diff options
Diffstat (limited to 'mmalloc/attach.c')
| -rw-r--r-- | mmalloc/attach.c | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/mmalloc/attach.c b/mmalloc/attach.c new file mode 100644 index 0000000..70cfa6e --- /dev/null +++ b/mmalloc/attach.c @@ -0,0 +1,218 @@ +/* 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) */ + |