forked from torvalds/linux
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathdebug_core.c
More file actions
1236 lines (1060 loc) · 29.1 KB
/
debug_core.c
File metadata and controls
1236 lines (1060 loc) · 29.1 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
// SPDX-License-Identifier: GPL-2.0-only
/*
* Kernel Debug Core
*
* Maintainer: Jason Wessel <jason.wessel@windriver.com>
*
* Copyright (C) 2000-2001 VERITAS Software Corporation.
* Copyright (C) 2002-2004 Timesys Corporation
* Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
* Copyright (C) 2004 Pavel Machek <pavel@ucw.cz>
* Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
* Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
* Copyright (C) 2005-2009 Wind River Systems, Inc.
* Copyright (C) 2007 MontaVista Software, Inc.
* Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
*
* Contributors at various stages not listed above:
* Jason Wessel ( jason.wessel@windriver.com )
* George Anzinger <george@mvista.com>
* Anurekh Saxena (anurekh.saxena@timesys.com)
* Lake Stevens Instrument Division (Glenn Engel)
* Jim Kingdon, Cygnus Support.
*
* Original KGDB stub: David Grothe <dave@gcom.com>,
* Tigran Aivazian <tigran@sco.com>
*/
#define pr_fmt(fmt) "KGDB: " fmt
#include <linux/pid_namespace.h>
#include <linux/clocksource.h>
#include <linux/serial_core.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/console.h>
#include <linux/threads.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/string.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/sysrq.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/kgdb.h>
#include <linux/kdb.h>
#include <linux/nmi.h>
#include <linux/pid.h>
#include <linux/smp.h>
#include <linux/mm.h>
#include <linux/rcupdate.h>
#include <linux/irq.h>
#include <linux/security.h>
#include <asm/cacheflush.h>
#include <asm/byteorder.h>
#include <linux/atomic.h>
#include "debug_core.h"
static int kgdb_break_asap;
struct debuggerinfo_struct kgdb_info[NR_CPUS];
/* kgdb_connected - Is a host GDB connected to us? */
int kgdb_connected;
EXPORT_SYMBOL_GPL(kgdb_connected);
/* All the KGDB handlers are installed */
int kgdb_io_module_registered;
/* Guard for recursive entry */
static int exception_level;
struct kgdb_io *dbg_io_ops;
static DEFINE_SPINLOCK(kgdb_registration_lock);
/* Action for the reboot notifier, a global allow kdb to change it */
static int kgdbreboot;
/* kgdb console driver is loaded */
static int kgdb_con_registered;
/* determine if kgdb console output should be used */
static int kgdb_use_con;
/* Flag for alternate operations for early debugging */
bool dbg_is_early = true;
/* Next cpu to become the master debug core */
int dbg_switch_cpu;
/* Use kdb or gdbserver mode */
int dbg_kdb_mode = 1;
module_param(kgdb_use_con, int, 0644);
module_param(kgdbreboot, int, 0644);
/*
* Holds information about breakpoints in a kernel. These breakpoints are
* added and removed by gdb.
*/
static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
[0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
};
/*
* The CPU# of the active CPU, or -1 if none:
*/
atomic_t kgdb_active = ATOMIC_INIT(-1);
EXPORT_SYMBOL_GPL(kgdb_active);
static DEFINE_RAW_SPINLOCK(dbg_master_lock);
static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
/*
* We use NR_CPUs not PERCPU, in case kgdb is used to debug early
* bootup code (which might not have percpu set up yet):
*/
static atomic_t masters_in_kgdb;
static atomic_t slaves_in_kgdb;
atomic_t kgdb_setting_breakpoint;
struct task_struct *kgdb_usethread;
struct task_struct *kgdb_contthread;
int kgdb_single_step;
static pid_t kgdb_sstep_pid;
/* to keep track of the CPU which is doing the single stepping*/
atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
/*
* If you are debugging a problem where roundup (the collection of
* all other CPUs) is a problem [this should be extremely rare],
* then use the nokgdbroundup option to avoid roundup. In that case
* the other CPUs might interfere with your debugging context, so
* use this with care:
*/
static int kgdb_do_roundup = 1;
static int __init opt_nokgdbroundup(char *str)
{
kgdb_do_roundup = 0;
return 0;
}
early_param("nokgdbroundup", opt_nokgdbroundup);
/*
* Finally, some KGDB code :-)
*/
/*
* Weak aliases for breakpoint management,
* can be overridden by architectures when needed:
*/
int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
{
int err;
err = copy_from_kernel_nofault(bpt->saved_instr, (char *)bpt->bpt_addr,
BREAK_INSTR_SIZE);
if (err)
return err;
err = copy_to_kernel_nofault((char *)bpt->bpt_addr,
arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
return err;
}
NOKPROBE_SYMBOL(kgdb_arch_set_breakpoint);
int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
{
return copy_to_kernel_nofault((char *)bpt->bpt_addr,
(char *)bpt->saved_instr, BREAK_INSTR_SIZE);
}
NOKPROBE_SYMBOL(kgdb_arch_remove_breakpoint);
int __weak kgdb_validate_break_address(unsigned long addr)
{
struct kgdb_bkpt tmp;
int err;
if (kgdb_within_blocklist(addr))
return -EINVAL;
/* Validate setting the breakpoint and then removing it. If the
* remove fails, the kernel needs to emit a bad message because we
* are deep trouble not being able to put things back the way we
* found them.
*/
tmp.bpt_addr = addr;
err = kgdb_arch_set_breakpoint(&tmp);
if (err)
return err;
err = kgdb_arch_remove_breakpoint(&tmp);
if (err)
pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
addr);
return err;
}
unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
{
return instruction_pointer(regs);
}
NOKPROBE_SYMBOL(kgdb_arch_pc);
int __weak kgdb_arch_init(void)
{
return 0;
}
int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
{
return 0;
}
NOKPROBE_SYMBOL(kgdb_skipexception);
#ifdef CONFIG_SMP
/*
* Default (weak) implementation for kgdb_roundup_cpus
*/
void __weak kgdb_call_nmi_hook(void *ignored)
{
/*
* NOTE: get_irq_regs() is supposed to get the registers from
* before the IPI interrupt happened and so is supposed to
* show where the processor was. In some situations it's
* possible we might be called without an IPI, so it might be
* safer to figure out how to make kgdb_breakpoint() work
* properly here.
*/
kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
}
NOKPROBE_SYMBOL(kgdb_call_nmi_hook);
static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd) =
CSD_INIT(kgdb_call_nmi_hook, NULL);
void __weak kgdb_roundup_cpus(void)
{
call_single_data_t *csd;
int this_cpu = raw_smp_processor_id();
int cpu;
int ret;
for_each_online_cpu(cpu) {
/* No need to roundup ourselves */
if (cpu == this_cpu)
continue;
csd = &per_cpu(kgdb_roundup_csd, cpu);
/*
* If it didn't round up last time, don't try again
* since smp_call_function_single_async() will block.
*
* If rounding_up is false then we know that the
* previous call must have at least started and that
* means smp_call_function_single_async() won't block.
*/
if (kgdb_info[cpu].rounding_up)
continue;
kgdb_info[cpu].rounding_up = true;
ret = smp_call_function_single_async(cpu, csd);
if (ret)
kgdb_info[cpu].rounding_up = false;
}
}
NOKPROBE_SYMBOL(kgdb_roundup_cpus);
#endif
/*
* Some architectures need cache flushes when we set/clear a
* breakpoint:
*/
static void kgdb_flush_swbreak_addr(unsigned long addr)
{
if (!CACHE_FLUSH_IS_SAFE)
return;
/* Force flush instruction cache if it was outside the mm */
flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
}
NOKPROBE_SYMBOL(kgdb_flush_swbreak_addr);
/*
* SW breakpoint management:
*/
int dbg_activate_sw_breakpoints(void)
{
int error;
int ret = 0;
int i;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state != BP_SET)
continue;
error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
if (error) {
ret = error;
pr_info("BP install failed: %lx\n",
kgdb_break[i].bpt_addr);
continue;
}
kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
kgdb_break[i].state = BP_ACTIVE;
}
return ret;
}
NOKPROBE_SYMBOL(dbg_activate_sw_breakpoints);
int dbg_set_sw_break(unsigned long addr)
{
int err = kgdb_validate_break_address(addr);
int breakno = -1;
int i;
if (err)
return err;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if ((kgdb_break[i].state == BP_SET) &&
(kgdb_break[i].bpt_addr == addr))
return -EEXIST;
}
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state == BP_REMOVED &&
kgdb_break[i].bpt_addr == addr) {
breakno = i;
break;
}
}
if (breakno == -1) {
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state == BP_UNDEFINED) {
breakno = i;
break;
}
}
}
if (breakno == -1)
return -E2BIG;
kgdb_break[breakno].state = BP_SET;
kgdb_break[breakno].type = BP_BREAKPOINT;
kgdb_break[breakno].bpt_addr = addr;
return 0;
}
int dbg_deactivate_sw_breakpoints(void)
{
int error;
int ret = 0;
int i;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state != BP_ACTIVE)
continue;
error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
if (error) {
pr_info("BP remove failed: %lx\n",
kgdb_break[i].bpt_addr);
ret = error;
}
kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
kgdb_break[i].state = BP_SET;
}
return ret;
}
NOKPROBE_SYMBOL(dbg_deactivate_sw_breakpoints);
int dbg_remove_sw_break(unsigned long addr)
{
int i;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if ((kgdb_break[i].state == BP_SET) &&
(kgdb_break[i].bpt_addr == addr)) {
kgdb_break[i].state = BP_REMOVED;
return 0;
}
}
return -ENOENT;
}
int kgdb_isremovedbreak(unsigned long addr)
{
int i;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if ((kgdb_break[i].state == BP_REMOVED) &&
(kgdb_break[i].bpt_addr == addr))
return 1;
}
return 0;
}
int kgdb_has_hit_break(unsigned long addr)
{
int i;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state == BP_ACTIVE &&
kgdb_break[i].bpt_addr == addr)
return 1;
}
return 0;
}
int dbg_remove_all_break(void)
{
int error;
int i;
/* Clear memory breakpoints. */
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state != BP_ACTIVE)
goto setundefined;
error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
if (error)
pr_err("breakpoint remove failed: %lx\n",
kgdb_break[i].bpt_addr);
setundefined:
kgdb_break[i].state = BP_UNDEFINED;
}
/* Clear hardware breakpoints. */
if (arch_kgdb_ops.remove_all_hw_break)
arch_kgdb_ops.remove_all_hw_break();
return 0;
}
void kgdb_free_init_mem(void)
{
int i;
/* Clear init memory breakpoints. */
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (init_section_contains((void *)kgdb_break[i].bpt_addr, 0))
kgdb_break[i].state = BP_UNDEFINED;
}
}
#ifdef CONFIG_KGDB_KDB
void kdb_dump_stack_on_cpu(int cpu)
{
if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) {
dump_stack();
return;
}
if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) {
kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n",
cpu);
return;
}
/*
* In general, architectures don't support dumping the stack of a
* "running" process that's not the current one. From the point of
* view of the Linux, kernel processes that are looping in the kgdb
* slave loop are still "running". There's also no API (that actually
* works across all architectures) that can do a stack crawl based
* on registers passed as a parameter.
*
* Solve this conundrum by asking slave CPUs to do the backtrace
* themselves.
*/
kgdb_info[cpu].exception_state |= DCPU_WANT_BT;
while (kgdb_info[cpu].exception_state & DCPU_WANT_BT)
cpu_relax();
}
#endif
/*
* Return true if there is a valid kgdb I/O module. Also if no
* debugger is attached a message can be printed to the console about
* waiting for the debugger to attach.
*
* The print_wait argument is only to be true when called from inside
* the core kgdb_handle_exception, because it will wait for the
* debugger to attach.
*/
static int kgdb_io_ready(int print_wait)
{
if (!dbg_io_ops)
return 0;
if (kgdb_connected)
return 1;
if (atomic_read(&kgdb_setting_breakpoint))
return 1;
if (print_wait) {
#ifdef CONFIG_KGDB_KDB
if (!dbg_kdb_mode)
pr_crit("waiting... or $3#33 for KDB\n");
#else
pr_crit("Waiting for remote debugger\n");
#endif
}
return 1;
}
NOKPROBE_SYMBOL(kgdb_io_ready);
static int kgdb_reenter_check(struct kgdb_state *ks)
{
unsigned long addr;
if (atomic_read(&kgdb_active) != raw_smp_processor_id())
return 0;
/* Panic on recursive debugger calls: */
exception_level++;
addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
dbg_deactivate_sw_breakpoints();
/*
* If the break point removed ok at the place exception
* occurred, try to recover and print a warning to the end
* user because the user planted a breakpoint in a place that
* KGDB needs in order to function.
*/
if (dbg_remove_sw_break(addr) == 0) {
exception_level = 0;
kgdb_skipexception(ks->ex_vector, ks->linux_regs);
dbg_activate_sw_breakpoints();
pr_crit("re-enter error: breakpoint removed %lx\n", addr);
WARN_ON_ONCE(1);
return 1;
}
dbg_remove_all_break();
kgdb_skipexception(ks->ex_vector, ks->linux_regs);
if (exception_level > 1) {
dump_stack();
kgdb_io_module_registered = false;
panic("Recursive entry to debugger");
}
pr_crit("re-enter exception: ALL breakpoints killed\n");
#ifdef CONFIG_KGDB_KDB
/* Allow kdb to debug itself one level */
return 0;
#endif
dump_stack();
panic("Recursive entry to debugger");
return 1;
}
NOKPROBE_SYMBOL(kgdb_reenter_check);
static void dbg_touch_watchdogs(void)
{
touch_softlockup_watchdog_sync();
clocksource_touch_watchdog();
rcu_cpu_stall_reset();
}
NOKPROBE_SYMBOL(dbg_touch_watchdogs);
static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
int exception_state)
{
unsigned long flags;
int sstep_tries = 100;
int error;
int cpu;
int trace_on = 0;
int online_cpus = num_online_cpus();
u64 time_left;
kgdb_info[ks->cpu].enter_kgdb++;
kgdb_info[ks->cpu].exception_state |= exception_state;
if (exception_state == DCPU_WANT_MASTER)
atomic_inc(&masters_in_kgdb);
else
atomic_inc(&slaves_in_kgdb);
if (arch_kgdb_ops.disable_hw_break)
arch_kgdb_ops.disable_hw_break(regs);
acquirelock:
rcu_read_lock();
/*
* Interrupts will be restored by the 'trap return' code, except when
* single stepping.
*/
local_irq_save(flags);
cpu = ks->cpu;
kgdb_info[cpu].debuggerinfo = regs;
kgdb_info[cpu].task = current;
kgdb_info[cpu].ret_state = 0;
kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
/* Make sure the above info reaches the primary CPU */
smp_mb();
if (exception_level == 1) {
if (raw_spin_trylock(&dbg_master_lock))
atomic_xchg(&kgdb_active, cpu);
goto cpu_master_loop;
}
/*
* CPU will loop if it is a slave or request to become a kgdb
* master cpu and acquire the kgdb_active lock:
*/
while (1) {
cpu_loop:
if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
goto cpu_master_loop;
} else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
if (raw_spin_trylock(&dbg_master_lock)) {
atomic_xchg(&kgdb_active, cpu);
break;
}
} else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) {
dump_stack();
kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT;
} else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
if (!raw_spin_is_locked(&dbg_slave_lock))
goto return_normal;
} else {
return_normal:
/* Return to normal operation by executing any
* hw breakpoint fixup.
*/
if (arch_kgdb_ops.correct_hw_break)
arch_kgdb_ops.correct_hw_break();
if (trace_on)
tracing_on();
kgdb_info[cpu].debuggerinfo = NULL;
kgdb_info[cpu].task = NULL;
kgdb_info[cpu].exception_state &=
~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
kgdb_info[cpu].enter_kgdb--;
smp_mb__before_atomic();
atomic_dec(&slaves_in_kgdb);
dbg_touch_watchdogs();
local_irq_restore(flags);
rcu_read_unlock();
return 0;
}
cpu_relax();
}
/*
* For single stepping, try to only enter on the processor
* that was single stepping. To guard against a deadlock, the
* kernel will only try for the value of sstep_tries before
* giving up and continuing on.
*/
if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
(kgdb_info[cpu].task &&
kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
atomic_set(&kgdb_active, -1);
raw_spin_unlock(&dbg_master_lock);
dbg_touch_watchdogs();
local_irq_restore(flags);
rcu_read_unlock();
goto acquirelock;
}
if (!kgdb_io_ready(1)) {
kgdb_info[cpu].ret_state = 1;
goto kgdb_restore; /* No I/O connection, resume the system */
}
/*
* Don't enter if we have hit a removed breakpoint.
*/
if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
goto kgdb_restore;
atomic_inc(&ignore_console_lock_warning);
/* Call the I/O driver's pre_exception routine */
if (dbg_io_ops->pre_exception)
dbg_io_ops->pre_exception();
/*
* Get the passive CPU lock which will hold all the non-primary
* CPU in a spin state while the debugger is active
*/
if (!kgdb_single_step)
raw_spin_lock(&dbg_slave_lock);
#ifdef CONFIG_SMP
/* If send_ready set, slaves are already waiting */
if (ks->send_ready)
atomic_set(ks->send_ready, 1);
/* Signal the other CPUs to enter kgdb_wait() */
else if ((!kgdb_single_step) && kgdb_do_roundup)
kgdb_roundup_cpus();
#endif
/*
* Wait for the other CPUs to be notified and be waiting for us:
*/
time_left = MSEC_PER_SEC;
while (kgdb_do_roundup && --time_left &&
(atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
online_cpus)
udelay(1000);
if (!time_left)
pr_crit("Timed out waiting for secondary CPUs.\n");
/*
* At this point the primary processor is completely
* in the debugger and all secondary CPUs are quiescent
*/
dbg_deactivate_sw_breakpoints();
kgdb_single_step = 0;
kgdb_contthread = current;
exception_level = 0;
trace_on = tracing_is_on();
if (trace_on)
tracing_off();
while (1) {
cpu_master_loop:
if (dbg_kdb_mode) {
kgdb_connected = 1;
error = kdb_stub(ks);
if (error == -1)
continue;
kgdb_connected = 0;
} else {
/*
* This is a brutal way to interfere with the debugger
* and prevent gdb being used to poke at kernel memory.
* This could cause trouble if lockdown is applied when
* there is already an active gdb session. For now the
* answer is simply "don't do that". Typically lockdown
* *will* be applied before the debug core gets started
* so only developers using kgdb for fairly advanced
* early kernel debug can be biten by this. Hopefully
* they are sophisticated enough to take care of
* themselves, especially with help from the lockdown
* message printed on the console!
*/
if (security_locked_down(LOCKDOWN_DBG_WRITE_KERNEL)) {
if (IS_ENABLED(CONFIG_KGDB_KDB)) {
/* Switch back to kdb if possible... */
dbg_kdb_mode = 1;
continue;
} else {
/* ... otherwise just bail */
break;
}
}
error = gdb_serial_stub(ks);
}
if (error == DBG_PASS_EVENT) {
dbg_kdb_mode = !dbg_kdb_mode;
} else if (error == DBG_SWITCH_CPU_EVENT) {
kgdb_info[dbg_switch_cpu].exception_state |=
DCPU_NEXT_MASTER;
goto cpu_loop;
} else {
kgdb_info[cpu].ret_state = error;
break;
}
}
dbg_activate_sw_breakpoints();
/* Call the I/O driver's post_exception routine */
if (dbg_io_ops->post_exception)
dbg_io_ops->post_exception();
atomic_dec(&ignore_console_lock_warning);
if (!kgdb_single_step) {
raw_spin_unlock(&dbg_slave_lock);
/* Wait till all the CPUs have quit from the debugger. */
while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
cpu_relax();
}
kgdb_restore:
if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
if (kgdb_info[sstep_cpu].task)
kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
else
kgdb_sstep_pid = 0;
}
if (arch_kgdb_ops.correct_hw_break)
arch_kgdb_ops.correct_hw_break();
if (trace_on)
tracing_on();
kgdb_info[cpu].debuggerinfo = NULL;
kgdb_info[cpu].task = NULL;
kgdb_info[cpu].exception_state &=
~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
kgdb_info[cpu].enter_kgdb--;
smp_mb__before_atomic();
atomic_dec(&masters_in_kgdb);
/* Free kgdb_active */
atomic_set(&kgdb_active, -1);
raw_spin_unlock(&dbg_master_lock);
dbg_touch_watchdogs();
local_irq_restore(flags);
rcu_read_unlock();
return kgdb_info[cpu].ret_state;
}
NOKPROBE_SYMBOL(kgdb_cpu_enter);
/*
* kgdb_handle_exception() - main entry point from a kernel exception
*
* Locking hierarchy:
* interface locks, if any (begin_session)
* kgdb lock (kgdb_active)
*/
int
kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
{
struct kgdb_state kgdb_var;
struct kgdb_state *ks = &kgdb_var;
int ret = 0;
if (arch_kgdb_ops.enable_nmi)
arch_kgdb_ops.enable_nmi(0);
/*
* Avoid entering the debugger if we were triggered due to an oops
* but panic_timeout indicates the system should automatically
* reboot on panic. We don't want to get stuck waiting for input
* on such systems, especially if its "just" an oops.
*/
if (signo != SIGTRAP && panic_timeout)
return 1;
memset(ks, 0, sizeof(struct kgdb_state));
ks->cpu = raw_smp_processor_id();
ks->ex_vector = evector;
ks->signo = signo;
ks->err_code = ecode;
ks->linux_regs = regs;
if (kgdb_reenter_check(ks))
goto out; /* Ouch, double exception ! */
if (kgdb_info[ks->cpu].enter_kgdb != 0)
goto out;
ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
out:
if (arch_kgdb_ops.enable_nmi)
arch_kgdb_ops.enable_nmi(1);
return ret;
}
NOKPROBE_SYMBOL(kgdb_handle_exception);
/*
* GDB places a breakpoint at this function to know dynamically loaded objects.
*/
static int module_event(struct notifier_block *self, unsigned long val,
void *data)
{
return 0;
}
static struct notifier_block dbg_module_load_nb = {
.notifier_call = module_event,
};
int kgdb_nmicallback(int cpu, void *regs)
{
#ifdef CONFIG_SMP
struct kgdb_state kgdb_var;
struct kgdb_state *ks = &kgdb_var;
kgdb_info[cpu].rounding_up = false;
memset(ks, 0, sizeof(struct kgdb_state));
ks->cpu = cpu;
ks->linux_regs = regs;
if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
raw_spin_is_locked(&dbg_master_lock)) {
kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
return 0;
}
#endif
return 1;
}
NOKPROBE_SYMBOL(kgdb_nmicallback);
int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
atomic_t *send_ready)
{
#ifdef CONFIG_SMP
if (!kgdb_io_ready(0) || !send_ready)
return 1;
if (kgdb_info[cpu].enter_kgdb == 0) {
struct kgdb_state kgdb_var;
struct kgdb_state *ks = &kgdb_var;
memset(ks, 0, sizeof(struct kgdb_state));
ks->cpu = cpu;
ks->ex_vector = trapnr;
ks->signo = SIGTRAP;
ks->err_code = err_code;
ks->linux_regs = regs;
ks->send_ready = send_ready;
kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
return 0;
}
#endif
return 1;
}
NOKPROBE_SYMBOL(kgdb_nmicallin);
static void kgdb_console_write(struct console *co, const char *s,
unsigned count)
{
unsigned long flags;
/* If we're debugging, or KGDB has not connected, don't try
* and print. */
if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
return;
local_irq_save(flags);
gdbstub_msg_write(s, count);
local_irq_restore(flags);
}
static struct console kgdbcons = {
.name = "kgdb",
.write = kgdb_console_write,
.flags = CON_PRINTBUFFER | CON_ENABLED,
.index = -1,
};
static int __init opt_kgdb_con(char *str)
{
kgdb_use_con = 1;
if (kgdb_io_module_registered && !kgdb_con_registered) {
register_console(&kgdbcons);
kgdb_con_registered = 1;
}
return 0;
}
early_param("kgdbcon", opt_kgdb_con);
#ifdef CONFIG_MAGIC_SYSRQ
static void sysrq_handle_dbg(int key)
{
if (!dbg_io_ops) {
pr_crit("ERROR: No KGDB I/O module available\n");
return;
}
if (!kgdb_connected) {
#ifdef CONFIG_KGDB_KDB
if (!dbg_kdb_mode)
pr_crit("KGDB or $3#33 for KDB\n");
#else
pr_crit("Entering KGDB\n");
#endif
}
kgdb_breakpoint();
}
static const struct sysrq_key_op sysrq_dbg_op = {
.handler = sysrq_handle_dbg,
.help_msg = "debug(g)",
.action_msg = "DEBUG",
};
#endif
void kgdb_panic(const char *msg)
{
if (!kgdb_io_module_registered)
return;