1 /* Support for an sbrk-like function that uses mmap. */
3 /* Copyright (c) 2010-2014. The SimGrid Team.
4 * All rights reserved. */
6 /* This program is free software; you can redistribute it and/or modify it
7 * under the terms of the license (GNU LGPL) which comes with this package. */
9 /* Copyright 1992, 2000 Free Software Foundation, Inc.
11 Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com */
13 #include "src/internal_config.h"
15 #include <unistd.h> /* Prototypes for lseek */
23 #include "mmprivate.h"
26 #define MAP_ANONYMOUS MAP_ANON
29 #define PAGE_ALIGN(addr) (void*) (((long)(addr) + xbt_pagesize - 1) & \
30 ~((long)xbt_pagesize - 1))
32 /* Return MAP_PRIVATE if MDP represents /dev/zero. Otherwise, return
34 #define MAP_PRIVATE_OR_SHARED(MDP) (( MDP -> flags & MMALLOC_ANONYMOUS) \
38 /* Return MAP_ANONYMOUS if MDP uses anonymous mapping. Otherwise, return 0 */
39 #define MAP_IS_ANONYMOUS(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
43 /* Return -1 if MDP uses anonymous mapping. Otherwise, return MDP->FD */
44 #define MAP_ANON_OR_FD(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
48 /* Return 0if MDP uses anonymous mapping. Otherwise, return off */
49 #define MAP_ANON_OR_OFFSET(MDP, off) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
53 /** @brief Add memoty to this heap
55 * Get core for the memory region specified by MDP, using SIZE as the
56 * amount to either add to or subtract from the existing region. Works
57 * like sbrk(), but using mmap().
59 * It never returns NULL. Instead, it dies verbosely on errors.
62 * @param size Bytes to allocate for this heap (or <0 to free memory from this heap)
64 void *mmorecore(struct mdesc *mdp, ssize_t size)
67 void* result; // please keep it uninitialized to track issues
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 /* Just return the current "break" value. */
80 /* We are deallocating memory. If the amount requested would cause us to try to deallocate back past the base of
81 * the mmap'd region then die verbosely. Otherwise, deallocate the memory and return the old break value. */
82 if (((char*)mdp->breakval) + size >= (char*)mdp->base) {
83 result = (void*)mdp->breakval;
84 mdp->breakval = (char*)mdp->breakval + size;
85 moveto = PAGE_ALIGN(mdp->breakval);
86 munmap(moveto, (size_t)(((char*)mdp->top) - ((char*)moveto)) - 1);
89 fprintf(stderr,"Internal error: mmap was asked to deallocate more memory than it previously allocated. Bailling out now!\n");
93 /* We are allocating memory. Make sure we have an open file descriptor if not working with anonymous memory. */
94 if (!(mdp->flags & MMALLOC_ANONYMOUS) && mdp->fd < 0) {
95 fprintf(stderr,"Internal error: mmap file descriptor <0 (%d), without MMALLOC_ANONYMOUS being in the flags.\n",mdp->fd);
97 } else if ((char*)mdp->breakval + size > (char*)mdp->top) {
98 /* The request would move us past the end of the currently mapped memory, so map in enough more memory to satisfy
99 the request. This means we also have to grow the mapped-to file by an appropriate amount, since mmap cannot
100 be used to extend a file. */
101 moveto = PAGE_ALIGN((char*)mdp->breakval + size);
102 mapbytes = (char*)moveto - (char*)mdp->top;
103 foffset = (char*)mdp->top - (char*)mdp->base;
106 /* FIXME: Test results of lseek() */
107 lseek(mdp->fd, foffset + mapbytes - 1, SEEK_SET);
108 test = write(mdp->fd, &buf, 1);
110 fprintf(stderr,"Internal error: write to mmap'ed fd failed! error: %s", strerror(errno));
115 /* Let's call mmap. Note that it is possible that mdp->top is 0. In this case mmap will choose the address for us.
116 This call might very well overwrite an already existing memory mapping (leading to weird bugs).
118 mapto = mmap(mdp->top, mapbytes, PROT_READ | PROT_WRITE,
119 MAP_PRIVATE_OR_SHARED(mdp) | MAP_IS_ANONYMOUS(mdp) |
120 MAP_FIXED, MAP_ANON_OR_FD(mdp), MAP_ANON_OR_OFFSET(mdp, foffset));
122 if (mapto == MAP_FAILED) {
124 fprintf(stderr,"Internal error: mmap returned MAP_FAILED! error: %s\n",strerror(errno));
125 snprintf(buff,1024,"cat /proc/%d/maps",getpid());
126 int status = system(buff);
127 if (status == -1 || !(WIFEXITED(status) && WEXITSTATUS(status) == 0))
128 fprintf(stderr, "Something went wrong when trying to %s\n", buff);
134 mdp->base = mdp->breakval = mapto;
136 mdp->top = PAGE_ALIGN((char*)mdp->breakval + size);
137 result = (void *) mdp->breakval;
138 mdp->breakval = (char*)mdp->breakval + size;
140 /* Memory is already mapped, we only need to increase the breakval: */
141 result = (void *) mdp->breakval;
142 mdp->breakval = (char*)mdp->breakval + size;
148 void *__mmalloc_remap_core(xbt_mheap_t mdp)
150 /* FIXME: Quick hack, needs error checking and other attention. */
152 return mmap(mdp->base, (char*) mdp->top - (char*) mdp->base,
153 PROT_READ | PROT_WRITE | PROT_EXEC,
154 MAP_PRIVATE_OR_SHARED(mdp) | MAP_FIXED, mdp->fd, 0);