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uvm_io.c revision 1.28 
      1 /*	$NetBSD: uvm_io.c,v 1.28 2016/05/25 17:43:58 christos 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 1.28 2016/05/25 17:43:58 christos Exp $");
     36 
     37 #include <sys/param.h>
     38 #include <sys/systm.h>
     39 #include <sys/mman.h>
     40 #include <sys/uio.h>
     41 
     42 #include <uvm/uvm.h>
     43 
     44 /*
     45  * functions
     46  */
     47 
     48 /*
     49  * uvm_io: perform I/O on a map
     50  *
     51  * => caller must have a reference to "map" so that it doesn't go away
     52  *    while we are working.
     53  */
     54 
     55 int
     56 uvm_io(struct vm_map *map, struct uio *uio, int flags)
     57 {
     58 	vaddr_t baseva, endva, pageoffset, kva;
     59 	vsize_t chunksz, togo, sz;
     60 	struct vm_map_entry *dead_entries;
     61 	int error;
     62 
     63 	/*
     64 	 * step 0: sanity checks and set up for copy loop.  start with a
     65 	 * large chunk size.  if we have trouble finding vm space we will
     66 	 * reduce it.
     67 	 */
     68 
     69 	if (uio->uio_resid == 0)
     70 		return(0);
     71 	togo = uio->uio_resid;
     72 
     73 	baseva = (vaddr_t) uio->uio_offset;
     74 	endva = baseva + (togo - 1);
     75 
     76 	if (endva < baseva)   /* wrap around? */
     77 		return(EIO);
     78 
     79 	if (baseva >= VM_MAXUSER_ADDRESS)
     80 		return(0);
     81 	if (endva >= VM_MAXUSER_ADDRESS)
     82 		/* EOF truncate */
     83 		togo = togo - (endva - VM_MAXUSER_ADDRESS + 1);
     84 	pageoffset = baseva & PAGE_MASK;
     85 	baseva = trunc_page(baseva);
     86 	chunksz = MIN(round_page(togo + pageoffset), trunc_page(MAXPHYS));
     87 	error = 0;
     88 
     89 	flags |= UVM_EXTRACT_QREF | UVM_EXTRACT_CONTIG | UVM_EXTRACT_FIXPROT;
     90 	/*
     91 	 * step 1: main loop...  while we've got data to move
     92 	 */
     93 
     94 	for (/*null*/; togo > 0 ; pageoffset = 0) {
     95 
     96 		/*
     97 		 * step 2: extract mappings from the map into kernel_map
     98 		 */
     99 
    100 		error = uvm_map_extract(map, baseva, chunksz, kernel_map, &kva,
    101 		    flags);
    102 		if (error) {
    103 
    104 			/* retry with a smaller chunk... */
    105 			if (error == ENOMEM && chunksz > PAGE_SIZE) {
    106 				chunksz = trunc_page(chunksz / 2);
    107 				if (chunksz < PAGE_SIZE)
    108 					chunksz = PAGE_SIZE;
    109 				continue;
    110 			}
    111 
    112 			break;
    113 		}
    114 
    115 		/*
    116 		 * step 3: move a chunk of data
    117 		 */
    118 
    119 		sz = chunksz - pageoffset;
    120 		if (sz > togo)
    121 			sz = togo;
    122 		error = uiomove((void *) (kva + pageoffset), sz, uio);
    123 		togo -= sz;
    124 		baseva += chunksz;
    125 
    126 		/*
    127 		 * step 4: unmap the area of kernel memory
    128 		 */
    129 
    130 		vm_map_lock(kernel_map);
    131 		uvm_unmap_remove(kernel_map, kva, kva + chunksz, &dead_entries,
    132 		   0);
    133 		vm_map_unlock(kernel_map);
    134 		if (dead_entries != NULL)
    135 			uvm_unmap_detach(dead_entries, AMAP_REFALL);
    136 
    137 		if (error)
    138 			break;
    139 	}
    140 	return (error);
    141 }
    142