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) 2004-2013 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_ptr;
  48 char *max_bss_sbrk_ptr;
  49 int bss_sbrk_did_unexec;
  50
  51 void *
  52 bss_sbrk (ptrdiff_t request_size)
  53 {
  54   if (!bss_sbrk_ptr)
  55     {
  56       max_bss_sbrk_ptr = bss_sbrk_ptr = bss_sbrk_buffer;
  57 #ifdef CYGWIN
  58       sbrk (BLOCKSIZE);         /* force space for fork to work */
  59 #endif
  60     }
  61
  62   if (!(int) request_size)
  63     {
  64       return (bss_sbrk_ptr);
  65     }
  66   else if (bss_sbrk_ptr + (int) request_size < bss_sbrk_buffer)
  67     {
  68       printf
  69         ("attempt to free too much: avail %d used %d failed request %d\n",
  70          STATIC_HEAP_SIZE, bss_sbrk_ptr - bss_sbrk_buffer,
  71          (int) request_size);
  72       exit (-1);
  73       return 0;
  74     }
  75   else if (bss_sbrk_ptr + (int) request_size >
  76            bss_sbrk_buffer + STATIC_HEAP_SIZE)
  77     {
  78       printf ("static heap exhausted: avail %d used %d failed request %d\n",
  79               STATIC_HEAP_SIZE,
  80               bss_sbrk_ptr - bss_sbrk_buffer, (int) request_size);
  81       exit (-1);
  82       return 0;
  83     }
  84   else if ((int) request_size < 0)
  85     {
  86       bss_sbrk_ptr += (int) request_size;
  87       if (debug_sheap)
  88         printf ("freed size %d\n", request_size);
  89       return bss_sbrk_ptr;
  90     }
  91   else
  92     {
  93       char *ret = bss_sbrk_ptr;
  94       if (debug_sheap)
  95         printf ("allocated 0x%08x size %d\n", ret, request_size);
  96       bss_sbrk_ptr += (int) request_size;
  97       if (bss_sbrk_ptr > max_bss_sbrk_ptr)
  98         max_bss_sbrk_ptr = bss_sbrk_ptr;
  99       return ret;
 100     }
 101 }
 102
 103 void
 104 report_sheap_usage (int die_if_pure_storage_exceeded)
 105 {
 106   char buf[200];
 107   sprintf (buf, "Maximum static heap usage: %d of %d bytes",
 108            max_bss_sbrk_ptr - bss_sbrk_buffer, STATIC_HEAP_SIZE);
 109   /* Don't log messages, cause at this point, we're not allowed to create
 110      buffers.  */
 111   message1_nolog (buf);
 112 }