| /* Support for an sbrk-like function that uses mmap. |
| Copyright 1992, 2000 Free Software Foundation, Inc. |
| |
| Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com |
| |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Library General Public License as |
| published by the Free Software Foundation; either version 2 of the |
| License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Library General Public License for more details. |
| |
| You should have received a copy of the GNU Library General Public |
| License along with the GNU C Library; see the file COPYING.LIB. If |
| not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, |
| Boston, MA 02111-1307, USA. */ |
| |
| #if defined(HAVE_MMAP) |
| |
| #ifdef HAVE_UNISTD_H |
| #include <unistd.h> /* Prototypes for lseek */ |
| #endif |
| #include <stdio.h> |
| #include <fcntl.h> |
| #include <sys/mman.h> |
| |
| #ifndef SEEK_SET |
| #define SEEK_SET 0 |
| #endif |
| |
| #include "mmprivate.h" |
| |
| /* Cache the pagesize for the current host machine. Note that if the host |
| does not readily provide a getpagesize() function, we need to emulate it |
| elsewhere, not clutter up this file with lots of kluges to try to figure |
| it out. */ |
| |
| static size_t pagesize; |
| #if NEED_DECLARATION_GETPAGESIZE |
| extern int getpagesize PARAMS ((void)); |
| #endif |
| |
| #define PAGE_ALIGN(addr) (caddr_t) (((long)(addr) + pagesize - 1) & \ |
| ~(pagesize - 1)) |
| |
| /* Get core for the memory region specified by MDP, using SIZE as the |
| amount to either add to or subtract from the existing region. Works |
| like sbrk(), but using mmap(). */ |
| |
| PTR |
| __mmalloc_mmap_morecore (mdp, size) |
| struct mdesc *mdp; |
| int size; |
| { |
| PTR result = NULL; |
| off_t foffset; /* File offset at which new mapping will start */ |
| size_t mapbytes; /* Number of bytes to map */ |
| caddr_t moveto; /* Address where we wish to move "break value" to */ |
| caddr_t mapto; /* Address we actually mapped to */ |
| char buf = 0; /* Single byte to write to extend mapped file */ |
| |
| if (pagesize == 0) |
| { |
| pagesize = getpagesize (); |
| } |
| if (size == 0) |
| { |
| /* Just return the current "break" value. */ |
| result = mdp -> breakval; |
| } |
| else if (size < 0) |
| { |
| /* We are deallocating memory. If the amount requested would cause |
| us to try to deallocate back past the base of the mmap'd region |
| then do nothing, and return NULL. Otherwise, deallocate the |
| memory and return the old break value. */ |
| if (mdp -> breakval + size >= mdp -> base) |
| { |
| result = (PTR) mdp -> breakval; |
| mdp -> breakval += size; |
| moveto = PAGE_ALIGN (mdp -> breakval); |
| munmap (moveto, (size_t) (mdp -> top - moveto)); |
| mdp -> top = moveto; |
| } |
| } |
| else |
| { |
| /* We are allocating memory. Make sure we have an open file |
| descriptor and then go on to get the memory. */ |
| if (mdp -> fd < 0) |
| { |
| result = NULL; |
| } |
| else if (mdp -> breakval + size > mdp -> top) |
| { |
| /* The request would move us past the end of the currently |
| mapped memory, so map in enough more memory to satisfy |
| the request. This means we also have to grow the mapped-to |
| file by an appropriate amount, since mmap cannot be used |
| to extend a file. */ |
| moveto = PAGE_ALIGN (mdp -> breakval + size); |
| mapbytes = moveto - mdp -> top; |
| foffset = mdp -> top - mdp -> base; |
| /* FIXME: Test results of lseek() and write() */ |
| lseek (mdp -> fd, foffset + mapbytes - 1, SEEK_SET); |
| write (mdp -> fd, &buf, 1); |
| if (mdp -> base == 0) |
| { |
| /* Let mmap pick the map start address */ |
| mapto = mmap (0, mapbytes, PROT_READ | PROT_WRITE, |
| MAP_SHARED, mdp -> fd, foffset); |
| if (mapto != (caddr_t) -1) |
| { |
| mdp -> base = mdp -> breakval = mapto; |
| mdp -> top = mdp -> base + mapbytes; |
| result = (PTR) mdp -> breakval; |
| mdp -> breakval += size; |
| } |
| } |
| else |
| { |
| mapto = mmap (mdp -> top, mapbytes, PROT_READ | PROT_WRITE, |
| MAP_SHARED | MAP_FIXED, mdp -> fd, foffset); |
| if (mapto == mdp -> top) |
| { |
| mdp -> top = moveto; |
| result = (PTR) mdp -> breakval; |
| mdp -> breakval += size; |
| } |
| } |
| } |
| else |
| { |
| result = (PTR) mdp -> breakval; |
| mdp -> breakval += size; |
| } |
| } |
| return (result); |
| } |
| |
| PTR |
| __mmalloc_remap_core (mdp) |
| struct mdesc *mdp; |
| { |
| caddr_t base; |
| |
| /* FIXME: Quick hack, needs error checking and other attention. */ |
| |
| base = mmap (mdp -> base, mdp -> top - mdp -> base, |
| PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, |
| mdp -> fd, 0); |
| return ((PTR) base); |
| } |
| |
| PTR |
| mmalloc_findbase (size) |
| int size; |
| { |
| int fd; |
| int flags; |
| caddr_t base = NULL; |
| |
| #ifdef MAP_ANONYMOUS |
| flags = MAP_SHARED | MAP_ANONYMOUS; |
| fd = -1; |
| #else |
| #ifdef MAP_FILE |
| flags = MAP_SHARED | MAP_FILE; |
| #else |
| flags = MAP_SHARED; |
| #endif |
| fd = open ("/dev/zero", O_RDWR); |
| if (fd != -1) |
| { |
| return ((PTR) NULL); |
| } |
| #endif |
| base = mmap (0, size, PROT_READ | PROT_WRITE, flags, fd, 0); |
| if (base != (caddr_t) -1) |
| { |
| munmap (base, (size_t) size); |
| } |
| if (fd != -1) |
| { |
| close (fd); |
| } |
| if (base == 0) |
| { |
| /* Don't allow mapping at address zero. We use that value |
| to signal an error return, and besides, it is useful to |
| catch NULL pointers if it is unmapped. Instead start |
| at the next page boundary. */ |
| base = (caddr_t) getpagesize (); |
| } |
| else if (base == (caddr_t) -1) |
| { |
| base = NULL; |
| } |
| return ((PTR) base); |
| } |
| |
| #else /* defined(HAVE_MMAP) */ |
| /* Prevent "empty translation unit" warnings from the idiots at X3J11. */ |
| static char ansi_c_idiots = 69; |
| #endif /* defined(HAVE_MMAP) */ |