xref: /freebsd-src/sys/contrib/openzfs/module/nvpair/nvpair_alloc_fixed.c (revision 271171e0d97b88ba2a7c3bf750c9672b484c1c13)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or https://opensource.org/licenses/CDDL-1.0.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <sys/isa_defs.h>
#include <sys/nvpair.h>
#include <sys/sysmacros.h>

/*
 * This allocator is very simple.
 *  - it uses a pre-allocated buffer for memory allocations.
 *  - it does _not_ free memory in the pre-allocated buffer.
 *
 * The reason for the selected implementation is simplicity.
 * This allocator is designed for the usage in interrupt context when
 * the caller may not wait for free memory.
 */

/* pre-allocated buffer for memory allocations */
typedef struct nvbuf {
	uintptr_t	nvb_buf;	/* address of pre-allocated buffer */
	uintptr_t 	nvb_lim;	/* limit address in the buffer */
	uintptr_t	nvb_cur;	/* current address in the buffer */
} nvbuf_t;

/*
 * Initialize the pre-allocated buffer allocator. The caller needs to supply
 *
 *   buf	address of pre-allocated buffer
 *   bufsz	size of pre-allocated buffer
 *
 * nv_fixed_init() calculates the remaining members of nvbuf_t.
 */
static int
nv_fixed_init(nv_alloc_t *nva, va_list valist)
{
	uintptr_t base = va_arg(valist, uintptr_t);
	uintptr_t lim = base + va_arg(valist, size_t);
	nvbuf_t *nvb = (nvbuf_t *)P2ROUNDUP(base, sizeof (uintptr_t));

	if (base == 0 || (uintptr_t)&nvb[1] > lim)
		return (EINVAL);

	nvb->nvb_buf = (uintptr_t)&nvb[0];
	nvb->nvb_cur = (uintptr_t)&nvb[1];
	nvb->nvb_lim = lim;
	nva->nva_arg = nvb;

	return (0);
}

static void *
nv_fixed_alloc(nv_alloc_t *nva, size_t size)
{
	nvbuf_t *nvb = nva->nva_arg;
	uintptr_t new = nvb->nvb_cur;

	if (size == 0 || new + size > nvb->nvb_lim)
		return (NULL);

	nvb->nvb_cur = P2ROUNDUP(new + size, sizeof (uintptr_t));

	return ((void *)new);
}

static void
nv_fixed_free(nv_alloc_t *nva, void *buf, size_t size)
{
	/* don't free memory in the pre-allocated buffer */
	(void) nva, (void) buf, (void) size;
}

static void
nv_fixed_reset(nv_alloc_t *nva)
{
	nvbuf_t *nvb = nva->nva_arg;

	nvb->nvb_cur = (uintptr_t)&nvb[1];
}

static const nv_alloc_ops_t nv_fixed_ops_def = {
	.nv_ao_init = nv_fixed_init,
	.nv_ao_fini = NULL,
	.nv_ao_alloc = nv_fixed_alloc,
	.nv_ao_free = nv_fixed_free,
	.nv_ao_reset = nv_fixed_reset
};

const nv_alloc_ops_t *const nv_fixed_ops = &nv_fixed_ops_def;

#if defined(_KERNEL)
EXPORT_SYMBOL(nv_fixed_ops);
#endif