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
65 static int kgdb_break_asap;
66
67 struct debuggerinfo_struct kgdb_info[NR_CPUS];
68
69 /**
70 * kgdb_connected - Is a host GDB connected to us?
71 */
72 int kgdb_connected;
73 EXPORT_SYMBOL_GPL(kgdb_connected);
74
75 /* All the KGDB handlers are installed */
76 int kgdb_io_module_registered;
77
78 /* Guard for recursive entry */
79 static int exception_level;
80
81 struct kgdb_io *dbg_io_ops;
82 static DEFINE_SPINLOCK(kgdb_registration_lock);
83
84 /* Action for the reboot notifiter, a global allow kdb to change it */
85 static int kgdbreboot;
86 /* kgdb console driver is loaded */
87 static int kgdb_con_registered;
88 /* determine if kgdb console output should be used */
89 static int kgdb_use_con;
90 /* Flag for alternate operations for early debugging */
91 bool dbg_is_early = true;
92 /* Next cpu to become the master debug core */
93 int dbg_switch_cpu;
94
95 /* Use kdb or gdbserver mode */
96 int dbg_kdb_mode = 1;
97
98 module_param(kgdb_use_con, int, 0644);
99 module_param(kgdbreboot, int, 0644);
100
101 /*
102 * Holds information about breakpoints in a kernel. These breakpoints are
103 * added and removed by gdb.
104 */
105 static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
106 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
107 };
108
109 /*
110 * The CPU# of the active CPU, or -1 if none:
111 */
112 atomic_t kgdb_active = ATOMIC_INIT(-1);
113 EXPORT_SYMBOL_GPL(kgdb_active);
114 static DEFINE_RAW_SPINLOCK(dbg_master_lock);
115 static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
116
117 /*
118 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
119 * bootup code (which might not have percpu set up yet):
120 */
121 static atomic_t masters_in_kgdb;
122 static atomic_t slaves_in_kgdb;
123 static atomic_t kgdb_break_tasklet_var;
124 atomic_t kgdb_setting_breakpoint;
125
126 struct task_struct *kgdb_usethread;
127 struct task_struct *kgdb_contthread;
128
129 int kgdb_single_step;
130 static pid_t kgdb_sstep_pid;
131
132 /* to keep track of the CPU which is doing the single stepping*/
133 atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
134
135 /*
136 * If you are debugging a problem where roundup (the collection of
137 * all other CPUs) is a problem [this should be extremely rare],
138 * then use the nokgdbroundup option to avoid roundup. In that case
139 * the other CPUs might interfere with your debugging context, so
140 * use this with care:
141 */
142 static int kgdb_do_roundup = 1;
143
opt_nokgdbroundup(char * str)144 static int __init opt_nokgdbroundup(char *str)
145 {
146 kgdb_do_roundup = 0;
147
148 return 0;
149 }
150
151 early_param("nokgdbroundup", opt_nokgdbroundup);
152
153 /*
154 * Finally, some KGDB code :-)
155 */
156
157 /*
158 * Weak aliases for breakpoint management,
159 * can be overriden by architectures when needed:
160 */
kgdb_arch_set_breakpoint(struct kgdb_bkpt * bpt)161 int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
162 {
163 int err;
164
165 err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
166 BREAK_INSTR_SIZE);
167 if (err)
168 return err;
169 err = probe_kernel_write((char *)bpt->bpt_addr,
170 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
171 return err;
172 }
173
kgdb_arch_remove_breakpoint(struct kgdb_bkpt * bpt)174 int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
175 {
176 return probe_kernel_write((char *)bpt->bpt_addr,
177 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
178 }
179
kgdb_validate_break_address(unsigned long addr)180 int __weak kgdb_validate_break_address(unsigned long addr)
181 {
182 struct kgdb_bkpt tmp;
183 int err;
184 /* Validate setting the breakpoint and then removing it. If the
185 * remove fails, the kernel needs to emit a bad message because we
186 * are deep trouble not being able to put things back the way we
187 * found them.
188 */
189 tmp.bpt_addr = addr;
190 err = kgdb_arch_set_breakpoint(&tmp);
191 if (err)
192 return err;
193 err = kgdb_arch_remove_breakpoint(&tmp);
194 if (err)
195 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
196 addr);
197 return err;
198 }
199
kgdb_arch_pc(int exception,struct pt_regs * regs)200 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
201 {
202 return instruction_pointer(regs);
203 }
204
kgdb_arch_init(void)205 int __weak kgdb_arch_init(void)
206 {
207 return 0;
208 }
209
kgdb_skipexception(int exception,struct pt_regs * regs)210 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
211 {
212 return 0;
213 }
214
215 /*
216 * Some architectures need cache flushes when we set/clear a
217 * breakpoint:
218 */
kgdb_flush_swbreak_addr(unsigned long addr)219 static void kgdb_flush_swbreak_addr(unsigned long addr)
220 {
221 if (!CACHE_FLUSH_IS_SAFE)
222 return;
223
224 if (current->mm) {
225 int i;
226
227 for (i = 0; i < VMACACHE_SIZE; i++) {
228 if (!current->vmacache.vmas[i])
229 continue;
230 flush_cache_range(current->vmacache.vmas[i],
231 addr, addr + BREAK_INSTR_SIZE);
232 }
233 }
234
235 /* Force flush instruction cache if it was outside the mm */
236 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
237 }
238
239 /*
240 * SW breakpoint management:
241 */
dbg_activate_sw_breakpoints(void)242 int dbg_activate_sw_breakpoints(void)
243 {
244 int error;
245 int ret = 0;
246 int i;
247
248 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
249 if (kgdb_break[i].state != BP_SET)
250 continue;
251
252 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
253 if (error) {
254 ret = error;
255 pr_info("BP install failed: %lx\n",
256 kgdb_break[i].bpt_addr);
257 continue;
258 }
259
260 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
261 kgdb_break[i].state = BP_ACTIVE;
262 }
263 return ret;
264 }
265
dbg_set_sw_break(unsigned long addr)266 int dbg_set_sw_break(unsigned long addr)
267 {
268 int err = kgdb_validate_break_address(addr);
269 int breakno = -1;
270 int i;
271
272 if (err)
273 return err;
274
275 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
276 if ((kgdb_break[i].state == BP_SET) &&
277 (kgdb_break[i].bpt_addr == addr))
278 return -EEXIST;
279 }
280 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
281 if (kgdb_break[i].state == BP_REMOVED &&
282 kgdb_break[i].bpt_addr == addr) {
283 breakno = i;
284 break;
285 }
286 }
287
288 if (breakno == -1) {
289 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
290 if (kgdb_break[i].state == BP_UNDEFINED) {
291 breakno = i;
292 break;
293 }
294 }
295 }
296
297 if (breakno == -1)
298 return -E2BIG;
299
300 kgdb_break[breakno].state = BP_SET;
301 kgdb_break[breakno].type = BP_BREAKPOINT;
302 kgdb_break[breakno].bpt_addr = addr;
303
304 return 0;
305 }
306
dbg_deactivate_sw_breakpoints(void)307 int dbg_deactivate_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_ACTIVE)
315 continue;
316 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
317 if (error) {
318 pr_info("BP remove failed: %lx\n",
319 kgdb_break[i].bpt_addr);
320 ret = error;
321 }
322
323 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
324 kgdb_break[i].state = BP_SET;
325 }
326 return ret;
327 }
328
dbg_remove_sw_break(unsigned long addr)329 int dbg_remove_sw_break(unsigned long addr)
330 {
331 int i;
332
333 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
334 if ((kgdb_break[i].state == BP_SET) &&
335 (kgdb_break[i].bpt_addr == addr)) {
336 kgdb_break[i].state = BP_REMOVED;
337 return 0;
338 }
339 }
340 return -ENOENT;
341 }
342
kgdb_isremovedbreak(unsigned long addr)343 int kgdb_isremovedbreak(unsigned long addr)
344 {
345 int i;
346
347 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
348 if ((kgdb_break[i].state == BP_REMOVED) &&
349 (kgdb_break[i].bpt_addr == addr))
350 return 1;
351 }
352 return 0;
353 }
354
dbg_remove_all_break(void)355 int dbg_remove_all_break(void)
356 {
357 int error;
358 int i;
359
360 /* Clear memory breakpoints. */
361 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
362 if (kgdb_break[i].state != BP_ACTIVE)
363 goto setundefined;
364 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
365 if (error)
366 pr_err("breakpoint remove failed: %lx\n",
367 kgdb_break[i].bpt_addr);
368 setundefined:
369 kgdb_break[i].state = BP_UNDEFINED;
370 }
371
372 /* Clear hardware breakpoints. */
373 if (arch_kgdb_ops.remove_all_hw_break)
374 arch_kgdb_ops.remove_all_hw_break();
375
376 return 0;
377 }
378
379 /*
380 * Return true if there is a valid kgdb I/O module. Also if no
381 * debugger is attached a message can be printed to the console about
382 * waiting for the debugger to attach.
383 *
384 * The print_wait argument is only to be true when called from inside
385 * the core kgdb_handle_exception, because it will wait for the
386 * debugger to attach.
387 */
kgdb_io_ready(int print_wait)388 static int kgdb_io_ready(int print_wait)
389 {
390 if (!dbg_io_ops)
391 return 0;
392 if (kgdb_connected)
393 return 1;
394 if (atomic_read(&kgdb_setting_breakpoint))
395 return 1;
396 if (print_wait) {
397 #ifdef CONFIG_KGDB_KDB
398 if (!dbg_kdb_mode)
399 pr_crit("waiting... or $3#33 for KDB\n");
400 #else
401 pr_crit("Waiting for remote debugger\n");
402 #endif
403 }
404 return 1;
405 }
406
kgdb_reenter_check(struct kgdb_state * ks)407 static int kgdb_reenter_check(struct kgdb_state *ks)
408 {
409 unsigned long addr;
410
411 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
412 return 0;
413
414 /* Panic on recursive debugger calls: */
415 exception_level++;
416 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
417 dbg_deactivate_sw_breakpoints();
418
419 /*
420 * If the break point removed ok at the place exception
421 * occurred, try to recover and print a warning to the end
422 * user because the user planted a breakpoint in a place that
423 * KGDB needs in order to function.
424 */
425 if (dbg_remove_sw_break(addr) == 0) {
426 exception_level = 0;
427 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
428 dbg_activate_sw_breakpoints();
429 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
430 WARN_ON_ONCE(1);
431
432 return 1;
433 }
434 dbg_remove_all_break();
435 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
436
437 if (exception_level > 1) {
438 dump_stack();
439 kgdb_io_module_registered = false;
440 panic("Recursive entry to debugger");
441 }
442
443 pr_crit("re-enter exception: ALL breakpoints killed\n");
444 #ifdef CONFIG_KGDB_KDB
445 /* Allow kdb to debug itself one level */
446 return 0;
447 #endif
448 dump_stack();
449 panic("Recursive entry to debugger");
450
451 return 1;
452 }
453
dbg_touch_watchdogs(void)454 static void dbg_touch_watchdogs(void)
455 {
456 touch_softlockup_watchdog_sync();
457 clocksource_touch_watchdog();
458 rcu_cpu_stall_reset();
459 }
460
kgdb_cpu_enter(struct kgdb_state * ks,struct pt_regs * regs,int exception_state)461 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
462 int exception_state)
463 {
464 unsigned long flags;
465 int sstep_tries = 100;
466 int error;
467 int cpu;
468 int trace_on = 0;
469 int online_cpus = num_online_cpus();
470 u64 time_left;
471
472 kgdb_info[ks->cpu].enter_kgdb++;
473 kgdb_info[ks->cpu].exception_state |= exception_state;
474
475 if (exception_state == DCPU_WANT_MASTER)
476 atomic_inc(&masters_in_kgdb);
477 else
478 atomic_inc(&slaves_in_kgdb);
479
480 if (arch_kgdb_ops.disable_hw_break)
481 arch_kgdb_ops.disable_hw_break(regs);
482
483 acquirelock:
484 rcu_read_lock();
485 /*
486 * Interrupts will be restored by the 'trap return' code, except when
487 * single stepping.
488 */
489 local_irq_save(flags);
490
491 cpu = ks->cpu;
492 kgdb_info[cpu].debuggerinfo = regs;
493 kgdb_info[cpu].task = current;
494 kgdb_info[cpu].ret_state = 0;
495 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
496
497 /* Make sure the above info reaches the primary CPU */
498 smp_mb();
499
500 if (exception_level == 1) {
501 if (raw_spin_trylock(&dbg_master_lock))
502 atomic_xchg(&kgdb_active, cpu);
503 goto cpu_master_loop;
504 }
505
506 /*
507 * CPU will loop if it is a slave or request to become a kgdb
508 * master cpu and acquire the kgdb_active lock:
509 */
510 while (1) {
511 cpu_loop:
512 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
513 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
514 goto cpu_master_loop;
515 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
516 if (raw_spin_trylock(&dbg_master_lock)) {
517 atomic_xchg(&kgdb_active, cpu);
518 break;
519 }
520 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
521 if (!raw_spin_is_locked(&dbg_slave_lock))
522 goto return_normal;
523 } else {
524 return_normal:
525 /* Return to normal operation by executing any
526 * hw breakpoint fixup.
527 */
528 if (arch_kgdb_ops.correct_hw_break)
529 arch_kgdb_ops.correct_hw_break();
530 if (trace_on)
531 tracing_on();
532 kgdb_info[cpu].debuggerinfo = NULL;
533 kgdb_info[cpu].task = NULL;
534 kgdb_info[cpu].exception_state &=
535 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
536 kgdb_info[cpu].enter_kgdb--;
537 smp_mb__before_atomic();
538 atomic_dec(&slaves_in_kgdb);
539 dbg_touch_watchdogs();
540 local_irq_restore(flags);
541 rcu_read_unlock();
542 return 0;
543 }
544 cpu_relax();
545 }
546
547 /*
548 * For single stepping, try to only enter on the processor
549 * that was single stepping. To guard against a deadlock, the
550 * kernel will only try for the value of sstep_tries before
551 * giving up and continuing on.
552 */
553 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
554 (kgdb_info[cpu].task &&
555 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
556 atomic_set(&kgdb_active, -1);
557 raw_spin_unlock(&dbg_master_lock);
558 dbg_touch_watchdogs();
559 local_irq_restore(flags);
560 rcu_read_unlock();
561
562 goto acquirelock;
563 }
564
565 if (!kgdb_io_ready(1)) {
566 kgdb_info[cpu].ret_state = 1;
567 goto kgdb_restore; /* No I/O connection, resume the system */
568 }
569
570 /*
571 * Don't enter if we have hit a removed breakpoint.
572 */
573 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
574 goto kgdb_restore;
575
576 atomic_inc(&ignore_console_lock_warning);
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) {
623 cpu_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 atomic_dec(&ignore_console_lock_warning);
651
652 if (!kgdb_single_step) {
653 raw_spin_unlock(&dbg_slave_lock);
654 /* Wait till all the CPUs have quit from the debugger. */
655 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
656 cpu_relax();
657 }
658
659 kgdb_restore:
660 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
661 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
662 if (kgdb_info[sstep_cpu].task)
663 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
664 else
665 kgdb_sstep_pid = 0;
666 }
667 if (arch_kgdb_ops.correct_hw_break)
668 arch_kgdb_ops.correct_hw_break();
669 if (trace_on)
670 tracing_on();
671
672 kgdb_info[cpu].debuggerinfo = NULL;
673 kgdb_info[cpu].task = NULL;
674 kgdb_info[cpu].exception_state &=
675 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
676 kgdb_info[cpu].enter_kgdb--;
677 smp_mb__before_atomic();
678 atomic_dec(&masters_in_kgdb);
679 /* Free kgdb_active */
680 atomic_set(&kgdb_active, -1);
681 raw_spin_unlock(&dbg_master_lock);
682 dbg_touch_watchdogs();
683 local_irq_restore(flags);
684 rcu_read_unlock();
685
686 return kgdb_info[cpu].ret_state;
687 }
688
689 /*
690 * kgdb_handle_exception() - main entry point from a kernel exception
691 *
692 * Locking hierarchy:
693 * interface locks, if any (begin_session)
694 * kgdb lock (kgdb_active)
695 */
696 int
kgdb_handle_exception(int evector,int signo,int ecode,struct pt_regs * regs)697 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
698 {
699 struct kgdb_state kgdb_var;
700 struct kgdb_state *ks = &kgdb_var;
701 int ret = 0;
702
703 if (arch_kgdb_ops.enable_nmi)
704 arch_kgdb_ops.enable_nmi(0);
705 /*
706 * Avoid entering the debugger if we were triggered due to an oops
707 * but panic_timeout indicates the system should automatically
708 * reboot on panic. We don't want to get stuck waiting for input
709 * on such systems, especially if its "just" an oops.
710 */
711 if (signo != SIGTRAP && panic_timeout)
712 return 1;
713
714 memset(ks, 0, sizeof(struct kgdb_state));
715 ks->cpu = raw_smp_processor_id();
716 ks->ex_vector = evector;
717 ks->signo = signo;
718 ks->err_code = ecode;
719 ks->linux_regs = regs;
720
721 if (kgdb_reenter_check(ks))
722 goto out; /* Ouch, double exception ! */
723 if (kgdb_info[ks->cpu].enter_kgdb != 0)
724 goto out;
725
726 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
727 out:
728 if (arch_kgdb_ops.enable_nmi)
729 arch_kgdb_ops.enable_nmi(1);
730 return ret;
731 }
732
733 /*
734 * GDB places a breakpoint at this function to know dynamically
735 * loaded objects. It's not defined static so that only one instance with this
736 * name exists in the kernel.
737 */
738
module_event(struct notifier_block * self,unsigned long val,void * data)739 static int module_event(struct notifier_block *self, unsigned long val,
740 void *data)
741 {
742 return 0;
743 }
744
745 static struct notifier_block dbg_module_load_nb = {
746 .notifier_call = module_event,
747 };
748
kgdb_nmicallback(int cpu,void * regs)749 int kgdb_nmicallback(int cpu, void *regs)
750 {
751 #ifdef CONFIG_SMP
752 struct kgdb_state kgdb_var;
753 struct kgdb_state *ks = &kgdb_var;
754
755 memset(ks, 0, sizeof(struct kgdb_state));
756 ks->cpu = cpu;
757 ks->linux_regs = regs;
758
759 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
760 raw_spin_is_locked(&dbg_master_lock)) {
761 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
762 return 0;
763 }
764 #endif
765 return 1;
766 }
767
kgdb_nmicallin(int cpu,int trapnr,void * regs,int err_code,atomic_t * send_ready)768 int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
769 atomic_t *send_ready)
770 {
771 #ifdef CONFIG_SMP
772 if (!kgdb_io_ready(0) || !send_ready)
773 return 1;
774
775 if (kgdb_info[cpu].enter_kgdb == 0) {
776 struct kgdb_state kgdb_var;
777 struct kgdb_state *ks = &kgdb_var;
778
779 memset(ks, 0, sizeof(struct kgdb_state));
780 ks->cpu = cpu;
781 ks->ex_vector = trapnr;
782 ks->signo = SIGTRAP;
783 ks->err_code = err_code;
784 ks->linux_regs = regs;
785 ks->send_ready = send_ready;
786 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
787 return 0;
788 }
789 #endif
790 return 1;
791 }
792
kgdb_console_write(struct console * co,const char * s,unsigned count)793 static void kgdb_console_write(struct console *co, const char *s,
794 unsigned count)
795 {
796 unsigned long flags;
797
798 /* If we're debugging, or KGDB has not connected, don't try
799 * and print. */
800 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
801 return;
802
803 local_irq_save(flags);
804 gdbstub_msg_write(s, count);
805 local_irq_restore(flags);
806 }
807
808 static struct console kgdbcons = {
809 .name = "kgdb",
810 .write = kgdb_console_write,
811 .flags = CON_PRINTBUFFER | CON_ENABLED,
812 .index = -1,
813 };
814
opt_kgdb_con(char * str)815 static int __init opt_kgdb_con(char *str)
816 {
817 kgdb_use_con = 1;
818
819 if (kgdb_io_module_registered && !kgdb_con_registered) {
820 register_console(&kgdbcons);
821 kgdb_con_registered = 1;
822 }
823
824 return 0;
825 }
826
827 early_param("kgdbcon", opt_kgdb_con);
828
829 #ifdef CONFIG_MAGIC_SYSRQ
sysrq_handle_dbg(int key)830 static void sysrq_handle_dbg(int key)
831 {
832 if (!dbg_io_ops) {
833 pr_crit("ERROR: No KGDB I/O module available\n");
834 return;
835 }
836 if (!kgdb_connected) {
837 #ifdef CONFIG_KGDB_KDB
838 if (!dbg_kdb_mode)
839 pr_crit("KGDB or $3#33 for KDB\n");
840 #else
841 pr_crit("Entering KGDB\n");
842 #endif
843 }
844
845 kgdb_breakpoint();
846 }
847
848 static struct sysrq_key_op sysrq_dbg_op = {
849 .handler = sysrq_handle_dbg,
850 .help_msg = "debug(g)",
851 .action_msg = "DEBUG",
852 };
853 #endif
854
kgdb_panic_event(struct notifier_block * self,unsigned long val,void * data)855 static int kgdb_panic_event(struct notifier_block *self,
856 unsigned long val,
857 void *data)
858 {
859 /*
860 * Avoid entering the debugger if we were triggered due to a panic
861 * We don't want to get stuck waiting for input from user in such case.
862 * panic_timeout indicates the system should automatically
863 * reboot on panic.
864 */
865 if (panic_timeout)
866 return NOTIFY_DONE;
867
868 if (dbg_kdb_mode)
869 kdb_printf("PANIC: %s\n", (char *)data);
870 kgdb_breakpoint();
871 return NOTIFY_DONE;
872 }
873
874 static struct notifier_block kgdb_panic_event_nb = {
875 .notifier_call = kgdb_panic_event,
876 .priority = INT_MAX,
877 };
878
kgdb_arch_late(void)879 void __weak kgdb_arch_late(void)
880 {
881 }
882
dbg_late_init(void)883 void __init dbg_late_init(void)
884 {
885 dbg_is_early = false;
886 if (kgdb_io_module_registered)
887 kgdb_arch_late();
888 kdb_init(KDB_INIT_FULL);
889 }
890
891 static int
dbg_notify_reboot(struct notifier_block * this,unsigned long code,void * x)892 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
893 {
894 /*
895 * Take the following action on reboot notify depending on value:
896 * 1 == Enter debugger
897 * 0 == [the default] detatch debug client
898 * -1 == Do nothing... and use this until the board resets
899 */
900 switch (kgdbreboot) {
901 case 1:
902 kgdb_breakpoint();
903 case -1:
904 goto done;
905 }
906 if (!dbg_kdb_mode)
907 gdbstub_exit(code);
908 done:
909 return NOTIFY_DONE;
910 }
911
912 static struct notifier_block dbg_reboot_notifier = {
913 .notifier_call = dbg_notify_reboot,
914 .next = NULL,
915 .priority = INT_MAX,
916 };
917
kgdb_register_callbacks(void)918 static void kgdb_register_callbacks(void)
919 {
920 if (!kgdb_io_module_registered) {
921 kgdb_io_module_registered = 1;
922 kgdb_arch_init();
923 if (!dbg_is_early)
924 kgdb_arch_late();
925 register_module_notifier(&dbg_module_load_nb);
926 register_reboot_notifier(&dbg_reboot_notifier);
927 atomic_notifier_chain_register(&panic_notifier_list,
928 &kgdb_panic_event_nb);
929 #ifdef CONFIG_MAGIC_SYSRQ
930 register_sysrq_key('g', &sysrq_dbg_op);
931 #endif
932 if (kgdb_use_con && !kgdb_con_registered) {
933 register_console(&kgdbcons);
934 kgdb_con_registered = 1;
935 }
936 }
937 }
938
kgdb_unregister_callbacks(void)939 static void kgdb_unregister_callbacks(void)
940 {
941 /*
942 * When this routine is called KGDB should unregister from the
943 * panic handler and clean up, making sure it is not handling any
944 * break exceptions at the time.
945 */
946 if (kgdb_io_module_registered) {
947 kgdb_io_module_registered = 0;
948 unregister_reboot_notifier(&dbg_reboot_notifier);
949 unregister_module_notifier(&dbg_module_load_nb);
950 atomic_notifier_chain_unregister(&panic_notifier_list,
951 &kgdb_panic_event_nb);
952 kgdb_arch_exit();
953 #ifdef CONFIG_MAGIC_SYSRQ
954 unregister_sysrq_key('g', &sysrq_dbg_op);
955 #endif
956 if (kgdb_con_registered) {
957 unregister_console(&kgdbcons);
958 kgdb_con_registered = 0;
959 }
960 }
961 }
962
963 /*
964 * There are times a tasklet needs to be used vs a compiled in
965 * break point so as to cause an exception outside a kgdb I/O module,
966 * such as is the case with kgdboe, where calling a breakpoint in the
967 * I/O driver itself would be fatal.
968 */
kgdb_tasklet_bpt(unsigned long ing)969 static void kgdb_tasklet_bpt(unsigned long ing)
970 {
971 kgdb_breakpoint();
972 atomic_set(&kgdb_break_tasklet_var, 0);
973 }
974
975 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
976
kgdb_schedule_breakpoint(void)977 void kgdb_schedule_breakpoint(void)
978 {
979 if (atomic_read(&kgdb_break_tasklet_var) ||
980 atomic_read(&kgdb_active) != -1 ||
981 atomic_read(&kgdb_setting_breakpoint))
982 return;
983 atomic_inc(&kgdb_break_tasklet_var);
984 tasklet_schedule(&kgdb_tasklet_breakpoint);
985 }
986 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
987
kgdb_initial_breakpoint(void)988 static void kgdb_initial_breakpoint(void)
989 {
990 kgdb_break_asap = 0;
991
992 pr_crit("Waiting for connection from remote gdb...\n");
993 kgdb_breakpoint();
994 }
995
996 /**
997 * kgdb_register_io_module - register KGDB IO module
998 * @new_dbg_io_ops: the io ops vector
999 *
1000 * Register it with the KGDB core.
1001 */
kgdb_register_io_module(struct kgdb_io * new_dbg_io_ops)1002 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
1003 {
1004 int err;
1005
1006 spin_lock(&kgdb_registration_lock);
1007
1008 if (dbg_io_ops) {
1009 spin_unlock(&kgdb_registration_lock);
1010
1011 pr_err("Another I/O driver is already registered with KGDB\n");
1012 return -EBUSY;
1013 }
1014
1015 if (new_dbg_io_ops->init) {
1016 err = new_dbg_io_ops->init();
1017 if (err) {
1018 spin_unlock(&kgdb_registration_lock);
1019 return err;
1020 }
1021 }
1022
1023 dbg_io_ops = new_dbg_io_ops;
1024
1025 spin_unlock(&kgdb_registration_lock);
1026
1027 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1028
1029 /* Arm KGDB now. */
1030 kgdb_register_callbacks();
1031
1032 if (kgdb_break_asap)
1033 kgdb_initial_breakpoint();
1034
1035 return 0;
1036 }
1037 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1038
1039 /**
1040 * kkgdb_unregister_io_module - unregister KGDB IO module
1041 * @old_dbg_io_ops: the io ops vector
1042 *
1043 * Unregister it with the KGDB core.
1044 */
kgdb_unregister_io_module(struct kgdb_io * old_dbg_io_ops)1045 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1046 {
1047 BUG_ON(kgdb_connected);
1048
1049 /*
1050 * KGDB is no longer able to communicate out, so
1051 * unregister our callbacks and reset state.
1052 */
1053 kgdb_unregister_callbacks();
1054
1055 spin_lock(&kgdb_registration_lock);
1056
1057 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1058 dbg_io_ops = NULL;
1059
1060 spin_unlock(&kgdb_registration_lock);
1061
1062 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1063 old_dbg_io_ops->name);
1064 }
1065 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1066
dbg_io_get_char(void)1067 int dbg_io_get_char(void)
1068 {
1069 int ret = dbg_io_ops->read_char();
1070 if (ret == NO_POLL_CHAR)
1071 return -1;
1072 if (!dbg_kdb_mode)
1073 return ret;
1074 if (ret == 127)
1075 return 8;
1076 return ret;
1077 }
1078
1079 /**
1080 * kgdb_breakpoint - generate breakpoint exception
1081 *
1082 * This function will generate a breakpoint exception. It is used at the
1083 * beginning of a program to sync up with a debugger and can be used
1084 * otherwise as a quick means to stop program execution and "break" into
1085 * the debugger.
1086 */
kgdb_breakpoint(void)1087 noinline void kgdb_breakpoint(void)
1088 {
1089 atomic_inc(&kgdb_setting_breakpoint);
1090 wmb(); /* Sync point before breakpoint */
1091 arch_kgdb_breakpoint();
1092 wmb(); /* Sync point after breakpoint */
1093 atomic_dec(&kgdb_setting_breakpoint);
1094 }
1095 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1096
opt_kgdb_wait(char * str)1097 static int __init opt_kgdb_wait(char *str)
1098 {
1099 kgdb_break_asap = 1;
1100
1101 kdb_init(KDB_INIT_EARLY);
1102 if (kgdb_io_module_registered)
1103 kgdb_initial_breakpoint();
1104
1105 return 0;
1106 }
1107
1108 early_param("kgdbwait", opt_kgdb_wait);
1109