xref: /freebsd/sys/i386/i386/db_trace.c (revision 2f513db7)
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 
195 static void db_nextframe(struct i386_frame **, db_addr_t *, struct thread *);
196 static int db_numargs(struct i386_frame *);
197 static void db_print_stack_entry(const char *, int, char **, int *, db_addr_t,
198     void *);
199 static void decode_syscall(int, struct thread *);
200 
201 static const char * watchtype_str(int type);
202 int  i386_set_watch(int watchnum, unsigned int watchaddr, int size, int access,
203 		    struct dbreg *d);
204 int  i386_clr_watch(int watchnum, struct dbreg *d);
205 
206 /*
207  * Figure out how many arguments were passed into the frame at "fp".
208  */
209 static int
210 db_numargs(fp)
211 	struct i386_frame *fp;
212 {
213 	char   *argp;
214 	int	inst;
215 	int	args;
216 
217 	argp = (char *)db_get_value((int)&fp->f_retaddr, 4, false);
218 	/*
219 	 * XXX etext is wrong for LKMs.  We should attempt to interpret
220 	 * the instruction at the return address in all cases.  This
221 	 * may require better fault handling.
222 	 */
223 	if (argp < btext || argp >= etext) {
224 		args = -1;
225 	} else {
226 retry:
227 		inst = db_get_value((int)argp, 4, false);
228 		if ((inst & 0xff) == 0x59)	/* popl %ecx */
229 			args = 1;
230 		else if ((inst & 0xffff) == 0xc483)	/* addl $Ibs, %esp */
231 			args = ((inst >> 16) & 0xff) / 4;
232 		else if ((inst & 0xf8ff) == 0xc089) {	/* movl %eax, %Reg */
233 			argp += 2;
234 			goto retry;
235 		} else
236 			args = -1;
237 	}
238 	return (args);
239 }
240 
241 static void
242 db_print_stack_entry(name, narg, argnp, argp, callpc, frame)
243 	const char *name;
244 	int narg;
245 	char **argnp;
246 	int *argp;
247 	db_addr_t callpc;
248 	void *frame;
249 {
250 	int n = narg >= 0 ? narg : 5;
251 
252 	db_printf("%s(", name);
253 	while (n) {
254 		if (argnp)
255 			db_printf("%s=", *argnp++);
256 		db_printf("%r", db_get_value((int)argp, 4, false));
257 		argp++;
258 		if (--n != 0)
259 			db_printf(",");
260 	}
261 	if (narg < 0)
262 		db_printf(",...");
263 	db_printf(") at ");
264 	db_printsym(callpc, DB_STGY_PROC);
265 	if (frame != NULL)
266 		db_printf("/frame 0x%r", (register_t)frame);
267 	db_printf("\n");
268 }
269 
270 static void
271 decode_syscall(int number, struct thread *td)
272 {
273 	struct proc *p;
274 	c_db_sym_t sym;
275 	db_expr_t diff;
276 	sy_call_t *f;
277 	const char *symname;
278 
279 	db_printf(" (%d", number);
280 	p = (td != NULL) ? td->td_proc : NULL;
281 	if (p != NULL && 0 <= number && number < p->p_sysent->sv_size) {
282 		f = p->p_sysent->sv_table[number].sy_call;
283 		sym = db_search_symbol((db_addr_t)f, DB_STGY_ANY, &diff);
284 		if (sym != DB_SYM_NULL && diff == 0) {
285 			db_symbol_values(sym, &symname, NULL);
286 			db_printf(", %s, %s", p->p_sysent->sv_name, symname);
287 		}
288 	}
289 	db_printf(")");
290 }
291 
292 /*
293  * Figure out the next frame up in the call stack.
294  */
295 static void
296 db_nextframe(struct i386_frame **fp, db_addr_t *ip, struct thread *td)
297 {
298 	struct trapframe *tf;
299 	int frame_type;
300 	int eip, esp, ebp;
301 	db_expr_t offset;
302 	c_db_sym_t sym;
303 	const char *name;
304 
305 	eip = db_get_value((int) &(*fp)->f_retaddr, 4, false);
306 	ebp = db_get_value((int) &(*fp)->f_frame, 4, false);
307 
308 	/*
309 	 * Figure out frame type.  We look at the address just before
310 	 * the saved instruction pointer as the saved EIP is after the
311 	 * call function, and if the function being called is marked as
312 	 * dead (such as panic() at the end of dblfault_handler()), then
313 	 * the instruction at the saved EIP will be part of a different
314 	 * function (syscall() in this example) rather than the one that
315 	 * actually made the call.
316 	 */
317 	frame_type = NORMAL;
318 
319 	if (eip >= PMAP_TRM_MIN_ADDRESS) {
320 		sym = db_search_symbol(eip - 1 - setidt_disp, DB_STGY_ANY,
321 		    &offset);
322 	} else {
323 		sym = db_search_symbol(eip - 1, DB_STGY_ANY, &offset);
324 	}
325 	db_symbol_values(sym, &name, NULL);
326 	if (name != NULL) {
327 		if (strcmp(name, "calltrap") == 0 ||
328 		    strcmp(name, "fork_trampoline") == 0)
329 			frame_type = TRAP;
330 		else if (strncmp(name, "Xatpic_intr", 11) == 0 ||
331 		    strncmp(name, "Xapic_isr", 9) == 0) {
332 			frame_type = INTERRUPT;
333 		} else if (strcmp(name, "Xlcall_syscall") == 0 ||
334 		    strcmp(name, "Xint0x80_syscall") == 0)
335 			frame_type = SYSCALL;
336 		else if (strcmp(name, "dblfault_handler") == 0)
337 			frame_type = DOUBLE_FAULT;
338 		else if (strcmp(name, "Xtimerint") == 0 ||
339 		    strcmp(name, "Xxen_intr_upcall") == 0)
340 			frame_type = INTERRUPT;
341 		else if (strcmp(name, "Xcpustop") == 0 ||
342 		    strcmp(name, "Xrendezvous") == 0 ||
343 		    strcmp(name, "Xipi_intr_bitmap_handler") == 0) {
344 			/* No arguments. */
345 			frame_type = INTERRUPT;
346 		}
347 	}
348 
349 	/*
350 	 * Normal frames need no special processing.
351 	 */
352 	if (frame_type == NORMAL) {
353 		*ip = (db_addr_t) eip;
354 		*fp = (struct i386_frame *) ebp;
355 		return;
356 	}
357 
358 	db_print_stack_entry(name, 0, 0, 0, eip, &(*fp)->f_frame);
359 
360 	/*
361 	 * For a double fault, we have to snag the values from the
362 	 * previous TSS since a double fault uses a task gate to
363 	 * switch to a known good state.
364 	 */
365 	if (frame_type == DOUBLE_FAULT) {
366 		esp = PCPU_GET(common_tssp)->tss_esp;
367 		eip = PCPU_GET(common_tssp)->tss_eip;
368 		ebp = PCPU_GET(common_tssp)->tss_ebp;
369 		db_printf(
370 		    "--- trap 0x17, eip = %#r, esp = %#r, ebp = %#r ---\n",
371 		    eip, esp, ebp);
372 		*ip = (db_addr_t) eip;
373 		*fp = (struct i386_frame *) ebp;
374 		return;
375 	}
376 
377 	/*
378 	 * Point to base of trapframe which is just above the current
379 	 * frame.  Pointer to it was put into %ebp by the kernel entry
380 	 * code.
381 	 */
382 	tf = (struct trapframe *)(*fp)->f_frame;
383 
384 	/*
385 	 * This can be the case for e.g. fork_trampoline, last frame
386 	 * of a kernel thread stack.
387 	 */
388 	if (tf == NULL) {
389 		*ip = 0;
390 		*fp = 0;
391 		db_printf("--- kthread start\n");
392 		return;
393 	}
394 
395 	esp = get_esp(tf);
396 	eip = tf->tf_eip;
397 	ebp = tf->tf_ebp;
398 	switch (frame_type) {
399 	case TRAP:
400 		db_printf("--- trap %#r", tf->tf_trapno);
401 		break;
402 	case SYSCALL:
403 		db_printf("--- syscall");
404 		decode_syscall(tf->tf_eax, td);
405 		break;
406 	case INTERRUPT:
407 		db_printf("--- interrupt");
408 		break;
409 	default:
410 		panic("The moon has moved again.");
411 	}
412 	db_printf(", eip = %#r, esp = %#r, ebp = %#r ---\n", eip, esp, ebp);
413 
414 	/*
415 	 * Detect the last (trap) frame on the kernel stack, where we
416 	 * entered kernel from usermode.  Terminate tracing in this
417 	 * case.
418 	 */
419 	switch (frame_type) {
420 	case TRAP:
421 	case INTERRUPT:
422 		if (!TRAPF_USERMODE(tf))
423 			break;
424 		/* FALLTHROUGH */
425 	case SYSCALL:
426 		ebp = 0;
427 		eip = 0;
428 		break;
429 	}
430 
431 	*ip = (db_addr_t) eip;
432 	*fp = (struct i386_frame *) ebp;
433 }
434 
435 static int
436 db_backtrace(struct thread *td, struct trapframe *tf, struct i386_frame *frame,
437     db_addr_t pc, register_t sp, int count)
438 {
439 	struct i386_frame *actframe;
440 #define MAXNARG	16
441 	char *argnames[MAXNARG], **argnp = NULL;
442 	const char *name;
443 	int *argp;
444 	db_expr_t offset;
445 	c_db_sym_t sym;
446 	int instr, narg;
447 	bool first;
448 
449 	if (db_segsize(tf) == 16) {
450 		db_printf(
451 "--- 16-bit%s, cs:eip = %#x:%#x, ss:esp = %#x:%#x, ebp = %#x, tf = %p ---\n",
452 		    (tf->tf_eflags & PSL_VM) ? " (vm86)" : "",
453 		    tf->tf_cs, tf->tf_eip,
454 		    TF_HAS_STACKREGS(tf) ? tf->tf_ss : rss(),
455 		    TF_HAS_STACKREGS(tf) ? tf->tf_esp : (intptr_t)&tf->tf_esp,
456 		    tf->tf_ebp, tf);
457 		return (0);
458 	}
459 
460 	/* 'frame' can be null initially.  Just print the pc then. */
461 	if (frame == NULL)
462 		goto out;
463 
464 	/*
465 	 * If an indirect call via an invalid pointer caused a trap,
466 	 * %pc contains the invalid address while the return address
467 	 * of the unlucky caller has been saved by CPU on the stack
468 	 * just before the trap frame.  In this case, try to recover
469 	 * the caller's address so that the first frame is assigned
470 	 * to the right spot in the right function, for that is where
471 	 * the failure actually happened.
472 	 *
473 	 * This trick depends on the fault address stashed in tf_err
474 	 * by trap_fatal() before entering KDB.
475 	 */
476 	if (kdb_frame && pc == kdb_frame->tf_err) {
477 		/*
478 		 * Find where the trap frame actually ends.
479 		 * It won't contain tf_esp or tf_ss unless crossing rings.
480 		 */
481 		if (TF_HAS_STACKREGS(kdb_frame))
482 			instr = (int)(kdb_frame + 1);
483 		else
484 			instr = (int)&kdb_frame->tf_esp;
485 		pc = db_get_value(instr, 4, false);
486 	}
487 
488 	if (count == -1)
489 		count = 1024;
490 
491 	first = true;
492 	while (count-- && !db_pager_quit) {
493 		sym = db_search_symbol(pc, DB_STGY_ANY, &offset);
494 		db_symbol_values(sym, &name, NULL);
495 
496 		/*
497 		 * Attempt to determine a (possibly fake) frame that gives
498 		 * the caller's pc.  It may differ from `frame' if the
499 		 * current function never sets up a standard frame or hasn't
500 		 * set one up yet or has just discarded one.  The last two
501 		 * cases can be guessed fairly reliably for code generated
502 		 * by gcc.  The first case is too much trouble to handle in
503 		 * general because the amount of junk on the stack depends
504 		 * on the pc (the special handling of "calltrap", etc. in
505 		 * db_nextframe() works because the `next' pc is special).
506 		 */
507 		actframe = frame;
508 		if (first) {
509 			first = false;
510 			if (sym == C_DB_SYM_NULL && sp != 0) {
511 				/*
512 				 * If a symbol couldn't be found, we've probably
513 				 * jumped to a bogus location, so try and use
514 				 * the return address to find our caller.
515 				 */
516 				db_print_stack_entry(name, 0, 0, 0, pc,
517 				    NULL);
518 				pc = db_get_value(sp, 4, false);
519 				if (db_search_symbol(pc, DB_STGY_PROC,
520 				    &offset) == C_DB_SYM_NULL)
521 					break;
522 				continue;
523 			} else if (tf != NULL) {
524 				instr = db_get_value(pc, 4, false);
525 				if ((instr & 0xffffff) == 0x00e58955) {
526 					/* pushl %ebp; movl %esp, %ebp */
527 					actframe = (void *)(get_esp(tf) - 4);
528 				} else if ((instr & 0xffff) == 0x0000e589) {
529 					/* movl %esp, %ebp */
530 					actframe = (void *)get_esp(tf);
531 					if (tf->tf_ebp == 0) {
532 						/* Fake frame better. */
533 						frame = actframe;
534 					}
535 				} else if ((instr & 0xff) == 0x000000c3) {
536 					/* ret */
537 					actframe = (void *)(get_esp(tf) - 4);
538 				} else if (offset == 0) {
539 					/* Probably an assembler symbol. */
540 					actframe = (void *)(get_esp(tf) - 4);
541 				}
542 			} else if (strcmp(name, "fork_trampoline") == 0) {
543 				/*
544 				 * Don't try to walk back on a stack for a
545 				 * process that hasn't actually been run yet.
546 				 */
547 				db_print_stack_entry(name, 0, 0, 0, pc,
548 				    actframe);
549 				break;
550 			}
551 		}
552 
553 		argp = &actframe->f_arg0;
554 		narg = MAXNARG;
555 		if (sym != NULL && db_sym_numargs(sym, &narg, argnames)) {
556 			argnp = argnames;
557 		} else {
558 			narg = db_numargs(frame);
559 		}
560 
561 		db_print_stack_entry(name, narg, argnp, argp, pc, actframe);
562 
563 		if (actframe != frame) {
564 			/* `frame' belongs to caller. */
565 			pc = (db_addr_t)
566 			    db_get_value((int)&actframe->f_retaddr, 4, false);
567 			continue;
568 		}
569 
570 		db_nextframe(&frame, &pc, td);
571 
572 out:
573 		/*
574 		 * 'frame' can be null here, either because it was initially
575 		 * null or because db_nextframe() found no frame.
576 		 * db_nextframe() may also have found a non-kernel frame.
577 		 * !INKERNEL() classifies both.  Stop tracing if either,
578 		 * after printing the pc if it is the kernel.
579 		 */
580 		if (frame == NULL || frame <= actframe) {
581 			if (pc != 0) {
582 				sym = db_search_symbol(pc, DB_STGY_ANY,
583 				    &offset);
584 				db_symbol_values(sym, &name, NULL);
585 				db_print_stack_entry(name, 0, 0, 0, pc, frame);
586 			}
587 			break;
588 		}
589 	}
590 
591 	return (0);
592 }
593 
594 void
595 db_trace_self(void)
596 {
597 	struct i386_frame *frame;
598 	db_addr_t callpc;
599 	register_t ebp;
600 
601 	__asm __volatile("movl %%ebp,%0" : "=r" (ebp));
602 	frame = (struct i386_frame *)ebp;
603 	callpc = (db_addr_t)db_get_value((int)&frame->f_retaddr, 4, false);
604 	frame = frame->f_frame;
605 	db_backtrace(curthread, NULL, frame, callpc, 0, -1);
606 }
607 
608 int
609 db_trace_thread(struct thread *thr, int count)
610 {
611 	struct pcb *ctx;
612 	struct trapframe *tf;
613 
614 	ctx = kdb_thr_ctx(thr);
615 	tf = thr == kdb_thread ? kdb_frame : NULL;
616 	return (db_backtrace(thr, tf, (struct i386_frame *)ctx->pcb_ebp,
617 	    ctx->pcb_eip, ctx->pcb_esp, count));
618 }
619 
620 int
621 i386_set_watch(watchnum, watchaddr, size, access, d)
622 	int watchnum;
623 	unsigned int watchaddr;
624 	int size;
625 	int access;
626 	struct dbreg *d;
627 {
628 	int i, len;
629 
630 	if (watchnum == -1) {
631 		for (i = 0; i < 4; i++)
632 			if (!DBREG_DR7_ENABLED(d->dr[7], i))
633 				break;
634 		if (i < 4)
635 			watchnum = i;
636 		else
637 			return (-1);
638 	}
639 
640 	switch (access) {
641 	case DBREG_DR7_EXEC:
642 		size = 1; /* size must be 1 for an execution breakpoint */
643 		/* fall through */
644 	case DBREG_DR7_WRONLY:
645 	case DBREG_DR7_RDWR:
646 		break;
647 	default:
648 		return (-1);
649 	}
650 
651 	/*
652 	 * we can watch a 1, 2, or 4 byte sized location
653 	 */
654 	switch (size) {
655 	case 1:
656 		len = DBREG_DR7_LEN_1;
657 		break;
658 	case 2:
659 		len = DBREG_DR7_LEN_2;
660 		break;
661 	case 4:
662 		len = DBREG_DR7_LEN_4;
663 		break;
664 	default:
665 		return (-1);
666 	}
667 
668 	/* clear the bits we are about to affect */
669 	d->dr[7] &= ~DBREG_DR7_MASK(watchnum);
670 
671 	/* set drN register to the address, N=watchnum */
672 	DBREG_DRX(d, watchnum) = watchaddr;
673 
674 	/* enable the watchpoint */
675 	d->dr[7] |= DBREG_DR7_SET(watchnum, len, access,
676 	    DBREG_DR7_GLOBAL_ENABLE);
677 
678 	return (watchnum);
679 }
680 
681 
682 int
683 i386_clr_watch(watchnum, d)
684 	int watchnum;
685 	struct dbreg *d;
686 {
687 
688 	if (watchnum < 0 || watchnum >= 4)
689 		return (-1);
690 
691 	d->dr[7] &= ~DBREG_DR7_MASK(watchnum);
692 	DBREG_DRX(d, watchnum) = 0;
693 
694 	return (0);
695 }
696 
697 
698 int
699 db_md_set_watchpoint(addr, size)
700 	db_expr_t addr;
701 	db_expr_t size;
702 {
703 	struct dbreg d;
704 	int avail, i, wsize;
705 
706 	fill_dbregs(NULL, &d);
707 
708 	avail = 0;
709 	for(i = 0; i < 4; i++) {
710 		if (!DBREG_DR7_ENABLED(d.dr[7], i))
711 			avail++;
712 	}
713 
714 	if (avail * 4 < size)
715 		return (-1);
716 
717 	for (i = 0; i < 4 && (size > 0); i++) {
718 		if (!DBREG_DR7_ENABLED(d.dr[7], i)) {
719 			if (size > 2)
720 				wsize = 4;
721 			else
722 				wsize = size;
723 			i386_set_watch(i, addr, wsize,
724 				       DBREG_DR7_WRONLY, &d);
725 			addr += wsize;
726 			size -= wsize;
727 		}
728 	}
729 
730 	set_dbregs(NULL, &d);
731 
732 	return(0);
733 }
734 
735 
736 int
737 db_md_clr_watchpoint(addr, size)
738 	db_expr_t addr;
739 	db_expr_t size;
740 {
741 	struct dbreg d;
742 	int i;
743 
744 	fill_dbregs(NULL, &d);
745 
746 	for(i = 0; i < 4; i++) {
747 		if (DBREG_DR7_ENABLED(d.dr[7], i)) {
748 			if ((DBREG_DRX((&d), i) >= addr) &&
749 			    (DBREG_DRX((&d), i) < addr+size))
750 				i386_clr_watch(i, &d);
751 
752 		}
753 	}
754 
755 	set_dbregs(NULL, &d);
756 
757 	return(0);
758 }
759 
760 
761 static const char *
762 watchtype_str(type)
763 	int type;
764 {
765 	switch (type) {
766 		case DBREG_DR7_EXEC   : return "execute";    break;
767 		case DBREG_DR7_RDWR   : return "read/write"; break;
768 		case DBREG_DR7_WRONLY : return "write";	     break;
769 		default		      : return "invalid";    break;
770 	}
771 }
772 
773 
774 void
775 db_md_list_watchpoints(void)
776 {
777 	struct dbreg d;
778 	int i, len, type;
779 
780 	fill_dbregs(NULL, &d);
781 
782 	db_printf("\nhardware watchpoints:\n");
783 	db_printf("  watch    status        type  len     address\n");
784 	db_printf("  -----  --------  ----------  ---  ----------\n");
785 	for (i = 0; i < 4; i++) {
786 		if (DBREG_DR7_ENABLED(d.dr[7], i)) {
787 			type = DBREG_DR7_ACCESS(d.dr[7], i);
788 			len = DBREG_DR7_LEN(d.dr[7], i);
789 			db_printf("  %-5d  %-8s  %10s  %3d  ",
790 			    i, "enabled", watchtype_str(type), len + 1);
791 			db_printsym((db_addr_t)DBREG_DRX(&d, i), DB_STGY_ANY);
792 			db_printf("\n");
793 		} else {
794 			db_printf("  %-5d  disabled\n", i);
795 		}
796 	}
797 
798 	db_printf("\ndebug register values:\n");
799 	for (i = 0; i < 8; i++)
800 		if (i != 4 && i != 5)
801 			db_printf("  dr%d 0x%08x\n", i, DBREG_DRX(&d, i));
802 	db_printf("\n");
803 }
804