usr/klibc/sbrk.c

/* sbrk.c - Change data segment size */

/* Written 2000 by Werner Almesberger */
/* Modified 2003-2004 for klibc by H. Peter Anvin */

#include <stddef.h>
#include <unistd.h>
#include <inttypes.h>
#include <errno.h>
#include "malloc.h"

#if !_KLIBC_NO_MMU		/* uClinux doesn't have brk() */

char *__current_brk;		/* Common with brk.c */

/* p is an address,  a is alignment; must be a power of 2 */
static inline void *align_up(void *p, uintptr_t a)
{
	return (void *)(((uintptr_t) p + a - 1) & ~(a - 1));
}

void *sbrk(ptrdiff_t increment)
{
	char *start, *end, *new_brk;

	if (!__current_brk)
		__current_brk = __brk(NULL);

	start = align_up(__current_brk, _KLIBC_SBRK_ALIGNMENT);
	end = start + increment;

	new_brk = __brk(end);

	if (new_brk == (void *)-1)
		return (void *)-1;
	else if (new_brk < end) {
		errno = ENOMEM;
		return (void *)-1;
	}

	__current_brk = new_brk;
	return start;
}

#endif				/* !_KLIBC_NO_MMU */