xref: /freebsd/sys/contrib/openzfs/module/nvpair/nvpair_alloc_fixed.c (revision 29332c0dcee1e80c9fb871e06c3160bd5deb1b44)
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 #include <sys/isa_defs.h>
28 #include <sys/nvpair.h>
29 #include <sys/sysmacros.h>
30 
31 /*
32  * This allocator is very simple.
33  *  - it uses a pre-allocated buffer for memory allocations.
34  *  - it does _not_ free memory in the pre-allocated buffer.
35  *
36  * The reason for the selected implementation is simplicity.
37  * This allocator is designed for the usage in interrupt context when
38  * the caller may not wait for free memory.
39  */
40 
41 /* pre-allocated buffer for memory allocations */
42 typedef struct nvbuf {
43 	uintptr_t	nvb_buf;	/* address of pre-allocated buffer */
44 	uintptr_t 	nvb_lim;	/* limit address in the buffer */
45 	uintptr_t	nvb_cur;	/* current address in the buffer */
46 } nvbuf_t;
47 
48 /*
49  * Initialize the pre-allocated buffer allocator. The caller needs to supply
50  *
51  *   buf	address of pre-allocated buffer
52  *   bufsz	size of pre-allocated buffer
53  *
54  * nv_fixed_init() calculates the remaining members of nvbuf_t.
55  */
56 static int
57 nv_fixed_init(nv_alloc_t *nva, va_list valist)
58 {
59 	uintptr_t base = va_arg(valist, uintptr_t);
60 	uintptr_t lim = base + va_arg(valist, size_t);
61 	nvbuf_t *nvb = (nvbuf_t *)P2ROUNDUP(base, sizeof (uintptr_t));
62 
63 	if (base == 0 || (uintptr_t)&nvb[1] > lim)
64 		return (EINVAL);
65 
66 	nvb->nvb_buf = (uintptr_t)&nvb[0];
67 	nvb->nvb_cur = (uintptr_t)&nvb[1];
68 	nvb->nvb_lim = lim;
69 	nva->nva_arg = nvb;
70 
71 	return (0);
72 }
73 
74 static void *
75 nv_fixed_alloc(nv_alloc_t *nva, size_t size)
76 {
77 	nvbuf_t *nvb = nva->nva_arg;
78 	uintptr_t new = nvb->nvb_cur;
79 
80 	if (size == 0 || new + size > nvb->nvb_lim)
81 		return (NULL);
82 
83 	nvb->nvb_cur = P2ROUNDUP(new + size, sizeof (uintptr_t));
84 
85 	return ((void *)new);
86 }
87 
88 static void
89 nv_fixed_free(nv_alloc_t *nva, void *buf, size_t size)
90 {
91 	/* don't free memory in the pre-allocated buffer */
92 	(void) nva, (void) buf, (void) size;
93 }
94 
95 static void
96 nv_fixed_reset(nv_alloc_t *nva)
97 {
98 	nvbuf_t *nvb = nva->nva_arg;
99 
100 	nvb->nvb_cur = (uintptr_t)&nvb[1];
101 }
102 
103 static const nv_alloc_ops_t nv_fixed_ops_def = {
104 	.nv_ao_init = nv_fixed_init,
105 	.nv_ao_fini = NULL,
106 	.nv_ao_alloc = nv_fixed_alloc,
107 	.nv_ao_free = nv_fixed_free,
108 	.nv_ao_reset = nv_fixed_reset
109 };
110 
111 const nv_alloc_ops_t *const nv_fixed_ops = &nv_fixed_ops_def;
112 
113 #if defined(_KERNEL)
114 EXPORT_SYMBOL(nv_fixed_ops);
115 #endif
116