projects/linux·blob master · refs

1231 lines · 29.0 KiB

1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Kernel Debug Core
4 *
5 * Maintainer: Jason Wessel <[email protected]>
6 *
7 * Copyright (C) 2000-2001 VERITAS Software Corporation.
8 * Copyright (C) 2002-2004 Timesys Corporation
9 * Copyright (C) 2003-2004 Amit S. Kale <[email protected]>
10 * Copyright (C) 2004 Pavel Machek <[email protected]>
11 * Copyright (C) 2004-2006 Tom Rini <[email protected]>
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 <[email protected]>
16 *
17 * Contributors at various stages not listed above:
18 * Jason Wessel ( [email protected] )
19 * George Anzinger <[email protected]>
20 * Anurekh Saxena ([email protected])
21 * Lake Stevens Instrument Division (Glenn Engel)
22 * Jim Kingdon, Cygnus Support.
23 *
24 * Original KGDB stub: David Grothe <[email protected]>,
25 * Tigran Aivazian <[email protected]>
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 the debug trap handler */
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 /*
841 * Avoid entering the debugger if we were triggered due to an oops
842 * but panic_timeout indicates the system should automatically
843 * reboot on panic. We don't want to get stuck waiting for input
844 * on such systems, especially if its "just" an oops.
845 */
846 if (signo != SIGTRAP && panic_timeout)
847 return 1;
848
849 memset(ks, 0, sizeof(struct kgdb_state));
850 ks->cpu = raw_smp_processor_id();
851 ks->ex_vector = evector;
852 ks->signo = signo;
853 ks->err_code = ecode;
854 ks->linux_regs = regs;
855
856 if (kgdb_reenter_check(ks))
857 return 0; /* Ouch, double exception ! */
858 if (kgdb_info[ks->cpu].enter_kgdb != 0)
859 return 0;
860
861 return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
862}
863NOKPROBE_SYMBOL(kgdb_handle_exception);
864
865/*
866 * GDB places a breakpoint at this function to know dynamically loaded objects.
867 */
868static int module_event(struct notifier_block *self, unsigned long val,
869 void *data)
870{
871 return 0;
872}
873
874static struct notifier_block dbg_module_load_nb = {
875 .notifier_call = module_event,
876};
877
878int kgdb_nmicallback(int cpu, void *regs)
879{
880#ifdef CONFIG_SMP
881 struct kgdb_state kgdb_var;
882 struct kgdb_state *ks = &kgdb_var;
883
884 kgdb_info[cpu].rounding_up = false;
885
886 memset(ks, 0, sizeof(struct kgdb_state));
887 ks->cpu = cpu;
888 ks->linux_regs = regs;
889
890 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
891 raw_spin_is_locked(&dbg_master_lock)) {
892 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
893 return 0;
894 }
895#endif
896 return 1;
897}
898NOKPROBE_SYMBOL(kgdb_nmicallback);
899
900int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
901 atomic_t *send_ready)
902{
903#ifdef CONFIG_SMP
904 if (!kgdb_io_ready(0) || !send_ready)
905 return 1;
906
907 if (kgdb_info[cpu].enter_kgdb == 0) {
908 struct kgdb_state kgdb_var;
909 struct kgdb_state *ks = &kgdb_var;
910
911 memset(ks, 0, sizeof(struct kgdb_state));
912 ks->cpu = cpu;
913 ks->ex_vector = trapnr;
914 ks->signo = SIGTRAP;
915 ks->err_code = err_code;
916 ks->linux_regs = regs;
917 ks->send_ready = send_ready;
918 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
919 return 0;
920 }
921#endif
922 return 1;
923}
924NOKPROBE_SYMBOL(kgdb_nmicallin);
925
926static void kgdb_console_write(struct console *co, const char *s,
927 unsigned count)
928{
929 unsigned long flags;
930
931 /* If we're debugging, or KGDB has not connected, don't try
932 * and print. */
933 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
934 return;
935
936 local_irq_save(flags);
937 gdbstub_msg_write(s, count);
938 local_irq_restore(flags);
939}
940
941static struct console kgdbcons = {
942 .name = "kgdb",
943 .write = kgdb_console_write,
944 .flags = CON_PRINTBUFFER | CON_ENABLED,
945 .index = -1,
946};
947
948static int __init opt_kgdb_con(char *str)
949{
950 kgdb_use_con = 1;
951
952 if (kgdb_io_module_registered && !kgdb_con_registered) {
953 register_console(&kgdbcons);
954 kgdb_con_registered = 1;
955 }
956
957 return 0;
958}
959
960early_param("kgdbcon", opt_kgdb_con);
961
962#ifdef CONFIG_MAGIC_SYSRQ
963static void sysrq_handle_dbg(u8 key)
964{
965 if (!dbg_io_ops) {
966 pr_crit("ERROR: No KGDB I/O module available\n");
967 return;
968 }
969 if (!kgdb_connected) {
970#ifdef CONFIG_KGDB_KDB
971 if (!dbg_kdb_mode)
972 pr_crit("KGDB or $3#33 for KDB\n");
973#else
974 pr_crit("Entering KGDB\n");
975#endif
976 }
977
978 kgdb_breakpoint();
979}
980
981static const struct sysrq_key_op sysrq_dbg_op = {
982 .handler = sysrq_handle_dbg,
983 .help_msg = "debug(g)",
984 .action_msg = "DEBUG",
985};
986#endif
987
988void kgdb_panic(const char *msg)
989{
990 if (!kgdb_io_module_registered)
991 return;
992
993 /*
994 * We don't want to get stuck waiting for input from user if
995 * "panic_timeout" indicates the system should automatically
996 * reboot on panic.
997 */
998 if (panic_timeout)
999 return;
1000
1001 debug_locks_off();
1002 console_flush_on_panic(CONSOLE_FLUSH_PENDING);
1003
1004 if (dbg_kdb_mode)
1005 kdb_printf("PANIC: %s\n", msg);
1006
1007 kgdb_breakpoint();
1008}
1009
1010static void kgdb_initial_breakpoint(void)
1011{
1012 kgdb_break_asap = 0;
1013
1014 pr_crit("Waiting for connection from remote gdb...\n");
1015 kgdb_breakpoint();
1016}
1017
1018void __weak kgdb_arch_late(void)
1019{
1020}
1021
1022void __init dbg_late_init(void)
1023{
1024 dbg_is_early = false;
1025 if (kgdb_io_module_registered)
1026 kgdb_arch_late();
1027 kdb_init(KDB_INIT_FULL);
1028
1029 if (kgdb_io_module_registered && kgdb_break_asap)
1030 kgdb_initial_breakpoint();
1031}
1032
1033static int
1034dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
1035{
1036 /*
1037 * Take the following action on reboot notify depending on value:
1038 * 1 == Enter debugger
1039 * 0 == [the default] detach debug client
1040 * -1 == Do nothing... and use this until the board resets
1041 */
1042 switch (kgdbreboot) {
1043 case 1:
1044 kgdb_breakpoint();
1045 goto done;
1046 case -1:
1047 goto done;
1048 }
1049 if (!dbg_kdb_mode)
1050 gdbstub_exit(code);
1051done:
1052 return NOTIFY_DONE;
1053}
1054
1055static struct notifier_block dbg_reboot_notifier = {
1056 .notifier_call = dbg_notify_reboot,
1057 .next = NULL,
1058 .priority = INT_MAX,
1059};
1060
1061static void kgdb_register_callbacks(void)
1062{
1063 if (!kgdb_io_module_registered) {
1064 kgdb_io_module_registered = 1;
1065 kgdb_arch_init();
1066 if (!dbg_is_early)
1067 kgdb_arch_late();
1068 register_module_notifier(&dbg_module_load_nb);
1069 register_reboot_notifier(&dbg_reboot_notifier);
1070#ifdef CONFIG_MAGIC_SYSRQ
1071 register_sysrq_key('g', &sysrq_dbg_op);
1072#endif
1073 if (kgdb_use_con && !kgdb_con_registered) {
1074 register_console(&kgdbcons);
1075 kgdb_con_registered = 1;
1076 }
1077 }
1078}
1079
1080static void kgdb_unregister_callbacks(void)
1081{
1082 /*
1083 * When this routine is called KGDB should unregister from
1084 * handlers and clean up, making sure it is not handling any
1085 * break exceptions at the time.
1086 */
1087 if (kgdb_io_module_registered) {
1088 kgdb_io_module_registered = 0;
1089 unregister_reboot_notifier(&dbg_reboot_notifier);
1090 unregister_module_notifier(&dbg_module_load_nb);
1091 kgdb_arch_exit();
1092#ifdef CONFIG_MAGIC_SYSRQ
1093 unregister_sysrq_key('g', &sysrq_dbg_op);
1094#endif
1095 if (kgdb_con_registered) {
1096 unregister_console(&kgdbcons);
1097 kgdb_con_registered = 0;
1098 }
1099 }
1100}
1101
1102/**
1103 * kgdb_register_io_module - register KGDB IO module
1104 * @new_dbg_io_ops: the io ops vector
1105 *
1106 * Register it with the KGDB core.
1107 */
1108int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
1109{
1110 struct kgdb_io *old_dbg_io_ops;
1111 int err;
1112
1113 spin_lock(&kgdb_registration_lock);
1114
1115 old_dbg_io_ops = dbg_io_ops;
1116 if (old_dbg_io_ops) {
1117 if (!old_dbg_io_ops->deinit) {
1118 spin_unlock(&kgdb_registration_lock);
1119
1120 pr_err("KGDB I/O driver %s can't replace %s.\n",
1121 new_dbg_io_ops->name, old_dbg_io_ops->name);
1122 return -EBUSY;
1123 }
1124 pr_info("Replacing I/O driver %s with %s\n",
1125 old_dbg_io_ops->name, new_dbg_io_ops->name);
1126 }
1127
1128 if (new_dbg_io_ops->init) {
1129 err = new_dbg_io_ops->init();
1130 if (err) {
1131 spin_unlock(&kgdb_registration_lock);
1132 return err;
1133 }
1134 }
1135
1136 dbg_io_ops = new_dbg_io_ops;
1137
1138 spin_unlock(&kgdb_registration_lock);
1139
1140 if (old_dbg_io_ops) {
1141 old_dbg_io_ops->deinit();
1142 return 0;
1143 }
1144
1145 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1146
1147 /* Arm KGDB now. */
1148 kgdb_register_callbacks();
1149
1150 if (kgdb_break_asap &&
1151 (!dbg_is_early || IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG)))
1152 kgdb_initial_breakpoint();
1153
1154 return 0;
1155}
1156EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1157
1158/**
1159 * kgdb_unregister_io_module - unregister KGDB IO module
1160 * @old_dbg_io_ops: the io ops vector
1161 *
1162 * Unregister it with the KGDB core.
1163 */
1164void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1165{
1166 BUG_ON(kgdb_connected);
1167
1168 /*
1169 * KGDB is no longer able to communicate out, so
1170 * unregister our callbacks and reset state.
1171 */
1172 kgdb_unregister_callbacks();
1173
1174 spin_lock(&kgdb_registration_lock);
1175
1176 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1177 dbg_io_ops = NULL;
1178
1179 spin_unlock(&kgdb_registration_lock);
1180
1181 if (old_dbg_io_ops->deinit)
1182 old_dbg_io_ops->deinit();
1183
1184 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1185 old_dbg_io_ops->name);
1186}
1187EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1188
1189int dbg_io_get_char(void)
1190{
1191 int ret = dbg_io_ops->read_char();
1192 if (ret == NO_POLL_CHAR)
1193 return -1;
1194 if (!dbg_kdb_mode)
1195 return ret;
1196 if (ret == 127)
1197 return 8;
1198 return ret;
1199}
1200
1201/**
1202 * kgdb_breakpoint - generate breakpoint exception
1203 *
1204 * This function will generate a breakpoint exception. It is used at the
1205 * beginning of a program to sync up with a debugger and can be used
1206 * otherwise as a quick means to stop program execution and "break" into
1207 * the debugger.
1208 */
1209noinline void kgdb_breakpoint(void)
1210{
1211 atomic_inc(&kgdb_setting_breakpoint);
1212 wmb(); /* Sync point before breakpoint */
1213 arch_kgdb_breakpoint();
1214 wmb(); /* Sync point after breakpoint */
1215 atomic_dec(&kgdb_setting_breakpoint);
1216}
1217EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1218
1219static int __init opt_kgdb_wait(char *str)
1220{
1221 kgdb_break_asap = 1;
1222
1223 kdb_init(KDB_INIT_EARLY);
1224 if (kgdb_io_module_registered &&
1225 IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG))
1226 kgdb_initial_breakpoint();
1227
1228 return 0;
1229}
1230
1231early_param("kgdbwait", opt_kgdb_wait);