src/sheap.c

   1 /* simulate `sbrk' with an array in .bss, for `unexec' support for Cygwin;
   2    complete rewrite of xemacs Cygwin `unexec' code
   3
   4    Copyright (C) 2004-2014 Free Software Foundation, Inc.
   5
   6 This file is part of GNU Emacs.
   7
   8 GNU Emacs is free software: you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation, either version 3 of the License, or
  11 (at your option) any later version.
  12
  13 GNU Emacs is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include <stdio.h>
  23
  24 #include "lisp.h"
  25
  26 #include <unistd.h>
  27
  28 #ifdef __x86_64__
  29 #ifdef ENABLE_CHECKING
  30 #define STATIC_HEAP_SIZE        (28 * 1024 * 1024)
  31 #else
  32 #define STATIC_HEAP_SIZE        (19 * 1024 * 1024)
  33 #endif
  34 #else  /* x86 */
  35 #ifdef ENABLE_CHECKING
  36 #define STATIC_HEAP_SIZE        (18 * 1024 * 1024)
  37 #else
  38 #define STATIC_HEAP_SIZE        (13 * 1024 * 1024)
  39 #endif
  40 #endif  /* x86 */
  41
  42 int debug_sheap = 0;
  43
  44 #define BLOCKSIZE 4096
  45
  46 char bss_sbrk_buffer[STATIC_HEAP_SIZE];
  47 char *bss_sbrk_buffer_end = bss_sbrk_buffer + STATIC_HEAP_SIZE;
  48 char *bss_sbrk_ptr;
  49 char *max_bss_sbrk_ptr;
  50 int bss_sbrk_did_unexec;
  51
  52 void *
  53 bss_sbrk (ptrdiff_t request_size)
  54 {
  55   if (!bss_sbrk_ptr)
  56     {
  57       max_bss_sbrk_ptr = bss_sbrk_ptr = bss_sbrk_buffer;
  58 #ifdef CYGWIN
  59       sbrk (BLOCKSIZE);         /* force space for fork to work */
  60 #endif
  61     }
  62
  63   if (!(int) request_size)
  64     {
  65       return (bss_sbrk_ptr);
  66     }
  67   else if (bss_sbrk_ptr + (int) request_size < bss_sbrk_buffer)
  68     {
  69       printf
  70         ("attempt to free too much: avail %d used %d failed request %d\n",
  71          STATIC_HEAP_SIZE, bss_sbrk_ptr - bss_sbrk_buffer,
  72          (int) request_size);
  73       exit (-1);
  74       return 0;
  75     }
  76   else if (bss_sbrk_ptr + (int) request_size >
  77            bss_sbrk_buffer + STATIC_HEAP_SIZE)
  78     {
  79       printf ("static heap exhausted: avail %d used %d failed request %d\n",
  80               STATIC_HEAP_SIZE,
  81               bss_sbrk_ptr - bss_sbrk_buffer, (int) request_size);
  82       exit (-1);
  83       return 0;
  84     }
  85   else if ((int) request_size < 0)
  86     {
  87       bss_sbrk_ptr += (int) request_size;
  88       if (debug_sheap)
  89         printf ("freed size %d\n", request_size);
  90       return bss_sbrk_ptr;
  91     }
  92   else
  93     {
  94       char *ret = bss_sbrk_ptr;
  95       if (debug_sheap)
  96         printf ("allocated 0x%08x size %d\n", ret, request_size);
  97       bss_sbrk_ptr += (int) request_size;
  98       if (bss_sbrk_ptr > max_bss_sbrk_ptr)
  99         max_bss_sbrk_ptr = bss_sbrk_ptr;
 100       return ret;
 101     }
 102 }
 103
 104 void
 105 report_sheap_usage (int die_if_pure_storage_exceeded)
 106 {
 107   char buf[200];
 108   sprintf (buf, "Maximum static heap usage: %d of %d bytes",
 109            max_bss_sbrk_ptr - bss_sbrk_buffer, STATIC_HEAP_SIZE);
 110   /* Don't log messages, cause at this point, we're not allowed to create
 111      buffers.  */
 112   message1_nolog (buf);
 113 }