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"
30 /* Cache the pagesize for the current host machine. Note that if the host
31 does not readily provide a getpagesize() function, we need to emulate it
32 elsewhere, not clutter up this file with lots of kluges to try to figure
35 static size_t pagesize;
36 #if NEED_DECLARATION_GETPAGESIZE
37 extern int getpagesize(void);
40 #define PAGE_ALIGN(addr) (void*) (((long)(addr) + pagesize - 1) & \
43 /* Return MAP_PRIVATE if MDP represents /dev/zero. Otherwise, return
46 #define MAP_PRIVATE_OR_SHARED(MDP) (( MDP -> flags & MMALLOC_ANONYMOUS) \
50 /* Return MAP_ANONYMOUS if MDP uses anonymous mapping. Otherwise, return 0 */
52 #define MAP_IS_ANONYMOUS(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
56 /* Return -1 if MDP uses anonymous mapping. Otherwise, return MDP->FD */
57 #define MAP_ANON_OR_FD(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
61 /* Get core for the memory region specified by MDP, using SIZE as the
62 amount to either add to or subtract from the existing region. Works
63 like sbrk(), but using mmap(). */
65 void *__mmalloc_mmap_morecore(struct mdesc *mdp, int size)
69 off_t foffset; /* File offset at which new mapping will start */
70 size_t mapbytes; /* Number of bytes to map */
71 void *moveto; /* Address where we wish to move "break value" to */
72 void *mapto; /* Address we actually mapped to */
73 char buf = 0; /* Single byte to write to extend mapped file */
76 pagesize = getpagesize();
79 /* Just return the current "break" value. */
80 result = mdp->breakval;
82 } else if (size < 0) {
83 /* We are deallocating memory. If the amount requested would cause
84 us to try to deallocate back past the base of the mmap'd region
85 then do nothing, and return NULL. Otherwise, deallocate the
86 memory and return the old break value. */
87 if (((char *) mdp->breakval) + size >= (char *) mdp->base) {
88 result = (void *) mdp->breakval;
89 mdp->breakval = (char *) mdp->breakval + size;
90 moveto = PAGE_ALIGN(mdp->breakval);
92 (size_t) (((char *) mdp->top) - ((char *) moveto)) - 1);
96 /* We are allocating memory. Make sure we have an open file
97 descriptor if not working with anonymous memory. */
98 if (!(mdp->flags & MMALLOC_ANONYMOUS) && mdp->fd < 0) {
99 THROWF(system_error,0,"mmap file descriptor <0 (%d), without MMALLOC_ANONYMOUS being in the flags",mdp->fd);
101 } else if ((char *) mdp->breakval + size > (char *) mdp->top) {
102 /* The request would move us past the end of the currently
103 mapped memory, so map in enough more memory to satisfy
104 the request. This means we also have to grow the mapped-to
105 file by an appropriate amount, since mmap cannot be used
107 moveto = PAGE_ALIGN((char *) mdp->breakval + size);
108 mapbytes = (char *) moveto - (char *) mdp->top;
109 foffset = (char *) mdp->top - (char *) mdp->base;
112 /* FIXME: Test results of lseek() and write() */
113 lseek(mdp->fd, foffset + mapbytes - 1, SEEK_SET);
114 test = write(mdp->fd, &buf, 1);
117 /* Let's call mmap. Note that it is possible that mdp->top
118 is 0. In this case mmap will choose the address for us */
119 mapto = mmap(mdp->top, mapbytes, PROT_READ | PROT_WRITE,
120 MAP_PRIVATE_OR_SHARED(mdp) | MAP_IS_ANONYMOUS(mdp) |
121 MAP_FIXED, MAP_ANON_OR_FD(mdp), foffset);
123 if (mapto != (void *) -1/* That's MAP_FAILED */) {
126 mdp->base = mdp->breakval = mapto;
128 mdp->top = PAGE_ALIGN((char *) mdp->breakval + size);
129 result = (void *) mdp->breakval;
130 mdp->breakval = (char *) mdp->breakval + size;
132 THROWF(system_error,0,"mmap returned MAP_FAILED! error: %s",strerror(errno));
135 result = (void *) mdp->breakval;
136 mdp->breakval = (char *) mdp->breakval + size;
142 void *__mmalloc_remap_core(struct mdesc *mdp)
146 /* FIXME: Quick hack, needs error checking and other attention. */
148 base = mmap(mdp->base, (char *) mdp->top - (char *) mdp->base,
149 PROT_READ | PROT_WRITE | PROT_EXEC,
150 MAP_PRIVATE_OR_SHARED(mdp) | MAP_FIXED, mdp->fd, 0);
151 return ((void *) base);
154 void *mmalloc_findbase(int size)
161 flags = MAP_PRIVATE | MAP_ANONYMOUS;
165 flags = MAP_PRIVATE | MAP_FILE;
169 fd = open("/dev/zero", O_RDWR);
171 return ((void *) NULL);
174 base = mmap(0, size, PROT_READ | PROT_WRITE, flags, fd, 0);
175 if (base != (void *) -1) {
176 munmap(base, (size_t) size);
182 /* Don't allow mapping at address zero. We use that value
183 to signal an error return, and besides, it is useful to
184 catch NULL pointers if it is unmapped. Instead start
185 at the next page boundary. */
186 base = (void *) (long) getpagesize();
187 } else if (base == (void *) -1) {
190 return ((void *) base);