| 1 | /* Support for an sbrk-like function that uses mmap. |
| 2 | Copyright 1992, 2000 Free Software Foundation, Inc. |
| 3 | |
| 4 | Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com |
| 5 | |
| 6 | This file is part of the GNU C Library. |
| 7 | |
| 8 | The GNU C Library is free software; you can redistribute it and/or |
| 9 | modify it under the terms of the GNU Library General Public License as |
| 10 | published by the Free Software Foundation; either version 2 of the |
| 11 | License, or (at your option) any later version. |
| 12 | |
| 13 | The GNU C Library 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 GNU |
| 16 | Library General Public License for more details. |
| 17 | |
| 18 | You should have received a copy of the GNU Library General Public |
| 19 | License along with the GNU C Library; see the file COPYING.LIB. If |
| 20 | not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, |
| 21 | Boston, MA 02111-1307, USA. */ |
| 22 | |
| 23 | #if defined(HAVE_MMAP) |
| 24 | |
| 25 | #ifdef HAVE_UNISTD_H |
| 26 | #include <unistd.h> /* Prototypes for lseek */ |
| 27 | #endif |
| 28 | #include <stdio.h> |
| 29 | #include <fcntl.h> |
| 30 | #include <sys/mman.h> |
| 31 | |
| 32 | #ifndef SEEK_SET |
| 33 | #define SEEK_SET 0 |
| 34 | #endif |
| 35 | |
| 36 | #include "mmprivate.h" |
| 37 | |
| 38 | /* Cache the pagesize for the current host machine. Note that if the host |
| 39 | does not readily provide a getpagesize() function, we need to emulate it |
| 40 | elsewhere, not clutter up this file with lots of kluges to try to figure |
| 41 | it out. */ |
| 42 | |
| 43 | static size_t pagesize; |
| 44 | #if NEED_DECLARATION_GETPAGESIZE |
| 45 | extern int getpagesize PARAMS ((void)); |
| 46 | #endif |
| 47 | |
| 48 | #define PAGE_ALIGN(addr) (caddr_t) (((long)(addr) + pagesize - 1) & \ |
| 49 | ~(pagesize - 1)) |
| 50 | |
| 51 | /* Get core for the memory region specified by MDP, using SIZE as the |
| 52 | amount to either add to or subtract from the existing region. Works |
| 53 | like sbrk(), but using mmap(). */ |
| 54 | |
| 55 | PTR |
| 56 | __mmalloc_mmap_morecore (mdp, size) |
| 57 | struct mdesc *mdp; |
| 58 | int size; |
| 59 | { |
| 60 | PTR result = NULL; |
| 61 | off_t foffset; /* File offset at which new mapping will start */ |
| 62 | size_t mapbytes; /* Number of bytes to map */ |
| 63 | caddr_t moveto; /* Address where we wish to move "break value" to */ |
| 64 | caddr_t mapto; /* Address we actually mapped to */ |
| 65 | char buf = 0; /* Single byte to write to extend mapped file */ |
| 66 | |
| 67 | if (pagesize == 0) |
| 68 | { |
| 69 | pagesize = getpagesize (); |
| 70 | } |
| 71 | if (size == 0) |
| 72 | { |
| 73 | /* Just return the current "break" value. */ |
| 74 | result = mdp -> breakval; |
| 75 | } |
| 76 | else if (size < 0) |
| 77 | { |
| 78 | /* We are deallocating memory. If the amount requested would cause |
| 79 | us to try to deallocate back past the base of the mmap'd region |
| 80 | then do nothing, and return NULL. Otherwise, deallocate the |
| 81 | memory and return the old break value. */ |
| 82 | if (mdp -> breakval + size >= mdp -> base) |
| 83 | { |
| 84 | result = (PTR) mdp -> breakval; |
| 85 | mdp -> breakval += size; |
| 86 | moveto = PAGE_ALIGN (mdp -> breakval); |
| 87 | munmap (moveto, (size_t) (mdp -> top - moveto)); |
| 88 | mdp -> top = moveto; |
| 89 | } |
| 90 | } |
| 91 | else |
| 92 | { |
| 93 | /* We are allocating memory. Make sure we have an open file |
| 94 | descriptor and then go on to get the memory. */ |
| 95 | if (mdp -> fd < 0) |
| 96 | { |
| 97 | result = NULL; |
| 98 | } |
| 99 | else if (mdp -> breakval + size > mdp -> top) |
| 100 | { |
| 101 | /* The request would move us past the end of the currently |
| 102 | mapped memory, so map in enough more memory to satisfy |
| 103 | the request. This means we also have to grow the mapped-to |
| 104 | file by an appropriate amount, since mmap cannot be used |
| 105 | to extend a file. */ |
| 106 | moveto = PAGE_ALIGN (mdp -> breakval + size); |
| 107 | mapbytes = moveto - mdp -> top; |
| 108 | foffset = mdp -> top - mdp -> base; |
| 109 | /* FIXME: Test results of lseek() and write() */ |
| 110 | lseek (mdp -> fd, foffset + mapbytes - 1, SEEK_SET); |
| 111 | write (mdp -> fd, &buf, 1); |
| 112 | if (mdp -> base == 0) |
| 113 | { |
| 114 | /* Let mmap pick the map start address */ |
| 115 | mapto = mmap (0, mapbytes, PROT_READ | PROT_WRITE, |
| 116 | MAP_SHARED, mdp -> fd, foffset); |
| 117 | if (mapto != (caddr_t) -1) |
| 118 | { |
| 119 | mdp -> base = mdp -> breakval = mapto; |
| 120 | mdp -> top = mdp -> base + mapbytes; |
| 121 | result = (PTR) mdp -> breakval; |
| 122 | mdp -> breakval += size; |
| 123 | } |
| 124 | } |
| 125 | else |
| 126 | { |
| 127 | mapto = mmap (mdp -> top, mapbytes, PROT_READ | PROT_WRITE, |
| 128 | MAP_SHARED | MAP_FIXED, mdp -> fd, foffset); |
| 129 | if (mapto == mdp -> top) |
| 130 | { |
| 131 | mdp -> top = moveto; |
| 132 | result = (PTR) mdp -> breakval; |
| 133 | mdp -> breakval += size; |
| 134 | } |
| 135 | } |
| 136 | } |
| 137 | else |
| 138 | { |
| 139 | result = (PTR) mdp -> breakval; |
| 140 | mdp -> breakval += size; |
| 141 | } |
| 142 | } |
| 143 | return (result); |
| 144 | } |
| 145 | |
| 146 | PTR |
| 147 | __mmalloc_remap_core (mdp) |
| 148 | struct mdesc *mdp; |
| 149 | { |
| 150 | caddr_t base; |
| 151 | |
| 152 | /* FIXME: Quick hack, needs error checking and other attention. */ |
| 153 | |
| 154 | base = mmap (mdp -> base, mdp -> top - mdp -> base, |
| 155 | PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, |
| 156 | mdp -> fd, 0); |
| 157 | return ((PTR) base); |
| 158 | } |
| 159 | |
| 160 | PTR |
| 161 | mmalloc_findbase (size) |
| 162 | int size; |
| 163 | { |
| 164 | int fd; |
| 165 | int flags; |
| 166 | caddr_t base = NULL; |
| 167 | |
| 168 | #ifdef MAP_ANONYMOUS |
| 169 | flags = MAP_SHARED | MAP_ANONYMOUS; |
| 170 | fd = -1; |
| 171 | #else |
| 172 | #ifdef MAP_FILE |
| 173 | flags = MAP_SHARED | MAP_FILE; |
| 174 | #else |
| 175 | flags = MAP_SHARED; |
| 176 | #endif |
| 177 | fd = open ("/dev/zero", O_RDWR); |
| 178 | if (fd != -1) |
| 179 | { |
| 180 | return ((PTR) NULL); |
| 181 | } |
| 182 | #endif |
| 183 | base = mmap (0, size, PROT_READ | PROT_WRITE, flags, fd, 0); |
| 184 | if (base != (caddr_t) -1) |
| 185 | { |
| 186 | munmap (base, (size_t) size); |
| 187 | } |
| 188 | if (fd != -1) |
| 189 | { |
| 190 | close (fd); |
| 191 | } |
| 192 | if (base == 0) |
| 193 | { |
| 194 | /* Don't allow mapping at address zero. We use that value |
| 195 | to signal an error return, and besides, it is useful to |
| 196 | catch NULL pointers if it is unmapped. Instead start |
| 197 | at the next page boundary. */ |
| 198 | base = (caddr_t) getpagesize (); |
| 199 | } |
| 200 | else if (base == (caddr_t) -1) |
| 201 | { |
| 202 | base = NULL; |
| 203 | } |
| 204 | return ((PTR) base); |
| 205 | } |
| 206 | |
| 207 | #else /* defined(HAVE_MMAP) */ |
| 208 | /* Prevent "empty translation unit" warnings from the idiots at X3J11. */ |
| 209 | static char ansi_c_idiots = 69; |
| 210 | #endif /* defined(HAVE_MMAP) */ |