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