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1/*
2 * Kernel Debug Core
3 *
4 * Maintainer: Jason Wessel <jason.wessel@windriver.com>
5 *
6 * Copyright (C) 2000-2001 VERITAS Software Corporation.
7 * Copyright (C) 2002-2004 Timesys Corporation
8 * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
9 * Copyright (C) 2004 Pavel Machek <pavel@ucw.cz>
10 * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
11 * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
12 * Copyright (C) 2005-2009 Wind River Systems, Inc.
13 * Copyright (C) 2007 MontaVista Software, Inc.
14 * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
15 *
16 * Contributors at various stages not listed above:
17 * Jason Wessel ( jason.wessel@windriver.com )
18 * George Anzinger <george@mvista.com>
19 * Anurekh Saxena (anurekh.saxena@timesys.com)
20 * Lake Stevens Instrument Division (Glenn Engel)
21 * Jim Kingdon, Cygnus Support.
22 *
23 * Original KGDB stub: David Grothe <dave@gcom.com>,
24 * Tigran Aivazian <tigran@sco.com>
25 *
26 * This file is licensed under the terms of the GNU General Public License
27 * version 2. This program is licensed "as is" without any warranty of any
28 * kind, whether express or implied.
29 */
30
31#define pr_fmt(fmt) "KGDB: " fmt
32
33#include <linux/pid_namespace.h>
34#include <linux/clocksource.h>
35#include <linux/serial_core.h>
36#include <linux/interrupt.h>
37#include <linux/spinlock.h>
38#include <linux/console.h>
39#include <linux/threads.h>
40#include <linux/uaccess.h>
41#include <linux/kernel.h>
42#include <linux/module.h>
43#include <linux/ptrace.h>
44#include <linux/string.h>
45#include <linux/delay.h>
46#include <linux/sched.h>
47#include <linux/sysrq.h>
48#include <linux/reboot.h>
49#include <linux/init.h>
50#include <linux/kgdb.h>
51#include <linux/kdb.h>
52#include <linux/pid.h>
53#include <linux/smp.h>
54#include <linux/mm.h>
55#include <linux/vmacache.h>
56#include <linux/rcupdate.h>
57
58#include <asm/cacheflush.h>
59#include <asm/byteorder.h>
60#include <linux/atomic.h>
61
62#include "debug_core.h"
63
64static int kgdb_break_asap;
65
66struct debuggerinfo_struct kgdb_info[NR_CPUS];
67
68/**
69 * kgdb_connected - Is a host GDB connected to us?
70 */
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 notifiter, 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
97static int __init opt_kgdb_con(char *str)
98{
99 kgdb_use_con = 1;
100 return 0;
101}
102
103early_param("kgdbcon", opt_kgdb_con);
104
105module_param(kgdb_use_con, int, 0644);
106module_param(kgdbreboot, int, 0644);
107
108/*
109 * Holds information about breakpoints in a kernel. These breakpoints are
110 * added and removed by gdb.
111 */
112static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
113 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
114};
115
116/*
117 * The CPU# of the active CPU, or -1 if none:
118 */
119atomic_t kgdb_active = ATOMIC_INIT(-1);
120EXPORT_SYMBOL_GPL(kgdb_active);
121static DEFINE_RAW_SPINLOCK(dbg_master_lock);
122static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
123
124/*
125 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
126 * bootup code (which might not have percpu set up yet):
127 */
128static atomic_t masters_in_kgdb;
129static atomic_t slaves_in_kgdb;
130static atomic_t kgdb_break_tasklet_var;
131atomic_t kgdb_setting_breakpoint;
132
133struct task_struct *kgdb_usethread;
134struct task_struct *kgdb_contthread;
135
136int kgdb_single_step;
137static pid_t kgdb_sstep_pid;
138
139/* to keep track of the CPU which is doing the single stepping*/
140atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
141
142/*
143 * If you are debugging a problem where roundup (the collection of
144 * all other CPUs) is a problem [this should be extremely rare],
145 * then use the nokgdbroundup option to avoid roundup. In that case
146 * the other CPUs might interfere with your debugging context, so
147 * use this with care:
148 */
149static int kgdb_do_roundup = 1;
150
151static int __init opt_nokgdbroundup(char *str)
152{
153 kgdb_do_roundup = 0;
154
155 return 0;
156}
157
158early_param("nokgdbroundup", opt_nokgdbroundup);
159
160/*
161 * Finally, some KGDB code :-)
162 */
163
164/*
165 * Weak aliases for breakpoint management,
166 * can be overriden by architectures when needed:
167 */
168int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
169{
170 int err;
171
172 err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
173 BREAK_INSTR_SIZE);
174 if (err)
175 return err;
176 err = probe_kernel_write((char *)bpt->bpt_addr,
177 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
178 return err;
179}
180
181int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
182{
183 return probe_kernel_write((char *)bpt->bpt_addr,
184 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
185}
186
187int __weak kgdb_validate_break_address(unsigned long addr)
188{
189 struct kgdb_bkpt tmp;
190 int err;
191 /* Validate setting the breakpoint and then removing it. If the
192 * remove fails, the kernel needs to emit a bad message because we
193 * are deep trouble not being able to put things back the way we
194 * found them.
195 */
196 tmp.bpt_addr = addr;
197 err = kgdb_arch_set_breakpoint(&tmp);
198 if (err)
199 return err;
200 err = kgdb_arch_remove_breakpoint(&tmp);
201 if (err)
202 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
203 addr);
204 return err;
205}
206
207unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
208{
209 return instruction_pointer(regs);
210}
211
212int __weak kgdb_arch_init(void)
213{
214 return 0;
215}
216
217int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
218{
219 return 0;
220}
221
222/*
223 * Some architectures need cache flushes when we set/clear a
224 * breakpoint:
225 */
226static void kgdb_flush_swbreak_addr(unsigned long addr)
227{
228 if (!CACHE_FLUSH_IS_SAFE)
229 return;
230
231 if (current->mm) {
232 int i;
233
234 for (i = 0; i < VMACACHE_SIZE; i++) {
235 if (!current->vmacache[i])
236 continue;
237 flush_cache_range(current->vmacache[i],
238 addr, addr + BREAK_INSTR_SIZE);
239 }
240 }
241
242 /* Force flush instruction cache if it was outside the mm */
243 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
244}
245
246/*
247 * SW breakpoint management:
248 */
249int dbg_activate_sw_breakpoints(void)
250{
251 int error;
252 int ret = 0;
253 int i;
254
255 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
256 if (kgdb_break[i].state != BP_SET)
257 continue;
258
259 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
260 if (error) {
261 ret = error;
262 pr_info("BP install failed: %lx\n",
263 kgdb_break[i].bpt_addr);
264 continue;
265 }
266
267 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
268 kgdb_break[i].state = BP_ACTIVE;
269 }
270 return ret;
271}
272
273int dbg_set_sw_break(unsigned long addr)
274{
275 int err = kgdb_validate_break_address(addr);
276 int breakno = -1;
277 int i;
278
279 if (err)
280 return err;
281
282 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
283 if ((kgdb_break[i].state == BP_SET) &&
284 (kgdb_break[i].bpt_addr == addr))
285 return -EEXIST;
286 }
287 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
288 if (kgdb_break[i].state == BP_REMOVED &&
289 kgdb_break[i].bpt_addr == addr) {
290 breakno = i;
291 break;
292 }
293 }
294
295 if (breakno == -1) {
296 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
297 if (kgdb_break[i].state == BP_UNDEFINED) {
298 breakno = i;
299 break;
300 }
301 }
302 }
303
304 if (breakno == -1)
305 return -E2BIG;
306
307 kgdb_break[breakno].state = BP_SET;
308 kgdb_break[breakno].type = BP_BREAKPOINT;
309 kgdb_break[breakno].bpt_addr = addr;
310
311 return 0;
312}
313
314int dbg_deactivate_sw_breakpoints(void)
315{
316 int error;
317 int ret = 0;
318 int i;
319
320 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
321 if (kgdb_break[i].state != BP_ACTIVE)
322 continue;
323 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
324 if (error) {
325 pr_info("BP remove failed: %lx\n",
326 kgdb_break[i].bpt_addr);
327 ret = error;
328 }
329
330 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
331 kgdb_break[i].state = BP_SET;
332 }
333 return ret;
334}
335
336int dbg_remove_sw_break(unsigned long addr)
337{
338 int i;
339
340 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
341 if ((kgdb_break[i].state == BP_SET) &&
342 (kgdb_break[i].bpt_addr == addr)) {
343 kgdb_break[i].state = BP_REMOVED;
344 return 0;
345 }
346 }
347 return -ENOENT;
348}
349
350int kgdb_isremovedbreak(unsigned long addr)
351{
352 int i;
353
354 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
355 if ((kgdb_break[i].state == BP_REMOVED) &&
356 (kgdb_break[i].bpt_addr == addr))
357 return 1;
358 }
359 return 0;
360}
361
362int dbg_remove_all_break(void)
363{
364 int error;
365 int i;
366
367 /* Clear memory breakpoints. */
368 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
369 if (kgdb_break[i].state != BP_ACTIVE)
370 goto setundefined;
371 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
372 if (error)
373 pr_err("breakpoint remove failed: %lx\n",
374 kgdb_break[i].bpt_addr);
375setundefined:
376 kgdb_break[i].state = BP_UNDEFINED;
377 }
378
379 /* Clear hardware breakpoints. */
380 if (arch_kgdb_ops.remove_all_hw_break)
381 arch_kgdb_ops.remove_all_hw_break();
382
383 return 0;
384}
385
386/*
387 * Return true if there is a valid kgdb I/O module. Also if no
388 * debugger is attached a message can be printed to the console about
389 * waiting for the debugger to attach.
390 *
391 * The print_wait argument is only to be true when called from inside
392 * the core kgdb_handle_exception, because it will wait for the
393 * debugger to attach.
394 */
395static int kgdb_io_ready(int print_wait)
396{
397 if (!dbg_io_ops)
398 return 0;
399 if (kgdb_connected)
400 return 1;
401 if (atomic_read(&kgdb_setting_breakpoint))
402 return 1;
403 if (print_wait) {
404#ifdef CONFIG_KGDB_KDB
405 if (!dbg_kdb_mode)
406 pr_crit("waiting... or $3#33 for KDB\n");
407#else
408 pr_crit("Waiting for remote debugger\n");
409#endif
410 }
411 return 1;
412}
413
414static int kgdb_reenter_check(struct kgdb_state *ks)
415{
416 unsigned long addr;
417
418 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
419 return 0;
420
421 /* Panic on recursive debugger calls: */
422 exception_level++;
423 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
424 dbg_deactivate_sw_breakpoints();
425
426 /*
427 * If the break point removed ok at the place exception
428 * occurred, try to recover and print a warning to the end
429 * user because the user planted a breakpoint in a place that
430 * KGDB needs in order to function.
431 */
432 if (dbg_remove_sw_break(addr) == 0) {
433 exception_level = 0;
434 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
435 dbg_activate_sw_breakpoints();
436 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
437 WARN_ON_ONCE(1);
438
439 return 1;
440 }
441 dbg_remove_all_break();
442 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
443
444 if (exception_level > 1) {
445 dump_stack();
446 panic("Recursive entry to debugger");
447 }
448
449 pr_crit("re-enter exception: ALL breakpoints killed\n");
450#ifdef CONFIG_KGDB_KDB
451 /* Allow kdb to debug itself one level */
452 return 0;
453#endif
454 dump_stack();
455 panic("Recursive entry to debugger");
456
457 return 1;
458}
459
460static void dbg_touch_watchdogs(void)
461{
462 touch_softlockup_watchdog_sync();
463 clocksource_touch_watchdog();
464 rcu_cpu_stall_reset();
465}
466
467static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
468 int exception_state)
469{
470 unsigned long flags;
471 int sstep_tries = 100;
472 int error;
473 int cpu;
474 int trace_on = 0;
475 int online_cpus = num_online_cpus();
476 u64 time_left;
477
478 kgdb_info[ks->cpu].enter_kgdb++;
479 kgdb_info[ks->cpu].exception_state |= exception_state;
480
481 if (exception_state == DCPU_WANT_MASTER)
482 atomic_inc(&masters_in_kgdb);
483 else
484 atomic_inc(&slaves_in_kgdb);
485
486 if (arch_kgdb_ops.disable_hw_break)
487 arch_kgdb_ops.disable_hw_break(regs);
488
489acquirelock:
490 /*
491 * Interrupts will be restored by the 'trap return' code, except when
492 * single stepping.
493 */
494 local_irq_save(flags);
495
496 cpu = ks->cpu;
497 kgdb_info[cpu].debuggerinfo = regs;
498 kgdb_info[cpu].task = current;
499 kgdb_info[cpu].ret_state = 0;
500 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
501
502 /* Make sure the above info reaches the primary CPU */
503 smp_mb();
504
505 if (exception_level == 1) {
506 if (raw_spin_trylock(&dbg_master_lock))
507 atomic_xchg(&kgdb_active, cpu);
508 goto cpu_master_loop;
509 }
510
511 /*
512 * CPU will loop if it is a slave or request to become a kgdb
513 * master cpu and acquire the kgdb_active lock:
514 */
515 while (1) {
516cpu_loop:
517 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
518 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
519 goto cpu_master_loop;
520 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
521 if (raw_spin_trylock(&dbg_master_lock)) {
522 atomic_xchg(&kgdb_active, cpu);
523 break;
524 }
525 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
526 if (!raw_spin_is_locked(&dbg_slave_lock))
527 goto return_normal;
528 } else {
529return_normal:
530 /* Return to normal operation by executing any
531 * hw breakpoint fixup.
532 */
533 if (arch_kgdb_ops.correct_hw_break)
534 arch_kgdb_ops.correct_hw_break();
535 if (trace_on)
536 tracing_on();
537 kgdb_info[cpu].exception_state &=
538 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
539 kgdb_info[cpu].enter_kgdb--;
540 smp_mb__before_atomic();
541 atomic_dec(&slaves_in_kgdb);
542 dbg_touch_watchdogs();
543 local_irq_restore(flags);
544 return 0;
545 }
546 cpu_relax();
547 }
548
549 /*
550 * For single stepping, try to only enter on the processor
551 * that was single stepping. To guard against a deadlock, the
552 * kernel will only try for the value of sstep_tries before
553 * giving up and continuing on.
554 */
555 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
556 (kgdb_info[cpu].task &&
557 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
558 atomic_set(&kgdb_active, -1);
559 raw_spin_unlock(&dbg_master_lock);
560 dbg_touch_watchdogs();
561 local_irq_restore(flags);
562
563 goto acquirelock;
564 }
565
566 if (!kgdb_io_ready(1)) {
567 kgdb_info[cpu].ret_state = 1;
568 goto kgdb_restore; /* No I/O connection, resume the system */
569 }
570
571 /*
572 * Don't enter if we have hit a removed breakpoint.
573 */
574 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
575 goto kgdb_restore;
576
577 /* Call the I/O driver's pre_exception routine */
578 if (dbg_io_ops->pre_exception)
579 dbg_io_ops->pre_exception();
580
581 /*
582 * Get the passive CPU lock which will hold all the non-primary
583 * CPU in a spin state while the debugger is active
584 */
585 if (!kgdb_single_step)
586 raw_spin_lock(&dbg_slave_lock);
587
588#ifdef CONFIG_SMP
589 /* If send_ready set, slaves are already waiting */
590 if (ks->send_ready)
591 atomic_set(ks->send_ready, 1);
592
593 /* Signal the other CPUs to enter kgdb_wait() */
594 else if ((!kgdb_single_step) && kgdb_do_roundup)
595 kgdb_roundup_cpus(flags);
596#endif
597
598 /*
599 * Wait for the other CPUs to be notified and be waiting for us:
600 */
601 time_left = loops_per_jiffy * HZ;
602 while (kgdb_do_roundup && --time_left &&
603 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
604 online_cpus)
605 cpu_relax();
606 if (!time_left)
607 pr_crit("Timed out waiting for secondary CPUs.\n");
608
609 /*
610 * At this point the primary processor is completely
611 * in the debugger and all secondary CPUs are quiescent
612 */
613 dbg_deactivate_sw_breakpoints();
614 kgdb_single_step = 0;
615 kgdb_contthread = current;
616 exception_level = 0;
617 trace_on = tracing_is_on();
618 if (trace_on)
619 tracing_off();
620
621 while (1) {
622cpu_master_loop:
623 if (dbg_kdb_mode) {
624 kgdb_connected = 1;
625 error = kdb_stub(ks);
626 if (error == -1)
627 continue;
628 kgdb_connected = 0;
629 } else {
630 error = gdb_serial_stub(ks);
631 }
632
633 if (error == DBG_PASS_EVENT) {
634 dbg_kdb_mode = !dbg_kdb_mode;
635 } else if (error == DBG_SWITCH_CPU_EVENT) {
636 kgdb_info[dbg_switch_cpu].exception_state |=
637 DCPU_NEXT_MASTER;
638 goto cpu_loop;
639 } else {
640 kgdb_info[cpu].ret_state = error;
641 break;
642 }
643 }
644
645 /* Call the I/O driver's post_exception routine */
646 if (dbg_io_ops->post_exception)
647 dbg_io_ops->post_exception();
648
649 if (!kgdb_single_step) {
650 raw_spin_unlock(&dbg_slave_lock);
651 /* Wait till all the CPUs have quit from the debugger. */
652 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
653 cpu_relax();
654 }
655
656kgdb_restore:
657 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
658 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
659 if (kgdb_info[sstep_cpu].task)
660 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
661 else
662 kgdb_sstep_pid = 0;
663 }
664 if (arch_kgdb_ops.correct_hw_break)
665 arch_kgdb_ops.correct_hw_break();
666 if (trace_on)
667 tracing_on();
668
669 kgdb_info[cpu].exception_state &=
670 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
671 kgdb_info[cpu].enter_kgdb--;
672 smp_mb__before_atomic();
673 atomic_dec(&masters_in_kgdb);
674 /* Free kgdb_active */
675 atomic_set(&kgdb_active, -1);
676 raw_spin_unlock(&dbg_master_lock);
677 dbg_touch_watchdogs();
678 local_irq_restore(flags);
679
680 return kgdb_info[cpu].ret_state;
681}
682
683/*
684 * kgdb_handle_exception() - main entry point from a kernel exception
685 *
686 * Locking hierarchy:
687 * interface locks, if any (begin_session)
688 * kgdb lock (kgdb_active)
689 */
690int
691kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
692{
693 struct kgdb_state kgdb_var;
694 struct kgdb_state *ks = &kgdb_var;
695 int ret = 0;
696
697 if (arch_kgdb_ops.enable_nmi)
698 arch_kgdb_ops.enable_nmi(0);
699 /*
700 * Avoid entering the debugger if we were triggered due to an oops
701 * but panic_timeout indicates the system should automatically
702 * reboot on panic. We don't want to get stuck waiting for input
703 * on such systems, especially if its "just" an oops.
704 */
705 if (signo != SIGTRAP && panic_timeout)
706 return 1;
707
708 memset(ks, 0, sizeof(struct kgdb_state));
709 ks->cpu = raw_smp_processor_id();
710 ks->ex_vector = evector;
711 ks->signo = signo;
712 ks->err_code = ecode;
713 ks->linux_regs = regs;
714
715 if (kgdb_reenter_check(ks))
716 goto out; /* Ouch, double exception ! */
717 if (kgdb_info[ks->cpu].enter_kgdb != 0)
718 goto out;
719
720 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
721out:
722 if (arch_kgdb_ops.enable_nmi)
723 arch_kgdb_ops.enable_nmi(1);
724 return ret;
725}
726
727/*
728 * GDB places a breakpoint at this function to know dynamically
729 * loaded objects. It's not defined static so that only one instance with this
730 * name exists in the kernel.
731 */
732
733static int module_event(struct notifier_block *self, unsigned long val,
734 void *data)
735{
736 return 0;
737}
738
739static struct notifier_block dbg_module_load_nb = {
740 .notifier_call = module_event,
741};
742
743int kgdb_nmicallback(int cpu, void *regs)
744{
745#ifdef CONFIG_SMP
746 struct kgdb_state kgdb_var;
747 struct kgdb_state *ks = &kgdb_var;
748
749 memset(ks, 0, sizeof(struct kgdb_state));
750 ks->cpu = cpu;
751 ks->linux_regs = regs;
752
753 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
754 raw_spin_is_locked(&dbg_master_lock)) {
755 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
756 return 0;
757 }
758#endif
759 return 1;
760}
761
762int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
763 atomic_t *send_ready)
764{
765#ifdef CONFIG_SMP
766 if (!kgdb_io_ready(0) || !send_ready)
767 return 1;
768
769 if (kgdb_info[cpu].enter_kgdb == 0) {
770 struct kgdb_state kgdb_var;
771 struct kgdb_state *ks = &kgdb_var;
772
773 memset(ks, 0, sizeof(struct kgdb_state));
774 ks->cpu = cpu;
775 ks->ex_vector = trapnr;
776 ks->signo = SIGTRAP;
777 ks->err_code = err_code;
778 ks->linux_regs = regs;
779 ks->send_ready = send_ready;
780 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
781 return 0;
782 }
783#endif
784 return 1;
785}
786
787static void kgdb_console_write(struct console *co, const char *s,
788 unsigned count)
789{
790 unsigned long flags;
791
792 /* If we're debugging, or KGDB has not connected, don't try
793 * and print. */
794 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
795 return;
796
797 local_irq_save(flags);
798 gdbstub_msg_write(s, count);
799 local_irq_restore(flags);
800}
801
802static struct console kgdbcons = {
803 .name = "kgdb",
804 .write = kgdb_console_write,
805 .flags = CON_PRINTBUFFER | CON_ENABLED,
806 .index = -1,
807};
808
809#ifdef CONFIG_MAGIC_SYSRQ
810static void sysrq_handle_dbg(int key)
811{
812 if (!dbg_io_ops) {
813 pr_crit("ERROR: No KGDB I/O module available\n");
814 return;
815 }
816 if (!kgdb_connected) {
817#ifdef CONFIG_KGDB_KDB
818 if (!dbg_kdb_mode)
819 pr_crit("KGDB or $3#33 for KDB\n");
820#else
821 pr_crit("Entering KGDB\n");
822#endif
823 }
824
825 kgdb_breakpoint();
826}
827
828static struct sysrq_key_op sysrq_dbg_op = {
829 .handler = sysrq_handle_dbg,
830 .help_msg = "debug(g)",
831 .action_msg = "DEBUG",
832};
833#endif
834
835static int kgdb_panic_event(struct notifier_block *self,
836 unsigned long val,
837 void *data)
838{
839 /*
840 * Avoid entering the debugger if we were triggered due to a panic
841 * We don't want to get stuck waiting for input from user in such case.
842 * panic_timeout indicates the system should automatically
843 * reboot on panic.
844 */
845 if (panic_timeout)
846 return NOTIFY_DONE;
847
848 if (dbg_kdb_mode)
849 kdb_printf("PANIC: %s\n", (char *)data);
850 kgdb_breakpoint();
851 return NOTIFY_DONE;
852}
853
854static struct notifier_block kgdb_panic_event_nb = {
855 .notifier_call = kgdb_panic_event,
856 .priority = INT_MAX,
857};
858
859void __weak kgdb_arch_late(void)
860{
861}
862
863void __init dbg_late_init(void)
864{
865 dbg_is_early = false;
866 if (kgdb_io_module_registered)
867 kgdb_arch_late();
868 kdb_init(KDB_INIT_FULL);
869}
870
871static int
872dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
873{
874 /*
875 * Take the following action on reboot notify depending on value:
876 * 1 == Enter debugger
877 * 0 == [the default] detatch debug client
878 * -1 == Do nothing... and use this until the board resets
879 */
880 switch (kgdbreboot) {
881 case 1:
882 kgdb_breakpoint();
883 case -1:
884 goto done;
885 }
886 if (!dbg_kdb_mode)
887 gdbstub_exit(code);
888done:
889 return NOTIFY_DONE;
890}
891
892static struct notifier_block dbg_reboot_notifier = {
893 .notifier_call = dbg_notify_reboot,
894 .next = NULL,
895 .priority = INT_MAX,
896};
897
898static void kgdb_register_callbacks(void)
899{
900 if (!kgdb_io_module_registered) {
901 kgdb_io_module_registered = 1;
902 kgdb_arch_init();
903 if (!dbg_is_early)
904 kgdb_arch_late();
905 register_module_notifier(&dbg_module_load_nb);
906 register_reboot_notifier(&dbg_reboot_notifier);
907 atomic_notifier_chain_register(&panic_notifier_list,
908 &kgdb_panic_event_nb);
909#ifdef CONFIG_MAGIC_SYSRQ
910 register_sysrq_key('g', &sysrq_dbg_op);
911#endif
912 if (kgdb_use_con && !kgdb_con_registered) {
913 register_console(&kgdbcons);
914 kgdb_con_registered = 1;
915 }
916 }
917}
918
919static void kgdb_unregister_callbacks(void)
920{
921 /*
922 * When this routine is called KGDB should unregister from the
923 * panic handler and clean up, making sure it is not handling any
924 * break exceptions at the time.
925 */
926 if (kgdb_io_module_registered) {
927 kgdb_io_module_registered = 0;
928 unregister_reboot_notifier(&dbg_reboot_notifier);
929 unregister_module_notifier(&dbg_module_load_nb);
930 atomic_notifier_chain_unregister(&panic_notifier_list,
931 &kgdb_panic_event_nb);
932 kgdb_arch_exit();
933#ifdef CONFIG_MAGIC_SYSRQ
934 unregister_sysrq_key('g', &sysrq_dbg_op);
935#endif
936 if (kgdb_con_registered) {
937 unregister_console(&kgdbcons);
938 kgdb_con_registered = 0;
939 }
940 }
941}
942
943/*
944 * There are times a tasklet needs to be used vs a compiled in
945 * break point so as to cause an exception outside a kgdb I/O module,
946 * such as is the case with kgdboe, where calling a breakpoint in the
947 * I/O driver itself would be fatal.
948 */
949static void kgdb_tasklet_bpt(unsigned long ing)
950{
951 kgdb_breakpoint();
952 atomic_set(&kgdb_break_tasklet_var, 0);
953}
954
955static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
956
957void kgdb_schedule_breakpoint(void)
958{
959 if (atomic_read(&kgdb_break_tasklet_var) ||
960 atomic_read(&kgdb_active) != -1 ||
961 atomic_read(&kgdb_setting_breakpoint))
962 return;
963 atomic_inc(&kgdb_break_tasklet_var);
964 tasklet_schedule(&kgdb_tasklet_breakpoint);
965}
966EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
967
968static void kgdb_initial_breakpoint(void)
969{
970 kgdb_break_asap = 0;
971
972 pr_crit("Waiting for connection from remote gdb...\n");
973 kgdb_breakpoint();
974}
975
976/**
977 * kgdb_register_io_module - register KGDB IO module
978 * @new_dbg_io_ops: the io ops vector
979 *
980 * Register it with the KGDB core.
981 */
982int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
983{
984 int err;
985
986 spin_lock(&kgdb_registration_lock);
987
988 if (dbg_io_ops) {
989 spin_unlock(&kgdb_registration_lock);
990
991 pr_err("Another I/O driver is already registered with KGDB\n");
992 return -EBUSY;
993 }
994
995 if (new_dbg_io_ops->init) {
996 err = new_dbg_io_ops->init();
997 if (err) {
998 spin_unlock(&kgdb_registration_lock);
999 return err;
1000 }
1001 }
1002
1003 dbg_io_ops = new_dbg_io_ops;
1004
1005 spin_unlock(&kgdb_registration_lock);
1006
1007 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1008
1009 /* Arm KGDB now. */
1010 kgdb_register_callbacks();
1011
1012 if (kgdb_break_asap)
1013 kgdb_initial_breakpoint();
1014
1015 return 0;
1016}
1017EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1018
1019/**
1020 * kkgdb_unregister_io_module - unregister KGDB IO module
1021 * @old_dbg_io_ops: the io ops vector
1022 *
1023 * Unregister it with the KGDB core.
1024 */
1025void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1026{
1027 BUG_ON(kgdb_connected);
1028
1029 /*
1030 * KGDB is no longer able to communicate out, so
1031 * unregister our callbacks and reset state.
1032 */
1033 kgdb_unregister_callbacks();
1034
1035 spin_lock(&kgdb_registration_lock);
1036
1037 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1038 dbg_io_ops = NULL;
1039
1040 spin_unlock(&kgdb_registration_lock);
1041
1042 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1043 old_dbg_io_ops->name);
1044}
1045EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1046
1047int dbg_io_get_char(void)
1048{
1049 int ret = dbg_io_ops->read_char();
1050 if (ret == NO_POLL_CHAR)
1051 return -1;
1052 if (!dbg_kdb_mode)
1053 return ret;
1054 if (ret == 127)
1055 return 8;
1056 return ret;
1057}
1058
1059/**
1060 * kgdb_breakpoint - generate breakpoint exception
1061 *
1062 * This function will generate a breakpoint exception. It is used at the
1063 * beginning of a program to sync up with a debugger and can be used
1064 * otherwise as a quick means to stop program execution and "break" into
1065 * the debugger.
1066 */
1067noinline void kgdb_breakpoint(void)
1068{
1069 atomic_inc(&kgdb_setting_breakpoint);
1070 wmb(); /* Sync point before breakpoint */
1071 arch_kgdb_breakpoint();
1072 wmb(); /* Sync point after breakpoint */
1073 atomic_dec(&kgdb_setting_breakpoint);
1074}
1075EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1076
1077static int __init opt_kgdb_wait(char *str)
1078{
1079 kgdb_break_asap = 1;
1080
1081 kdb_init(KDB_INIT_EARLY);
1082 if (kgdb_io_module_registered)
1083 kgdb_initial_breakpoint();
1084
1085 return 0;
1086}
1087
1088early_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#include <linux/pid_namespace.h>
31#include <linux/clocksource.h>
32#include <linux/interrupt.h>
33#include <linux/spinlock.h>
34#include <linux/console.h>
35#include <linux/threads.h>
36#include <linux/uaccess.h>
37#include <linux/kernel.h>
38#include <linux/module.h>
39#include <linux/ptrace.h>
40#include <linux/string.h>
41#include <linux/delay.h>
42#include <linux/sched.h>
43#include <linux/sysrq.h>
44#include <linux/reboot.h>
45#include <linux/init.h>
46#include <linux/kgdb.h>
47#include <linux/kdb.h>
48#include <linux/pid.h>
49#include <linux/smp.h>
50#include <linux/mm.h>
51#include <linux/rcupdate.h>
52
53#include <asm/cacheflush.h>
54#include <asm/byteorder.h>
55#include <linux/atomic.h>
56
57#include "debug_core.h"
58
59static int kgdb_break_asap;
60
61struct debuggerinfo_struct kgdb_info[NR_CPUS];
62
63/**
64 * kgdb_connected - Is a host GDB connected to us?
65 */
66int kgdb_connected;
67EXPORT_SYMBOL_GPL(kgdb_connected);
68
69/* All the KGDB handlers are installed */
70int kgdb_io_module_registered;
71
72/* Guard for recursive entry */
73static int exception_level;
74
75struct kgdb_io *dbg_io_ops;
76static DEFINE_SPINLOCK(kgdb_registration_lock);
77
78/* Action for the reboot notifiter, a global allow kdb to change it */
79static int kgdbreboot;
80/* kgdb console driver is loaded */
81static int kgdb_con_registered;
82/* determine if kgdb console output should be used */
83static int kgdb_use_con;
84/* Flag for alternate operations for early debugging */
85bool dbg_is_early = true;
86/* Next cpu to become the master debug core */
87int dbg_switch_cpu;
88
89/* Use kdb or gdbserver mode */
90int dbg_kdb_mode = 1;
91
92static int __init opt_kgdb_con(char *str)
93{
94 kgdb_use_con = 1;
95 return 0;
96}
97
98early_param("kgdbcon", opt_kgdb_con);
99
100module_param(kgdb_use_con, int, 0644);
101module_param(kgdbreboot, int, 0644);
102
103/*
104 * Holds information about breakpoints in a kernel. These breakpoints are
105 * added and removed by gdb.
106 */
107static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
108 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
109};
110
111/*
112 * The CPU# of the active CPU, or -1 if none:
113 */
114atomic_t kgdb_active = ATOMIC_INIT(-1);
115EXPORT_SYMBOL_GPL(kgdb_active);
116static DEFINE_RAW_SPINLOCK(dbg_master_lock);
117static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
118
119/*
120 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
121 * bootup code (which might not have percpu set up yet):
122 */
123static atomic_t masters_in_kgdb;
124static atomic_t slaves_in_kgdb;
125static atomic_t kgdb_break_tasklet_var;
126atomic_t kgdb_setting_breakpoint;
127
128struct task_struct *kgdb_usethread;
129struct task_struct *kgdb_contthread;
130
131int kgdb_single_step;
132static pid_t kgdb_sstep_pid;
133
134/* to keep track of the CPU which is doing the single stepping*/
135atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
136
137/*
138 * If you are debugging a problem where roundup (the collection of
139 * all other CPUs) is a problem [this should be extremely rare],
140 * then use the nokgdbroundup option to avoid roundup. In that case
141 * the other CPUs might interfere with your debugging context, so
142 * use this with care:
143 */
144static int kgdb_do_roundup = 1;
145
146static int __init opt_nokgdbroundup(char *str)
147{
148 kgdb_do_roundup = 0;
149
150 return 0;
151}
152
153early_param("nokgdbroundup", opt_nokgdbroundup);
154
155/*
156 * Finally, some KGDB code :-)
157 */
158
159/*
160 * Weak aliases for breakpoint management,
161 * can be overriden by architectures when needed:
162 */
163int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
164{
165 int err;
166
167 err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
168 BREAK_INSTR_SIZE);
169 if (err)
170 return err;
171 err = probe_kernel_write((char *)bpt->bpt_addr,
172 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
173 return err;
174}
175
176int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
177{
178 return probe_kernel_write((char *)bpt->bpt_addr,
179 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
180}
181
182int __weak kgdb_validate_break_address(unsigned long addr)
183{
184 struct kgdb_bkpt tmp;
185 int err;
186 /* Validate setting the breakpoint and then removing it. If the
187 * remove fails, the kernel needs to emit a bad message because we
188 * are deep trouble not being able to put things back the way we
189 * found them.
190 */
191 tmp.bpt_addr = addr;
192 err = kgdb_arch_set_breakpoint(&tmp);
193 if (err)
194 return err;
195 err = kgdb_arch_remove_breakpoint(&tmp);
196 if (err)
197 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
198 "memory destroyed at: %lx", addr);
199 return err;
200}
201
202unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
203{
204 return instruction_pointer(regs);
205}
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}
216
217/*
218 * Some architectures need cache flushes when we set/clear a
219 * breakpoint:
220 */
221static void kgdb_flush_swbreak_addr(unsigned long addr)
222{
223 if (!CACHE_FLUSH_IS_SAFE)
224 return;
225
226 if (current->mm && current->mm->mmap_cache) {
227 flush_cache_range(current->mm->mmap_cache,
228 addr, addr + BREAK_INSTR_SIZE);
229 }
230 /* Force flush instruction cache if it was outside the mm */
231 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
232}
233
234/*
235 * SW breakpoint management:
236 */
237int dbg_activate_sw_breakpoints(void)
238{
239 int error;
240 int ret = 0;
241 int i;
242
243 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
244 if (kgdb_break[i].state != BP_SET)
245 continue;
246
247 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
248 if (error) {
249 ret = error;
250 printk(KERN_INFO "KGDB: BP install failed: %lx",
251 kgdb_break[i].bpt_addr);
252 continue;
253 }
254
255 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
256 kgdb_break[i].state = BP_ACTIVE;
257 }
258 return ret;
259}
260
261int dbg_set_sw_break(unsigned long addr)
262{
263 int err = kgdb_validate_break_address(addr);
264 int breakno = -1;
265 int i;
266
267 if (err)
268 return err;
269
270 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
271 if ((kgdb_break[i].state == BP_SET) &&
272 (kgdb_break[i].bpt_addr == addr))
273 return -EEXIST;
274 }
275 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
276 if (kgdb_break[i].state == BP_REMOVED &&
277 kgdb_break[i].bpt_addr == addr) {
278 breakno = i;
279 break;
280 }
281 }
282
283 if (breakno == -1) {
284 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
285 if (kgdb_break[i].state == BP_UNDEFINED) {
286 breakno = i;
287 break;
288 }
289 }
290 }
291
292 if (breakno == -1)
293 return -E2BIG;
294
295 kgdb_break[breakno].state = BP_SET;
296 kgdb_break[breakno].type = BP_BREAKPOINT;
297 kgdb_break[breakno].bpt_addr = addr;
298
299 return 0;
300}
301
302int dbg_deactivate_sw_breakpoints(void)
303{
304 int error;
305 int ret = 0;
306 int i;
307
308 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
309 if (kgdb_break[i].state != BP_ACTIVE)
310 continue;
311 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
312 if (error) {
313 printk(KERN_INFO "KGDB: BP remove failed: %lx\n",
314 kgdb_break[i].bpt_addr);
315 ret = error;
316 }
317
318 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
319 kgdb_break[i].state = BP_SET;
320 }
321 return ret;
322}
323
324int dbg_remove_sw_break(unsigned long addr)
325{
326 int i;
327
328 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
329 if ((kgdb_break[i].state == BP_SET) &&
330 (kgdb_break[i].bpt_addr == addr)) {
331 kgdb_break[i].state = BP_REMOVED;
332 return 0;
333 }
334 }
335 return -ENOENT;
336}
337
338int kgdb_isremovedbreak(unsigned long addr)
339{
340 int i;
341
342 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
343 if ((kgdb_break[i].state == BP_REMOVED) &&
344 (kgdb_break[i].bpt_addr == addr))
345 return 1;
346 }
347 return 0;
348}
349
350int dbg_remove_all_break(void)
351{
352 int error;
353 int i;
354
355 /* Clear memory breakpoints. */
356 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
357 if (kgdb_break[i].state != BP_ACTIVE)
358 goto setundefined;
359 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
360 if (error)
361 printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
362 kgdb_break[i].bpt_addr);
363setundefined:
364 kgdb_break[i].state = BP_UNDEFINED;
365 }
366
367 /* Clear hardware breakpoints. */
368 if (arch_kgdb_ops.remove_all_hw_break)
369 arch_kgdb_ops.remove_all_hw_break();
370
371 return 0;
372}
373
374/*
375 * Return true if there is a valid kgdb I/O module. Also if no
376 * debugger is attached a message can be printed to the console about
377 * waiting for the debugger to attach.
378 *
379 * The print_wait argument is only to be true when called from inside
380 * the core kgdb_handle_exception, because it will wait for the
381 * debugger to attach.
382 */
383static int kgdb_io_ready(int print_wait)
384{
385 if (!dbg_io_ops)
386 return 0;
387 if (kgdb_connected)
388 return 1;
389 if (atomic_read(&kgdb_setting_breakpoint))
390 return 1;
391 if (print_wait) {
392#ifdef CONFIG_KGDB_KDB
393 if (!dbg_kdb_mode)
394 printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
395#else
396 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
397#endif
398 }
399 return 1;
400}
401
402static int kgdb_reenter_check(struct kgdb_state *ks)
403{
404 unsigned long addr;
405
406 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
407 return 0;
408
409 /* Panic on recursive debugger calls: */
410 exception_level++;
411 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
412 dbg_deactivate_sw_breakpoints();
413
414 /*
415 * If the break point removed ok at the place exception
416 * occurred, try to recover and print a warning to the end
417 * user because the user planted a breakpoint in a place that
418 * KGDB needs in order to function.
419 */
420 if (dbg_remove_sw_break(addr) == 0) {
421 exception_level = 0;
422 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
423 dbg_activate_sw_breakpoints();
424 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
425 addr);
426 WARN_ON_ONCE(1);
427
428 return 1;
429 }
430 dbg_remove_all_break();
431 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
432
433 if (exception_level > 1) {
434 dump_stack();
435 panic("Recursive entry to debugger");
436 }
437
438 printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
439#ifdef CONFIG_KGDB_KDB
440 /* Allow kdb to debug itself one level */
441 return 0;
442#endif
443 dump_stack();
444 panic("Recursive entry to debugger");
445
446 return 1;
447}
448
449static void dbg_touch_watchdogs(void)
450{
451 touch_softlockup_watchdog_sync();
452 clocksource_touch_watchdog();
453 rcu_cpu_stall_reset();
454}
455
456static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
457 int exception_state)
458{
459 unsigned long flags;
460 int sstep_tries = 100;
461 int error;
462 int cpu;
463 int trace_on = 0;
464 int online_cpus = num_online_cpus();
465
466 kgdb_info[ks->cpu].enter_kgdb++;
467 kgdb_info[ks->cpu].exception_state |= exception_state;
468
469 if (exception_state == DCPU_WANT_MASTER)
470 atomic_inc(&masters_in_kgdb);
471 else
472 atomic_inc(&slaves_in_kgdb);
473
474 if (arch_kgdb_ops.disable_hw_break)
475 arch_kgdb_ops.disable_hw_break(regs);
476
477acquirelock:
478 /*
479 * Interrupts will be restored by the 'trap return' code, except when
480 * single stepping.
481 */
482 local_irq_save(flags);
483
484 cpu = ks->cpu;
485 kgdb_info[cpu].debuggerinfo = regs;
486 kgdb_info[cpu].task = current;
487 kgdb_info[cpu].ret_state = 0;
488 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
489
490 /* Make sure the above info reaches the primary CPU */
491 smp_mb();
492
493 if (exception_level == 1) {
494 if (raw_spin_trylock(&dbg_master_lock))
495 atomic_xchg(&kgdb_active, cpu);
496 goto cpu_master_loop;
497 }
498
499 /*
500 * CPU will loop if it is a slave or request to become a kgdb
501 * master cpu and acquire the kgdb_active lock:
502 */
503 while (1) {
504cpu_loop:
505 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
506 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
507 goto cpu_master_loop;
508 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
509 if (raw_spin_trylock(&dbg_master_lock)) {
510 atomic_xchg(&kgdb_active, cpu);
511 break;
512 }
513 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
514 if (!raw_spin_is_locked(&dbg_slave_lock))
515 goto return_normal;
516 } else {
517return_normal:
518 /* Return to normal operation by executing any
519 * hw breakpoint fixup.
520 */
521 if (arch_kgdb_ops.correct_hw_break)
522 arch_kgdb_ops.correct_hw_break();
523 if (trace_on)
524 tracing_on();
525 kgdb_info[cpu].exception_state &=
526 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
527 kgdb_info[cpu].enter_kgdb--;
528 smp_mb__before_atomic_dec();
529 atomic_dec(&slaves_in_kgdb);
530 dbg_touch_watchdogs();
531 local_irq_restore(flags);
532 return 0;
533 }
534 cpu_relax();
535 }
536
537 /*
538 * For single stepping, try to only enter on the processor
539 * that was single stepping. To guard against a deadlock, the
540 * kernel will only try for the value of sstep_tries before
541 * giving up and continuing on.
542 */
543 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
544 (kgdb_info[cpu].task &&
545 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
546 atomic_set(&kgdb_active, -1);
547 raw_spin_unlock(&dbg_master_lock);
548 dbg_touch_watchdogs();
549 local_irq_restore(flags);
550
551 goto acquirelock;
552 }
553
554 if (!kgdb_io_ready(1)) {
555 kgdb_info[cpu].ret_state = 1;
556 goto kgdb_restore; /* No I/O connection, resume the system */
557 }
558
559 /*
560 * Don't enter if we have hit a removed breakpoint.
561 */
562 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
563 goto kgdb_restore;
564
565 /* Call the I/O driver's pre_exception routine */
566 if (dbg_io_ops->pre_exception)
567 dbg_io_ops->pre_exception();
568
569 /*
570 * Get the passive CPU lock which will hold all the non-primary
571 * CPU in a spin state while the debugger is active
572 */
573 if (!kgdb_single_step)
574 raw_spin_lock(&dbg_slave_lock);
575
576#ifdef CONFIG_SMP
577 /* Signal the other CPUs to enter kgdb_wait() */
578 if ((!kgdb_single_step) && kgdb_do_roundup)
579 kgdb_roundup_cpus(flags);
580#endif
581
582 /*
583 * Wait for the other CPUs to be notified and be waiting for us:
584 */
585 while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) +
586 atomic_read(&slaves_in_kgdb)) != online_cpus)
587 cpu_relax();
588
589 /*
590 * At this point the primary processor is completely
591 * in the debugger and all secondary CPUs are quiescent
592 */
593 dbg_deactivate_sw_breakpoints();
594 kgdb_single_step = 0;
595 kgdb_contthread = current;
596 exception_level = 0;
597 trace_on = tracing_is_on();
598 if (trace_on)
599 tracing_off();
600
601 while (1) {
602cpu_master_loop:
603 if (dbg_kdb_mode) {
604 kgdb_connected = 1;
605 error = kdb_stub(ks);
606 if (error == -1)
607 continue;
608 kgdb_connected = 0;
609 } else {
610 error = gdb_serial_stub(ks);
611 }
612
613 if (error == DBG_PASS_EVENT) {
614 dbg_kdb_mode = !dbg_kdb_mode;
615 } else if (error == DBG_SWITCH_CPU_EVENT) {
616 kgdb_info[dbg_switch_cpu].exception_state |=
617 DCPU_NEXT_MASTER;
618 goto cpu_loop;
619 } else {
620 kgdb_info[cpu].ret_state = error;
621 break;
622 }
623 }
624
625 /* Call the I/O driver's post_exception routine */
626 if (dbg_io_ops->post_exception)
627 dbg_io_ops->post_exception();
628
629 if (!kgdb_single_step) {
630 raw_spin_unlock(&dbg_slave_lock);
631 /* Wait till all the CPUs have quit from the debugger. */
632 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
633 cpu_relax();
634 }
635
636kgdb_restore:
637 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
638 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
639 if (kgdb_info[sstep_cpu].task)
640 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
641 else
642 kgdb_sstep_pid = 0;
643 }
644 if (arch_kgdb_ops.correct_hw_break)
645 arch_kgdb_ops.correct_hw_break();
646 if (trace_on)
647 tracing_on();
648
649 kgdb_info[cpu].exception_state &=
650 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
651 kgdb_info[cpu].enter_kgdb--;
652 smp_mb__before_atomic_dec();
653 atomic_dec(&masters_in_kgdb);
654 /* Free kgdb_active */
655 atomic_set(&kgdb_active, -1);
656 raw_spin_unlock(&dbg_master_lock);
657 dbg_touch_watchdogs();
658 local_irq_restore(flags);
659
660 return kgdb_info[cpu].ret_state;
661}
662
663/*
664 * kgdb_handle_exception() - main entry point from a kernel exception
665 *
666 * Locking hierarchy:
667 * interface locks, if any (begin_session)
668 * kgdb lock (kgdb_active)
669 */
670int
671kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
672{
673 struct kgdb_state kgdb_var;
674 struct kgdb_state *ks = &kgdb_var;
675
676 ks->cpu = raw_smp_processor_id();
677 ks->ex_vector = evector;
678 ks->signo = signo;
679 ks->err_code = ecode;
680 ks->kgdb_usethreadid = 0;
681 ks->linux_regs = regs;
682
683 if (kgdb_reenter_check(ks))
684 return 0; /* Ouch, double exception ! */
685 if (kgdb_info[ks->cpu].enter_kgdb != 0)
686 return 0;
687
688 return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
689}
690
691int kgdb_nmicallback(int cpu, void *regs)
692{
693#ifdef CONFIG_SMP
694 struct kgdb_state kgdb_var;
695 struct kgdb_state *ks = &kgdb_var;
696
697 memset(ks, 0, sizeof(struct kgdb_state));
698 ks->cpu = cpu;
699 ks->linux_regs = regs;
700
701 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
702 raw_spin_is_locked(&dbg_master_lock)) {
703 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
704 return 0;
705 }
706#endif
707 return 1;
708}
709
710static void kgdb_console_write(struct console *co, const char *s,
711 unsigned count)
712{
713 unsigned long flags;
714
715 /* If we're debugging, or KGDB has not connected, don't try
716 * and print. */
717 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
718 return;
719
720 local_irq_save(flags);
721 gdbstub_msg_write(s, count);
722 local_irq_restore(flags);
723}
724
725static struct console kgdbcons = {
726 .name = "kgdb",
727 .write = kgdb_console_write,
728 .flags = CON_PRINTBUFFER | CON_ENABLED,
729 .index = -1,
730};
731
732#ifdef CONFIG_MAGIC_SYSRQ
733static void sysrq_handle_dbg(int key)
734{
735 if (!dbg_io_ops) {
736 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
737 return;
738 }
739 if (!kgdb_connected) {
740#ifdef CONFIG_KGDB_KDB
741 if (!dbg_kdb_mode)
742 printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
743#else
744 printk(KERN_CRIT "Entering KGDB\n");
745#endif
746 }
747
748 kgdb_breakpoint();
749}
750
751static struct sysrq_key_op sysrq_dbg_op = {
752 .handler = sysrq_handle_dbg,
753 .help_msg = "debug(G)",
754 .action_msg = "DEBUG",
755};
756#endif
757
758static int kgdb_panic_event(struct notifier_block *self,
759 unsigned long val,
760 void *data)
761{
762 if (dbg_kdb_mode)
763 kdb_printf("PANIC: %s\n", (char *)data);
764 kgdb_breakpoint();
765 return NOTIFY_DONE;
766}
767
768static struct notifier_block kgdb_panic_event_nb = {
769 .notifier_call = kgdb_panic_event,
770 .priority = INT_MAX,
771};
772
773void __weak kgdb_arch_late(void)
774{
775}
776
777void __init dbg_late_init(void)
778{
779 dbg_is_early = false;
780 if (kgdb_io_module_registered)
781 kgdb_arch_late();
782 kdb_init(KDB_INIT_FULL);
783}
784
785static int
786dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
787{
788 /*
789 * Take the following action on reboot notify depending on value:
790 * 1 == Enter debugger
791 * 0 == [the default] detatch debug client
792 * -1 == Do nothing... and use this until the board resets
793 */
794 switch (kgdbreboot) {
795 case 1:
796 kgdb_breakpoint();
797 case -1:
798 goto done;
799 }
800 if (!dbg_kdb_mode)
801 gdbstub_exit(code);
802done:
803 return NOTIFY_DONE;
804}
805
806static struct notifier_block dbg_reboot_notifier = {
807 .notifier_call = dbg_notify_reboot,
808 .next = NULL,
809 .priority = INT_MAX,
810};
811
812static void kgdb_register_callbacks(void)
813{
814 if (!kgdb_io_module_registered) {
815 kgdb_io_module_registered = 1;
816 kgdb_arch_init();
817 if (!dbg_is_early)
818 kgdb_arch_late();
819 register_reboot_notifier(&dbg_reboot_notifier);
820 atomic_notifier_chain_register(&panic_notifier_list,
821 &kgdb_panic_event_nb);
822#ifdef CONFIG_MAGIC_SYSRQ
823 register_sysrq_key('g', &sysrq_dbg_op);
824#endif
825 if (kgdb_use_con && !kgdb_con_registered) {
826 register_console(&kgdbcons);
827 kgdb_con_registered = 1;
828 }
829 }
830}
831
832static void kgdb_unregister_callbacks(void)
833{
834 /*
835 * When this routine is called KGDB should unregister from the
836 * panic handler and clean up, making sure it is not handling any
837 * break exceptions at the time.
838 */
839 if (kgdb_io_module_registered) {
840 kgdb_io_module_registered = 0;
841 unregister_reboot_notifier(&dbg_reboot_notifier);
842 atomic_notifier_chain_unregister(&panic_notifier_list,
843 &kgdb_panic_event_nb);
844 kgdb_arch_exit();
845#ifdef CONFIG_MAGIC_SYSRQ
846 unregister_sysrq_key('g', &sysrq_dbg_op);
847#endif
848 if (kgdb_con_registered) {
849 unregister_console(&kgdbcons);
850 kgdb_con_registered = 0;
851 }
852 }
853}
854
855/*
856 * There are times a tasklet needs to be used vs a compiled in
857 * break point so as to cause an exception outside a kgdb I/O module,
858 * such as is the case with kgdboe, where calling a breakpoint in the
859 * I/O driver itself would be fatal.
860 */
861static void kgdb_tasklet_bpt(unsigned long ing)
862{
863 kgdb_breakpoint();
864 atomic_set(&kgdb_break_tasklet_var, 0);
865}
866
867static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
868
869void kgdb_schedule_breakpoint(void)
870{
871 if (atomic_read(&kgdb_break_tasklet_var) ||
872 atomic_read(&kgdb_active) != -1 ||
873 atomic_read(&kgdb_setting_breakpoint))
874 return;
875 atomic_inc(&kgdb_break_tasklet_var);
876 tasklet_schedule(&kgdb_tasklet_breakpoint);
877}
878EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
879
880static void kgdb_initial_breakpoint(void)
881{
882 kgdb_break_asap = 0;
883
884 printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
885 kgdb_breakpoint();
886}
887
888/**
889 * kgdb_register_io_module - register KGDB IO module
890 * @new_dbg_io_ops: the io ops vector
891 *
892 * Register it with the KGDB core.
893 */
894int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
895{
896 int err;
897
898 spin_lock(&kgdb_registration_lock);
899
900 if (dbg_io_ops) {
901 spin_unlock(&kgdb_registration_lock);
902
903 printk(KERN_ERR "kgdb: Another I/O driver is already "
904 "registered with KGDB.\n");
905 return -EBUSY;
906 }
907
908 if (new_dbg_io_ops->init) {
909 err = new_dbg_io_ops->init();
910 if (err) {
911 spin_unlock(&kgdb_registration_lock);
912 return err;
913 }
914 }
915
916 dbg_io_ops = new_dbg_io_ops;
917
918 spin_unlock(&kgdb_registration_lock);
919
920 printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
921 new_dbg_io_ops->name);
922
923 /* Arm KGDB now. */
924 kgdb_register_callbacks();
925
926 if (kgdb_break_asap)
927 kgdb_initial_breakpoint();
928
929 return 0;
930}
931EXPORT_SYMBOL_GPL(kgdb_register_io_module);
932
933/**
934 * kkgdb_unregister_io_module - unregister KGDB IO module
935 * @old_dbg_io_ops: the io ops vector
936 *
937 * Unregister it with the KGDB core.
938 */
939void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
940{
941 BUG_ON(kgdb_connected);
942
943 /*
944 * KGDB is no longer able to communicate out, so
945 * unregister our callbacks and reset state.
946 */
947 kgdb_unregister_callbacks();
948
949 spin_lock(&kgdb_registration_lock);
950
951 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
952 dbg_io_ops = NULL;
953
954 spin_unlock(&kgdb_registration_lock);
955
956 printk(KERN_INFO
957 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
958 old_dbg_io_ops->name);
959}
960EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
961
962int dbg_io_get_char(void)
963{
964 int ret = dbg_io_ops->read_char();
965 if (ret == NO_POLL_CHAR)
966 return -1;
967 if (!dbg_kdb_mode)
968 return ret;
969 if (ret == 127)
970 return 8;
971 return ret;
972}
973
974/**
975 * kgdb_breakpoint - generate breakpoint exception
976 *
977 * This function will generate a breakpoint exception. It is used at the
978 * beginning of a program to sync up with a debugger and can be used
979 * otherwise as a quick means to stop program execution and "break" into
980 * the debugger.
981 */
982void kgdb_breakpoint(void)
983{
984 atomic_inc(&kgdb_setting_breakpoint);
985 wmb(); /* Sync point before breakpoint */
986 arch_kgdb_breakpoint();
987 wmb(); /* Sync point after breakpoint */
988 atomic_dec(&kgdb_setting_breakpoint);
989}
990EXPORT_SYMBOL_GPL(kgdb_breakpoint);
991
992static int __init opt_kgdb_wait(char *str)
993{
994 kgdb_break_asap = 1;
995
996 kdb_init(KDB_INIT_EARLY);
997 if (kgdb_io_module_registered)
998 kgdb_initial_breakpoint();
999
1000 return 0;
1001}
1002
1003early_param("kgdbwait", opt_kgdb_wait);