The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/uvm/uvm_io.c

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    1 /*      $NetBSD: uvm_io.c,v 1.18 2003/04/23 00:55:21 tls Exp $  */
    2 
    3 /*
    4  *
    5  * Copyright (c) 1997 Charles D. Cranor and Washington University.
    6  * All rights reserved.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. All advertising materials mentioning features or use of this software
   17  *    must display the following acknowledgement:
   18  *      This product includes software developed by Charles D. Cranor and
   19  *      Washington University.
   20  * 4. The name of the author may not be used to endorse or promote products
   21  *    derived from this software without specific prior written permission.
   22  *
   23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   24  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   25  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   26  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   27  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   28  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   29  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   30  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   31  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   32  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   33  *
   34  * from: Id: uvm_io.c,v 1.1.2.2 1997/12/30 12:02:00 mrg Exp
   35  */
   36 
   37 /*
   38  * uvm_io.c: uvm i/o ops
   39  */
   40 
   41 #include <sys/cdefs.h>
   42 __KERNEL_RCSID(0, "$NetBSD: uvm_io.c,v 1.18 2003/04/23 00:55:21 tls Exp $");
   43 
   44 #include <sys/param.h>
   45 #include <sys/systm.h>
   46 #include <sys/mman.h>
   47 #include <sys/proc.h>
   48 #include <sys/malloc.h>
   49 #include <sys/uio.h>
   50 
   51 #include <uvm/uvm.h>
   52 
   53 /*
   54  * functions
   55  */
   56 
   57 /*
   58  * uvm_io: perform I/O on a map
   59  *
   60  * => caller must have a reference to "map" so that it doesn't go away
   61  *    while we are working.
   62  */
   63 
   64 int
   65 uvm_io(map, uio)
   66         struct vm_map *map;
   67         struct uio *uio;
   68 {
   69         vaddr_t baseva, endva, pageoffset, kva;
   70         vsize_t chunksz, togo, sz;
   71         struct vm_map_entry *dead_entries;
   72         int error;
   73 
   74         /*
   75          * step 0: sanity checks and set up for copy loop.  start with a
   76          * large chunk size.  if we have trouble finding vm space we will
   77          * reduce it.
   78          */
   79 
   80         if (uio->uio_resid == 0)
   81                 return(0);
   82         togo = uio->uio_resid;
   83 
   84         baseva = (vaddr_t) uio->uio_offset;
   85         endva = baseva + (togo - 1);
   86 
   87         if (endva < baseva)   /* wrap around? */
   88                 return(EIO);
   89 
   90         if (baseva >= VM_MAXUSER_ADDRESS)
   91                 return(0);
   92         if (endva >= VM_MAXUSER_ADDRESS)
   93                 /* EOF truncate */
   94                 togo = togo - (endva - VM_MAXUSER_ADDRESS + 1);
   95         pageoffset = baseva & PAGE_MASK;
   96         baseva = trunc_page(baseva);
   97         chunksz = MIN(round_page(togo + pageoffset), trunc_page(MAXPHYS));
   98         error = 0;
   99 
  100         /*
  101          * step 1: main loop...  while we've got data to move
  102          */
  103 
  104         for (/*null*/; togo > 0 ; pageoffset = 0) {
  105 
  106                 /*
  107                  * step 2: extract mappings from the map into kernel_map
  108                  */
  109 
  110                 error = uvm_map_extract(map, baseva, chunksz, kernel_map, &kva,
  111                             UVM_EXTRACT_QREF | UVM_EXTRACT_CONTIG |
  112                             UVM_EXTRACT_FIXPROT);
  113                 if (error) {
  114 
  115                         /* retry with a smaller chunk... */
  116                         if (error == ENOMEM && chunksz > PAGE_SIZE) {
  117                                 chunksz = trunc_page(chunksz / 2);
  118                                 if (chunksz < PAGE_SIZE)
  119                                         chunksz = PAGE_SIZE;
  120                                 continue;
  121                         }
  122 
  123                         break;
  124                 }
  125 
  126                 /*
  127                  * step 3: move a chunk of data
  128                  */
  129 
  130                 sz = chunksz - pageoffset;
  131                 if (sz > togo)
  132                         sz = togo;
  133                 error = uiomove((caddr_t) (kva + pageoffset), sz, uio);
  134                 if (error)
  135                         break;
  136                 togo -= sz;
  137                 baseva += chunksz;
  138 
  139 
  140                 /*
  141                  * step 4: unmap the area of kernel memory
  142                  */
  143 
  144                 vm_map_lock(kernel_map);
  145                 uvm_unmap_remove(kernel_map, kva, kva + chunksz, &dead_entries);
  146                 vm_map_unlock(kernel_map);
  147                 if (dead_entries != NULL)
  148                         uvm_unmap_detach(dead_entries, AMAP_REFALL);
  149         }
  150         return (error);
  151 }

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