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      1 /*	$NetBSD: db_memrw.c,v 1.16 2022/08/27 20:40:03 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1996, 2000 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Gordon W. Ross and Jason R. Thorpe.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 /*
     33  * Interface to the debugger for virtual memory read/write.
     34  * This file is shared by DDB and KGDB, and must work even
     35  * when only KGDB is included (thus no db_printf calls).
     36  *
     37  * To write in the text segment, we have to first make
     38  * the page writable, do the write, then restore the PTE.
     39  * For writes outside the text segment, and all reads,
     40  * just do the access -- if it causes a fault, the debugger
     41  * will recover with a longjmp to an appropriate place.
     42  *
     43  * ALERT!  If you want to access device registers with a
     44  * specific size, then the read/write functions have to
     45  * make sure to do the correct sized pointer access.
     46  *
     47  * Modified for i386 from hp300 version by
     48  * Jason R. Thorpe <thorpej (at) zembu.com>.
     49  *
     50  * Basic copy to amd64 by fvdl.
     51  *
     52  * i386 and amd64 merge by jym.
     53  */
     54 
     55 #include <sys/cdefs.h>
     56 __KERNEL_RCSID(0, "$NetBSD: db_memrw.c,v 1.16 2022/08/27 20:40:03 riastradh Exp $");
     57 
     58 #include <sys/param.h>
     59 #include <sys/proc.h>
     60 #include <sys/systm.h>
     61 
     62 #include <machine/db_machdep.h>
     63 #include <machine/pmap_private.h>
     64 
     65 #include <x86/bootspace.h>
     66 
     67 #include <ddb/db_access.h>
     68 #include <ddb/db_output.h>
     69 
     70 static int
     71 db_validate_address(vaddr_t addr)
     72 {
     73 	struct proc *p = curproc;
     74 	struct pmap *pmap;
     75 
     76 	if (!p || !p->p_vmspace || !p->p_vmspace->vm_map.pmap ||
     77 	    addr >= VM_MIN_KERNEL_ADDRESS)
     78 		pmap = pmap_kernel();
     79 	else
     80 		pmap = p->p_vmspace->vm_map.pmap;
     81 
     82 	return (pmap_extract(pmap, addr, NULL) == false);
     83 }
     84 
     85 /*
     86  * Read bytes from kernel address space for debugger.
     87  */
     88 void __noubsan
     89 db_read_bytes(vaddr_t addr, size_t size, char *data)
     90 {
     91 	char *src;
     92 
     93 	src = (char *)addr;
     94 
     95 	if (db_validate_address((vaddr_t)src)) {
     96 #ifdef DDB
     97 		db_printf("address %p is invalid\n", src);
     98 #endif
     99 		return;
    100 	}
    101 
    102 	if (size == 8) {
    103 		*((uint64_t *)data) = *((uint64_t *)src);
    104 		return;
    105 	}
    106 
    107 	if (size == 4) {
    108 		*((uint32_t *)data) = *((uint32_t *)src);
    109 		return;
    110 	}
    111 
    112 	if (size == 2) {
    113 		*((uint16_t *)data) = *((uint16_t *)src);
    114 		return;
    115 	}
    116 
    117 	while (size-- > 0) {
    118 		if (db_validate_address((vaddr_t)src)) {
    119 #ifdef DDB
    120 			db_printf("address %p is invalid\n", src);
    121 #endif
    122 			return;
    123 		}
    124 
    125 		*data++ = *src++;
    126 	}
    127 }
    128 
    129 /*
    130  * Write bytes somewhere in the kernel text.  Make the text
    131  * pages writable temporarily.
    132  */
    133 static void
    134 db_write_text(vaddr_t addr, size_t size, const char *data)
    135 {
    136 	pt_entry_t *ppte, pte;
    137 	size_t limit;
    138 	char *dst;
    139 
    140 	if (size == 0)
    141 		return;
    142 
    143 	dst = (char *)addr;
    144 
    145 	do {
    146 		addr = (vaddr_t)dst;
    147 		/*
    148 		 * Get the PTE for the page.
    149 		 */
    150 		ppte = kvtopte(addr);
    151 		pte = *ppte;
    152 
    153 		if ((pte & PTE_P) == 0) {
    154 #ifdef DDB
    155 			db_printf(" address %p not a valid page\n", dst);
    156 #endif
    157 			return;
    158 		}
    159 
    160 		/*
    161 		 * Compute number of bytes that can be written
    162 		 * with this mapping and subtract it from the
    163 		 * total size.
    164 		 */
    165 		if (pte & PTE_PS)
    166 			limit = NBPD_L2 - (addr & (NBPD_L2 - 1));
    167 		else
    168 			limit = PAGE_SIZE - (addr & PGOFSET);
    169 		if (limit > size)
    170 			limit = size;
    171 		size -= limit;
    172 
    173 		/*
    174 		 * Make the kernel text page writable.
    175 		 */
    176 		pmap_pte_setbits(ppte, PTE_W);
    177 		pmap_update_pg(addr);
    178 
    179 		/*
    180 		 * MULTIPROCESSOR: no shootdown required as the PTE continues to
    181 		 * map the same page and other CPUs do not need write access.
    182 		 */
    183 
    184 		/*
    185 		 * Page is now writable.  Do as much access as we
    186 		 * can in this page.
    187 		 */
    188 		for (; limit > 0; limit--)
    189 			*dst++ = *data++;
    190 
    191 		/*
    192 		 * Turn the page back to read-only.
    193 		 */
    194 		pmap_pte_clearbits(ppte, PTE_W);
    195 		pmap_update_pg(addr);
    196 
    197 		/*
    198 		 * MULTIPROCESSOR: no shootdown required as all other CPUs
    199 		 * should be in CPUF_PAUSE state and will not cache the PTE
    200 		 * with the write access set.
    201 		 */
    202 	} while (size != 0);
    203 }
    204 
    205 /*
    206  * Write bytes to kernel address space for debugger.
    207  */
    208 void __noubsan
    209 db_write_bytes(vaddr_t addr, size_t size, const char *data)
    210 {
    211 	extern struct bootspace bootspace;
    212 	char *dst;
    213 	size_t i;
    214 
    215 	dst = (char *)addr;
    216 
    217 	/* If any part is in kernel text or rodata, use db_write_text() */
    218 	for (i = 0; i < BTSPACE_NSEGS; i++) {
    219 		if (bootspace.segs[i].type != BTSEG_TEXT &&
    220 		    bootspace.segs[i].type != BTSEG_RODATA) {
    221 			continue;
    222 		}
    223 		if (addr >= bootspace.segs[i].va &&
    224 		    addr < (bootspace.segs[i].va + bootspace.segs[i].sz)) {
    225 			db_write_text(addr, size, data);
    226 			return;
    227 		}
    228 	}
    229 
    230 	dst = (char *)addr;
    231 
    232 	if (size == 8) {
    233 		*((uint64_t *)dst) = *((const uint64_t *)data);
    234 		return;
    235 	}
    236 
    237 	if (size == 4) {
    238 		*((uint32_t *)dst) = *((const uint32_t *)data);
    239 		return;
    240 	}
    241 
    242 	if (size == 2) {
    243 		*((uint16_t *)dst) = *((const uint16_t *)data);
    244 		return;
    245 	}
    246 
    247 	while (size-- > 0)
    248 		*dst++ = *data++;
    249 }
    250