1 /* $NetBSD: kern_crashme.c,v 1.4 2021/09/07 11:00:13 riastradh Exp $ */ 2 3 /* 4 * Copyright (c) 2018, 2019 Matthew R. Green 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, 23 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 25 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 26 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31 /* 32 * kern_crashme.c: special debugging routines, designed for debugging 33 * kernel crashes. 34 * 35 * supports crashme sysctl nodes, to test various ways the system can 36 * panic or crash. you can add and remove nodes. 37 */ 38 39 #ifdef _KERNEL_OPT 40 #include "opt_ddb.h" 41 #endif 42 43 #include <sys/param.h> 44 #include <sys/sysctl.h> 45 #include <sys/systm.h> 46 #include <sys/kthread.h> 47 #include <sys/kmem.h> 48 #include <sys/mutex.h> 49 #include <sys/crashme.h> 50 51 #ifdef DDB 52 #include <ddb/ddb.h> 53 #endif 54 55 #define DPRINTF(fmt, ...) \ 56 printf("%s:%d: " fmt "\n", __func__, __LINE__, ## __VA_ARGS__) 57 58 static int crashme_sysctl_forwarder(SYSCTLFN_PROTO); 59 60 static int crashme_panic(int); 61 static int crashme_null_deref(int); 62 #ifdef DDB 63 static int crashme_ddb(int); 64 #endif 65 66 #define CMNODE(name, lname, func) \ 67 { \ 68 .cn_name = name, \ 69 .cn_longname = lname, \ 70 .cn_fn = func, \ 71 } 72 73 static crashme_node nodes[] = { 74 CMNODE("panic", "plain old panic", crashme_panic), 75 CMNODE("null_deref", "null dereference", crashme_null_deref), 76 #ifdef DDB 77 CMNODE("ddb", "enter ddb directly", crashme_ddb), 78 #endif 79 }; 80 static crashme_node *first_node; 81 static kmutex_t crashme_lock; 82 static const struct sysctlnode *crashme_root = NULL; 83 static bool crashme_enable = 0; 84 85 /* 86 * add a crashme node dynamically. return -1 on failure, 0 on success. 87 */ 88 int 89 crashme_add(crashme_node *ncn) 90 { 91 int rv = -1; 92 crashme_node *cn; 93 crashme_node *last = NULL; 94 95 if (crashme_root == NULL) 96 return -1; 97 98 mutex_enter(&crashme_lock); 99 for (cn = first_node; cn; last = cn, cn = cn->cn_next) { 100 if (strcmp(cn->cn_name, ncn->cn_name) == 0) 101 break; 102 } 103 if (!cn) { 104 ncn->cn_next = NULL; 105 106 rv = sysctl_createv(NULL, 0, 107 &crashme_root, &ncn->cn_sysctl, 108 CTLFLAG_PERMANENT | CTLFLAG_READWRITE, 109 CTLTYPE_INT, ncn->cn_name, 110 SYSCTL_DESCR(ncn->cn_longname), 111 crashme_sysctl_forwarder, 0, 112 NULL, 0, 113 CTL_CREATE, CTL_EOL); 114 115 /* don't insert upon failure */ 116 if (rv == 0) { 117 if (last) 118 last->cn_next = ncn; 119 if (first_node == NULL) 120 first_node = ncn; 121 } 122 } 123 mutex_exit(&crashme_lock); 124 125 return rv; 126 } 127 128 /* 129 * remove a crashme node. return -1 on failure, 0 on success. 130 */ 131 int 132 crashme_remove(crashme_node *rcn) 133 { 134 crashme_node *cn, *prev = NULL; 135 136 mutex_enter(&crashme_lock); 137 for (cn = first_node; cn; prev = cn, cn = cn->cn_next) { 138 int rv; 139 140 if (cn != rcn) 141 continue; 142 143 if (cn == first_node) 144 first_node = cn->cn_next; 145 if (prev) 146 prev->cn_next = cn->cn_next; 147 148 if ((rv = sysctl_destroyv(NULL, CTL_DEBUG, crashme_root, 149 cn->cn_name, CTL_EOL)) == 0) 150 printf("%s: unable to remove %s from sysctl\n", 151 __func__, cn->cn_name); 152 break; 153 } 154 mutex_exit(&crashme_lock); 155 156 if (cn == NULL) 157 return -1; 158 159 return 0; 160 } 161 162 /* 163 * list or execute a crashme node 164 */ 165 static int 166 crashme_sysctl_forwarder(SYSCTLFN_ARGS) 167 { 168 struct sysctlnode node; 169 crashme_node *cn; 170 int error, arg = 0; 171 172 for (cn = first_node; cn; cn = cn->cn_next) { 173 if (cn->cn_sysctl == rnode) 174 break; 175 } 176 if (!cn) { 177 return EINVAL; 178 } 179 180 node = *rnode; 181 node.sysctl_data = &arg; 182 error = sysctl_lookup(SYSCTLFN_CALL(&node)); 183 if (error || newp == NULL) 184 return (error); 185 186 if (!crashme_enable) 187 return EACCES; 188 189 DPRINTF("invoking \"%s\" (%s)", cn->cn_name, cn->cn_longname); 190 if ((*cn->cn_fn)(arg) != 0) 191 panic("crashme on %s failed!\n", cn->cn_name); 192 return 0; 193 } 194 195 /* 196 * register the various nodes with sysctl. 197 */ 198 SYSCTL_SETUP(selfdebug_crashme, "sysctl crashme setup") 199 { 200 int rv; 201 size_t n; 202 203 mutex_init(&crashme_lock, MUTEX_DEFAULT, IPL_NONE); 204 205 rv = sysctl_createv(NULL, 0, NULL, &crashme_root, 206 CTLFLAG_PERMANENT, 207 CTLTYPE_NODE, "crashme", 208 SYSCTL_DESCR("Crashme options"), 209 NULL, 0, NULL, 0, 210 CTL_DEBUG, CTL_CREATE, CTL_EOL); 211 212 if (rv != 0 || crashme_root == NULL) 213 return; 214 215 rv = sysctl_createv(NULL, 0, NULL, NULL, 216 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 217 CTLTYPE_BOOL, "crashme_enable", 218 SYSCTL_DESCR("Enable crashme"), 219 NULL, 0, &crashme_enable, 0, 220 CTL_DEBUG, CTL_CREATE, CTL_EOL); 221 222 for (n = 0; n < __arraycount(nodes); n++) { 223 crashme_node *cn = &nodes[n]; 224 225 rv = crashme_add(cn); 226 227 /* don't insert */ 228 if (rv != 0) 229 continue; 230 } 231 } 232 233 /* 234 * actual panic functions below 235 */ 236 static int 237 crashme_panic(int flags) 238 { 239 240 panic("crashme plain old panic"); 241 return -1; 242 } 243 244 static int 245 crashme_null_deref(int flags) 246 { 247 248 *(volatile char *)0 = 0; 249 return -1; 250 } 251 252 #ifdef DDB 253 static int 254 crashme_ddb(int flags) 255 { 256 257 Debugger(); 258 return 0; 259 } 260 #endif 261