1 /*- 2 * Copyright (c) 2004 The FreeBSD Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include <sys/cdefs.h> 28 __FBSDID("$FreeBSD$"); 29 30 #include "opt_kdb.h" 31 32 #include <sys/param.h> 33 #include <sys/systm.h> 34 #include <sys/kdb.h> 35 #include <sys/kernel.h> 36 #include <sys/malloc.h> 37 #include <sys/pcpu.h> 38 #include <sys/proc.h> 39 #include <sys/smp.h> 40 #include <sys/sysctl.h> 41 42 #include <machine/kdb.h> 43 #include <machine/pcb.h> 44 45 #ifdef KDB_STOP_NMI 46 #include <machine/smp.h> 47 #endif 48 49 /* 50 * KDB_STOP_NMI requires SMP to pick up the right dependencies 51 * (And isn't useful on UP anyway) 52 */ 53 #if defined(KDB_STOP_NMI) && !defined(SMP) 54 #error "options KDB_STOP_NMI" requires "options SMP" 55 #endif 56 57 int kdb_active = 0; 58 void *kdb_jmpbufp = NULL; 59 struct kdb_dbbe *kdb_dbbe = NULL; 60 struct pcb kdb_pcb; 61 struct pcb *kdb_thrctx = NULL; 62 struct thread *kdb_thread = NULL; 63 struct trapframe *kdb_frame = NULL; 64 65 KDB_BACKEND(null, NULL, NULL, NULL); 66 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe); 67 68 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS); 69 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS); 70 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS); 71 72 SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes"); 73 74 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, 0, 0, 75 kdb_sysctl_available, "A", "list of available KDB backends"); 76 77 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, 0, 0, 78 kdb_sysctl_current, "A", "currently selected KDB backend"); 79 80 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, 0, 0, 81 kdb_sysctl_enter, "I", "set to enter the debugger"); 82 83 /* 84 * Flag indicating whether or not to IPI the other CPUs to stop them on 85 * entering the debugger. Sometimes, this will result in a deadlock as 86 * stop_cpus() waits for the other cpus to stop, so we allow it to be 87 * disabled. 88 */ 89 #ifdef SMP 90 static int kdb_stop_cpus = 1; 91 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW, 92 &kdb_stop_cpus, 0, ""); 93 TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus); 94 95 #ifdef KDB_STOP_NMI 96 /* 97 * Provide an alternate method of stopping other CPUs. If another CPU has 98 * disabled interrupts the conventional STOP IPI will be blocked. This 99 * NMI-based stop should get through in that case. 100 */ 101 static int kdb_stop_cpus_with_nmi = 0; 102 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus_with_nmi, CTLTYPE_INT | CTLFLAG_RW, 103 &kdb_stop_cpus_with_nmi, 0, ""); 104 TUNABLE_INT("debug.kdb.stop_cpus_with_nmi", &kdb_stop_cpus_with_nmi); 105 #endif /* KDB_STOP_NMI */ 106 107 #endif 108 109 static int 110 kdb_sysctl_available(SYSCTL_HANDLER_ARGS) 111 { 112 struct kdb_dbbe *be, **iter; 113 char *avail, *p; 114 ssize_t len, sz; 115 int error; 116 117 sz = 0; 118 SET_FOREACH(iter, kdb_dbbe_set) { 119 be = *iter; 120 if (be->dbbe_active == 0) 121 sz += strlen(be->dbbe_name) + 1; 122 } 123 sz++; 124 avail = malloc(sz, M_TEMP, M_WAITOK); 125 p = avail; 126 *p = '\0'; 127 128 SET_FOREACH(iter, kdb_dbbe_set) { 129 be = *iter; 130 if (be->dbbe_active == 0) { 131 len = snprintf(p, sz, "%s ", be->dbbe_name); 132 p += len; 133 sz -= len; 134 } 135 } 136 KASSERT(sz >= 0, ("%s", __func__)); 137 error = sysctl_handle_string(oidp, avail, 0, req); 138 free(avail, M_TEMP); 139 return (error); 140 } 141 142 static int 143 kdb_sysctl_current(SYSCTL_HANDLER_ARGS) 144 { 145 char buf[16]; 146 int error; 147 148 if (kdb_dbbe != NULL) { 149 strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf)); 150 buf[sizeof(buf) - 1] = '\0'; 151 } else 152 *buf = '\0'; 153 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 154 if (error != 0 || req->newptr == NULL) 155 return (error); 156 if (kdb_active) 157 return (EBUSY); 158 return (kdb_dbbe_select(buf)); 159 } 160 161 static int 162 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS) 163 { 164 int error, i; 165 166 error = sysctl_wire_old_buffer(req, sizeof(int)); 167 if (error == 0) { 168 i = 0; 169 error = sysctl_handle_int(oidp, &i, 0, req); 170 } 171 if (error != 0 || req->newptr == NULL) 172 return (error); 173 if (kdb_active) 174 return (EBUSY); 175 kdb_enter("sysctl debug.kdb.enter"); 176 return (0); 177 } 178 179 /* 180 * Solaris implements a new BREAK which is initiated by a character sequence 181 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the 182 * Remote Console. 183 * 184 * Note that this function may be called from almost anywhere, with interrupts 185 * disabled and with unknown locks held, so it must not access data other than 186 * its arguments. Its up to the caller to ensure that the state variable is 187 * consistent. 188 */ 189 190 #define KEY_CR 13 /* CR '\r' */ 191 #define KEY_TILDE 126 /* ~ */ 192 #define KEY_CRTLB 2 /* ^B */ 193 194 int 195 kdb_alt_break(int key, int *state) 196 { 197 int brk; 198 199 brk = 0; 200 switch (key) { 201 case KEY_CR: 202 *state = KEY_TILDE; 203 break; 204 case KEY_TILDE: 205 *state = (*state == KEY_TILDE) ? KEY_CRTLB : 0; 206 break; 207 case KEY_CRTLB: 208 if (*state == KEY_CRTLB) 209 brk = 1; 210 /* FALLTHROUGH */ 211 default: 212 *state = 0; 213 break; 214 } 215 return (brk); 216 } 217 218 /* 219 * Print a backtrace of the calling thread. The backtrace is generated by 220 * the selected debugger, provided it supports backtraces. If no debugger 221 * is selected or the current debugger does not support backtraces, this 222 * function silently returns. 223 */ 224 225 void 226 kdb_backtrace() 227 { 228 229 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) { 230 printf("KDB: stack backtrace:\n"); 231 kdb_dbbe->dbbe_trace(); 232 } 233 } 234 235 /* 236 * Set/change the current backend. 237 */ 238 239 int 240 kdb_dbbe_select(const char *name) 241 { 242 struct kdb_dbbe *be, **iter; 243 244 SET_FOREACH(iter, kdb_dbbe_set) { 245 be = *iter; 246 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) { 247 kdb_dbbe = be; 248 return (0); 249 } 250 } 251 return (EINVAL); 252 } 253 254 /* 255 * Enter the currently selected debugger. If a message has been provided, 256 * it is printed first. If the debugger does not support the enter method, 257 * it is entered by using breakpoint(), which enters the debugger through 258 * kdb_trap(). 259 */ 260 261 void 262 kdb_enter(const char *msg) 263 { 264 265 if (kdb_dbbe != NULL && kdb_active == 0) { 266 if (msg != NULL) 267 printf("KDB: enter: %s\n", msg); 268 breakpoint(); 269 } 270 } 271 272 /* 273 * Initialize the kernel debugger interface. 274 */ 275 276 void 277 kdb_init() 278 { 279 struct kdb_dbbe *be, **iter; 280 int cur_pri, pri; 281 282 kdb_active = 0; 283 kdb_dbbe = NULL; 284 cur_pri = -1; 285 SET_FOREACH(iter, kdb_dbbe_set) { 286 be = *iter; 287 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1; 288 be->dbbe_active = (pri >= 0) ? 0 : -1; 289 if (pri > cur_pri) { 290 cur_pri = pri; 291 kdb_dbbe = be; 292 } 293 } 294 if (kdb_dbbe != NULL) { 295 printf("KDB: debugger backends:"); 296 SET_FOREACH(iter, kdb_dbbe_set) { 297 be = *iter; 298 if (be->dbbe_active == 0) 299 printf(" %s", be->dbbe_name); 300 } 301 printf("\n"); 302 printf("KDB: current backend: %s\n", 303 kdb_dbbe->dbbe_name); 304 } 305 } 306 307 /* 308 * Handle contexts. 309 */ 310 311 void * 312 kdb_jmpbuf(jmp_buf new) 313 { 314 void *old; 315 316 old = kdb_jmpbufp; 317 kdb_jmpbufp = new; 318 return (old); 319 } 320 321 void 322 kdb_reenter(void) 323 { 324 325 if (!kdb_active || kdb_jmpbufp == NULL) 326 return; 327 328 longjmp(kdb_jmpbufp, 1); 329 /* NOTREACHED */ 330 } 331 332 /* 333 * Thread related support functions. 334 */ 335 336 struct pcb * 337 kdb_thr_ctx(struct thread *thr) 338 #ifdef KDB_STOP_NMI 339 { 340 u_int cpuid; 341 struct pcpu *pc; 342 343 if (thr == curthread) 344 return &kdb_pcb; 345 346 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) { 347 cpuid = pc->pc_cpuid; 348 if (pc->pc_curthread == thr && (atomic_load_acq_int(&stopped_cpus) & (1 << cpuid))) 349 return &stoppcbs[cpuid]; 350 } 351 352 return thr->td_pcb; 353 } 354 #else 355 { 356 return ((thr == curthread) ? &kdb_pcb : thr->td_pcb); 357 } 358 #endif /* KDB_STOP_NMI */ 359 360 struct thread * 361 kdb_thr_first(void) 362 { 363 struct proc *p; 364 struct thread *thr; 365 366 p = LIST_FIRST(&allproc); 367 while (p != NULL) { 368 if (p->p_sflag & PS_INMEM) { 369 thr = FIRST_THREAD_IN_PROC(p); 370 if (thr != NULL) 371 return (thr); 372 } 373 p = LIST_NEXT(p, p_list); 374 } 375 return (NULL); 376 } 377 378 struct thread * 379 kdb_thr_from_pid(pid_t pid) 380 { 381 struct proc *p; 382 383 p = LIST_FIRST(&allproc); 384 while (p != NULL) { 385 if (p->p_sflag & PS_INMEM && p->p_pid == pid) 386 return (FIRST_THREAD_IN_PROC(p)); 387 p = LIST_NEXT(p, p_list); 388 } 389 return (NULL); 390 } 391 392 struct thread * 393 kdb_thr_lookup(lwpid_t tid) 394 { 395 struct thread *thr; 396 397 thr = kdb_thr_first(); 398 while (thr != NULL && thr->td_tid != tid) 399 thr = kdb_thr_next(thr); 400 return (thr); 401 } 402 403 struct thread * 404 kdb_thr_next(struct thread *thr) 405 { 406 struct proc *p; 407 408 p = thr->td_proc; 409 thr = TAILQ_NEXT(thr, td_plist); 410 do { 411 if (thr != NULL) 412 return (thr); 413 p = LIST_NEXT(p, p_list); 414 if (p != NULL && (p->p_sflag & PS_INMEM)) 415 thr = FIRST_THREAD_IN_PROC(p); 416 } while (p != NULL); 417 return (NULL); 418 } 419 420 int 421 kdb_thr_select(struct thread *thr) 422 { 423 if (thr == NULL) 424 return (EINVAL); 425 kdb_thread = thr; 426 kdb_thrctx = kdb_thr_ctx(thr); 427 return (0); 428 } 429 430 /* 431 * Enter the debugger due to a trap. 432 */ 433 434 int 435 kdb_trap(int type, int code, struct trapframe *tf) 436 { 437 #ifdef SMP 438 int did_stop_cpus; 439 #endif 440 int handled; 441 442 if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL) 443 return (0); 444 445 /* We reenter the debugger through kdb_reenter(). */ 446 if (kdb_active) 447 return (0); 448 449 critical_enter(); 450 451 kdb_active++; 452 453 #ifdef SMP 454 if ((did_stop_cpus = kdb_stop_cpus) != 0) 455 { 456 #ifdef KDB_STOP_NMI 457 if(kdb_stop_cpus_with_nmi) 458 stop_cpus_nmi(PCPU_GET(other_cpus)); 459 else 460 #endif /* KDB_STOP_NMI */ 461 stop_cpus(PCPU_GET(other_cpus)); 462 } 463 #endif 464 465 kdb_frame = tf; 466 467 /* Let MD code do its thing first... */ 468 kdb_cpu_trap(type, code); 469 470 makectx(tf, &kdb_pcb); 471 kdb_thr_select(curthread); 472 473 handled = kdb_dbbe->dbbe_trap(type, code); 474 475 #ifdef SMP 476 if (did_stop_cpus) 477 restart_cpus(stopped_cpus); 478 #endif 479 480 kdb_active--; 481 482 critical_exit(); 483 484 return (handled); 485 } 486