FreeBSD/Linux Kernel Cross Reference
sys/sys/_pv_entry.h

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * Copyright (c) 2003 Peter Wemm.
      * All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
      * the Systems Programming Group of the University of Utah Computer
      * Science Department and William Jolitz of UUNET Technologies Inc.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #ifndef __SYS__PV_ENTRY_H__
    #define __SYS__PV_ENTRY_H__
    
    #include <sys/param.h>
    
    struct pmap;
    
    /*
     * For each vm_page_t, there is a list of all currently valid virtual
     * mappings of that page.  An entry is a pv_entry_t, the list is pv_list.
     */
    typedef struct pv_entry {
            vm_offset_t     pv_va;          /* virtual address for mapping */
            TAILQ_ENTRY(pv_entry)   pv_next;
    } *pv_entry_t;
    
    /*
     * pv_entries are allocated in chunks per-process.  This avoids the
     * need to track per-pmap assignments.  Each chunk is the size of a
     * single page.
     *
     * Chunks store a bitmap in pc_map[] to track which entries in the
     * bitmap are free (1) or used (0).  PC_FREEL is the value of the last
     * entry in the pc_map[] array when a chunk is completely free.  PC_FREEN
     * is the value of all the other entries in the pc_map[] array when a
     * chunk is completely free.
     */
    #if PAGE_SIZE == 4 * 1024
    #ifdef __LP64__
    #define _NPCPV  168
    #define _NPAD   0
    #else
    #define _NPCPV  336
    #define _NPAD   0
    #endif
    #elif PAGE_SIZE == 16 * 1024
    #ifdef __LP64__
    #define _NPCPV  677
    #define _NPAD   1
    #endif
    #endif
    
    #ifndef _NPCPV
    #error Unsupported page size
    #endif
    
    /* Support clang < 14 */
    #ifndef __LONG_WIDTH__
    #define __LONG_WIDTH__  (__CHAR_BIT__ * __SIZEOF_LONG__)
    #endif
    
    #define _NPCM           howmany(_NPCPV, __LONG_WIDTH__)
    #define PC_FREEN        ~0ul
    #define PC_FREEL        ((1ul << (_NPCPV % __LONG_WIDTH__)) - 1)
    
    #define PV_CHUNK_HEADER                                                 \
            struct pmap             *pc_pmap;                               \
            TAILQ_ENTRY(pv_chunk)   pc_list;                                \
            unsigned long           pc_map[_NPCM];  /* bitmap; 1 = free */  \
            TAILQ_ENTRY(pv_chunk)   pc_lru;
    
    struct pv_chunk_header {
            PV_CHUNK_HEADER
    };
   
   struct pv_chunk {
           PV_CHUNK_HEADER
           struct pv_entry         pc_pventry[_NPCPV];
           unsigned long           pc_pad[_NPAD];
   };
   
   _Static_assert(sizeof(struct pv_chunk) == PAGE_SIZE,
       "PV entry chunk size mismatch");
   
   #ifdef _KERNEL
   static __inline bool
   pc_is_full(struct pv_chunk *pc)
   {
           for (u_int i = 0; i < _NPCM; i++) {
                   if (pc->pc_map[i] != 0)
                           return (false);
           }
           return (true);
   }
   
   static __inline bool
   pc_is_free(struct pv_chunk *pc)
   {
           for (u_int i = 0; i < _NPCM - 1; i++) {
                   if (pc->pc_map[i] != PC_FREEN)
                           return (false);
           }
           return (pc->pc_map[_NPCM - 1] == PC_FREEL);
   }
   
   static __inline struct pv_chunk *
   pv_to_chunk(pv_entry_t pv)
   {
           return ((struct pv_chunk *)((uintptr_t)pv & ~(uintptr_t)PAGE_MASK));
   }
   
   #define PV_PMAP(pv) (pv_to_chunk(pv)->pc_pmap)
   #endif
   
   #endif /* !__SYS__PV_ENTRY_H__ */

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