
  72   if (pagend <= pagebrk)
  73     {
  74       if (pagend < pagebrk)
  75         {
  76           /* XXX wish this were atomic... */
  77           /* First deallocate the memory to release its backing space.  */
  78           __vm_deallocate (__mach_task_self (), pagend, pagebrk - pagend);
  79           /* Now reallocate it with no access allowed.  */
  80           err = __vm_map (__mach_task_self (),
  81                           &pagend, pagebrk - pagend,
  82                           0, 0, MACH_PORT_NULL, 0, 0,
  83                           0, VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE,
  84                           VM_INHERIT_COPY);
  85           /* XXX what if error? */
  86         }
  87       _hurd_brk = addr;
  88       return 0;
  89     }
  90
  91   __mutex_lock (&_hurd_rlimit_lock);
  92   rlimit = _hurd_rlimits[RLIMIT_DATA].rlim_cur;
  93   __mutex_unlock (&_hurd_rlimit_lock);
  94
  95   if (addr - static_data_start > rlimit)
  96     {
  97       /* Need to increase the resource limit.  */
  98       errno = ENOMEM;
  99       return -1;
 100     }
 101
 102   if (pagend > _hurd_data_end)
 103     {
 104       /* We didn't allocate enough space!  Hopefully we can get some more!  */
 105       err = __vm_allocate (__mach_task_self (), &pagebrk, pagend - pagebrk, 0);
 106       if (! err)
 107         _hurd_data_end = pagend;
 108     }
 109   else
 110     /* Make the memory accessible.  */
 111     err = __vm_protect (__mach_task_self (), pagebrk, pagend - pagebrk,
 112                         0, VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE);
 113
 114   if (err)
 115     return __hurd_fail (err);
 116
 117   _hurd_brk = addr;
 118   return 0;
 119 }
 120
 121 static void
 122 init_brk (void)
 123 {
 124   vm_address_t pagend;
 125
 126   __mutex_init (&_hurd_brk_lock);
 127
 128   static_data_start = (vm_address_t) (&__data_start ?: &_end);
 129
 130   /* If _hurd_brk is already set, don't change it.  The assumption is that
 131      it was set in a previous run before something like Emacs's unexec was
 132      called and dumped all the data up to the break at that point.  */
 133   if (_hurd_brk == 0)
 134     _hurd_brk = (vm_address_t) &_end;
 135
 136   pagend = round_page (_hurd_brk);
 137
 138   _hurd_data_end = round_page (static_data_start + DATA_SIZE);
 139
 140   if (pagend < _hurd_data_end)
 141     {
 142       /* We use vm_map to allocate and change permissions atomically.  */
 143       if (__vm_map (__mach_task_self (), &pagend, _hurd_data_end - pagend,
 144                     0, 0, MACH_PORT_NULL, 0, 0,
 145                     0, VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE,
 146                     VM_INHERIT_COPY))
 147         /* Couldn't allocate the memory.  The break will be very short.  */
 148         _hurd_data_end = pagend;
 149     }
 150
 151   (void) &init_brk;             /* Avoid ``defined but not used'' warning.  */
 152 }
 153 text_set_element (_hurd_preinit_hook, init_brk);