sys/ddb/db_access.c

   1 /*
   2  * Mach Operating System
   3  * Copyright (c) 1991,1990 Carnegie Mellon University
   4  * All Rights Reserved.
   5  *
   6  * Permission to use, copy, modify and distribute this software and its
   7  * documentation is hereby granted, provided that both the copyright
   8  * notice and this permission notice appear in all copies of the
   9  * software, derivative works or modified versions, and any portions
  10  * thereof, and that both notices appear in supporting documentation.
  11  *
  12  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
  13  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
  14  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  15  *
  16  * Carnegie Mellon requests users of this software to return to
  17  *
  18  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  19  *  School of Computer Science
  20  *  Carnegie Mellon University
  21  *  Pittsburgh PA 15213-3890
  22  *
  23  * any improvements or extensions that they make and grant Carnegie the
  24  * rights to redistribute these changes.
  25  *
  26  * $FreeBSD: src/sys/ddb/db_access.c,v 1.15 1999/08/28 00:41:04 peter Exp $
  27  */
  28
  29 /*
  30  *      Author: David B. Golub, Carnegie Mellon University
  31  *      Date:   7/90
  32  */
  33 #include <sys/param.h>
  34 #include <machine/limits.h>
  35
  36 #include <ddb/ddb.h>
  37 #include <ddb/db_access.h>
  38
  39 /*
  40  * Access unaligned data items on aligned (longword)
  41  * boundaries.
  42  */
  43
  44 #if LONG_BIT == 32
  45
  46 static unsigned db_extend[] = { /* table for sign-extending */
  47         0,
  48         0xFFFFFF80U,
  49         0xFFFF8000U,
  50         0xFF800000U
  51 };
  52
  53 #else
  54
  55 static unsigned long db_extend[] = {    /* table for sign-extending */
  56         0,
  57         0xFFFFFFFFFFFFFF80LU,
  58         0xFFFFFFFFFFFF8000LU,
  59         0xFFFFFFFFFF800000LU,
  60         0xFFFFFFFF80000000LU,
  61         0xFFFFFF8000000000LU,
  62         0xFFFF800000000000LU,
  63         0xFF80000000000000LU
  64 };
  65
  66 #endif
  67
  68 #ifndef BYTE_MSF
  69 #define BYTE_MSF        0
  70 #endif
  71
  72 db_expr_t
  73 db_get_value(db_addr_t addr, int size, boolean_t is_signed)
  74 {
  75         char    data[sizeof(long)];
  76         int     i;
  77         db_expr_t value;
  78
  79         if (size > sizeof(long))
  80                 size = sizeof(long);
  81
  82         db_read_bytes(addr, size, data);
  83
  84         value = 0;
  85 #if     BYTE_MSF
  86         for (i = 0; i < size; i++)
  87 #else   /* BYTE_LSF */
  88         for (i = size - 1; i >= 0; i--)
  89 #endif
  90         {
  91                 value = (value << 8) + (data[i] & 0xFF);
  92         }
  93
  94         if (size < sizeof(long)) {
  95                 if (is_signed && (value & db_extend[size]) != 0)
  96                         value |= db_extend[size];
  97         }
  98         return (value);
  99 }
 100
 101 void
 102 db_put_value(db_addr_t addr, int size, db_expr_t value)
 103 {
 104         char    data[sizeof(long)];
 105         int     i;
 106
 107         if (size > sizeof(long))
 108                 size = sizeof(long);
 109
 110 #if     BYTE_MSF
 111         for (i = size - 1; i >= 0; i--)
 112 #else   /* BYTE_LSF */
 113         for (i = 0; i < size; i++)
 114 #endif
 115         {
 116                 data[i] = value & 0xFF;
 117                 value >>= 8;
 118         }
 119
 120         db_write_bytes(addr, size, data);
 121 }
 122