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 #include <unistd.h> /* Prototypes for lseek */
23 #include "mmprivate.h"
25 /* Cache the pagesize for the current host machine. Note that if the host
26 does not readily provide a getpagesize() function, we need to emulate it
27 elsewhere, not clutter up this file with lots of kluges to try to figure
30 static size_t pagesize;
31 #if NEED_DECLARATION_GETPAGESIZE
32 extern int getpagesize (void);
35 #define PAGE_ALIGN(addr) (void*) (((long)(addr) + pagesize - 1) & \
38 /* Return MAP_PRIVATE if MDP represents /dev/zero. Otherwise, return
41 #define MAP_PRIVATE_OR_SHARED(MDP) (( MDP -> flags & MMALLOC_ANONYMOUS) \
45 /* Return MAP_ANONYMOUS if MDP uses anonymous mapping. Otherwise, return 0 */
47 #define MAP_IS_ANONYMOUS(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
51 /* Return -1 if MDP uses anonymous mapping. Otherwise, return MDP->FD */
52 #define MAP_ANON_OR_FD(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
56 /* Get core for the memory region specified by MDP, using SIZE as the
57 amount to either add to or subtract from the existing region. Works
58 like sbrk(), but using mmap(). */
61 __mmalloc_mmap_morecore (struct mdesc *mdp, int size)
64 off_t foffset; /* File offset at which new mapping will start */
65 size_t mapbytes; /* Number of bytes to map */
66 void* moveto; /* Address where we wish to move "break value" to */
67 void* mapto; /* Address we actually mapped to */
68 char buf = 0; /* Single byte to write to extend mapped file */
71 pagesize = getpagesize();
75 /* Just return the current "break" value. */
76 result = mdp -> breakval;
80 /* We are deallocating memory. If the amount requested would cause
81 us to try to deallocate back past the base of the mmap'd region
82 then do nothing, and return NULL. Otherwise, deallocate the
83 memory and return the old break value. */
84 if (((char*)mdp -> breakval) + size >= (char*)mdp -> base)
86 result = (void*) mdp -> breakval;
87 mdp -> breakval = (char*) mdp->breakval + size;
88 moveto = PAGE_ALIGN (mdp -> breakval);
89 munmap (moveto, (size_t) (((char*)mdp -> top) - ((char*)moveto)) - 1);
95 /* We are allocating memory. Make sure we have an open file
96 descriptor if not working with anonymous memory. */
97 if ( !(mdp->flags & MMALLOC_ANONYMOUS) && mdp -> fd < 0)
101 else if ((char*)mdp -> breakval + size > (char*)mdp -> top)
103 /* The request would move us past the end of the currently
104 mapped memory, so map in enough more memory to satisfy
105 the request. This means we also have to grow the mapped-to
106 file by an appropriate amount, since mmap cannot be used
108 moveto = PAGE_ALIGN ((char*)mdp -> breakval + size);
109 mapbytes = (char*)moveto - (char*)mdp -> top;
110 foffset = (char*)mdp -> top - (char*)mdp -> base;
113 /* FIXME: Test results of lseek() and write() */
114 lseek (mdp -> fd, foffset + mapbytes - 1, SEEK_SET);
115 write (mdp -> fd, &buf, 1);
118 /* Let's call mmap. Note that it is possible that mdp->top
119 is 0. In this case mmap will choose the address for us */
120 mapto = mmap (mdp->top, mapbytes, PROT_READ | PROT_WRITE,
121 MAP_PRIVATE_OR_SHARED(mdp) | MAP_IS_ANONYMOUS(mdp) | MAP_FIXED,
122 MAP_ANON_OR_FD(mdp), foffset);
124 if (mapto != (void*) -1){
127 mdp -> base = mdp -> breakval = mapto;
129 mdp -> top = PAGE_ALIGN ((char*)mdp -> breakval + size);
130 result = (void*) mdp -> breakval;
131 mdp -> breakval = (char*)mdp->breakval + size;
136 result = (void*) mdp -> breakval;
137 mdp -> breakval = (char*)mdp->breakval + size;
144 __mmalloc_remap_core (struct mdesc *mdp)
148 /* FIXME: Quick hack, needs error checking and other attention. */
150 base = mmap (mdp -> base, (char*)mdp -> top - (char*)mdp -> base,
151 PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE_OR_SHARED (mdp) | MAP_FIXED,
153 return ((void*) base);
157 mmalloc_findbase (int size)
164 flags = MAP_PRIVATE | MAP_ANONYMOUS;
168 flags = MAP_PRIVATE | MAP_FILE;
172 fd = open ("/dev/zero", O_RDWR);
175 return ((void*) NULL);
178 base = mmap (0, size, PROT_READ | PROT_WRITE, flags, fd, 0);
179 if (base != (void*) -1)
181 munmap (base, (size_t) size);
189 /* Don't allow mapping at address zero. We use that value
190 to signal an error return, and besides, it is useful to
191 catch NULL pointers if it is unmapped. Instead start
192 at the next page boundary. */
193 base = (void*) getpagesize ();
195 else if (base == (void*) -1)
199 return ((void*) base);