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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// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Kernel Debug Core
4 *
5 * Maintainer: Jason Wessel <jason.wessel@windriver.com>
6 *
7 * Copyright (C) 2000-2001 VERITAS Software Corporation.
8 * Copyright (C) 2002-2004 Timesys Corporation
9 * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
10 * Copyright (C) 2004 Pavel Machek <pavel@ucw.cz>
11 * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
12 * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
13 * Copyright (C) 2005-2009 Wind River Systems, Inc.
14 * Copyright (C) 2007 MontaVista Software, Inc.
15 * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
16 *
17 * Contributors at various stages not listed above:
18 * Jason Wessel ( jason.wessel@windriver.com )
19 * George Anzinger <george@mvista.com>
20 * Anurekh Saxena (anurekh.saxena@timesys.com)
21 * Lake Stevens Instrument Division (Glenn Engel)
22 * Jim Kingdon, Cygnus Support.
23 *
24 * Original KGDB stub: David Grothe <dave@gcom.com>,
25 * Tigran Aivazian <tigran@sco.com>
26 */
27
28#define pr_fmt(fmt) "KGDB: " fmt
29
30#include <linux/pid_namespace.h>
31#include <linux/clocksource.h>
32#include <linux/serial_core.h>
33#include <linux/interrupt.h>
34#include <linux/spinlock.h>
35#include <linux/console.h>
36#include <linux/threads.h>
37#include <linux/uaccess.h>
38#include <linux/kernel.h>
39#include <linux/module.h>
40#include <linux/ptrace.h>
41#include <linux/string.h>
42#include <linux/delay.h>
43#include <linux/sched.h>
44#include <linux/sysrq.h>
45#include <linux/reboot.h>
46#include <linux/init.h>
47#include <linux/kgdb.h>
48#include <linux/kdb.h>
49#include <linux/nmi.h>
50#include <linux/pid.h>
51#include <linux/smp.h>
52#include <linux/mm.h>
53#include <linux/rcupdate.h>
54#include <linux/irq.h>
55#include <linux/security.h>
56
57#include <asm/cacheflush.h>
58#include <asm/byteorder.h>
59#include <linux/atomic.h>
60
61#include "debug_core.h"
62
63static int kgdb_break_asap;
64
65struct debuggerinfo_struct kgdb_info[NR_CPUS];
66
67/* kgdb_connected - Is a host GDB connected to us? */
68int kgdb_connected;
69EXPORT_SYMBOL_GPL(kgdb_connected);
70
71/* All the KGDB handlers are installed */
72int kgdb_io_module_registered;
73
74/* Guard for recursive entry */
75static int exception_level;
76
77struct kgdb_io *dbg_io_ops;
78static DEFINE_SPINLOCK(kgdb_registration_lock);
79
80/* Action for the reboot notifier, a global allow kdb to change it */
81static int kgdbreboot;
82/* kgdb console driver is loaded */
83static int kgdb_con_registered;
84/* determine if kgdb console output should be used */
85static int kgdb_use_con;
86/* Flag for alternate operations for early debugging */
87bool dbg_is_early = true;
88/* Next cpu to become the master debug core */
89int dbg_switch_cpu;
90
91/* Use kdb or gdbserver mode */
92int dbg_kdb_mode = 1;
93
94module_param(kgdb_use_con, int, 0644);
95module_param(kgdbreboot, int, 0644);
96
97/*
98 * Holds information about breakpoints in a kernel. These breakpoints are
99 * added and removed by gdb.
100 */
101static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
102 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
103};
104
105/*
106 * The CPU# of the active CPU, or -1 if none:
107 */
108atomic_t kgdb_active = ATOMIC_INIT(-1);
109EXPORT_SYMBOL_GPL(kgdb_active);
110static DEFINE_RAW_SPINLOCK(dbg_master_lock);
111static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
112
113/*
114 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
115 * bootup code (which might not have percpu set up yet):
116 */
117static atomic_t masters_in_kgdb;
118static atomic_t slaves_in_kgdb;
119atomic_t kgdb_setting_breakpoint;
120
121struct task_struct *kgdb_usethread;
122struct task_struct *kgdb_contthread;
123
124int kgdb_single_step;
125static pid_t kgdb_sstep_pid;
126
127/* to keep track of the CPU which is doing the single stepping*/
128atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
129
130/*
131 * If you are debugging a problem where roundup (the collection of
132 * all other CPUs) is a problem [this should be extremely rare],
133 * then use the nokgdbroundup option to avoid roundup. In that case
134 * the other CPUs might interfere with your debugging context, so
135 * use this with care:
136 */
137static int kgdb_do_roundup = 1;
138
139static int __init opt_nokgdbroundup(char *str)
140{
141 kgdb_do_roundup = 0;
142
143 return 0;
144}
145
146early_param("nokgdbroundup", opt_nokgdbroundup);
147
148/*
149 * Finally, some KGDB code :-)
150 */
151
152/*
153 * Weak aliases for breakpoint management,
154 * can be overridden by architectures when needed:
155 */
156int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
157{
158 int err;
159
160 err = copy_from_kernel_nofault(bpt->saved_instr, (char *)bpt->bpt_addr,
161 BREAK_INSTR_SIZE);
162 if (err)
163 return err;
164 err = copy_to_kernel_nofault((char *)bpt->bpt_addr,
165 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
166 return err;
167}
168NOKPROBE_SYMBOL(kgdb_arch_set_breakpoint);
169
170int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
171{
172 return copy_to_kernel_nofault((char *)bpt->bpt_addr,
173 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
174}
175NOKPROBE_SYMBOL(kgdb_arch_remove_breakpoint);
176
177int __weak kgdb_validate_break_address(unsigned long addr)
178{
179 struct kgdb_bkpt tmp;
180 int err;
181
182 if (kgdb_within_blocklist(addr))
183 return -EINVAL;
184
185 /* Validate setting the breakpoint and then removing it. If the
186 * remove fails, the kernel needs to emit a bad message because we
187 * are deep trouble not being able to put things back the way we
188 * found them.
189 */
190 tmp.bpt_addr = addr;
191 err = kgdb_arch_set_breakpoint(&tmp);
192 if (err)
193 return err;
194 err = kgdb_arch_remove_breakpoint(&tmp);
195 if (err)
196 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
197 addr);
198 return err;
199}
200
201unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
202{
203 return instruction_pointer(regs);
204}
205NOKPROBE_SYMBOL(kgdb_arch_pc);
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}
216NOKPROBE_SYMBOL(kgdb_skipexception);
217
218#ifdef CONFIG_SMP
219
220/*
221 * Default (weak) implementation for kgdb_roundup_cpus
222 */
223
224void __weak kgdb_call_nmi_hook(void *ignored)
225{
226 /*
227 * NOTE: get_irq_regs() is supposed to get the registers from
228 * before the IPI interrupt happened and so is supposed to
229 * show where the processor was. In some situations it's
230 * possible we might be called without an IPI, so it might be
231 * safer to figure out how to make kgdb_breakpoint() work
232 * properly here.
233 */
234 kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
235}
236NOKPROBE_SYMBOL(kgdb_call_nmi_hook);
237
238static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd) =
239 CSD_INIT(kgdb_call_nmi_hook, NULL);
240
241void __weak kgdb_roundup_cpus(void)
242{
243 call_single_data_t *csd;
244 int this_cpu = raw_smp_processor_id();
245 int cpu;
246 int ret;
247
248 for_each_online_cpu(cpu) {
249 /* No need to roundup ourselves */
250 if (cpu == this_cpu)
251 continue;
252
253 csd = &per_cpu(kgdb_roundup_csd, cpu);
254
255 /*
256 * If it didn't round up last time, don't try again
257 * since smp_call_function_single_async() will block.
258 *
259 * If rounding_up is false then we know that the
260 * previous call must have at least started and that
261 * means smp_call_function_single_async() won't block.
262 */
263 if (kgdb_info[cpu].rounding_up)
264 continue;
265 kgdb_info[cpu].rounding_up = true;
266
267 ret = smp_call_function_single_async(cpu, csd);
268 if (ret)
269 kgdb_info[cpu].rounding_up = false;
270 }
271}
272NOKPROBE_SYMBOL(kgdb_roundup_cpus);
273
274#endif
275
276/*
277 * Some architectures need cache flushes when we set/clear a
278 * breakpoint:
279 */
280static void kgdb_flush_swbreak_addr(unsigned long addr)
281{
282 if (!CACHE_FLUSH_IS_SAFE)
283 return;
284
285 /* Force flush instruction cache if it was outside the mm */
286 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
287}
288NOKPROBE_SYMBOL(kgdb_flush_swbreak_addr);
289
290/*
291 * SW breakpoint management:
292 */
293int dbg_activate_sw_breakpoints(void)
294{
295 int error;
296 int ret = 0;
297 int i;
298
299 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
300 if (kgdb_break[i].state != BP_SET)
301 continue;
302
303 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
304 if (error) {
305 ret = error;
306 pr_info("BP install failed: %lx\n",
307 kgdb_break[i].bpt_addr);
308 continue;
309 }
310
311 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
312 kgdb_break[i].state = BP_ACTIVE;
313 }
314 return ret;
315}
316NOKPROBE_SYMBOL(dbg_activate_sw_breakpoints);
317
318int dbg_set_sw_break(unsigned long addr)
319{
320 int err = kgdb_validate_break_address(addr);
321 int breakno = -1;
322 int i;
323
324 if (err)
325 return err;
326
327 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
328 if ((kgdb_break[i].state == BP_SET) &&
329 (kgdb_break[i].bpt_addr == addr))
330 return -EEXIST;
331 }
332 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
333 if (kgdb_break[i].state == BP_REMOVED &&
334 kgdb_break[i].bpt_addr == addr) {
335 breakno = i;
336 break;
337 }
338 }
339
340 if (breakno == -1) {
341 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
342 if (kgdb_break[i].state == BP_UNDEFINED) {
343 breakno = i;
344 break;
345 }
346 }
347 }
348
349 if (breakno == -1)
350 return -E2BIG;
351
352 kgdb_break[breakno].state = BP_SET;
353 kgdb_break[breakno].type = BP_BREAKPOINT;
354 kgdb_break[breakno].bpt_addr = addr;
355
356 return 0;
357}
358
359int dbg_deactivate_sw_breakpoints(void)
360{
361 int error;
362 int ret = 0;
363 int i;
364
365 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
366 if (kgdb_break[i].state != BP_ACTIVE)
367 continue;
368 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
369 if (error) {
370 pr_info("BP remove failed: %lx\n",
371 kgdb_break[i].bpt_addr);
372 ret = error;
373 }
374
375 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
376 kgdb_break[i].state = BP_SET;
377 }
378 return ret;
379}
380NOKPROBE_SYMBOL(dbg_deactivate_sw_breakpoints);
381
382int dbg_remove_sw_break(unsigned long addr)
383{
384 int i;
385
386 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
387 if ((kgdb_break[i].state == BP_SET) &&
388 (kgdb_break[i].bpt_addr == addr)) {
389 kgdb_break[i].state = BP_REMOVED;
390 return 0;
391 }
392 }
393 return -ENOENT;
394}
395
396int kgdb_isremovedbreak(unsigned long addr)
397{
398 int i;
399
400 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
401 if ((kgdb_break[i].state == BP_REMOVED) &&
402 (kgdb_break[i].bpt_addr == addr))
403 return 1;
404 }
405 return 0;
406}
407
408int kgdb_has_hit_break(unsigned long addr)
409{
410 int i;
411
412 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
413 if (kgdb_break[i].state == BP_ACTIVE &&
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
444void kgdb_free_init_mem(void)
445{
446 int i;
447
448 /* Clear init memory breakpoints. */
449 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
450 if (init_section_contains((void *)kgdb_break[i].bpt_addr, 0))
451 kgdb_break[i].state = BP_UNDEFINED;
452 }
453}
454
455#ifdef CONFIG_KGDB_KDB
456void kdb_dump_stack_on_cpu(int cpu)
457{
458 if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) {
459 dump_stack();
460 return;
461 }
462
463 if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) {
464 kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n",
465 cpu);
466 return;
467 }
468
469 /*
470 * In general, architectures don't support dumping the stack of a
471 * "running" process that's not the current one. From the point of
472 * view of the Linux, kernel processes that are looping in the kgdb
473 * slave loop are still "running". There's also no API (that actually
474 * works across all architectures) that can do a stack crawl based
475 * on registers passed as a parameter.
476 *
477 * Solve this conundrum by asking slave CPUs to do the backtrace
478 * themselves.
479 */
480 kgdb_info[cpu].exception_state |= DCPU_WANT_BT;
481 while (kgdb_info[cpu].exception_state & DCPU_WANT_BT)
482 cpu_relax();
483}
484#endif
485
486/*
487 * Return true if there is a valid kgdb I/O module. Also if no
488 * debugger is attached a message can be printed to the console about
489 * waiting for the debugger to attach.
490 *
491 * The print_wait argument is only to be true when called from inside
492 * the core kgdb_handle_exception, because it will wait for the
493 * debugger to attach.
494 */
495static int kgdb_io_ready(int print_wait)
496{
497 if (!dbg_io_ops)
498 return 0;
499 if (kgdb_connected)
500 return 1;
501 if (atomic_read(&kgdb_setting_breakpoint))
502 return 1;
503 if (print_wait) {
504#ifdef CONFIG_KGDB_KDB
505 if (!dbg_kdb_mode)
506 pr_crit("waiting... or $3#33 for KDB\n");
507#else
508 pr_crit("Waiting for remote debugger\n");
509#endif
510 }
511 return 1;
512}
513NOKPROBE_SYMBOL(kgdb_io_ready);
514
515static int kgdb_reenter_check(struct kgdb_state *ks)
516{
517 unsigned long addr;
518
519 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
520 return 0;
521
522 /* Panic on recursive debugger calls: */
523 exception_level++;
524 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
525 dbg_deactivate_sw_breakpoints();
526
527 /*
528 * If the break point removed ok at the place exception
529 * occurred, try to recover and print a warning to the end
530 * user because the user planted a breakpoint in a place that
531 * KGDB needs in order to function.
532 */
533 if (dbg_remove_sw_break(addr) == 0) {
534 exception_level = 0;
535 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
536 dbg_activate_sw_breakpoints();
537 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
538 WARN_ON_ONCE(1);
539
540 return 1;
541 }
542 dbg_remove_all_break();
543 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
544
545 if (exception_level > 1) {
546 dump_stack();
547 kgdb_io_module_registered = false;
548 panic("Recursive entry to debugger");
549 }
550
551 pr_crit("re-enter exception: ALL breakpoints killed\n");
552#ifdef CONFIG_KGDB_KDB
553 /* Allow kdb to debug itself one level */
554 return 0;
555#endif
556 dump_stack();
557 panic("Recursive entry to debugger");
558
559 return 1;
560}
561NOKPROBE_SYMBOL(kgdb_reenter_check);
562
563static void dbg_touch_watchdogs(void)
564{
565 touch_softlockup_watchdog_sync();
566 clocksource_touch_watchdog();
567 rcu_cpu_stall_reset();
568}
569NOKPROBE_SYMBOL(dbg_touch_watchdogs);
570
571static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
572 int exception_state)
573{
574 unsigned long flags;
575 int sstep_tries = 100;
576 int error;
577 int cpu;
578 int trace_on = 0;
579 int online_cpus = num_online_cpus();
580 u64 time_left;
581
582 kgdb_info[ks->cpu].enter_kgdb++;
583 kgdb_info[ks->cpu].exception_state |= exception_state;
584
585 if (exception_state == DCPU_WANT_MASTER)
586 atomic_inc(&masters_in_kgdb);
587 else
588 atomic_inc(&slaves_in_kgdb);
589
590 if (arch_kgdb_ops.disable_hw_break)
591 arch_kgdb_ops.disable_hw_break(regs);
592
593acquirelock:
594 rcu_read_lock();
595 /*
596 * Interrupts will be restored by the 'trap return' code, except when
597 * single stepping.
598 */
599 local_irq_save(flags);
600
601 cpu = ks->cpu;
602 kgdb_info[cpu].debuggerinfo = regs;
603 kgdb_info[cpu].task = current;
604 kgdb_info[cpu].ret_state = 0;
605 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
606
607 /* Make sure the above info reaches the primary CPU */
608 smp_mb();
609
610 if (exception_level == 1) {
611 if (raw_spin_trylock(&dbg_master_lock))
612 atomic_xchg(&kgdb_active, cpu);
613 goto cpu_master_loop;
614 }
615
616 /*
617 * CPU will loop if it is a slave or request to become a kgdb
618 * master cpu and acquire the kgdb_active lock:
619 */
620 while (1) {
621cpu_loop:
622 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
623 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
624 goto cpu_master_loop;
625 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
626 if (raw_spin_trylock(&dbg_master_lock)) {
627 atomic_xchg(&kgdb_active, cpu);
628 break;
629 }
630 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) {
631 dump_stack();
632 kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT;
633 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
634 if (!raw_spin_is_locked(&dbg_slave_lock))
635 goto return_normal;
636 } else {
637return_normal:
638 /* Return to normal operation by executing any
639 * hw breakpoint fixup.
640 */
641 if (arch_kgdb_ops.correct_hw_break)
642 arch_kgdb_ops.correct_hw_break();
643 if (trace_on)
644 tracing_on();
645 kgdb_info[cpu].debuggerinfo = NULL;
646 kgdb_info[cpu].task = NULL;
647 kgdb_info[cpu].exception_state &=
648 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
649 kgdb_info[cpu].enter_kgdb--;
650 smp_mb__before_atomic();
651 atomic_dec(&slaves_in_kgdb);
652 dbg_touch_watchdogs();
653 local_irq_restore(flags);
654 rcu_read_unlock();
655 return 0;
656 }
657 cpu_relax();
658 }
659
660 /*
661 * For single stepping, try to only enter on the processor
662 * that was single stepping. To guard against a deadlock, the
663 * kernel will only try for the value of sstep_tries before
664 * giving up and continuing on.
665 */
666 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
667 (kgdb_info[cpu].task &&
668 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
669 atomic_set(&kgdb_active, -1);
670 raw_spin_unlock(&dbg_master_lock);
671 dbg_touch_watchdogs();
672 local_irq_restore(flags);
673 rcu_read_unlock();
674
675 goto acquirelock;
676 }
677
678 if (!kgdb_io_ready(1)) {
679 kgdb_info[cpu].ret_state = 1;
680 goto kgdb_restore; /* No I/O connection, resume the system */
681 }
682
683 /*
684 * Don't enter if we have hit a removed breakpoint.
685 */
686 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
687 goto kgdb_restore;
688
689 atomic_inc(&ignore_console_lock_warning);
690
691 /* Call the I/O driver's pre_exception routine */
692 if (dbg_io_ops->pre_exception)
693 dbg_io_ops->pre_exception();
694
695 /*
696 * Get the passive CPU lock which will hold all the non-primary
697 * CPU in a spin state while the debugger is active
698 */
699 if (!kgdb_single_step)
700 raw_spin_lock(&dbg_slave_lock);
701
702#ifdef CONFIG_SMP
703 /* If send_ready set, slaves are already waiting */
704 if (ks->send_ready)
705 atomic_set(ks->send_ready, 1);
706
707 /* Signal the other CPUs to enter kgdb_wait() */
708 else if ((!kgdb_single_step) && kgdb_do_roundup)
709 kgdb_roundup_cpus();
710#endif
711
712 /*
713 * Wait for the other CPUs to be notified and be waiting for us:
714 */
715 time_left = MSEC_PER_SEC;
716 while (kgdb_do_roundup && --time_left &&
717 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
718 online_cpus)
719 udelay(1000);
720 if (!time_left)
721 pr_crit("Timed out waiting for secondary CPUs.\n");
722
723 /*
724 * At this point the primary processor is completely
725 * in the debugger and all secondary CPUs are quiescent
726 */
727 dbg_deactivate_sw_breakpoints();
728 kgdb_single_step = 0;
729 kgdb_contthread = current;
730 exception_level = 0;
731 trace_on = tracing_is_on();
732 if (trace_on)
733 tracing_off();
734
735 while (1) {
736cpu_master_loop:
737 if (dbg_kdb_mode) {
738 kgdb_connected = 1;
739 error = kdb_stub(ks);
740 if (error == -1)
741 continue;
742 kgdb_connected = 0;
743 } else {
744 /*
745 * This is a brutal way to interfere with the debugger
746 * and prevent gdb being used to poke at kernel memory.
747 * This could cause trouble if lockdown is applied when
748 * there is already an active gdb session. For now the
749 * answer is simply "don't do that". Typically lockdown
750 * *will* be applied before the debug core gets started
751 * so only developers using kgdb for fairly advanced
752 * early kernel debug can be biten by this. Hopefully
753 * they are sophisticated enough to take care of
754 * themselves, especially with help from the lockdown
755 * message printed on the console!
756 */
757 if (security_locked_down(LOCKDOWN_DBG_WRITE_KERNEL)) {
758 if (IS_ENABLED(CONFIG_KGDB_KDB)) {
759 /* Switch back to kdb if possible... */
760 dbg_kdb_mode = 1;
761 continue;
762 } else {
763 /* ... otherwise just bail */
764 break;
765 }
766 }
767 error = gdb_serial_stub(ks);
768 }
769
770 if (error == DBG_PASS_EVENT) {
771 dbg_kdb_mode = !dbg_kdb_mode;
772 } else if (error == DBG_SWITCH_CPU_EVENT) {
773 kgdb_info[dbg_switch_cpu].exception_state |=
774 DCPU_NEXT_MASTER;
775 goto cpu_loop;
776 } else {
777 kgdb_info[cpu].ret_state = error;
778 break;
779 }
780 }
781
782 dbg_activate_sw_breakpoints();
783
784 /* Call the I/O driver's post_exception routine */
785 if (dbg_io_ops->post_exception)
786 dbg_io_ops->post_exception();
787
788 atomic_dec(&ignore_console_lock_warning);
789
790 if (!kgdb_single_step) {
791 raw_spin_unlock(&dbg_slave_lock);
792 /* Wait till all the CPUs have quit from the debugger. */
793 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
794 cpu_relax();
795 }
796
797kgdb_restore:
798 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
799 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
800 if (kgdb_info[sstep_cpu].task)
801 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
802 else
803 kgdb_sstep_pid = 0;
804 }
805 if (arch_kgdb_ops.correct_hw_break)
806 arch_kgdb_ops.correct_hw_break();
807 if (trace_on)
808 tracing_on();
809
810 kgdb_info[cpu].debuggerinfo = NULL;
811 kgdb_info[cpu].task = NULL;
812 kgdb_info[cpu].exception_state &=
813 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
814 kgdb_info[cpu].enter_kgdb--;
815 smp_mb__before_atomic();
816 atomic_dec(&masters_in_kgdb);
817 /* Free kgdb_active */
818 atomic_set(&kgdb_active, -1);
819 raw_spin_unlock(&dbg_master_lock);
820 dbg_touch_watchdogs();
821 local_irq_restore(flags);
822 rcu_read_unlock();
823
824 return kgdb_info[cpu].ret_state;
825}
826NOKPROBE_SYMBOL(kgdb_cpu_enter);
827
828/*
829 * kgdb_handle_exception() - main entry point from a kernel exception
830 *
831 * Locking hierarchy:
832 * interface locks, if any (begin_session)
833 * kgdb lock (kgdb_active)
834 */
835int
836kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
837{
838 struct kgdb_state kgdb_var;
839 struct kgdb_state *ks = &kgdb_var;
840 int ret = 0;
841
842 if (arch_kgdb_ops.enable_nmi)
843 arch_kgdb_ops.enable_nmi(0);
844 /*
845 * Avoid entering the debugger if we were triggered due to an oops
846 * but panic_timeout indicates the system should automatically
847 * reboot on panic. We don't want to get stuck waiting for input
848 * on such systems, especially if its "just" an oops.
849 */
850 if (signo != SIGTRAP && panic_timeout)
851 return 1;
852
853 memset(ks, 0, sizeof(struct kgdb_state));
854 ks->cpu = raw_smp_processor_id();
855 ks->ex_vector = evector;
856 ks->signo = signo;
857 ks->err_code = ecode;
858 ks->linux_regs = regs;
859
860 if (kgdb_reenter_check(ks))
861 goto out; /* Ouch, double exception ! */
862 if (kgdb_info[ks->cpu].enter_kgdb != 0)
863 goto out;
864
865 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
866out:
867 if (arch_kgdb_ops.enable_nmi)
868 arch_kgdb_ops.enable_nmi(1);
869 return ret;
870}
871NOKPROBE_SYMBOL(kgdb_handle_exception);
872
873/*
874 * GDB places a breakpoint at this function to know dynamically loaded objects.
875 */
876static int module_event(struct notifier_block *self, unsigned long val,
877 void *data)
878{
879 return 0;
880}
881
882static struct notifier_block dbg_module_load_nb = {
883 .notifier_call = module_event,
884};
885
886int kgdb_nmicallback(int cpu, void *regs)
887{
888#ifdef CONFIG_SMP
889 struct kgdb_state kgdb_var;
890 struct kgdb_state *ks = &kgdb_var;
891
892 kgdb_info[cpu].rounding_up = false;
893
894 memset(ks, 0, sizeof(struct kgdb_state));
895 ks->cpu = cpu;
896 ks->linux_regs = regs;
897
898 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
899 raw_spin_is_locked(&dbg_master_lock)) {
900 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
901 return 0;
902 }
903#endif
904 return 1;
905}
906NOKPROBE_SYMBOL(kgdb_nmicallback);
907
908int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
909 atomic_t *send_ready)
910{
911#ifdef CONFIG_SMP
912 if (!kgdb_io_ready(0) || !send_ready)
913 return 1;
914
915 if (kgdb_info[cpu].enter_kgdb == 0) {
916 struct kgdb_state kgdb_var;
917 struct kgdb_state *ks = &kgdb_var;
918
919 memset(ks, 0, sizeof(struct kgdb_state));
920 ks->cpu = cpu;
921 ks->ex_vector = trapnr;
922 ks->signo = SIGTRAP;
923 ks->err_code = err_code;
924 ks->linux_regs = regs;
925 ks->send_ready = send_ready;
926 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
927 return 0;
928 }
929#endif
930 return 1;
931}
932NOKPROBE_SYMBOL(kgdb_nmicallin);
933
934static void kgdb_console_write(struct console *co, const char *s,
935 unsigned count)
936{
937 unsigned long flags;
938
939 /* If we're debugging, or KGDB has not connected, don't try
940 * and print. */
941 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
942 return;
943
944 local_irq_save(flags);
945 gdbstub_msg_write(s, count);
946 local_irq_restore(flags);
947}
948
949static struct console kgdbcons = {
950 .name = "kgdb",
951 .write = kgdb_console_write,
952 .flags = CON_PRINTBUFFER | CON_ENABLED,
953 .index = -1,
954};
955
956static int __init opt_kgdb_con(char *str)
957{
958 kgdb_use_con = 1;
959
960 if (kgdb_io_module_registered && !kgdb_con_registered) {
961 register_console(&kgdbcons);
962 kgdb_con_registered = 1;
963 }
964
965 return 0;
966}
967
968early_param("kgdbcon", opt_kgdb_con);
969
970#ifdef CONFIG_MAGIC_SYSRQ
971static void sysrq_handle_dbg(int key)
972{
973 if (!dbg_io_ops) {
974 pr_crit("ERROR: No KGDB I/O module available\n");
975 return;
976 }
977 if (!kgdb_connected) {
978#ifdef CONFIG_KGDB_KDB
979 if (!dbg_kdb_mode)
980 pr_crit("KGDB or $3#33 for KDB\n");
981#else
982 pr_crit("Entering KGDB\n");
983#endif
984 }
985
986 kgdb_breakpoint();
987}
988
989static const struct sysrq_key_op sysrq_dbg_op = {
990 .handler = sysrq_handle_dbg,
991 .help_msg = "debug(g)",
992 .action_msg = "DEBUG",
993};
994#endif
995
996void kgdb_panic(const char *msg)
997{
998 if (!kgdb_io_module_registered)
999 return;
1000
1001 /*
1002 * We don't want to get stuck waiting for input from user if
1003 * "panic_timeout" indicates the system should automatically
1004 * reboot on panic.
1005 */
1006 if (panic_timeout)
1007 return;
1008
1009 if (dbg_kdb_mode)
1010 kdb_printf("PANIC: %s\n", msg);
1011
1012 kgdb_breakpoint();
1013}
1014
1015static void kgdb_initial_breakpoint(void)
1016{
1017 kgdb_break_asap = 0;
1018
1019 pr_crit("Waiting for connection from remote gdb...\n");
1020 kgdb_breakpoint();
1021}
1022
1023void __weak kgdb_arch_late(void)
1024{
1025}
1026
1027void __init dbg_late_init(void)
1028{
1029 dbg_is_early = false;
1030 if (kgdb_io_module_registered)
1031 kgdb_arch_late();
1032 kdb_init(KDB_INIT_FULL);
1033
1034 if (kgdb_io_module_registered && kgdb_break_asap)
1035 kgdb_initial_breakpoint();
1036}
1037
1038static int
1039dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
1040{
1041 /*
1042 * Take the following action on reboot notify depending on value:
1043 * 1 == Enter debugger
1044 * 0 == [the default] detach debug client
1045 * -1 == Do nothing... and use this until the board resets
1046 */
1047 switch (kgdbreboot) {
1048 case 1:
1049 kgdb_breakpoint();
1050 goto done;
1051 case -1:
1052 goto done;
1053 }
1054 if (!dbg_kdb_mode)
1055 gdbstub_exit(code);
1056done:
1057 return NOTIFY_DONE;
1058}
1059
1060static struct notifier_block dbg_reboot_notifier = {
1061 .notifier_call = dbg_notify_reboot,
1062 .next = NULL,
1063 .priority = INT_MAX,
1064};
1065
1066static void kgdb_register_callbacks(void)
1067{
1068 if (!kgdb_io_module_registered) {
1069 kgdb_io_module_registered = 1;
1070 kgdb_arch_init();
1071 if (!dbg_is_early)
1072 kgdb_arch_late();
1073 register_module_notifier(&dbg_module_load_nb);
1074 register_reboot_notifier(&dbg_reboot_notifier);
1075#ifdef CONFIG_MAGIC_SYSRQ
1076 register_sysrq_key('g', &sysrq_dbg_op);
1077#endif
1078 if (kgdb_use_con && !kgdb_con_registered) {
1079 register_console(&kgdbcons);
1080 kgdb_con_registered = 1;
1081 }
1082 }
1083}
1084
1085static void kgdb_unregister_callbacks(void)
1086{
1087 /*
1088 * When this routine is called KGDB should unregister from
1089 * handlers and clean up, making sure it is not handling any
1090 * break exceptions at the time.
1091 */
1092 if (kgdb_io_module_registered) {
1093 kgdb_io_module_registered = 0;
1094 unregister_reboot_notifier(&dbg_reboot_notifier);
1095 unregister_module_notifier(&dbg_module_load_nb);
1096 kgdb_arch_exit();
1097#ifdef CONFIG_MAGIC_SYSRQ
1098 unregister_sysrq_key('g', &sysrq_dbg_op);
1099#endif
1100 if (kgdb_con_registered) {
1101 unregister_console(&kgdbcons);
1102 kgdb_con_registered = 0;
1103 }
1104 }
1105}
1106
1107/**
1108 * kgdb_register_io_module - register KGDB IO module
1109 * @new_dbg_io_ops: the io ops vector
1110 *
1111 * Register it with the KGDB core.
1112 */
1113int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
1114{
1115 struct kgdb_io *old_dbg_io_ops;
1116 int err;
1117
1118 spin_lock(&kgdb_registration_lock);
1119
1120 old_dbg_io_ops = dbg_io_ops;
1121 if (old_dbg_io_ops) {
1122 if (!old_dbg_io_ops->deinit) {
1123 spin_unlock(&kgdb_registration_lock);
1124
1125 pr_err("KGDB I/O driver %s can't replace %s.\n",
1126 new_dbg_io_ops->name, old_dbg_io_ops->name);
1127 return -EBUSY;
1128 }
1129 pr_info("Replacing I/O driver %s with %s\n",
1130 old_dbg_io_ops->name, new_dbg_io_ops->name);
1131 }
1132
1133 if (new_dbg_io_ops->init) {
1134 err = new_dbg_io_ops->init();
1135 if (err) {
1136 spin_unlock(&kgdb_registration_lock);
1137 return err;
1138 }
1139 }
1140
1141 dbg_io_ops = new_dbg_io_ops;
1142
1143 spin_unlock(&kgdb_registration_lock);
1144
1145 if (old_dbg_io_ops) {
1146 old_dbg_io_ops->deinit();
1147 return 0;
1148 }
1149
1150 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1151
1152 /* Arm KGDB now. */
1153 kgdb_register_callbacks();
1154
1155 if (kgdb_break_asap &&
1156 (!dbg_is_early || IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG)))
1157 kgdb_initial_breakpoint();
1158
1159 return 0;
1160}
1161EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1162
1163/**
1164 * kgdb_unregister_io_module - unregister KGDB IO module
1165 * @old_dbg_io_ops: the io ops vector
1166 *
1167 * Unregister it with the KGDB core.
1168 */
1169void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1170{
1171 BUG_ON(kgdb_connected);
1172
1173 /*
1174 * KGDB is no longer able to communicate out, so
1175 * unregister our callbacks and reset state.
1176 */
1177 kgdb_unregister_callbacks();
1178
1179 spin_lock(&kgdb_registration_lock);
1180
1181 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1182 dbg_io_ops = NULL;
1183
1184 spin_unlock(&kgdb_registration_lock);
1185
1186 if (old_dbg_io_ops->deinit)
1187 old_dbg_io_ops->deinit();
1188
1189 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1190 old_dbg_io_ops->name);
1191}
1192EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1193
1194int dbg_io_get_char(void)
1195{
1196 int ret = dbg_io_ops->read_char();
1197 if (ret == NO_POLL_CHAR)
1198 return -1;
1199 if (!dbg_kdb_mode)
1200 return ret;
1201 if (ret == 127)
1202 return 8;
1203 return ret;
1204}
1205
1206/**
1207 * kgdb_breakpoint - generate breakpoint exception
1208 *
1209 * This function will generate a breakpoint exception. It is used at the
1210 * beginning of a program to sync up with a debugger and can be used
1211 * otherwise as a quick means to stop program execution and "break" into
1212 * the debugger.
1213 */
1214noinline void kgdb_breakpoint(void)
1215{
1216 atomic_inc(&kgdb_setting_breakpoint);
1217 wmb(); /* Sync point before breakpoint */
1218 arch_kgdb_breakpoint();
1219 wmb(); /* Sync point after breakpoint */
1220 atomic_dec(&kgdb_setting_breakpoint);
1221}
1222EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1223
1224static int __init opt_kgdb_wait(char *str)
1225{
1226 kgdb_break_asap = 1;
1227
1228 kdb_init(KDB_INIT_EARLY);
1229 if (kgdb_io_module_registered &&
1230 IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG))
1231 kgdb_initial_breakpoint();
1232
1233 return 0;
1234}
1235
1236early_param("kgdbwait", opt_kgdb_wait);