module/nvpair/nvpair_alloc_fixed.c

   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 https://opensource.org/licenses/CDDL-1.0.
  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