projects/linux·blob 7eec11d3 · refs

1174 lines · 27.3 KiB

1/*
2 * Kernel Debug Core
3 *
4 * Maintainer: Jason Wessel <[email protected]>
5 *
6 * Copyright (C) 2000-2001 VERITAS Software Corporation.
7 * Copyright (C) 2002-2004 Timesys Corporation
8 * Copyright (C) 2003-2004 Amit S. Kale <[email protected]>
9 * Copyright (C) 2004 Pavel Machek <[email protected]>
10 * Copyright (C) 2004-2006 Tom Rini <[email protected]>
11 * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
12 * Copyright (C) 2005-2009 Wind River Systems, Inc.
13 * Copyright (C) 2007 MontaVista Software, Inc.
14 * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <[email protected]>
15 *
16 * Contributors at various stages not listed above:
17 * Jason Wessel ( [email protected] )
18 * George Anzinger <[email protected]>
19 * Anurekh Saxena ([email protected])
20 * Lake Stevens Instrument Division (Glenn Engel)
21 * Jim Kingdon, Cygnus Support.
22 *
23 * Original KGDB stub: David Grothe <[email protected]>,
24 * Tigran Aivazian <[email protected]>
25 *
26 * This file is licensed under the terms of the GNU General Public License
27 * version 2. This program is licensed "as is" without any warranty of any
28 * kind, whether express or implied.
29 */
30
31#define pr_fmt(fmt) "KGDB: " fmt
32
33#include <linux/pid_namespace.h>
34#include <linux/clocksource.h>
35#include <linux/serial_core.h>
36#include <linux/interrupt.h>
37#include <linux/spinlock.h>
38#include <linux/console.h>
39#include <linux/threads.h>
40#include <linux/uaccess.h>
41#include <linux/kernel.h>
42#include <linux/module.h>
43#include <linux/ptrace.h>
44#include <linux/string.h>
45#include <linux/delay.h>
46#include <linux/sched.h>
47#include <linux/sysrq.h>
48#include <linux/reboot.h>
49#include <linux/init.h>
50#include <linux/kgdb.h>
51#include <linux/kdb.h>
52#include <linux/nmi.h>
53#include <linux/pid.h>
54#include <linux/smp.h>
55#include <linux/mm.h>
56#include <linux/vmacache.h>
57#include <linux/rcupdate.h>
58#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#ifdef CONFIG_KGDB_KDB
445void kdb_dump_stack_on_cpu(int cpu)
446{
447 if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) {
448 dump_stack();
449 return;
450 }
451
452 if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) {
453 kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n",
454 cpu);
455 return;
456 }
457
458 /*
459 * In general, architectures don't support dumping the stack of a
460 * "running" process that's not the current one. From the point of
461 * view of the Linux, kernel processes that are looping in the kgdb
462 * slave loop are still "running". There's also no API (that actually
463 * works across all architectures) that can do a stack crawl based
464 * on registers passed as a parameter.
465 *
466 * Solve this conundrum by asking slave CPUs to do the backtrace
467 * themselves.
468 */
469 kgdb_info[cpu].exception_state |= DCPU_WANT_BT;
470 while (kgdb_info[cpu].exception_state & DCPU_WANT_BT)
471 cpu_relax();
472}
473#endif
474
475/*
476 * Return true if there is a valid kgdb I/O module. Also if no
477 * debugger is attached a message can be printed to the console about
478 * waiting for the debugger to attach.
479 *
480 * The print_wait argument is only to be true when called from inside
481 * the core kgdb_handle_exception, because it will wait for the
482 * debugger to attach.
483 */
484static int kgdb_io_ready(int print_wait)
485{
486 if (!dbg_io_ops)
487 return 0;
488 if (kgdb_connected)
489 return 1;
490 if (atomic_read(&kgdb_setting_breakpoint))
491 return 1;
492 if (print_wait) {
493#ifdef CONFIG_KGDB_KDB
494 if (!dbg_kdb_mode)
495 pr_crit("waiting... or $3#33 for KDB\n");
496#else
497 pr_crit("Waiting for remote debugger\n");
498#endif
499 }
500 return 1;
501}
502
503static int kgdb_reenter_check(struct kgdb_state *ks)
504{
505 unsigned long addr;
506
507 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
508 return 0;
509
510 /* Panic on recursive debugger calls: */
511 exception_level++;
512 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
513 dbg_deactivate_sw_breakpoints();
514
515 /*
516 * If the break point removed ok at the place exception
517 * occurred, try to recover and print a warning to the end
518 * user because the user planted a breakpoint in a place that
519 * KGDB needs in order to function.
520 */
521 if (dbg_remove_sw_break(addr) == 0) {
522 exception_level = 0;
523 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
524 dbg_activate_sw_breakpoints();
525 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
526 WARN_ON_ONCE(1);
527
528 return 1;
529 }
530 dbg_remove_all_break();
531 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
532
533 if (exception_level > 1) {
534 dump_stack();
535 panic("Recursive entry to debugger");
536 }
537
538 pr_crit("re-enter exception: ALL breakpoints killed\n");
539#ifdef CONFIG_KGDB_KDB
540 /* Allow kdb to debug itself one level */
541 return 0;
542#endif
543 dump_stack();
544 panic("Recursive entry to debugger");
545
546 return 1;
547}
548
549static void dbg_touch_watchdogs(void)
550{
551 touch_softlockup_watchdog_sync();
552 clocksource_touch_watchdog();
553 rcu_cpu_stall_reset();
554}
555
556static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
557 int exception_state)
558{
559 unsigned long flags;
560 int sstep_tries = 100;
561 int error;
562 int cpu;
563 int trace_on = 0;
564 int online_cpus = num_online_cpus();
565 u64 time_left;
566
567 kgdb_info[ks->cpu].enter_kgdb++;
568 kgdb_info[ks->cpu].exception_state |= exception_state;
569
570 if (exception_state == DCPU_WANT_MASTER)
571 atomic_inc(&masters_in_kgdb);
572 else
573 atomic_inc(&slaves_in_kgdb);
574
575 if (arch_kgdb_ops.disable_hw_break)
576 arch_kgdb_ops.disable_hw_break(regs);
577
578acquirelock:
579 /*
580 * Interrupts will be restored by the 'trap return' code, except when
581 * single stepping.
582 */
583 local_irq_save(flags);
584
585 cpu = ks->cpu;
586 kgdb_info[cpu].debuggerinfo = regs;
587 kgdb_info[cpu].task = current;
588 kgdb_info[cpu].ret_state = 0;
589 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
590
591 /* Make sure the above info reaches the primary CPU */
592 smp_mb();
593
594 if (exception_level == 1) {
595 if (raw_spin_trylock(&dbg_master_lock))
596 atomic_xchg(&kgdb_active, cpu);
597 goto cpu_master_loop;
598 }
599
600 /*
601 * CPU will loop if it is a slave or request to become a kgdb
602 * master cpu and acquire the kgdb_active lock:
603 */
604 while (1) {
605cpu_loop:
606 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
607 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
608 goto cpu_master_loop;
609 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
610 if (raw_spin_trylock(&dbg_master_lock)) {
611 atomic_xchg(&kgdb_active, cpu);
612 break;
613 }
614 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) {
615 dump_stack();
616 kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT;
617 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
618 if (!raw_spin_is_locked(&dbg_slave_lock))
619 goto return_normal;
620 } else {
621return_normal:
622 /* Return to normal operation by executing any
623 * hw breakpoint fixup.
624 */
625 if (arch_kgdb_ops.correct_hw_break)
626 arch_kgdb_ops.correct_hw_break();
627 if (trace_on)
628 tracing_on();
629 kgdb_info[cpu].debuggerinfo = NULL;
630 kgdb_info[cpu].task = NULL;
631 kgdb_info[cpu].exception_state &=
632 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
633 kgdb_info[cpu].enter_kgdb--;
634 smp_mb__before_atomic();
635 atomic_dec(&slaves_in_kgdb);
636 dbg_touch_watchdogs();
637 local_irq_restore(flags);
638 return 0;
639 }
640 cpu_relax();
641 }
642
643 /*
644 * For single stepping, try to only enter on the processor
645 * that was single stepping. To guard against a deadlock, the
646 * kernel will only try for the value of sstep_tries before
647 * giving up and continuing on.
648 */
649 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
650 (kgdb_info[cpu].task &&
651 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
652 atomic_set(&kgdb_active, -1);
653 raw_spin_unlock(&dbg_master_lock);
654 dbg_touch_watchdogs();
655 local_irq_restore(flags);
656
657 goto acquirelock;
658 }
659
660 if (!kgdb_io_ready(1)) {
661 kgdb_info[cpu].ret_state = 1;
662 goto kgdb_restore; /* No I/O connection, resume the system */
663 }
664
665 /*
666 * Don't enter if we have hit a removed breakpoint.
667 */
668 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
669 goto kgdb_restore;
670
671 /* Call the I/O driver's pre_exception routine */
672 if (dbg_io_ops->pre_exception)
673 dbg_io_ops->pre_exception();
674
675 /*
676 * Get the passive CPU lock which will hold all the non-primary
677 * CPU in a spin state while the debugger is active
678 */
679 if (!kgdb_single_step)
680 raw_spin_lock(&dbg_slave_lock);
681
682#ifdef CONFIG_SMP
683 /* If send_ready set, slaves are already waiting */
684 if (ks->send_ready)
685 atomic_set(ks->send_ready, 1);
686
687 /* Signal the other CPUs to enter kgdb_wait() */
688 else if ((!kgdb_single_step) && kgdb_do_roundup)
689 kgdb_roundup_cpus();
690#endif
691
692 /*
693 * Wait for the other CPUs to be notified and be waiting for us:
694 */
695 time_left = MSEC_PER_SEC;
696 while (kgdb_do_roundup && --time_left &&
697 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
698 online_cpus)
699 udelay(1000);
700 if (!time_left)
701 pr_crit("Timed out waiting for secondary CPUs.\n");
702
703 /*
704 * At this point the primary processor is completely
705 * in the debugger and all secondary CPUs are quiescent
706 */
707 dbg_deactivate_sw_breakpoints();
708 kgdb_single_step = 0;
709 kgdb_contthread = current;
710 exception_level = 0;
711 trace_on = tracing_is_on();
712 if (trace_on)
713 tracing_off();
714
715 while (1) {
716cpu_master_loop:
717 if (dbg_kdb_mode) {
718 kgdb_connected = 1;
719 error = kdb_stub(ks);
720 if (error == -1)
721 continue;
722 kgdb_connected = 0;
723 } else {
724 error = gdb_serial_stub(ks);
725 }
726
727 if (error == DBG_PASS_EVENT) {
728 dbg_kdb_mode = !dbg_kdb_mode;
729 } else if (error == DBG_SWITCH_CPU_EVENT) {
730 kgdb_info[dbg_switch_cpu].exception_state |=
731 DCPU_NEXT_MASTER;
732 goto cpu_loop;
733 } else {
734 kgdb_info[cpu].ret_state = error;
735 break;
736 }
737 }
738
739 /* Call the I/O driver's post_exception routine */
740 if (dbg_io_ops->post_exception)
741 dbg_io_ops->post_exception();
742
743 if (!kgdb_single_step) {
744 raw_spin_unlock(&dbg_slave_lock);
745 /* Wait till all the CPUs have quit from the debugger. */
746 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
747 cpu_relax();
748 }
749
750kgdb_restore:
751 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
752 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
753 if (kgdb_info[sstep_cpu].task)
754 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
755 else
756 kgdb_sstep_pid = 0;
757 }
758 if (arch_kgdb_ops.correct_hw_break)
759 arch_kgdb_ops.correct_hw_break();
760 if (trace_on)
761 tracing_on();
762
763 kgdb_info[cpu].debuggerinfo = NULL;
764 kgdb_info[cpu].task = NULL;
765 kgdb_info[cpu].exception_state &=
766 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
767 kgdb_info[cpu].enter_kgdb--;
768 smp_mb__before_atomic();
769 atomic_dec(&masters_in_kgdb);
770 /* Free kgdb_active */
771 atomic_set(&kgdb_active, -1);
772 raw_spin_unlock(&dbg_master_lock);
773 dbg_touch_watchdogs();
774 local_irq_restore(flags);
775
776 return kgdb_info[cpu].ret_state;
777}
778
779/*
780 * kgdb_handle_exception() - main entry point from a kernel exception
781 *
782 * Locking hierarchy:
783 * interface locks, if any (begin_session)
784 * kgdb lock (kgdb_active)
785 */
786int
787kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
788{
789 struct kgdb_state kgdb_var;
790 struct kgdb_state *ks = &kgdb_var;
791 int ret = 0;
792
793 if (arch_kgdb_ops.enable_nmi)
794 arch_kgdb_ops.enable_nmi(0);
795 /*
796 * Avoid entering the debugger if we were triggered due to an oops
797 * but panic_timeout indicates the system should automatically
798 * reboot on panic. We don't want to get stuck waiting for input
799 * on such systems, especially if its "just" an oops.
800 */
801 if (signo != SIGTRAP && panic_timeout)
802 return 1;
803
804 memset(ks, 0, sizeof(struct kgdb_state));
805 ks->cpu = raw_smp_processor_id();
806 ks->ex_vector = evector;
807 ks->signo = signo;
808 ks->err_code = ecode;
809 ks->linux_regs = regs;
810
811 if (kgdb_reenter_check(ks))
812 goto out; /* Ouch, double exception ! */
813 if (kgdb_info[ks->cpu].enter_kgdb != 0)
814 goto out;
815
816 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
817out:
818 if (arch_kgdb_ops.enable_nmi)
819 arch_kgdb_ops.enable_nmi(1);
820 return ret;
821}
822
823/*
824 * GDB places a breakpoint at this function to know dynamically loaded objects.
825 */
826static int module_event(struct notifier_block *self, unsigned long val,
827 void *data)
828{
829 return 0;
830}
831
832static struct notifier_block dbg_module_load_nb = {
833 .notifier_call = module_event,
834};
835
836int kgdb_nmicallback(int cpu, void *regs)
837{
838#ifdef CONFIG_SMP
839 struct kgdb_state kgdb_var;
840 struct kgdb_state *ks = &kgdb_var;
841
842 kgdb_info[cpu].rounding_up = false;
843
844 memset(ks, 0, sizeof(struct kgdb_state));
845 ks->cpu = cpu;
846 ks->linux_regs = regs;
847
848 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
849 raw_spin_is_locked(&dbg_master_lock)) {
850 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
851 return 0;
852 }
853#endif
854 return 1;
855}
856
857int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
858 atomic_t *send_ready)
859{
860#ifdef CONFIG_SMP
861 if (!kgdb_io_ready(0) || !send_ready)
862 return 1;
863
864 if (kgdb_info[cpu].enter_kgdb == 0) {
865 struct kgdb_state kgdb_var;
866 struct kgdb_state *ks = &kgdb_var;
867
868 memset(ks, 0, sizeof(struct kgdb_state));
869 ks->cpu = cpu;
870 ks->ex_vector = trapnr;
871 ks->signo = SIGTRAP;
872 ks->err_code = err_code;
873 ks->linux_regs = regs;
874 ks->send_ready = send_ready;
875 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
876 return 0;
877 }
878#endif
879 return 1;
880}
881
882static void kgdb_console_write(struct console *co, const char *s,
883 unsigned count)
884{
885 unsigned long flags;
886
887 /* If we're debugging, or KGDB has not connected, don't try
888 * and print. */
889 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
890 return;
891
892 local_irq_save(flags);
893 gdbstub_msg_write(s, count);
894 local_irq_restore(flags);
895}
896
897static struct console kgdbcons = {
898 .name = "kgdb",
899 .write = kgdb_console_write,
900 .flags = CON_PRINTBUFFER | CON_ENABLED,
901 .index = -1,
902};
903
904#ifdef CONFIG_MAGIC_SYSRQ
905static void sysrq_handle_dbg(int key)
906{
907 if (!dbg_io_ops) {
908 pr_crit("ERROR: No KGDB I/O module available\n");
909 return;
910 }
911 if (!kgdb_connected) {
912#ifdef CONFIG_KGDB_KDB
913 if (!dbg_kdb_mode)
914 pr_crit("KGDB or $3#33 for KDB\n");
915#else
916 pr_crit("Entering KGDB\n");
917#endif
918 }
919
920 kgdb_breakpoint();
921}
922
923static struct sysrq_key_op sysrq_dbg_op = {
924 .handler = sysrq_handle_dbg,
925 .help_msg = "debug(g)",
926 .action_msg = "DEBUG",
927};
928#endif
929
930void kgdb_panic(const char *msg)
931{
932 if (!kgdb_io_module_registered)
933 return;
934
935 /*
936 * We don't want to get stuck waiting for input from user if
937 * "panic_timeout" indicates the system should automatically
938 * reboot on panic.
939 */
940 if (panic_timeout)
941 return;
942
943 if (dbg_kdb_mode)
944 kdb_printf("PANIC: %s\n", msg);
945
946 kgdb_breakpoint();
947}
948
949void __weak kgdb_arch_late(void)
950{
951}
952
953void __init dbg_late_init(void)
954{
955 dbg_is_early = false;
956 if (kgdb_io_module_registered)
957 kgdb_arch_late();
958 kdb_init(KDB_INIT_FULL);
959}
960
961static int
962dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
963{
964 /*
965 * Take the following action on reboot notify depending on value:
966 * 1 == Enter debugger
967 * 0 == [the default] detatch debug client
968 * -1 == Do nothing... and use this until the board resets
969 */
970 switch (kgdbreboot) {
971 case 1:
972 kgdb_breakpoint();
973 case -1:
974 goto done;
975 }
976 if (!dbg_kdb_mode)
977 gdbstub_exit(code);
978done:
979 return NOTIFY_DONE;
980}
981
982static struct notifier_block dbg_reboot_notifier = {
983 .notifier_call = dbg_notify_reboot,
984 .next = NULL,
985 .priority = INT_MAX,
986};
987
988static void kgdb_register_callbacks(void)
989{
990 if (!kgdb_io_module_registered) {
991 kgdb_io_module_registered = 1;
992 kgdb_arch_init();
993 if (!dbg_is_early)
994 kgdb_arch_late();
995 register_module_notifier(&dbg_module_load_nb);
996 register_reboot_notifier(&dbg_reboot_notifier);
997#ifdef CONFIG_MAGIC_SYSRQ
998 register_sysrq_key('g', &sysrq_dbg_op);
999#endif
1000 if (kgdb_use_con && !kgdb_con_registered) {
1001 register_console(&kgdbcons);
1002 kgdb_con_registered = 1;
1003 }
1004 }
1005}
1006
1007static void kgdb_unregister_callbacks(void)
1008{
1009 /*
1010 * When this routine is called KGDB should unregister from
1011 * handlers and clean up, making sure it is not handling any
1012 * break exceptions at the time.
1013 */
1014 if (kgdb_io_module_registered) {
1015 kgdb_io_module_registered = 0;
1016 unregister_reboot_notifier(&dbg_reboot_notifier);
1017 unregister_module_notifier(&dbg_module_load_nb);
1018 kgdb_arch_exit();
1019#ifdef CONFIG_MAGIC_SYSRQ
1020 unregister_sysrq_key('g', &sysrq_dbg_op);
1021#endif
1022 if (kgdb_con_registered) {
1023 unregister_console(&kgdbcons);
1024 kgdb_con_registered = 0;
1025 }
1026 }
1027}
1028
1029/*
1030 * There are times a tasklet needs to be used vs a compiled in
1031 * break point so as to cause an exception outside a kgdb I/O module,
1032 * such as is the case with kgdboe, where calling a breakpoint in the
1033 * I/O driver itself would be fatal.
1034 */
1035static void kgdb_tasklet_bpt(unsigned long ing)
1036{
1037 kgdb_breakpoint();
1038 atomic_set(&kgdb_break_tasklet_var, 0);
1039}
1040
1041static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
1042
1043void kgdb_schedule_breakpoint(void)
1044{
1045 if (atomic_read(&kgdb_break_tasklet_var) ||
1046 atomic_read(&kgdb_active) != -1 ||
1047 atomic_read(&kgdb_setting_breakpoint))
1048 return;
1049 atomic_inc(&kgdb_break_tasklet_var);
1050 tasklet_schedule(&kgdb_tasklet_breakpoint);
1051}
1052EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
1053
1054static void kgdb_initial_breakpoint(void)
1055{
1056 kgdb_break_asap = 0;
1057
1058 pr_crit("Waiting for connection from remote gdb...\n");
1059 kgdb_breakpoint();
1060}
1061
1062/**
1063 * kgdb_register_io_module - register KGDB IO module
1064 * @new_dbg_io_ops: the io ops vector
1065 *
1066 * Register it with the KGDB core.
1067 */
1068int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
1069{
1070 int err;
1071
1072 spin_lock(&kgdb_registration_lock);
1073
1074 if (dbg_io_ops) {
1075 spin_unlock(&kgdb_registration_lock);
1076
1077 pr_err("Another I/O driver is already registered with KGDB\n");
1078 return -EBUSY;
1079 }
1080
1081 if (new_dbg_io_ops->init) {
1082 err = new_dbg_io_ops->init();
1083 if (err) {
1084 spin_unlock(&kgdb_registration_lock);
1085 return err;
1086 }
1087 }
1088
1089 dbg_io_ops = new_dbg_io_ops;
1090
1091 spin_unlock(&kgdb_registration_lock);
1092
1093 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1094
1095 /* Arm KGDB now. */
1096 kgdb_register_callbacks();
1097
1098 if (kgdb_break_asap)
1099 kgdb_initial_breakpoint();
1100
1101 return 0;
1102}
1103EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1104
1105/**
1106 * kkgdb_unregister_io_module - unregister KGDB IO module
1107 * @old_dbg_io_ops: the io ops vector
1108 *
1109 * Unregister it with the KGDB core.
1110 */
1111void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1112{
1113 BUG_ON(kgdb_connected);
1114
1115 /*
1116 * KGDB is no longer able to communicate out, so
1117 * unregister our callbacks and reset state.
1118 */
1119 kgdb_unregister_callbacks();
1120
1121 spin_lock(&kgdb_registration_lock);
1122
1123 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1124 dbg_io_ops = NULL;
1125
1126 spin_unlock(&kgdb_registration_lock);
1127
1128 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1129 old_dbg_io_ops->name);
1130}
1131EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1132
1133int dbg_io_get_char(void)
1134{
1135 int ret = dbg_io_ops->read_char();
1136 if (ret == NO_POLL_CHAR)
1137 return -1;
1138 if (!dbg_kdb_mode)
1139 return ret;
1140 if (ret == 127)
1141 return 8;
1142 return ret;
1143}
1144
1145/**
1146 * kgdb_breakpoint - generate breakpoint exception
1147 *
1148 * This function will generate a breakpoint exception. It is used at the
1149 * beginning of a program to sync up with a debugger and can be used
1150 * otherwise as a quick means to stop program execution and "break" into
1151 * the debugger.
1152 */
1153noinline void kgdb_breakpoint(void)
1154{
1155 atomic_inc(&kgdb_setting_breakpoint);
1156 wmb(); /* Sync point before breakpoint */
1157 arch_kgdb_breakpoint();
1158 wmb(); /* Sync point after breakpoint */
1159 atomic_dec(&kgdb_setting_breakpoint);
1160}
1161EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1162
1163static int __init opt_kgdb_wait(char *str)
1164{
1165 kgdb_break_asap = 1;
1166
1167 kdb_init(KDB_INIT_EARLY);
1168 if (kgdb_io_module_registered)
1169 kgdb_initial_breakpoint();
1170
1171 return 0;
1172}
1173
1174early_param("kgdbwait", opt_kgdb_wait);