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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/interrupt.h>
33#include <linux/spinlock.h>
34#include <linux/console.h>
35#include <linux/threads.h>
36#include <linux/uaccess.h>
37#include <linux/kernel.h>
38#include <linux/module.h>
39#include <linux/ptrace.h>
40#include <linux/string.h>
41#include <linux/delay.h>
42#include <linux/sched.h>
43#include <linux/sysrq.h>
44#include <linux/reboot.h>
45#include <linux/init.h>
46#include <linux/kgdb.h>
47#include <linux/kdb.h>
48#include <linux/pid.h>
49#include <linux/smp.h>
50#include <linux/mm.h>
51#include <linux/rcupdate.h>
52
53#include <asm/cacheflush.h>
54#include <asm/byteorder.h>
55#include <linux/atomic.h>
56
57#include "debug_core.h"
58
59static int kgdb_break_asap;
60
61struct debuggerinfo_struct kgdb_info[NR_CPUS];
62
63/**
64 * kgdb_connected - Is a host GDB connected to us?
65 */
66int kgdb_connected;
67EXPORT_SYMBOL_GPL(kgdb_connected);
68
69/* All the KGDB handlers are installed */
70int kgdb_io_module_registered;
71
72/* Guard for recursive entry */
73static int exception_level;
74
75struct kgdb_io *dbg_io_ops;
76static DEFINE_SPINLOCK(kgdb_registration_lock);
77
78/* Action for the reboot notifiter, a global allow kdb to change it */
79static int kgdbreboot;
80/* kgdb console driver is loaded */
81static int kgdb_con_registered;
82/* determine if kgdb console output should be used */
83static int kgdb_use_con;
84/* Flag for alternate operations for early debugging */
85bool dbg_is_early = true;
86/* Next cpu to become the master debug core */
87int dbg_switch_cpu;
88
89/* Use kdb or gdbserver mode */
90int dbg_kdb_mode = 1;
91
92static int __init opt_kgdb_con(char *str)
93{
94 kgdb_use_con = 1;
95 return 0;
96}
97
98early_param("kgdbcon", opt_kgdb_con);
99
100module_param(kgdb_use_con, int, 0644);
101module_param(kgdbreboot, int, 0644);
102
103/*
104 * Holds information about breakpoints in a kernel. These breakpoints are
105 * added and removed by gdb.
106 */
107static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
108 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
109};
110
111/*
112 * The CPU# of the active CPU, or -1 if none:
113 */
114atomic_t kgdb_active = ATOMIC_INIT(-1);
115EXPORT_SYMBOL_GPL(kgdb_active);
116static DEFINE_RAW_SPINLOCK(dbg_master_lock);
117static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
118
119/*
120 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
121 * bootup code (which might not have percpu set up yet):
122 */
123static atomic_t masters_in_kgdb;
124static atomic_t slaves_in_kgdb;
125static atomic_t kgdb_break_tasklet_var;
126atomic_t kgdb_setting_breakpoint;
127
128struct task_struct *kgdb_usethread;
129struct task_struct *kgdb_contthread;
130
131int kgdb_single_step;
132static pid_t kgdb_sstep_pid;
133
134/* to keep track of the CPU which is doing the single stepping*/
135atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
136
137/*
138 * If you are debugging a problem where roundup (the collection of
139 * all other CPUs) is a problem [this should be extremely rare],
140 * then use the nokgdbroundup option to avoid roundup. In that case
141 * the other CPUs might interfere with your debugging context, so
142 * use this with care:
143 */
144static int kgdb_do_roundup = 1;
145
146static int __init opt_nokgdbroundup(char *str)
147{
148 kgdb_do_roundup = 0;
149
150 return 0;
151}
152
153early_param("nokgdbroundup", opt_nokgdbroundup);
154
155/*
156 * Finally, some KGDB code :-)
157 */
158
159/*
160 * Weak aliases for breakpoint management,
161 * can be overriden by architectures when needed:
162 */
163int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
164{
165 int err;
166
167 err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
168 BREAK_INSTR_SIZE);
169 if (err)
170 return err;
171 err = probe_kernel_write((char *)bpt->bpt_addr,
172 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
173 return err;
174}
175
176int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
177{
178 return probe_kernel_write((char *)bpt->bpt_addr,
179 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
180}
181
182int __weak kgdb_validate_break_address(unsigned long addr)
183{
184 struct kgdb_bkpt tmp;
185 int err;
186 /* Validate setting the breakpoint and then removing it. If the
187 * remove fails, the kernel needs to emit a bad message because we
188 * are deep trouble not being able to put things back the way we
189 * found them.
190 */
191 tmp.bpt_addr = addr;
192 err = kgdb_arch_set_breakpoint(&tmp);
193 if (err)
194 return err;
195 err = kgdb_arch_remove_breakpoint(&tmp);
196 if (err)
197 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
198 "memory destroyed at: %lx", addr);
199 return err;
200}
201
202unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
203{
204 return instruction_pointer(regs);
205}
206
207int __weak kgdb_arch_init(void)
208{
209 return 0;
210}
211
212int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
213{
214 return 0;
215}
216
217/*
218 * Some architectures need cache flushes when we set/clear a
219 * breakpoint:
220 */
221static void kgdb_flush_swbreak_addr(unsigned long addr)
222{
223 if (!CACHE_FLUSH_IS_SAFE)
224 return;
225
226 if (current->mm && current->mm->mmap_cache) {
227 flush_cache_range(current->mm->mmap_cache,
228 addr, addr + BREAK_INSTR_SIZE);
229 }
230 /* Force flush instruction cache if it was outside the mm */
231 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
232}
233
234/*
235 * SW breakpoint management:
236 */
237int dbg_activate_sw_breakpoints(void)
238{
239 int error;
240 int ret = 0;
241 int i;
242
243 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
244 if (kgdb_break[i].state != BP_SET)
245 continue;
246
247 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
248 if (error) {
249 ret = error;
250 printk(KERN_INFO "KGDB: BP install failed: %lx",
251 kgdb_break[i].bpt_addr);
252 continue;
253 }
254
255 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
256 kgdb_break[i].state = BP_ACTIVE;
257 }
258 return ret;
259}
260
261int dbg_set_sw_break(unsigned long addr)
262{
263 int err = kgdb_validate_break_address(addr);
264 int breakno = -1;
265 int i;
266
267 if (err)
268 return err;
269
270 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
271 if ((kgdb_break[i].state == BP_SET) &&
272 (kgdb_break[i].bpt_addr == addr))
273 return -EEXIST;
274 }
275 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
276 if (kgdb_break[i].state == BP_REMOVED &&
277 kgdb_break[i].bpt_addr == addr) {
278 breakno = i;
279 break;
280 }
281 }
282
283 if (breakno == -1) {
284 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
285 if (kgdb_break[i].state == BP_UNDEFINED) {
286 breakno = i;
287 break;
288 }
289 }
290 }
291
292 if (breakno == -1)
293 return -E2BIG;
294
295 kgdb_break[breakno].state = BP_SET;
296 kgdb_break[breakno].type = BP_BREAKPOINT;
297 kgdb_break[breakno].bpt_addr = addr;
298
299 return 0;
300}
301
302int dbg_deactivate_sw_breakpoints(void)
303{
304 int error;
305 int ret = 0;
306 int i;
307
308 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
309 if (kgdb_break[i].state != BP_ACTIVE)
310 continue;
311 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
312 if (error) {
313 printk(KERN_INFO "KGDB: BP remove failed: %lx\n",
314 kgdb_break[i].bpt_addr);
315 ret = error;
316 }
317
318 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
319 kgdb_break[i].state = BP_SET;
320 }
321 return ret;
322}
323
324int dbg_remove_sw_break(unsigned long addr)
325{
326 int i;
327
328 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
329 if ((kgdb_break[i].state == BP_SET) &&
330 (kgdb_break[i].bpt_addr == addr)) {
331 kgdb_break[i].state = BP_REMOVED;
332 return 0;
333 }
334 }
335 return -ENOENT;
336}
337
338int kgdb_isremovedbreak(unsigned long addr)
339{
340 int i;
341
342 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
343 if ((kgdb_break[i].state == BP_REMOVED) &&
344 (kgdb_break[i].bpt_addr == addr))
345 return 1;
346 }
347 return 0;
348}
349
350int dbg_remove_all_break(void)
351{
352 int error;
353 int i;
354
355 /* Clear memory breakpoints. */
356 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
357 if (kgdb_break[i].state != BP_ACTIVE)
358 goto setundefined;
359 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
360 if (error)
361 printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
362 kgdb_break[i].bpt_addr);
363setundefined:
364 kgdb_break[i].state = BP_UNDEFINED;
365 }
366
367 /* Clear hardware breakpoints. */
368 if (arch_kgdb_ops.remove_all_hw_break)
369 arch_kgdb_ops.remove_all_hw_break();
370
371 return 0;
372}
373
374/*
375 * Return true if there is a valid kgdb I/O module. Also if no
376 * debugger is attached a message can be printed to the console about
377 * waiting for the debugger to attach.
378 *
379 * The print_wait argument is only to be true when called from inside
380 * the core kgdb_handle_exception, because it will wait for the
381 * debugger to attach.
382 */
383static int kgdb_io_ready(int print_wait)
384{
385 if (!dbg_io_ops)
386 return 0;
387 if (kgdb_connected)
388 return 1;
389 if (atomic_read(&kgdb_setting_breakpoint))
390 return 1;
391 if (print_wait) {
392#ifdef CONFIG_KGDB_KDB
393 if (!dbg_kdb_mode)
394 printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
395#else
396 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
397#endif
398 }
399 return 1;
400}
401
402static int kgdb_reenter_check(struct kgdb_state *ks)
403{
404 unsigned long addr;
405
406 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
407 return 0;
408
409 /* Panic on recursive debugger calls: */
410 exception_level++;
411 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
412 dbg_deactivate_sw_breakpoints();
413
414 /*
415 * If the break point removed ok at the place exception
416 * occurred, try to recover and print a warning to the end
417 * user because the user planted a breakpoint in a place that
418 * KGDB needs in order to function.
419 */
420 if (dbg_remove_sw_break(addr) == 0) {
421 exception_level = 0;
422 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
423 dbg_activate_sw_breakpoints();
424 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
425 addr);
426 WARN_ON_ONCE(1);
427
428 return 1;
429 }
430 dbg_remove_all_break();
431 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
432
433 if (exception_level > 1) {
434 dump_stack();
435 panic("Recursive entry to debugger");
436 }
437
438 printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
439#ifdef CONFIG_KGDB_KDB
440 /* Allow kdb to debug itself one level */
441 return 0;
442#endif
443 dump_stack();
444 panic("Recursive entry to debugger");
445
446 return 1;
447}
448
449static void dbg_touch_watchdogs(void)
450{
451 touch_softlockup_watchdog_sync();
452 clocksource_touch_watchdog();
453 rcu_cpu_stall_reset();
454}
455
456static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
457 int exception_state)
458{
459 unsigned long flags;
460 int sstep_tries = 100;
461 int error;
462 int cpu;
463 int trace_on = 0;
464 int online_cpus = num_online_cpus();
465
466 kgdb_info[ks->cpu].enter_kgdb++;
467 kgdb_info[ks->cpu].exception_state |= exception_state;
468
469 if (exception_state == DCPU_WANT_MASTER)
470 atomic_inc(&masters_in_kgdb);
471 else
472 atomic_inc(&slaves_in_kgdb);
473
474 if (arch_kgdb_ops.disable_hw_break)
475 arch_kgdb_ops.disable_hw_break(regs);
476
477acquirelock:
478 /*
479 * Interrupts will be restored by the 'trap return' code, except when
480 * single stepping.
481 */
482 local_irq_save(flags);
483
484 cpu = ks->cpu;
485 kgdb_info[cpu].debuggerinfo = regs;
486 kgdb_info[cpu].task = current;
487 kgdb_info[cpu].ret_state = 0;
488 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
489
490 /* Make sure the above info reaches the primary CPU */
491 smp_mb();
492
493 if (exception_level == 1) {
494 if (raw_spin_trylock(&dbg_master_lock))
495 atomic_xchg(&kgdb_active, cpu);
496 goto cpu_master_loop;
497 }
498
499 /*
500 * CPU will loop if it is a slave or request to become a kgdb
501 * master cpu and acquire the kgdb_active lock:
502 */
503 while (1) {
504cpu_loop:
505 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
506 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
507 goto cpu_master_loop;
508 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
509 if (raw_spin_trylock(&dbg_master_lock)) {
510 atomic_xchg(&kgdb_active, cpu);
511 break;
512 }
513 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
514 if (!raw_spin_is_locked(&dbg_slave_lock))
515 goto return_normal;
516 } else {
517return_normal:
518 /* Return to normal operation by executing any
519 * hw breakpoint fixup.
520 */
521 if (arch_kgdb_ops.correct_hw_break)
522 arch_kgdb_ops.correct_hw_break();
523 if (trace_on)
524 tracing_on();
525 kgdb_info[cpu].exception_state &=
526 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
527 kgdb_info[cpu].enter_kgdb--;
528 smp_mb__before_atomic_dec();
529 atomic_dec(&slaves_in_kgdb);
530 dbg_touch_watchdogs();
531 local_irq_restore(flags);
532 return 0;
533 }
534 cpu_relax();
535 }
536
537 /*
538 * For single stepping, try to only enter on the processor
539 * that was single stepping. To guard against a deadlock, the
540 * kernel will only try for the value of sstep_tries before
541 * giving up and continuing on.
542 */
543 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
544 (kgdb_info[cpu].task &&
545 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
546 atomic_set(&kgdb_active, -1);
547 raw_spin_unlock(&dbg_master_lock);
548 dbg_touch_watchdogs();
549 local_irq_restore(flags);
550
551 goto acquirelock;
552 }
553
554 if (!kgdb_io_ready(1)) {
555 kgdb_info[cpu].ret_state = 1;
556 goto kgdb_restore; /* No I/O connection, resume the system */
557 }
558
559 /*
560 * Don't enter if we have hit a removed breakpoint.
561 */
562 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
563 goto kgdb_restore;
564
565 /* Call the I/O driver's pre_exception routine */
566 if (dbg_io_ops->pre_exception)
567 dbg_io_ops->pre_exception();
568
569 /*
570 * Get the passive CPU lock which will hold all the non-primary
571 * CPU in a spin state while the debugger is active
572 */
573 if (!kgdb_single_step)
574 raw_spin_lock(&dbg_slave_lock);
575
576#ifdef CONFIG_SMP
577 /* Signal the other CPUs to enter kgdb_wait() */
578 if ((!kgdb_single_step) && kgdb_do_roundup)
579 kgdb_roundup_cpus(flags);
580#endif
581
582 /*
583 * Wait for the other CPUs to be notified and be waiting for us:
584 */
585 while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) +
586 atomic_read(&slaves_in_kgdb)) != online_cpus)
587 cpu_relax();
588
589 /*
590 * At this point the primary processor is completely
591 * in the debugger and all secondary CPUs are quiescent
592 */
593 dbg_deactivate_sw_breakpoints();
594 kgdb_single_step = 0;
595 kgdb_contthread = current;
596 exception_level = 0;
597 trace_on = tracing_is_on();
598 if (trace_on)
599 tracing_off();
600
601 while (1) {
602cpu_master_loop:
603 if (dbg_kdb_mode) {
604 kgdb_connected = 1;
605 error = kdb_stub(ks);
606 if (error == -1)
607 continue;
608 kgdb_connected = 0;
609 } else {
610 error = gdb_serial_stub(ks);
611 }
612
613 if (error == DBG_PASS_EVENT) {
614 dbg_kdb_mode = !dbg_kdb_mode;
615 } else if (error == DBG_SWITCH_CPU_EVENT) {
616 kgdb_info[dbg_switch_cpu].exception_state |=
617 DCPU_NEXT_MASTER;
618 goto cpu_loop;
619 } else {
620 kgdb_info[cpu].ret_state = error;
621 break;
622 }
623 }
624
625 /* Call the I/O driver's post_exception routine */
626 if (dbg_io_ops->post_exception)
627 dbg_io_ops->post_exception();
628
629 if (!kgdb_single_step) {
630 raw_spin_unlock(&dbg_slave_lock);
631 /* Wait till all the CPUs have quit from the debugger. */
632 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
633 cpu_relax();
634 }
635
636kgdb_restore:
637 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
638 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
639 if (kgdb_info[sstep_cpu].task)
640 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
641 else
642 kgdb_sstep_pid = 0;
643 }
644 if (arch_kgdb_ops.correct_hw_break)
645 arch_kgdb_ops.correct_hw_break();
646 if (trace_on)
647 tracing_on();
648
649 kgdb_info[cpu].exception_state &=
650 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
651 kgdb_info[cpu].enter_kgdb--;
652 smp_mb__before_atomic_dec();
653 atomic_dec(&masters_in_kgdb);
654 /* Free kgdb_active */
655 atomic_set(&kgdb_active, -1);
656 raw_spin_unlock(&dbg_master_lock);
657 dbg_touch_watchdogs();
658 local_irq_restore(flags);
659
660 return kgdb_info[cpu].ret_state;
661}
662
663/*
664 * kgdb_handle_exception() - main entry point from a kernel exception
665 *
666 * Locking hierarchy:
667 * interface locks, if any (begin_session)
668 * kgdb lock (kgdb_active)
669 */
670int
671kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
672{
673 struct kgdb_state kgdb_var;
674 struct kgdb_state *ks = &kgdb_var;
675
676 ks->cpu = raw_smp_processor_id();
677 ks->ex_vector = evector;
678 ks->signo = signo;
679 ks->err_code = ecode;
680 ks->kgdb_usethreadid = 0;
681 ks->linux_regs = regs;
682
683 if (kgdb_reenter_check(ks))
684 return 0; /* Ouch, double exception ! */
685 if (kgdb_info[ks->cpu].enter_kgdb != 0)
686 return 0;
687
688 return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
689}
690
691int kgdb_nmicallback(int cpu, void *regs)
692{
693#ifdef CONFIG_SMP
694 struct kgdb_state kgdb_var;
695 struct kgdb_state *ks = &kgdb_var;
696
697 memset(ks, 0, sizeof(struct kgdb_state));
698 ks->cpu = cpu;
699 ks->linux_regs = regs;
700
701 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
702 raw_spin_is_locked(&dbg_master_lock)) {
703 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
704 return 0;
705 }
706#endif
707 return 1;
708}
709
710static void kgdb_console_write(struct console *co, const char *s,
711 unsigned count)
712{
713 unsigned long flags;
714
715 /* If we're debugging, or KGDB has not connected, don't try
716 * and print. */
717 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
718 return;
719
720 local_irq_save(flags);
721 gdbstub_msg_write(s, count);
722 local_irq_restore(flags);
723}
724
725static struct console kgdbcons = {
726 .name = "kgdb",
727 .write = kgdb_console_write,
728 .flags = CON_PRINTBUFFER | CON_ENABLED,
729 .index = -1,
730};
731
732#ifdef CONFIG_MAGIC_SYSRQ
733static void sysrq_handle_dbg(int key)
734{
735 if (!dbg_io_ops) {
736 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
737 return;
738 }
739 if (!kgdb_connected) {
740#ifdef CONFIG_KGDB_KDB
741 if (!dbg_kdb_mode)
742 printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
743#else
744 printk(KERN_CRIT "Entering KGDB\n");
745#endif
746 }
747
748 kgdb_breakpoint();
749}
750
751static struct sysrq_key_op sysrq_dbg_op = {
752 .handler = sysrq_handle_dbg,
753 .help_msg = "debug(G)",
754 .action_msg = "DEBUG",
755};
756#endif
757
758static int kgdb_panic_event(struct notifier_block *self,
759 unsigned long val,
760 void *data)
761{
762 if (dbg_kdb_mode)
763 kdb_printf("PANIC: %s\n", (char *)data);
764 kgdb_breakpoint();
765 return NOTIFY_DONE;
766}
767
768static struct notifier_block kgdb_panic_event_nb = {
769 .notifier_call = kgdb_panic_event,
770 .priority = INT_MAX,
771};
772
773void __weak kgdb_arch_late(void)
774{
775}
776
777void __init dbg_late_init(void)
778{
779 dbg_is_early = false;
780 if (kgdb_io_module_registered)
781 kgdb_arch_late();
782 kdb_init(KDB_INIT_FULL);
783}
784
785static int
786dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
787{
788 /*
789 * Take the following action on reboot notify depending on value:
790 * 1 == Enter debugger
791 * 0 == [the default] detatch debug client
792 * -1 == Do nothing... and use this until the board resets
793 */
794 switch (kgdbreboot) {
795 case 1:
796 kgdb_breakpoint();
797 case -1:
798 goto done;
799 }
800 if (!dbg_kdb_mode)
801 gdbstub_exit(code);
802done:
803 return NOTIFY_DONE;
804}
805
806static struct notifier_block dbg_reboot_notifier = {
807 .notifier_call = dbg_notify_reboot,
808 .next = NULL,
809 .priority = INT_MAX,
810};
811
812static void kgdb_register_callbacks(void)
813{
814 if (!kgdb_io_module_registered) {
815 kgdb_io_module_registered = 1;
816 kgdb_arch_init();
817 if (!dbg_is_early)
818 kgdb_arch_late();
819 register_reboot_notifier(&dbg_reboot_notifier);
820 atomic_notifier_chain_register(&panic_notifier_list,
821 &kgdb_panic_event_nb);
822#ifdef CONFIG_MAGIC_SYSRQ
823 register_sysrq_key('g', &sysrq_dbg_op);
824#endif
825 if (kgdb_use_con && !kgdb_con_registered) {
826 register_console(&kgdbcons);
827 kgdb_con_registered = 1;
828 }
829 }
830}
831
832static void kgdb_unregister_callbacks(void)
833{
834 /*
835 * When this routine is called KGDB should unregister from the
836 * panic handler and clean up, making sure it is not handling any
837 * break exceptions at the time.
838 */
839 if (kgdb_io_module_registered) {
840 kgdb_io_module_registered = 0;
841 unregister_reboot_notifier(&dbg_reboot_notifier);
842 atomic_notifier_chain_unregister(&panic_notifier_list,
843 &kgdb_panic_event_nb);
844 kgdb_arch_exit();
845#ifdef CONFIG_MAGIC_SYSRQ
846 unregister_sysrq_key('g', &sysrq_dbg_op);
847#endif
848 if (kgdb_con_registered) {
849 unregister_console(&kgdbcons);
850 kgdb_con_registered = 0;
851 }
852 }
853}
854
855/*
856 * There are times a tasklet needs to be used vs a compiled in
857 * break point so as to cause an exception outside a kgdb I/O module,
858 * such as is the case with kgdboe, where calling a breakpoint in the
859 * I/O driver itself would be fatal.
860 */
861static void kgdb_tasklet_bpt(unsigned long ing)
862{
863 kgdb_breakpoint();
864 atomic_set(&kgdb_break_tasklet_var, 0);
865}
866
867static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
868
869void kgdb_schedule_breakpoint(void)
870{
871 if (atomic_read(&kgdb_break_tasklet_var) ||
872 atomic_read(&kgdb_active) != -1 ||
873 atomic_read(&kgdb_setting_breakpoint))
874 return;
875 atomic_inc(&kgdb_break_tasklet_var);
876 tasklet_schedule(&kgdb_tasklet_breakpoint);
877}
878EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
879
880static void kgdb_initial_breakpoint(void)
881{
882 kgdb_break_asap = 0;
883
884 printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
885 kgdb_breakpoint();
886}
887
888/**
889 * kgdb_register_io_module - register KGDB IO module
890 * @new_dbg_io_ops: the io ops vector
891 *
892 * Register it with the KGDB core.
893 */
894int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
895{
896 int err;
897
898 spin_lock(&kgdb_registration_lock);
899
900 if (dbg_io_ops) {
901 spin_unlock(&kgdb_registration_lock);
902
903 printk(KERN_ERR "kgdb: Another I/O driver is already "
904 "registered with KGDB.\n");
905 return -EBUSY;
906 }
907
908 if (new_dbg_io_ops->init) {
909 err = new_dbg_io_ops->init();
910 if (err) {
911 spin_unlock(&kgdb_registration_lock);
912 return err;
913 }
914 }
915
916 dbg_io_ops = new_dbg_io_ops;
917
918 spin_unlock(&kgdb_registration_lock);
919
920 printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
921 new_dbg_io_ops->name);
922
923 /* Arm KGDB now. */
924 kgdb_register_callbacks();
925
926 if (kgdb_break_asap)
927 kgdb_initial_breakpoint();
928
929 return 0;
930}
931EXPORT_SYMBOL_GPL(kgdb_register_io_module);
932
933/**
934 * kkgdb_unregister_io_module - unregister KGDB IO module
935 * @old_dbg_io_ops: the io ops vector
936 *
937 * Unregister it with the KGDB core.
938 */
939void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
940{
941 BUG_ON(kgdb_connected);
942
943 /*
944 * KGDB is no longer able to communicate out, so
945 * unregister our callbacks and reset state.
946 */
947 kgdb_unregister_callbacks();
948
949 spin_lock(&kgdb_registration_lock);
950
951 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
952 dbg_io_ops = NULL;
953
954 spin_unlock(&kgdb_registration_lock);
955
956 printk(KERN_INFO
957 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
958 old_dbg_io_ops->name);
959}
960EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
961
962int dbg_io_get_char(void)
963{
964 int ret = dbg_io_ops->read_char();
965 if (ret == NO_POLL_CHAR)
966 return -1;
967 if (!dbg_kdb_mode)
968 return ret;
969 if (ret == 127)
970 return 8;
971 return ret;
972}
973
974/**
975 * kgdb_breakpoint - generate breakpoint exception
976 *
977 * This function will generate a breakpoint exception. It is used at the
978 * beginning of a program to sync up with a debugger and can be used
979 * otherwise as a quick means to stop program execution and "break" into
980 * the debugger.
981 */
982void kgdb_breakpoint(void)
983{
984 atomic_inc(&kgdb_setting_breakpoint);
985 wmb(); /* Sync point before breakpoint */
986 arch_kgdb_breakpoint();
987 wmb(); /* Sync point after breakpoint */
988 atomic_dec(&kgdb_setting_breakpoint);
989}
990EXPORT_SYMBOL_GPL(kgdb_breakpoint);
991
992static int __init opt_kgdb_wait(char *str)
993{
994 kgdb_break_asap = 1;
995
996 kdb_init(KDB_INIT_EARLY);
997 if (kgdb_io_module_registered)
998 kgdb_initial_breakpoint();
999
1000 return 0;
1001}
1002
1003early_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 notifier, 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
97module_param(kgdb_use_con, int, 0644);
98module_param(kgdbreboot, int, 0644);
99
100/*
101 * Holds information about breakpoints in a kernel. These breakpoints are
102 * added and removed by gdb.
103 */
104static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
105 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
106};
107
108/*
109 * The CPU# of the active CPU, or -1 if none:
110 */
111atomic_t kgdb_active = ATOMIC_INIT(-1);
112EXPORT_SYMBOL_GPL(kgdb_active);
113static DEFINE_RAW_SPINLOCK(dbg_master_lock);
114static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
115
116/*
117 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
118 * bootup code (which might not have percpu set up yet):
119 */
120static atomic_t masters_in_kgdb;
121static atomic_t slaves_in_kgdb;
122atomic_t kgdb_setting_breakpoint;
123
124struct task_struct *kgdb_usethread;
125struct task_struct *kgdb_contthread;
126
127int kgdb_single_step;
128static pid_t kgdb_sstep_pid;
129
130/* to keep track of the CPU which is doing the single stepping*/
131atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
132
133/*
134 * If you are debugging a problem where roundup (the collection of
135 * all other CPUs) is a problem [this should be extremely rare],
136 * then use the nokgdbroundup option to avoid roundup. In that case
137 * the other CPUs might interfere with your debugging context, so
138 * use this with care:
139 */
140static int kgdb_do_roundup = 1;
141
142static int __init opt_nokgdbroundup(char *str)
143{
144 kgdb_do_roundup = 0;
145
146 return 0;
147}
148
149early_param("nokgdbroundup", opt_nokgdbroundup);
150
151/*
152 * Finally, some KGDB code :-)
153 */
154
155/*
156 * Weak aliases for breakpoint management,
157 * can be overridden by architectures when needed:
158 */
159int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
160{
161 int err;
162
163 err = copy_from_kernel_nofault(bpt->saved_instr, (char *)bpt->bpt_addr,
164 BREAK_INSTR_SIZE);
165 if (err)
166 return err;
167 err = copy_to_kernel_nofault((char *)bpt->bpt_addr,
168 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
169 return err;
170}
171NOKPROBE_SYMBOL(kgdb_arch_set_breakpoint);
172
173int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
174{
175 return copy_to_kernel_nofault((char *)bpt->bpt_addr,
176 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
177}
178NOKPROBE_SYMBOL(kgdb_arch_remove_breakpoint);
179
180int __weak kgdb_validate_break_address(unsigned long addr)
181{
182 struct kgdb_bkpt tmp;
183 int err;
184
185 if (kgdb_within_blocklist(addr))
186 return -EINVAL;
187
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 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
200 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}
208NOKPROBE_SYMBOL(kgdb_arch_pc);
209
210int __weak kgdb_arch_init(void)
211{
212 return 0;
213}
214
215int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
216{
217 return 0;
218}
219NOKPROBE_SYMBOL(kgdb_skipexception);
220
221#ifdef CONFIG_SMP
222
223/*
224 * Default (weak) implementation for kgdb_roundup_cpus
225 */
226
227void __weak kgdb_call_nmi_hook(void *ignored)
228{
229 /*
230 * NOTE: get_irq_regs() is supposed to get the registers from
231 * before the IPI interrupt happened and so is supposed to
232 * show where the processor was. In some situations it's
233 * possible we might be called without an IPI, so it might be
234 * safer to figure out how to make kgdb_breakpoint() work
235 * properly here.
236 */
237 kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
238}
239NOKPROBE_SYMBOL(kgdb_call_nmi_hook);
240
241static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd) =
242 CSD_INIT(kgdb_call_nmi_hook, NULL);
243
244void __weak kgdb_roundup_cpus(void)
245{
246 call_single_data_t *csd;
247 int this_cpu = raw_smp_processor_id();
248 int cpu;
249 int ret;
250
251 for_each_online_cpu(cpu) {
252 /* No need to roundup ourselves */
253 if (cpu == this_cpu)
254 continue;
255
256 csd = &per_cpu(kgdb_roundup_csd, cpu);
257
258 /*
259 * If it didn't round up last time, don't try again
260 * since smp_call_function_single_async() will block.
261 *
262 * If rounding_up is false then we know that the
263 * previous call must have at least started and that
264 * means smp_call_function_single_async() won't block.
265 */
266 if (kgdb_info[cpu].rounding_up)
267 continue;
268 kgdb_info[cpu].rounding_up = true;
269
270 ret = smp_call_function_single_async(cpu, csd);
271 if (ret)
272 kgdb_info[cpu].rounding_up = false;
273 }
274}
275NOKPROBE_SYMBOL(kgdb_roundup_cpus);
276
277#endif
278
279/*
280 * Some architectures need cache flushes when we set/clear a
281 * breakpoint:
282 */
283static void kgdb_flush_swbreak_addr(unsigned long addr)
284{
285 if (!CACHE_FLUSH_IS_SAFE)
286 return;
287
288 if (current->mm) {
289 int i;
290
291 for (i = 0; i < VMACACHE_SIZE; i++) {
292 if (!current->vmacache.vmas[i])
293 continue;
294 flush_cache_range(current->vmacache.vmas[i],
295 addr, addr + BREAK_INSTR_SIZE);
296 }
297 }
298
299 /* Force flush instruction cache if it was outside the mm */
300 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
301}
302NOKPROBE_SYMBOL(kgdb_flush_swbreak_addr);
303
304/*
305 * SW breakpoint management:
306 */
307int dbg_activate_sw_breakpoints(void)
308{
309 int error;
310 int ret = 0;
311 int i;
312
313 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
314 if (kgdb_break[i].state != BP_SET)
315 continue;
316
317 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
318 if (error) {
319 ret = error;
320 pr_info("BP install failed: %lx\n",
321 kgdb_break[i].bpt_addr);
322 continue;
323 }
324
325 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
326 kgdb_break[i].state = BP_ACTIVE;
327 }
328 return ret;
329}
330NOKPROBE_SYMBOL(dbg_activate_sw_breakpoints);
331
332int dbg_set_sw_break(unsigned long addr)
333{
334 int err = kgdb_validate_break_address(addr);
335 int breakno = -1;
336 int i;
337
338 if (err)
339 return err;
340
341 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
342 if ((kgdb_break[i].state == BP_SET) &&
343 (kgdb_break[i].bpt_addr == addr))
344 return -EEXIST;
345 }
346 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
347 if (kgdb_break[i].state == BP_REMOVED &&
348 kgdb_break[i].bpt_addr == addr) {
349 breakno = i;
350 break;
351 }
352 }
353
354 if (breakno == -1) {
355 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
356 if (kgdb_break[i].state == BP_UNDEFINED) {
357 breakno = i;
358 break;
359 }
360 }
361 }
362
363 if (breakno == -1)
364 return -E2BIG;
365
366 kgdb_break[breakno].state = BP_SET;
367 kgdb_break[breakno].type = BP_BREAKPOINT;
368 kgdb_break[breakno].bpt_addr = addr;
369
370 return 0;
371}
372
373int dbg_deactivate_sw_breakpoints(void)
374{
375 int error;
376 int ret = 0;
377 int i;
378
379 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
380 if (kgdb_break[i].state != BP_ACTIVE)
381 continue;
382 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
383 if (error) {
384 pr_info("BP remove failed: %lx\n",
385 kgdb_break[i].bpt_addr);
386 ret = error;
387 }
388
389 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
390 kgdb_break[i].state = BP_SET;
391 }
392 return ret;
393}
394NOKPROBE_SYMBOL(dbg_deactivate_sw_breakpoints);
395
396int dbg_remove_sw_break(unsigned long addr)
397{
398 int i;
399
400 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
401 if ((kgdb_break[i].state == BP_SET) &&
402 (kgdb_break[i].bpt_addr == addr)) {
403 kgdb_break[i].state = BP_REMOVED;
404 return 0;
405 }
406 }
407 return -ENOENT;
408}
409
410int kgdb_isremovedbreak(unsigned long addr)
411{
412 int i;
413
414 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
415 if ((kgdb_break[i].state == BP_REMOVED) &&
416 (kgdb_break[i].bpt_addr == addr))
417 return 1;
418 }
419 return 0;
420}
421
422int kgdb_has_hit_break(unsigned long addr)
423{
424 int i;
425
426 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
427 if (kgdb_break[i].state == BP_ACTIVE &&
428 kgdb_break[i].bpt_addr == addr)
429 return 1;
430 }
431 return 0;
432}
433
434int dbg_remove_all_break(void)
435{
436 int error;
437 int i;
438
439 /* Clear memory breakpoints. */
440 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
441 if (kgdb_break[i].state != BP_ACTIVE)
442 goto setundefined;
443 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
444 if (error)
445 pr_err("breakpoint remove failed: %lx\n",
446 kgdb_break[i].bpt_addr);
447setundefined:
448 kgdb_break[i].state = BP_UNDEFINED;
449 }
450
451 /* Clear hardware breakpoints. */
452 if (arch_kgdb_ops.remove_all_hw_break)
453 arch_kgdb_ops.remove_all_hw_break();
454
455 return 0;
456}
457
458void kgdb_free_init_mem(void)
459{
460 int i;
461
462 /* Clear init memory breakpoints. */
463 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
464 if (init_section_contains((void *)kgdb_break[i].bpt_addr, 0))
465 kgdb_break[i].state = BP_UNDEFINED;
466 }
467}
468
469#ifdef CONFIG_KGDB_KDB
470void kdb_dump_stack_on_cpu(int cpu)
471{
472 if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) {
473 dump_stack();
474 return;
475 }
476
477 if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) {
478 kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n",
479 cpu);
480 return;
481 }
482
483 /*
484 * In general, architectures don't support dumping the stack of a
485 * "running" process that's not the current one. From the point of
486 * view of the Linux, kernel processes that are looping in the kgdb
487 * slave loop are still "running". There's also no API (that actually
488 * works across all architectures) that can do a stack crawl based
489 * on registers passed as a parameter.
490 *
491 * Solve this conundrum by asking slave CPUs to do the backtrace
492 * themselves.
493 */
494 kgdb_info[cpu].exception_state |= DCPU_WANT_BT;
495 while (kgdb_info[cpu].exception_state & DCPU_WANT_BT)
496 cpu_relax();
497}
498#endif
499
500/*
501 * Return true if there is a valid kgdb I/O module. Also if no
502 * debugger is attached a message can be printed to the console about
503 * waiting for the debugger to attach.
504 *
505 * The print_wait argument is only to be true when called from inside
506 * the core kgdb_handle_exception, because it will wait for the
507 * debugger to attach.
508 */
509static int kgdb_io_ready(int print_wait)
510{
511 if (!dbg_io_ops)
512 return 0;
513 if (kgdb_connected)
514 return 1;
515 if (atomic_read(&kgdb_setting_breakpoint))
516 return 1;
517 if (print_wait) {
518#ifdef CONFIG_KGDB_KDB
519 if (!dbg_kdb_mode)
520 pr_crit("waiting... or $3#33 for KDB\n");
521#else
522 pr_crit("Waiting for remote debugger\n");
523#endif
524 }
525 return 1;
526}
527NOKPROBE_SYMBOL(kgdb_io_ready);
528
529static int kgdb_reenter_check(struct kgdb_state *ks)
530{
531 unsigned long addr;
532
533 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
534 return 0;
535
536 /* Panic on recursive debugger calls: */
537 exception_level++;
538 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
539 dbg_deactivate_sw_breakpoints();
540
541 /*
542 * If the break point removed ok at the place exception
543 * occurred, try to recover and print a warning to the end
544 * user because the user planted a breakpoint in a place that
545 * KGDB needs in order to function.
546 */
547 if (dbg_remove_sw_break(addr) == 0) {
548 exception_level = 0;
549 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
550 dbg_activate_sw_breakpoints();
551 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
552 WARN_ON_ONCE(1);
553
554 return 1;
555 }
556 dbg_remove_all_break();
557 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
558
559 if (exception_level > 1) {
560 dump_stack();
561 kgdb_io_module_registered = false;
562 panic("Recursive entry to debugger");
563 }
564
565 pr_crit("re-enter exception: ALL breakpoints killed\n");
566#ifdef CONFIG_KGDB_KDB
567 /* Allow kdb to debug itself one level */
568 return 0;
569#endif
570 dump_stack();
571 panic("Recursive entry to debugger");
572
573 return 1;
574}
575NOKPROBE_SYMBOL(kgdb_reenter_check);
576
577static void dbg_touch_watchdogs(void)
578{
579 touch_softlockup_watchdog_sync();
580 clocksource_touch_watchdog();
581 rcu_cpu_stall_reset();
582}
583NOKPROBE_SYMBOL(dbg_touch_watchdogs);
584
585static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
586 int exception_state)
587{
588 unsigned long flags;
589 int sstep_tries = 100;
590 int error;
591 int cpu;
592 int trace_on = 0;
593 int online_cpus = num_online_cpus();
594 u64 time_left;
595
596 kgdb_info[ks->cpu].enter_kgdb++;
597 kgdb_info[ks->cpu].exception_state |= exception_state;
598
599 if (exception_state == DCPU_WANT_MASTER)
600 atomic_inc(&masters_in_kgdb);
601 else
602 atomic_inc(&slaves_in_kgdb);
603
604 if (arch_kgdb_ops.disable_hw_break)
605 arch_kgdb_ops.disable_hw_break(regs);
606
607acquirelock:
608 rcu_read_lock();
609 /*
610 * Interrupts will be restored by the 'trap return' code, except when
611 * single stepping.
612 */
613 local_irq_save(flags);
614
615 cpu = ks->cpu;
616 kgdb_info[cpu].debuggerinfo = regs;
617 kgdb_info[cpu].task = current;
618 kgdb_info[cpu].ret_state = 0;
619 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
620
621 /* Make sure the above info reaches the primary CPU */
622 smp_mb();
623
624 if (exception_level == 1) {
625 if (raw_spin_trylock(&dbg_master_lock))
626 atomic_xchg(&kgdb_active, cpu);
627 goto cpu_master_loop;
628 }
629
630 /*
631 * CPU will loop if it is a slave or request to become a kgdb
632 * master cpu and acquire the kgdb_active lock:
633 */
634 while (1) {
635cpu_loop:
636 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
637 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
638 goto cpu_master_loop;
639 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
640 if (raw_spin_trylock(&dbg_master_lock)) {
641 atomic_xchg(&kgdb_active, cpu);
642 break;
643 }
644 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) {
645 dump_stack();
646 kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT;
647 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
648 if (!raw_spin_is_locked(&dbg_slave_lock))
649 goto return_normal;
650 } else {
651return_normal:
652 /* Return to normal operation by executing any
653 * hw breakpoint fixup.
654 */
655 if (arch_kgdb_ops.correct_hw_break)
656 arch_kgdb_ops.correct_hw_break();
657 if (trace_on)
658 tracing_on();
659 kgdb_info[cpu].debuggerinfo = NULL;
660 kgdb_info[cpu].task = NULL;
661 kgdb_info[cpu].exception_state &=
662 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
663 kgdb_info[cpu].enter_kgdb--;
664 smp_mb__before_atomic();
665 atomic_dec(&slaves_in_kgdb);
666 dbg_touch_watchdogs();
667 local_irq_restore(flags);
668 rcu_read_unlock();
669 return 0;
670 }
671 cpu_relax();
672 }
673
674 /*
675 * For single stepping, try to only enter on the processor
676 * that was single stepping. To guard against a deadlock, the
677 * kernel will only try for the value of sstep_tries before
678 * giving up and continuing on.
679 */
680 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
681 (kgdb_info[cpu].task &&
682 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
683 atomic_set(&kgdb_active, -1);
684 raw_spin_unlock(&dbg_master_lock);
685 dbg_touch_watchdogs();
686 local_irq_restore(flags);
687 rcu_read_unlock();
688
689 goto acquirelock;
690 }
691
692 if (!kgdb_io_ready(1)) {
693 kgdb_info[cpu].ret_state = 1;
694 goto kgdb_restore; /* No I/O connection, resume the system */
695 }
696
697 /*
698 * Don't enter if we have hit a removed breakpoint.
699 */
700 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
701 goto kgdb_restore;
702
703 atomic_inc(&ignore_console_lock_warning);
704
705 /* Call the I/O driver's pre_exception routine */
706 if (dbg_io_ops->pre_exception)
707 dbg_io_ops->pre_exception();
708
709 /*
710 * Get the passive CPU lock which will hold all the non-primary
711 * CPU in a spin state while the debugger is active
712 */
713 if (!kgdb_single_step)
714 raw_spin_lock(&dbg_slave_lock);
715
716#ifdef CONFIG_SMP
717 /* If send_ready set, slaves are already waiting */
718 if (ks->send_ready)
719 atomic_set(ks->send_ready, 1);
720
721 /* Signal the other CPUs to enter kgdb_wait() */
722 else if ((!kgdb_single_step) && kgdb_do_roundup)
723 kgdb_roundup_cpus();
724#endif
725
726 /*
727 * Wait for the other CPUs to be notified and be waiting for us:
728 */
729 time_left = MSEC_PER_SEC;
730 while (kgdb_do_roundup && --time_left &&
731 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
732 online_cpus)
733 udelay(1000);
734 if (!time_left)
735 pr_crit("Timed out waiting for secondary CPUs.\n");
736
737 /*
738 * At this point the primary processor is completely
739 * in the debugger and all secondary CPUs are quiescent
740 */
741 dbg_deactivate_sw_breakpoints();
742 kgdb_single_step = 0;
743 kgdb_contthread = current;
744 exception_level = 0;
745 trace_on = tracing_is_on();
746 if (trace_on)
747 tracing_off();
748
749 while (1) {
750cpu_master_loop:
751 if (dbg_kdb_mode) {
752 kgdb_connected = 1;
753 error = kdb_stub(ks);
754 if (error == -1)
755 continue;
756 kgdb_connected = 0;
757 } else {
758 error = gdb_serial_stub(ks);
759 }
760
761 if (error == DBG_PASS_EVENT) {
762 dbg_kdb_mode = !dbg_kdb_mode;
763 } else if (error == DBG_SWITCH_CPU_EVENT) {
764 kgdb_info[dbg_switch_cpu].exception_state |=
765 DCPU_NEXT_MASTER;
766 goto cpu_loop;
767 } else {
768 kgdb_info[cpu].ret_state = error;
769 break;
770 }
771 }
772
773 dbg_activate_sw_breakpoints();
774
775 /* Call the I/O driver's post_exception routine */
776 if (dbg_io_ops->post_exception)
777 dbg_io_ops->post_exception();
778
779 atomic_dec(&ignore_console_lock_warning);
780
781 if (!kgdb_single_step) {
782 raw_spin_unlock(&dbg_slave_lock);
783 /* Wait till all the CPUs have quit from the debugger. */
784 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
785 cpu_relax();
786 }
787
788kgdb_restore:
789 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
790 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
791 if (kgdb_info[sstep_cpu].task)
792 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
793 else
794 kgdb_sstep_pid = 0;
795 }
796 if (arch_kgdb_ops.correct_hw_break)
797 arch_kgdb_ops.correct_hw_break();
798 if (trace_on)
799 tracing_on();
800
801 kgdb_info[cpu].debuggerinfo = NULL;
802 kgdb_info[cpu].task = NULL;
803 kgdb_info[cpu].exception_state &=
804 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
805 kgdb_info[cpu].enter_kgdb--;
806 smp_mb__before_atomic();
807 atomic_dec(&masters_in_kgdb);
808 /* Free kgdb_active */
809 atomic_set(&kgdb_active, -1);
810 raw_spin_unlock(&dbg_master_lock);
811 dbg_touch_watchdogs();
812 local_irq_restore(flags);
813 rcu_read_unlock();
814
815 return kgdb_info[cpu].ret_state;
816}
817NOKPROBE_SYMBOL(kgdb_cpu_enter);
818
819/*
820 * kgdb_handle_exception() - main entry point from a kernel exception
821 *
822 * Locking hierarchy:
823 * interface locks, if any (begin_session)
824 * kgdb lock (kgdb_active)
825 */
826int
827kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
828{
829 struct kgdb_state kgdb_var;
830 struct kgdb_state *ks = &kgdb_var;
831 int ret = 0;
832
833 if (arch_kgdb_ops.enable_nmi)
834 arch_kgdb_ops.enable_nmi(0);
835 /*
836 * Avoid entering the debugger if we were triggered due to an oops
837 * but panic_timeout indicates the system should automatically
838 * reboot on panic. We don't want to get stuck waiting for input
839 * on such systems, especially if its "just" an oops.
840 */
841 if (signo != SIGTRAP && panic_timeout)
842 return 1;
843
844 memset(ks, 0, sizeof(struct kgdb_state));
845 ks->cpu = raw_smp_processor_id();
846 ks->ex_vector = evector;
847 ks->signo = signo;
848 ks->err_code = ecode;
849 ks->linux_regs = regs;
850
851 if (kgdb_reenter_check(ks))
852 goto out; /* Ouch, double exception ! */
853 if (kgdb_info[ks->cpu].enter_kgdb != 0)
854 goto out;
855
856 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
857out:
858 if (arch_kgdb_ops.enable_nmi)
859 arch_kgdb_ops.enable_nmi(1);
860 return ret;
861}
862NOKPROBE_SYMBOL(kgdb_handle_exception);
863
864/*
865 * GDB places a breakpoint at this function to know dynamically loaded objects.
866 */
867static int module_event(struct notifier_block *self, unsigned long val,
868 void *data)
869{
870 return 0;
871}
872
873static struct notifier_block dbg_module_load_nb = {
874 .notifier_call = module_event,
875};
876
877int kgdb_nmicallback(int cpu, void *regs)
878{
879#ifdef CONFIG_SMP
880 struct kgdb_state kgdb_var;
881 struct kgdb_state *ks = &kgdb_var;
882
883 kgdb_info[cpu].rounding_up = false;
884
885 memset(ks, 0, sizeof(struct kgdb_state));
886 ks->cpu = cpu;
887 ks->linux_regs = regs;
888
889 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
890 raw_spin_is_locked(&dbg_master_lock)) {
891 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
892 return 0;
893 }
894#endif
895 return 1;
896}
897NOKPROBE_SYMBOL(kgdb_nmicallback);
898
899int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
900 atomic_t *send_ready)
901{
902#ifdef CONFIG_SMP
903 if (!kgdb_io_ready(0) || !send_ready)
904 return 1;
905
906 if (kgdb_info[cpu].enter_kgdb == 0) {
907 struct kgdb_state kgdb_var;
908 struct kgdb_state *ks = &kgdb_var;
909
910 memset(ks, 0, sizeof(struct kgdb_state));
911 ks->cpu = cpu;
912 ks->ex_vector = trapnr;
913 ks->signo = SIGTRAP;
914 ks->err_code = err_code;
915 ks->linux_regs = regs;
916 ks->send_ready = send_ready;
917 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
918 return 0;
919 }
920#endif
921 return 1;
922}
923NOKPROBE_SYMBOL(kgdb_nmicallin);
924
925static void kgdb_console_write(struct console *co, const char *s,
926 unsigned count)
927{
928 unsigned long flags;
929
930 /* If we're debugging, or KGDB has not connected, don't try
931 * and print. */
932 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
933 return;
934
935 local_irq_save(flags);
936 gdbstub_msg_write(s, count);
937 local_irq_restore(flags);
938}
939
940static struct console kgdbcons = {
941 .name = "kgdb",
942 .write = kgdb_console_write,
943 .flags = CON_PRINTBUFFER | CON_ENABLED,
944 .index = -1,
945};
946
947static int __init opt_kgdb_con(char *str)
948{
949 kgdb_use_con = 1;
950
951 if (kgdb_io_module_registered && !kgdb_con_registered) {
952 register_console(&kgdbcons);
953 kgdb_con_registered = 1;
954 }
955
956 return 0;
957}
958
959early_param("kgdbcon", opt_kgdb_con);
960
961#ifdef CONFIG_MAGIC_SYSRQ
962static void sysrq_handle_dbg(int key)
963{
964 if (!dbg_io_ops) {
965 pr_crit("ERROR: No KGDB I/O module available\n");
966 return;
967 }
968 if (!kgdb_connected) {
969#ifdef CONFIG_KGDB_KDB
970 if (!dbg_kdb_mode)
971 pr_crit("KGDB or $3#33 for KDB\n");
972#else
973 pr_crit("Entering KGDB\n");
974#endif
975 }
976
977 kgdb_breakpoint();
978}
979
980static const struct sysrq_key_op sysrq_dbg_op = {
981 .handler = sysrq_handle_dbg,
982 .help_msg = "debug(g)",
983 .action_msg = "DEBUG",
984};
985#endif
986
987void kgdb_panic(const char *msg)
988{
989 if (!kgdb_io_module_registered)
990 return;
991
992 /*
993 * We don't want to get stuck waiting for input from user if
994 * "panic_timeout" indicates the system should automatically
995 * reboot on panic.
996 */
997 if (panic_timeout)
998 return;
999
1000 if (dbg_kdb_mode)
1001 kdb_printf("PANIC: %s\n", msg);
1002
1003 kgdb_breakpoint();
1004}
1005
1006static void kgdb_initial_breakpoint(void)
1007{
1008 kgdb_break_asap = 0;
1009
1010 pr_crit("Waiting for connection from remote gdb...\n");
1011 kgdb_breakpoint();
1012}
1013
1014void __weak kgdb_arch_late(void)
1015{
1016}
1017
1018void __init dbg_late_init(void)
1019{
1020 dbg_is_early = false;
1021 if (kgdb_io_module_registered)
1022 kgdb_arch_late();
1023 kdb_init(KDB_INIT_FULL);
1024
1025 if (kgdb_io_module_registered && kgdb_break_asap)
1026 kgdb_initial_breakpoint();
1027}
1028
1029static int
1030dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
1031{
1032 /*
1033 * Take the following action on reboot notify depending on value:
1034 * 1 == Enter debugger
1035 * 0 == [the default] detach debug client
1036 * -1 == Do nothing... and use this until the board resets
1037 */
1038 switch (kgdbreboot) {
1039 case 1:
1040 kgdb_breakpoint();
1041 goto done;
1042 case -1:
1043 goto done;
1044 }
1045 if (!dbg_kdb_mode)
1046 gdbstub_exit(code);
1047done:
1048 return NOTIFY_DONE;
1049}
1050
1051static struct notifier_block dbg_reboot_notifier = {
1052 .notifier_call = dbg_notify_reboot,
1053 .next = NULL,
1054 .priority = INT_MAX,
1055};
1056
1057static void kgdb_register_callbacks(void)
1058{
1059 if (!kgdb_io_module_registered) {
1060 kgdb_io_module_registered = 1;
1061 kgdb_arch_init();
1062 if (!dbg_is_early)
1063 kgdb_arch_late();
1064 register_module_notifier(&dbg_module_load_nb);
1065 register_reboot_notifier(&dbg_reboot_notifier);
1066#ifdef CONFIG_MAGIC_SYSRQ
1067 register_sysrq_key('g', &sysrq_dbg_op);
1068#endif
1069 if (kgdb_use_con && !kgdb_con_registered) {
1070 register_console(&kgdbcons);
1071 kgdb_con_registered = 1;
1072 }
1073 }
1074}
1075
1076static void kgdb_unregister_callbacks(void)
1077{
1078 /*
1079 * When this routine is called KGDB should unregister from
1080 * handlers and clean up, making sure it is not handling any
1081 * break exceptions at the time.
1082 */
1083 if (kgdb_io_module_registered) {
1084 kgdb_io_module_registered = 0;
1085 unregister_reboot_notifier(&dbg_reboot_notifier);
1086 unregister_module_notifier(&dbg_module_load_nb);
1087 kgdb_arch_exit();
1088#ifdef CONFIG_MAGIC_SYSRQ
1089 unregister_sysrq_key('g', &sysrq_dbg_op);
1090#endif
1091 if (kgdb_con_registered) {
1092 unregister_console(&kgdbcons);
1093 kgdb_con_registered = 0;
1094 }
1095 }
1096}
1097
1098/**
1099 * kgdb_register_io_module - register KGDB IO module
1100 * @new_dbg_io_ops: the io ops vector
1101 *
1102 * Register it with the KGDB core.
1103 */
1104int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
1105{
1106 struct kgdb_io *old_dbg_io_ops;
1107 int err;
1108
1109 spin_lock(&kgdb_registration_lock);
1110
1111 old_dbg_io_ops = dbg_io_ops;
1112 if (old_dbg_io_ops) {
1113 if (!old_dbg_io_ops->deinit) {
1114 spin_unlock(&kgdb_registration_lock);
1115
1116 pr_err("KGDB I/O driver %s can't replace %s.\n",
1117 new_dbg_io_ops->name, old_dbg_io_ops->name);
1118 return -EBUSY;
1119 }
1120 pr_info("Replacing I/O driver %s with %s\n",
1121 old_dbg_io_ops->name, new_dbg_io_ops->name);
1122 }
1123
1124 if (new_dbg_io_ops->init) {
1125 err = new_dbg_io_ops->init();
1126 if (err) {
1127 spin_unlock(&kgdb_registration_lock);
1128 return err;
1129 }
1130 }
1131
1132 dbg_io_ops = new_dbg_io_ops;
1133
1134 spin_unlock(&kgdb_registration_lock);
1135
1136 if (old_dbg_io_ops) {
1137 old_dbg_io_ops->deinit();
1138 return 0;
1139 }
1140
1141 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1142
1143 /* Arm KGDB now. */
1144 kgdb_register_callbacks();
1145
1146 if (kgdb_break_asap &&
1147 (!dbg_is_early || IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG)))
1148 kgdb_initial_breakpoint();
1149
1150 return 0;
1151}
1152EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1153
1154/**
1155 * kgdb_unregister_io_module - unregister KGDB IO module
1156 * @old_dbg_io_ops: the io ops vector
1157 *
1158 * Unregister it with the KGDB core.
1159 */
1160void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1161{
1162 BUG_ON(kgdb_connected);
1163
1164 /*
1165 * KGDB is no longer able to communicate out, so
1166 * unregister our callbacks and reset state.
1167 */
1168 kgdb_unregister_callbacks();
1169
1170 spin_lock(&kgdb_registration_lock);
1171
1172 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1173 dbg_io_ops = NULL;
1174
1175 spin_unlock(&kgdb_registration_lock);
1176
1177 if (old_dbg_io_ops->deinit)
1178 old_dbg_io_ops->deinit();
1179
1180 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1181 old_dbg_io_ops->name);
1182}
1183EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1184
1185int dbg_io_get_char(void)
1186{
1187 int ret = dbg_io_ops->read_char();
1188 if (ret == NO_POLL_CHAR)
1189 return -1;
1190 if (!dbg_kdb_mode)
1191 return ret;
1192 if (ret == 127)
1193 return 8;
1194 return ret;
1195}
1196
1197/**
1198 * kgdb_breakpoint - generate breakpoint exception
1199 *
1200 * This function will generate a breakpoint exception. It is used at the
1201 * beginning of a program to sync up with a debugger and can be used
1202 * otherwise as a quick means to stop program execution and "break" into
1203 * the debugger.
1204 */
1205noinline void kgdb_breakpoint(void)
1206{
1207 atomic_inc(&kgdb_setting_breakpoint);
1208 wmb(); /* Sync point before breakpoint */
1209 arch_kgdb_breakpoint();
1210 wmb(); /* Sync point after breakpoint */
1211 atomic_dec(&kgdb_setting_breakpoint);
1212}
1213EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1214
1215static int __init opt_kgdb_wait(char *str)
1216{
1217 kgdb_break_asap = 1;
1218
1219 kdb_init(KDB_INIT_EARLY);
1220 if (kgdb_io_module_registered &&
1221 IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG))
1222 kgdb_initial_breakpoint();
1223
1224 return 0;
1225}
1226
1227early_param("kgdbwait", opt_kgdb_wait);