opensolaris_nvpair_alloc_fixed.c revision 292973 
1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22/*
23 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
24 * Use is subject to license terms.
25 */
26
27#pragma ident	"%Z%%M%	%I%	%E% SMI"
28
29#include <sys/nvpair.h>
30#include <sys/sysmacros.h>
31#if defined(_KERNEL) && !defined(_BOOT)
32#include <sys/varargs.h>
33#else
34#include <stdarg.h>
35#include <strings.h>
36#endif
37
38/*
39 * This allocator is very simple.
40 *  - it uses a pre-allocated buffer for memory allocations.
41 *  - it does _not_ free memory in the pre-allocated buffer.
42 *
43 * The reason for the selected implemention is simplicity.
44 * This allocator is designed for the usage in interrupt context when
45 * the caller may not wait for free memory.
46 */
47
48/* pre-allocated buffer for memory allocations */
49typedef struct nvbuf {
50	uintptr_t	nvb_buf;	/* address of pre-allocated buffer */
51	uintptr_t 	nvb_lim;	/* limit address in the buffer */
52	uintptr_t	nvb_cur;	/* current address in the buffer */
53} nvbuf_t;
54
55/*
56 * Initialize the pre-allocated buffer allocator. The caller needs to supply
57 *
58 *   buf	address of pre-allocated buffer
59 *   bufsz	size of pre-allocated buffer
60 *
61 * nv_fixed_init() calculates the remaining members of nvbuf_t.
62 */
63static int
64nv_fixed_init(nv_alloc_t *nva, va_list valist)
65{
66	uintptr_t base = va_arg(valist, uintptr_t);
67	uintptr_t lim = base + va_arg(valist, size_t);
68	nvbuf_t *nvb = (nvbuf_t *)P2ROUNDUP(base, sizeof (uintptr_t));
69
70	if (base == 0 || (uintptr_t)&nvb[1] > lim)
71		return (EINVAL);
72
73	nvb->nvb_buf = (uintptr_t)&nvb[0];
74	nvb->nvb_cur = (uintptr_t)&nvb[1];
75	nvb->nvb_lim = lim;
76	nva->nva_arg = nvb;
77
78	return (0);
79}
80
81static void *
82nv_fixed_alloc(nv_alloc_t *nva, size_t size)
83{
84	nvbuf_t *nvb = nva->nva_arg;
85	uintptr_t new = nvb->nvb_cur;
86
87	if (size == 0 || new + size > nvb->nvb_lim)
88		return (NULL);
89
90	nvb->nvb_cur = P2ROUNDUP(new + size, sizeof (uintptr_t));
91
92	return ((void *)new);
93}
94
95/*ARGSUSED*/
96static void
97nv_fixed_free(nv_alloc_t *nva, void *buf, size_t size)
98{
99	/* don't free memory in the pre-allocated buffer */
100}
101
102static void
103nv_fixed_reset(nv_alloc_t *nva)
104{
105	nvbuf_t *nvb = nva->nva_arg;
106
107	nvb->nvb_cur = (uintptr_t)&nvb[1];
108}
109
110const nv_alloc_ops_t nv_fixed_ops_def = {
111	nv_fixed_init,	/* nv_ao_init() */
112	NULL,		/* nv_ao_fini() */
113	nv_fixed_alloc,	/* nv_ao_alloc() */
114	nv_fixed_free,	/* nv_ao_free() */
115	nv_fixed_reset	/* nv_ao_reset() */
116};
117
118const nv_alloc_ops_t *nv_fixed_ops = &nv_fixed_ops_def;
119