Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel...
[linux-2.6.git] / kernel / debug / debug_core.c
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/init.h>
45 #include <linux/kgdb.h>
46 #include <linux/kdb.h>
47 #include <linux/pid.h>
48 #include <linux/smp.h>
49 #include <linux/mm.h>
50
51 #include <asm/cacheflush.h>
52 #include <asm/byteorder.h>
53 #include <asm/atomic.h>
54 #include <asm/system.h>
55
56 #include "debug_core.h"
57
58 static int kgdb_break_asap;
59
60 struct debuggerinfo_struct kgdb_info[NR_CPUS];
61
62 /**
63  * kgdb_connected - Is a host GDB connected to us?
64  */
65 int                             kgdb_connected;
66 EXPORT_SYMBOL_GPL(kgdb_connected);
67
68 /* All the KGDB handlers are installed */
69 int                     kgdb_io_module_registered;
70
71 /* Guard for recursive entry */
72 static int                      exception_level;
73
74 struct kgdb_io          *dbg_io_ops;
75 static DEFINE_SPINLOCK(kgdb_registration_lock);
76
77 /* kgdb console driver is loaded */
78 static int kgdb_con_registered;
79 /* determine if kgdb console output should be used */
80 static int kgdb_use_con;
81 /* Flag for alternate operations for early debugging */
82 bool dbg_is_early = true;
83 /* Next cpu to become the master debug core */
84 int dbg_switch_cpu;
85
86 /* Use kdb or gdbserver mode */
87 int dbg_kdb_mode = 1;
88
89 static int __init opt_kgdb_con(char *str)
90 {
91         kgdb_use_con = 1;
92         return 0;
93 }
94
95 early_param("kgdbcon", opt_kgdb_con);
96
97 module_param(kgdb_use_con, int, 0644);
98
99 /*
100  * Holds information about breakpoints in a kernel. These breakpoints are
101  * added and removed by gdb.
102  */
103 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
104         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
105 };
106
107 /*
108  * The CPU# of the active CPU, or -1 if none:
109  */
110 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
111 EXPORT_SYMBOL_GPL(kgdb_active);
112
113 /*
114  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
115  * bootup code (which might not have percpu set up yet):
116  */
117 static atomic_t                 passive_cpu_wait[NR_CPUS];
118 static atomic_t                 cpu_in_kgdb[NR_CPUS];
119 static atomic_t                 kgdb_break_tasklet_var;
120 atomic_t                        kgdb_setting_breakpoint;
121
122 struct task_struct              *kgdb_usethread;
123 struct task_struct              *kgdb_contthread;
124
125 int                             kgdb_single_step;
126 static pid_t                    kgdb_sstep_pid;
127
128 /* to keep track of the CPU which is doing the single stepping*/
129 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
130
131 /*
132  * If you are debugging a problem where roundup (the collection of
133  * all other CPUs) is a problem [this should be extremely rare],
134  * then use the nokgdbroundup option to avoid roundup. In that case
135  * the other CPUs might interfere with your debugging context, so
136  * use this with care:
137  */
138 static int kgdb_do_roundup = 1;
139
140 static int __init opt_nokgdbroundup(char *str)
141 {
142         kgdb_do_roundup = 0;
143
144         return 0;
145 }
146
147 early_param("nokgdbroundup", opt_nokgdbroundup);
148
149 /*
150  * Finally, some KGDB code :-)
151  */
152
153 /*
154  * Weak aliases for breakpoint management,
155  * can be overriden by architectures when needed:
156  */
157 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
158 {
159         int err;
160
161         err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
162         if (err)
163                 return err;
164
165         return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
166                                   BREAK_INSTR_SIZE);
167 }
168
169 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
170 {
171         return probe_kernel_write((char *)addr,
172                                   (char *)bundle, BREAK_INSTR_SIZE);
173 }
174
175 int __weak kgdb_validate_break_address(unsigned long addr)
176 {
177         char tmp_variable[BREAK_INSTR_SIZE];
178         int err;
179         /* Validate setting the breakpoint and then removing it.  In the
180          * remove fails, the kernel needs to emit a bad message because we
181          * are deep trouble not being able to put things back the way we
182          * found them.
183          */
184         err = kgdb_arch_set_breakpoint(addr, tmp_variable);
185         if (err)
186                 return err;
187         err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
188         if (err)
189                 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
190                    "memory destroyed at: %lx", addr);
191         return err;
192 }
193
194 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
195 {
196         return instruction_pointer(regs);
197 }
198
199 int __weak kgdb_arch_init(void)
200 {
201         return 0;
202 }
203
204 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
205 {
206         return 0;
207 }
208
209 /**
210  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
211  *      @regs: Current &struct pt_regs.
212  *
213  *      This function will be called if the particular architecture must
214  *      disable hardware debugging while it is processing gdb packets or
215  *      handling exception.
216  */
217 void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
218 {
219 }
220
221 /*
222  * Some architectures need cache flushes when we set/clear a
223  * breakpoint:
224  */
225 static void kgdb_flush_swbreak_addr(unsigned long addr)
226 {
227         if (!CACHE_FLUSH_IS_SAFE)
228                 return;
229
230         if (current->mm && current->mm->mmap_cache) {
231                 flush_cache_range(current->mm->mmap_cache,
232                                   addr, addr + BREAK_INSTR_SIZE);
233         }
234         /* Force flush instruction cache if it was outside the mm */
235         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
236 }
237
238 /*
239  * SW breakpoint management:
240  */
241 int dbg_activate_sw_breakpoints(void)
242 {
243         unsigned long addr;
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                 addr = kgdb_break[i].bpt_addr;
253                 error = kgdb_arch_set_breakpoint(addr,
254                                 kgdb_break[i].saved_instr);
255                 if (error) {
256                         ret = error;
257                         printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
258                         continue;
259                 }
260
261                 kgdb_flush_swbreak_addr(addr);
262                 kgdb_break[i].state = BP_ACTIVE;
263         }
264         return ret;
265 }
266
267 int dbg_set_sw_break(unsigned long addr)
268 {
269         int err = kgdb_validate_break_address(addr);
270         int breakno = -1;
271         int i;
272
273         if (err)
274                 return err;
275
276         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
277                 if ((kgdb_break[i].state == BP_SET) &&
278                                         (kgdb_break[i].bpt_addr == addr))
279                         return -EEXIST;
280         }
281         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
282                 if (kgdb_break[i].state == BP_REMOVED &&
283                                         kgdb_break[i].bpt_addr == addr) {
284                         breakno = i;
285                         break;
286                 }
287         }
288
289         if (breakno == -1) {
290                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
291                         if (kgdb_break[i].state == BP_UNDEFINED) {
292                                 breakno = i;
293                                 break;
294                         }
295                 }
296         }
297
298         if (breakno == -1)
299                 return -E2BIG;
300
301         kgdb_break[breakno].state = BP_SET;
302         kgdb_break[breakno].type = BP_BREAKPOINT;
303         kgdb_break[breakno].bpt_addr = addr;
304
305         return 0;
306 }
307
308 int dbg_deactivate_sw_breakpoints(void)
309 {
310         unsigned long addr;
311         int error;
312         int ret = 0;
313         int i;
314
315         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
316                 if (kgdb_break[i].state != BP_ACTIVE)
317                         continue;
318                 addr = kgdb_break[i].bpt_addr;
319                 error = kgdb_arch_remove_breakpoint(addr,
320                                         kgdb_break[i].saved_instr);
321                 if (error) {
322                         printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
323                         ret = error;
324                 }
325
326                 kgdb_flush_swbreak_addr(addr);
327                 kgdb_break[i].state = BP_SET;
328         }
329         return ret;
330 }
331
332 int dbg_remove_sw_break(unsigned long addr)
333 {
334         int i;
335
336         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
337                 if ((kgdb_break[i].state == BP_SET) &&
338                                 (kgdb_break[i].bpt_addr == addr)) {
339                         kgdb_break[i].state = BP_REMOVED;
340                         return 0;
341                 }
342         }
343         return -ENOENT;
344 }
345
346 int kgdb_isremovedbreak(unsigned long addr)
347 {
348         int i;
349
350         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
351                 if ((kgdb_break[i].state == BP_REMOVED) &&
352                                         (kgdb_break[i].bpt_addr == addr))
353                         return 1;
354         }
355         return 0;
356 }
357
358 int dbg_remove_all_break(void)
359 {
360         unsigned long addr;
361         int error;
362         int i;
363
364         /* Clear memory breakpoints. */
365         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
366                 if (kgdb_break[i].state != BP_ACTIVE)
367                         goto setundefined;
368                 addr = kgdb_break[i].bpt_addr;
369                 error = kgdb_arch_remove_breakpoint(addr,
370                                 kgdb_break[i].saved_instr);
371                 if (error)
372                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
373                            addr);
374 setundefined:
375                 kgdb_break[i].state = BP_UNDEFINED;
376         }
377
378         /* Clear hardware breakpoints. */
379         if (arch_kgdb_ops.remove_all_hw_break)
380                 arch_kgdb_ops.remove_all_hw_break();
381
382         return 0;
383 }
384
385 /*
386  * Return true if there is a valid kgdb I/O module.  Also if no
387  * debugger is attached a message can be printed to the console about
388  * waiting for the debugger to attach.
389  *
390  * The print_wait argument is only to be true when called from inside
391  * the core kgdb_handle_exception, because it will wait for the
392  * debugger to attach.
393  */
394 static int kgdb_io_ready(int print_wait)
395 {
396         if (!dbg_io_ops)
397                 return 0;
398         if (kgdb_connected)
399                 return 1;
400         if (atomic_read(&kgdb_setting_breakpoint))
401                 return 1;
402         if (print_wait) {
403 #ifdef CONFIG_KGDB_KDB
404                 if (!dbg_kdb_mode)
405                         printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
406 #else
407                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
408 #endif
409         }
410         return 1;
411 }
412
413 static int kgdb_reenter_check(struct kgdb_state *ks)
414 {
415         unsigned long addr;
416
417         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
418                 return 0;
419
420         /* Panic on recursive debugger calls: */
421         exception_level++;
422         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
423         dbg_deactivate_sw_breakpoints();
424
425         /*
426          * If the break point removed ok at the place exception
427          * occurred, try to recover and print a warning to the end
428          * user because the user planted a breakpoint in a place that
429          * KGDB needs in order to function.
430          */
431         if (dbg_remove_sw_break(addr) == 0) {
432                 exception_level = 0;
433                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
434                 dbg_activate_sw_breakpoints();
435                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
436                         addr);
437                 WARN_ON_ONCE(1);
438
439                 return 1;
440         }
441         dbg_remove_all_break();
442         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
443
444         if (exception_level > 1) {
445                 dump_stack();
446                 panic("Recursive entry to debugger");
447         }
448
449         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
450 #ifdef CONFIG_KGDB_KDB
451         /* Allow kdb to debug itself one level */
452         return 0;
453 #endif
454         dump_stack();
455         panic("Recursive entry to debugger");
456
457         return 1;
458 }
459
460 static void dbg_cpu_switch(int cpu, int next_cpu)
461 {
462         /* Mark the cpu we are switching away from as a slave when it
463          * holds the kgdb_active token.  This must be done so that the
464          * that all the cpus wait in for the debug core will not enter
465          * again as the master. */
466         if (cpu == atomic_read(&kgdb_active)) {
467                 kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
468                 kgdb_info[cpu].exception_state &= ~DCPU_WANT_MASTER;
469         }
470         kgdb_info[next_cpu].exception_state |= DCPU_NEXT_MASTER;
471 }
472
473 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
474 {
475         unsigned long flags;
476         int sstep_tries = 100;
477         int error;
478         int i, cpu;
479         int trace_on = 0;
480 acquirelock:
481         /*
482          * Interrupts will be restored by the 'trap return' code, except when
483          * single stepping.
484          */
485         local_irq_save(flags);
486
487         cpu = ks->cpu;
488         kgdb_info[cpu].debuggerinfo = regs;
489         kgdb_info[cpu].task = current;
490         kgdb_info[cpu].ret_state = 0;
491         kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
492         /*
493          * Make sure the above info reaches the primary CPU before
494          * our cpu_in_kgdb[] flag setting does:
495          */
496         atomic_inc(&cpu_in_kgdb[cpu]);
497
498         if (exception_level == 1)
499                 goto cpu_master_loop;
500
501         /*
502          * CPU will loop if it is a slave or request to become a kgdb
503          * master cpu and acquire the kgdb_active lock:
504          */
505         while (1) {
506 cpu_loop:
507                 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
508                         kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
509                         goto cpu_master_loop;
510                 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
511                         if (atomic_cmpxchg(&kgdb_active, -1, cpu) == cpu)
512                                 break;
513                 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
514                         if (!atomic_read(&passive_cpu_wait[cpu]))
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                         atomic_dec(&cpu_in_kgdb[cpu]);
526                         touch_softlockup_watchdog_sync();
527                         clocksource_touch_watchdog();
528                         local_irq_restore(flags);
529                         return 0;
530                 }
531                 cpu_relax();
532         }
533
534         /*
535          * For single stepping, try to only enter on the processor
536          * that was single stepping.  To gaurd against a deadlock, the
537          * kernel will only try for the value of sstep_tries before
538          * giving up and continuing on.
539          */
540         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
541             (kgdb_info[cpu].task &&
542              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
543                 atomic_set(&kgdb_active, -1);
544                 touch_softlockup_watchdog_sync();
545                 clocksource_touch_watchdog();
546                 local_irq_restore(flags);
547
548                 goto acquirelock;
549         }
550
551         if (!kgdb_io_ready(1)) {
552                 kgdb_info[cpu].ret_state = 1;
553                 goto kgdb_restore; /* No I/O connection, resume the system */
554         }
555
556         /*
557          * Don't enter if we have hit a removed breakpoint.
558          */
559         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
560                 goto kgdb_restore;
561
562         /* Call the I/O driver's pre_exception routine */
563         if (dbg_io_ops->pre_exception)
564                 dbg_io_ops->pre_exception();
565
566         kgdb_disable_hw_debug(ks->linux_regs);
567
568         /*
569          * Get the passive CPU lock which will hold all the non-primary
570          * CPU in a spin state while the debugger is active
571          */
572         if (!kgdb_single_step) {
573                 for (i = 0; i < NR_CPUS; i++)
574                         atomic_inc(&passive_cpu_wait[i]);
575         }
576
577 #ifdef CONFIG_SMP
578         /* Signal the other CPUs to enter kgdb_wait() */
579         if ((!kgdb_single_step) && kgdb_do_roundup)
580                 kgdb_roundup_cpus(flags);
581 #endif
582
583         /*
584          * Wait for the other CPUs to be notified and be waiting for us:
585          */
586         for_each_online_cpu(i) {
587                 while (kgdb_do_roundup && !atomic_read(&cpu_in_kgdb[i]))
588                         cpu_relax();
589         }
590
591         /*
592          * At this point the primary processor is completely
593          * in the debugger and all secondary CPUs are quiescent
594          */
595         dbg_deactivate_sw_breakpoints();
596         kgdb_single_step = 0;
597         kgdb_contthread = current;
598         exception_level = 0;
599         trace_on = tracing_is_on();
600         if (trace_on)
601                 tracing_off();
602
603         while (1) {
604 cpu_master_loop:
605                 if (dbg_kdb_mode) {
606                         kgdb_connected = 1;
607                         error = kdb_stub(ks);
608                         if (error == -1)
609                                 continue;
610                         kgdb_connected = 0;
611                 } else {
612                         error = gdb_serial_stub(ks);
613                 }
614
615                 if (error == DBG_PASS_EVENT) {
616                         dbg_kdb_mode = !dbg_kdb_mode;
617                 } else if (error == DBG_SWITCH_CPU_EVENT) {
618                         dbg_cpu_switch(cpu, dbg_switch_cpu);
619                         goto cpu_loop;
620                 } else {
621                         kgdb_info[cpu].ret_state = error;
622                         break;
623                 }
624         }
625
626         /* Call the I/O driver's post_exception routine */
627         if (dbg_io_ops->post_exception)
628                 dbg_io_ops->post_exception();
629
630         atomic_dec(&cpu_in_kgdb[ks->cpu]);
631
632         if (!kgdb_single_step) {
633                 for (i = NR_CPUS-1; i >= 0; i--)
634                         atomic_dec(&passive_cpu_wait[i]);
635                 /*
636                  * Wait till all the CPUs have quit from the debugger,
637                  * but allow a CPU that hit an exception and is
638                  * waiting to become the master to remain in the debug
639                  * core.
640                  */
641                 for_each_online_cpu(i) {
642                         while (kgdb_do_roundup &&
643                                atomic_read(&cpu_in_kgdb[i]) &&
644                                !(kgdb_info[i].exception_state &
645                                  DCPU_WANT_MASTER))
646                                 cpu_relax();
647                 }
648         }
649
650 kgdb_restore:
651         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
652                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
653                 if (kgdb_info[sstep_cpu].task)
654                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
655                 else
656                         kgdb_sstep_pid = 0;
657         }
658         if (trace_on)
659                 tracing_on();
660         /* Free kgdb_active */
661         atomic_set(&kgdb_active, -1);
662         touch_softlockup_watchdog_sync();
663         clocksource_touch_watchdog();
664         local_irq_restore(flags);
665
666         return kgdb_info[cpu].ret_state;
667 }
668
669 /*
670  * kgdb_handle_exception() - main entry point from a kernel exception
671  *
672  * Locking hierarchy:
673  *      interface locks, if any (begin_session)
674  *      kgdb lock (kgdb_active)
675  */
676 int
677 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
678 {
679         struct kgdb_state kgdb_var;
680         struct kgdb_state *ks = &kgdb_var;
681         int ret;
682
683         ks->cpu                 = raw_smp_processor_id();
684         ks->ex_vector           = evector;
685         ks->signo               = signo;
686         ks->err_code            = ecode;
687         ks->kgdb_usethreadid    = 0;
688         ks->linux_regs          = regs;
689
690         if (kgdb_reenter_check(ks))
691                 return 0; /* Ouch, double exception ! */
692         kgdb_info[ks->cpu].exception_state |= DCPU_WANT_MASTER;
693         ret = kgdb_cpu_enter(ks, regs);
694         kgdb_info[ks->cpu].exception_state &= ~(DCPU_WANT_MASTER |
695                                                 DCPU_IS_SLAVE);
696         return ret;
697 }
698
699 int kgdb_nmicallback(int cpu, void *regs)
700 {
701 #ifdef CONFIG_SMP
702         struct kgdb_state kgdb_var;
703         struct kgdb_state *ks = &kgdb_var;
704
705         memset(ks, 0, sizeof(struct kgdb_state));
706         ks->cpu                 = cpu;
707         ks->linux_regs          = regs;
708
709         if (!atomic_read(&cpu_in_kgdb[cpu]) &&
710             atomic_read(&kgdb_active) != -1 &&
711             atomic_read(&kgdb_active) != cpu) {
712                 kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
713                 kgdb_cpu_enter(ks, regs);
714                 kgdb_info[cpu].exception_state &= ~DCPU_IS_SLAVE;
715                 return 0;
716         }
717 #endif
718         return 1;
719 }
720
721 static void kgdb_console_write(struct console *co, const char *s,
722    unsigned count)
723 {
724         unsigned long flags;
725
726         /* If we're debugging, or KGDB has not connected, don't try
727          * and print. */
728         if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
729                 return;
730
731         local_irq_save(flags);
732         gdbstub_msg_write(s, count);
733         local_irq_restore(flags);
734 }
735
736 static struct console kgdbcons = {
737         .name           = "kgdb",
738         .write          = kgdb_console_write,
739         .flags          = CON_PRINTBUFFER | CON_ENABLED,
740         .index          = -1,
741 };
742
743 #ifdef CONFIG_MAGIC_SYSRQ
744 static void sysrq_handle_dbg(int key, struct tty_struct *tty)
745 {
746         if (!dbg_io_ops) {
747                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
748                 return;
749         }
750         if (!kgdb_connected) {
751 #ifdef CONFIG_KGDB_KDB
752                 if (!dbg_kdb_mode)
753                         printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
754 #else
755                 printk(KERN_CRIT "Entering KGDB\n");
756 #endif
757         }
758
759         kgdb_breakpoint();
760 }
761
762 static struct sysrq_key_op sysrq_dbg_op = {
763         .handler        = sysrq_handle_dbg,
764         .help_msg       = "debug(G)",
765         .action_msg     = "DEBUG",
766 };
767 #endif
768
769 static int kgdb_panic_event(struct notifier_block *self,
770                             unsigned long val,
771                             void *data)
772 {
773         if (dbg_kdb_mode)
774                 kdb_printf("PANIC: %s\n", (char *)data);
775         kgdb_breakpoint();
776         return NOTIFY_DONE;
777 }
778
779 static struct notifier_block kgdb_panic_event_nb = {
780        .notifier_call   = kgdb_panic_event,
781        .priority        = INT_MAX,
782 };
783
784 void __weak kgdb_arch_late(void)
785 {
786 }
787
788 void __init dbg_late_init(void)
789 {
790         dbg_is_early = false;
791         if (kgdb_io_module_registered)
792                 kgdb_arch_late();
793         kdb_init(KDB_INIT_FULL);
794 }
795
796 static void kgdb_register_callbacks(void)
797 {
798         if (!kgdb_io_module_registered) {
799                 kgdb_io_module_registered = 1;
800                 kgdb_arch_init();
801                 if (!dbg_is_early)
802                         kgdb_arch_late();
803                 atomic_notifier_chain_register(&panic_notifier_list,
804                                                &kgdb_panic_event_nb);
805 #ifdef CONFIG_MAGIC_SYSRQ
806                 register_sysrq_key('g', &sysrq_dbg_op);
807 #endif
808                 if (kgdb_use_con && !kgdb_con_registered) {
809                         register_console(&kgdbcons);
810                         kgdb_con_registered = 1;
811                 }
812         }
813 }
814
815 static void kgdb_unregister_callbacks(void)
816 {
817         /*
818          * When this routine is called KGDB should unregister from the
819          * panic handler and clean up, making sure it is not handling any
820          * break exceptions at the time.
821          */
822         if (kgdb_io_module_registered) {
823                 kgdb_io_module_registered = 0;
824                 atomic_notifier_chain_unregister(&panic_notifier_list,
825                                                &kgdb_panic_event_nb);
826                 kgdb_arch_exit();
827 #ifdef CONFIG_MAGIC_SYSRQ
828                 unregister_sysrq_key('g', &sysrq_dbg_op);
829 #endif
830                 if (kgdb_con_registered) {
831                         unregister_console(&kgdbcons);
832                         kgdb_con_registered = 0;
833                 }
834         }
835 }
836
837 /*
838  * There are times a tasklet needs to be used vs a compiled in
839  * break point so as to cause an exception outside a kgdb I/O module,
840  * such as is the case with kgdboe, where calling a breakpoint in the
841  * I/O driver itself would be fatal.
842  */
843 static void kgdb_tasklet_bpt(unsigned long ing)
844 {
845         kgdb_breakpoint();
846         atomic_set(&kgdb_break_tasklet_var, 0);
847 }
848
849 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
850
851 void kgdb_schedule_breakpoint(void)
852 {
853         if (atomic_read(&kgdb_break_tasklet_var) ||
854                 atomic_read(&kgdb_active) != -1 ||
855                 atomic_read(&kgdb_setting_breakpoint))
856                 return;
857         atomic_inc(&kgdb_break_tasklet_var);
858         tasklet_schedule(&kgdb_tasklet_breakpoint);
859 }
860 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
861
862 static void kgdb_initial_breakpoint(void)
863 {
864         kgdb_break_asap = 0;
865
866         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
867         kgdb_breakpoint();
868 }
869
870 /**
871  *      kgdb_register_io_module - register KGDB IO module
872  *      @new_dbg_io_ops: the io ops vector
873  *
874  *      Register it with the KGDB core.
875  */
876 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
877 {
878         int err;
879
880         spin_lock(&kgdb_registration_lock);
881
882         if (dbg_io_ops) {
883                 spin_unlock(&kgdb_registration_lock);
884
885                 printk(KERN_ERR "kgdb: Another I/O driver is already "
886                                 "registered with KGDB.\n");
887                 return -EBUSY;
888         }
889
890         if (new_dbg_io_ops->init) {
891                 err = new_dbg_io_ops->init();
892                 if (err) {
893                         spin_unlock(&kgdb_registration_lock);
894                         return err;
895                 }
896         }
897
898         dbg_io_ops = new_dbg_io_ops;
899
900         spin_unlock(&kgdb_registration_lock);
901
902         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
903                new_dbg_io_ops->name);
904
905         /* Arm KGDB now. */
906         kgdb_register_callbacks();
907
908         if (kgdb_break_asap)
909                 kgdb_initial_breakpoint();
910
911         return 0;
912 }
913 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
914
915 /**
916  *      kkgdb_unregister_io_module - unregister KGDB IO module
917  *      @old_dbg_io_ops: the io ops vector
918  *
919  *      Unregister it with the KGDB core.
920  */
921 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
922 {
923         BUG_ON(kgdb_connected);
924
925         /*
926          * KGDB is no longer able to communicate out, so
927          * unregister our callbacks and reset state.
928          */
929         kgdb_unregister_callbacks();
930
931         spin_lock(&kgdb_registration_lock);
932
933         WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
934         dbg_io_ops = NULL;
935
936         spin_unlock(&kgdb_registration_lock);
937
938         printk(KERN_INFO
939                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
940                 old_dbg_io_ops->name);
941 }
942 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
943
944 int dbg_io_get_char(void)
945 {
946         int ret = dbg_io_ops->read_char();
947         if (ret == NO_POLL_CHAR)
948                 return -1;
949         if (!dbg_kdb_mode)
950                 return ret;
951         if (ret == 127)
952                 return 8;
953         return ret;
954 }
955
956 /**
957  * kgdb_breakpoint - generate breakpoint exception
958  *
959  * This function will generate a breakpoint exception.  It is used at the
960  * beginning of a program to sync up with a debugger and can be used
961  * otherwise as a quick means to stop program execution and "break" into
962  * the debugger.
963  */
964 void kgdb_breakpoint(void)
965 {
966         atomic_inc(&kgdb_setting_breakpoint);
967         wmb(); /* Sync point before breakpoint */
968         arch_kgdb_breakpoint();
969         wmb(); /* Sync point after breakpoint */
970         atomic_dec(&kgdb_setting_breakpoint);
971 }
972 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
973
974 static int __init opt_kgdb_wait(char *str)
975 {
976         kgdb_break_asap = 1;
977
978         kdb_init(KDB_INIT_EARLY);
979         if (kgdb_io_module_registered)
980                 kgdb_initial_breakpoint();
981
982         return 0;
983 }
984
985 early_param("kgdbwait", opt_kgdb_wait);