From 7f12eb53ca94589c030b562c362b6283f1b002e4 Mon Sep 17 00:00:00 2001 From: Fred Fish Date: Thu, 11 Jul 1996 07:36:27 +0000 Subject: * detach.c (mmalloc_detach): Fix bug in computation of negative brk value. * mmcheck.c (mmcheckf): Renamed from mmcheck and new FORCE argument added. Replaced hack that always allowed checking routines to be installed and enforce restriction that they have to be installed prior to allocating any memory on the used heap or the FORCE argument has to be non-NULL. (mmcheck): New function that calls mmcheckf with FORCE set to zero, for backwards compatibility. * mmalloc.c (malloc): Store result in local variable before returning it. Makes debugging much easier at negligible cost. * mmalloc.h (mmcheckf): Declare. * attach.c (reuse): Call mmcheckf rather than mmcheck. * mmap-sup.c (__mmalloc_mmap_morecore): Improve to allow mmap to select a base mapping address if none is otherwise given. (mmalloc_findbase): New function that user can call to find an available mapping address of a given size. --- mmalloc/mmap-sup.c | 190 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 190 insertions(+) create mode 100644 mmalloc/mmap-sup.c (limited to 'mmalloc/mmap-sup.c') diff --git a/mmalloc/mmap-sup.c b/mmalloc/mmap-sup.c new file mode 100644 index 0000000..e085f95 --- /dev/null +++ b/mmalloc/mmap-sup.c @@ -0,0 +1,190 @@ +/* Support for an sbrk-like function that uses mmap. + 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. */ + +#if defined(HAVE_MMAP) + +#include +#include +#include + +#ifndef SEEK_SET +#define SEEK_SET 0 +#endif + +#include "mmprivate.h" + +/* Cache the pagesize for the current host machine. Note that if the host + does not readily provide a getpagesize() function, we need to emulate it + elsewhere, not clutter up this file with lots of kluges to try to figure + it out. */ + +static size_t pagesize; +extern int getpagesize PARAMS ((void)); + +#define PAGE_ALIGN(addr) (caddr_t) (((long)(addr) + pagesize - 1) & \ + ~(pagesize - 1)) + +/* Get core for the memory region specified by MDP, using SIZE as the + amount to either add to or subtract from the existing region. Works + like sbrk(), but using mmap(). */ + +PTR +__mmalloc_mmap_morecore (mdp, size) + struct mdesc *mdp; + int size; +{ + PTR result = NULL; + off_t foffset; /* File offset at which new mapping will start */ + size_t mapbytes; /* Number of bytes to map */ + caddr_t moveto; /* Address where we wish to move "break value" to */ + caddr_t mapto; /* Address we actually mapped to */ + char buf = 0; /* Single byte to write to extend mapped file */ + + if (pagesize == 0) + { + pagesize = getpagesize (); + } + if (size == 0) + { + /* Just return the current "break" value. */ + result = mdp -> breakval; + } + else if (size < 0) + { + /* We are deallocating memory. If the amount requested would cause + us to try to deallocate back past the base of the mmap'd region + then do nothing, and return NULL. Otherwise, deallocate the + memory and return the old break value. */ + if (mdp -> breakval + size >= mdp -> base) + { + result = (PTR) mdp -> breakval; + mdp -> breakval += size; + moveto = PAGE_ALIGN (mdp -> breakval); + munmap (moveto, (size_t) (mdp -> top - moveto)); + mdp -> top = moveto; + } + } + else + { + /* We are allocating memory. Make sure we have an open file + descriptor and then go on to get the memory. */ + if (mdp -> fd < 0) + { + result = NULL; + } + else if (mdp -> breakval + size > mdp -> top) + { + /* The request would move us past the end of the currently + mapped memory, so map in enough more memory to satisfy + the request. This means we also have to grow the mapped-to + file by an appropriate amount, since mmap cannot be used + to extend a file. */ + moveto = PAGE_ALIGN (mdp -> breakval + size); + mapbytes = moveto - mdp -> top; + foffset = mdp -> top - mdp -> base; + /* FIXME: Test results of lseek() and write() */ + lseek (mdp -> fd, foffset + mapbytes - 1, SEEK_SET); + write (mdp -> fd, &buf, 1); + if (mdp -> base == 0) + { + /* Let mmap pick the map start address */ + mapto = mmap (0, mapbytes, PROT_READ | PROT_WRITE, + MAP_SHARED, mdp -> fd, foffset); + if (mapto != (caddr_t) -1) + { + mdp -> base = mdp -> breakval = mapto; + mdp -> top = mdp -> base + mapbytes; + result = (PTR) mdp -> breakval; + mdp -> breakval += size; + } + } + else + { + mapto = mmap (mdp -> top, mapbytes, PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_FIXED, mdp -> fd, foffset); + if (mapto == mdp -> top) + { + mdp -> top = moveto; + result = (PTR) mdp -> breakval; + mdp -> breakval += size; + } + } + } + else + { + result = (PTR) mdp -> breakval; + mdp -> breakval += size; + } + } + return (result); +} + +PTR +__mmalloc_remap_core (mdp) + struct mdesc *mdp; +{ + caddr_t base; + + /* FIXME: Quick hack, needs error checking and other attention. */ + + base = mmap (mdp -> base, mdp -> top - mdp -> base, + PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, + mdp -> fd, 0); + return ((PTR) base); +} + +PTR +mmalloc_findbase (size) + int size; +{ + int fd; + caddr_t base = NULL; + + fd = open ("/dev/zero", O_RDWR); + if (fd != -1) + { + base = mmap (0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + if (base != (caddr_t) -1) + { + munmap (base, (size_t) size); + } + close (fd); + if (base == 0) + { + /* Don't allow mapping at address zero. We use that value + to signal an error return, and besides, it is useful to + catch NULL pointers if it is unmapped. Instead start + at the next page boundary. */ + base = (caddr_t) getpagesize (); + } + else if (base == (caddr_t) -1) + { + base = NULL; + } + } + return ((PTR) base); +} + +#else /* defined(HAVE_MMAP) */ +/* Prevent "empty translation unit" warnings from the idiots at X3J11. */ +static char ansi_c_idiots = 69; +#endif /* defined(HAVE_MMAP) */ -- cgit v1.1