Loading...
1/*
2 * Kernel Debug Core
3 *
4 * Maintainer: Jason Wessel <jason.wessel@windriver.com>
5 *
6 * Copyright (C) 2000-2001 VERITAS Software Corporation.
7 * Copyright (C) 2002-2004 Timesys Corporation
8 * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
9 * Copyright (C) 2004 Pavel Machek <pavel@ucw.cz>
10 * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
11 * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
12 * Copyright (C) 2005-2009 Wind River Systems, Inc.
13 * Copyright (C) 2007 MontaVista Software, Inc.
14 * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
15 *
16 * Contributors at various stages not listed above:
17 * Jason Wessel ( jason.wessel@windriver.com )
18 * George Anzinger <george@mvista.com>
19 * Anurekh Saxena (anurekh.saxena@timesys.com)
20 * Lake Stevens Instrument Division (Glenn Engel)
21 * Jim Kingdon, Cygnus Support.
22 *
23 * Original KGDB stub: David Grothe <dave@gcom.com>,
24 * Tigran Aivazian <tigran@sco.com>
25 *
26 * This file is licensed under the terms of the GNU General Public License
27 * version 2. This program is licensed "as is" without any warranty of any
28 * kind, whether express or implied.
29 */
30
31#define pr_fmt(fmt) "KGDB: " fmt
32
33#include <linux/pid_namespace.h>
34#include <linux/clocksource.h>
35#include <linux/serial_core.h>
36#include <linux/interrupt.h>
37#include <linux/spinlock.h>
38#include <linux/console.h>
39#include <linux/threads.h>
40#include <linux/uaccess.h>
41#include <linux/kernel.h>
42#include <linux/module.h>
43#include <linux/ptrace.h>
44#include <linux/string.h>
45#include <linux/delay.h>
46#include <linux/sched.h>
47#include <linux/sysrq.h>
48#include <linux/reboot.h>
49#include <linux/init.h>
50#include <linux/kgdb.h>
51#include <linux/kdb.h>
52#include <linux/nmi.h>
53#include <linux/pid.h>
54#include <linux/smp.h>
55#include <linux/mm.h>
56#include <linux/vmacache.h>
57#include <linux/rcupdate.h>
58#include <linux/irq.h>
59
60#include <asm/cacheflush.h>
61#include <asm/byteorder.h>
62#include <linux/atomic.h>
63
64#include "debug_core.h"
65
66static int kgdb_break_asap;
67
68struct debuggerinfo_struct kgdb_info[NR_CPUS];
69
70/**
71 * kgdb_connected - Is a host GDB connected to us?
72 */
73int kgdb_connected;
74EXPORT_SYMBOL_GPL(kgdb_connected);
75
76/* All the KGDB handlers are installed */
77int kgdb_io_module_registered;
78
79/* Guard for recursive entry */
80static int exception_level;
81
82struct kgdb_io *dbg_io_ops;
83static DEFINE_SPINLOCK(kgdb_registration_lock);
84
85/* Action for the reboot notifiter, a global allow kdb to change it */
86static int kgdbreboot;
87/* kgdb console driver is loaded */
88static int kgdb_con_registered;
89/* determine if kgdb console output should be used */
90static int kgdb_use_con;
91/* Flag for alternate operations for early debugging */
92bool dbg_is_early = true;
93/* Next cpu to become the master debug core */
94int dbg_switch_cpu;
95
96/* Use kdb or gdbserver mode */
97int dbg_kdb_mode = 1;
98
99static int __init opt_kgdb_con(char *str)
100{
101 kgdb_use_con = 1;
102 return 0;
103}
104
105early_param("kgdbcon", opt_kgdb_con);
106
107module_param(kgdb_use_con, int, 0644);
108module_param(kgdbreboot, int, 0644);
109
110/*
111 * Holds information about breakpoints in a kernel. These breakpoints are
112 * added and removed by gdb.
113 */
114static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
115 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
116};
117
118/*
119 * The CPU# of the active CPU, or -1 if none:
120 */
121atomic_t kgdb_active = ATOMIC_INIT(-1);
122EXPORT_SYMBOL_GPL(kgdb_active);
123static DEFINE_RAW_SPINLOCK(dbg_master_lock);
124static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
125
126/*
127 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
128 * bootup code (which might not have percpu set up yet):
129 */
130static atomic_t masters_in_kgdb;
131static atomic_t slaves_in_kgdb;
132static atomic_t kgdb_break_tasklet_var;
133atomic_t kgdb_setting_breakpoint;
134
135struct task_struct *kgdb_usethread;
136struct task_struct *kgdb_contthread;
137
138int kgdb_single_step;
139static pid_t kgdb_sstep_pid;
140
141/* to keep track of the CPU which is doing the single stepping*/
142atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
143
144/*
145 * If you are debugging a problem where roundup (the collection of
146 * all other CPUs) is a problem [this should be extremely rare],
147 * then use the nokgdbroundup option to avoid roundup. In that case
148 * the other CPUs might interfere with your debugging context, so
149 * use this with care:
150 */
151static int kgdb_do_roundup = 1;
152
153static int __init opt_nokgdbroundup(char *str)
154{
155 kgdb_do_roundup = 0;
156
157 return 0;
158}
159
160early_param("nokgdbroundup", opt_nokgdbroundup);
161
162/*
163 * Finally, some KGDB code :-)
164 */
165
166/*
167 * Weak aliases for breakpoint management,
168 * can be overriden by architectures when needed:
169 */
170int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
171{
172 int err;
173
174 err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
175 BREAK_INSTR_SIZE);
176 if (err)
177 return err;
178 err = probe_kernel_write((char *)bpt->bpt_addr,
179 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
180 return err;
181}
182
183int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
184{
185 return probe_kernel_write((char *)bpt->bpt_addr,
186 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
187}
188
189int __weak kgdb_validate_break_address(unsigned long addr)
190{
191 struct kgdb_bkpt tmp;
192 int err;
193 /* Validate setting the breakpoint and then removing it. If the
194 * remove fails, the kernel needs to emit a bad message because we
195 * are deep trouble not being able to put things back the way we
196 * found them.
197 */
198 tmp.bpt_addr = addr;
199 err = kgdb_arch_set_breakpoint(&tmp);
200 if (err)
201 return err;
202 err = kgdb_arch_remove_breakpoint(&tmp);
203 if (err)
204 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
205 addr);
206 return err;
207}
208
209unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
210{
211 return instruction_pointer(regs);
212}
213
214int __weak kgdb_arch_init(void)
215{
216 return 0;
217}
218
219int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
220{
221 return 0;
222}
223
224#ifdef CONFIG_SMP
225
226/*
227 * Default (weak) implementation for kgdb_roundup_cpus
228 */
229
230static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd);
231
232void __weak kgdb_call_nmi_hook(void *ignored)
233{
234 /*
235 * NOTE: get_irq_regs() is supposed to get the registers from
236 * before the IPI interrupt happened and so is supposed to
237 * show where the processor was. In some situations it's
238 * possible we might be called without an IPI, so it might be
239 * safer to figure out how to make kgdb_breakpoint() work
240 * properly here.
241 */
242 kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
243}
244
245void __weak kgdb_roundup_cpus(void)
246{
247 call_single_data_t *csd;
248 int this_cpu = raw_smp_processor_id();
249 int cpu;
250 int ret;
251
252 for_each_online_cpu(cpu) {
253 /* No need to roundup ourselves */
254 if (cpu == this_cpu)
255 continue;
256
257 csd = &per_cpu(kgdb_roundup_csd, cpu);
258
259 /*
260 * If it didn't round up last time, don't try again
261 * since smp_call_function_single_async() will block.
262 *
263 * If rounding_up is false then we know that the
264 * previous call must have at least started and that
265 * means smp_call_function_single_async() won't block.
266 */
267 if (kgdb_info[cpu].rounding_up)
268 continue;
269 kgdb_info[cpu].rounding_up = true;
270
271 csd->func = kgdb_call_nmi_hook;
272 ret = smp_call_function_single_async(cpu, csd);
273 if (ret)
274 kgdb_info[cpu].rounding_up = false;
275 }
276}
277
278#endif
279
280/*
281 * Some architectures need cache flushes when we set/clear a
282 * breakpoint:
283 */
284static void kgdb_flush_swbreak_addr(unsigned long addr)
285{
286 if (!CACHE_FLUSH_IS_SAFE)
287 return;
288
289 if (current->mm) {
290 int i;
291
292 for (i = 0; i < VMACACHE_SIZE; i++) {
293 if (!current->vmacache.vmas[i])
294 continue;
295 flush_cache_range(current->vmacache.vmas[i],
296 addr, addr + BREAK_INSTR_SIZE);
297 }
298 }
299
300 /* Force flush instruction cache if it was outside the mm */
301 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
302}
303
304/*
305 * SW breakpoint management:
306 */
307int dbg_activate_sw_breakpoints(void)
308{
309 int error;
310 int ret = 0;
311 int i;
312
313 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
314 if (kgdb_break[i].state != BP_SET)
315 continue;
316
317 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
318 if (error) {
319 ret = error;
320 pr_info("BP install failed: %lx\n",
321 kgdb_break[i].bpt_addr);
322 continue;
323 }
324
325 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
326 kgdb_break[i].state = BP_ACTIVE;
327 }
328 return ret;
329}
330
331int dbg_set_sw_break(unsigned long addr)
332{
333 int err = kgdb_validate_break_address(addr);
334 int breakno = -1;
335 int i;
336
337 if (err)
338 return err;
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 return -EEXIST;
344 }
345 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
346 if (kgdb_break[i].state == BP_REMOVED &&
347 kgdb_break[i].bpt_addr == addr) {
348 breakno = i;
349 break;
350 }
351 }
352
353 if (breakno == -1) {
354 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
355 if (kgdb_break[i].state == BP_UNDEFINED) {
356 breakno = i;
357 break;
358 }
359 }
360 }
361
362 if (breakno == -1)
363 return -E2BIG;
364
365 kgdb_break[breakno].state = BP_SET;
366 kgdb_break[breakno].type = BP_BREAKPOINT;
367 kgdb_break[breakno].bpt_addr = addr;
368
369 return 0;
370}
371
372int dbg_deactivate_sw_breakpoints(void)
373{
374 int error;
375 int ret = 0;
376 int i;
377
378 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
379 if (kgdb_break[i].state != BP_ACTIVE)
380 continue;
381 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
382 if (error) {
383 pr_info("BP remove failed: %lx\n",
384 kgdb_break[i].bpt_addr);
385 ret = error;
386 }
387
388 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
389 kgdb_break[i].state = BP_SET;
390 }
391 return ret;
392}
393
394int dbg_remove_sw_break(unsigned long addr)
395{
396 int i;
397
398 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
399 if ((kgdb_break[i].state == BP_SET) &&
400 (kgdb_break[i].bpt_addr == addr)) {
401 kgdb_break[i].state = BP_REMOVED;
402 return 0;
403 }
404 }
405 return -ENOENT;
406}
407
408int kgdb_isremovedbreak(unsigned long addr)
409{
410 int i;
411
412 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
413 if ((kgdb_break[i].state == BP_REMOVED) &&
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
444/*
445 * Return true if there is a valid kgdb I/O module. Also if no
446 * debugger is attached a message can be printed to the console about
447 * waiting for the debugger to attach.
448 *
449 * The print_wait argument is only to be true when called from inside
450 * the core kgdb_handle_exception, because it will wait for the
451 * debugger to attach.
452 */
453static int kgdb_io_ready(int print_wait)
454{
455 if (!dbg_io_ops)
456 return 0;
457 if (kgdb_connected)
458 return 1;
459 if (atomic_read(&kgdb_setting_breakpoint))
460 return 1;
461 if (print_wait) {
462#ifdef CONFIG_KGDB_KDB
463 if (!dbg_kdb_mode)
464 pr_crit("waiting... or $3#33 for KDB\n");
465#else
466 pr_crit("Waiting for remote debugger\n");
467#endif
468 }
469 return 1;
470}
471
472static int kgdb_reenter_check(struct kgdb_state *ks)
473{
474 unsigned long addr;
475
476 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
477 return 0;
478
479 /* Panic on recursive debugger calls: */
480 exception_level++;
481 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
482 dbg_deactivate_sw_breakpoints();
483
484 /*
485 * If the break point removed ok at the place exception
486 * occurred, try to recover and print a warning to the end
487 * user because the user planted a breakpoint in a place that
488 * KGDB needs in order to function.
489 */
490 if (dbg_remove_sw_break(addr) == 0) {
491 exception_level = 0;
492 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
493 dbg_activate_sw_breakpoints();
494 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
495 WARN_ON_ONCE(1);
496
497 return 1;
498 }
499 dbg_remove_all_break();
500 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
501
502 if (exception_level > 1) {
503 dump_stack();
504 panic("Recursive entry to debugger");
505 }
506
507 pr_crit("re-enter exception: ALL breakpoints killed\n");
508#ifdef CONFIG_KGDB_KDB
509 /* Allow kdb to debug itself one level */
510 return 0;
511#endif
512 dump_stack();
513 panic("Recursive entry to debugger");
514
515 return 1;
516}
517
518static void dbg_touch_watchdogs(void)
519{
520 touch_softlockup_watchdog_sync();
521 clocksource_touch_watchdog();
522 rcu_cpu_stall_reset();
523}
524
525static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
526 int exception_state)
527{
528 unsigned long flags;
529 int sstep_tries = 100;
530 int error;
531 int cpu;
532 int trace_on = 0;
533 int online_cpus = num_online_cpus();
534 u64 time_left;
535
536 kgdb_info[ks->cpu].enter_kgdb++;
537 kgdb_info[ks->cpu].exception_state |= exception_state;
538
539 if (exception_state == DCPU_WANT_MASTER)
540 atomic_inc(&masters_in_kgdb);
541 else
542 atomic_inc(&slaves_in_kgdb);
543
544 if (arch_kgdb_ops.disable_hw_break)
545 arch_kgdb_ops.disable_hw_break(regs);
546
547acquirelock:
548 /*
549 * Interrupts will be restored by the 'trap return' code, except when
550 * single stepping.
551 */
552 local_irq_save(flags);
553
554 cpu = ks->cpu;
555 kgdb_info[cpu].debuggerinfo = regs;
556 kgdb_info[cpu].task = current;
557 kgdb_info[cpu].ret_state = 0;
558 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
559
560 /* Make sure the above info reaches the primary CPU */
561 smp_mb();
562
563 if (exception_level == 1) {
564 if (raw_spin_trylock(&dbg_master_lock))
565 atomic_xchg(&kgdb_active, cpu);
566 goto cpu_master_loop;
567 }
568
569 /*
570 * CPU will loop if it is a slave or request to become a kgdb
571 * master cpu and acquire the kgdb_active lock:
572 */
573 while (1) {
574cpu_loop:
575 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
576 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
577 goto cpu_master_loop;
578 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
579 if (raw_spin_trylock(&dbg_master_lock)) {
580 atomic_xchg(&kgdb_active, cpu);
581 break;
582 }
583 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
584 if (!raw_spin_is_locked(&dbg_slave_lock))
585 goto return_normal;
586 } else {
587return_normal:
588 /* Return to normal operation by executing any
589 * hw breakpoint fixup.
590 */
591 if (arch_kgdb_ops.correct_hw_break)
592 arch_kgdb_ops.correct_hw_break();
593 if (trace_on)
594 tracing_on();
595 kgdb_info[cpu].debuggerinfo = NULL;
596 kgdb_info[cpu].task = NULL;
597 kgdb_info[cpu].exception_state &=
598 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
599 kgdb_info[cpu].enter_kgdb--;
600 smp_mb__before_atomic();
601 atomic_dec(&slaves_in_kgdb);
602 dbg_touch_watchdogs();
603 local_irq_restore(flags);
604 return 0;
605 }
606 cpu_relax();
607 }
608
609 /*
610 * For single stepping, try to only enter on the processor
611 * that was single stepping. To guard against a deadlock, the
612 * kernel will only try for the value of sstep_tries before
613 * giving up and continuing on.
614 */
615 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
616 (kgdb_info[cpu].task &&
617 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
618 atomic_set(&kgdb_active, -1);
619 raw_spin_unlock(&dbg_master_lock);
620 dbg_touch_watchdogs();
621 local_irq_restore(flags);
622
623 goto acquirelock;
624 }
625
626 if (!kgdb_io_ready(1)) {
627 kgdb_info[cpu].ret_state = 1;
628 goto kgdb_restore; /* No I/O connection, resume the system */
629 }
630
631 /*
632 * Don't enter if we have hit a removed breakpoint.
633 */
634 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
635 goto kgdb_restore;
636
637 /* Call the I/O driver's pre_exception routine */
638 if (dbg_io_ops->pre_exception)
639 dbg_io_ops->pre_exception();
640
641 /*
642 * Get the passive CPU lock which will hold all the non-primary
643 * CPU in a spin state while the debugger is active
644 */
645 if (!kgdb_single_step)
646 raw_spin_lock(&dbg_slave_lock);
647
648#ifdef CONFIG_SMP
649 /* If send_ready set, slaves are already waiting */
650 if (ks->send_ready)
651 atomic_set(ks->send_ready, 1);
652
653 /* Signal the other CPUs to enter kgdb_wait() */
654 else if ((!kgdb_single_step) && kgdb_do_roundup)
655 kgdb_roundup_cpus();
656#endif
657
658 /*
659 * Wait for the other CPUs to be notified and be waiting for us:
660 */
661 time_left = MSEC_PER_SEC;
662 while (kgdb_do_roundup && --time_left &&
663 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
664 online_cpus)
665 udelay(1000);
666 if (!time_left)
667 pr_crit("Timed out waiting for secondary CPUs.\n");
668
669 /*
670 * At this point the primary processor is completely
671 * in the debugger and all secondary CPUs are quiescent
672 */
673 dbg_deactivate_sw_breakpoints();
674 kgdb_single_step = 0;
675 kgdb_contthread = current;
676 exception_level = 0;
677 trace_on = tracing_is_on();
678 if (trace_on)
679 tracing_off();
680
681 while (1) {
682cpu_master_loop:
683 if (dbg_kdb_mode) {
684 kgdb_connected = 1;
685 error = kdb_stub(ks);
686 if (error == -1)
687 continue;
688 kgdb_connected = 0;
689 } else {
690 error = gdb_serial_stub(ks);
691 }
692
693 if (error == DBG_PASS_EVENT) {
694 dbg_kdb_mode = !dbg_kdb_mode;
695 } else if (error == DBG_SWITCH_CPU_EVENT) {
696 kgdb_info[dbg_switch_cpu].exception_state |=
697 DCPU_NEXT_MASTER;
698 goto cpu_loop;
699 } else {
700 kgdb_info[cpu].ret_state = error;
701 break;
702 }
703 }
704
705 /* Call the I/O driver's post_exception routine */
706 if (dbg_io_ops->post_exception)
707 dbg_io_ops->post_exception();
708
709 if (!kgdb_single_step) {
710 raw_spin_unlock(&dbg_slave_lock);
711 /* Wait till all the CPUs have quit from the debugger. */
712 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
713 cpu_relax();
714 }
715
716kgdb_restore:
717 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
718 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
719 if (kgdb_info[sstep_cpu].task)
720 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
721 else
722 kgdb_sstep_pid = 0;
723 }
724 if (arch_kgdb_ops.correct_hw_break)
725 arch_kgdb_ops.correct_hw_break();
726 if (trace_on)
727 tracing_on();
728
729 kgdb_info[cpu].debuggerinfo = NULL;
730 kgdb_info[cpu].task = NULL;
731 kgdb_info[cpu].exception_state &=
732 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
733 kgdb_info[cpu].enter_kgdb--;
734 smp_mb__before_atomic();
735 atomic_dec(&masters_in_kgdb);
736 /* Free kgdb_active */
737 atomic_set(&kgdb_active, -1);
738 raw_spin_unlock(&dbg_master_lock);
739 dbg_touch_watchdogs();
740 local_irq_restore(flags);
741
742 return kgdb_info[cpu].ret_state;
743}
744
745/*
746 * kgdb_handle_exception() - main entry point from a kernel exception
747 *
748 * Locking hierarchy:
749 * interface locks, if any (begin_session)
750 * kgdb lock (kgdb_active)
751 */
752int
753kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
754{
755 struct kgdb_state kgdb_var;
756 struct kgdb_state *ks = &kgdb_var;
757 int ret = 0;
758
759 if (arch_kgdb_ops.enable_nmi)
760 arch_kgdb_ops.enable_nmi(0);
761 /*
762 * Avoid entering the debugger if we were triggered due to an oops
763 * but panic_timeout indicates the system should automatically
764 * reboot on panic. We don't want to get stuck waiting for input
765 * on such systems, especially if its "just" an oops.
766 */
767 if (signo != SIGTRAP && panic_timeout)
768 return 1;
769
770 memset(ks, 0, sizeof(struct kgdb_state));
771 ks->cpu = raw_smp_processor_id();
772 ks->ex_vector = evector;
773 ks->signo = signo;
774 ks->err_code = ecode;
775 ks->linux_regs = regs;
776
777 if (kgdb_reenter_check(ks))
778 goto out; /* Ouch, double exception ! */
779 if (kgdb_info[ks->cpu].enter_kgdb != 0)
780 goto out;
781
782 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
783out:
784 if (arch_kgdb_ops.enable_nmi)
785 arch_kgdb_ops.enable_nmi(1);
786 return ret;
787}
788
789/*
790 * GDB places a breakpoint at this function to know dynamically loaded objects.
791 */
792static int module_event(struct notifier_block *self, unsigned long val,
793 void *data)
794{
795 return 0;
796}
797
798static struct notifier_block dbg_module_load_nb = {
799 .notifier_call = module_event,
800};
801
802int kgdb_nmicallback(int cpu, void *regs)
803{
804#ifdef CONFIG_SMP
805 struct kgdb_state kgdb_var;
806 struct kgdb_state *ks = &kgdb_var;
807
808 kgdb_info[cpu].rounding_up = false;
809
810 memset(ks, 0, sizeof(struct kgdb_state));
811 ks->cpu = cpu;
812 ks->linux_regs = regs;
813
814 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
815 raw_spin_is_locked(&dbg_master_lock)) {
816 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
817 return 0;
818 }
819#endif
820 return 1;
821}
822
823int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
824 atomic_t *send_ready)
825{
826#ifdef CONFIG_SMP
827 if (!kgdb_io_ready(0) || !send_ready)
828 return 1;
829
830 if (kgdb_info[cpu].enter_kgdb == 0) {
831 struct kgdb_state kgdb_var;
832 struct kgdb_state *ks = &kgdb_var;
833
834 memset(ks, 0, sizeof(struct kgdb_state));
835 ks->cpu = cpu;
836 ks->ex_vector = trapnr;
837 ks->signo = SIGTRAP;
838 ks->err_code = err_code;
839 ks->linux_regs = regs;
840 ks->send_ready = send_ready;
841 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
842 return 0;
843 }
844#endif
845 return 1;
846}
847
848static void kgdb_console_write(struct console *co, const char *s,
849 unsigned count)
850{
851 unsigned long flags;
852
853 /* If we're debugging, or KGDB has not connected, don't try
854 * and print. */
855 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
856 return;
857
858 local_irq_save(flags);
859 gdbstub_msg_write(s, count);
860 local_irq_restore(flags);
861}
862
863static struct console kgdbcons = {
864 .name = "kgdb",
865 .write = kgdb_console_write,
866 .flags = CON_PRINTBUFFER | CON_ENABLED,
867 .index = -1,
868};
869
870#ifdef CONFIG_MAGIC_SYSRQ
871static void sysrq_handle_dbg(int key)
872{
873 if (!dbg_io_ops) {
874 pr_crit("ERROR: No KGDB I/O module available\n");
875 return;
876 }
877 if (!kgdb_connected) {
878#ifdef CONFIG_KGDB_KDB
879 if (!dbg_kdb_mode)
880 pr_crit("KGDB or $3#33 for KDB\n");
881#else
882 pr_crit("Entering KGDB\n");
883#endif
884 }
885
886 kgdb_breakpoint();
887}
888
889static struct sysrq_key_op sysrq_dbg_op = {
890 .handler = sysrq_handle_dbg,
891 .help_msg = "debug(g)",
892 .action_msg = "DEBUG",
893};
894#endif
895
896void kgdb_panic(const char *msg)
897{
898 if (!kgdb_io_module_registered)
899 return;
900
901 /*
902 * We don't want to get stuck waiting for input from user if
903 * "panic_timeout" indicates the system should automatically
904 * reboot on panic.
905 */
906 if (panic_timeout)
907 return;
908
909 if (dbg_kdb_mode)
910 kdb_printf("PANIC: %s\n", msg);
911
912 kgdb_breakpoint();
913}
914
915void __weak kgdb_arch_late(void)
916{
917}
918
919void __init dbg_late_init(void)
920{
921 dbg_is_early = false;
922 if (kgdb_io_module_registered)
923 kgdb_arch_late();
924 kdb_init(KDB_INIT_FULL);
925}
926
927static int
928dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
929{
930 /*
931 * Take the following action on reboot notify depending on value:
932 * 1 == Enter debugger
933 * 0 == [the default] detatch debug client
934 * -1 == Do nothing... and use this until the board resets
935 */
936 switch (kgdbreboot) {
937 case 1:
938 kgdb_breakpoint();
939 case -1:
940 goto done;
941 }
942 if (!dbg_kdb_mode)
943 gdbstub_exit(code);
944done:
945 return NOTIFY_DONE;
946}
947
948static struct notifier_block dbg_reboot_notifier = {
949 .notifier_call = dbg_notify_reboot,
950 .next = NULL,
951 .priority = INT_MAX,
952};
953
954static void kgdb_register_callbacks(void)
955{
956 if (!kgdb_io_module_registered) {
957 kgdb_io_module_registered = 1;
958 kgdb_arch_init();
959 if (!dbg_is_early)
960 kgdb_arch_late();
961 register_module_notifier(&dbg_module_load_nb);
962 register_reboot_notifier(&dbg_reboot_notifier);
963#ifdef CONFIG_MAGIC_SYSRQ
964 register_sysrq_key('g', &sysrq_dbg_op);
965#endif
966 if (kgdb_use_con && !kgdb_con_registered) {
967 register_console(&kgdbcons);
968 kgdb_con_registered = 1;
969 }
970 }
971}
972
973static void kgdb_unregister_callbacks(void)
974{
975 /*
976 * When this routine is called KGDB should unregister from
977 * handlers and clean up, making sure it is not handling any
978 * break exceptions at the time.
979 */
980 if (kgdb_io_module_registered) {
981 kgdb_io_module_registered = 0;
982 unregister_reboot_notifier(&dbg_reboot_notifier);
983 unregister_module_notifier(&dbg_module_load_nb);
984 kgdb_arch_exit();
985#ifdef CONFIG_MAGIC_SYSRQ
986 unregister_sysrq_key('g', &sysrq_dbg_op);
987#endif
988 if (kgdb_con_registered) {
989 unregister_console(&kgdbcons);
990 kgdb_con_registered = 0;
991 }
992 }
993}
994
995/*
996 * There are times a tasklet needs to be used vs a compiled in
997 * break point so as to cause an exception outside a kgdb I/O module,
998 * such as is the case with kgdboe, where calling a breakpoint in the
999 * I/O driver itself would be fatal.
1000 */
1001static void kgdb_tasklet_bpt(unsigned long ing)
1002{
1003 kgdb_breakpoint();
1004 atomic_set(&kgdb_break_tasklet_var, 0);
1005}
1006
1007static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
1008
1009void kgdb_schedule_breakpoint(void)
1010{
1011 if (atomic_read(&kgdb_break_tasklet_var) ||
1012 atomic_read(&kgdb_active) != -1 ||
1013 atomic_read(&kgdb_setting_breakpoint))
1014 return;
1015 atomic_inc(&kgdb_break_tasklet_var);
1016 tasklet_schedule(&kgdb_tasklet_breakpoint);
1017}
1018EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
1019
1020static void kgdb_initial_breakpoint(void)
1021{
1022 kgdb_break_asap = 0;
1023
1024 pr_crit("Waiting for connection from remote gdb...\n");
1025 kgdb_breakpoint();
1026}
1027
1028/**
1029 * kgdb_register_io_module - register KGDB IO module
1030 * @new_dbg_io_ops: the io ops vector
1031 *
1032 * Register it with the KGDB core.
1033 */
1034int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
1035{
1036 int err;
1037
1038 spin_lock(&kgdb_registration_lock);
1039
1040 if (dbg_io_ops) {
1041 spin_unlock(&kgdb_registration_lock);
1042
1043 pr_err("Another I/O driver is already registered with KGDB\n");
1044 return -EBUSY;
1045 }
1046
1047 if (new_dbg_io_ops->init) {
1048 err = new_dbg_io_ops->init();
1049 if (err) {
1050 spin_unlock(&kgdb_registration_lock);
1051 return err;
1052 }
1053 }
1054
1055 dbg_io_ops = new_dbg_io_ops;
1056
1057 spin_unlock(&kgdb_registration_lock);
1058
1059 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1060
1061 /* Arm KGDB now. */
1062 kgdb_register_callbacks();
1063
1064 if (kgdb_break_asap)
1065 kgdb_initial_breakpoint();
1066
1067 return 0;
1068}
1069EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1070
1071/**
1072 * kkgdb_unregister_io_module - unregister KGDB IO module
1073 * @old_dbg_io_ops: the io ops vector
1074 *
1075 * Unregister it with the KGDB core.
1076 */
1077void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1078{
1079 BUG_ON(kgdb_connected);
1080
1081 /*
1082 * KGDB is no longer able to communicate out, so
1083 * unregister our callbacks and reset state.
1084 */
1085 kgdb_unregister_callbacks();
1086
1087 spin_lock(&kgdb_registration_lock);
1088
1089 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1090 dbg_io_ops = NULL;
1091
1092 spin_unlock(&kgdb_registration_lock);
1093
1094 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1095 old_dbg_io_ops->name);
1096}
1097EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1098
1099int dbg_io_get_char(void)
1100{
1101 int ret = dbg_io_ops->read_char();
1102 if (ret == NO_POLL_CHAR)
1103 return -1;
1104 if (!dbg_kdb_mode)
1105 return ret;
1106 if (ret == 127)
1107 return 8;
1108 return ret;
1109}
1110
1111/**
1112 * kgdb_breakpoint - generate breakpoint exception
1113 *
1114 * This function will generate a breakpoint exception. It is used at the
1115 * beginning of a program to sync up with a debugger and can be used
1116 * otherwise as a quick means to stop program execution and "break" into
1117 * the debugger.
1118 */
1119noinline void kgdb_breakpoint(void)
1120{
1121 atomic_inc(&kgdb_setting_breakpoint);
1122 wmb(); /* Sync point before breakpoint */
1123 arch_kgdb_breakpoint();
1124 wmb(); /* Sync point after breakpoint */
1125 atomic_dec(&kgdb_setting_breakpoint);
1126}
1127EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1128
1129static int __init opt_kgdb_wait(char *str)
1130{
1131 kgdb_break_asap = 1;
1132
1133 kdb_init(KDB_INIT_EARLY);
1134 if (kgdb_io_module_registered)
1135 kgdb_initial_breakpoint();
1136
1137 return 0;
1138}
1139
1140early_param("kgdbwait", opt_kgdb_wait);
1/*
2 * Kernel Debug Core
3 *
4 * Maintainer: Jason Wessel <jason.wessel@windriver.com>
5 *
6 * Copyright (C) 2000-2001 VERITAS Software Corporation.
7 * Copyright (C) 2002-2004 Timesys Corporation
8 * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
9 * Copyright (C) 2004 Pavel Machek <pavel@ucw.cz>
10 * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
11 * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
12 * Copyright (C) 2005-2009 Wind River Systems, Inc.
13 * Copyright (C) 2007 MontaVista Software, Inc.
14 * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
15 *
16 * Contributors at various stages not listed above:
17 * Jason Wessel ( jason.wessel@windriver.com )
18 * George Anzinger <george@mvista.com>
19 * Anurekh Saxena (anurekh.saxena@timesys.com)
20 * Lake Stevens Instrument Division (Glenn Engel)
21 * Jim Kingdon, Cygnus Support.
22 *
23 * Original KGDB stub: David Grothe <dave@gcom.com>,
24 * Tigran Aivazian <tigran@sco.com>
25 *
26 * This file is licensed under the terms of the GNU General Public License
27 * version 2. This program is licensed "as is" without any warranty of any
28 * kind, whether express or implied.
29 */
30
31#define pr_fmt(fmt) "KGDB: " fmt
32
33#include <linux/pid_namespace.h>
34#include <linux/clocksource.h>
35#include <linux/serial_core.h>
36#include <linux/interrupt.h>
37#include <linux/spinlock.h>
38#include <linux/console.h>
39#include <linux/threads.h>
40#include <linux/uaccess.h>
41#include <linux/kernel.h>
42#include <linux/module.h>
43#include <linux/ptrace.h>
44#include <linux/string.h>
45#include <linux/delay.h>
46#include <linux/sched.h>
47#include <linux/sysrq.h>
48#include <linux/reboot.h>
49#include <linux/init.h>
50#include <linux/kgdb.h>
51#include <linux/kdb.h>
52#include <linux/nmi.h>
53#include <linux/pid.h>
54#include <linux/smp.h>
55#include <linux/mm.h>
56#include <linux/vmacache.h>
57#include <linux/rcupdate.h>
58
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);