1 /* Initialization for access to a mmap'd malloc managed region.
2 Copyright 1992, 2000 Free Software Foundation, Inc.
4 Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com
6 This file is part of the GNU C Library.
8 The GNU C Library is free software; you can redistribute it and/or
9 modify it under the terms of the GNU Library General Public License as
10 published by the Free Software Foundation; either version 2 of the
11 License, or (at your option) any later version.
13 The GNU C Library is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 Library General Public License for more details.
18 You should have received a copy of the GNU Library General Public
19 License along with the GNU C Library; see the file COPYING.LIB. If
20 not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
21 Boston, MA 02111-1307, USA. */
23 #include <sys/types.h>
24 #include <fcntl.h> /* After sys/types.h, at least for dpx/2. */
28 #include <unistd.h> /* Prototypes for lseek */
30 #include "mmprivate.h"
37 /* Forward declarations/prototypes for local functions */
39 static struct mdesc *reuse(int fd);
41 /* Initialize access to a mmalloc managed region.
43 If FD is a valid file descriptor for an open file then data for the
44 mmalloc managed region is mapped to that file, otherwise an anonymous
45 map is used if supported by the underlying OS. In case of running in
46 an OS without support of anonymous mappings then "/dev/zero" is used
47 and in both cases the data will not exist in any filesystem object.
49 If the open file corresponding to FD is from a previous use of
50 mmalloc and passes some basic sanity checks to ensure that it is
51 compatible with the current mmalloc package, then it's data is
52 mapped in and is immediately accessible at the same addresses in
53 the current process as the process that created the file (ignoring
54 the BASEADDR parameter).
56 For non valid FDs or empty files ones the mapping is established
57 starting at the specified address BASEADDR in the process address
60 The provided BASEADDR should be choosed carefully in order to avoid
61 bumping into existing mapped regions or future mapped regions.
63 On success, returns a "malloc descriptor" which is used in subsequent
64 calls to other mmalloc package functions. It is explicitly "void *"
65 ("char *" for systems that don't fully support void) so that users
66 of the package don't have to worry about the actual implementation
69 On failure returns NULL. */
71 void *mmalloc_attach(int fd, void *baseaddr)
78 /* First check to see if FD is a valid file descriptor, and if so, see
79 if the file has any current contents (size > 0). If it does, then
80 attempt to reuse the file. If we can't reuse the file, either
81 because it isn't a valid mmalloc produced file, was produced by an
82 obsolete version, or any other reason, then we fail to attach to
86 if (fstat(fd, &sbuf) < 0)
89 else if (sbuf.st_size > 0)
90 return ((void *) reuse(fd));
93 /* If the user provided NULL BASEADDR then fail */
97 /* We start off with the malloc descriptor allocated on the stack, until
98 we build it up enough to call _mmalloc_mmap_morecore() to allocate the
99 first page of the region and copy it there. Ensure that it is zero'd and
100 then initialize the fields that we know values for. */
103 memset((char *) mdp, 0, sizeof(mtemp));
104 strncpy(mdp->magic, MMALLOC_MAGIC, MMALLOC_MAGIC_SIZE);
105 mdp->headersize = sizeof(mtemp);
106 mdp->version = MMALLOC_VERSION;
107 mdp->morecore = __mmalloc_mmap_morecore;
109 mdp->base = mdp->breakval = mdp->top = baseaddr;
111 /* If we have not been passed a valid open file descriptor for the file
112 to map to, then we go for an anonymous map */
115 mdp->flags |= MMALLOC_ANONYMOUS;
117 /* If we have not been passed a valid open file descriptor for the file
118 to map to, then open /dev/zero and use that to map to. */
120 /* Now try to map in the first page, copy the malloc descriptor structure
121 there, and arrange to return a pointer to this new copy. If the mapping
122 fails, then close the file descriptor if it was opened by us, and arrange
125 if ((mbase = mdp->morecore(mdp, sizeof(mtemp))) != NULL) {
126 memcpy(mbase, mdp, sizeof(mtemp));
130 mdp = (struct mdesc *) mbase;
132 { /* create the mutex within that heap */
133 void *old_heap = mmalloc_get_current_heap();
134 mmalloc_set_current_heap(mbase);
135 mdp->mutex = xbt_os_mutex_init();
136 mmalloc_set_current_heap(old_heap);
139 return ((void *) mbase);
142 /* Given an valid file descriptor on an open file, test to see if that file
143 is a valid mmalloc produced file, and if so, attempt to remap it into the
144 current process at the same address to which it was previously mapped.
146 Note that we have to update the file descriptor number in the malloc-
147 descriptor read from the file to match the current valid one, before
148 trying to map the file in, and again after a successful mapping and
149 after we've switched over to using the mapped in malloc descriptor
150 rather than the temporary one on the stack.
152 Once we've switched over to using the mapped in malloc descriptor, we
153 have to update the pointer to the morecore function, since it almost
154 certainly will be at a different address if the process reusing the
155 mapped region is from a different executable.
157 Also note that if the heap being remapped previously used the mmcheckf()
158 routines, we need to update the hooks since their target functions
159 will have certainly moved if the executable has changed in any way.
160 We do this by calling mmcheckf() internally.
162 Returns a pointer to the malloc descriptor if successful, or NULL if
163 unsuccessful for some reason. */
165 static struct mdesc *reuse(int fd)
168 struct mdesc *mdp = NULL;
170 if (lseek(fd, 0L, SEEK_SET) != 0)
172 if (read(fd, (char *) &mtemp, sizeof(mtemp)) != sizeof(mtemp))
174 if (mtemp.headersize != sizeof(mtemp))
176 if (strcmp(mtemp.magic, MMALLOC_MAGIC) != 0)
178 if (mtemp.version > MMALLOC_VERSION)
182 if (__mmalloc_remap_core(&mtemp) == mtemp.base) {
183 mdp = (struct mdesc *) mtemp.base;
185 mdp->morecore = __mmalloc_mmap_morecore;
186 mdp->mutex = xbt_os_mutex_init();
187 if (mdp->mfree_hook != NULL) {
188 mmcheckf((void *) mdp, (void (*)(void)) NULL, 1);
192 { /* create the mutex within that heap */
193 void *old_heap = mmalloc_get_current_heap();
194 mmalloc_set_current_heap(mdp);
195 mdp->mutex = xbt_os_mutex_init();
196 mmalloc_set_current_heap(old_heap);