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) 2010-2014. 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 #define PAGE_ALIGN(addr) (void*) (((long)(addr) + xbt_pagesize - 1) & \
26 ~((long)xbt_pagesize - 1))
28 /* Return MAP_PRIVATE if MDP represents /dev/zero. Otherwise, return
30 #define MAP_PRIVATE_OR_SHARED(MDP) (( MDP -> flags & MMALLOC_ANONYMOUS) \
34 /* Return MAP_ANONYMOUS if MDP uses anonymous mapping. Otherwise, return 0 */
35 #define MAP_IS_ANONYMOUS(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
39 /* Return -1 if MDP uses anonymous mapping. Otherwise, return MDP->FD */
40 #define MAP_ANON_OR_FD(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
44 /* Get core for the memory region specified by MDP, using SIZE as the
45 amount to either add to or subtract from the existing region. Works
46 like sbrk(), but using mmap().
48 It never returns NULL. Instead, it dies verbosely on errors. */
50 void *mmorecore(struct mdesc *mdp, ssize_t size)
53 void *result; // please keep it uninitialized to track issues
54 off_t foffset; /* File offset at which new mapping will start */
55 size_t mapbytes; /* Number of bytes to map */
56 void *moveto; /* Address where we wish to move "break value" to */
57 void *mapto; /* Address we actually mapped to */
58 char buf = 0; /* Single byte to write to extend mapped file */
60 // fprintf(stderr,"increase %p by %u\n",mdp,size);
63 /* Just return the current "break" value. */
64 result = mdp->breakval;
66 } else if (size < 0) {
67 /* We are deallocating memory. If the amount requested would cause
68 us to try to deallocate back past the base of the mmap'd region
69 then die verbosely. Otherwise, deallocate the memory and return
70 the old break value. */
71 if (((char *) mdp->breakval) + size >= (char *) mdp->base) {
72 result = (void *) mdp->breakval;
73 mdp->breakval = (char *) mdp->breakval + size;
74 moveto = PAGE_ALIGN(mdp->breakval);
76 (size_t) (((char *) mdp->top) - ((char *) moveto)) - 1);
79 fprintf(stderr,"Internal error: mmap was asked to deallocate more memory than it previously allocated. Bailling out now!\n");
83 /* We are allocating memory. Make sure we have an open file
84 descriptor if not working with anonymous memory. */
85 if (!(mdp->flags & MMALLOC_ANONYMOUS) && mdp->fd < 0) {
86 fprintf(stderr,"Internal error: mmap file descriptor <0 (%d), without MMALLOC_ANONYMOUS being in the flags.\n",mdp->fd);
88 } else if ((char *) mdp->breakval + size > (char *) mdp->top) {
89 /* The request would move us past the end of the currently
90 mapped memory, so map in enough more memory to satisfy
91 the request. This means we also have to grow the mapped-to
92 file by an appropriate amount, since mmap cannot be used
94 moveto = PAGE_ALIGN((char *) mdp->breakval + size);
95 mapbytes = (char *) moveto - (char *) mdp->top;
96 foffset = (char *) mdp->top - (char *) mdp->base;
99 /* FIXME: Test results of lseek() */
100 lseek(mdp->fd, foffset + mapbytes - 1, SEEK_SET);
101 test = write(mdp->fd, &buf, 1);
103 fprintf(stderr,"Internal error: write to mmap'ed fd failed! error: %s", strerror(errno));
108 /* Let's call mmap. Note that it is possible that mdp->top
109 is 0. In this case mmap will choose the address for us */
110 mapto = mmap(mdp->top, mapbytes, PROT_READ | PROT_WRITE,
111 MAP_PRIVATE_OR_SHARED(mdp) | MAP_IS_ANONYMOUS(mdp) |
112 MAP_FIXED, MAP_ANON_OR_FD(mdp), foffset);
114 if (mapto == (void *) -1/* That's MAP_FAILED */) {
116 fprintf(stderr,"Internal error: mmap returned MAP_FAILED! error: %s\n",strerror(errno));
117 sprintf(buff,"cat /proc/%d/maps",getpid());
118 int status = system(buff);
119 if (status == -1 || !(WIFEXITED(status) && WEXITSTATUS(status) == 0))
120 fprintf(stderr, "Something went wrong when trying to %s\n", buff);
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 result = (void *) mdp->breakval;
133 mdp->breakval = (char *) mdp->breakval + size;
139 void *__mmalloc_remap_core(xbt_mheap_t mdp)
141 /* FIXME: Quick hack, needs error checking and other attention. */
143 return mmap(mdp->base, (char*) mdp->top - (char*) mdp->base,
144 PROT_READ | PROT_WRITE | PROT_EXEC,
145 MAP_PRIVATE_OR_SHARED(mdp) | MAP_FIXED, mdp->fd, 0);