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db_memrw.c revision 1.10 
      1 /*	$NetBSD: db_memrw.c,v 1.10 1996/02/16 23:32:00 gwr Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1996 Gordon W. Ross
      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  * 3. The name of the author may not be used to endorse or promote products
     16  *    derived from this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     28  */
     29 
     30 /*
     31  * Interface to the debugger for virtual memory read/write.
     32  *
     33  * To write in the text segment, we have to first make
     34  * the page writable, do the write, then restore the PTE.
     35  * For writes outside the text segment, and all reads,
     36  * just do the access -- if it causes a fault, the debugger
     37  * will recover with a longjmp to an appropriate place.
     38  *
     39  * ALERT!  If you want to access device registers with a
     40  * specific size, then the read/write functions have to
     41  * make sure to do the correct sized pointer access.
     42  */
     43 
     44 #include <sys/param.h>
     45 #include <sys/proc.h>
     46 
     47 #include <vm/vm.h>
     48 
     49 #include <machine/pte.h>
     50 #include <machine/db_machdep.h>
     51 
     52 #include <ddb/db_access.h>
     53 
     54 #include "cache.h"
     55 
     56 /*
     57  * Read bytes from kernel address space for debugger.
     58  * This used to check for valid PTEs, but now that
     59  * traps in DDB work correctly, "Just Do It!"
     60  */
     61 void
     62 db_read_bytes(addr, size, data)
     63 	vm_offset_t	addr;
     64 	register size_t	size;
     65 	register char	*data;
     66 {
     67 	register char	*src = (char*)addr;
     68 
     69 	if (size == 4) {
     70 		*((int*)data) = *((int*)src);
     71 		return;
     72 	}
     73 
     74 	if (size == 2) {
     75 		*((short*)data) = *((short*)src);
     76 		return;
     77 	}
     78 
     79 	while (--size >= 0)
     80 		*data++ = *src++;
     81 }
     82 
     83 /*
     84  * Write bytes somewhere in kernel text.
     85  * Makes text page writable temporarily.
     86  */
     87 static void
     88 db_write_text(addr, size, data)
     89 	vm_offset_t	addr;
     90 	register size_t	size;
     91 	register char	*data;
     92 {
     93 	register char *dst;
     94 	int		ch, oldpte, tmppte;
     95 	vm_offset_t pgva, prevpg;
     96 
     97 	/* Prevent restoring a garbage PTE. */
     98 	if (size <= 0)
     99 		return;
    100 
    101 	dst = (char*)addr;
    102 	pgva = sun3_trunc_page((long)dst);
    103 
    104 	goto firstpage;
    105 	do {
    106 
    107 		/*
    108 		 * If we are on a new page, restore the PTE
    109 		 * for the previous page, and make the new
    110 		 * page writable.
    111 		 */
    112 		pgva = sun3_trunc_page((long)dst);
    113 		if (pgva != prevpg) {
    114 			/*
    115 			 * Restore old PTE.  No cache flush,
    116 			 * because the tmp PTE has no-cache.
    117 			 */
    118 			set_pte(prevpg, oldpte);
    119 
    120 		firstpage:
    121 			/*
    122 			 * Flush the VAC to prevent a cache hit
    123 			 * on the old, read-only PTE.
    124 			 */
    125 #ifdef	HAVECACHE
    126 			if (cache_size)
    127 				cache_flush_page(pgva);
    128 #endif
    129 			oldpte = get_pte(pgva);
    130 			if ((oldpte & PG_VALID) == 0) {
    131 				db_printf(" address 0x%x not a valid page\n", dst);
    132 				return;
    133 			}
    134 			tmppte = oldpte | PG_WRITE | PG_NC;
    135 			set_pte(pgva, tmppte);
    136 
    137 			prevpg = pgva;
    138 		}
    139 
    140 		/* Now we can write in this page of kernel text... */
    141 		*dst++ = *data++;
    142 
    143 	} while (--size > 0);
    144 
    145 	/* Restore old PTE for the last page touched. */
    146 	set_pte(prevpg, oldpte);
    147 
    148 	/* Finally, clear the instruction cache. */
    149 	ICIA();
    150 }
    151 
    152 /*
    153  * Write bytes to kernel address space for debugger.
    154  */
    155 extern char	kernel_text[], etext[];
    156 void
    157 db_write_bytes(addr, size, data)
    158 	vm_offset_t	addr;
    159 	register size_t	size;
    160 	register char	*data;
    161 {
    162 	register char	*dst = (char *)addr;
    163 
    164 	/* If any part is in kernel text, use db_write_text() */
    165 	if ((dst < etext) && ((dst + size) > kernel_text)) {
    166 		db_write_text(dst, size, data);
    167 		return;
    168 	}
    169 
    170 	if (size == 4) {
    171 		*((int*)dst) = *((int*)data);
    172 		return;
    173 	}
    174 
    175 	if (size == 2) {
    176 		*((short*)dst) = *((short*)data);
    177 		return;
    178 	}
    179 
    180 	while (--size >= 0)
    181 		*dst++ = *data++;
    182 }
    183 
    184