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uvm_io.c revision 1.24.64.1 
      1 /*	$NetBSD: uvm_io.c,v 1.24.64.1 2011/03/05 20:56:36 rmind Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1997 Charles D. Cranor and Washington University.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  *
     27  * from: Id: uvm_io.c,v 1.1.2.2 1997/12/30 12:02:00 mrg Exp
     28  */
     29 
     30 /*
     31  * uvm_io.c: uvm i/o ops
     32  */
     33 
     34 #include <sys/cdefs.h>
     35 __KERNEL_RCSID(0, "$NetBSD: uvm_io.c,v 1.24.64.1 2011/03/05 20:56:36 rmind Exp $");
     36 
     37 #include <sys/param.h>
     38 #include <sys/systm.h>
     39 #include <sys/mman.h>
     40 #include <sys/proc.h>
     41 #include <sys/malloc.h>
     42 #include <sys/uio.h>
     43 
     44 #include <uvm/uvm.h>
     45 
     46 /*
     47  * functions
     48  */
     49 
     50 /*
     51  * uvm_io: perform I/O on a map
     52  *
     53  * => caller must have a reference to "map" so that it doesn't go away
     54  *    while we are working.
     55  */
     56 
     57 int
     58 uvm_io(struct vm_map *map, struct uio *uio)
     59 {
     60 	vaddr_t baseva, endva, pageoffset, kva;
     61 	vsize_t chunksz, togo, sz;
     62 	struct vm_map_entry *dead_entries;
     63 	int error;
     64 
     65 	/*
     66 	 * step 0: sanity checks and set up for copy loop.  start with a
     67 	 * large chunk size.  if we have trouble finding vm space we will
     68 	 * reduce it.
     69 	 */
     70 
     71 	if (uio->uio_resid == 0)
     72 		return(0);
     73 	togo = uio->uio_resid;
     74 
     75 	baseva = (vaddr_t) uio->uio_offset;
     76 	endva = baseva + (togo - 1);
     77 
     78 	if (endva < baseva)   /* wrap around? */
     79 		return(EIO);
     80 
     81 	if (baseva >= VM_MAXUSER_ADDRESS)
     82 		return(0);
     83 	if (endva >= VM_MAXUSER_ADDRESS)
     84 		/* EOF truncate */
     85 		togo = togo - (endva - VM_MAXUSER_ADDRESS + 1);
     86 	pageoffset = baseva & PAGE_MASK;
     87 	baseva = trunc_page(baseva);
     88 	chunksz = MIN(round_page(togo + pageoffset), trunc_page(MAXPHYS));
     89 	error = 0;
     90 
     91 	/*
     92 	 * step 1: main loop...  while we've got data to move
     93 	 */
     94 
     95 	for (/*null*/; togo > 0 ; pageoffset = 0) {
     96 
     97 		/*
     98 		 * step 2: extract mappings from the map into kernel_map
     99 		 */
    100 
    101 		error = uvm_map_extract(map, baseva, chunksz, kernel_map, &kva,
    102 			    UVM_EXTRACT_QREF | UVM_EXTRACT_CONTIG |
    103 			    UVM_EXTRACT_FIXPROT);
    104 		if (error) {
    105 
    106 			/* retry with a smaller chunk... */
    107 			if (error == ENOMEM && chunksz > PAGE_SIZE) {
    108 				chunksz = trunc_page(chunksz / 2);
    109 				if (chunksz < PAGE_SIZE)
    110 					chunksz = PAGE_SIZE;
    111 				continue;
    112 			}
    113 
    114 			break;
    115 		}
    116 
    117 		/*
    118 		 * step 3: move a chunk of data
    119 		 */
    120 
    121 		sz = chunksz - pageoffset;
    122 		if (sz > togo)
    123 			sz = togo;
    124 		error = uiomove((void *) (kva + pageoffset), sz, uio);
    125 		togo -= sz;
    126 		baseva += chunksz;
    127 
    128 		/*
    129 		 * step 4: unmap the area of kernel memory
    130 		 */
    131 
    132 		vm_map_lock(kernel_map);
    133 		uvm_unmap_remove(kernel_map, kva, kva + chunksz, &dead_entries,
    134 		    NULL, 0);
    135 		vm_map_unlock(kernel_map);
    136 		if (dead_entries != NULL)
    137 			uvm_unmap_detach(dead_entries, AMAP_REFALL);
    138 
    139 		if (error)
    140 			break;
    141 	}
    142 	return (error);
    143 }
    144