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

     /*      $NetBSD: uvm_io.c,v 1.29 2020/09/21 18:41:59 chs Exp $  */
     
     /*
      * Copyright (c) 1997 Charles D. Cranor and Washington University.
      * All rights reserved.
      *
      * 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.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
     *
     * from: Id: uvm_io.c,v 1.1.2.2 1997/12/30 12:02:00 mrg Exp
     */
    
    /*
     * uvm_io.c: uvm i/o ops
     */
    
    #include <sys/cdefs.h>
    __KERNEL_RCSID(0, "$NetBSD: uvm_io.c,v 1.29 2020/09/21 18:41:59 chs Exp $");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/mman.h>
    #include <sys/uio.h>
    
    #include <uvm/uvm.h>
    
    /*
     * functions
     */
    
    /*
     * uvm_io: perform I/O on a map
     *
     * => caller must have a reference to "map" so that it doesn't go away
     *    while we are working.
     */
    
    int
    uvm_io(struct vm_map *map, struct uio *uio, int flags)
    {
            vaddr_t baseva, endva, pageoffset, kva;
            vsize_t chunksz, togo, sz;
            struct vm_map_entry *dead_entries;
            int error;
    
            /*
             * step 0: sanity checks and set up for copy loop.  start with a
             * large chunk size.  if we have trouble finding vm space we will
             * reduce it.
             */
    
            if (uio->uio_resid == 0)
                    return(0);
            togo = uio->uio_resid;
    
            baseva = (vaddr_t) uio->uio_offset;
            endva = baseva + (togo - 1);
    
            if (endva < baseva)   /* wrap around? */
                    return(EIO);
    
            if (baseva >= VM_MAXUSER_ADDRESS)
                    return(0);
            if (endva >= VM_MAXUSER_ADDRESS)
                    /* EOF truncate */
                    togo = togo - (endva - VM_MAXUSER_ADDRESS + 1);
            pageoffset = baseva & PAGE_MASK;
            baseva = trunc_page(baseva);
            chunksz = MIN(round_page(togo + pageoffset), trunc_page(MAXPHYS));
            error = 0;
    
            flags |= UVM_EXTRACT_QREF | UVM_EXTRACT_CONTIG | UVM_EXTRACT_FIXPROT;
    
            /* XXX cannot use QREF with without AMAP_REFALL, and REFALL is unsafe */
            flags &= ~UVM_EXTRACT_QREF;
    
            /*
             * step 1: main loop...  while we've got data to move
             */
    
            for (/*null*/; togo > 0 ; pageoffset = 0) {
    
                   /*
                    * step 2: extract mappings from the map into kernel_map
                    */
   
                   error = uvm_map_extract(map, baseva, chunksz, kernel_map, &kva,
                       flags);
                   if (error) {
   
                           /* retry with a smaller chunk... */
                           if (error == ENOMEM && chunksz > PAGE_SIZE) {
                                   chunksz = trunc_page(chunksz / 2);
                                   if (chunksz < PAGE_SIZE)
                                           chunksz = PAGE_SIZE;
                                   continue;
                           }
   
                           break;
                   }
   
                   /*
                    * step 3: move a chunk of data
                    */
   
                   sz = chunksz - pageoffset;
                   if (sz > togo)
                           sz = togo;
                   error = uiomove((void *) (kva + pageoffset), sz, uio);
                   togo -= sz;
                   baseva += chunksz;
   
                   /*
                    * step 4: unmap the area of kernel memory
                    */
   
                   vm_map_lock(kernel_map);
                   uvm_unmap_remove(kernel_map, kva, kva + chunksz, &dead_entries,
                      0);
                   vm_map_unlock(kernel_map);
                   if (dead_entries != NULL)
                           uvm_unmap_detach(dead_entries, AMAP_REFALL);
   
                   if (error)
                           break;
           }
           return (error);
   }

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