FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/module/nvpair/nvpair_alloc_fixed.c

     /*
      * CDDL HEADER START
      *
      * The contents of this file are subject to the terms of the
      * Common Development and Distribution License (the "License").
      * You may not use this file except in compliance with the License.
      *
      * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      * or https://opensource.org/licenses/CDDL-1.0.
     * See the License for the specific language governing permissions
     * and limitations under the License.
     *
     * When distributing Covered Code, include this CDDL HEADER in each
     * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     * If applicable, add the following below this CDDL HEADER, with the
     * fields enclosed by brackets "[]" replaced with your own identifying
     * information: Portions Copyright [yyyy] [name of copyright owner]
     *
     * CDDL HEADER END
     */
    
    /*
     * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
     * Use is subject to license terms.
     */
    
    #include <sys/isa_defs.h>
    #include <sys/nvpair.h>
    #include <sys/sysmacros.h>
    
    /*
     * This allocator is very simple.
     *  - it uses a pre-allocated buffer for memory allocations.
     *  - it does _not_ free memory in the pre-allocated buffer.
     *
     * The reason for the selected implementation is simplicity.
     * This allocator is designed for the usage in interrupt context when
     * the caller may not wait for free memory.
     */
    
    /* pre-allocated buffer for memory allocations */
    typedef struct nvbuf {
            uintptr_t       nvb_buf;        /* address of pre-allocated buffer */
            uintptr_t       nvb_lim;        /* limit address in the buffer */
            uintptr_t       nvb_cur;        /* current address in the buffer */
    } nvbuf_t;
    
    /*
     * Initialize the pre-allocated buffer allocator. The caller needs to supply
     *
     *   buf        address of pre-allocated buffer
     *   bufsz      size of pre-allocated buffer
     *
     * nv_fixed_init() calculates the remaining members of nvbuf_t.
     */
    static int
    nv_fixed_init(nv_alloc_t *nva, va_list valist)
    {
            uintptr_t base = va_arg(valist, uintptr_t);
            uintptr_t lim = base + va_arg(valist, size_t);
            nvbuf_t *nvb = (nvbuf_t *)P2ROUNDUP(base, sizeof (uintptr_t));
    
            if (base == 0 || (uintptr_t)&nvb[1] > lim)
                    return (EINVAL);
    
            nvb->nvb_buf = (uintptr_t)&nvb[0];
            nvb->nvb_cur = (uintptr_t)&nvb[1];
            nvb->nvb_lim = lim;
            nva->nva_arg = nvb;
    
            return (0);
    }
    
    static void *
    nv_fixed_alloc(nv_alloc_t *nva, size_t size)
    {
            nvbuf_t *nvb = nva->nva_arg;
            uintptr_t new = nvb->nvb_cur;
    
            if (size == 0 || new + size > nvb->nvb_lim)
                    return (NULL);
    
            nvb->nvb_cur = P2ROUNDUP(new + size, sizeof (uintptr_t));
    
            return ((void *)new);
    }
    
    static void
    nv_fixed_free(nv_alloc_t *nva, void *buf, size_t size)
    {
            /* don't free memory in the pre-allocated buffer */
            (void) nva, (void) buf, (void) size;
    }
    
    static void
    nv_fixed_reset(nv_alloc_t *nva)
    {
            nvbuf_t *nvb = nva->nva_arg;
    
           nvb->nvb_cur = (uintptr_t)&nvb[1];
   }
   
   static const nv_alloc_ops_t nv_fixed_ops_def = {
           .nv_ao_init = nv_fixed_init,
           .nv_ao_fini = NULL,
           .nv_ao_alloc = nv_fixed_alloc,
           .nv_ao_free = nv_fixed_free,
           .nv_ao_reset = nv_fixed_reset
   };
   
   const nv_alloc_ops_t *const nv_fixed_ops = &nv_fixed_ops_def;
   
   #if defined(_KERNEL)
   EXPORT_SYMBOL(nv_fixed_ops);
   #endif

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