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db_memrw.c revision 1.12 
      1 /*	$NetBSD: db_memrw.c,v 1.12 1996/06/17 15:40:48 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  * This file is shared by DDB and KGDB, and must work even
     33  * when only KGDB is included (thus no db_printf calls).
     34  *
     35  * To write in the text segment, we have to first make
     36  * the page writable, do the write, then restore the PTE.
     37  * For writes outside the text segment, and all reads,
     38  * just do the access -- if it causes a fault, the debugger
     39  * will recover with a longjmp to an appropriate place.
     40  *
     41  * ALERT!  If you want to access device registers with a
     42  * specific size, then the read/write functions have to
     43  * make sure to do the correct sized pointer access.
     44  */
     45 
     46 #include <sys/param.h>
     47 #include <sys/proc.h>
     48 
     49 #include <vm/vm.h>
     50 
     51 #include <machine/pte.h>
     52 #include <machine/db_machdep.h>
     53 
     54 #include <ddb/db_access.h>
     55 
     56 #include "cache.h"
     57 
     58 /*
     59  * Read bytes from kernel address space for debugger.
     60  * This used to check for valid PTEs, but now that
     61  * traps in DDB work correctly, "Just Do It!"
     62  */
     63 void
     64 db_read_bytes(addr, size, data)
     65 	vm_offset_t	addr;
     66 	register size_t	size;
     67 	register char	*data;
     68 {
     69 	register char	*src = (char*)addr;
     70 
     71 	if (size == 4) {
     72 		*((int*)data) = *((int*)src);
     73 		return;
     74 	}
     75 
     76 	if (size == 2) {
     77 		*((short*)data) = *((short*)src);
     78 		return;
     79 	}
     80 
     81 	while (size > 0) {
     82 		--size;
     83 		*data++ = *src++;
     84 	}
     85 }
     86 
     87 /*
     88  * Write bytes somewhere in kernel text.
     89  * Makes text page writable temporarily.
     90  */
     91 static void
     92 db_write_text(addr, size, data)
     93 	vm_offset_t	addr;
     94 	register size_t	size;
     95 	register char	*data;
     96 {
     97 	register char *dst;
     98 	int		ch, oldpte, tmppte;
     99 	vm_offset_t pgva, prevpg;
    100 
    101 	/* Prevent restoring a garbage PTE. */
    102 	if (size <= 0)
    103 		return;
    104 
    105 	dst = (char*)addr;
    106 	pgva = sun3_trunc_page((long)dst);
    107 
    108 	goto firstpage;
    109 	do {
    110 
    111 		/*
    112 		 * If we are on a new page, restore the PTE
    113 		 * for the previous page, and make the new
    114 		 * page writable.
    115 		 */
    116 		pgva = sun3_trunc_page((long)dst);
    117 		if (pgva != prevpg) {
    118 			/*
    119 			 * Restore old PTE.  No cache flush,
    120 			 * because the tmp PTE has no-cache.
    121 			 */
    122 			set_pte(prevpg, oldpte);
    123 
    124 		firstpage:
    125 			/*
    126 			 * Flush the VAC to prevent a cache hit
    127 			 * on the old, read-only PTE.
    128 			 */
    129 #ifdef	HAVECACHE
    130 			if (cache_size)
    131 				cache_flush_page(pgva);
    132 #endif
    133 			oldpte = get_pte(pgva);
    134 			if ((oldpte & PG_VALID) == 0) {
    135 				printf(" address 0x%x not a valid page\n", dst);
    136 				return;
    137 			}
    138 			tmppte = oldpte | PG_WRITE | PG_NC;
    139 			set_pte(pgva, tmppte);
    140 
    141 			prevpg = pgva;
    142 		}
    143 
    144 		/* Now we can write in this page of kernel text... */
    145 		*dst++ = *data++;
    146 
    147 	} while (--size > 0);
    148 
    149 	/* Restore old PTE for the last page touched. */
    150 	set_pte(prevpg, oldpte);
    151 
    152 	/* Finally, clear the instruction cache. */
    153 	ICIA();
    154 }
    155 
    156 /*
    157  * Write bytes to kernel address space for debugger.
    158  */
    159 extern char	kernel_text[], etext[];
    160 void
    161 db_write_bytes(addr, size, data)
    162 	vm_offset_t	addr;
    163 	register size_t	size;
    164 	register char	*data;
    165 {
    166 	register char	*dst = (char *)addr;
    167 
    168 	/* If any part is in kernel text, use db_write_text() */
    169 	if ((dst < etext) && ((dst + size) > kernel_text)) {
    170 		db_write_text(dst, size, data);
    171 		return;
    172 	}
    173 
    174 	if (size == 4) {
    175 		*((int*)dst) = *((int*)data);
    176 		return;
    177 	}
    178 
    179 	if (size == 2) {
    180 		*((short*)dst) = *((short*)data);
    181 		return;
    182 	}
    183 
    184 	while (size > 0) {
    185 		--size;
    186 		*dst++ = *data++;
    187 	}
    188 }
    189 
    190