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authorStan Shebs <shebs@codesourcery.com>1999-04-16 01:35:26 +0000
committerStan Shebs <shebs@codesourcery.com>1999-04-16 01:35:26 +0000
commitc906108c21474dfb4ed285bcc0ac6fe02cd400cc (patch)
treea0015aa5cedc19ccbab307251353a41722a3ae13 /mmalloc/attach.c
parentcd946cff9ede3f30935803403f06f6ed30cad136 (diff)
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Initial creation of sourceware repositorygdb-4_18-branchpoint
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diff --git a/mmalloc/attach.c b/mmalloc/attach.c
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+/* Initialization for access to a mmap'd malloc managed region.
+ Copyright 1992 Free Software Foundation, Inc.
+
+ Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com
+
+This file is part of the GNU C Library.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C Library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB. If
+not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA. */
+
+#include <sys/types.h>
+#include <fcntl.h> /* After sys/types.h, at least for dpx/2. */
+#include <sys/stat.h>
+#include <string.h>
+#include "mmprivate.h"
+
+#ifndef SEEK_SET
+#define SEEK_SET 0
+#endif
+
+
+#if defined(HAVE_MMAP)
+
+/* Forward declarations/prototypes for local functions */
+
+static struct mdesc *reuse PARAMS ((int));
+
+/* Initialize access to a mmalloc managed region.
+
+ If FD is a valid file descriptor for an open file then data for the
+ mmalloc managed region is mapped to that file, otherwise "/dev/zero"
+ is used and the data will not exist in any filesystem object.
+
+ If the open file corresponding to FD is from a previous use of
+ mmalloc and passes some basic sanity checks to ensure that it is
+ compatible with the current mmalloc package, then it's data is
+ mapped in and is immediately accessible at the same addresses in
+ the current process as the process that created the file.
+
+ If BASEADDR is not NULL, the mapping is established starting at the
+ specified address in the process address space. If BASEADDR is NULL,
+ the mmalloc package chooses a suitable address at which to start the
+ mapped region, which will be the value of the previous mapping if
+ opening an existing file which was previously built by mmalloc, or
+ for new files will be a value chosen by mmap.
+
+ Specifying BASEADDR provides more control over where the regions
+ start and how big they can be before bumping into existing mapped
+ regions or future mapped regions.
+
+ On success, returns a "malloc descriptor" which is used in subsequent
+ calls to other mmalloc package functions. It is explicitly "void *"
+ ("char *" for systems that don't fully support void) so that users
+ of the package don't have to worry about the actual implementation
+ details.
+
+ On failure returns NULL. */
+
+PTR
+mmalloc_attach (fd, baseaddr)
+ int fd;
+ PTR baseaddr;
+{
+ struct mdesc mtemp;
+ struct mdesc *mdp;
+ PTR mbase;
+ struct stat sbuf;
+
+ /* First check to see if FD is a valid file descriptor, and if so, see
+ if the file has any current contents (size > 0). If it does, then
+ attempt to reuse the file. If we can't reuse the file, either
+ because it isn't a valid mmalloc produced file, was produced by an
+ obsolete version, or any other reason, then we fail to attach to
+ this file. */
+
+ if (fd >= 0)
+ {
+ if (fstat (fd, &sbuf) < 0)
+ {
+ return (NULL);
+ }
+ else if (sbuf.st_size > 0)
+ {
+ return ((PTR) reuse (fd));
+ }
+ }
+
+ /* We start off with the malloc descriptor allocated on the stack, until
+ we build it up enough to call _mmalloc_mmap_morecore() to allocate the
+ first page of the region and copy it there. Ensure that it is zero'd and
+ then initialize the fields that we know values for. */
+
+ mdp = &mtemp;
+ memset ((char *) mdp, 0, sizeof (mtemp));
+ strncpy (mdp -> magic, MMALLOC_MAGIC, MMALLOC_MAGIC_SIZE);
+ mdp -> headersize = sizeof (mtemp);
+ mdp -> version = MMALLOC_VERSION;
+ mdp -> morecore = __mmalloc_mmap_morecore;
+ mdp -> fd = fd;
+ mdp -> base = mdp -> breakval = mdp -> top = baseaddr;
+
+ /* If we have not been passed a valid open file descriptor for the file
+ to map to, then open /dev/zero and use that to map to. */
+
+ if (mdp -> fd < 0)
+ {
+ if ((mdp -> fd = open ("/dev/zero", O_RDWR)) < 0)
+ {
+ return (NULL);
+ }
+ else
+ {
+ mdp -> flags |= MMALLOC_DEVZERO;
+ }
+ }
+
+ /* Now try to map in the first page, copy the malloc descriptor structure
+ there, and arrange to return a pointer to this new copy. If the mapping
+ fails, then close the file descriptor if it was opened by us, and arrange
+ to return a NULL. */
+
+ if ((mbase = mdp -> morecore (mdp, sizeof (mtemp))) != NULL)
+ {
+ memcpy (mbase, mdp, sizeof (mtemp));
+ mdp = (struct mdesc *) mbase;
+ }
+ else
+ {
+ if (mdp -> flags & MMALLOC_DEVZERO)
+ {
+ close (mdp -> fd);
+ }
+ mdp = NULL;
+ }
+
+ return ((PTR) mdp);
+}
+
+/* Given an valid file descriptor on an open file, test to see if that file
+ is a valid mmalloc produced file, and if so, attempt to remap it into the
+ current process at the same address to which it was previously mapped.
+
+ Note that we have to update the file descriptor number in the malloc-
+ descriptor read from the file to match the current valid one, before
+ trying to map the file in, and again after a successful mapping and
+ after we've switched over to using the mapped in malloc descriptor
+ rather than the temporary one on the stack.
+
+ Once we've switched over to using the mapped in malloc descriptor, we
+ have to update the pointer to the morecore function, since it almost
+ certainly will be at a different address if the process reusing the
+ mapped region is from a different executable.
+
+ Also note that if the heap being remapped previously used the mmcheckf()
+ routines, we need to update the hooks since their target functions
+ will have certainly moved if the executable has changed in any way.
+ We do this by calling mmcheckf() internally.
+
+ Returns a pointer to the malloc descriptor if successful, or NULL if
+ unsuccessful for some reason. */
+
+static struct mdesc *
+reuse (fd)
+ int fd;
+{
+ struct mdesc mtemp;
+ struct mdesc *mdp = NULL;
+
+ if ((lseek (fd, 0L, SEEK_SET) == 0) &&
+ (read (fd, (char *) &mtemp, sizeof (mtemp)) == sizeof (mtemp)) &&
+ (mtemp.headersize == sizeof (mtemp)) &&
+ (strcmp (mtemp.magic, MMALLOC_MAGIC) == 0) &&
+ (mtemp.version <= MMALLOC_VERSION))
+ {
+ mtemp.fd = fd;
+ if (__mmalloc_remap_core (&mtemp) == mtemp.base)
+ {
+ mdp = (struct mdesc *) mtemp.base;
+ mdp -> fd = fd;
+ mdp -> morecore = __mmalloc_mmap_morecore;
+ if (mdp -> mfree_hook != NULL)
+ {
+ mmcheckf ((PTR) mdp, (void (*) PARAMS ((void))) NULL, 1);
+ }
+ }
+ }
+ return (mdp);
+}
+
+#else /* !defined (HAVE_MMAP) */
+
+/* For systems without mmap, the library still supplies an entry point
+ to link to, but trying to initialize access to an mmap'd managed region
+ always fails. */
+
+/* ARGSUSED */
+PTR
+mmalloc_attach (fd, baseaddr)
+ int fd;
+ PTR baseaddr;
+{
+ return (NULL);
+}
+
+#endif /* defined (HAVE_MMAP) */
+