1 /* Support for an sbrk-like function that uses mmap.
2 Copyright 1992, 2000 Free Software Foundation, Inc.
4 Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com */
6 /* Copyright (c) 2010. The SimGrid Team.
7 * All rights reserved. */
9 /* This program is free software; you can redistribute it and/or modify it
10 * under the terms of the license (GNU LGPL) which comes with this package. */
13 #define MAP_ANONYMOUS MAP_ANON
17 #include <unistd.h> /* Prototypes for lseek */
27 #include "mmprivate.h"
29 /* Cache the pagesize for the current host machine. Note that if the host
30 does not readily provide a getpagesize() function, we need to emulate it
31 elsewhere, not clutter up this file with lots of kluges to try to figure
34 static size_t pagesize;
35 #if NEED_DECLARATION_GETPAGESIZE
36 extern int getpagesize (void);
39 #define PAGE_ALIGN(addr) (void*) (((long)(addr) + pagesize - 1) & \
42 /* Return MAP_PRIVATE if MDP represents /dev/zero. Otherwise, return
45 #define MAP_PRIVATE_OR_SHARED(MDP) (( MDP -> flags & MMALLOC_ANONYMOUS) \
49 /* Return MAP_ANONYMOUS if MDP uses anonymous mapping. Otherwise, return 0 */
51 #define MAP_IS_ANONYMOUS(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
55 /* Return -1 if MDP uses anonymous mapping. Otherwise, return MDP->FD */
56 #define MAP_ANON_OR_FD(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
60 /* Get core for the memory region specified by MDP, using SIZE as the
61 amount to either add to or subtract from the existing region. Works
62 like sbrk(), but using mmap(). */
65 __mmalloc_mmap_morecore (struct mdesc *mdp, int size)
68 off_t foffset; /* File offset at which new mapping will start */
69 size_t mapbytes; /* Number of bytes to map */
70 void* moveto; /* Address where we wish to move "break value" to */
71 void* mapto; /* Address we actually mapped to */
72 char buf = 0; /* Single byte to write to extend mapped file */
75 pagesize = getpagesize();
79 /* Just return the current "break" value. */
80 result = mdp -> breakval;
84 /* We are deallocating memory. If the amount requested would cause
85 us to try to deallocate back past the base of the mmap'd region
86 then do nothing, and return NULL. Otherwise, deallocate the
87 memory and return the old break value. */
88 if (((char*)mdp -> breakval) + size >= (char*)mdp -> base)
90 result = (void*) mdp -> breakval;
91 mdp -> breakval = (char*) mdp->breakval + size;
92 moveto = PAGE_ALIGN (mdp -> breakval);
93 munmap (moveto, (size_t) (((char*)mdp -> top) - ((char*)moveto)) - 1);
99 /* We are allocating memory. Make sure we have an open file
100 descriptor if not working with anonymous memory. */
101 if ( !(mdp->flags & MMALLOC_ANONYMOUS) && mdp -> fd < 0)
105 else if ((char*)mdp -> breakval + size > (char*)mdp -> top)
107 /* The request would move us past the end of the currently
108 mapped memory, so map in enough more memory to satisfy
109 the request. This means we also have to grow the mapped-to
110 file by an appropriate amount, since mmap cannot be used
112 moveto = PAGE_ALIGN ((char*)mdp -> breakval + size);
113 mapbytes = (char*)moveto - (char*)mdp -> top;
114 foffset = (char*)mdp -> top - (char*)mdp -> base;
117 /* FIXME: Test results of lseek() and write() */
118 lseek (mdp -> fd, foffset + mapbytes - 1, SEEK_SET);
119 write (mdp -> fd, &buf, 1);
122 /* Let's call mmap. Note that it is possible that mdp->top
123 is 0. In this case mmap will choose the address for us */
124 mapto = mmap (mdp->top, mapbytes, PROT_READ | PROT_WRITE,
125 MAP_PRIVATE_OR_SHARED(mdp) | MAP_IS_ANONYMOUS(mdp) | MAP_FIXED,
126 MAP_ANON_OR_FD(mdp), foffset);
128 if (mapto != (void*) -1){
131 mdp -> base = mdp -> breakval = mapto;
133 mdp -> top = PAGE_ALIGN ((char*)mdp -> breakval + size);
134 result = (void*) mdp -> breakval;
135 mdp -> breakval = (char*)mdp->breakval + size;
140 result = (void*) mdp -> breakval;
141 mdp -> breakval = (char*)mdp->breakval + size;
148 __mmalloc_remap_core (struct mdesc *mdp)
152 /* FIXME: Quick hack, needs error checking and other attention. */
154 base = mmap (mdp -> base, (char*)mdp -> top - (char*)mdp -> base,
155 PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE_OR_SHARED (mdp) | MAP_FIXED,
157 return ((void*) base);
161 mmalloc_findbase (int size)
168 flags = MAP_PRIVATE | MAP_ANONYMOUS;
172 flags = MAP_PRIVATE | MAP_FILE;
176 fd = open ("/dev/zero", O_RDWR);
179 return ((void*) NULL);
182 base = mmap (0, size, PROT_READ | PROT_WRITE, flags, fd, 0);
183 if (base != (void*) -1)
185 munmap (base, (size_t) size);
193 /* Don't allow mapping at address zero. We use that value
194 to signal an error return, and besides, it is useful to
195 catch NULL pointers if it is unmapped. Instead start
196 at the next page boundary. */
197 base = (void*)(long) getpagesize ();
199 else if (base == (void*) -1)
203 return ((void*) base);