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