222 lines
7.1 KiB
C
222 lines
7.1 KiB
C
/* Initialization for access to a mmap'd malloc managed region.
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Copyright 1992, 2000 Free Software Foundation, Inc.
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Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include <sys/types.h>
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#include <fcntl.h> /* After sys/types.h, at least for dpx/2. */
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#include <sys/stat.h>
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#include <string.h>
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#ifdef HAVE_UNISTD_H
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#include <unistd.h> /* Prototypes for lseek */
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#endif
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#include "mmprivate.h"
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#ifndef SEEK_SET
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#define SEEK_SET 0
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#endif
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#if defined(HAVE_MMAP)
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/* Forward declarations/prototypes for local functions */
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static struct mdesc *reuse PARAMS ((int));
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/* Initialize access to a mmalloc managed region.
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If FD is a valid file descriptor for an open file then data for the
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mmalloc managed region is mapped to that file, otherwise "/dev/zero"
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is used and the data will not exist in any filesystem object.
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If the open file corresponding to FD is from a previous use of
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mmalloc and passes some basic sanity checks to ensure that it is
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compatible with the current mmalloc package, then it's data is
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mapped in and is immediately accessible at the same addresses in
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the current process as the process that created the file.
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If BASEADDR is not NULL, the mapping is established starting at the
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specified address in the process address space. If BASEADDR is NULL,
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the mmalloc package chooses a suitable address at which to start the
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mapped region, which will be the value of the previous mapping if
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opening an existing file which was previously built by mmalloc, or
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for new files will be a value chosen by mmap.
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Specifying BASEADDR provides more control over where the regions
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start and how big they can be before bumping into existing mapped
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regions or future mapped regions.
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On success, returns a "malloc descriptor" which is used in subsequent
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calls to other mmalloc package functions. It is explicitly "void *"
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("char *" for systems that don't fully support void) so that users
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of the package don't have to worry about the actual implementation
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details.
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On failure returns NULL. */
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PTR
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mmalloc_attach (fd, baseaddr)
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int fd;
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PTR baseaddr;
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{
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struct mdesc mtemp;
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struct mdesc *mdp;
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PTR mbase;
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struct stat sbuf;
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/* First check to see if FD is a valid file descriptor, and if so, see
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if the file has any current contents (size > 0). If it does, then
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attempt to reuse the file. If we can't reuse the file, either
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because it isn't a valid mmalloc produced file, was produced by an
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obsolete version, or any other reason, then we fail to attach to
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this file. */
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if (fd >= 0)
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{
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if (fstat (fd, &sbuf) < 0)
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{
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return (NULL);
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}
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else if (sbuf.st_size > 0)
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{
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return ((PTR) reuse (fd));
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}
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}
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/* We start off with the malloc descriptor allocated on the stack, until
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we build it up enough to call _mmalloc_mmap_morecore() to allocate the
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first page of the region and copy it there. Ensure that it is zero'd and
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then initialize the fields that we know values for. */
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mdp = &mtemp;
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memset ((char *) mdp, 0, sizeof (mtemp));
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strncpy (mdp -> magic, MMALLOC_MAGIC, MMALLOC_MAGIC_SIZE);
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mdp -> headersize = sizeof (mtemp);
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mdp -> version = MMALLOC_VERSION;
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mdp -> morecore = __mmalloc_mmap_morecore;
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mdp -> fd = fd;
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mdp -> base = mdp -> breakval = mdp -> top = baseaddr;
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/* If we have not been passed a valid open file descriptor for the file
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to map to, then open /dev/zero and use that to map to. */
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if (mdp -> fd < 0)
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{
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if ((mdp -> fd = open ("/dev/zero", O_RDWR)) < 0)
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{
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return (NULL);
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}
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else
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{
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mdp -> flags |= MMALLOC_DEVZERO;
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}
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}
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/* Now try to map in the first page, copy the malloc descriptor structure
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there, and arrange to return a pointer to this new copy. If the mapping
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fails, then close the file descriptor if it was opened by us, and arrange
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to return a NULL. */
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if ((mbase = mdp -> morecore (mdp, sizeof (mtemp))) != NULL)
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{
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memcpy (mbase, mdp, sizeof (mtemp));
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mdp = (struct mdesc *) mbase;
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}
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else
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{
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if (mdp -> flags & MMALLOC_DEVZERO)
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{
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close (mdp -> fd);
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}
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mdp = NULL;
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}
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return ((PTR) mdp);
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}
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/* Given an valid file descriptor on an open file, test to see if that file
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is a valid mmalloc produced file, and if so, attempt to remap it into the
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current process at the same address to which it was previously mapped.
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Note that we have to update the file descriptor number in the malloc-
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descriptor read from the file to match the current valid one, before
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trying to map the file in, and again after a successful mapping and
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after we've switched over to using the mapped in malloc descriptor
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rather than the temporary one on the stack.
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Once we've switched over to using the mapped in malloc descriptor, we
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have to update the pointer to the morecore function, since it almost
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certainly will be at a different address if the process reusing the
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mapped region is from a different executable.
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Also note that if the heap being remapped previously used the mmcheckf()
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routines, we need to update the hooks since their target functions
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will have certainly moved if the executable has changed in any way.
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We do this by calling mmcheckf() internally.
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Returns a pointer to the malloc descriptor if successful, or NULL if
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unsuccessful for some reason. */
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static struct mdesc *
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reuse (fd)
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int fd;
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{
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struct mdesc mtemp;
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struct mdesc *mdp = NULL;
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if ((lseek (fd, 0L, SEEK_SET) == 0) &&
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(read (fd, (char *) &mtemp, sizeof (mtemp)) == sizeof (mtemp)) &&
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(mtemp.headersize == sizeof (mtemp)) &&
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(strcmp (mtemp.magic, MMALLOC_MAGIC) == 0) &&
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(mtemp.version <= MMALLOC_VERSION))
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{
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mtemp.fd = fd;
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if (__mmalloc_remap_core (&mtemp) == mtemp.base)
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{
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mdp = (struct mdesc *) mtemp.base;
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mdp -> fd = fd;
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mdp -> morecore = __mmalloc_mmap_morecore;
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if (mdp -> mfree_hook != NULL)
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{
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mmcheckf ((PTR) mdp, (void (*) PARAMS ((void))) NULL, 1);
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}
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}
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}
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return (mdp);
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}
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#else /* !defined (HAVE_MMAP) */
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/* For systems without mmap, the library still supplies an entry point
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to link to, but trying to initialize access to an mmap'd managed region
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always fails. */
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/* ARGSUSED */
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PTR
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mmalloc_attach (fd, baseaddr)
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int fd;
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PTR baseaddr;
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{
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return (NULL);
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}
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#endif /* defined (HAVE_MMAP) */
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