xref: /xnu-8019.80.24/osfmk/kdp/ml/arm/kdp_machdep.c (revision a325d9c4a84054e40bbe985afedcb50ab80993ea)
1 /*
2  * Copyright (c) 2000-2016 Apple Inc. All rights reserved.
3  *
4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5  *
6  * This file contains Original Code and/or Modifications of Original Code
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8  * Version 2.0 (the 'License'). You may not use this file except in
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10  * may not be used to create, or enable the creation or redistribution of,
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15  * Please obtain a copy of the License at
16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
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20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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27  */
28 
29 #include <mach/mach_types.h>
30 #include <mach/exception_types.h>
31 #include <arm/exception.h>
32 #include <arm/pmap.h>
33 #include <arm/proc_reg.h>
34 #include <arm/thread.h>
35 #include <arm/trap.h>
36 #include <arm/cpu_data_internal.h>
37 #include <kdp/kdp_internal.h>
38 #include <kern/debug.h>
39 #include <IOKit/IOPlatformExpert.h>
40 #include <libkern/OSAtomic.h>
41 #include <vm/vm_map.h>
42 
43 #if defined(HAS_APPLE_PAC)
44 #include <ptrauth.h>
45 #endif
46 
47 #define KDP_TEST_HARNESS 0
48 #if KDP_TEST_HARNESS
49 #define dprintf(x) kprintf x
50 #else
51 #define dprintf(x) do {} while (0)
52 #endif
53 
54 void            halt_all_cpus(boolean_t);
55 void kdp_call(void);
56 int kdp_getc(void);
57 int machine_trace_thread(thread_t thread,
58     char * tracepos,
59     char * tracebound,
60     int nframes,
61     uint32_t * thread_trace_flags);
62 int machine_trace_thread64(thread_t thread,
63     char * tracepos,
64     char * tracebound,
65     int nframes,
66     uint32_t * thread_trace_flags);
67 
68 void kdp_trap(unsigned int, struct arm_saved_state * saved_state);
69 
70 extern bool machine_trace_thread_validate_kva(vm_offset_t addr);
71 
72 #if CONFIG_KDP_INTERACTIVE_DEBUGGING
73 void
kdp_exception(unsigned char * pkt,int * len,unsigned short * remote_port,unsigned int exception,unsigned int code,unsigned int subcode)74 kdp_exception(
75 	unsigned char * pkt, int * len, unsigned short * remote_port, unsigned int exception, unsigned int code, unsigned int subcode)
76 {
77 	struct {
78 		kdp_exception_t pkt;
79 		kdp_exc_info_t exc;
80 	} aligned_pkt;
81 
82 	kdp_exception_t * rq = (kdp_exception_t *)&aligned_pkt;
83 
84 	bcopy((char *)pkt, (char *)rq, sizeof(*rq));
85 	rq->hdr.request = KDP_EXCEPTION;
86 	rq->hdr.is_reply = 0;
87 	rq->hdr.seq = kdp.exception_seq;
88 	rq->hdr.key = 0;
89 	rq->hdr.len = sizeof(*rq) + sizeof(kdp_exc_info_t);
90 
91 	rq->n_exc_info = 1;
92 	rq->exc_info[0].cpu = 0;
93 	rq->exc_info[0].exception = exception;
94 	rq->exc_info[0].code = code;
95 	rq->exc_info[0].subcode = subcode;
96 
97 	rq->hdr.len += rq->n_exc_info * sizeof(kdp_exc_info_t);
98 
99 	bcopy((char *)rq, (char *)pkt, rq->hdr.len);
100 
101 	kdp.exception_ack_needed = TRUE;
102 
103 	*remote_port = kdp.exception_port;
104 	*len = rq->hdr.len;
105 }
106 
107 boolean_t
kdp_exception_ack(unsigned char * pkt,int len)108 kdp_exception_ack(unsigned char * pkt, int len)
109 {
110 	kdp_exception_ack_t aligned_pkt;
111 	kdp_exception_ack_t * rq = (kdp_exception_ack_t *)&aligned_pkt;
112 
113 	if ((unsigned)len < sizeof(*rq)) {
114 		return FALSE;
115 	}
116 
117 	bcopy((char *)pkt, (char *)rq, sizeof(*rq));
118 
119 	if (!rq->hdr.is_reply || rq->hdr.request != KDP_EXCEPTION) {
120 		return FALSE;
121 	}
122 
123 	dprintf(("kdp_exception_ack seq %x %x\n", rq->hdr.seq, kdp.exception_seq));
124 
125 	if (rq->hdr.seq == kdp.exception_seq) {
126 		kdp.exception_ack_needed = FALSE;
127 		kdp.exception_seq++;
128 	}
129 	return TRUE;
130 }
131 
132 static void
kdp_getintegerstate(char * out_state)133 kdp_getintegerstate(char * out_state)
134 {
135 #if defined(__arm__)
136 	struct arm_thread_state thread_state;
137 	struct arm_saved_state *saved_state;
138 
139 	saved_state = kdp.saved_state;
140 
141 	bzero((char *) &thread_state, sizeof(struct arm_thread_state));
142 
143 	saved_state_to_thread_state32(saved_state, &thread_state);
144 
145 	bcopy((char *) &thread_state, (char *) out_state, sizeof(struct arm_thread_state));
146 #elif defined(__arm64__)
147 	struct arm_thread_state64 thread_state64;
148 	arm_saved_state_t *saved_state;
149 
150 	saved_state = kdp.saved_state;
151 	assert(is_saved_state64(saved_state));
152 
153 	bzero((char *) &thread_state64, sizeof(struct arm_thread_state64));
154 
155 	saved_state_to_thread_state64(saved_state, &thread_state64);
156 
157 	bcopy((char *) &thread_state64, (char *) out_state, sizeof(struct arm_thread_state64));
158 #else
159 #error Unknown architecture.
160 #endif
161 }
162 
163 kdp_error_t
kdp_machine_read_regs(__unused unsigned int cpu,unsigned int flavor,char * data,int * size)164 kdp_machine_read_regs(__unused unsigned int cpu, unsigned int flavor, char * data, int * size)
165 {
166 	switch (flavor) {
167 #if defined(__arm__)
168 	case ARM_THREAD_STATE:
169 		dprintf(("kdp_readregs THREAD_STATE\n"));
170 		kdp_getintegerstate(data);
171 		*size = ARM_THREAD_STATE_COUNT * sizeof(int);
172 		return KDPERR_NO_ERROR;
173 #elif defined(__arm64__)
174 	case ARM_THREAD_STATE64:
175 		dprintf(("kdp_readregs THREAD_STATE64\n"));
176 		kdp_getintegerstate(data);
177 		*size = ARM_THREAD_STATE64_COUNT * sizeof(int);
178 		return KDPERR_NO_ERROR;
179 #endif
180 
181 	case ARM_VFP_STATE:
182 		dprintf(("kdp_readregs THREAD_FPSTATE\n"));
183 		bzero((char *) data, sizeof(struct arm_vfp_state));
184 		*size = ARM_VFP_STATE_COUNT * sizeof(int);
185 		return KDPERR_NO_ERROR;
186 
187 	default:
188 		dprintf(("kdp_readregs bad flavor %d\n"));
189 		return KDPERR_BADFLAVOR;
190 	}
191 }
192 
193 static void
kdp_setintegerstate(char * state_in)194 kdp_setintegerstate(char * state_in)
195 {
196 #if defined(__arm__)
197 	struct arm_thread_state thread_state;
198 	struct arm_saved_state *saved_state;
199 
200 	bcopy((char *) state_in, (char *) &thread_state, sizeof(struct arm_thread_state));
201 	saved_state = kdp.saved_state;
202 
203 	thread_state32_to_saved_state(&thread_state, saved_state);
204 #elif defined(__arm64__)
205 	struct arm_thread_state64 thread_state64;
206 	struct arm_saved_state *saved_state;
207 
208 	bcopy((char *) state_in, (char *) &thread_state64, sizeof(struct arm_thread_state64));
209 	saved_state = kdp.saved_state;
210 	assert(is_saved_state64(saved_state));
211 
212 	thread_state64_to_saved_state(&thread_state64, saved_state);
213 	set_saved_state_cpsr(saved_state, thread_state64.cpsr); /* override CPSR sanitization */
214 #else
215 #error Unknown architecture.
216 #endif
217 }
218 
219 kdp_error_t
kdp_machine_write_regs(__unused unsigned int cpu,unsigned int flavor,char * data,__unused int * size)220 kdp_machine_write_regs(__unused unsigned int cpu, unsigned int flavor, char * data, __unused int * size)
221 {
222 	switch (flavor) {
223 #if defined(__arm__)
224 	case ARM_THREAD_STATE:
225 		dprintf(("kdp_writeregs THREAD_STATE\n"));
226 		kdp_setintegerstate(data);
227 		return KDPERR_NO_ERROR;
228 #elif defined(__arm64__)
229 	case ARM_THREAD_STATE64:
230 		dprintf(("kdp_writeregs THREAD_STATE64\n"));
231 		kdp_setintegerstate(data);
232 		return KDPERR_NO_ERROR;
233 #endif
234 
235 	case ARM_VFP_STATE:
236 		dprintf(("kdp_writeregs THREAD_FPSTATE\n"));
237 		return KDPERR_NO_ERROR;
238 
239 	default:
240 		dprintf(("kdp_writeregs bad flavor %d\n"));
241 		return KDPERR_BADFLAVOR;
242 	}
243 }
244 
245 void
kdp_machine_hostinfo(kdp_hostinfo_t * hostinfo)246 kdp_machine_hostinfo(kdp_hostinfo_t * hostinfo)
247 {
248 	hostinfo->cpus_mask = 1;
249 	hostinfo->cpu_type = slot_type(0);
250 	hostinfo->cpu_subtype = slot_subtype(0);
251 }
252 
253 __attribute__((noreturn))
254 void
kdp_panic(const char * fmt,...)255 kdp_panic(const char * fmt, ...)
256 {
257 	char kdp_fmt[256];
258 	va_list args;
259 
260 	va_start(args, fmt);
261 	(void) snprintf(kdp_fmt, sizeof(kdp_fmt), "kdp panic: %s", fmt);
262 	vprintf(kdp_fmt, args);
263 	va_end(args);
264 
265 	while (1) {
266 	}
267 	;
268 }
269 
270 int
kdp_intr_disbl(void)271 kdp_intr_disbl(void)
272 {
273 	return splhigh();
274 }
275 
276 void
kdp_intr_enbl(int s)277 kdp_intr_enbl(int s)
278 {
279 	splx(s);
280 }
281 
282 void
kdp_us_spin(int usec)283 kdp_us_spin(int usec)
284 {
285 	delay(usec / 100);
286 }
287 
288 void
kdp_call(void)289 kdp_call(void)
290 {
291 	Debugger("inline call to debugger(machine_startup)");
292 }
293 
294 int
kdp_getc(void)295 kdp_getc(void)
296 {
297 	return console_try_read_char();
298 }
299 
300 void
kdp_machine_get_breakinsn(uint8_t * bytes,uint32_t * size)301 kdp_machine_get_breakinsn(uint8_t * bytes, uint32_t * size)
302 {
303 	*(uint32_t *)bytes = GDB_TRAP_INSTR1;
304 	*size = sizeof(uint32_t);
305 }
306 
307 void
kdp_sync_cache(void)308 kdp_sync_cache(void)
309 {
310 }
311 
312 int
kdp_machine_ioport_read(kdp_readioport_req_t * rq,caddr_t data,uint16_t lcpu)313 kdp_machine_ioport_read(kdp_readioport_req_t * rq, caddr_t data, uint16_t lcpu)
314 {
315 #pragma unused(rq, data, lcpu)
316 	return 0;
317 }
318 
319 int
kdp_machine_ioport_write(kdp_writeioport_req_t * rq,caddr_t data,uint16_t lcpu)320 kdp_machine_ioport_write(kdp_writeioport_req_t * rq, caddr_t data, uint16_t lcpu)
321 {
322 #pragma unused(rq, data, lcpu)
323 	return 0;
324 }
325 
326 int
kdp_machine_msr64_read(kdp_readmsr64_req_t * rq,caddr_t data,uint16_t lcpu)327 kdp_machine_msr64_read(kdp_readmsr64_req_t *rq, caddr_t data, uint16_t lcpu)
328 {
329 #pragma unused(rq, data, lcpu)
330 	return 0;
331 }
332 
333 int
kdp_machine_msr64_write(kdp_writemsr64_req_t * rq,caddr_t data,uint16_t lcpu)334 kdp_machine_msr64_write(kdp_writemsr64_req_t *rq, caddr_t data, uint16_t lcpu)
335 {
336 #pragma unused(rq, data, lcpu)
337 	return 0;
338 }
339 #endif /* CONFIG_KDP_INTERACTIVE_DEBUGGING */
340 
341 void
kdp_trap(unsigned int exception,struct arm_saved_state * saved_state)342 kdp_trap(unsigned int exception, struct arm_saved_state * saved_state)
343 {
344 	handle_debugger_trap(exception, 0, 0, saved_state);
345 
346 #if defined(__arm__)
347 	if (saved_state->cpsr & PSR_TF) {
348 		unsigned short instr = *((unsigned short *)(saved_state->pc));
349 		if ((instr == (GDB_TRAP_INSTR1 & 0xFFFF)) || (instr == (GDB_TRAP_INSTR2 & 0xFFFF))) {
350 			saved_state->pc += 2;
351 		}
352 	} else {
353 		unsigned int instr = *((unsigned int *)(saved_state->pc));
354 		if ((instr == GDB_TRAP_INSTR1) || (instr == GDB_TRAP_INSTR2)) {
355 			saved_state->pc += 4;
356 		}
357 	}
358 
359 #elif defined(__arm64__)
360 	assert(is_saved_state64(saved_state));
361 
362 	uint32_t instr = *((uint32_t *)get_saved_state_pc(saved_state));
363 
364 	/*
365 	 * As long as we are using the arm32 trap encoding to handling
366 	 * traps to the debugger, we should identify both variants and
367 	 * increment for both of them.
368 	 */
369 	if ((instr == GDB_TRAP_INSTR1) || (instr == GDB_TRAP_INSTR2)) {
370 		add_saved_state_pc(saved_state, 4);
371 	}
372 #else
373 #error Unknown architecture.
374 #endif
375 }
376 
377 #define ARM32_LR_OFFSET 4
378 #define ARM64_LR_OFFSET 8
379 
380 /*
381  * Since sizeof (struct thread_snapshot) % 4 == 2
382  * make sure the compiler does not try to use word-aligned
383  * access to this data, which can result in alignment faults
384  * that can't be emulated in KDP context.
385  */
386 typedef uint32_t uint32_align2_t __attribute__((aligned(2)));
387 
388 #if !defined(__arm64__)
389 
390 int
machine_trace_thread(thread_t thread,char * tracepos,char * tracebound,int nframes,uint32_t * thread_trace_flags)391 machine_trace_thread(thread_t thread,
392     char * tracepos,
393     char * tracebound,
394     int nframes,
395     uint32_t * thread_trace_flags)
396 {
397 	uint32_align2_t * tracebuf = (uint32_align2_t *)tracepos;
398 
399 	vm_size_t framesize = sizeof(uint32_t);
400 
401 	vm_offset_t stacklimit        = 0;
402 	vm_offset_t stacklimit_bottom = 0;
403 	int framecount                = 0;
404 	uint32_t short_fp             = 0;
405 	vm_offset_t fp                = 0;
406 	vm_offset_t pc, sp;
407 	vm_offset_t prevfp            = 0;
408 	uint32_t prevlr               = 0;
409 	struct arm_saved_state * state;
410 	vm_offset_t kern_virt_addr = 0;
411 
412 	nframes = (tracebound > tracepos) ? MIN(nframes, (int)((tracebound - tracepos) / framesize)) : 0;
413 	if (!nframes) {
414 		return 0;
415 	}
416 	framecount = 0;
417 
418 #if defined(__arm__)
419 	/* kstackptr may not always be there, so recompute it */
420 	state = &thread_get_kernel_state(thread)->machine;
421 
422 	stacklimit = VM_MAX_KERNEL_ADDRESS;
423 	stacklimit_bottom = VM_MIN_KERNEL_ADDRESS;
424 #else
425 #error Unknown architecture.
426 #endif
427 
428 	/* Get the frame pointer */
429 	fp = get_saved_state_fp(state);
430 
431 	/* Fill in the current link register */
432 	prevlr = (uint32_t)get_saved_state_lr(state);
433 	pc = get_saved_state_pc(state);
434 	sp = get_saved_state_sp(state);
435 
436 	if (!prevlr && !fp && !sp && !pc) {
437 		return 0;
438 	}
439 
440 	prevlr = (uint32_t)VM_KERNEL_UNSLIDE(prevlr);
441 
442 	for (; framecount < nframes; framecount++) {
443 		*tracebuf++ = prevlr;
444 
445 		/* Invalid frame */
446 		if (!fp) {
447 			break;
448 		}
449 		/* Unaligned frame */
450 		if (fp & 0x0000003) {
451 			break;
452 		}
453 		/* Frame is out of range, maybe a user FP while doing kernel BT */
454 		if (fp > stacklimit) {
455 			break;
456 		}
457 		if (fp < stacklimit_bottom) {
458 			break;
459 		}
460 		/* Stack grows downward */
461 		if (fp < prevfp) {
462 			boolean_t prev_in_interrupt_stack = FALSE;
463 
464 			/*
465 			 * As a special case, sometimes we are backtracing out of an interrupt
466 			 * handler, and the stack jumps downward because of the memory allocation
467 			 * pattern during early boot due to KASLR.
468 			 */
469 			int cpu;
470 			int max_cpu = ml_get_max_cpu_number();
471 
472 			for (cpu = 0; cpu <= max_cpu; cpu++) {
473 				cpu_data_t      *target_cpu_datap;
474 
475 				target_cpu_datap = (cpu_data_t *)CpuDataEntries[cpu].cpu_data_vaddr;
476 				if (target_cpu_datap == (cpu_data_t *)NULL) {
477 					continue;
478 				}
479 
480 				if (prevfp >= (target_cpu_datap->intstack_top - INTSTACK_SIZE) && prevfp < target_cpu_datap->intstack_top) {
481 					prev_in_interrupt_stack = TRUE;
482 					break;
483 				}
484 
485 				if (prevfp >= (target_cpu_datap->fiqstack_top - FIQSTACK_SIZE) && prevfp < target_cpu_datap->fiqstack_top) {
486 					prev_in_interrupt_stack = TRUE;
487 					break;
488 				}
489 			}
490 
491 			if (!prev_in_interrupt_stack) {
492 				/* Corrupt frame pointer? */
493 				break;
494 			}
495 		}
496 		/* Assume there's a saved link register, and read it */
497 		kern_virt_addr = fp + ARM32_LR_OFFSET;
498 		bool ok = machine_trace_thread_validate_kva(kern_virt_addr);
499 		if (!ok) {
500 			if (thread_trace_flags != NULL) {
501 				*thread_trace_flags |= kThreadTruncatedBT;
502 			}
503 			break;
504 		}
505 
506 		prevlr = (uint32_t)VM_KERNEL_UNSLIDE(*(uint32_t *)kern_virt_addr);
507 		prevfp = fp;
508 
509 		/*
510 		 * Next frame; read the fp value into short_fp first
511 		 * as it is 32-bit.
512 		 */
513 		kern_virt_addr = fp;
514 		ok = machine_trace_thread_validate_kva(kern_virt_addr);
515 		if (!ok) {
516 			if (thread_trace_flags != NULL) {
517 				*thread_trace_flags |= kThreadTruncatedBT;
518 			}
519 			fp = 0;
520 			break;
521 		}
522 
523 		short_fp = *(uint32_t *)kern_virt_addr;
524 		fp = (vm_offset_t) short_fp;
525 	}
526 	return (int)(((char *)tracebuf) - tracepos);
527 }
528 
529 #endif // !defined(__arm64__)
530 
531 int
machine_trace_thread64(thread_t thread,char * tracepos,char * tracebound,int nframes,uint32_t * thread_trace_flags)532 machine_trace_thread64(thread_t thread,
533     char * tracepos,
534     char * tracebound,
535     int nframes,
536     uint32_t * thread_trace_flags)
537 {
538 #if defined(__arm__)
539 #pragma unused(thread, tracepos, tracebound, nframes, thread_trace_flags)
540 	return 0;
541 #elif defined(__arm64__)
542 
543 	uint64_t * tracebuf = (uint64_t *)tracepos;
544 	vm_size_t framesize = sizeof(uint64_t);
545 
546 	vm_offset_t stacklimit        = 0;
547 	vm_offset_t stacklimit_bottom = 0;
548 	int framecount                = 0;
549 	vm_offset_t pc                = 0;
550 	vm_offset_t fp                = 0;
551 	vm_offset_t sp                = 0;
552 	vm_offset_t prevfp            = 0;
553 	uint64_t prevlr               = 0;
554 	vm_offset_t kern_virt_addr    = 0;
555 
556 	nframes = (tracebound > tracepos) ? MIN(nframes, (int)((tracebound - tracepos) / framesize)) : 0;
557 	if (!nframes) {
558 		return 0;
559 	}
560 	framecount = 0;
561 
562 	struct arm_saved_state *state = thread->machine.kpcb;
563 	if (state != NULL) {
564 		fp = state->ss_64.fp;
565 
566 		prevlr = state->ss_64.lr;
567 		pc = state->ss_64.pc;
568 		sp = state->ss_64.sp;
569 	} else {
570 		/* kstackptr may not always be there, so recompute it */
571 		arm_kernel_saved_state_t *kstate = &thread_get_kernel_state(thread)->machine.ss;
572 
573 		fp = kstate->fp;
574 		prevlr = kstate->lr;
575 		pc = kstate->pc;
576 		sp = kstate->sp;
577 	}
578 
579 	stacklimit = VM_MAX_KERNEL_ADDRESS;
580 	stacklimit_bottom = VM_MIN_KERNEL_ADDRESS;
581 
582 	if (!prevlr && !fp && !sp && !pc) {
583 		return 0;
584 	}
585 
586 	prevlr = VM_KERNEL_UNSLIDE(prevlr);
587 
588 	for (; framecount < nframes; framecount++) {
589 		*tracebuf++ = prevlr;
590 
591 		/* Invalid frame */
592 		if (!fp) {
593 			break;
594 		}
595 		/*
596 		 * Unaligned frame; given that the stack register must always be
597 		 * 16-byte aligned, we are assured 8-byte alignment of the saved
598 		 * frame pointer and link register.
599 		 */
600 		if (fp & 0x0000007) {
601 			break;
602 		}
603 		/* Frame is out of range, maybe a user FP while doing kernel BT */
604 		if (fp > stacklimit) {
605 			break;
606 		}
607 		if (fp < stacklimit_bottom) {
608 			break;
609 		}
610 		/* Stack grows downward */
611 		if (fp < prevfp) {
612 			bool switched_stacks = false;
613 
614 			/*
615 			 * As a special case, sometimes we are backtracing out of an interrupt
616 			 * handler, and the stack jumps downward because of the memory allocation
617 			 * pattern during early boot due to KASLR.
618 			 */
619 			int cpu;
620 			int max_cpu = ml_get_max_cpu_number();
621 
622 			for (cpu = 0; cpu <= max_cpu; cpu++) {
623 				cpu_data_t      *target_cpu_datap;
624 
625 				target_cpu_datap = (cpu_data_t *)CpuDataEntries[cpu].cpu_data_vaddr;
626 				if (target_cpu_datap == (cpu_data_t *)NULL) {
627 					continue;
628 				}
629 
630 				if (prevfp >= (target_cpu_datap->intstack_top - INTSTACK_SIZE) && prevfp < target_cpu_datap->intstack_top) {
631 					switched_stacks = true;
632 					break;
633 				}
634 #if defined(__arm__)
635 				if (prevfp >= (target_cpu_datap->fiqstack_top - FIQSTACK_SIZE) && prevfp < target_cpu_datap->fiqstack_top) {
636 					switched_stacks = true;
637 					break;
638 				}
639 #elif defined(__arm64__)
640 				if (prevfp >= (target_cpu_datap->excepstack_top - EXCEPSTACK_SIZE) && prevfp < target_cpu_datap->excepstack_top) {
641 					switched_stacks = true;
642 					break;
643 				}
644 #endif
645 			}
646 
647 #if XNU_MONITOR
648 			vm_offset_t cpu_base = (vm_offset_t)pmap_stacks_start;
649 			vm_offset_t cpu_top = (vm_offset_t)pmap_stacks_end;
650 
651 			if (((prevfp >= cpu_base) && (prevfp < cpu_top)) !=
652 			    ((fp >= cpu_base) && (fp < cpu_top))) {
653 				switched_stacks = true;
654 				break;
655 			}
656 #endif
657 
658 			if (!switched_stacks) {
659 				/* Corrupt frame pointer? */
660 				break;
661 			}
662 		}
663 
664 		/* Assume there's a saved link register, and read it */
665 		kern_virt_addr = fp + ARM64_LR_OFFSET;
666 		bool ok = machine_trace_thread_validate_kva(kern_virt_addr);
667 		if (!ok) {
668 			if (thread_trace_flags != NULL) {
669 				*thread_trace_flags |= kThreadTruncatedBT;
670 			}
671 			break;
672 		}
673 
674 		prevlr = *(uint64_t *)kern_virt_addr;
675 #if defined(HAS_APPLE_PAC)
676 		/* return addresses on stack signed by arm64e ABI */
677 		prevlr = (uint64_t) ptrauth_strip((void *)prevlr, ptrauth_key_return_address);
678 #endif
679 		prevlr = VM_KERNEL_UNSLIDE(prevlr);
680 
681 		prevfp = fp;
682 		/* Next frame */
683 		kern_virt_addr = fp;
684 		ok = machine_trace_thread_validate_kva(kern_virt_addr);
685 		if (!ok) {
686 			if (thread_trace_flags != NULL) {
687 				*thread_trace_flags |= kThreadTruncatedBT;
688 			}
689 			fp = 0;
690 			break;
691 		}
692 
693 		fp = *(uint64_t *)kern_virt_addr;
694 	}
695 	return (int)(((char *)tracebuf) - tracepos);
696 #else
697 #error Unknown architecture.
698 #endif
699 }
700 
701 void
kdp_ml_enter_debugger(void)702 kdp_ml_enter_debugger(void)
703 {
704 	__asm__ volatile (".long 0xe7ffdefe");
705 }
706