99 lines
3.3 KiB
C
99 lines
3.3 KiB
C
/* Support for sbrk() regions.
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Copyright 1992 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 <string.h> /* Prototypes for memcpy, memmove, memset, etc */
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#include "mmprivate.h"
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static PTR sbrk_morecore PARAMS ((struct mdesc *, int));
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#if NEED_DECLARATION_SBRK
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extern PTR sbrk PARAMS ((int));
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#endif
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/* The mmalloc() package can use a single implicit malloc descriptor
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for mmalloc/mrealloc/mfree operations which do not supply an explicit
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descriptor. For these operations, sbrk() is used to obtain more core
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from the system, or return core. This allows mmalloc() to provide
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backwards compatibility with the non-mmap'd version. */
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struct mdesc *__mmalloc_default_mdp;
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/* Use sbrk() to get more core. */
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static PTR
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sbrk_morecore (mdp, size)
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struct mdesc *mdp;
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int size;
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{
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PTR result;
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if ((result = sbrk (size)) == (PTR) -1)
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{
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result = NULL;
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}
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else
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{
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mdp -> breakval += size;
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mdp -> top += size;
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}
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return (result);
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}
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/* Initialize the default malloc descriptor if this is the first time
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a request has been made to use the default sbrk'd region.
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Since no alignment guarantees are made about the initial value returned
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by sbrk, test the initial value and (if necessary) sbrk enough additional
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memory to start off with alignment to BLOCKSIZE. We actually only need
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it aligned to an alignment suitable for any object, so this is overkill.
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But at most it wastes just part of one BLOCKSIZE chunk of memory and
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minimizes portability problems by avoiding us having to figure out
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what the actual minimal alignment is. The rest of the malloc code
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avoids this as well, by always aligning to the minimum of the requested
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size rounded up to a power of two, or to BLOCKSIZE.
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Note that we are going to use some memory starting at this initial sbrk
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address for the sbrk region malloc descriptor, which is a struct, so the
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base address must be suitably aligned. */
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struct mdesc *
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__mmalloc_sbrk_init ()
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{
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PTR base;
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unsigned int adj;
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base = sbrk (0);
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adj = RESIDUAL (base, BLOCKSIZE);
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if (adj != 0)
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{
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sbrk (BLOCKSIZE - adj);
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base = sbrk (0);
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}
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__mmalloc_default_mdp = (struct mdesc *) sbrk (sizeof (struct mdesc));
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memset ((char *) __mmalloc_default_mdp, 0, sizeof (struct mdesc));
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__mmalloc_default_mdp -> morecore = sbrk_morecore;
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__mmalloc_default_mdp -> base = base;
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__mmalloc_default_mdp -> breakval = __mmalloc_default_mdp -> top = sbrk (0);
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__mmalloc_default_mdp -> fd = -1;
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return (__mmalloc_default_mdp);
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}
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