db_access.c

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    1 /*-
    2  * SPDX-License-Identifier: MIT-CMU
    3  *
    4  * Mach Operating System
    5  * Copyright (c) 1991,1990 Carnegie Mellon University
    6  * All Rights Reserved.
    7  *
    8  * Permission to use, copy, modify and distribute this software and its
    9  * documentation is hereby granted, provided that both the copyright
   10  * notice and this permission notice appear in all copies of the
   11  * software, derivative works or modified versions, and any portions
   12  * thereof, and that both notices appear in supporting documentation.
   13  *
   14  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
   15  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
   16  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   17  *
   18  * Carnegie Mellon requests users of this software to return to
   19  *
   20  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   21  *  School of Computer Science
   22  *  Carnegie Mellon University
   23  *  Pittsburgh PA 15213-3890
   24  *
   25  * any improvements or extensions that they make and grant Carnegie the
   26  * rights to redistribute these changes.
   27  */
   28 /*
   29  *      Author: David B. Golub, Carnegie Mellon University
   30  *      Date:   7/90
   31  */
   32 
   33 #include <sys/cdefs.h>
   34 __FBSDID("$FreeBSD$");
   35 
   36 #include <sys/param.h>
   37 #include <sys/kdb.h>
   38 #include <sys/endian.h>
   39 
   40 #include <ddb/ddb.h>
   41 #include <ddb/db_access.h>
   42 
   43 /*
   44  * Access unaligned data items on aligned (longword)
   45  * boundaries.
   46  */
   47 
   48 static unsigned db_extend[] = { /* table for sign-extending */
   49         0,
   50         0xFFFFFF80U,
   51         0xFFFF8000U,
   52         0xFF800000U
   53 };
   54 
   55 db_expr_t
   56 db_get_value(db_addr_t addr, int size, bool is_signed)
   57 {
   58         char            data[sizeof(u_int64_t)];
   59         db_expr_t       value;
   60         int             i;
   61 
   62         if (db_read_bytes(addr, size, data) != 0) {
   63                 db_printf("*** error reading from address %llx ***\n",
   64                     (long long)addr);
   65                 kdb_reenter();
   66         }
   67 
   68         value = 0;
   69 #if _BYTE_ORDER == _BIG_ENDIAN
   70         for (i = 0; i < size; i++)
   71 #else   /* _LITTLE_ENDIAN */
   72         for (i = size - 1; i >= 0; i--)
   73 #endif
   74         {
   75             value = (value << 8) + (data[i] & 0xFF);
   76         }
   77 
   78         if (size < 4) {
   79             if (is_signed && (value & db_extend[size]) != 0)
   80                 value |= db_extend[size];
   81         }
   82         return (value);
   83 }
   84 
   85 void
   86 db_put_value(db_addr_t addr, int size, db_expr_t value)
   87 {
   88         char            data[sizeof(int)];
   89         int             i;
   90 
   91 #if _BYTE_ORDER == _BIG_ENDIAN
   92         for (i = size - 1; i >= 0; i--)
   93 #else   /* _LITTLE_ENDIAN */
   94         for (i = 0; i < size; i++)
   95 #endif
   96         {
   97             data[i] = value & 0xFF;
   98             value >>= 8;
   99         }
  100 
  101         if (db_write_bytes(addr, size, data) != 0) {
  102                 db_printf("*** error writing to address %llx ***\n",
  103                     (long long)addr);
  104                 kdb_reenter();
  105         }
  106 }

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FreeBSD/Linux Kernel Cross Reference sys/ddb/db_access.c

FreeBSD/Linux Kernel Cross Reference
sys/ddb/db_access.c