projects/linux·blob 6fbac201 · refs

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1/*
2 * Kernel Debug Core
3 *
4 * Maintainer: Jason Wessel <[email protected]>
5 *
6 * Copyright (C) 2000-2001 VERITAS Software Corporation.
7 * Copyright (C) 2002-2004 Timesys Corporation
8 * Copyright (C) 2003-2004 Amit S. Kale <[email protected]>
9 * Copyright (C) 2004 Pavel Machek <[email protected]>
10 * Copyright (C) 2004-2006 Tom Rini <[email protected]>
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 <[email protected]>
15 *
16 * Contributors at various stages not listed above:
17 * Jason Wessel ( [email protected] )
18 * George Anzinger <[email protected]>
19 * Anurekh Saxena ([email protected])
20 * Lake Stevens Instrument Division (Glenn Engel)
21 * Jim Kingdon, Cygnus Support.
22 *
23 * Original KGDB stub: David Grothe <[email protected]>,
24 * Tigran Aivazian <[email protected]>
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
59#include <asm/cacheflush.h>
60#include <asm/byteorder.h>
61#include <linux/atomic.h>
62
63#include "debug_core.h"
64
65static int kgdb_break_asap;
66
67struct debuggerinfo_struct kgdb_info[NR_CPUS];
68
69/**
70 * kgdb_connected - Is a host GDB connected to us?
71 */
72int kgdb_connected;
73EXPORT_SYMBOL_GPL(kgdb_connected);
74
75/* All the KGDB handlers are installed */
76int kgdb_io_module_registered;
77
78/* Guard for recursive entry */
79static int exception_level;
80
81struct kgdb_io *dbg_io_ops;
82static DEFINE_SPINLOCK(kgdb_registration_lock);
83
84/* Action for the reboot notifiter, a global allow kdb to change it */
85static int kgdbreboot;
86/* kgdb console driver is loaded */
87static int kgdb_con_registered;
88/* determine if kgdb console output should be used */
89static int kgdb_use_con;
90/* Flag for alternate operations for early debugging */
91bool dbg_is_early = true;
92/* Next cpu to become the master debug core */
93int dbg_switch_cpu;
94
95/* Use kdb or gdbserver mode */
96int dbg_kdb_mode = 1;
97
98static int __init opt_kgdb_con(char *str)
99{
100 kgdb_use_con = 1;
101 return 0;
102}
103
104early_param("kgdbcon", opt_kgdb_con);
105
106module_param(kgdb_use_con, int, 0644);
107module_param(kgdbreboot, int, 0644);
108
109/*
110 * Holds information about breakpoints in a kernel. These breakpoints are
111 * added and removed by gdb.
112 */
113static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
114 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
115};
116
117/*
118 * The CPU# of the active CPU, or -1 if none:
119 */
120atomic_t kgdb_active = ATOMIC_INIT(-1);
121EXPORT_SYMBOL_GPL(kgdb_active);
122static DEFINE_RAW_SPINLOCK(dbg_master_lock);
123static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
124
125/*
126 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
127 * bootup code (which might not have percpu set up yet):
128 */
129static atomic_t masters_in_kgdb;
130static atomic_t slaves_in_kgdb;
131static atomic_t kgdb_break_tasklet_var;
132atomic_t kgdb_setting_breakpoint;
133
134struct task_struct *kgdb_usethread;
135struct task_struct *kgdb_contthread;
136
137int kgdb_single_step;
138static pid_t kgdb_sstep_pid;
139
140/* to keep track of the CPU which is doing the single stepping*/
141atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
142
143/*
144 * If you are debugging a problem where roundup (the collection of
145 * all other CPUs) is a problem [this should be extremely rare],
146 * then use the nokgdbroundup option to avoid roundup. In that case
147 * the other CPUs might interfere with your debugging context, so
148 * use this with care:
149 */
150static int kgdb_do_roundup = 1;
151
152static int __init opt_nokgdbroundup(char *str)
153{
154 kgdb_do_roundup = 0;
155
156 return 0;
157}
158
159early_param("nokgdbroundup", opt_nokgdbroundup);
160
161/*
162 * Finally, some KGDB code :-)
163 */
164
165/*
166 * Weak aliases for breakpoint management,
167 * can be overriden by architectures when needed:
168 */
169int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
170{
171 int err;
172
173 err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
174 BREAK_INSTR_SIZE);
175 if (err)
176 return err;
177 err = probe_kernel_write((char *)bpt->bpt_addr,
178 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
179 return err;
180}
181
182int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
183{
184 return probe_kernel_write((char *)bpt->bpt_addr,
185 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
186}
187
188int __weak kgdb_validate_break_address(unsigned long addr)
189{
190 struct kgdb_bkpt tmp;
191 int err;
192 /* Validate setting the breakpoint and then removing it. If the
193 * remove fails, the kernel needs to emit a bad message because we
194 * are deep trouble not being able to put things back the way we
195 * found them.
196 */
197 tmp.bpt_addr = addr;
198 err = kgdb_arch_set_breakpoint(&tmp);
199 if (err)
200 return err;
201 err = kgdb_arch_remove_breakpoint(&tmp);
202 if (err)
203 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
204 addr);
205 return err;
206}
207
208unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
209{
210 return instruction_pointer(regs);
211}
212
213int __weak kgdb_arch_init(void)
214{
215 return 0;
216}
217
218int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
219{
220 return 0;
221}
222
223/*
224 * Some architectures need cache flushes when we set/clear a
225 * breakpoint:
226 */
227static void kgdb_flush_swbreak_addr(unsigned long addr)
228{
229 if (!CACHE_FLUSH_IS_SAFE)
230 return;
231
232 if (current->mm) {
233 int i;
234
235 for (i = 0; i < VMACACHE_SIZE; i++) {
236 if (!current->vmacache.vmas[i])
237 continue;
238 flush_cache_range(current->vmacache.vmas[i],
239 addr, addr + BREAK_INSTR_SIZE);
240 }
241 }
242
243 /* Force flush instruction cache if it was outside the mm */
244 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
245}
246
247/*
248 * SW breakpoint management:
249 */
250int dbg_activate_sw_breakpoints(void)
251{
252 int error;
253 int ret = 0;
254 int i;
255
256 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
257 if (kgdb_break[i].state != BP_SET)
258 continue;
259
260 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
261 if (error) {
262 ret = error;
263 pr_info("BP install failed: %lx\n",
264 kgdb_break[i].bpt_addr);
265 continue;
266 }
267
268 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
269 kgdb_break[i].state = BP_ACTIVE;
270 }
271 return ret;
272}
273
274int dbg_set_sw_break(unsigned long addr)
275{
276 int err = kgdb_validate_break_address(addr);
277 int breakno = -1;
278 int i;
279
280 if (err)
281 return err;
282
283 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
284 if ((kgdb_break[i].state == BP_SET) &&
285 (kgdb_break[i].bpt_addr == addr))
286 return -EEXIST;
287 }
288 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
289 if (kgdb_break[i].state == BP_REMOVED &&
290 kgdb_break[i].bpt_addr == addr) {
291 breakno = i;
292 break;
293 }
294 }
295
296 if (breakno == -1) {
297 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
298 if (kgdb_break[i].state == BP_UNDEFINED) {
299 breakno = i;
300 break;
301 }
302 }
303 }
304
305 if (breakno == -1)
306 return -E2BIG;
307
308 kgdb_break[breakno].state = BP_SET;
309 kgdb_break[breakno].type = BP_BREAKPOINT;
310 kgdb_break[breakno].bpt_addr = addr;
311
312 return 0;
313}
314
315int dbg_deactivate_sw_breakpoints(void)
316{
317 int error;
318 int ret = 0;
319 int i;
320
321 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
322 if (kgdb_break[i].state != BP_ACTIVE)
323 continue;
324 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
325 if (error) {
326 pr_info("BP remove failed: %lx\n",
327 kgdb_break[i].bpt_addr);
328 ret = error;
329 }
330
331 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
332 kgdb_break[i].state = BP_SET;
333 }
334 return ret;
335}
336
337int dbg_remove_sw_break(unsigned long addr)
338{
339 int i;
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 kgdb_break[i].state = BP_REMOVED;
345 return 0;
346 }
347 }
348 return -ENOENT;
349}
350
351int kgdb_isremovedbreak(unsigned long addr)
352{
353 int i;
354
355 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
356 if ((kgdb_break[i].state == BP_REMOVED) &&
357 (kgdb_break[i].bpt_addr == addr))
358 return 1;
359 }
360 return 0;
361}
362
363int dbg_remove_all_break(void)
364{
365 int error;
366 int i;
367
368 /* Clear memory breakpoints. */
369 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
370 if (kgdb_break[i].state != BP_ACTIVE)
371 goto setundefined;
372 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
373 if (error)
374 pr_err("breakpoint remove failed: %lx\n",
375 kgdb_break[i].bpt_addr);
376setundefined:
377 kgdb_break[i].state = BP_UNDEFINED;
378 }
379
380 /* Clear hardware breakpoints. */
381 if (arch_kgdb_ops.remove_all_hw_break)
382 arch_kgdb_ops.remove_all_hw_break();
383
384 return 0;
385}
386
387/*
388 * Return true if there is a valid kgdb I/O module. Also if no
389 * debugger is attached a message can be printed to the console about
390 * waiting for the debugger to attach.
391 *
392 * The print_wait argument is only to be true when called from inside
393 * the core kgdb_handle_exception, because it will wait for the
394 * debugger to attach.
395 */
396static int kgdb_io_ready(int print_wait)
397{
398 if (!dbg_io_ops)
399 return 0;
400 if (kgdb_connected)
401 return 1;
402 if (atomic_read(&kgdb_setting_breakpoint))
403 return 1;
404 if (print_wait) {
405#ifdef CONFIG_KGDB_KDB
406 if (!dbg_kdb_mode)
407 pr_crit("waiting... or $3#33 for KDB\n");
408#else
409 pr_crit("Waiting for remote debugger\n");
410#endif
411 }
412 return 1;
413}
414
415static int kgdb_reenter_check(struct kgdb_state *ks)
416{
417 unsigned long addr;
418
419 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
420 return 0;
421
422 /* Panic on recursive debugger calls: */
423 exception_level++;
424 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
425 dbg_deactivate_sw_breakpoints();
426
427 /*
428 * If the break point removed ok at the place exception
429 * occurred, try to recover and print a warning to the end
430 * user because the user planted a breakpoint in a place that
431 * KGDB needs in order to function.
432 */
433 if (dbg_remove_sw_break(addr) == 0) {
434 exception_level = 0;
435 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
436 dbg_activate_sw_breakpoints();
437 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
438 WARN_ON_ONCE(1);
439
440 return 1;
441 }
442 dbg_remove_all_break();
443 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
444
445 if (exception_level > 1) {
446 dump_stack();
447 panic("Recursive entry to debugger");
448 }
449
450 pr_crit("re-enter exception: ALL breakpoints killed\n");
451#ifdef CONFIG_KGDB_KDB
452 /* Allow kdb to debug itself one level */
453 return 0;
454#endif
455 dump_stack();
456 panic("Recursive entry to debugger");
457
458 return 1;
459}
460
461static void dbg_touch_watchdogs(void)
462{
463 touch_softlockup_watchdog_sync();
464 clocksource_touch_watchdog();
465 rcu_cpu_stall_reset();
466}
467
468static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
469 int exception_state)
470{
471 unsigned long flags;
472 int sstep_tries = 100;
473 int error;
474 int cpu;
475 int trace_on = 0;
476 int online_cpus = num_online_cpus();
477 u64 time_left;
478
479 kgdb_info[ks->cpu].enter_kgdb++;
480 kgdb_info[ks->cpu].exception_state |= exception_state;
481
482 if (exception_state == DCPU_WANT_MASTER)
483 atomic_inc(&masters_in_kgdb);
484 else
485 atomic_inc(&slaves_in_kgdb);
486
487 if (arch_kgdb_ops.disable_hw_break)
488 arch_kgdb_ops.disable_hw_break(regs);
489
490acquirelock:
491 /*
492 * Interrupts will be restored by the 'trap return' code, except when
493 * single stepping.
494 */
495 local_irq_save(flags);
496
497 cpu = ks->cpu;
498 kgdb_info[cpu].debuggerinfo = regs;
499 kgdb_info[cpu].task = current;
500 kgdb_info[cpu].ret_state = 0;
501 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
502
503 /* Make sure the above info reaches the primary CPU */
504 smp_mb();
505
506 if (exception_level == 1) {
507 if (raw_spin_trylock(&dbg_master_lock))
508 atomic_xchg(&kgdb_active, cpu);
509 goto cpu_master_loop;
510 }
511
512 /*
513 * CPU will loop if it is a slave or request to become a kgdb
514 * master cpu and acquire the kgdb_active lock:
515 */
516 while (1) {
517cpu_loop:
518 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
519 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
520 goto cpu_master_loop;
521 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
522 if (raw_spin_trylock(&dbg_master_lock)) {
523 atomic_xchg(&kgdb_active, cpu);
524 break;
525 }
526 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
527 if (!raw_spin_is_locked(&dbg_slave_lock))
528 goto return_normal;
529 } else {
530return_normal:
531 /* Return to normal operation by executing any
532 * hw breakpoint fixup.
533 */
534 if (arch_kgdb_ops.correct_hw_break)
535 arch_kgdb_ops.correct_hw_break();
536 if (trace_on)
537 tracing_on();
538 kgdb_info[cpu].exception_state &=
539 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
540 kgdb_info[cpu].enter_kgdb--;
541 smp_mb__before_atomic();
542 atomic_dec(&slaves_in_kgdb);
543 dbg_touch_watchdogs();
544 local_irq_restore(flags);
545 return 0;
546 }
547 cpu_relax();
548 }
549
550 /*
551 * For single stepping, try to only enter on the processor
552 * that was single stepping. To guard against a deadlock, the
553 * kernel will only try for the value of sstep_tries before
554 * giving up and continuing on.
555 */
556 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
557 (kgdb_info[cpu].task &&
558 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
559 atomic_set(&kgdb_active, -1);
560 raw_spin_unlock(&dbg_master_lock);
561 dbg_touch_watchdogs();
562 local_irq_restore(flags);
563
564 goto acquirelock;
565 }
566
567 if (!kgdb_io_ready(1)) {
568 kgdb_info[cpu].ret_state = 1;
569 goto kgdb_restore; /* No I/O connection, resume the system */
570 }
571
572 /*
573 * Don't enter if we have hit a removed breakpoint.
574 */
575 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
576 goto kgdb_restore;
577
578 /* Call the I/O driver's pre_exception routine */
579 if (dbg_io_ops->pre_exception)
580 dbg_io_ops->pre_exception();
581
582 /*
583 * Get the passive CPU lock which will hold all the non-primary
584 * CPU in a spin state while the debugger is active
585 */
586 if (!kgdb_single_step)
587 raw_spin_lock(&dbg_slave_lock);
588
589#ifdef CONFIG_SMP
590 /* If send_ready set, slaves are already waiting */
591 if (ks->send_ready)
592 atomic_set(ks->send_ready, 1);
593
594 /* Signal the other CPUs to enter kgdb_wait() */
595 else if ((!kgdb_single_step) && kgdb_do_roundup)
596 kgdb_roundup_cpus(flags);
597#endif
598
599 /*
600 * Wait for the other CPUs to be notified and be waiting for us:
601 */
602 time_left = MSEC_PER_SEC;
603 while (kgdb_do_roundup && --time_left &&
604 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
605 online_cpus)
606 udelay(1000);
607 if (!time_left)
608 pr_crit("Timed out waiting for secondary CPUs.\n");
609
610 /*
611 * At this point the primary processor is completely
612 * in the debugger and all secondary CPUs are quiescent
613 */
614 dbg_deactivate_sw_breakpoints();
615 kgdb_single_step = 0;
616 kgdb_contthread = current;
617 exception_level = 0;
618 trace_on = tracing_is_on();
619 if (trace_on)
620 tracing_off();
621
622 while (1) {
623cpu_master_loop:
624 if (dbg_kdb_mode) {
625 kgdb_connected = 1;
626 error = kdb_stub(ks);
627 if (error == -1)
628 continue;
629 kgdb_connected = 0;
630 } else {
631 error = gdb_serial_stub(ks);
632 }
633
634 if (error == DBG_PASS_EVENT) {
635 dbg_kdb_mode = !dbg_kdb_mode;
636 } else if (error == DBG_SWITCH_CPU_EVENT) {
637 kgdb_info[dbg_switch_cpu].exception_state |=
638 DCPU_NEXT_MASTER;
639 goto cpu_loop;
640 } else {
641 kgdb_info[cpu].ret_state = error;
642 break;
643 }
644 }
645
646 /* Call the I/O driver's post_exception routine */
647 if (dbg_io_ops->post_exception)
648 dbg_io_ops->post_exception();
649
650 if (!kgdb_single_step) {
651 raw_spin_unlock(&dbg_slave_lock);
652 /* Wait till all the CPUs have quit from the debugger. */
653 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
654 cpu_relax();
655 }
656
657kgdb_restore:
658 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
659 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
660 if (kgdb_info[sstep_cpu].task)
661 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
662 else
663 kgdb_sstep_pid = 0;
664 }
665 if (arch_kgdb_ops.correct_hw_break)
666 arch_kgdb_ops.correct_hw_break();
667 if (trace_on)
668 tracing_on();
669
670 kgdb_info[cpu].exception_state &=
671 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
672 kgdb_info[cpu].enter_kgdb--;
673 smp_mb__before_atomic();
674 atomic_dec(&masters_in_kgdb);
675 /* Free kgdb_active */
676 atomic_set(&kgdb_active, -1);
677 raw_spin_unlock(&dbg_master_lock);
678 dbg_touch_watchdogs();
679 local_irq_restore(flags);
680
681 return kgdb_info[cpu].ret_state;
682}
683
684/*
685 * kgdb_handle_exception() - main entry point from a kernel exception
686 *
687 * Locking hierarchy:
688 * interface locks, if any (begin_session)
689 * kgdb lock (kgdb_active)
690 */
691int
692kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
693{
694 struct kgdb_state kgdb_var;
695 struct kgdb_state *ks = &kgdb_var;
696 int ret = 0;
697
698 if (arch_kgdb_ops.enable_nmi)
699 arch_kgdb_ops.enable_nmi(0);
700 /*
701 * Avoid entering the debugger if we were triggered due to an oops
702 * but panic_timeout indicates the system should automatically
703 * reboot on panic. We don't want to get stuck waiting for input
704 * on such systems, especially if its "just" an oops.
705 */
706 if (signo != SIGTRAP && panic_timeout)
707 return 1;
708
709 memset(ks, 0, sizeof(struct kgdb_state));
710 ks->cpu = raw_smp_processor_id();
711 ks->ex_vector = evector;
712 ks->signo = signo;
713 ks->err_code = ecode;
714 ks->linux_regs = regs;
715
716 if (kgdb_reenter_check(ks))
717 goto out; /* Ouch, double exception ! */
718 if (kgdb_info[ks->cpu].enter_kgdb != 0)
719 goto out;
720
721 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
722out:
723 if (arch_kgdb_ops.enable_nmi)
724 arch_kgdb_ops.enable_nmi(1);
725 return ret;
726}
727
728/*
729 * GDB places a breakpoint at this function to know dynamically
730 * loaded objects. It's not defined static so that only one instance with this
731 * name exists in the kernel.
732 */
733
734static int module_event(struct notifier_block *self, unsigned long val,
735 void *data)
736{
737 return 0;
738}
739
740static struct notifier_block dbg_module_load_nb = {
741 .notifier_call = module_event,
742};
743
744int kgdb_nmicallback(int cpu, void *regs)
745{
746#ifdef CONFIG_SMP
747 struct kgdb_state kgdb_var;
748 struct kgdb_state *ks = &kgdb_var;
749
750 memset(ks, 0, sizeof(struct kgdb_state));
751 ks->cpu = cpu;
752 ks->linux_regs = regs;
753
754 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
755 raw_spin_is_locked(&dbg_master_lock)) {
756 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
757 return 0;
758 }
759#endif
760 return 1;
761}
762
763int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
764 atomic_t *send_ready)
765{
766#ifdef CONFIG_SMP
767 if (!kgdb_io_ready(0) || !send_ready)
768 return 1;
769
770 if (kgdb_info[cpu].enter_kgdb == 0) {
771 struct kgdb_state kgdb_var;
772 struct kgdb_state *ks = &kgdb_var;
773
774 memset(ks, 0, sizeof(struct kgdb_state));
775 ks->cpu = cpu;
776 ks->ex_vector = trapnr;
777 ks->signo = SIGTRAP;
778 ks->err_code = err_code;
779 ks->linux_regs = regs;
780 ks->send_ready = send_ready;
781 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
782 return 0;
783 }
784#endif
785 return 1;
786}
787
788static void kgdb_console_write(struct console *co, const char *s,
789 unsigned count)
790{
791 unsigned long flags;
792
793 /* If we're debugging, or KGDB has not connected, don't try
794 * and print. */
795 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
796 return;
797
798 local_irq_save(flags);
799 gdbstub_msg_write(s, count);
800 local_irq_restore(flags);
801}
802
803static struct console kgdbcons = {
804 .name = "kgdb",
805 .write = kgdb_console_write,
806 .flags = CON_PRINTBUFFER | CON_ENABLED,
807 .index = -1,
808};
809
810#ifdef CONFIG_MAGIC_SYSRQ
811static void sysrq_handle_dbg(int key)
812{
813 if (!dbg_io_ops) {
814 pr_crit("ERROR: No KGDB I/O module available\n");
815 return;
816 }
817 if (!kgdb_connected) {
818#ifdef CONFIG_KGDB_KDB
819 if (!dbg_kdb_mode)
820 pr_crit("KGDB or $3#33 for KDB\n");
821#else
822 pr_crit("Entering KGDB\n");
823#endif
824 }
825
826 kgdb_breakpoint();
827}
828
829static struct sysrq_key_op sysrq_dbg_op = {
830 .handler = sysrq_handle_dbg,
831 .help_msg = "debug(g)",
832 .action_msg = "DEBUG",
833};
834#endif
835
836static int kgdb_panic_event(struct notifier_block *self,
837 unsigned long val,
838 void *data)
839{
840 /*
841 * Avoid entering the debugger if we were triggered due to a panic
842 * We don't want to get stuck waiting for input from user in such case.
843 * panic_timeout indicates the system should automatically
844 * reboot on panic.
845 */
846 if (panic_timeout)
847 return NOTIFY_DONE;
848
849 if (dbg_kdb_mode)
850 kdb_printf("PANIC: %s\n", (char *)data);
851 kgdb_breakpoint();
852 return NOTIFY_DONE;
853}
854
855static struct notifier_block kgdb_panic_event_nb = {
856 .notifier_call = kgdb_panic_event,
857 .priority = INT_MAX,
858};
859
860void __weak kgdb_arch_late(void)
861{
862}
863
864void __init dbg_late_init(void)
865{
866 dbg_is_early = false;
867 if (kgdb_io_module_registered)
868 kgdb_arch_late();
869 kdb_init(KDB_INIT_FULL);
870}
871
872static int
873dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
874{
875 /*
876 * Take the following action on reboot notify depending on value:
877 * 1 == Enter debugger
878 * 0 == [the default] detatch debug client
879 * -1 == Do nothing... and use this until the board resets
880 */
881 switch (kgdbreboot) {
882 case 1:
883 kgdb_breakpoint();
884 case -1:
885 goto done;
886 }
887 if (!dbg_kdb_mode)
888 gdbstub_exit(code);
889done:
890 return NOTIFY_DONE;
891}
892
893static struct notifier_block dbg_reboot_notifier = {
894 .notifier_call = dbg_notify_reboot,
895 .next = NULL,
896 .priority = INT_MAX,
897};
898
899static void kgdb_register_callbacks(void)
900{
901 if (!kgdb_io_module_registered) {
902 kgdb_io_module_registered = 1;
903 kgdb_arch_init();
904 if (!dbg_is_early)
905 kgdb_arch_late();
906 register_module_notifier(&dbg_module_load_nb);
907 register_reboot_notifier(&dbg_reboot_notifier);
908 atomic_notifier_chain_register(&panic_notifier_list,
909 &kgdb_panic_event_nb);
910#ifdef CONFIG_MAGIC_SYSRQ
911 register_sysrq_key('g', &sysrq_dbg_op);
912#endif
913 if (kgdb_use_con && !kgdb_con_registered) {
914 register_console(&kgdbcons);
915 kgdb_con_registered = 1;
916 }
917 }
918}
919
920static void kgdb_unregister_callbacks(void)
921{
922 /*
923 * When this routine is called KGDB should unregister from the
924 * panic handler and clean up, making sure it is not handling any
925 * break exceptions at the time.
926 */
927 if (kgdb_io_module_registered) {
928 kgdb_io_module_registered = 0;
929 unregister_reboot_notifier(&dbg_reboot_notifier);
930 unregister_module_notifier(&dbg_module_load_nb);
931 atomic_notifier_chain_unregister(&panic_notifier_list,
932 &kgdb_panic_event_nb);
933 kgdb_arch_exit();
934#ifdef CONFIG_MAGIC_SYSRQ
935 unregister_sysrq_key('g', &sysrq_dbg_op);
936#endif
937 if (kgdb_con_registered) {
938 unregister_console(&kgdbcons);
939 kgdb_con_registered = 0;
940 }
941 }
942}
943
944/*
945 * There are times a tasklet needs to be used vs a compiled in
946 * break point so as to cause an exception outside a kgdb I/O module,
947 * such as is the case with kgdboe, where calling a breakpoint in the
948 * I/O driver itself would be fatal.
949 */
950static void kgdb_tasklet_bpt(unsigned long ing)
951{
952 kgdb_breakpoint();
953 atomic_set(&kgdb_break_tasklet_var, 0);
954}
955
956static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
957
958void kgdb_schedule_breakpoint(void)
959{
960 if (atomic_read(&kgdb_break_tasklet_var) ||
961 atomic_read(&kgdb_active) != -1 ||
962 atomic_read(&kgdb_setting_breakpoint))
963 return;
964 atomic_inc(&kgdb_break_tasklet_var);
965 tasklet_schedule(&kgdb_tasklet_breakpoint);
966}
967EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
968
969static void kgdb_initial_breakpoint(void)
970{
971 kgdb_break_asap = 0;
972
973 pr_crit("Waiting for connection from remote gdb...\n");
974 kgdb_breakpoint();
975}
976
977/**
978 * kgdb_register_io_module - register KGDB IO module
979 * @new_dbg_io_ops: the io ops vector
980 *
981 * Register it with the KGDB core.
982 */
983int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
984{
985 int err;
986
987 spin_lock(&kgdb_registration_lock);
988
989 if (dbg_io_ops) {
990 spin_unlock(&kgdb_registration_lock);
991
992 pr_err("Another I/O driver is already registered with KGDB\n");
993 return -EBUSY;
994 }
995
996 if (new_dbg_io_ops->init) {
997 err = new_dbg_io_ops->init();
998 if (err) {
999 spin_unlock(&kgdb_registration_lock);
1000 return err;
1001 }
1002 }
1003
1004 dbg_io_ops = new_dbg_io_ops;
1005
1006 spin_unlock(&kgdb_registration_lock);
1007
1008 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1009
1010 /* Arm KGDB now. */
1011 kgdb_register_callbacks();
1012
1013 if (kgdb_break_asap)
1014 kgdb_initial_breakpoint();
1015
1016 return 0;
1017}
1018EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1019
1020/**
1021 * kkgdb_unregister_io_module - unregister KGDB IO module
1022 * @old_dbg_io_ops: the io ops vector
1023 *
1024 * Unregister it with the KGDB core.
1025 */
1026void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1027{
1028 BUG_ON(kgdb_connected);
1029
1030 /*
1031 * KGDB is no longer able to communicate out, so
1032 * unregister our callbacks and reset state.
1033 */
1034 kgdb_unregister_callbacks();
1035
1036 spin_lock(&kgdb_registration_lock);
1037
1038 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1039 dbg_io_ops = NULL;
1040
1041 spin_unlock(&kgdb_registration_lock);
1042
1043 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1044 old_dbg_io_ops->name);
1045}
1046EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1047
1048int dbg_io_get_char(void)
1049{
1050 int ret = dbg_io_ops->read_char();
1051 if (ret == NO_POLL_CHAR)
1052 return -1;
1053 if (!dbg_kdb_mode)
1054 return ret;
1055 if (ret == 127)
1056 return 8;
1057 return ret;
1058}
1059
1060/**
1061 * kgdb_breakpoint - generate breakpoint exception
1062 *
1063 * This function will generate a breakpoint exception. It is used at the
1064 * beginning of a program to sync up with a debugger and can be used
1065 * otherwise as a quick means to stop program execution and "break" into
1066 * the debugger.
1067 */
1068noinline void kgdb_breakpoint(void)
1069{
1070 atomic_inc(&kgdb_setting_breakpoint);
1071 wmb(); /* Sync point before breakpoint */
1072 arch_kgdb_breakpoint();
1073 wmb(); /* Sync point after breakpoint */
1074 atomic_dec(&kgdb_setting_breakpoint);
1075}
1076EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1077
1078static int __init opt_kgdb_wait(char *str)
1079{
1080 kgdb_break_asap = 1;
1081
1082 kdb_init(KDB_INIT_EARLY);
1083 if (kgdb_io_module_registered)
1084 kgdb_initial_breakpoint();
1085
1086 return 0;
1087}
1088
1089early_param("kgdbwait", opt_kgdb_wait);