usr/src/common/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 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;