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TOMOYO Linux Cross Reference
Linux/kernel/debug/debug_core.c

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  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/serial_core.h>
 33 #include <linux/interrupt.h>
 34 #include <linux/spinlock.h>
 35 #include <linux/console.h>
 36 #include <linux/threads.h>
 37 #include <linux/uaccess.h>
 38 #include <linux/kernel.h>
 39 #include <linux/module.h>
 40 #include <linux/ptrace.h>
 41 #include <linux/string.h>
 42 #include <linux/delay.h>
 43 #include <linux/sched.h>
 44 #include <linux/sysrq.h>
 45 #include <linux/reboot.h>
 46 #include <linux/init.h>
 47 #include <linux/kgdb.h>
 48 #include <linux/kdb.h>
 49 #include <linux/pid.h>
 50 #include <linux/smp.h>
 51 #include <linux/mm.h>
 52 #include <linux/rcupdate.h>
 53 
 54 #include <asm/cacheflush.h>
 55 #include <asm/byteorder.h>
 56 #include <linux/atomic.h>
 57 
 58 #include "debug_core.h"
 59 
 60 static int kgdb_break_asap;
 61 
 62 struct debuggerinfo_struct kgdb_info[NR_CPUS];
 63 
 64 /**
 65  * kgdb_connected - Is a host GDB connected to us?
 66  */
 67 int                             kgdb_connected;
 68 EXPORT_SYMBOL_GPL(kgdb_connected);
 69 
 70 /* All the KGDB handlers are installed */
 71 int                     kgdb_io_module_registered;
 72 
 73 /* Guard for recursive entry */
 74 static int                      exception_level;
 75 
 76 struct kgdb_io          *dbg_io_ops;
 77 static DEFINE_SPINLOCK(kgdb_registration_lock);
 78 
 79 /* Action for the reboot notifiter, a global allow kdb to change it */
 80 static int kgdbreboot;
 81 /* kgdb console driver is loaded */
 82 static int kgdb_con_registered;
 83 /* determine if kgdb console output should be used */
 84 static int kgdb_use_con;
 85 /* Flag for alternate operations for early debugging */
 86 bool dbg_is_early = true;
 87 /* Next cpu to become the master debug core */
 88 int dbg_switch_cpu;
 89 
 90 /* Use kdb or gdbserver mode */
 91 int dbg_kdb_mode = 1;
 92 
 93 static int __init opt_kgdb_con(char *str)
 94 {
 95         kgdb_use_con = 1;
 96         return 0;
 97 }
 98 
 99 early_param("kgdbcon", opt_kgdb_con);
100 
101 module_param(kgdb_use_con, int, 0644);
102 module_param(kgdbreboot, int, 0644);
103 
104 /*
105  * Holds information about breakpoints in a kernel. These breakpoints are
106  * added and removed by gdb.
107  */
108 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
109         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
110 };
111 
112 /*
113  * The CPU# of the active CPU, or -1 if none:
114  */
115 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
116 EXPORT_SYMBOL_GPL(kgdb_active);
117 static DEFINE_RAW_SPINLOCK(dbg_master_lock);
118 static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
119 
120 /*
121  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
122  * bootup code (which might not have percpu set up yet):
123  */
124 static atomic_t                 masters_in_kgdb;
125 static atomic_t                 slaves_in_kgdb;
126 static atomic_t                 kgdb_break_tasklet_var;
127 atomic_t                        kgdb_setting_breakpoint;
128 
129 struct task_struct              *kgdb_usethread;
130 struct task_struct              *kgdb_contthread;
131 
132 int                             kgdb_single_step;
133 static pid_t                    kgdb_sstep_pid;
134 
135 /* to keep track of the CPU which is doing the single stepping*/
136 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
137 
138 /*
139  * If you are debugging a problem where roundup (the collection of
140  * all other CPUs) is a problem [this should be extremely rare],
141  * then use the nokgdbroundup option to avoid roundup. In that case
142  * the other CPUs might interfere with your debugging context, so
143  * use this with care:
144  */
145 static int kgdb_do_roundup = 1;
146 
147 static int __init opt_nokgdbroundup(char *str)
148 {
149         kgdb_do_roundup = 0;
150 
151         return 0;
152 }
153 
154 early_param("nokgdbroundup", opt_nokgdbroundup);
155 
156 /*
157  * Finally, some KGDB code :-)
158  */
159 
160 /*
161  * Weak aliases for breakpoint management,
162  * can be overriden by architectures when needed:
163  */
164 int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
165 {
166         int err;
167 
168         err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
169                                 BREAK_INSTR_SIZE);
170         if (err)
171                 return err;
172         err = probe_kernel_write((char *)bpt->bpt_addr,
173                                  arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
174         return err;
175 }
176 
177 int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
178 {
179         return probe_kernel_write((char *)bpt->bpt_addr,
180                                   (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
181 }
182 
183 int __weak kgdb_validate_break_address(unsigned long addr)
184 {
185         struct kgdb_bkpt tmp;
186         int err;
187         /* Validate setting the breakpoint and then removing it.  If the
188          * remove fails, the kernel needs to emit a bad message because we
189          * are deep trouble not being able to put things back the way we
190          * found them.
191          */
192         tmp.bpt_addr = addr;
193         err = kgdb_arch_set_breakpoint(&tmp);
194         if (err)
195                 return err;
196         err = kgdb_arch_remove_breakpoint(&tmp);
197         if (err)
198                 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
199                    "memory destroyed at: %lx", addr);
200         return err;
201 }
202 
203 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
204 {
205         return instruction_pointer(regs);
206 }
207 
208 int __weak kgdb_arch_init(void)
209 {
210         return 0;
211 }
212 
213 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
214 {
215         return 0;
216 }
217 
218 /*
219  * Some architectures need cache flushes when we set/clear a
220  * breakpoint:
221  */
222 static void kgdb_flush_swbreak_addr(unsigned long addr)
223 {
224         if (!CACHE_FLUSH_IS_SAFE)
225                 return;
226 
227         if (current->mm && current->mm->mmap_cache) {
228                 flush_cache_range(current->mm->mmap_cache,
229                                   addr, addr + BREAK_INSTR_SIZE);
230         }
231         /* Force flush instruction cache if it was outside the mm */
232         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
233 }
234 
235 /*
236  * SW breakpoint management:
237  */
238 int dbg_activate_sw_breakpoints(void)
239 {
240         int error;
241         int ret = 0;
242         int i;
243 
244         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
245                 if (kgdb_break[i].state != BP_SET)
246                         continue;
247 
248                 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
249                 if (error) {
250                         ret = error;
251                         printk(KERN_INFO "KGDB: BP install failed: %lx",
252                                kgdb_break[i].bpt_addr);
253                         continue;
254                 }
255 
256                 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
257                 kgdb_break[i].state = BP_ACTIVE;
258         }
259         return ret;
260 }
261 
262 int dbg_set_sw_break(unsigned long addr)
263 {
264         int err = kgdb_validate_break_address(addr);
265         int breakno = -1;
266         int i;
267 
268         if (err)
269                 return err;
270 
271         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
272                 if ((kgdb_break[i].state == BP_SET) &&
273                                         (kgdb_break[i].bpt_addr == addr))
274                         return -EEXIST;
275         }
276         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
277                 if (kgdb_break[i].state == BP_REMOVED &&
278                                         kgdb_break[i].bpt_addr == addr) {
279                         breakno = i;
280                         break;
281                 }
282         }
283 
284         if (breakno == -1) {
285                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
286                         if (kgdb_break[i].state == BP_UNDEFINED) {
287                                 breakno = i;
288                                 break;
289                         }
290                 }
291         }
292 
293         if (breakno == -1)
294                 return -E2BIG;
295 
296         kgdb_break[breakno].state = BP_SET;
297         kgdb_break[breakno].type = BP_BREAKPOINT;
298         kgdb_break[breakno].bpt_addr = addr;
299 
300         return 0;
301 }
302 
303 int dbg_deactivate_sw_breakpoints(void)
304 {
305         int error;
306         int ret = 0;
307         int i;
308 
309         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
310                 if (kgdb_break[i].state != BP_ACTIVE)
311                         continue;
312                 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
313                 if (error) {
314                         printk(KERN_INFO "KGDB: BP remove failed: %lx\n",
315                                kgdb_break[i].bpt_addr);
316                         ret = error;
317                 }
318 
319                 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
320                 kgdb_break[i].state = BP_SET;
321         }
322         return ret;
323 }
324 
325 int dbg_remove_sw_break(unsigned long addr)
326 {
327         int i;
328 
329         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
330                 if ((kgdb_break[i].state == BP_SET) &&
331                                 (kgdb_break[i].bpt_addr == addr)) {
332                         kgdb_break[i].state = BP_REMOVED;
333                         return 0;
334                 }
335         }
336         return -ENOENT;
337 }
338 
339 int kgdb_isremovedbreak(unsigned long addr)
340 {
341         int i;
342 
343         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
344                 if ((kgdb_break[i].state == BP_REMOVED) &&
345                                         (kgdb_break[i].bpt_addr == addr))
346                         return 1;
347         }
348         return 0;
349 }
350 
351 int dbg_remove_all_break(void)
352 {
353         int error;
354         int i;
355 
356         /* Clear memory breakpoints. */
357         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
358                 if (kgdb_break[i].state != BP_ACTIVE)
359                         goto setundefined;
360                 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
361                 if (error)
362                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
363                                kgdb_break[i].bpt_addr);
364 setundefined:
365                 kgdb_break[i].state = BP_UNDEFINED;
366         }
367 
368         /* Clear hardware breakpoints. */
369         if (arch_kgdb_ops.remove_all_hw_break)
370                 arch_kgdb_ops.remove_all_hw_break();
371 
372         return 0;
373 }
374 
375 /*
376  * Return true if there is a valid kgdb I/O module.  Also if no
377  * debugger is attached a message can be printed to the console about
378  * waiting for the debugger to attach.
379  *
380  * The print_wait argument is only to be true when called from inside
381  * the core kgdb_handle_exception, because it will wait for the
382  * debugger to attach.
383  */
384 static int kgdb_io_ready(int print_wait)
385 {
386         if (!dbg_io_ops)
387                 return 0;
388         if (kgdb_connected)
389                 return 1;
390         if (atomic_read(&kgdb_setting_breakpoint))
391                 return 1;
392         if (print_wait) {
393 #ifdef CONFIG_KGDB_KDB
394                 if (!dbg_kdb_mode)
395                         printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
396 #else
397                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
398 #endif
399         }
400         return 1;
401 }
402 
403 static int kgdb_reenter_check(struct kgdb_state *ks)
404 {
405         unsigned long addr;
406 
407         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
408                 return 0;
409 
410         /* Panic on recursive debugger calls: */
411         exception_level++;
412         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
413         dbg_deactivate_sw_breakpoints();
414 
415         /*
416          * If the break point removed ok at the place exception
417          * occurred, try to recover and print a warning to the end
418          * user because the user planted a breakpoint in a place that
419          * KGDB needs in order to function.
420          */
421         if (dbg_remove_sw_break(addr) == 0) {
422                 exception_level = 0;
423                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
424                 dbg_activate_sw_breakpoints();
425                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
426                         addr);
427                 WARN_ON_ONCE(1);
428 
429                 return 1;
430         }
431         dbg_remove_all_break();
432         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
433 
434         if (exception_level > 1) {
435                 dump_stack();
436                 panic("Recursive entry to debugger");
437         }
438 
439         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
440 #ifdef CONFIG_KGDB_KDB
441         /* Allow kdb to debug itself one level */
442         return 0;
443 #endif
444         dump_stack();
445         panic("Recursive entry to debugger");
446 
447         return 1;
448 }
449 
450 static void dbg_touch_watchdogs(void)
451 {
452         touch_softlockup_watchdog_sync();
453         clocksource_touch_watchdog();
454         rcu_cpu_stall_reset();
455 }
456 
457 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
458                 int exception_state)
459 {
460         unsigned long flags;
461         int sstep_tries = 100;
462         int error;
463         int cpu;
464         int trace_on = 0;
465         int online_cpus = num_online_cpus();
466 
467         kgdb_info[ks->cpu].enter_kgdb++;
468         kgdb_info[ks->cpu].exception_state |= exception_state;
469 
470         if (exception_state == DCPU_WANT_MASTER)
471                 atomic_inc(&masters_in_kgdb);
472         else
473                 atomic_inc(&slaves_in_kgdb);
474 
475         if (arch_kgdb_ops.disable_hw_break)
476                 arch_kgdb_ops.disable_hw_break(regs);
477 
478 acquirelock:
479         /*
480          * Interrupts will be restored by the 'trap return' code, except when
481          * single stepping.
482          */
483         local_irq_save(flags);
484 
485         cpu = ks->cpu;
486         kgdb_info[cpu].debuggerinfo = regs;
487         kgdb_info[cpu].task = current;
488         kgdb_info[cpu].ret_state = 0;
489         kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
490 
491         /* Make sure the above info reaches the primary CPU */
492         smp_mb();
493 
494         if (exception_level == 1) {
495                 if (raw_spin_trylock(&dbg_master_lock))
496                         atomic_xchg(&kgdb_active, cpu);
497                 goto cpu_master_loop;
498         }
499 
500         /*
501          * CPU will loop if it is a slave or request to become a kgdb
502          * master cpu and acquire the kgdb_active lock:
503          */
504         while (1) {
505 cpu_loop:
506                 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
507                         kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
508                         goto cpu_master_loop;
509                 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
510                         if (raw_spin_trylock(&dbg_master_lock)) {
511                                 atomic_xchg(&kgdb_active, cpu);
512                                 break;
513                         }
514                 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
515                         if (!raw_spin_is_locked(&dbg_slave_lock))
516                                 goto return_normal;
517                 } else {
518 return_normal:
519                         /* Return to normal operation by executing any
520                          * hw breakpoint fixup.
521                          */
522                         if (arch_kgdb_ops.correct_hw_break)
523                                 arch_kgdb_ops.correct_hw_break();
524                         if (trace_on)
525                                 tracing_on();
526                         kgdb_info[cpu].exception_state &=
527                                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
528                         kgdb_info[cpu].enter_kgdb--;
529                         smp_mb__before_atomic_dec();
530                         atomic_dec(&slaves_in_kgdb);
531                         dbg_touch_watchdogs();
532                         local_irq_restore(flags);
533                         return 0;
534                 }
535                 cpu_relax();
536         }
537 
538         /*
539          * For single stepping, try to only enter on the processor
540          * that was single stepping.  To guard against a deadlock, the
541          * kernel will only try for the value of sstep_tries before
542          * giving up and continuing on.
543          */
544         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
545             (kgdb_info[cpu].task &&
546              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
547                 atomic_set(&kgdb_active, -1);
548                 raw_spin_unlock(&dbg_master_lock);
549                 dbg_touch_watchdogs();
550                 local_irq_restore(flags);
551 
552                 goto acquirelock;
553         }
554 
555         if (!kgdb_io_ready(1)) {
556                 kgdb_info[cpu].ret_state = 1;
557                 goto kgdb_restore; /* No I/O connection, resume the system */
558         }
559 
560         /*
561          * Don't enter if we have hit a removed breakpoint.
562          */
563         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
564                 goto kgdb_restore;
565 
566         /* Call the I/O driver's pre_exception routine */
567         if (dbg_io_ops->pre_exception)
568                 dbg_io_ops->pre_exception();
569 
570         /*
571          * Get the passive CPU lock which will hold all the non-primary
572          * CPU in a spin state while the debugger is active
573          */
574         if (!kgdb_single_step)
575                 raw_spin_lock(&dbg_slave_lock);
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         while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) +
587                                 atomic_read(&slaves_in_kgdb)) != online_cpus)
588                 cpu_relax();
589 
590         /*
591          * At this point the primary processor is completely
592          * in the debugger and all secondary CPUs are quiescent
593          */
594         dbg_deactivate_sw_breakpoints();
595         kgdb_single_step = 0;
596         kgdb_contthread = current;
597         exception_level = 0;
598         trace_on = tracing_is_on();
599         if (trace_on)
600                 tracing_off();
601 
602         while (1) {
603 cpu_master_loop:
604                 if (dbg_kdb_mode) {
605                         kgdb_connected = 1;
606                         error = kdb_stub(ks);
607                         if (error == -1)
608                                 continue;
609                         kgdb_connected = 0;
610                 } else {
611                         error = gdb_serial_stub(ks);
612                 }
613 
614                 if (error == DBG_PASS_EVENT) {
615                         dbg_kdb_mode = !dbg_kdb_mode;
616                 } else if (error == DBG_SWITCH_CPU_EVENT) {
617                         kgdb_info[dbg_switch_cpu].exception_state |=
618                                 DCPU_NEXT_MASTER;
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         if (!kgdb_single_step) {
631                 raw_spin_unlock(&dbg_slave_lock);
632                 /* Wait till all the CPUs have quit from the debugger. */
633                 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
634                         cpu_relax();
635         }
636 
637 kgdb_restore:
638         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
639                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
640                 if (kgdb_info[sstep_cpu].task)
641                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
642                 else
643                         kgdb_sstep_pid = 0;
644         }
645         if (arch_kgdb_ops.correct_hw_break)
646                 arch_kgdb_ops.correct_hw_break();
647         if (trace_on)
648                 tracing_on();
649 
650         kgdb_info[cpu].exception_state &=
651                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
652         kgdb_info[cpu].enter_kgdb--;
653         smp_mb__before_atomic_dec();
654         atomic_dec(&masters_in_kgdb);
655         /* Free kgdb_active */
656         atomic_set(&kgdb_active, -1);
657         raw_spin_unlock(&dbg_master_lock);
658         dbg_touch_watchdogs();
659         local_irq_restore(flags);
660 
661         return kgdb_info[cpu].ret_state;
662 }
663 
664 /*
665  * kgdb_handle_exception() - main entry point from a kernel exception
666  *
667  * Locking hierarchy:
668  *      interface locks, if any (begin_session)
669  *      kgdb lock (kgdb_active)
670  */
671 int
672 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
673 {
674         struct kgdb_state kgdb_var;
675         struct kgdb_state *ks = &kgdb_var;
676         int ret = 0;
677 
678         if (arch_kgdb_ops.enable_nmi)
679                 arch_kgdb_ops.enable_nmi(0);
680 
681         ks->cpu                 = raw_smp_processor_id();
682         ks->ex_vector           = evector;
683         ks->signo               = signo;
684         ks->err_code            = ecode;
685         ks->kgdb_usethreadid    = 0;
686         ks->linux_regs          = regs;
687 
688         if (kgdb_reenter_check(ks))
689                 goto out; /* Ouch, double exception ! */
690         if (kgdb_info[ks->cpu].enter_kgdb != 0)
691                 goto out;
692 
693         ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
694 out:
695         if (arch_kgdb_ops.enable_nmi)
696                 arch_kgdb_ops.enable_nmi(1);
697         return ret;
698 }
699 
700 /*
701  * GDB places a breakpoint at this function to know dynamically
702  * loaded objects. It's not defined static so that only one instance with this
703  * name exists in the kernel.
704  */
705 
706 static int module_event(struct notifier_block *self, unsigned long val,
707         void *data)
708 {
709         return 0;
710 }
711 
712 static struct notifier_block dbg_module_load_nb = {
713         .notifier_call  = module_event,
714 };
715 
716 int kgdb_nmicallback(int cpu, void *regs)
717 {
718 #ifdef CONFIG_SMP
719         struct kgdb_state kgdb_var;
720         struct kgdb_state *ks = &kgdb_var;
721 
722         memset(ks, 0, sizeof(struct kgdb_state));
723         ks->cpu                 = cpu;
724         ks->linux_regs          = regs;
725 
726         if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
727                         raw_spin_is_locked(&dbg_master_lock)) {
728                 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
729                 return 0;
730         }
731 #endif
732         return 1;
733 }
734 
735 static void kgdb_console_write(struct console *co, const char *s,
736    unsigned count)
737 {
738         unsigned long flags;
739 
740         /* If we're debugging, or KGDB has not connected, don't try
741          * and print. */
742         if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
743                 return;
744 
745         local_irq_save(flags);
746         gdbstub_msg_write(s, count);
747         local_irq_restore(flags);
748 }
749 
750 static struct console kgdbcons = {
751         .name           = "kgdb",
752         .write          = kgdb_console_write,
753         .flags          = CON_PRINTBUFFER | CON_ENABLED,
754         .index          = -1,
755 };
756 
757 #ifdef CONFIG_MAGIC_SYSRQ
758 static void sysrq_handle_dbg(int key)
759 {
760         if (!dbg_io_ops) {
761                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
762                 return;
763         }
764         if (!kgdb_connected) {
765 #ifdef CONFIG_KGDB_KDB
766                 if (!dbg_kdb_mode)
767                         printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
768 #else
769                 printk(KERN_CRIT "Entering KGDB\n");
770 #endif
771         }
772 
773         kgdb_breakpoint();
774 }
775 
776 static struct sysrq_key_op sysrq_dbg_op = {
777         .handler        = sysrq_handle_dbg,
778         .help_msg       = "debug(g)",
779         .action_msg     = "DEBUG",
780 };
781 #endif
782 
783 static int kgdb_panic_event(struct notifier_block *self,
784                             unsigned long val,
785                             void *data)
786 {
787         if (dbg_kdb_mode)
788                 kdb_printf("PANIC: %s\n", (char *)data);
789         kgdb_breakpoint();
790         return NOTIFY_DONE;
791 }
792 
793 static struct notifier_block kgdb_panic_event_nb = {
794        .notifier_call   = kgdb_panic_event,
795        .priority        = INT_MAX,
796 };
797 
798 void __weak kgdb_arch_late(void)
799 {
800 }
801 
802 void __init dbg_late_init(void)
803 {
804         dbg_is_early = false;
805         if (kgdb_io_module_registered)
806                 kgdb_arch_late();
807         kdb_init(KDB_INIT_FULL);
808 }
809 
810 static int
811 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
812 {
813         /*
814          * Take the following action on reboot notify depending on value:
815          *    1 == Enter debugger
816          *    0 == [the default] detatch debug client
817          *   -1 == Do nothing... and use this until the board resets
818          */
819         switch (kgdbreboot) {
820         case 1:
821                 kgdb_breakpoint();
822         case -1:
823                 goto done;
824         }
825         if (!dbg_kdb_mode)
826                 gdbstub_exit(code);
827 done:
828         return NOTIFY_DONE;
829 }
830 
831 static struct notifier_block dbg_reboot_notifier = {
832         .notifier_call          = dbg_notify_reboot,
833         .next                   = NULL,
834         .priority               = INT_MAX,
835 };
836 
837 static void kgdb_register_callbacks(void)
838 {
839         if (!kgdb_io_module_registered) {
840                 kgdb_io_module_registered = 1;
841                 kgdb_arch_init();
842                 if (!dbg_is_early)
843                         kgdb_arch_late();
844                 register_module_notifier(&dbg_module_load_nb);
845                 register_reboot_notifier(&dbg_reboot_notifier);
846                 atomic_notifier_chain_register(&panic_notifier_list,
847                                                &kgdb_panic_event_nb);
848 #ifdef CONFIG_MAGIC_SYSRQ
849                 register_sysrq_key('g', &sysrq_dbg_op);
850 #endif
851                 if (kgdb_use_con && !kgdb_con_registered) {
852                         register_console(&kgdbcons);
853                         kgdb_con_registered = 1;
854                 }
855         }
856 }
857 
858 static void kgdb_unregister_callbacks(void)
859 {
860         /*
861          * When this routine is called KGDB should unregister from the
862          * panic handler and clean up, making sure it is not handling any
863          * break exceptions at the time.
864          */
865         if (kgdb_io_module_registered) {
866                 kgdb_io_module_registered = 0;
867                 unregister_reboot_notifier(&dbg_reboot_notifier);
868                 unregister_module_notifier(&dbg_module_load_nb);
869                 atomic_notifier_chain_unregister(&panic_notifier_list,
870                                                &kgdb_panic_event_nb);
871                 kgdb_arch_exit();
872 #ifdef CONFIG_MAGIC_SYSRQ
873                 unregister_sysrq_key('g', &sysrq_dbg_op);
874 #endif
875                 if (kgdb_con_registered) {
876                         unregister_console(&kgdbcons);
877                         kgdb_con_registered = 0;
878                 }
879         }
880 }
881 
882 /*
883  * There are times a tasklet needs to be used vs a compiled in
884  * break point so as to cause an exception outside a kgdb I/O module,
885  * such as is the case with kgdboe, where calling a breakpoint in the
886  * I/O driver itself would be fatal.
887  */
888 static void kgdb_tasklet_bpt(unsigned long ing)
889 {
890         kgdb_breakpoint();
891         atomic_set(&kgdb_break_tasklet_var, 0);
892 }
893 
894 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
895 
896 void kgdb_schedule_breakpoint(void)
897 {
898         if (atomic_read(&kgdb_break_tasklet_var) ||
899                 atomic_read(&kgdb_active) != -1 ||
900                 atomic_read(&kgdb_setting_breakpoint))
901                 return;
902         atomic_inc(&kgdb_break_tasklet_var);
903         tasklet_schedule(&kgdb_tasklet_breakpoint);
904 }
905 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
906 
907 static void kgdb_initial_breakpoint(void)
908 {
909         kgdb_break_asap = 0;
910 
911         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
912         kgdb_breakpoint();
913 }
914 
915 /**
916  *      kgdb_register_io_module - register KGDB IO module
917  *      @new_dbg_io_ops: the io ops vector
918  *
919  *      Register it with the KGDB core.
920  */
921 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
922 {
923         int err;
924 
925         spin_lock(&kgdb_registration_lock);
926 
927         if (dbg_io_ops) {
928                 spin_unlock(&kgdb_registration_lock);
929 
930                 printk(KERN_ERR "kgdb: Another I/O driver is already "
931                                 "registered with KGDB.\n");
932                 return -EBUSY;
933         }
934 
935         if (new_dbg_io_ops->init) {
936                 err = new_dbg_io_ops->init();
937                 if (err) {
938                         spin_unlock(&kgdb_registration_lock);
939                         return err;
940                 }
941         }
942 
943         dbg_io_ops = new_dbg_io_ops;
944 
945         spin_unlock(&kgdb_registration_lock);
946 
947         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
948                new_dbg_io_ops->name);
949 
950         /* Arm KGDB now. */
951         kgdb_register_callbacks();
952 
953         if (kgdb_break_asap)
954                 kgdb_initial_breakpoint();
955 
956         return 0;
957 }
958 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
959 
960 /**
961  *      kkgdb_unregister_io_module - unregister KGDB IO module
962  *      @old_dbg_io_ops: the io ops vector
963  *
964  *      Unregister it with the KGDB core.
965  */
966 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
967 {
968         BUG_ON(kgdb_connected);
969 
970         /*
971          * KGDB is no longer able to communicate out, so
972          * unregister our callbacks and reset state.
973          */
974         kgdb_unregister_callbacks();
975 
976         spin_lock(&kgdb_registration_lock);
977 
978         WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
979         dbg_io_ops = NULL;
980 
981         spin_unlock(&kgdb_registration_lock);
982 
983         printk(KERN_INFO
984                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
985                 old_dbg_io_ops->name);
986 }
987 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
988 
989 int dbg_io_get_char(void)
990 {
991         int ret = dbg_io_ops->read_char();
992         if (ret == NO_POLL_CHAR)
993                 return -1;
994         if (!dbg_kdb_mode)
995                 return ret;
996         if (ret == 127)
997                 return 8;
998         return ret;
999 }
1000 
1001 /**
1002  * kgdb_breakpoint - generate breakpoint exception
1003  *
1004  * This function will generate a breakpoint exception.  It is used at the
1005  * beginning of a program to sync up with a debugger and can be used
1006  * otherwise as a quick means to stop program execution and "break" into
1007  * the debugger.
1008  */
1009 void kgdb_breakpoint(void)
1010 {
1011         atomic_inc(&kgdb_setting_breakpoint);
1012         wmb(); /* Sync point before breakpoint */
1013         arch_kgdb_breakpoint();
1014         wmb(); /* Sync point after breakpoint */
1015         atomic_dec(&kgdb_setting_breakpoint);
1016 }
1017 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1018 
1019 static int __init opt_kgdb_wait(char *str)
1020 {
1021         kgdb_break_asap = 1;
1022 
1023         kdb_init(KDB_INIT_EARLY);
1024         if (kgdb_io_module_registered)
1025                 kgdb_initial_breakpoint();
1026 
1027         return 0;
1028 }
1029 
1030 early_param("kgdbwait", opt_kgdb_wait);
1031 

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