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
59 static int kgdb_break_asap;
60
61 struct debuggerinfo_struct kgdb_info[NR_CPUS];
62
63 /**
64 * kgdb_connected - Is a host GDB connected to us?
65 */
66 int kgdb_connected;
67 EXPORT_SYMBOL_GPL(kgdb_connected);
68
69 /* All the KGDB handlers are installed */
70 int kgdb_io_module_registered;
71
72 /* Guard for recursive entry */
73 static int exception_level;
74
75 struct kgdb_io *dbg_io_ops;
76 static DEFINE_SPINLOCK(kgdb_registration_lock);
77
78 /* Action for the reboot notifiter, a global allow kdb to change it */
79 static int kgdbreboot;
80 /* kgdb console driver is loaded */
81 static int kgdb_con_registered;
82 /* determine if kgdb console output should be used */
83 static int kgdb_use_con;
84 /* Flag for alternate operations for early debugging */
85 bool dbg_is_early = true;
86 /* Next cpu to become the master debug core */
87 int dbg_switch_cpu;
88
89 /* Use kdb or gdbserver mode */
90 int dbg_kdb_mode = 1;
91
opt_kgdb_con(char * str)92 static int __init opt_kgdb_con(char *str)
93 {
94 kgdb_use_con = 1;
95 return 0;
96 }
97
98 early_param("kgdbcon", opt_kgdb_con);
99
100 module_param(kgdb_use_con, int, 0644);
101 module_param(kgdbreboot, int, 0644);
102
103 /*
104 * Holds information about breakpoints in a kernel. These breakpoints are
105 * added and removed by gdb.
106 */
107 static 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 */
114 atomic_t kgdb_active = ATOMIC_INIT(-1);
115 EXPORT_SYMBOL_GPL(kgdb_active);
116 static DEFINE_RAW_SPINLOCK(dbg_master_lock);
117 static 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 */
123 static atomic_t masters_in_kgdb;
124 static atomic_t slaves_in_kgdb;
125 static atomic_t kgdb_break_tasklet_var;
126 atomic_t kgdb_setting_breakpoint;
127
128 struct task_struct *kgdb_usethread;
129 struct task_struct *kgdb_contthread;
130
131 int kgdb_single_step;
132 static pid_t kgdb_sstep_pid;
133
134 /* to keep track of the CPU which is doing the single stepping*/
135 atomic_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 */
144 static int kgdb_do_roundup = 1;
145
opt_nokgdbroundup(char * str)146 static int __init opt_nokgdbroundup(char *str)
147 {
148 kgdb_do_roundup = 0;
149
150 return 0;
151 }
152
153 early_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 */
kgdb_arch_set_breakpoint(struct kgdb_bkpt * bpt)163 int __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
kgdb_arch_remove_breakpoint(struct kgdb_bkpt * bpt)176 int __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
kgdb_validate_break_address(unsigned long addr)182 int __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
kgdb_arch_pc(int exception,struct pt_regs * regs)202 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
203 {
204 return instruction_pointer(regs);
205 }
206
kgdb_arch_init(void)207 int __weak kgdb_arch_init(void)
208 {
209 return 0;
210 }
211
kgdb_skipexception(int exception,struct pt_regs * regs)212 int __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 */
kgdb_flush_swbreak_addr(unsigned long addr)221 static 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 */
dbg_activate_sw_breakpoints(void)237 int 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
dbg_set_sw_break(unsigned long addr)261 int 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
dbg_deactivate_sw_breakpoints(void)302 int 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
dbg_remove_sw_break(unsigned long addr)324 int 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
kgdb_isremovedbreak(unsigned long addr)338 int 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
dbg_remove_all_break(void)350 int 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);
363 setundefined:
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 */
kgdb_io_ready(int print_wait)383 static 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
kgdb_reenter_check(struct kgdb_state * ks)402 static 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
dbg_touch_watchdogs(void)449 static void dbg_touch_watchdogs(void)
450 {
451 touch_softlockup_watchdog_sync();
452 clocksource_touch_watchdog();
453 rcu_cpu_stall_reset();
454 }
455
kgdb_cpu_enter(struct kgdb_state * ks,struct pt_regs * regs,int exception_state)456 static 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
477 acquirelock:
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) {
504 cpu_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 {
517 return_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) {
602 cpu_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
636 kgdb_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 */
670 int
kgdb_handle_exception(int evector,int signo,int ecode,struct pt_regs * regs)671 kgdb_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
kgdb_nmicallback(int cpu,void * regs)691 int 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
kgdb_console_write(struct console * co,const char * s,unsigned count)710 static 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
725 static 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
sysrq_handle_dbg(int key)733 static 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
751 static 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
kgdb_panic_event(struct notifier_block * self,unsigned long val,void * data)758 static 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
768 static struct notifier_block kgdb_panic_event_nb = {
769 .notifier_call = kgdb_panic_event,
770 .priority = INT_MAX,
771 };
772
kgdb_arch_late(void)773 void __weak kgdb_arch_late(void)
774 {
775 }
776
dbg_late_init(void)777 void __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
785 static int
dbg_notify_reboot(struct notifier_block * this,unsigned long code,void * x)786 dbg_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);
802 done:
803 return NOTIFY_DONE;
804 }
805
806 static struct notifier_block dbg_reboot_notifier = {
807 .notifier_call = dbg_notify_reboot,
808 .next = NULL,
809 .priority = INT_MAX,
810 };
811
kgdb_register_callbacks(void)812 static 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
kgdb_unregister_callbacks(void)832 static 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 */
kgdb_tasklet_bpt(unsigned long ing)861 static void kgdb_tasklet_bpt(unsigned long ing)
862 {
863 kgdb_breakpoint();
864 atomic_set(&kgdb_break_tasklet_var, 0);
865 }
866
867 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
868
kgdb_schedule_breakpoint(void)869 void 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 }
878 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
879
kgdb_initial_breakpoint(void)880 static 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 */
kgdb_register_io_module(struct kgdb_io * new_dbg_io_ops)894 int 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 }
931 EXPORT_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 */
kgdb_unregister_io_module(struct kgdb_io * old_dbg_io_ops)939 void 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 }
960 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
961
dbg_io_get_char(void)962 int 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 */
kgdb_breakpoint(void)982 void 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 }
990 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
991
opt_kgdb_wait(char * str)992 static 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
1003 early_param("kgdbwait", opt_kgdb_wait);
1004