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"
38 /* Forward declarations/prototypes for local functions */
40 static struct mdesc *reuse(int fd);
42 /* Initialize access to a mmalloc managed region.
44 If FD is a valid file descriptor for an open file then data for the
45 mmalloc managed region is mapped to that file, otherwise an anonymous
46 map is used if supported by the underlying OS. In case of running in
47 an OS without support of anonymous mappings then "/dev/zero" is used
48 and in both cases the data will not exist in any filesystem object.
50 If the open file corresponding to FD is from a previous use of
51 mmalloc and passes some basic sanity checks to ensure that it is
52 compatible with the current mmalloc package, then it's data is
53 mapped in and is immediately accessible at the same addresses in
54 the current process as the process that created the file (ignoring
55 the BASEADDR parameter).
57 For non valid FDs or empty files ones the mapping is established
58 starting at the specified address BASEADDR in the process address
61 The provided BASEADDR should be choosed carefully in order to avoid
62 bumping into existing mapped regions or future mapped regions.
64 On success, returns a "malloc descriptor" which is used in subsequent
65 calls to other mmalloc package functions. It is explicitly "void *"
66 ("char *" for systems that don't fully support void) so that users
67 of the package don't have to worry about the actual implementation
70 On failure returns NULL. */
72 void *mmalloc_attach(int fd, void *baseaddr)
79 /* First check to see if FD is a valid file descriptor, and if so, see
80 if the file has any current contents (size > 0). If it does, then
81 attempt to reuse the file. If we can't reuse the file, either
82 because it isn't a valid mmalloc produced file, was produced by an
83 obsolete version, or any other reason, then we fail to attach to
87 if (fstat(fd, &sbuf) < 0)
90 else if (sbuf.st_size > 0)
91 return ((void *) reuse(fd));
94 /* If the user provided NULL BASEADDR then fail */
98 /* We start off with the malloc descriptor allocated on the stack, until
99 we build it up enough to call _mmalloc_mmap_morecore() to allocate the
100 first page of the region and copy it there. Ensure that it is zero'd and
101 then initialize the fields that we know values for. */
104 memset((char *) mdp, 0, sizeof(mtemp));
105 strncpy(mdp->magic, MMALLOC_MAGIC, MMALLOC_MAGIC_SIZE);
106 mdp->headersize = sizeof(mtemp);
107 mdp->version = MMALLOC_VERSION;
108 mdp->morecore = __mmalloc_mmap_morecore;
110 mdp->base = mdp->breakval = mdp->top = baseaddr;
111 mdp->next_mdesc = NULL;
114 /* If we have not been passed a valid open file descriptor for the file
115 to map to, then we go for an anonymous map */
118 mdp->flags |= MMALLOC_ANONYMOUS;
119 sem_init(&mdp->sem, 0, 1);
121 sem_init(&mdp->sem, 1, 1);
124 /* If we have not been passed a valid open file descriptor for the file
125 to map to, then open /dev/zero and use that to map to. */
127 /* Now try to map in the first page, copy the malloc descriptor structure
128 there, and arrange to return a pointer to this new copy. If the mapping
129 fails, then close the file descriptor if it was opened by us, and arrange
132 if ((mbase = mdp->morecore(mdp, sizeof(mtemp))) != NULL) {
133 memcpy(mbase, mdp, sizeof(mtemp));
135 THROWF(system_error,0,"morecore failed to get some memory!");
138 /* Add the new heap to the linked list of heaps attached by mmalloc */
139 if(__mmalloc_default_mdp){
140 mdp = __mmalloc_default_mdp;
141 while(mdp->next_mdesc)
142 mdp = mdp->next_mdesc;
145 mdp->next_mdesc = (struct mdesc *)mbase;
149 return ((void *) mbase);
152 /* Given an valid file descriptor on an open file, test to see if that file
153 is a valid mmalloc produced file, and if so, attempt to remap it into the
154 current process at the same address to which it was previously mapped.
156 Note that we have to update the file descriptor number in the malloc-
157 descriptor read from the file to match the current valid one, before
158 trying to map the file in, and again after a successful mapping and
159 after we've switched over to using the mapped in malloc descriptor
160 rather than the temporary one on the stack.
162 Once we've switched over to using the mapped in malloc descriptor, we
163 have to update the pointer to the morecore function, since it almost
164 certainly will be at a different address if the process reusing the
165 mapped region is from a different executable.
167 Also note that if the heap being remapped previously used the mmcheckf()
168 routines, we need to update the hooks since their target functions
169 will have certainly moved if the executable has changed in any way.
170 We do this by calling mmcheckf() internally.
172 Returns a pointer to the malloc descriptor if successful, or NULL if
173 unsuccessful for some reason. */
175 static struct mdesc *reuse(int fd)
178 struct mdesc *mdp = NULL, *mdptemp = NULL;
180 if (lseek(fd, 0L, SEEK_SET) != 0)
182 if (read(fd, (char *) &mtemp, sizeof(mtemp)) != sizeof(mtemp))
184 if (mtemp.headersize != sizeof(mtemp))
186 if (strcmp(mtemp.magic, MMALLOC_MAGIC) != 0)
188 if (mtemp.version > MMALLOC_VERSION)
192 if (__mmalloc_remap_core(&mtemp) == mtemp.base) {
193 mdp = (struct mdesc *) mtemp.base;
195 mdp->morecore = __mmalloc_mmap_morecore;
197 sem_init(&mdp->sem, 1, 1);
200 if (mdp->mfree_hook != NULL) {
201 mmcheckf((void *) mdp, (void (*)(void)) NULL, 1);
205 /* Add the new heap to the linked list of heaps attached by mmalloc */
206 mdptemp = __mmalloc_default_mdp;
207 while(mdptemp->next_mdesc)
208 mdptemp = mdptemp->next_mdesc;
211 mdptemp->next_mdesc = mdp;