| 1 | /* Support for sbrk() regions. |
| 2 | Copyright 1992, 2000 Free Software Foundation, Inc. |
| 3 | Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com |
| 4 | |
| 5 | This file is part of the GNU C Library. |
| 6 | |
| 7 | The GNU C Library is free software; you can redistribute it and/or |
| 8 | modify it under the terms of the GNU Library General Public License as |
| 9 | published by the Free Software Foundation; either version 2 of the |
| 10 | License, or (at your option) any later version. |
| 11 | |
| 12 | The GNU C Library is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 15 | Library General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU Library General Public |
| 18 | License along with the GNU C Library; see the file COPYING.LIB. If |
| 19 | not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, |
| 20 | Boston, MA 02111-1307, USA. */ |
| 21 | |
| 22 | #ifdef HAVE_UNISTD_H |
| 23 | #include <unistd.h> /* Prototypes for sbrk (maybe) */ |
| 24 | #endif |
| 25 | #include <string.h> /* Prototypes for memcpy, memmove, memset, etc */ |
| 26 | |
| 27 | #include "mmprivate.h" |
| 28 | |
| 29 | static PTR sbrk_morecore PARAMS ((struct mdesc *, int)); |
| 30 | #if NEED_DECLARATION_SBRK |
| 31 | extern PTR sbrk PARAMS ((int)); |
| 32 | #endif |
| 33 | |
| 34 | /* The mmalloc() package can use a single implicit malloc descriptor |
| 35 | for mmalloc/mrealloc/mfree operations which do not supply an explicit |
| 36 | descriptor. For these operations, sbrk() is used to obtain more core |
| 37 | from the system, or return core. This allows mmalloc() to provide |
| 38 | backwards compatibility with the non-mmap'd version. */ |
| 39 | |
| 40 | struct mdesc *__mmalloc_default_mdp; |
| 41 | |
| 42 | /* Use sbrk() to get more core. */ |
| 43 | |
| 44 | static PTR |
| 45 | sbrk_morecore (mdp, size) |
| 46 | struct mdesc *mdp; |
| 47 | int size; |
| 48 | { |
| 49 | PTR result; |
| 50 | |
| 51 | if ((result = sbrk (size)) == (PTR) -1) |
| 52 | { |
| 53 | result = NULL; |
| 54 | } |
| 55 | else |
| 56 | { |
| 57 | mdp -> breakval += size; |
| 58 | mdp -> top += size; |
| 59 | } |
| 60 | return (result); |
| 61 | } |
| 62 | |
| 63 | /* Initialize the default malloc descriptor if this is the first time |
| 64 | a request has been made to use the default sbrk'd region. |
| 65 | |
| 66 | Since no alignment guarantees are made about the initial value returned |
| 67 | by sbrk, test the initial value and (if necessary) sbrk enough additional |
| 68 | memory to start off with alignment to BLOCKSIZE. We actually only need |
| 69 | it aligned to an alignment suitable for any object, so this is overkill. |
| 70 | But at most it wastes just part of one BLOCKSIZE chunk of memory and |
| 71 | minimizes portability problems by avoiding us having to figure out |
| 72 | what the actual minimal alignment is. The rest of the malloc code |
| 73 | avoids this as well, by always aligning to the minimum of the requested |
| 74 | size rounded up to a power of two, or to BLOCKSIZE. |
| 75 | |
| 76 | Note that we are going to use some memory starting at this initial sbrk |
| 77 | address for the sbrk region malloc descriptor, which is a struct, so the |
| 78 | base address must be suitably aligned. */ |
| 79 | |
| 80 | struct mdesc * |
| 81 | __mmalloc_sbrk_init () |
| 82 | { |
| 83 | PTR base; |
| 84 | unsigned int adj; |
| 85 | |
| 86 | base = sbrk (0); |
| 87 | adj = RESIDUAL (base, BLOCKSIZE); |
| 88 | if (adj != 0) |
| 89 | { |
| 90 | sbrk (BLOCKSIZE - adj); |
| 91 | base = sbrk (0); |
| 92 | } |
| 93 | __mmalloc_default_mdp = (struct mdesc *) sbrk (sizeof (struct mdesc)); |
| 94 | memset ((char *) __mmalloc_default_mdp, 0, sizeof (struct mdesc)); |
| 95 | __mmalloc_default_mdp -> morecore = sbrk_morecore; |
| 96 | __mmalloc_default_mdp -> base = base; |
| 97 | __mmalloc_default_mdp -> breakval = __mmalloc_default_mdp -> top = sbrk (0); |
| 98 | __mmalloc_default_mdp -> fd = -1; |
| 99 | return (__mmalloc_default_mdp); |
| 100 | } |
| 101 | |
| 102 | |