xref: /illumos-gate/usr/src/common/nvpair/nvpair_alloc_fixed.c (revision bea83d026ee1bd1b2a2419e1d0232f107a5d7d9b)
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/stropts.h>
30 #include <sys/isa_defs.h>
31 #include <sys/nvpair.h>
32 #include <sys/sysmacros.h>
33 #if defined(_KERNEL) && !defined(_BOOT)
34 #include <sys/varargs.h>
35 #else
36 #include <stdarg.h>
37 #include <strings.h>
38 #endif
39 
40 /*
41  * This allocator is very simple.
42  *  - it uses a pre-allocated buffer for memory allocations.
43  *  - it does _not_ free memory in the pre-allocated buffer.
44  *
45  * The reason for the selected implemention is simplicity.
46  * This allocator is designed for the usage in interrupt context when
47  * the caller may not wait for free memory.
48  */
49 
50 /* pre-allocated buffer for memory allocations */
51 typedef struct nvbuf {
52 	uintptr_t	nvb_buf;	/* address of pre-allocated buffer */
53 	uintptr_t 	nvb_lim;	/* limit address in the buffer */
54 	uintptr_t	nvb_cur;	/* current address in the buffer */
55 } nvbuf_t;
56 
57 /*
58  * Initialize the pre-allocated buffer allocator. The caller needs to supply
59  *
60  *   buf	address of pre-allocated buffer
61  *   bufsz	size of pre-allocated buffer
62  *
63  * nv_fixed_init() calculates the remaining members of nvbuf_t.
64  */
65 static int
66 nv_fixed_init(nv_alloc_t *nva, va_list valist)
67 {
68 	uintptr_t base = va_arg(valist, uintptr_t);
69 	uintptr_t lim = base + va_arg(valist, size_t);
70 	nvbuf_t *nvb = (nvbuf_t *)P2ROUNDUP(base, sizeof (uintptr_t));
71 
72 	if (base == 0 || (uintptr_t)&nvb[1] > lim)
73 		return (EINVAL);
74 
75 	nvb->nvb_buf = (uintptr_t)&nvb[0];
76 	nvb->nvb_cur = (uintptr_t)&nvb[1];
77 	nvb->nvb_lim = lim;
78 	nva->nva_arg = nvb;
79 
80 	return (0);
81 }
82 
83 static void *
84 nv_fixed_alloc(nv_alloc_t *nva, size_t size)
85 {
86 	nvbuf_t *nvb = nva->nva_arg;
87 	uintptr_t new = nvb->nvb_cur;
88 
89 	if (size == 0 || new + size > nvb->nvb_lim)
90 		return (NULL);
91 
92 	nvb->nvb_cur = P2ROUNDUP(new + size, sizeof (uintptr_t));
93 
94 	return ((void *)new);
95 }
96 
97 /*ARGSUSED*/
98 static void
99 nv_fixed_free(nv_alloc_t *nva, void *buf, size_t size)
100 {
101 	/* don't free memory in the pre-allocated buffer */
102 }
103 
104 static void
105 nv_fixed_reset(nv_alloc_t *nva)
106 {
107 	nvbuf_t *nvb = nva->nva_arg;
108 
109 	nvb->nvb_cur = (uintptr_t)&nvb[1];
110 }
111 
112 const nv_alloc_ops_t nv_fixed_ops_def = {
113 	nv_fixed_init,	/* nv_ao_init() */
114 	NULL,		/* nv_ao_fini() */
115 	nv_fixed_alloc,	/* nv_ao_alloc() */
116 	nv_fixed_free,	/* nv_ao_free() */
117 	nv_fixed_reset	/* nv_ao_reset() */
118 };
119 
120 const nv_alloc_ops_t *nv_fixed_ops = &nv_fixed_ops_def;
121