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1/*
2 * Kernel Debug Core
3 *
4 * Maintainer: Jason Wessel <jason.wessel@windriver.com>
5 *
6 * Copyright (C) 2000-2001 VERITAS Software Corporation.
7 * Copyright (C) 2002-2004 Timesys Corporation
8 * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
9 * Copyright (C) 2004 Pavel Machek <pavel@ucw.cz>
10 * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
11 * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
12 * Copyright (C) 2005-2009 Wind River Systems, Inc.
13 * Copyright (C) 2007 MontaVista Software, Inc.
14 * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
15 *
16 * Contributors at various stages not listed above:
17 * Jason Wessel ( jason.wessel@windriver.com )
18 * George Anzinger <george@mvista.com>
19 * Anurekh Saxena (anurekh.saxena@timesys.com)
20 * Lake Stevens Instrument Division (Glenn Engel)
21 * Jim Kingdon, Cygnus Support.
22 *
23 * Original KGDB stub: David Grothe <dave@gcom.com>,
24 * Tigran Aivazian <tigran@sco.com>
25 *
26 * This file is licensed under the terms of the GNU General Public License
27 * version 2. This program is licensed "as is" without any warranty of any
28 * kind, whether express or implied.
29 */
30
31#define pr_fmt(fmt) "KGDB: " fmt
32
33#include <linux/pid_namespace.h>
34#include <linux/clocksource.h>
35#include <linux/serial_core.h>
36#include <linux/interrupt.h>
37#include <linux/spinlock.h>
38#include <linux/console.h>
39#include <linux/threads.h>
40#include <linux/uaccess.h>
41#include <linux/kernel.h>
42#include <linux/module.h>
43#include <linux/ptrace.h>
44#include <linux/string.h>
45#include <linux/delay.h>
46#include <linux/sched.h>
47#include <linux/sysrq.h>
48#include <linux/reboot.h>
49#include <linux/init.h>
50#include <linux/kgdb.h>
51#include <linux/kdb.h>
52#include <linux/pid.h>
53#include <linux/smp.h>
54#include <linux/mm.h>
55#include <linux/vmacache.h>
56#include <linux/rcupdate.h>
57
58#include <asm/cacheflush.h>
59#include <asm/byteorder.h>
60#include <linux/atomic.h>
61
62#include "debug_core.h"
63
64static int kgdb_break_asap;
65
66struct debuggerinfo_struct kgdb_info[NR_CPUS];
67
68/**
69 * kgdb_connected - Is a host GDB connected to us?
70 */
71int kgdb_connected;
72EXPORT_SYMBOL_GPL(kgdb_connected);
73
74/* All the KGDB handlers are installed */
75int kgdb_io_module_registered;
76
77/* Guard for recursive entry */
78static int exception_level;
79
80struct kgdb_io *dbg_io_ops;
81static DEFINE_SPINLOCK(kgdb_registration_lock);
82
83/* Action for the reboot notifiter, a global allow kdb to change it */
84static int kgdbreboot;
85/* kgdb console driver is loaded */
86static int kgdb_con_registered;
87/* determine if kgdb console output should be used */
88static int kgdb_use_con;
89/* Flag for alternate operations for early debugging */
90bool dbg_is_early = true;
91/* Next cpu to become the master debug core */
92int dbg_switch_cpu;
93
94/* Use kdb or gdbserver mode */
95int dbg_kdb_mode = 1;
96
97static int __init opt_kgdb_con(char *str)
98{
99 kgdb_use_con = 1;
100 return 0;
101}
102
103early_param("kgdbcon", opt_kgdb_con);
104
105module_param(kgdb_use_con, int, 0644);
106module_param(kgdbreboot, int, 0644);
107
108/*
109 * Holds information about breakpoints in a kernel. These breakpoints are
110 * added and removed by gdb.
111 */
112static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
113 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
114};
115
116/*
117 * The CPU# of the active CPU, or -1 if none:
118 */
119atomic_t kgdb_active = ATOMIC_INIT(-1);
120EXPORT_SYMBOL_GPL(kgdb_active);
121static DEFINE_RAW_SPINLOCK(dbg_master_lock);
122static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
123
124/*
125 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
126 * bootup code (which might not have percpu set up yet):
127 */
128static atomic_t masters_in_kgdb;
129static atomic_t slaves_in_kgdb;
130static atomic_t kgdb_break_tasklet_var;
131atomic_t kgdb_setting_breakpoint;
132
133struct task_struct *kgdb_usethread;
134struct task_struct *kgdb_contthread;
135
136int kgdb_single_step;
137static pid_t kgdb_sstep_pid;
138
139/* to keep track of the CPU which is doing the single stepping*/
140atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
141
142/*
143 * If you are debugging a problem where roundup (the collection of
144 * all other CPUs) is a problem [this should be extremely rare],
145 * then use the nokgdbroundup option to avoid roundup. In that case
146 * the other CPUs might interfere with your debugging context, so
147 * use this with care:
148 */
149static int kgdb_do_roundup = 1;
150
151static int __init opt_nokgdbroundup(char *str)
152{
153 kgdb_do_roundup = 0;
154
155 return 0;
156}
157
158early_param("nokgdbroundup", opt_nokgdbroundup);
159
160/*
161 * Finally, some KGDB code :-)
162 */
163
164/*
165 * Weak aliases for breakpoint management,
166 * can be overriden by architectures when needed:
167 */
168int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
169{
170 int err;
171
172 err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
173 BREAK_INSTR_SIZE);
174 if (err)
175 return err;
176 err = probe_kernel_write((char *)bpt->bpt_addr,
177 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
178 return err;
179}
180
181int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
182{
183 return probe_kernel_write((char *)bpt->bpt_addr,
184 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
185}
186
187int __weak kgdb_validate_break_address(unsigned long addr)
188{
189 struct kgdb_bkpt tmp;
190 int err;
191 /* Validate setting the breakpoint and then removing it. If the
192 * remove fails, the kernel needs to emit a bad message because we
193 * are deep trouble not being able to put things back the way we
194 * found them.
195 */
196 tmp.bpt_addr = addr;
197 err = kgdb_arch_set_breakpoint(&tmp);
198 if (err)
199 return err;
200 err = kgdb_arch_remove_breakpoint(&tmp);
201 if (err)
202 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
203 addr);
204 return err;
205}
206
207unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
208{
209 return instruction_pointer(regs);
210}
211
212int __weak kgdb_arch_init(void)
213{
214 return 0;
215}
216
217int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
218{
219 return 0;
220}
221
222/*
223 * Some architectures need cache flushes when we set/clear a
224 * breakpoint:
225 */
226static void kgdb_flush_swbreak_addr(unsigned long addr)
227{
228 if (!CACHE_FLUSH_IS_SAFE)
229 return;
230
231 if (current->mm) {
232 int i;
233
234 for (i = 0; i < VMACACHE_SIZE; i++) {
235 if (!current->vmacache[i])
236 continue;
237 flush_cache_range(current->vmacache[i],
238 addr, addr + BREAK_INSTR_SIZE);
239 }
240 }
241
242 /* Force flush instruction cache if it was outside the mm */
243 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
244}
245
246/*
247 * SW breakpoint management:
248 */
249int dbg_activate_sw_breakpoints(void)
250{
251 int error;
252 int ret = 0;
253 int i;
254
255 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
256 if (kgdb_break[i].state != BP_SET)
257 continue;
258
259 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
260 if (error) {
261 ret = error;
262 pr_info("BP install failed: %lx\n",
263 kgdb_break[i].bpt_addr);
264 continue;
265 }
266
267 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
268 kgdb_break[i].state = BP_ACTIVE;
269 }
270 return ret;
271}
272
273int dbg_set_sw_break(unsigned long addr)
274{
275 int err = kgdb_validate_break_address(addr);
276 int breakno = -1;
277 int i;
278
279 if (err)
280 return err;
281
282 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
283 if ((kgdb_break[i].state == BP_SET) &&
284 (kgdb_break[i].bpt_addr == addr))
285 return -EEXIST;
286 }
287 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
288 if (kgdb_break[i].state == BP_REMOVED &&
289 kgdb_break[i].bpt_addr == addr) {
290 breakno = i;
291 break;
292 }
293 }
294
295 if (breakno == -1) {
296 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
297 if (kgdb_break[i].state == BP_UNDEFINED) {
298 breakno = i;
299 break;
300 }
301 }
302 }
303
304 if (breakno == -1)
305 return -E2BIG;
306
307 kgdb_break[breakno].state = BP_SET;
308 kgdb_break[breakno].type = BP_BREAKPOINT;
309 kgdb_break[breakno].bpt_addr = addr;
310
311 return 0;
312}
313
314int dbg_deactivate_sw_breakpoints(void)
315{
316 int error;
317 int ret = 0;
318 int i;
319
320 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
321 if (kgdb_break[i].state != BP_ACTIVE)
322 continue;
323 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
324 if (error) {
325 pr_info("BP remove failed: %lx\n",
326 kgdb_break[i].bpt_addr);
327 ret = error;
328 }
329
330 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
331 kgdb_break[i].state = BP_SET;
332 }
333 return ret;
334}
335
336int dbg_remove_sw_break(unsigned long addr)
337{
338 int i;
339
340 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
341 if ((kgdb_break[i].state == BP_SET) &&
342 (kgdb_break[i].bpt_addr == addr)) {
343 kgdb_break[i].state = BP_REMOVED;
344 return 0;
345 }
346 }
347 return -ENOENT;
348}
349
350int kgdb_isremovedbreak(unsigned long addr)
351{
352 int i;
353
354 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
355 if ((kgdb_break[i].state == BP_REMOVED) &&
356 (kgdb_break[i].bpt_addr == addr))
357 return 1;
358 }
359 return 0;
360}
361
362int dbg_remove_all_break(void)
363{
364 int error;
365 int i;
366
367 /* Clear memory breakpoints. */
368 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
369 if (kgdb_break[i].state != BP_ACTIVE)
370 goto setundefined;
371 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
372 if (error)
373 pr_err("breakpoint remove failed: %lx\n",
374 kgdb_break[i].bpt_addr);
375setundefined:
376 kgdb_break[i].state = BP_UNDEFINED;
377 }
378
379 /* Clear hardware breakpoints. */
380 if (arch_kgdb_ops.remove_all_hw_break)
381 arch_kgdb_ops.remove_all_hw_break();
382
383 return 0;
384}
385
386/*
387 * Return true if there is a valid kgdb I/O module. Also if no
388 * debugger is attached a message can be printed to the console about
389 * waiting for the debugger to attach.
390 *
391 * The print_wait argument is only to be true when called from inside
392 * the core kgdb_handle_exception, because it will wait for the
393 * debugger to attach.
394 */
395static int kgdb_io_ready(int print_wait)
396{
397 if (!dbg_io_ops)
398 return 0;
399 if (kgdb_connected)
400 return 1;
401 if (atomic_read(&kgdb_setting_breakpoint))
402 return 1;
403 if (print_wait) {
404#ifdef CONFIG_KGDB_KDB
405 if (!dbg_kdb_mode)
406 pr_crit("waiting... or $3#33 for KDB\n");
407#else
408 pr_crit("Waiting for remote debugger\n");
409#endif
410 }
411 return 1;
412}
413
414static int kgdb_reenter_check(struct kgdb_state *ks)
415{
416 unsigned long addr;
417
418 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
419 return 0;
420
421 /* Panic on recursive debugger calls: */
422 exception_level++;
423 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
424 dbg_deactivate_sw_breakpoints();
425
426 /*
427 * If the break point removed ok at the place exception
428 * occurred, try to recover and print a warning to the end
429 * user because the user planted a breakpoint in a place that
430 * KGDB needs in order to function.
431 */
432 if (dbg_remove_sw_break(addr) == 0) {
433 exception_level = 0;
434 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
435 dbg_activate_sw_breakpoints();
436 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
437 WARN_ON_ONCE(1);
438
439 return 1;
440 }
441 dbg_remove_all_break();
442 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
443
444 if (exception_level > 1) {
445 dump_stack();
446 panic("Recursive entry to debugger");
447 }
448
449 pr_crit("re-enter exception: ALL breakpoints killed\n");
450#ifdef CONFIG_KGDB_KDB
451 /* Allow kdb to debug itself one level */
452 return 0;
453#endif
454 dump_stack();
455 panic("Recursive entry to debugger");
456
457 return 1;
458}
459
460static void dbg_touch_watchdogs(void)
461{
462 touch_softlockup_watchdog_sync();
463 clocksource_touch_watchdog();
464 rcu_cpu_stall_reset();
465}
466
467static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
468 int exception_state)
469{
470 unsigned long flags;
471 int sstep_tries = 100;
472 int error;
473 int cpu;
474 int trace_on = 0;
475 int online_cpus = num_online_cpus();
476 u64 time_left;
477
478 kgdb_info[ks->cpu].enter_kgdb++;
479 kgdb_info[ks->cpu].exception_state |= exception_state;
480
481 if (exception_state == DCPU_WANT_MASTER)
482 atomic_inc(&masters_in_kgdb);
483 else
484 atomic_inc(&slaves_in_kgdb);
485
486 if (arch_kgdb_ops.disable_hw_break)
487 arch_kgdb_ops.disable_hw_break(regs);
488
489acquirelock:
490 /*
491 * Interrupts will be restored by the 'trap return' code, except when
492 * single stepping.
493 */
494 local_irq_save(flags);
495
496 cpu = ks->cpu;
497 kgdb_info[cpu].debuggerinfo = regs;
498 kgdb_info[cpu].task = current;
499 kgdb_info[cpu].ret_state = 0;
500 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
501
502 /* Make sure the above info reaches the primary CPU */
503 smp_mb();
504
505 if (exception_level == 1) {
506 if (raw_spin_trylock(&dbg_master_lock))
507 atomic_xchg(&kgdb_active, cpu);
508 goto cpu_master_loop;
509 }
510
511 /*
512 * CPU will loop if it is a slave or request to become a kgdb
513 * master cpu and acquire the kgdb_active lock:
514 */
515 while (1) {
516cpu_loop:
517 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
518 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
519 goto cpu_master_loop;
520 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
521 if (raw_spin_trylock(&dbg_master_lock)) {
522 atomic_xchg(&kgdb_active, cpu);
523 break;
524 }
525 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
526 if (!raw_spin_is_locked(&dbg_slave_lock))
527 goto return_normal;
528 } else {
529return_normal:
530 /* Return to normal operation by executing any
531 * hw breakpoint fixup.
532 */
533 if (arch_kgdb_ops.correct_hw_break)
534 arch_kgdb_ops.correct_hw_break();
535 if (trace_on)
536 tracing_on();
537 kgdb_info[cpu].exception_state &=
538 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
539 kgdb_info[cpu].enter_kgdb--;
540 smp_mb__before_atomic();
541 atomic_dec(&slaves_in_kgdb);
542 dbg_touch_watchdogs();
543 local_irq_restore(flags);
544 return 0;
545 }
546 cpu_relax();
547 }
548
549 /*
550 * For single stepping, try to only enter on the processor
551 * that was single stepping. To guard against a deadlock, the
552 * kernel will only try for the value of sstep_tries before
553 * giving up and continuing on.
554 */
555 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
556 (kgdb_info[cpu].task &&
557 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
558 atomic_set(&kgdb_active, -1);
559 raw_spin_unlock(&dbg_master_lock);
560 dbg_touch_watchdogs();
561 local_irq_restore(flags);
562
563 goto acquirelock;
564 }
565
566 if (!kgdb_io_ready(1)) {
567 kgdb_info[cpu].ret_state = 1;
568 goto kgdb_restore; /* No I/O connection, resume the system */
569 }
570
571 /*
572 * Don't enter if we have hit a removed breakpoint.
573 */
574 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
575 goto kgdb_restore;
576
577 /* Call the I/O driver's pre_exception routine */
578 if (dbg_io_ops->pre_exception)
579 dbg_io_ops->pre_exception();
580
581 /*
582 * Get the passive CPU lock which will hold all the non-primary
583 * CPU in a spin state while the debugger is active
584 */
585 if (!kgdb_single_step)
586 raw_spin_lock(&dbg_slave_lock);
587
588#ifdef CONFIG_SMP
589 /* If send_ready set, slaves are already waiting */
590 if (ks->send_ready)
591 atomic_set(ks->send_ready, 1);
592
593 /* Signal the other CPUs to enter kgdb_wait() */
594 else if ((!kgdb_single_step) && kgdb_do_roundup)
595 kgdb_roundup_cpus(flags);
596#endif
597
598 /*
599 * Wait for the other CPUs to be notified and be waiting for us:
600 */
601 time_left = MSEC_PER_SEC;
602 while (kgdb_do_roundup && --time_left &&
603 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
604 online_cpus)
605 udelay(1000);
606 if (!time_left)
607 pr_crit("Timed out waiting for secondary CPUs.\n");
608
609 /*
610 * At this point the primary processor is completely
611 * in the debugger and all secondary CPUs are quiescent
612 */
613 dbg_deactivate_sw_breakpoints();
614 kgdb_single_step = 0;
615 kgdb_contthread = current;
616 exception_level = 0;
617 trace_on = tracing_is_on();
618 if (trace_on)
619 tracing_off();
620
621 while (1) {
622cpu_master_loop:
623 if (dbg_kdb_mode) {
624 kgdb_connected = 1;
625 error = kdb_stub(ks);
626 if (error == -1)
627 continue;
628 kgdb_connected = 0;
629 } else {
630 error = gdb_serial_stub(ks);
631 }
632
633 if (error == DBG_PASS_EVENT) {
634 dbg_kdb_mode = !dbg_kdb_mode;
635 } else if (error == DBG_SWITCH_CPU_EVENT) {
636 kgdb_info[dbg_switch_cpu].exception_state |=
637 DCPU_NEXT_MASTER;
638 goto cpu_loop;
639 } else {
640 kgdb_info[cpu].ret_state = error;
641 break;
642 }
643 }
644
645 /* Call the I/O driver's post_exception routine */
646 if (dbg_io_ops->post_exception)
647 dbg_io_ops->post_exception();
648
649 if (!kgdb_single_step) {
650 raw_spin_unlock(&dbg_slave_lock);
651 /* Wait till all the CPUs have quit from the debugger. */
652 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
653 cpu_relax();
654 }
655
656kgdb_restore:
657 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
658 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
659 if (kgdb_info[sstep_cpu].task)
660 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
661 else
662 kgdb_sstep_pid = 0;
663 }
664 if (arch_kgdb_ops.correct_hw_break)
665 arch_kgdb_ops.correct_hw_break();
666 if (trace_on)
667 tracing_on();
668
669 kgdb_info[cpu].exception_state &=
670 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
671 kgdb_info[cpu].enter_kgdb--;
672 smp_mb__before_atomic();
673 atomic_dec(&masters_in_kgdb);
674 /* Free kgdb_active */
675 atomic_set(&kgdb_active, -1);
676 raw_spin_unlock(&dbg_master_lock);
677 dbg_touch_watchdogs();
678 local_irq_restore(flags);
679
680 return kgdb_info[cpu].ret_state;
681}
682
683/*
684 * kgdb_handle_exception() - main entry point from a kernel exception
685 *
686 * Locking hierarchy:
687 * interface locks, if any (begin_session)
688 * kgdb lock (kgdb_active)
689 */
690int
691kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
692{
693 struct kgdb_state kgdb_var;
694 struct kgdb_state *ks = &kgdb_var;
695 int ret = 0;
696
697 if (arch_kgdb_ops.enable_nmi)
698 arch_kgdb_ops.enable_nmi(0);
699 /*
700 * Avoid entering the debugger if we were triggered due to an oops
701 * but panic_timeout indicates the system should automatically
702 * reboot on panic. We don't want to get stuck waiting for input
703 * on such systems, especially if its "just" an oops.
704 */
705 if (signo != SIGTRAP && panic_timeout)
706 return 1;
707
708 memset(ks, 0, sizeof(struct kgdb_state));
709 ks->cpu = raw_smp_processor_id();
710 ks->ex_vector = evector;
711 ks->signo = signo;
712 ks->err_code = ecode;
713 ks->linux_regs = regs;
714
715 if (kgdb_reenter_check(ks))
716 goto out; /* Ouch, double exception ! */
717 if (kgdb_info[ks->cpu].enter_kgdb != 0)
718 goto out;
719
720 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
721out:
722 if (arch_kgdb_ops.enable_nmi)
723 arch_kgdb_ops.enable_nmi(1);
724 return ret;
725}
726
727/*
728 * GDB places a breakpoint at this function to know dynamically
729 * loaded objects. It's not defined static so that only one instance with this
730 * name exists in the kernel.
731 */
732
733static int module_event(struct notifier_block *self, unsigned long val,
734 void *data)
735{
736 return 0;
737}
738
739static struct notifier_block dbg_module_load_nb = {
740 .notifier_call = module_event,
741};
742
743int kgdb_nmicallback(int cpu, void *regs)
744{
745#ifdef CONFIG_SMP
746 struct kgdb_state kgdb_var;
747 struct kgdb_state *ks = &kgdb_var;
748
749 memset(ks, 0, sizeof(struct kgdb_state));
750 ks->cpu = cpu;
751 ks->linux_regs = regs;
752
753 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
754 raw_spin_is_locked(&dbg_master_lock)) {
755 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
756 return 0;
757 }
758#endif
759 return 1;
760}
761
762int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
763 atomic_t *send_ready)
764{
765#ifdef CONFIG_SMP
766 if (!kgdb_io_ready(0) || !send_ready)
767 return 1;
768
769 if (kgdb_info[cpu].enter_kgdb == 0) {
770 struct kgdb_state kgdb_var;
771 struct kgdb_state *ks = &kgdb_var;
772
773 memset(ks, 0, sizeof(struct kgdb_state));
774 ks->cpu = cpu;
775 ks->ex_vector = trapnr;
776 ks->signo = SIGTRAP;
777 ks->err_code = err_code;
778 ks->linux_regs = regs;
779 ks->send_ready = send_ready;
780 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
781 return 0;
782 }
783#endif
784 return 1;
785}
786
787static void kgdb_console_write(struct console *co, const char *s,
788 unsigned count)
789{
790 unsigned long flags;
791
792 /* If we're debugging, or KGDB has not connected, don't try
793 * and print. */
794 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
795 return;
796
797 local_irq_save(flags);
798 gdbstub_msg_write(s, count);
799 local_irq_restore(flags);
800}
801
802static struct console kgdbcons = {
803 .name = "kgdb",
804 .write = kgdb_console_write,
805 .flags = CON_PRINTBUFFER | CON_ENABLED,
806 .index = -1,
807};
808
809#ifdef CONFIG_MAGIC_SYSRQ
810static void sysrq_handle_dbg(int key)
811{
812 if (!dbg_io_ops) {
813 pr_crit("ERROR: No KGDB I/O module available\n");
814 return;
815 }
816 if (!kgdb_connected) {
817#ifdef CONFIG_KGDB_KDB
818 if (!dbg_kdb_mode)
819 pr_crit("KGDB or $3#33 for KDB\n");
820#else
821 pr_crit("Entering KGDB\n");
822#endif
823 }
824
825 kgdb_breakpoint();
826}
827
828static struct sysrq_key_op sysrq_dbg_op = {
829 .handler = sysrq_handle_dbg,
830 .help_msg = "debug(g)",
831 .action_msg = "DEBUG",
832};
833#endif
834
835static int kgdb_panic_event(struct notifier_block *self,
836 unsigned long val,
837 void *data)
838{
839 /*
840 * Avoid entering the debugger if we were triggered due to a panic
841 * We don't want to get stuck waiting for input from user in such case.
842 * panic_timeout indicates the system should automatically
843 * reboot on panic.
844 */
845 if (panic_timeout)
846 return NOTIFY_DONE;
847
848 if (dbg_kdb_mode)
849 kdb_printf("PANIC: %s\n", (char *)data);
850 kgdb_breakpoint();
851 return NOTIFY_DONE;
852}
853
854static struct notifier_block kgdb_panic_event_nb = {
855 .notifier_call = kgdb_panic_event,
856 .priority = INT_MAX,
857};
858
859void __weak kgdb_arch_late(void)
860{
861}
862
863void __init dbg_late_init(void)
864{
865 dbg_is_early = false;
866 if (kgdb_io_module_registered)
867 kgdb_arch_late();
868 kdb_init(KDB_INIT_FULL);
869}
870
871static int
872dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
873{
874 /*
875 * Take the following action on reboot notify depending on value:
876 * 1 == Enter debugger
877 * 0 == [the default] detatch debug client
878 * -1 == Do nothing... and use this until the board resets
879 */
880 switch (kgdbreboot) {
881 case 1:
882 kgdb_breakpoint();
883 case -1:
884 goto done;
885 }
886 if (!dbg_kdb_mode)
887 gdbstub_exit(code);
888done:
889 return NOTIFY_DONE;
890}
891
892static struct notifier_block dbg_reboot_notifier = {
893 .notifier_call = dbg_notify_reboot,
894 .next = NULL,
895 .priority = INT_MAX,
896};
897
898static void kgdb_register_callbacks(void)
899{
900 if (!kgdb_io_module_registered) {
901 kgdb_io_module_registered = 1;
902 kgdb_arch_init();
903 if (!dbg_is_early)
904 kgdb_arch_late();
905 register_module_notifier(&dbg_module_load_nb);
906 register_reboot_notifier(&dbg_reboot_notifier);
907 atomic_notifier_chain_register(&panic_notifier_list,
908 &kgdb_panic_event_nb);
909#ifdef CONFIG_MAGIC_SYSRQ
910 register_sysrq_key('g', &sysrq_dbg_op);
911#endif
912 if (kgdb_use_con && !kgdb_con_registered) {
913 register_console(&kgdbcons);
914 kgdb_con_registered = 1;
915 }
916 }
917}
918
919static void kgdb_unregister_callbacks(void)
920{
921 /*
922 * When this routine is called KGDB should unregister from the
923 * panic handler and clean up, making sure it is not handling any
924 * break exceptions at the time.
925 */
926 if (kgdb_io_module_registered) {
927 kgdb_io_module_registered = 0;
928 unregister_reboot_notifier(&dbg_reboot_notifier);
929 unregister_module_notifier(&dbg_module_load_nb);
930 atomic_notifier_chain_unregister(&panic_notifier_list,
931 &kgdb_panic_event_nb);
932 kgdb_arch_exit();
933#ifdef CONFIG_MAGIC_SYSRQ
934 unregister_sysrq_key('g', &sysrq_dbg_op);
935#endif
936 if (kgdb_con_registered) {
937 unregister_console(&kgdbcons);
938 kgdb_con_registered = 0;
939 }
940 }
941}
942
943/*
944 * There are times a tasklet needs to be used vs a compiled in
945 * break point so as to cause an exception outside a kgdb I/O module,
946 * such as is the case with kgdboe, where calling a breakpoint in the
947 * I/O driver itself would be fatal.
948 */
949static void kgdb_tasklet_bpt(unsigned long ing)
950{
951 kgdb_breakpoint();
952 atomic_set(&kgdb_break_tasklet_var, 0);
953}
954
955static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
956
957void kgdb_schedule_breakpoint(void)
958{
959 if (atomic_read(&kgdb_break_tasklet_var) ||
960 atomic_read(&kgdb_active) != -1 ||
961 atomic_read(&kgdb_setting_breakpoint))
962 return;
963 atomic_inc(&kgdb_break_tasklet_var);
964 tasklet_schedule(&kgdb_tasklet_breakpoint);
965}
966EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
967
968static void kgdb_initial_breakpoint(void)
969{
970 kgdb_break_asap = 0;
971
972 pr_crit("Waiting for connection from remote gdb...\n");
973 kgdb_breakpoint();
974}
975
976/**
977 * kgdb_register_io_module - register KGDB IO module
978 * @new_dbg_io_ops: the io ops vector
979 *
980 * Register it with the KGDB core.
981 */
982int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
983{
984 int err;
985
986 spin_lock(&kgdb_registration_lock);
987
988 if (dbg_io_ops) {
989 spin_unlock(&kgdb_registration_lock);
990
991 pr_err("Another I/O driver is already registered with KGDB\n");
992 return -EBUSY;
993 }
994
995 if (new_dbg_io_ops->init) {
996 err = new_dbg_io_ops->init();
997 if (err) {
998 spin_unlock(&kgdb_registration_lock);
999 return err;
1000 }
1001 }
1002
1003 dbg_io_ops = new_dbg_io_ops;
1004
1005 spin_unlock(&kgdb_registration_lock);
1006
1007 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1008
1009 /* Arm KGDB now. */
1010 kgdb_register_callbacks();
1011
1012 if (kgdb_break_asap)
1013 kgdb_initial_breakpoint();
1014
1015 return 0;
1016}
1017EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1018
1019/**
1020 * kkgdb_unregister_io_module - unregister KGDB IO module
1021 * @old_dbg_io_ops: the io ops vector
1022 *
1023 * Unregister it with the KGDB core.
1024 */
1025void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1026{
1027 BUG_ON(kgdb_connected);
1028
1029 /*
1030 * KGDB is no longer able to communicate out, so
1031 * unregister our callbacks and reset state.
1032 */
1033 kgdb_unregister_callbacks();
1034
1035 spin_lock(&kgdb_registration_lock);
1036
1037 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1038 dbg_io_ops = NULL;
1039
1040 spin_unlock(&kgdb_registration_lock);
1041
1042 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1043 old_dbg_io_ops->name);
1044}
1045EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1046
1047int dbg_io_get_char(void)
1048{
1049 int ret = dbg_io_ops->read_char();
1050 if (ret == NO_POLL_CHAR)
1051 return -1;
1052 if (!dbg_kdb_mode)
1053 return ret;
1054 if (ret == 127)
1055 return 8;
1056 return ret;
1057}
1058
1059/**
1060 * kgdb_breakpoint - generate breakpoint exception
1061 *
1062 * This function will generate a breakpoint exception. It is used at the
1063 * beginning of a program to sync up with a debugger and can be used
1064 * otherwise as a quick means to stop program execution and "break" into
1065 * the debugger.
1066 */
1067noinline void kgdb_breakpoint(void)
1068{
1069 atomic_inc(&kgdb_setting_breakpoint);
1070 wmb(); /* Sync point before breakpoint */
1071 arch_kgdb_breakpoint();
1072 wmb(); /* Sync point after breakpoint */
1073 atomic_dec(&kgdb_setting_breakpoint);
1074}
1075EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1076
1077static int __init opt_kgdb_wait(char *str)
1078{
1079 kgdb_break_asap = 1;
1080
1081 kdb_init(KDB_INIT_EARLY);
1082 if (kgdb_io_module_registered)
1083 kgdb_initial_breakpoint();
1084
1085 return 0;
1086}
1087
1088early_param("kgdbwait", opt_kgdb_wait);
1/*
2 * Kernel Debug Core
3 *
4 * Maintainer: Jason Wessel <jason.wessel@windriver.com>
5 *
6 * Copyright (C) 2000-2001 VERITAS Software Corporation.
7 * Copyright (C) 2002-2004 Timesys Corporation
8 * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
9 * Copyright (C) 2004 Pavel Machek <pavel@ucw.cz>
10 * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
11 * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
12 * Copyright (C) 2005-2009 Wind River Systems, Inc.
13 * Copyright (C) 2007 MontaVista Software, Inc.
14 * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
15 *
16 * Contributors at various stages not listed above:
17 * Jason Wessel ( jason.wessel@windriver.com )
18 * George Anzinger <george@mvista.com>
19 * Anurekh Saxena (anurekh.saxena@timesys.com)
20 * Lake Stevens Instrument Division (Glenn Engel)
21 * Jim Kingdon, Cygnus Support.
22 *
23 * Original KGDB stub: David Grothe <dave@gcom.com>,
24 * Tigran Aivazian <tigran@sco.com>
25 *
26 * This file is licensed under the terms of the GNU General Public License
27 * version 2. This program is licensed "as is" without any warranty of any
28 * kind, whether express or implied.
29 */
30
31#define pr_fmt(fmt) "KGDB: " fmt
32
33#include <linux/pid_namespace.h>
34#include <linux/clocksource.h>
35#include <linux/serial_core.h>
36#include <linux/interrupt.h>
37#include <linux/spinlock.h>
38#include <linux/console.h>
39#include <linux/threads.h>
40#include <linux/uaccess.h>
41#include <linux/kernel.h>
42#include <linux/module.h>
43#include <linux/ptrace.h>
44#include <linux/string.h>
45#include <linux/delay.h>
46#include <linux/sched.h>
47#include <linux/sysrq.h>
48#include <linux/reboot.h>
49#include <linux/init.h>
50#include <linux/kgdb.h>
51#include <linux/kdb.h>
52#include <linux/nmi.h>
53#include <linux/pid.h>
54#include <linux/smp.h>
55#include <linux/mm.h>
56#include <linux/vmacache.h>
57#include <linux/rcupdate.h>
58#include <linux/irq.h>
59
60#include <asm/cacheflush.h>
61#include <asm/byteorder.h>
62#include <linux/atomic.h>
63
64#include "debug_core.h"
65
66static int kgdb_break_asap;
67
68struct debuggerinfo_struct kgdb_info[NR_CPUS];
69
70/* kgdb_connected - Is a host GDB connected to us? */
71int kgdb_connected;
72EXPORT_SYMBOL_GPL(kgdb_connected);
73
74/* All the KGDB handlers are installed */
75int kgdb_io_module_registered;
76
77/* Guard for recursive entry */
78static int exception_level;
79
80struct kgdb_io *dbg_io_ops;
81static DEFINE_SPINLOCK(kgdb_registration_lock);
82
83/* Action for the reboot notifiter, a global allow kdb to change it */
84static int kgdbreboot;
85/* kgdb console driver is loaded */
86static int kgdb_con_registered;
87/* determine if kgdb console output should be used */
88static int kgdb_use_con;
89/* Flag for alternate operations for early debugging */
90bool dbg_is_early = true;
91/* Next cpu to become the master debug core */
92int dbg_switch_cpu;
93
94/* Use kdb or gdbserver mode */
95int dbg_kdb_mode = 1;
96
97static int __init opt_kgdb_con(char *str)
98{
99 kgdb_use_con = 1;
100 return 0;
101}
102
103early_param("kgdbcon", opt_kgdb_con);
104
105module_param(kgdb_use_con, int, 0644);
106module_param(kgdbreboot, int, 0644);
107
108/*
109 * Holds information about breakpoints in a kernel. These breakpoints are
110 * added and removed by gdb.
111 */
112static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
113 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
114};
115
116/*
117 * The CPU# of the active CPU, or -1 if none:
118 */
119atomic_t kgdb_active = ATOMIC_INIT(-1);
120EXPORT_SYMBOL_GPL(kgdb_active);
121static DEFINE_RAW_SPINLOCK(dbg_master_lock);
122static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
123
124/*
125 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
126 * bootup code (which might not have percpu set up yet):
127 */
128static atomic_t masters_in_kgdb;
129static atomic_t slaves_in_kgdb;
130static atomic_t kgdb_break_tasklet_var;
131atomic_t kgdb_setting_breakpoint;
132
133struct task_struct *kgdb_usethread;
134struct task_struct *kgdb_contthread;
135
136int kgdb_single_step;
137static pid_t kgdb_sstep_pid;
138
139/* to keep track of the CPU which is doing the single stepping*/
140atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
141
142/*
143 * If you are debugging a problem where roundup (the collection of
144 * all other CPUs) is a problem [this should be extremely rare],
145 * then use the nokgdbroundup option to avoid roundup. In that case
146 * the other CPUs might interfere with your debugging context, so
147 * use this with care:
148 */
149static int kgdb_do_roundup = 1;
150
151static int __init opt_nokgdbroundup(char *str)
152{
153 kgdb_do_roundup = 0;
154
155 return 0;
156}
157
158early_param("nokgdbroundup", opt_nokgdbroundup);
159
160/*
161 * Finally, some KGDB code :-)
162 */
163
164/*
165 * Weak aliases for breakpoint management,
166 * can be overriden by architectures when needed:
167 */
168int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
169{
170 int err;
171
172 err = copy_from_kernel_nofault(bpt->saved_instr, (char *)bpt->bpt_addr,
173 BREAK_INSTR_SIZE);
174 if (err)
175 return err;
176 err = copy_to_kernel_nofault((char *)bpt->bpt_addr,
177 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
178 return err;
179}
180
181int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
182{
183 return copy_to_kernel_nofault((char *)bpt->bpt_addr,
184 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
185}
186
187int __weak kgdb_validate_break_address(unsigned long addr)
188{
189 struct kgdb_bkpt tmp;
190 int err;
191 /* Validate setting the breakpoint and then removing it. If the
192 * remove fails, the kernel needs to emit a bad message because we
193 * are deep trouble not being able to put things back the way we
194 * found them.
195 */
196 tmp.bpt_addr = addr;
197 err = kgdb_arch_set_breakpoint(&tmp);
198 if (err)
199 return err;
200 err = kgdb_arch_remove_breakpoint(&tmp);
201 if (err)
202 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
203 addr);
204 return err;
205}
206
207unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
208{
209 return instruction_pointer(regs);
210}
211
212int __weak kgdb_arch_init(void)
213{
214 return 0;
215}
216
217int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
218{
219 return 0;
220}
221
222#ifdef CONFIG_SMP
223
224/*
225 * Default (weak) implementation for kgdb_roundup_cpus
226 */
227
228static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd);
229
230void __weak kgdb_call_nmi_hook(void *ignored)
231{
232 /*
233 * NOTE: get_irq_regs() is supposed to get the registers from
234 * before the IPI interrupt happened and so is supposed to
235 * show where the processor was. In some situations it's
236 * possible we might be called without an IPI, so it might be
237 * safer to figure out how to make kgdb_breakpoint() work
238 * properly here.
239 */
240 kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
241}
242
243void __weak kgdb_roundup_cpus(void)
244{
245 call_single_data_t *csd;
246 int this_cpu = raw_smp_processor_id();
247 int cpu;
248 int ret;
249
250 for_each_online_cpu(cpu) {
251 /* No need to roundup ourselves */
252 if (cpu == this_cpu)
253 continue;
254
255 csd = &per_cpu(kgdb_roundup_csd, cpu);
256
257 /*
258 * If it didn't round up last time, don't try again
259 * since smp_call_function_single_async() will block.
260 *
261 * If rounding_up is false then we know that the
262 * previous call must have at least started and that
263 * means smp_call_function_single_async() won't block.
264 */
265 if (kgdb_info[cpu].rounding_up)
266 continue;
267 kgdb_info[cpu].rounding_up = true;
268
269 csd->func = kgdb_call_nmi_hook;
270 ret = smp_call_function_single_async(cpu, csd);
271 if (ret)
272 kgdb_info[cpu].rounding_up = false;
273 }
274}
275
276#endif
277
278/*
279 * Some architectures need cache flushes when we set/clear a
280 * breakpoint:
281 */
282static void kgdb_flush_swbreak_addr(unsigned long addr)
283{
284 if (!CACHE_FLUSH_IS_SAFE)
285 return;
286
287 if (current->mm) {
288 int i;
289
290 for (i = 0; i < VMACACHE_SIZE; i++) {
291 if (!current->vmacache.vmas[i])
292 continue;
293 flush_cache_range(current->vmacache.vmas[i],
294 addr, addr + BREAK_INSTR_SIZE);
295 }
296 }
297
298 /* Force flush instruction cache if it was outside the mm */
299 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
300}
301
302/*
303 * SW breakpoint management:
304 */
305int dbg_activate_sw_breakpoints(void)
306{
307 int error;
308 int ret = 0;
309 int i;
310
311 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
312 if (kgdb_break[i].state != BP_SET)
313 continue;
314
315 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
316 if (error) {
317 ret = error;
318 pr_info("BP install failed: %lx\n",
319 kgdb_break[i].bpt_addr);
320 continue;
321 }
322
323 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
324 kgdb_break[i].state = BP_ACTIVE;
325 }
326 return ret;
327}
328
329int dbg_set_sw_break(unsigned long addr)
330{
331 int err = kgdb_validate_break_address(addr);
332 int breakno = -1;
333 int i;
334
335 if (err)
336 return err;
337
338 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
339 if ((kgdb_break[i].state == BP_SET) &&
340 (kgdb_break[i].bpt_addr == addr))
341 return -EEXIST;
342 }
343 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
344 if (kgdb_break[i].state == BP_REMOVED &&
345 kgdb_break[i].bpt_addr == addr) {
346 breakno = i;
347 break;
348 }
349 }
350
351 if (breakno == -1) {
352 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
353 if (kgdb_break[i].state == BP_UNDEFINED) {
354 breakno = i;
355 break;
356 }
357 }
358 }
359
360 if (breakno == -1)
361 return -E2BIG;
362
363 kgdb_break[breakno].state = BP_SET;
364 kgdb_break[breakno].type = BP_BREAKPOINT;
365 kgdb_break[breakno].bpt_addr = addr;
366
367 return 0;
368}
369
370int dbg_deactivate_sw_breakpoints(void)
371{
372 int error;
373 int ret = 0;
374 int i;
375
376 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
377 if (kgdb_break[i].state != BP_ACTIVE)
378 continue;
379 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
380 if (error) {
381 pr_info("BP remove failed: %lx\n",
382 kgdb_break[i].bpt_addr);
383 ret = error;
384 }
385
386 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
387 kgdb_break[i].state = BP_SET;
388 }
389 return ret;
390}
391
392int dbg_remove_sw_break(unsigned long addr)
393{
394 int i;
395
396 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
397 if ((kgdb_break[i].state == BP_SET) &&
398 (kgdb_break[i].bpt_addr == addr)) {
399 kgdb_break[i].state = BP_REMOVED;
400 return 0;
401 }
402 }
403 return -ENOENT;
404}
405
406int kgdb_isremovedbreak(unsigned long addr)
407{
408 int i;
409
410 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
411 if ((kgdb_break[i].state == BP_REMOVED) &&
412 (kgdb_break[i].bpt_addr == addr))
413 return 1;
414 }
415 return 0;
416}
417
418int kgdb_has_hit_break(unsigned long addr)
419{
420 int i;
421
422 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
423 if (kgdb_break[i].state == BP_ACTIVE &&
424 kgdb_break[i].bpt_addr == addr)
425 return 1;
426 }
427 return 0;
428}
429
430int dbg_remove_all_break(void)
431{
432 int error;
433 int i;
434
435 /* Clear memory breakpoints. */
436 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
437 if (kgdb_break[i].state != BP_ACTIVE)
438 goto setundefined;
439 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
440 if (error)
441 pr_err("breakpoint remove failed: %lx\n",
442 kgdb_break[i].bpt_addr);
443setundefined:
444 kgdb_break[i].state = BP_UNDEFINED;
445 }
446
447 /* Clear hardware breakpoints. */
448 if (arch_kgdb_ops.remove_all_hw_break)
449 arch_kgdb_ops.remove_all_hw_break();
450
451 return 0;
452}
453
454#ifdef CONFIG_KGDB_KDB
455void kdb_dump_stack_on_cpu(int cpu)
456{
457 if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) {
458 dump_stack();
459 return;
460 }
461
462 if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) {
463 kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n",
464 cpu);
465 return;
466 }
467
468 /*
469 * In general, architectures don't support dumping the stack of a
470 * "running" process that's not the current one. From the point of
471 * view of the Linux, kernel processes that are looping in the kgdb
472 * slave loop are still "running". There's also no API (that actually
473 * works across all architectures) that can do a stack crawl based
474 * on registers passed as a parameter.
475 *
476 * Solve this conundrum by asking slave CPUs to do the backtrace
477 * themselves.
478 */
479 kgdb_info[cpu].exception_state |= DCPU_WANT_BT;
480 while (kgdb_info[cpu].exception_state & DCPU_WANT_BT)
481 cpu_relax();
482}
483#endif
484
485/*
486 * Return true if there is a valid kgdb I/O module. Also if no
487 * debugger is attached a message can be printed to the console about
488 * waiting for the debugger to attach.
489 *
490 * The print_wait argument is only to be true when called from inside
491 * the core kgdb_handle_exception, because it will wait for the
492 * debugger to attach.
493 */
494static int kgdb_io_ready(int print_wait)
495{
496 if (!dbg_io_ops)
497 return 0;
498 if (kgdb_connected)
499 return 1;
500 if (atomic_read(&kgdb_setting_breakpoint))
501 return 1;
502 if (print_wait) {
503#ifdef CONFIG_KGDB_KDB
504 if (!dbg_kdb_mode)
505 pr_crit("waiting... or $3#33 for KDB\n");
506#else
507 pr_crit("Waiting for remote debugger\n");
508#endif
509 }
510 return 1;
511}
512
513static int kgdb_reenter_check(struct kgdb_state *ks)
514{
515 unsigned long addr;
516
517 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
518 return 0;
519
520 /* Panic on recursive debugger calls: */
521 exception_level++;
522 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
523 dbg_deactivate_sw_breakpoints();
524
525 /*
526 * If the break point removed ok at the place exception
527 * occurred, try to recover and print a warning to the end
528 * user because the user planted a breakpoint in a place that
529 * KGDB needs in order to function.
530 */
531 if (dbg_remove_sw_break(addr) == 0) {
532 exception_level = 0;
533 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
534 dbg_activate_sw_breakpoints();
535 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
536 WARN_ON_ONCE(1);
537
538 return 1;
539 }
540 dbg_remove_all_break();
541 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
542
543 if (exception_level > 1) {
544 dump_stack();
545 kgdb_io_module_registered = false;
546 panic("Recursive entry to debugger");
547 }
548
549 pr_crit("re-enter exception: ALL breakpoints killed\n");
550#ifdef CONFIG_KGDB_KDB
551 /* Allow kdb to debug itself one level */
552 return 0;
553#endif
554 dump_stack();
555 panic("Recursive entry to debugger");
556
557 return 1;
558}
559
560static void dbg_touch_watchdogs(void)
561{
562 touch_softlockup_watchdog_sync();
563 clocksource_touch_watchdog();
564 rcu_cpu_stall_reset();
565}
566
567static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
568 int exception_state)
569{
570 unsigned long flags;
571 int sstep_tries = 100;
572 int error;
573 int cpu;
574 int trace_on = 0;
575 int online_cpus = num_online_cpus();
576 u64 time_left;
577
578 kgdb_info[ks->cpu].enter_kgdb++;
579 kgdb_info[ks->cpu].exception_state |= exception_state;
580
581 if (exception_state == DCPU_WANT_MASTER)
582 atomic_inc(&masters_in_kgdb);
583 else
584 atomic_inc(&slaves_in_kgdb);
585
586 if (arch_kgdb_ops.disable_hw_break)
587 arch_kgdb_ops.disable_hw_break(regs);
588
589acquirelock:
590 rcu_read_lock();
591 /*
592 * Interrupts will be restored by the 'trap return' code, except when
593 * single stepping.
594 */
595 local_irq_save(flags);
596
597 cpu = ks->cpu;
598 kgdb_info[cpu].debuggerinfo = regs;
599 kgdb_info[cpu].task = current;
600 kgdb_info[cpu].ret_state = 0;
601 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
602
603 /* Make sure the above info reaches the primary CPU */
604 smp_mb();
605
606 if (exception_level == 1) {
607 if (raw_spin_trylock(&dbg_master_lock))
608 atomic_xchg(&kgdb_active, cpu);
609 goto cpu_master_loop;
610 }
611
612 /*
613 * CPU will loop if it is a slave or request to become a kgdb
614 * master cpu and acquire the kgdb_active lock:
615 */
616 while (1) {
617cpu_loop:
618 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
619 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
620 goto cpu_master_loop;
621 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
622 if (raw_spin_trylock(&dbg_master_lock)) {
623 atomic_xchg(&kgdb_active, cpu);
624 break;
625 }
626 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) {
627 dump_stack();
628 kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT;
629 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
630 if (!raw_spin_is_locked(&dbg_slave_lock))
631 goto return_normal;
632 } else {
633return_normal:
634 /* Return to normal operation by executing any
635 * hw breakpoint fixup.
636 */
637 if (arch_kgdb_ops.correct_hw_break)
638 arch_kgdb_ops.correct_hw_break();
639 if (trace_on)
640 tracing_on();
641 kgdb_info[cpu].debuggerinfo = NULL;
642 kgdb_info[cpu].task = NULL;
643 kgdb_info[cpu].exception_state &=
644 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
645 kgdb_info[cpu].enter_kgdb--;
646 smp_mb__before_atomic();
647 atomic_dec(&slaves_in_kgdb);
648 dbg_touch_watchdogs();
649 local_irq_restore(flags);
650 rcu_read_unlock();
651 return 0;
652 }
653 cpu_relax();
654 }
655
656 /*
657 * For single stepping, try to only enter on the processor
658 * that was single stepping. To guard against a deadlock, the
659 * kernel will only try for the value of sstep_tries before
660 * giving up and continuing on.
661 */
662 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
663 (kgdb_info[cpu].task &&
664 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
665 atomic_set(&kgdb_active, -1);
666 raw_spin_unlock(&dbg_master_lock);
667 dbg_touch_watchdogs();
668 local_irq_restore(flags);
669 rcu_read_unlock();
670
671 goto acquirelock;
672 }
673
674 if (!kgdb_io_ready(1)) {
675 kgdb_info[cpu].ret_state = 1;
676 goto kgdb_restore; /* No I/O connection, resume the system */
677 }
678
679 /*
680 * Don't enter if we have hit a removed breakpoint.
681 */
682 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
683 goto kgdb_restore;
684
685 atomic_inc(&ignore_console_lock_warning);
686
687 /* Call the I/O driver's pre_exception routine */
688 if (dbg_io_ops->pre_exception)
689 dbg_io_ops->pre_exception();
690
691 /*
692 * Get the passive CPU lock which will hold all the non-primary
693 * CPU in a spin state while the debugger is active
694 */
695 if (!kgdb_single_step)
696 raw_spin_lock(&dbg_slave_lock);
697
698#ifdef CONFIG_SMP
699 /* If send_ready set, slaves are already waiting */
700 if (ks->send_ready)
701 atomic_set(ks->send_ready, 1);
702
703 /* Signal the other CPUs to enter kgdb_wait() */
704 else if ((!kgdb_single_step) && kgdb_do_roundup)
705 kgdb_roundup_cpus();
706#endif
707
708 /*
709 * Wait for the other CPUs to be notified and be waiting for us:
710 */
711 time_left = MSEC_PER_SEC;
712 while (kgdb_do_roundup && --time_left &&
713 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
714 online_cpus)
715 udelay(1000);
716 if (!time_left)
717 pr_crit("Timed out waiting for secondary CPUs.\n");
718
719 /*
720 * At this point the primary processor is completely
721 * in the debugger and all secondary CPUs are quiescent
722 */
723 dbg_deactivate_sw_breakpoints();
724 kgdb_single_step = 0;
725 kgdb_contthread = current;
726 exception_level = 0;
727 trace_on = tracing_is_on();
728 if (trace_on)
729 tracing_off();
730
731 while (1) {
732cpu_master_loop:
733 if (dbg_kdb_mode) {
734 kgdb_connected = 1;
735 error = kdb_stub(ks);
736 if (error == -1)
737 continue;
738 kgdb_connected = 0;
739 } else {
740 error = gdb_serial_stub(ks);
741 }
742
743 if (error == DBG_PASS_EVENT) {
744 dbg_kdb_mode = !dbg_kdb_mode;
745 } else if (error == DBG_SWITCH_CPU_EVENT) {
746 kgdb_info[dbg_switch_cpu].exception_state |=
747 DCPU_NEXT_MASTER;
748 goto cpu_loop;
749 } else {
750 kgdb_info[cpu].ret_state = error;
751 break;
752 }
753 }
754
755 /* Call the I/O driver's post_exception routine */
756 if (dbg_io_ops->post_exception)
757 dbg_io_ops->post_exception();
758
759 atomic_dec(&ignore_console_lock_warning);
760
761 if (!kgdb_single_step) {
762 raw_spin_unlock(&dbg_slave_lock);
763 /* Wait till all the CPUs have quit from the debugger. */
764 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
765 cpu_relax();
766 }
767
768kgdb_restore:
769 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
770 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
771 if (kgdb_info[sstep_cpu].task)
772 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
773 else
774 kgdb_sstep_pid = 0;
775 }
776 if (arch_kgdb_ops.correct_hw_break)
777 arch_kgdb_ops.correct_hw_break();
778 if (trace_on)
779 tracing_on();
780
781 kgdb_info[cpu].debuggerinfo = NULL;
782 kgdb_info[cpu].task = NULL;
783 kgdb_info[cpu].exception_state &=
784 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
785 kgdb_info[cpu].enter_kgdb--;
786 smp_mb__before_atomic();
787 atomic_dec(&masters_in_kgdb);
788 /* Free kgdb_active */
789 atomic_set(&kgdb_active, -1);
790 raw_spin_unlock(&dbg_master_lock);
791 dbg_touch_watchdogs();
792 local_irq_restore(flags);
793 rcu_read_unlock();
794
795 return kgdb_info[cpu].ret_state;
796}
797
798/*
799 * kgdb_handle_exception() - main entry point from a kernel exception
800 *
801 * Locking hierarchy:
802 * interface locks, if any (begin_session)
803 * kgdb lock (kgdb_active)
804 */
805int
806kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
807{
808 struct kgdb_state kgdb_var;
809 struct kgdb_state *ks = &kgdb_var;
810 int ret = 0;
811
812 if (arch_kgdb_ops.enable_nmi)
813 arch_kgdb_ops.enable_nmi(0);
814 /*
815 * Avoid entering the debugger if we were triggered due to an oops
816 * but panic_timeout indicates the system should automatically
817 * reboot on panic. We don't want to get stuck waiting for input
818 * on such systems, especially if its "just" an oops.
819 */
820 if (signo != SIGTRAP && panic_timeout)
821 return 1;
822
823 memset(ks, 0, sizeof(struct kgdb_state));
824 ks->cpu = raw_smp_processor_id();
825 ks->ex_vector = evector;
826 ks->signo = signo;
827 ks->err_code = ecode;
828 ks->linux_regs = regs;
829
830 if (kgdb_reenter_check(ks))
831 goto out; /* Ouch, double exception ! */
832 if (kgdb_info[ks->cpu].enter_kgdb != 0)
833 goto out;
834
835 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
836out:
837 if (arch_kgdb_ops.enable_nmi)
838 arch_kgdb_ops.enable_nmi(1);
839 return ret;
840}
841
842/*
843 * GDB places a breakpoint at this function to know dynamically loaded objects.
844 */
845static int module_event(struct notifier_block *self, unsigned long val,
846 void *data)
847{
848 return 0;
849}
850
851static struct notifier_block dbg_module_load_nb = {
852 .notifier_call = module_event,
853};
854
855int kgdb_nmicallback(int cpu, void *regs)
856{
857#ifdef CONFIG_SMP
858 struct kgdb_state kgdb_var;
859 struct kgdb_state *ks = &kgdb_var;
860
861 kgdb_info[cpu].rounding_up = false;
862
863 memset(ks, 0, sizeof(struct kgdb_state));
864 ks->cpu = cpu;
865 ks->linux_regs = regs;
866
867 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
868 raw_spin_is_locked(&dbg_master_lock)) {
869 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
870 return 0;
871 }
872#endif
873 return 1;
874}
875
876int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
877 atomic_t *send_ready)
878{
879#ifdef CONFIG_SMP
880 if (!kgdb_io_ready(0) || !send_ready)
881 return 1;
882
883 if (kgdb_info[cpu].enter_kgdb == 0) {
884 struct kgdb_state kgdb_var;
885 struct kgdb_state *ks = &kgdb_var;
886
887 memset(ks, 0, sizeof(struct kgdb_state));
888 ks->cpu = cpu;
889 ks->ex_vector = trapnr;
890 ks->signo = SIGTRAP;
891 ks->err_code = err_code;
892 ks->linux_regs = regs;
893 ks->send_ready = send_ready;
894 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
895 return 0;
896 }
897#endif
898 return 1;
899}
900
901static void kgdb_console_write(struct console *co, const char *s,
902 unsigned count)
903{
904 unsigned long flags;
905
906 /* If we're debugging, or KGDB has not connected, don't try
907 * and print. */
908 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
909 return;
910
911 local_irq_save(flags);
912 gdbstub_msg_write(s, count);
913 local_irq_restore(flags);
914}
915
916static struct console kgdbcons = {
917 .name = "kgdb",
918 .write = kgdb_console_write,
919 .flags = CON_PRINTBUFFER | CON_ENABLED,
920 .index = -1,
921};
922
923#ifdef CONFIG_MAGIC_SYSRQ
924static void sysrq_handle_dbg(int key)
925{
926 if (!dbg_io_ops) {
927 pr_crit("ERROR: No KGDB I/O module available\n");
928 return;
929 }
930 if (!kgdb_connected) {
931#ifdef CONFIG_KGDB_KDB
932 if (!dbg_kdb_mode)
933 pr_crit("KGDB or $3#33 for KDB\n");
934#else
935 pr_crit("Entering KGDB\n");
936#endif
937 }
938
939 kgdb_breakpoint();
940}
941
942static const struct sysrq_key_op sysrq_dbg_op = {
943 .handler = sysrq_handle_dbg,
944 .help_msg = "debug(g)",
945 .action_msg = "DEBUG",
946};
947#endif
948
949void kgdb_panic(const char *msg)
950{
951 if (!kgdb_io_module_registered)
952 return;
953
954 /*
955 * We don't want to get stuck waiting for input from user if
956 * "panic_timeout" indicates the system should automatically
957 * reboot on panic.
958 */
959 if (panic_timeout)
960 return;
961
962 if (dbg_kdb_mode)
963 kdb_printf("PANIC: %s\n", msg);
964
965 kgdb_breakpoint();
966}
967
968static void kgdb_initial_breakpoint(void)
969{
970 kgdb_break_asap = 0;
971
972 pr_crit("Waiting for connection from remote gdb...\n");
973 kgdb_breakpoint();
974}
975
976void __weak kgdb_arch_late(void)
977{
978}
979
980void __init dbg_late_init(void)
981{
982 dbg_is_early = false;
983 if (kgdb_io_module_registered)
984 kgdb_arch_late();
985 kdb_init(KDB_INIT_FULL);
986
987 if (kgdb_io_module_registered && kgdb_break_asap)
988 kgdb_initial_breakpoint();
989}
990
991static int
992dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
993{
994 /*
995 * Take the following action on reboot notify depending on value:
996 * 1 == Enter debugger
997 * 0 == [the default] detatch debug client
998 * -1 == Do nothing... and use this until the board resets
999 */
1000 switch (kgdbreboot) {
1001 case 1:
1002 kgdb_breakpoint();
1003 case -1:
1004 goto done;
1005 }
1006 if (!dbg_kdb_mode)
1007 gdbstub_exit(code);
1008done:
1009 return NOTIFY_DONE;
1010}
1011
1012static struct notifier_block dbg_reboot_notifier = {
1013 .notifier_call = dbg_notify_reboot,
1014 .next = NULL,
1015 .priority = INT_MAX,
1016};
1017
1018static void kgdb_register_callbacks(void)
1019{
1020 if (!kgdb_io_module_registered) {
1021 kgdb_io_module_registered = 1;
1022 kgdb_arch_init();
1023 if (!dbg_is_early)
1024 kgdb_arch_late();
1025 register_module_notifier(&dbg_module_load_nb);
1026 register_reboot_notifier(&dbg_reboot_notifier);
1027#ifdef CONFIG_MAGIC_SYSRQ
1028 register_sysrq_key('g', &sysrq_dbg_op);
1029#endif
1030 if (kgdb_use_con && !kgdb_con_registered) {
1031 register_console(&kgdbcons);
1032 kgdb_con_registered = 1;
1033 }
1034 }
1035}
1036
1037static void kgdb_unregister_callbacks(void)
1038{
1039 /*
1040 * When this routine is called KGDB should unregister from
1041 * handlers and clean up, making sure it is not handling any
1042 * break exceptions at the time.
1043 */
1044 if (kgdb_io_module_registered) {
1045 kgdb_io_module_registered = 0;
1046 unregister_reboot_notifier(&dbg_reboot_notifier);
1047 unregister_module_notifier(&dbg_module_load_nb);
1048 kgdb_arch_exit();
1049#ifdef CONFIG_MAGIC_SYSRQ
1050 unregister_sysrq_key('g', &sysrq_dbg_op);
1051#endif
1052 if (kgdb_con_registered) {
1053 unregister_console(&kgdbcons);
1054 kgdb_con_registered = 0;
1055 }
1056 }
1057}
1058
1059/*
1060 * There are times a tasklet needs to be used vs a compiled in
1061 * break point so as to cause an exception outside a kgdb I/O module,
1062 * such as is the case with kgdboe, where calling a breakpoint in the
1063 * I/O driver itself would be fatal.
1064 */
1065static void kgdb_tasklet_bpt(unsigned long ing)
1066{
1067 kgdb_breakpoint();
1068 atomic_set(&kgdb_break_tasklet_var, 0);
1069}
1070
1071static DECLARE_TASKLET_OLD(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt);
1072
1073void kgdb_schedule_breakpoint(void)
1074{
1075 if (atomic_read(&kgdb_break_tasklet_var) ||
1076 atomic_read(&kgdb_active) != -1 ||
1077 atomic_read(&kgdb_setting_breakpoint))
1078 return;
1079 atomic_inc(&kgdb_break_tasklet_var);
1080 tasklet_schedule(&kgdb_tasklet_breakpoint);
1081}
1082EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
1083
1084/**
1085 * kgdb_register_io_module - register KGDB IO module
1086 * @new_dbg_io_ops: the io ops vector
1087 *
1088 * Register it with the KGDB core.
1089 */
1090int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
1091{
1092 struct kgdb_io *old_dbg_io_ops;
1093 int err;
1094
1095 spin_lock(&kgdb_registration_lock);
1096
1097 old_dbg_io_ops = dbg_io_ops;
1098 if (old_dbg_io_ops) {
1099 if (!old_dbg_io_ops->deinit) {
1100 spin_unlock(&kgdb_registration_lock);
1101
1102 pr_err("KGDB I/O driver %s can't replace %s.\n",
1103 new_dbg_io_ops->name, old_dbg_io_ops->name);
1104 return -EBUSY;
1105 }
1106 pr_info("Replacing I/O driver %s with %s\n",
1107 old_dbg_io_ops->name, new_dbg_io_ops->name);
1108 }
1109
1110 if (new_dbg_io_ops->init) {
1111 err = new_dbg_io_ops->init();
1112 if (err) {
1113 spin_unlock(&kgdb_registration_lock);
1114 return err;
1115 }
1116 }
1117
1118 dbg_io_ops = new_dbg_io_ops;
1119
1120 spin_unlock(&kgdb_registration_lock);
1121
1122 if (old_dbg_io_ops) {
1123 old_dbg_io_ops->deinit();
1124 return 0;
1125 }
1126
1127 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1128
1129 /* Arm KGDB now. */
1130 kgdb_register_callbacks();
1131
1132 if (kgdb_break_asap &&
1133 (!dbg_is_early || IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG)))
1134 kgdb_initial_breakpoint();
1135
1136 return 0;
1137}
1138EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1139
1140/**
1141 * kkgdb_unregister_io_module - unregister KGDB IO module
1142 * @old_dbg_io_ops: the io ops vector
1143 *
1144 * Unregister it with the KGDB core.
1145 */
1146void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1147{
1148 BUG_ON(kgdb_connected);
1149
1150 /*
1151 * KGDB is no longer able to communicate out, so
1152 * unregister our callbacks and reset state.
1153 */
1154 kgdb_unregister_callbacks();
1155
1156 spin_lock(&kgdb_registration_lock);
1157
1158 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1159 dbg_io_ops = NULL;
1160
1161 spin_unlock(&kgdb_registration_lock);
1162
1163 if (old_dbg_io_ops->deinit)
1164 old_dbg_io_ops->deinit();
1165
1166 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1167 old_dbg_io_ops->name);
1168}
1169EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1170
1171int dbg_io_get_char(void)
1172{
1173 int ret = dbg_io_ops->read_char();
1174 if (ret == NO_POLL_CHAR)
1175 return -1;
1176 if (!dbg_kdb_mode)
1177 return ret;
1178 if (ret == 127)
1179 return 8;
1180 return ret;
1181}
1182
1183/**
1184 * kgdb_breakpoint - generate breakpoint exception
1185 *
1186 * This function will generate a breakpoint exception. It is used at the
1187 * beginning of a program to sync up with a debugger and can be used
1188 * otherwise as a quick means to stop program execution and "break" into
1189 * the debugger.
1190 */
1191noinline void kgdb_breakpoint(void)
1192{
1193 atomic_inc(&kgdb_setting_breakpoint);
1194 wmb(); /* Sync point before breakpoint */
1195 arch_kgdb_breakpoint();
1196 wmb(); /* Sync point after breakpoint */
1197 atomic_dec(&kgdb_setting_breakpoint);
1198}
1199EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1200
1201static int __init opt_kgdb_wait(char *str)
1202{
1203 kgdb_break_asap = 1;
1204
1205 kdb_init(KDB_INIT_EARLY);
1206 if (kgdb_io_module_registered &&
1207 IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG))
1208 kgdb_initial_breakpoint();
1209
1210 return 0;
1211}
1212
1213early_param("kgdbwait", opt_kgdb_wait);