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/* sbrk.c - sbrk implementation.
Copyright (C) 2008 Free Software Foundation, Inc.
Written by Neal H. Walfield <neal@gnu.org>.
This file is part of the GNU Hurd.
The GNU Hurd is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU Hurd 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <stdint.h>
#include <errno.h>
#include <sys/mman.h>
#include <assert.h>
#include <hurd/mutex.h>
/* We need an implementation for sbrk for glibc, which uses it before
malloc is available. In a real sbrk implementation, the initial
break value is set to the end of the data segment. We don't do
that; we just allocate a block of memory using mmap and maintain a
pointer into it. */
static ss_mutex_t lock;
static void *endds;
static void *brk;
void *
sbrk (intptr_t inc)
{
ss_mutex_lock (&lock);
if (! endds)
{
/* sbrk isn't used that much so 16MB of virtual address space
should be enough. */
#define SIZE 16 * 1024 * 1024
endds = mmap (0, SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (endds == MAP_FAILED)
{
ss_mutex_unlock (&lock);
errno = ENOMEM;
return (void *) -1;
}
brk = endds;
}
void *p = brk;
brk += inc;
assert (brk >= endds);
if (brk > endds + SIZE)
{
brk -= inc;
errno = ENOMEM;
p = (void *) -1;
debug (0, "sbrk: sbrk memory exhausted!");
}
ss_mutex_unlock (&lock);
return p;
}
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