xref: /freebsd/sys/i386/i386/db_trace.c (revision 0957b409)
1 /*-
2  * Mach Operating System
3  * Copyright (c) 1991,1990 Carnegie Mellon University
4  * All Rights Reserved.
5  *
6  * Permission to use, copy, modify and distribute this software and its
7  * documentation is hereby granted, provided that both the copyright
8  * notice and this permission notice appear in all copies of the
9  * software, derivative works or modified versions, and any portions
10  * thereof, and that both notices appear in supporting documentation.
11  *
12  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
13  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
14  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
15  *
16  * Carnegie Mellon requests users of this software to return to
17  *
18  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
19  *  School of Computer Science
20  *  Carnegie Mellon University
21  *  Pittsburgh PA 15213-3890
22  *
23  * any improvements or extensions that they make and grant Carnegie the
24  * rights to redistribute these changes.
25  */
26 
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
29 
30 #include <sys/param.h>
31 #include <sys/systm.h>
32 #include <sys/kdb.h>
33 #include <sys/proc.h>
34 #include <sys/sysent.h>
35 
36 #include <machine/cpu.h>
37 #include <machine/frame.h>
38 #include <machine/md_var.h>
39 #include <machine/pcb.h>
40 #include <machine/reg.h>
41 #include <machine/stack.h>
42 
43 #include <vm/vm.h>
44 #include <vm/vm_param.h>
45 #include <vm/pmap.h>
46 
47 #include <ddb/ddb.h>
48 #include <ddb/db_access.h>
49 #include <ddb/db_sym.h>
50 #include <ddb/db_variables.h>
51 
52 static db_varfcn_t db_esp;
53 static db_varfcn_t db_frame;
54 static db_varfcn_t db_frame_seg;
55 static db_varfcn_t db_gs;
56 static db_varfcn_t db_ss;
57 
58 /*
59  * Machine register set.
60  */
61 #define	DB_OFFSET(x)	(db_expr_t *)offsetof(struct trapframe, x)
62 struct db_variable db_regs[] = {
63 	{ "cs",		DB_OFFSET(tf_cs),	db_frame_seg },
64 	{ "ds",		DB_OFFSET(tf_ds),	db_frame_seg },
65 	{ "es",		DB_OFFSET(tf_es),	db_frame_seg },
66 	{ "fs",		DB_OFFSET(tf_fs),	db_frame_seg },
67 	{ "gs",		NULL,			db_gs },
68 	{ "ss",		NULL,			db_ss },
69 	{ "eax",	DB_OFFSET(tf_eax),	db_frame },
70 	{ "ecx",	DB_OFFSET(tf_ecx),	db_frame },
71 	{ "edx",	DB_OFFSET(tf_edx),	db_frame },
72 	{ "ebx",	DB_OFFSET(tf_ebx),	db_frame },
73 	{ "esp",	NULL,			db_esp },
74 	{ "ebp",	DB_OFFSET(tf_ebp),	db_frame },
75 	{ "esi",	DB_OFFSET(tf_esi),	db_frame },
76 	{ "edi",	DB_OFFSET(tf_edi),	db_frame },
77 	{ "eip",	DB_OFFSET(tf_eip),	db_frame },
78 	{ "efl",	DB_OFFSET(tf_eflags),	db_frame },
79 };
80 struct db_variable *db_eregs = db_regs + nitems(db_regs);
81 
82 static __inline int
83 get_esp(struct trapframe *tf)
84 {
85 	return (TF_HAS_STACKREGS(tf) ? tf->tf_esp : (intptr_t)&tf->tf_esp);
86 }
87 
88 static int
89 db_frame(struct db_variable *vp, db_expr_t *valuep, int op)
90 {
91 	int *reg;
92 
93 	if (kdb_frame == NULL)
94 		return (0);
95 
96 	reg = (int *)((uintptr_t)kdb_frame + (db_expr_t)vp->valuep);
97 	if (op == DB_VAR_GET)
98 		*valuep = *reg;
99 	else
100 		*reg = *valuep;
101 	return (1);
102 }
103 
104 static int
105 db_frame_seg(struct db_variable *vp, db_expr_t *valuep, int op)
106 {
107 	struct trapframe_vm86 *tfp;
108 	int off;
109 	uint16_t *reg;
110 
111 	if (kdb_frame == NULL)
112 		return (0);
113 
114 	off = (intptr_t)vp->valuep;
115 	if (kdb_frame->tf_eflags & PSL_VM) {
116 		tfp = (void *)kdb_frame;
117 		switch ((intptr_t)vp->valuep) {
118 		case (intptr_t)DB_OFFSET(tf_cs):
119 			reg = (uint16_t *)&tfp->tf_cs;
120 			break;
121 		case (intptr_t)DB_OFFSET(tf_ds):
122 			reg = (uint16_t *)&tfp->tf_vm86_ds;
123 			break;
124 		case (intptr_t)DB_OFFSET(tf_es):
125 			reg = (uint16_t *)&tfp->tf_vm86_es;
126 			break;
127 		case (intptr_t)DB_OFFSET(tf_fs):
128 			reg = (uint16_t *)&tfp->tf_vm86_fs;
129 			break;
130 		}
131 	} else
132 		reg = (uint16_t *)((uintptr_t)kdb_frame + off);
133 	if (op == DB_VAR_GET)
134 		*valuep = *reg;
135 	else
136 		*reg = *valuep;
137 	return (1);
138 }
139 
140 static int
141 db_esp(struct db_variable *vp, db_expr_t *valuep, int op)
142 {
143 
144 	if (kdb_frame == NULL)
145 		return (0);
146 
147 	if (op == DB_VAR_GET)
148 		*valuep = get_esp(kdb_frame);
149 	else if (TF_HAS_STACKREGS(kdb_frame))
150 		kdb_frame->tf_esp = *valuep;
151 	return (1);
152 }
153 
154 static int
155 db_gs(struct db_variable *vp, db_expr_t *valuep, int op)
156 {
157 	struct trapframe_vm86 *tfp;
158 
159 	if (kdb_frame != NULL && kdb_frame->tf_eflags & PSL_VM) {
160 		tfp = (void *)kdb_frame;
161 		if (op == DB_VAR_GET)
162 			*valuep = tfp->tf_vm86_gs;
163 		else
164 			tfp->tf_vm86_gs = *valuep;
165 		return (1);
166 	}
167 	if (op == DB_VAR_GET)
168 		*valuep = rgs();
169 	else
170 		load_gs(*valuep);
171 	return (1);
172 }
173 
174 static int
175 db_ss(struct db_variable *vp, db_expr_t *valuep, int op)
176 {
177 
178 	if (kdb_frame == NULL)
179 		return (0);
180 
181 	if (op == DB_VAR_GET)
182 		*valuep = TF_HAS_STACKREGS(kdb_frame) ? kdb_frame->tf_ss :
183 		    rss();
184 	else if (TF_HAS_STACKREGS(kdb_frame))
185 		kdb_frame->tf_ss = *valuep;
186 	return (1);
187 }
188 
189 #define NORMAL		0
190 #define	TRAP		1
191 #define	INTERRUPT	2
192 #define	SYSCALL		3
193 #define	DOUBLE_FAULT	4
194 #define	TRAP_INTERRUPT	5
195 #define	TRAP_TIMERINT	6
196 
197 static void db_nextframe(struct i386_frame **, db_addr_t *, struct thread *);
198 static int db_numargs(struct i386_frame *);
199 static void db_print_stack_entry(const char *, int, char **, int *, db_addr_t,
200     void *);
201 static void decode_syscall(int, struct thread *);
202 
203 static const char * watchtype_str(int type);
204 int  i386_set_watch(int watchnum, unsigned int watchaddr, int size, int access,
205 		    struct dbreg *d);
206 int  i386_clr_watch(int watchnum, struct dbreg *d);
207 
208 /*
209  * Figure out how many arguments were passed into the frame at "fp".
210  */
211 static int
212 db_numargs(fp)
213 	struct i386_frame *fp;
214 {
215 	char   *argp;
216 	int	inst;
217 	int	args;
218 
219 	argp = (char *)db_get_value((int)&fp->f_retaddr, 4, false);
220 	/*
221 	 * XXX etext is wrong for LKMs.  We should attempt to interpret
222 	 * the instruction at the return address in all cases.  This
223 	 * may require better fault handling.
224 	 */
225 	if (argp < btext || argp >= etext) {
226 		args = -1;
227 	} else {
228 retry:
229 		inst = db_get_value((int)argp, 4, false);
230 		if ((inst & 0xff) == 0x59)	/* popl %ecx */
231 			args = 1;
232 		else if ((inst & 0xffff) == 0xc483)	/* addl $Ibs, %esp */
233 			args = ((inst >> 16) & 0xff) / 4;
234 		else if ((inst & 0xf8ff) == 0xc089) {	/* movl %eax, %Reg */
235 			argp += 2;
236 			goto retry;
237 		} else
238 			args = -1;
239 	}
240 	return (args);
241 }
242 
243 static void
244 db_print_stack_entry(name, narg, argnp, argp, callpc, frame)
245 	const char *name;
246 	int narg;
247 	char **argnp;
248 	int *argp;
249 	db_addr_t callpc;
250 	void *frame;
251 {
252 	int n = narg >= 0 ? narg : 5;
253 
254 	db_printf("%s(", name);
255 	while (n) {
256 		if (argnp)
257 			db_printf("%s=", *argnp++);
258 		db_printf("%r", db_get_value((int)argp, 4, false));
259 		argp++;
260 		if (--n != 0)
261 			db_printf(",");
262 	}
263 	if (narg < 0)
264 		db_printf(",...");
265 	db_printf(") at ");
266 	db_printsym(callpc, DB_STGY_PROC);
267 	if (frame != NULL)
268 		db_printf("/frame 0x%r", (register_t)frame);
269 	db_printf("\n");
270 }
271 
272 static void
273 decode_syscall(int number, struct thread *td)
274 {
275 	struct proc *p;
276 	c_db_sym_t sym;
277 	db_expr_t diff;
278 	sy_call_t *f;
279 	const char *symname;
280 
281 	db_printf(" (%d", number);
282 	p = (td != NULL) ? td->td_proc : NULL;
283 	if (p != NULL && 0 <= number && number < p->p_sysent->sv_size) {
284 		f = p->p_sysent->sv_table[number].sy_call;
285 		sym = db_search_symbol((db_addr_t)f, DB_STGY_ANY, &diff);
286 		if (sym != DB_SYM_NULL && diff == 0) {
287 			db_symbol_values(sym, &symname, NULL);
288 			db_printf(", %s, %s", p->p_sysent->sv_name, symname);
289 		}
290 	}
291 	db_printf(")");
292 }
293 
294 /*
295  * Figure out the next frame up in the call stack.
296  */
297 static void
298 db_nextframe(struct i386_frame **fp, db_addr_t *ip, struct thread *td)
299 {
300 	struct trapframe *tf;
301 	int frame_type;
302 	int eip, esp, ebp;
303 	db_expr_t offset;
304 	c_db_sym_t sym;
305 	const char *name;
306 
307 	eip = db_get_value((int) &(*fp)->f_retaddr, 4, false);
308 	ebp = db_get_value((int) &(*fp)->f_frame, 4, false);
309 
310 	/*
311 	 * Figure out frame type.  We look at the address just before
312 	 * the saved instruction pointer as the saved EIP is after the
313 	 * call function, and if the function being called is marked as
314 	 * dead (such as panic() at the end of dblfault_handler()), then
315 	 * the instruction at the saved EIP will be part of a different
316 	 * function (syscall() in this example) rather than the one that
317 	 * actually made the call.
318 	 */
319 	frame_type = NORMAL;
320 	if (eip >= PMAP_TRM_MIN_ADDRESS) {
321 		sym = db_search_symbol(eip - 1 - setidt_disp, DB_STGY_ANY,
322 		    &offset);
323 	} else {
324 		sym = db_search_symbol(eip - 1, DB_STGY_ANY, &offset);
325 	}
326 	db_symbol_values(sym, &name, NULL);
327 	if (name != NULL) {
328 		if (strcmp(name, "calltrap") == 0 ||
329 		    strcmp(name, "fork_trampoline") == 0)
330 			frame_type = TRAP;
331 		else if (strncmp(name, "Xatpic_intr", 11) == 0 ||
332 		    strncmp(name, "Xapic_isr", 9) == 0)
333 			frame_type = INTERRUPT;
334 		else if (strcmp(name, "Xlcall_syscall") == 0 ||
335 		    strcmp(name, "Xint0x80_syscall") == 0)
336 			frame_type = SYSCALL;
337 		else if (strcmp(name, "dblfault_handler") == 0)
338 			frame_type = DOUBLE_FAULT;
339 		/* XXX: These are interrupts with trap frames. */
340 		else if (strcmp(name, "Xtimerint") == 0)
341 			frame_type = TRAP_TIMERINT;
342 		else if (strcmp(name, "Xcpustop") == 0 ||
343 		    strcmp(name, "Xrendezvous") == 0 ||
344 		    strcmp(name, "Xipi_intr_bitmap_handler") == 0)
345 			frame_type = TRAP_INTERRUPT;
346 	}
347 
348 	/*
349 	 * Normal frames need no special processing.
350 	 */
351 	if (frame_type == NORMAL) {
352 		*ip = (db_addr_t) eip;
353 		*fp = (struct i386_frame *) ebp;
354 		return;
355 	}
356 
357 	db_print_stack_entry(name, 0, 0, 0, eip, &(*fp)->f_frame);
358 
359 	/*
360 	 * For a double fault, we have to snag the values from the
361 	 * previous TSS since a double fault uses a task gate to
362 	 * switch to a known good state.
363 	 */
364 	if (frame_type == DOUBLE_FAULT) {
365 		esp = PCPU_GET(common_tssp)->tss_esp;
366 		eip = PCPU_GET(common_tssp)->tss_eip;
367 		ebp = PCPU_GET(common_tssp)->tss_ebp;
368 		db_printf(
369 		    "--- trap 0x17, eip = %#r, esp = %#r, ebp = %#r ---\n",
370 		    eip, esp, ebp);
371 		*ip = (db_addr_t) eip;
372 		*fp = (struct i386_frame *) ebp;
373 		return;
374 	}
375 
376 	/*
377 	 * Point to base of trapframe which is just above the
378 	 * current frame.
379 	 */
380 	if (frame_type == INTERRUPT)
381 		tf = (struct trapframe *)((int)*fp + 16);
382 	else if (frame_type == TRAP_INTERRUPT)
383 		tf = (struct trapframe *)((int)*fp + 8);
384 	else
385 		tf = (struct trapframe *)((int)*fp + 12);
386 
387 	esp = get_esp(tf);
388 	eip = tf->tf_eip;
389 	ebp = tf->tf_ebp;
390 	switch (frame_type) {
391 	case TRAP:
392 		db_printf("--- trap %#r", tf->tf_trapno);
393 		break;
394 	case SYSCALL:
395 		db_printf("--- syscall");
396 		decode_syscall(tf->tf_eax, td);
397 		break;
398 	case TRAP_TIMERINT:
399 	case TRAP_INTERRUPT:
400 	case INTERRUPT:
401 		db_printf("--- interrupt");
402 		break;
403 	default:
404 		panic("The moon has moved again.");
405 	}
406 	db_printf(", eip = %#r, esp = %#r, ebp = %#r ---\n", eip, esp, ebp);
407 
408 	switch (frame_type) {
409 	case TRAP:
410 	case TRAP_TIMERINT:
411 	case TRAP_INTERRUPT:
412 	case INTERRUPT:
413 		if ((tf->tf_eflags & PSL_VM) != 0 ||
414 		    (tf->tf_cs & SEL_RPL_MASK) != 0)
415 			ebp = 0;
416 		break;
417 	case SYSCALL:
418 		ebp = 0;
419 		break;
420 	}
421 
422 	*ip = (db_addr_t) eip;
423 	*fp = (struct i386_frame *) ebp;
424 }
425 
426 static int
427 db_backtrace(struct thread *td, struct trapframe *tf, struct i386_frame *frame,
428     db_addr_t pc, register_t sp, int count)
429 {
430 	struct i386_frame *actframe;
431 #define MAXNARG	16
432 	char *argnames[MAXNARG], **argnp = NULL;
433 	const char *name;
434 	int *argp;
435 	db_expr_t offset;
436 	c_db_sym_t sym;
437 	int instr, narg;
438 	bool first;
439 
440 	if (db_segsize(tf) == 16) {
441 		db_printf(
442 "--- 16-bit%s, cs:eip = %#x:%#x, ss:esp = %#x:%#x, ebp = %#x, tf = %p ---\n",
443 		    (tf->tf_eflags & PSL_VM) ? " (vm86)" : "",
444 		    tf->tf_cs, tf->tf_eip,
445 		    TF_HAS_STACKREGS(tf) ? tf->tf_ss : rss(),
446 		    TF_HAS_STACKREGS(tf) ? tf->tf_esp : (intptr_t)&tf->tf_esp,
447 		    tf->tf_ebp, tf);
448 		return (0);
449 	}
450 
451 	/* 'frame' can be null initially.  Just print the pc then. */
452 	if (frame == NULL)
453 		goto out;
454 
455 	/*
456 	 * If an indirect call via an invalid pointer caused a trap,
457 	 * %pc contains the invalid address while the return address
458 	 * of the unlucky caller has been saved by CPU on the stack
459 	 * just before the trap frame.  In this case, try to recover
460 	 * the caller's address so that the first frame is assigned
461 	 * to the right spot in the right function, for that is where
462 	 * the failure actually happened.
463 	 *
464 	 * This trick depends on the fault address stashed in tf_err
465 	 * by trap_fatal() before entering KDB.
466 	 */
467 	if (kdb_frame && pc == kdb_frame->tf_err) {
468 		/*
469 		 * Find where the trap frame actually ends.
470 		 * It won't contain tf_esp or tf_ss unless crossing rings.
471 		 */
472 		if (TF_HAS_STACKREGS(kdb_frame))
473 			instr = (int)(kdb_frame + 1);
474 		else
475 			instr = (int)&kdb_frame->tf_esp;
476 		pc = db_get_value(instr, 4, false);
477 	}
478 
479 	if (count == -1)
480 		count = 1024;
481 
482 	first = true;
483 	while (count-- && !db_pager_quit) {
484 		sym = db_search_symbol(pc, DB_STGY_ANY, &offset);
485 		db_symbol_values(sym, &name, NULL);
486 
487 		/*
488 		 * Attempt to determine a (possibly fake) frame that gives
489 		 * the caller's pc.  It may differ from `frame' if the
490 		 * current function never sets up a standard frame or hasn't
491 		 * set one up yet or has just discarded one.  The last two
492 		 * cases can be guessed fairly reliably for code generated
493 		 * by gcc.  The first case is too much trouble to handle in
494 		 * general because the amount of junk on the stack depends
495 		 * on the pc (the special handling of "calltrap", etc. in
496 		 * db_nextframe() works because the `next' pc is special).
497 		 */
498 		actframe = frame;
499 		if (first) {
500 			first = false;
501 			if (sym == C_DB_SYM_NULL && sp != 0) {
502 				/*
503 				 * If a symbol couldn't be found, we've probably
504 				 * jumped to a bogus location, so try and use
505 				 * the return address to find our caller.
506 				 */
507 				db_print_stack_entry(name, 0, 0, 0, pc,
508 				    NULL);
509 				pc = db_get_value(sp, 4, false);
510 				if (db_search_symbol(pc, DB_STGY_PROC,
511 				    &offset) == C_DB_SYM_NULL)
512 					break;
513 				continue;
514 			} else if (tf != NULL) {
515 				instr = db_get_value(pc, 4, false);
516 				if ((instr & 0xffffff) == 0x00e58955) {
517 					/* pushl %ebp; movl %esp, %ebp */
518 					actframe = (void *)(get_esp(tf) - 4);
519 				} else if ((instr & 0xffff) == 0x0000e589) {
520 					/* movl %esp, %ebp */
521 					actframe = (void *)get_esp(tf);
522 					if (tf->tf_ebp == 0) {
523 						/* Fake frame better. */
524 						frame = actframe;
525 					}
526 				} else if ((instr & 0xff) == 0x000000c3) {
527 					/* ret */
528 					actframe = (void *)(get_esp(tf) - 4);
529 				} else if (offset == 0) {
530 					/* Probably an assembler symbol. */
531 					actframe = (void *)(get_esp(tf) - 4);
532 				}
533 			} else if (strcmp(name, "fork_trampoline") == 0) {
534 				/*
535 				 * Don't try to walk back on a stack for a
536 				 * process that hasn't actually been run yet.
537 				 */
538 				db_print_stack_entry(name, 0, 0, 0, pc,
539 				    actframe);
540 				break;
541 			}
542 		}
543 
544 		argp = &actframe->f_arg0;
545 		narg = MAXNARG;
546 		if (sym != NULL && db_sym_numargs(sym, &narg, argnames)) {
547 			argnp = argnames;
548 		} else {
549 			narg = db_numargs(frame);
550 		}
551 
552 		db_print_stack_entry(name, narg, argnp, argp, pc, actframe);
553 
554 		if (actframe != frame) {
555 			/* `frame' belongs to caller. */
556 			pc = (db_addr_t)
557 			    db_get_value((int)&actframe->f_retaddr, 4, false);
558 			continue;
559 		}
560 
561 		db_nextframe(&frame, &pc, td);
562 
563 out:
564 		/*
565 		 * 'frame' can be null here, either because it was initially
566 		 * null or because db_nextframe() found no frame.
567 		 * db_nextframe() may also have found a non-kernel frame.
568 		 * !INKERNEL() classifies both.  Stop tracing if either,
569 		 * after printing the pc if it is the kernel.
570 		 */
571 		if (frame == NULL || frame <= actframe) {
572 			sym = db_search_symbol(pc, DB_STGY_ANY, &offset);
573 			db_symbol_values(sym, &name, NULL);
574 			db_print_stack_entry(name, 0, 0, 0, pc, frame);
575 			break;
576 		}
577 	}
578 
579 	return (0);
580 }
581 
582 void
583 db_trace_self(void)
584 {
585 	struct i386_frame *frame;
586 	db_addr_t callpc;
587 	register_t ebp;
588 
589 	__asm __volatile("movl %%ebp,%0" : "=r" (ebp));
590 	frame = (struct i386_frame *)ebp;
591 	callpc = (db_addr_t)db_get_value((int)&frame->f_retaddr, 4, false);
592 	frame = frame->f_frame;
593 	db_backtrace(curthread, NULL, frame, callpc, 0, -1);
594 }
595 
596 int
597 db_trace_thread(struct thread *thr, int count)
598 {
599 	struct pcb *ctx;
600 	struct trapframe *tf;
601 
602 	ctx = kdb_thr_ctx(thr);
603 	tf = thr == kdb_thread ? kdb_frame : NULL;
604 	return (db_backtrace(thr, tf, (struct i386_frame *)ctx->pcb_ebp,
605 	    ctx->pcb_eip, ctx->pcb_esp, count));
606 }
607 
608 int
609 i386_set_watch(watchnum, watchaddr, size, access, d)
610 	int watchnum;
611 	unsigned int watchaddr;
612 	int size;
613 	int access;
614 	struct dbreg *d;
615 {
616 	int i, len;
617 
618 	if (watchnum == -1) {
619 		for (i = 0; i < 4; i++)
620 			if (!DBREG_DR7_ENABLED(d->dr[7], i))
621 				break;
622 		if (i < 4)
623 			watchnum = i;
624 		else
625 			return (-1);
626 	}
627 
628 	switch (access) {
629 	case DBREG_DR7_EXEC:
630 		size = 1; /* size must be 1 for an execution breakpoint */
631 		/* fall through */
632 	case DBREG_DR7_WRONLY:
633 	case DBREG_DR7_RDWR:
634 		break;
635 	default:
636 		return (-1);
637 	}
638 
639 	/*
640 	 * we can watch a 1, 2, or 4 byte sized location
641 	 */
642 	switch (size) {
643 	case 1:
644 		len = DBREG_DR7_LEN_1;
645 		break;
646 	case 2:
647 		len = DBREG_DR7_LEN_2;
648 		break;
649 	case 4:
650 		len = DBREG_DR7_LEN_4;
651 		break;
652 	default:
653 		return (-1);
654 	}
655 
656 	/* clear the bits we are about to affect */
657 	d->dr[7] &= ~DBREG_DR7_MASK(watchnum);
658 
659 	/* set drN register to the address, N=watchnum */
660 	DBREG_DRX(d, watchnum) = watchaddr;
661 
662 	/* enable the watchpoint */
663 	d->dr[7] |= DBREG_DR7_SET(watchnum, len, access,
664 	    DBREG_DR7_GLOBAL_ENABLE);
665 
666 	return (watchnum);
667 }
668 
669 
670 int
671 i386_clr_watch(watchnum, d)
672 	int watchnum;
673 	struct dbreg *d;
674 {
675 
676 	if (watchnum < 0 || watchnum >= 4)
677 		return (-1);
678 
679 	d->dr[7] &= ~DBREG_DR7_MASK(watchnum);
680 	DBREG_DRX(d, watchnum) = 0;
681 
682 	return (0);
683 }
684 
685 
686 int
687 db_md_set_watchpoint(addr, size)
688 	db_expr_t addr;
689 	db_expr_t size;
690 {
691 	struct dbreg d;
692 	int avail, i, wsize;
693 
694 	fill_dbregs(NULL, &d);
695 
696 	avail = 0;
697 	for(i = 0; i < 4; i++) {
698 		if (!DBREG_DR7_ENABLED(d.dr[7], i))
699 			avail++;
700 	}
701 
702 	if (avail * 4 < size)
703 		return (-1);
704 
705 	for (i = 0; i < 4 && (size > 0); i++) {
706 		if (!DBREG_DR7_ENABLED(d.dr[7], i)) {
707 			if (size > 2)
708 				wsize = 4;
709 			else
710 				wsize = size;
711 			i386_set_watch(i, addr, wsize,
712 				       DBREG_DR7_WRONLY, &d);
713 			addr += wsize;
714 			size -= wsize;
715 		}
716 	}
717 
718 	set_dbregs(NULL, &d);
719 
720 	return(0);
721 }
722 
723 
724 int
725 db_md_clr_watchpoint(addr, size)
726 	db_expr_t addr;
727 	db_expr_t size;
728 {
729 	struct dbreg d;
730 	int i;
731 
732 	fill_dbregs(NULL, &d);
733 
734 	for(i = 0; i < 4; i++) {
735 		if (DBREG_DR7_ENABLED(d.dr[7], i)) {
736 			if ((DBREG_DRX((&d), i) >= addr) &&
737 			    (DBREG_DRX((&d), i) < addr+size))
738 				i386_clr_watch(i, &d);
739 
740 		}
741 	}
742 
743 	set_dbregs(NULL, &d);
744 
745 	return(0);
746 }
747 
748 
749 static const char *
750 watchtype_str(type)
751 	int type;
752 {
753 	switch (type) {
754 		case DBREG_DR7_EXEC   : return "execute";    break;
755 		case DBREG_DR7_RDWR   : return "read/write"; break;
756 		case DBREG_DR7_WRONLY : return "write";	     break;
757 		default		      : return "invalid";    break;
758 	}
759 }
760 
761 
762 void
763 db_md_list_watchpoints(void)
764 {
765 	struct dbreg d;
766 	int i, len, type;
767 
768 	fill_dbregs(NULL, &d);
769 
770 	db_printf("\nhardware watchpoints:\n");
771 	db_printf("  watch    status        type  len     address\n");
772 	db_printf("  -----  --------  ----------  ---  ----------\n");
773 	for (i = 0; i < 4; i++) {
774 		if (DBREG_DR7_ENABLED(d.dr[7], i)) {
775 			type = DBREG_DR7_ACCESS(d.dr[7], i);
776 			len = DBREG_DR7_LEN(d.dr[7], i);
777 			db_printf("  %-5d  %-8s  %10s  %3d  ",
778 			    i, "enabled", watchtype_str(type), len + 1);
779 			db_printsym((db_addr_t)DBREG_DRX(&d, i), DB_STGY_ANY);
780 			db_printf("\n");
781 		} else {
782 			db_printf("  %-5d  disabled\n", i);
783 		}
784 	}
785 
786 	db_printf("\ndebug register values:\n");
787 	for (i = 0; i < 8; i++)
788 		if (i != 4 && i != 5)
789 			db_printf("  dr%d 0x%08x\n", i, DBREG_DRX(&d, i));
790 	db_printf("\n");
791 }
792