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 */
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;
32 #define PAGE_ALIGN(addr) (void*) (((long)(addr) + pagesize - 1) & \
35 /* Return MAP_PRIVATE if MDP represents /dev/zero. Otherwise, return
37 #define MAP_PRIVATE_OR_SHARED(MDP) (( MDP -> flags & MMALLOC_ANONYMOUS) \
41 /* Return MAP_ANONYMOUS if MDP uses anonymous mapping. Otherwise, return 0 */
42 #define MAP_IS_ANONYMOUS(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
46 /* Return -1 if MDP uses anonymous mapping. Otherwise, return MDP->FD */
47 #define MAP_ANON_OR_FD(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
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(). */
55 void *mmorecore(struct mdesc *mdp, int size)
59 off_t foffset; /* File offset at which new mapping will start */
60 size_t mapbytes; /* Number of bytes to map */
61 void *moveto; /* Address where we wish to move "break value" to */
62 void *mapto; /* Address we actually mapped to */
63 char buf = 0; /* Single byte to write to extend mapped file */
66 pagesize = getpagesize();
69 /* Just return the current "break" value. */
70 result = mdp->breakval;
72 } else if (size < 0) {
73 /* We are deallocating memory. If the amount requested would cause
74 us to try to deallocate back past the base of the mmap'd region
75 then do nothing, and return NULL. Otherwise, deallocate the
76 memory and return the old break value. */
77 if (((char *) mdp->breakval) + size >= (char *) mdp->base) {
78 result = (void *) mdp->breakval;
79 mdp->breakval = (char *) mdp->breakval + size;
80 moveto = PAGE_ALIGN(mdp->breakval);
82 (size_t) (((char *) mdp->top) - ((char *) moveto)) - 1);
86 /* We are allocating memory. Make sure we have an open file
87 descriptor if not working with anonymous memory. */
88 if (!(mdp->flags & MMALLOC_ANONYMOUS) && mdp->fd < 0) {
89 THROWF(system_error,0,"mmap file descriptor <0 (%d), without MMALLOC_ANONYMOUS being in the flags",mdp->fd);
91 } else if ((char *) mdp->breakval + size > (char *) mdp->top) {
92 /* The request would move us past the end of the currently
93 mapped memory, so map in enough more memory to satisfy
94 the request. This means we also have to grow the mapped-to
95 file by an appropriate amount, since mmap cannot be used
97 moveto = PAGE_ALIGN((char *) mdp->breakval + size);
98 mapbytes = (char *) moveto - (char *) mdp->top;
99 foffset = (char *) mdp->top - (char *) mdp->base;
102 /* FIXME: Test results of lseek() */
103 lseek(mdp->fd, foffset + mapbytes - 1, SEEK_SET);
104 test = write(mdp->fd, &buf, 1);
106 THROWF(system_error, 0, "write to mmap'ed fd failed! error: %s", strerror(errno));
109 /* Let's call mmap. Note that it is possible that mdp->top
110 is 0. In this case mmap will choose the address for us */
111 mapto = mmap(mdp->top, mapbytes, PROT_READ | PROT_WRITE,
112 MAP_PRIVATE_OR_SHARED(mdp) | MAP_IS_ANONYMOUS(mdp) |
113 MAP_FIXED, MAP_ANON_OR_FD(mdp), foffset);
115 if (mapto == (void *) -1/* That's MAP_FAILED */)
116 THROWF(system_error,0,"mmap returned MAP_FAILED! error: %s",strerror(errno));
119 mdp->base = mdp->breakval = mapto;
121 mdp->top = PAGE_ALIGN((char *) mdp->breakval + size);
122 result = (void *) mdp->breakval;
123 mdp->breakval = (char *) mdp->breakval + size;
125 result = (void *) mdp->breakval;
126 mdp->breakval = (char *) mdp->breakval + size;
132 void *__mmalloc_remap_core(xbt_mheap_t mdp)
134 /* FIXME: Quick hack, needs error checking and other attention. */
136 return mmap(mdp->base, (char*) mdp->top - (char*) mdp->base,
137 PROT_READ | PROT_WRITE | PROT_EXEC,
138 MAP_PRIVATE_OR_SHARED(mdp) | MAP_FIXED, mdp->fd, 0);