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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(u8 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 debug_locks_off();
1010 console_flush_on_panic(CONSOLE_FLUSH_PENDING);
1011
1012 if (dbg_kdb_mode)
1013 kdb_printf("PANIC: %s\n", msg);
1014
1015 kgdb_breakpoint();
1016}
1017
1018static void kgdb_initial_breakpoint(void)
1019{
1020 kgdb_break_asap = 0;
1021
1022 pr_crit("Waiting for connection from remote gdb...\n");
1023 kgdb_breakpoint();
1024}
1025
1026void __weak kgdb_arch_late(void)
1027{
1028}
1029
1030void __init dbg_late_init(void)
1031{
1032 dbg_is_early = false;
1033 if (kgdb_io_module_registered)
1034 kgdb_arch_late();
1035 kdb_init(KDB_INIT_FULL);
1036
1037 if (kgdb_io_module_registered && kgdb_break_asap)
1038 kgdb_initial_breakpoint();
1039}
1040
1041static int
1042dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
1043{
1044 /*
1045 * Take the following action on reboot notify depending on value:
1046 * 1 == Enter debugger
1047 * 0 == [the default] detach debug client
1048 * -1 == Do nothing... and use this until the board resets
1049 */
1050 switch (kgdbreboot) {
1051 case 1:
1052 kgdb_breakpoint();
1053 goto done;
1054 case -1:
1055 goto done;
1056 }
1057 if (!dbg_kdb_mode)
1058 gdbstub_exit(code);
1059done:
1060 return NOTIFY_DONE;
1061}
1062
1063static struct notifier_block dbg_reboot_notifier = {
1064 .notifier_call = dbg_notify_reboot,
1065 .next = NULL,
1066 .priority = INT_MAX,
1067};
1068
1069static void kgdb_register_callbacks(void)
1070{
1071 if (!kgdb_io_module_registered) {
1072 kgdb_io_module_registered = 1;
1073 kgdb_arch_init();
1074 if (!dbg_is_early)
1075 kgdb_arch_late();
1076 register_module_notifier(&dbg_module_load_nb);
1077 register_reboot_notifier(&dbg_reboot_notifier);
1078#ifdef CONFIG_MAGIC_SYSRQ
1079 register_sysrq_key('g', &sysrq_dbg_op);
1080#endif
1081 if (kgdb_use_con && !kgdb_con_registered) {
1082 register_console(&kgdbcons);
1083 kgdb_con_registered = 1;
1084 }
1085 }
1086}
1087
1088static void kgdb_unregister_callbacks(void)
1089{
1090 /*
1091 * When this routine is called KGDB should unregister from
1092 * handlers and clean up, making sure it is not handling any
1093 * break exceptions at the time.
1094 */
1095 if (kgdb_io_module_registered) {
1096 kgdb_io_module_registered = 0;
1097 unregister_reboot_notifier(&dbg_reboot_notifier);
1098 unregister_module_notifier(&dbg_module_load_nb);
1099 kgdb_arch_exit();
1100#ifdef CONFIG_MAGIC_SYSRQ
1101 unregister_sysrq_key('g', &sysrq_dbg_op);
1102#endif
1103 if (kgdb_con_registered) {
1104 unregister_console(&kgdbcons);
1105 kgdb_con_registered = 0;
1106 }
1107 }
1108}
1109
1110/**
1111 * kgdb_register_io_module - register KGDB IO module
1112 * @new_dbg_io_ops: the io ops vector
1113 *
1114 * Register it with the KGDB core.
1115 */
1116int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
1117{
1118 struct kgdb_io *old_dbg_io_ops;
1119 int err;
1120
1121 spin_lock(&kgdb_registration_lock);
1122
1123 old_dbg_io_ops = dbg_io_ops;
1124 if (old_dbg_io_ops) {
1125 if (!old_dbg_io_ops->deinit) {
1126 spin_unlock(&kgdb_registration_lock);
1127
1128 pr_err("KGDB I/O driver %s can't replace %s.\n",
1129 new_dbg_io_ops->name, old_dbg_io_ops->name);
1130 return -EBUSY;
1131 }
1132 pr_info("Replacing I/O driver %s with %s\n",
1133 old_dbg_io_ops->name, new_dbg_io_ops->name);
1134 }
1135
1136 if (new_dbg_io_ops->init) {
1137 err = new_dbg_io_ops->init();
1138 if (err) {
1139 spin_unlock(&kgdb_registration_lock);
1140 return err;
1141 }
1142 }
1143
1144 dbg_io_ops = new_dbg_io_ops;
1145
1146 spin_unlock(&kgdb_registration_lock);
1147
1148 if (old_dbg_io_ops) {
1149 old_dbg_io_ops->deinit();
1150 return 0;
1151 }
1152
1153 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1154
1155 /* Arm KGDB now. */
1156 kgdb_register_callbacks();
1157
1158 if (kgdb_break_asap &&
1159 (!dbg_is_early || IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG)))
1160 kgdb_initial_breakpoint();
1161
1162 return 0;
1163}
1164EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1165
1166/**
1167 * kgdb_unregister_io_module - unregister KGDB IO module
1168 * @old_dbg_io_ops: the io ops vector
1169 *
1170 * Unregister it with the KGDB core.
1171 */
1172void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1173{
1174 BUG_ON(kgdb_connected);
1175
1176 /*
1177 * KGDB is no longer able to communicate out, so
1178 * unregister our callbacks and reset state.
1179 */
1180 kgdb_unregister_callbacks();
1181
1182 spin_lock(&kgdb_registration_lock);
1183
1184 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1185 dbg_io_ops = NULL;
1186
1187 spin_unlock(&kgdb_registration_lock);
1188
1189 if (old_dbg_io_ops->deinit)
1190 old_dbg_io_ops->deinit();
1191
1192 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1193 old_dbg_io_ops->name);
1194}
1195EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1196
1197int dbg_io_get_char(void)
1198{
1199 int ret = dbg_io_ops->read_char();
1200 if (ret == NO_POLL_CHAR)
1201 return -1;
1202 if (!dbg_kdb_mode)
1203 return ret;
1204 if (ret == 127)
1205 return 8;
1206 return ret;
1207}
1208
1209/**
1210 * kgdb_breakpoint - generate breakpoint exception
1211 *
1212 * This function will generate a breakpoint exception. It is used at the
1213 * beginning of a program to sync up with a debugger and can be used
1214 * otherwise as a quick means to stop program execution and "break" into
1215 * the debugger.
1216 */
1217noinline void kgdb_breakpoint(void)
1218{
1219 atomic_inc(&kgdb_setting_breakpoint);
1220 wmb(); /* Sync point before breakpoint */
1221 arch_kgdb_breakpoint();
1222 wmb(); /* Sync point after breakpoint */
1223 atomic_dec(&kgdb_setting_breakpoint);
1224}
1225EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1226
1227static int __init opt_kgdb_wait(char *str)
1228{
1229 kgdb_break_asap = 1;
1230
1231 kdb_init(KDB_INIT_EARLY);
1232 if (kgdb_io_module_registered &&
1233 IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG))
1234 kgdb_initial_breakpoint();
1235
1236 return 0;
1237}
1238
1239early_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);