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;
109 mdp->base = mdp->breakval = mdp->top = baseaddr;
110 mdp->next_mdesc = NULL;
113 /* If we have not been passed a valid open file descriptor for the file
114 to map to, then we go for an anonymous map */
117 mdp->flags |= MMALLOC_ANONYMOUS;
118 sem_init(&mdp->sem, 0, 1);
120 sem_init(&mdp->sem, 1, 1);
123 /* If we have not been passed a valid open file descriptor for the file
124 to map to, then open /dev/zero and use that to map to. */
126 /* Now try to map in the first page, copy the malloc descriptor structure
127 there, and arrange to return a pointer to this new copy. If the mapping
128 fails, then close the file descriptor if it was opened by us, and arrange
131 if ((mbase = mmorecore(mdp, sizeof(mtemp))) != NULL) {
132 memcpy(mbase, mdp, sizeof(mtemp));
134 THROWF(system_error,0,"morecore failed to get some memory!");
137 /* Add the new heap to the linked list of heaps attached by mmalloc */
138 if(__mmalloc_default_mdp){
139 mdp = __mmalloc_default_mdp;
140 while(mdp->next_mdesc)
141 mdp = mdp->next_mdesc;
144 mdp->next_mdesc = (struct mdesc *)mbase;
148 return ((void *) mbase);
151 /* Given an valid file descriptor on an open file, test to see if that file
152 is a valid mmalloc produced file, and if so, attempt to remap it into the
153 current process at the same address to which it was previously mapped.
155 Note that we have to update the file descriptor number in the malloc-
156 descriptor read from the file to match the current valid one, before
157 trying to map the file in, and again after a successful mapping and
158 after we've switched over to using the mapped in malloc descriptor
159 rather than the temporary one on the stack.
161 Once we've switched over to using the mapped in malloc descriptor, we
162 have to update the pointer to the morecore function, since it almost
163 certainly will be at a different address if the process reusing the
164 mapped region is from a different executable.
166 Also note that if the heap being remapped previously used the mmcheckf()
167 routines, we need to update the hooks since their target functions
168 will have certainly moved if the executable has changed in any way.
169 We do this by calling mmcheckf() internally.
171 Returns a pointer to the malloc descriptor if successful, or NULL if
172 unsuccessful for some reason. */
174 static struct mdesc *reuse(int fd)
177 struct mdesc *mdp = NULL, *mdptemp = NULL;
179 if (lseek(fd, 0L, SEEK_SET) != 0)
181 if (read(fd, (char *) &mtemp, sizeof(mtemp)) != sizeof(mtemp))
183 if (mtemp.headersize != sizeof(mtemp))
185 if (strcmp(mtemp.magic, MMALLOC_MAGIC) != 0)
187 if (mtemp.version > MMALLOC_VERSION)
191 if (__mmalloc_remap_core(&mtemp) == mtemp.base) {
192 mdp = (struct mdesc *) mtemp.base;
195 sem_init(&mdp->sem, 1, 1);
200 /* Add the new heap to the linked list of heaps attached by mmalloc */
201 mdptemp = __mmalloc_default_mdp;
202 while(mdptemp->next_mdesc)
203 mdptemp = mdptemp->next_mdesc;
206 mdptemp->next_mdesc = mdp;