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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/interrupt.h>
 33 #include <linux/spinlock.h>
 34 #include <linux/console.h>
 35 #include <linux/threads.h>
 36 #include <linux/uaccess.h>
 37 #include <linux/kernel.h>
 38 #include <linux/module.h>
 39 #include <linux/ptrace.h>
 40 #include <linux/string.h>
 41 #include <linux/delay.h>
 42 #include <linux/sched.h>
 43 #include <linux/sysrq.h>
 44 #include <linux/reboot.h>
 45 #include <linux/init.h>
 46 #include <linux/kgdb.h>
 47 #include <linux/kdb.h>
 48 #include <linux/pid.h>
 49 #include <linux/smp.h>
 50 #include <linux/mm.h>
 51 #include <linux/rcupdate.h>
 52 
 53 #include <asm/cacheflush.h>
 54 #include <asm/byteorder.h>
 55 #include <linux/atomic.h>
 56 
 57 #include "debug_core.h"
 58 
 59 static int kgdb_break_asap;
 60 
 61 struct debuggerinfo_struct kgdb_info[NR_CPUS];
 62 
 63 /**
 64  * kgdb_connected - Is a host GDB connected to us?
 65  */
 66 int                             kgdb_connected;
 67 EXPORT_SYMBOL_GPL(kgdb_connected);
 68 
 69 /* All the KGDB handlers are installed */
 70 int                     kgdb_io_module_registered;
 71 
 72 /* Guard for recursive entry */
 73 static int                      exception_level;
 74 
 75 struct kgdb_io          *dbg_io_ops;
 76 static DEFINE_SPINLOCK(kgdb_registration_lock);
 77 
 78 /* Action for the reboot notifiter, a global allow kdb to change it */
 79 static int kgdbreboot;
 80 /* kgdb console driver is loaded */
 81 static int kgdb_con_registered;
 82 /* determine if kgdb console output should be used */
 83 static int kgdb_use_con;
 84 /* Flag for alternate operations for early debugging */
 85 bool dbg_is_early = true;
 86 /* Next cpu to become the master debug core */
 87 int dbg_switch_cpu;
 88 
 89 /* Use kdb or gdbserver mode */
 90 int dbg_kdb_mode = 1;
 91 
 92 static int __init opt_kgdb_con(char *str)
 93 {
 94         kgdb_use_con = 1;
 95         return 0;
 96 }
 97 
 98 early_param("kgdbcon", opt_kgdb_con);
 99 
100 module_param(kgdb_use_con, int, 0644);
101 module_param(kgdbreboot, int, 0644);
102 
103 /*
104  * Holds information about breakpoints in a kernel. These breakpoints are
105  * added and removed by gdb.
106  */
107 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
108         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
109 };
110 
111 /*
112  * The CPU# of the active CPU, or -1 if none:
113  */
114 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
115 EXPORT_SYMBOL_GPL(kgdb_active);
116 static DEFINE_RAW_SPINLOCK(dbg_master_lock);
117 static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
118 
119 /*
120  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
121  * bootup code (which might not have percpu set up yet):
122  */
123 static atomic_t                 masters_in_kgdb;
124 static atomic_t                 slaves_in_kgdb;
125 static atomic_t                 kgdb_break_tasklet_var;
126 atomic_t                        kgdb_setting_breakpoint;
127 
128 struct task_struct              *kgdb_usethread;
129 struct task_struct              *kgdb_contthread;
130 
131 int                             kgdb_single_step;
132 static pid_t                    kgdb_sstep_pid;
133 
134 /* to keep track of the CPU which is doing the single stepping*/
135 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
136 
137 /*
138  * If you are debugging a problem where roundup (the collection of
139  * all other CPUs) is a problem [this should be extremely rare],
140  * then use the nokgdbroundup option to avoid roundup. In that case
141  * the other CPUs might interfere with your debugging context, so
142  * use this with care:
143  */
144 static int kgdb_do_roundup = 1;
145 
146 static int __init opt_nokgdbroundup(char *str)
147 {
148         kgdb_do_roundup = 0;
149 
150         return 0;
151 }
152 
153 early_param("nokgdbroundup", opt_nokgdbroundup);
154 
155 /*
156  * Finally, some KGDB code :-)
157  */
158 
159 /*
160  * Weak aliases for breakpoint management,
161  * can be overriden by architectures when needed:
162  */
163 int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
164 {
165         int err;
166 
167         err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
168                                 BREAK_INSTR_SIZE);
169         if (err)
170                 return err;
171         err = probe_kernel_write((char *)bpt->bpt_addr,
172                                  arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
173         return err;
174 }
175 
176 int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
177 {
178         return probe_kernel_write((char *)bpt->bpt_addr,
179                                   (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
180 }
181 
182 int __weak kgdb_validate_break_address(unsigned long addr)
183 {
184         struct kgdb_bkpt tmp;
185         int err;
186         /* Validate setting the breakpoint and then removing it.  If the
187          * remove fails, the kernel needs to emit a bad message because we
188          * are deep trouble not being able to put things back the way we
189          * found them.
190          */
191         tmp.bpt_addr = addr;
192         err = kgdb_arch_set_breakpoint(&tmp);
193         if (err)
194                 return err;
195         err = kgdb_arch_remove_breakpoint(&tmp);
196         if (err)
197                 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
198                    "memory destroyed at: %lx", addr);
199         return err;
200 }
201 
202 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
203 {
204         return instruction_pointer(regs);
205 }
206 
207 int __weak kgdb_arch_init(void)
208 {
209         return 0;
210 }
211 
212 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
213 {
214         return 0;
215 }
216 
217 /*
218  * Some architectures need cache flushes when we set/clear a
219  * breakpoint:
220  */
221 static void kgdb_flush_swbreak_addr(unsigned long addr)
222 {
223         if (!CACHE_FLUSH_IS_SAFE)
224                 return;
225 
226         if (current->mm && current->mm->mmap_cache) {
227                 flush_cache_range(current->mm->mmap_cache,
228                                   addr, addr + BREAK_INSTR_SIZE);
229         }
230         /* Force flush instruction cache if it was outside the mm */
231         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
232 }
233 
234 /*
235  * SW breakpoint management:
236  */
237 int dbg_activate_sw_breakpoints(void)
238 {
239         int error;
240         int ret = 0;
241         int i;
242 
243         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
244                 if (kgdb_break[i].state != BP_SET)
245                         continue;
246 
247                 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
248                 if (error) {
249                         ret = error;
250                         printk(KERN_INFO "KGDB: BP install failed: %lx",
251                                kgdb_break[i].bpt_addr);
252                         continue;
253                 }
254 
255                 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
256                 kgdb_break[i].state = BP_ACTIVE;
257         }
258         return ret;
259 }
260 
261 int dbg_set_sw_break(unsigned long addr)
262 {
263         int err = kgdb_validate_break_address(addr);
264         int breakno = -1;
265         int i;
266 
267         if (err)
268                 return err;
269 
270         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
271                 if ((kgdb_break[i].state == BP_SET) &&
272                                         (kgdb_break[i].bpt_addr == addr))
273                         return -EEXIST;
274         }
275         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
276                 if (kgdb_break[i].state == BP_REMOVED &&
277                                         kgdb_break[i].bpt_addr == addr) {
278                         breakno = i;
279                         break;
280                 }
281         }
282 
283         if (breakno == -1) {
284                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
285                         if (kgdb_break[i].state == BP_UNDEFINED) {
286                                 breakno = i;
287                                 break;
288                         }
289                 }
290         }
291 
292         if (breakno == -1)
293                 return -E2BIG;
294 
295         kgdb_break[breakno].state = BP_SET;
296         kgdb_break[breakno].type = BP_BREAKPOINT;
297         kgdb_break[breakno].bpt_addr = addr;
298 
299         return 0;
300 }
301 
302 int dbg_deactivate_sw_breakpoints(void)
303 {
304         int error;
305         int ret = 0;
306         int i;
307 
308         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
309                 if (kgdb_break[i].state != BP_ACTIVE)
310                         continue;
311                 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
312                 if (error) {
313                         printk(KERN_INFO "KGDB: BP remove failed: %lx\n",
314                                kgdb_break[i].bpt_addr);
315                         ret = error;
316                 }
317 
318                 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
319                 kgdb_break[i].state = BP_SET;
320         }
321         return ret;
322 }
323 
324 int dbg_remove_sw_break(unsigned long addr)
325 {
326         int i;
327 
328         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
329                 if ((kgdb_break[i].state == BP_SET) &&
330                                 (kgdb_break[i].bpt_addr == addr)) {
331                         kgdb_break[i].state = BP_REMOVED;
332                         return 0;
333                 }
334         }
335         return -ENOENT;
336 }
337 
338 int kgdb_isremovedbreak(unsigned long addr)
339 {
340         int i;
341 
342         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
343                 if ((kgdb_break[i].state == BP_REMOVED) &&
344                                         (kgdb_break[i].bpt_addr == addr))
345                         return 1;
346         }
347         return 0;
348 }
349 
350 int dbg_remove_all_break(void)
351 {
352         int error;
353         int i;
354 
355         /* Clear memory breakpoints. */
356         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
357                 if (kgdb_break[i].state != BP_ACTIVE)
358                         goto setundefined;
359                 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
360                 if (error)
361                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
362                                kgdb_break[i].bpt_addr);
363 setundefined:
364                 kgdb_break[i].state = BP_UNDEFINED;
365         }
366 
367         /* Clear hardware breakpoints. */
368         if (arch_kgdb_ops.remove_all_hw_break)
369                 arch_kgdb_ops.remove_all_hw_break();
370 
371         return 0;
372 }
373 
374 /*
375  * Return true if there is a valid kgdb I/O module.  Also if no
376  * debugger is attached a message can be printed to the console about
377  * waiting for the debugger to attach.
378  *
379  * The print_wait argument is only to be true when called from inside
380  * the core kgdb_handle_exception, because it will wait for the
381  * debugger to attach.
382  */
383 static int kgdb_io_ready(int print_wait)
384 {
385         if (!dbg_io_ops)
386                 return 0;
387         if (kgdb_connected)
388                 return 1;
389         if (atomic_read(&kgdb_setting_breakpoint))
390                 return 1;
391         if (print_wait) {
392 #ifdef CONFIG_KGDB_KDB
393                 if (!dbg_kdb_mode)
394                         printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
395 #else
396                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
397 #endif
398         }
399         return 1;
400 }
401 
402 static int kgdb_reenter_check(struct kgdb_state *ks)
403 {
404         unsigned long addr;
405 
406         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
407                 return 0;
408 
409         /* Panic on recursive debugger calls: */
410         exception_level++;
411         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
412         dbg_deactivate_sw_breakpoints();
413 
414         /*
415          * If the break point removed ok at the place exception
416          * occurred, try to recover and print a warning to the end
417          * user because the user planted a breakpoint in a place that
418          * KGDB needs in order to function.
419          */
420         if (dbg_remove_sw_break(addr) == 0) {
421                 exception_level = 0;
422                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
423                 dbg_activate_sw_breakpoints();
424                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
425                         addr);
426                 WARN_ON_ONCE(1);
427 
428                 return 1;
429         }
430         dbg_remove_all_break();
431         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
432 
433         if (exception_level > 1) {
434                 dump_stack();
435                 panic("Recursive entry to debugger");
436         }
437 
438         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
439 #ifdef CONFIG_KGDB_KDB
440         /* Allow kdb to debug itself one level */
441         return 0;
442 #endif
443         dump_stack();
444         panic("Recursive entry to debugger");
445 
446         return 1;
447 }
448 
449 static void dbg_touch_watchdogs(void)
450 {
451         touch_softlockup_watchdog_sync();
452         clocksource_touch_watchdog();
453         rcu_cpu_stall_reset();
454 }
455 
456 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
457                 int exception_state)
458 {
459         unsigned long flags;
460         int sstep_tries = 100;
461         int error;
462         int cpu;
463         int trace_on = 0;
464         int online_cpus = num_online_cpus();
465 
466         kgdb_info[ks->cpu].enter_kgdb++;
467         kgdb_info[ks->cpu].exception_state |= exception_state;
468 
469         if (exception_state == DCPU_WANT_MASTER)
470                 atomic_inc(&masters_in_kgdb);
471         else
472                 atomic_inc(&slaves_in_kgdb);
473 
474         if (arch_kgdb_ops.disable_hw_break)
475                 arch_kgdb_ops.disable_hw_break(regs);
476 
477 acquirelock:
478         /*
479          * Interrupts will be restored by the 'trap return' code, except when
480          * single stepping.
481          */
482         local_irq_save(flags);
483 
484         cpu = ks->cpu;
485         kgdb_info[cpu].debuggerinfo = regs;
486         kgdb_info[cpu].task = current;
487         kgdb_info[cpu].ret_state = 0;
488         kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
489 
490         /* Make sure the above info reaches the primary CPU */
491         smp_mb();
492 
493         if (exception_level == 1) {
494                 if (raw_spin_trylock(&dbg_master_lock))
495                         atomic_xchg(&kgdb_active, cpu);
496                 goto cpu_master_loop;
497         }
498 
499         /*
500          * CPU will loop if it is a slave or request to become a kgdb
501          * master cpu and acquire the kgdb_active lock:
502          */
503         while (1) {
504 cpu_loop:
505                 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
506                         kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
507                         goto cpu_master_loop;
508                 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
509                         if (raw_spin_trylock(&dbg_master_lock)) {
510                                 atomic_xchg(&kgdb_active, cpu);
511                                 break;
512                         }
513                 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
514                         if (!raw_spin_is_locked(&dbg_slave_lock))
515                                 goto return_normal;
516                 } else {
517 return_normal:
518                         /* Return to normal operation by executing any
519                          * hw breakpoint fixup.
520                          */
521                         if (arch_kgdb_ops.correct_hw_break)
522                                 arch_kgdb_ops.correct_hw_break();
523                         if (trace_on)
524                                 tracing_on();
525                         kgdb_info[cpu].exception_state &=
526                                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
527                         kgdb_info[cpu].enter_kgdb--;
528                         smp_mb__before_atomic_dec();
529                         atomic_dec(&slaves_in_kgdb);
530                         dbg_touch_watchdogs();
531                         local_irq_restore(flags);
532                         return 0;
533                 }
534                 cpu_relax();
535         }
536 
537         /*
538          * For single stepping, try to only enter on the processor
539          * that was single stepping.  To guard against a deadlock, the
540          * kernel will only try for the value of sstep_tries before
541          * giving up and continuing on.
542          */
543         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
544             (kgdb_info[cpu].task &&
545              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
546                 atomic_set(&kgdb_active, -1);
547                 raw_spin_unlock(&dbg_master_lock);
548                 dbg_touch_watchdogs();
549                 local_irq_restore(flags);
550 
551                 goto acquirelock;
552         }
553 
554         if (!kgdb_io_ready(1)) {
555                 kgdb_info[cpu].ret_state = 1;
556                 goto kgdb_restore; /* No I/O connection, resume the system */
557         }
558 
559         /*
560          * Don't enter if we have hit a removed breakpoint.
561          */
562         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
563                 goto kgdb_restore;
564 
565         /* Call the I/O driver's pre_exception routine */
566         if (dbg_io_ops->pre_exception)
567                 dbg_io_ops->pre_exception();
568 
569         /*
570          * Get the passive CPU lock which will hold all the non-primary
571          * CPU in a spin state while the debugger is active
572          */
573         if (!kgdb_single_step)
574                 raw_spin_lock(&dbg_slave_lock);
575 
576 #ifdef CONFIG_SMP
577         /* Signal the other CPUs to enter kgdb_wait() */
578         if ((!kgdb_single_step) && kgdb_do_roundup)
579                 kgdb_roundup_cpus(flags);
580 #endif
581 
582         /*
583          * Wait for the other CPUs to be notified and be waiting for us:
584          */
585         while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) +
586                                 atomic_read(&slaves_in_kgdb)) != online_cpus)
587                 cpu_relax();
588 
589         /*
590          * At this point the primary processor is completely
591          * in the debugger and all secondary CPUs are quiescent
592          */
593         dbg_deactivate_sw_breakpoints();
594         kgdb_single_step = 0;
595         kgdb_contthread = current;
596         exception_level = 0;
597         trace_on = tracing_is_on();
598         if (trace_on)
599                 tracing_off();
600 
601         while (1) {
602 cpu_master_loop:
603                 if (dbg_kdb_mode) {
604                         kgdb_connected = 1;
605                         error = kdb_stub(ks);
606                         if (error == -1)
607                                 continue;
608                         kgdb_connected = 0;
609                 } else {
610                         error = gdb_serial_stub(ks);
611                 }
612 
613                 if (error == DBG_PASS_EVENT) {
614                         dbg_kdb_mode = !dbg_kdb_mode;
615                 } else if (error == DBG_SWITCH_CPU_EVENT) {
616                         kgdb_info[dbg_switch_cpu].exception_state |=
617                                 DCPU_NEXT_MASTER;
618                         goto cpu_loop;
619                 } else {
620                         kgdb_info[cpu].ret_state = error;
621                         break;
622                 }
623         }
624 
625         /* Call the I/O driver's post_exception routine */
626         if (dbg_io_ops->post_exception)
627                 dbg_io_ops->post_exception();
628 
629         if (!kgdb_single_step) {
630                 raw_spin_unlock(&dbg_slave_lock);
631                 /* Wait till all the CPUs have quit from the debugger. */
632                 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
633                         cpu_relax();
634         }
635 
636 kgdb_restore:
637         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
638                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
639                 if (kgdb_info[sstep_cpu].task)
640                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
641                 else
642                         kgdb_sstep_pid = 0;
643         }
644         if (arch_kgdb_ops.correct_hw_break)
645                 arch_kgdb_ops.correct_hw_break();
646         if (trace_on)
647                 tracing_on();
648 
649         kgdb_info[cpu].exception_state &=
650                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
651         kgdb_info[cpu].enter_kgdb--;
652         smp_mb__before_atomic_dec();
653         atomic_dec(&masters_in_kgdb);
654         /* Free kgdb_active */
655         atomic_set(&kgdb_active, -1);
656         raw_spin_unlock(&dbg_master_lock);
657         dbg_touch_watchdogs();
658         local_irq_restore(flags);
659 
660         return kgdb_info[cpu].ret_state;
661 }
662 
663 /*
664  * kgdb_handle_exception() - main entry point from a kernel exception
665  *
666  * Locking hierarchy:
667  *      interface locks, if any (begin_session)
668  *      kgdb lock (kgdb_active)
669  */
670 int
671 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
672 {
673         struct kgdb_state kgdb_var;
674         struct kgdb_state *ks = &kgdb_var;
675         int ret = 0;
676 
677         if (arch_kgdb_ops.enable_nmi)
678                 arch_kgdb_ops.enable_nmi(0);
679 
680         ks->cpu                 = raw_smp_processor_id();
681         ks->ex_vector           = evector;
682         ks->signo               = signo;
683         ks->err_code            = ecode;
684         ks->kgdb_usethreadid    = 0;
685         ks->linux_regs          = regs;
686 
687         if (kgdb_reenter_check(ks))
688                 goto out; /* Ouch, double exception ! */
689         if (kgdb_info[ks->cpu].enter_kgdb != 0)
690                 goto out;
691 
692         ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
693 out:
694         if (arch_kgdb_ops.enable_nmi)
695                 arch_kgdb_ops.enable_nmi(1);
696         return ret;
697 }
698 
699 /*
700  * GDB places a breakpoint at this function to know dynamically
701  * loaded objects. It's not defined static so that only one instance with this
702  * name exists in the kernel.
703  */
704 
705 static int module_event(struct notifier_block *self, unsigned long val,
706         void *data)
707 {
708         return 0;
709 }
710 
711 static struct notifier_block dbg_module_load_nb = {
712         .notifier_call  = module_event,
713 };
714 
715 int kgdb_nmicallback(int cpu, void *regs)
716 {
717 #ifdef CONFIG_SMP
718         struct kgdb_state kgdb_var;
719         struct kgdb_state *ks = &kgdb_var;
720 
721         memset(ks, 0, sizeof(struct kgdb_state));
722         ks->cpu                 = cpu;
723         ks->linux_regs          = regs;
724 
725         if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
726                         raw_spin_is_locked(&dbg_master_lock)) {
727                 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
728                 return 0;
729         }
730 #endif
731         return 1;
732 }
733 
734 static void kgdb_console_write(struct console *co, const char *s,
735    unsigned count)
736 {
737         unsigned long flags;
738 
739         /* If we're debugging, or KGDB has not connected, don't try
740          * and print. */
741         if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
742                 return;
743 
744         local_irq_save(flags);
745         gdbstub_msg_write(s, count);
746         local_irq_restore(flags);
747 }
748 
749 static struct console kgdbcons = {
750         .name           = "kgdb",
751         .write          = kgdb_console_write,
752         .flags          = CON_PRINTBUFFER | CON_ENABLED,
753         .index          = -1,
754 };
755 
756 #ifdef CONFIG_MAGIC_SYSRQ
757 static void sysrq_handle_dbg(int key)
758 {
759         if (!dbg_io_ops) {
760                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
761                 return;
762         }
763         if (!kgdb_connected) {
764 #ifdef CONFIG_KGDB_KDB
765                 if (!dbg_kdb_mode)
766                         printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
767 #else
768                 printk(KERN_CRIT "Entering KGDB\n");
769 #endif
770         }
771 
772         kgdb_breakpoint();
773 }
774 
775 static struct sysrq_key_op sysrq_dbg_op = {
776         .handler        = sysrq_handle_dbg,
777         .help_msg       = "debug(G)",
778         .action_msg     = "DEBUG",
779 };
780 #endif
781 
782 static int kgdb_panic_event(struct notifier_block *self,
783                             unsigned long val,
784                             void *data)
785 {
786         if (dbg_kdb_mode)
787                 kdb_printf("PANIC: %s\n", (char *)data);
788         kgdb_breakpoint();
789         return NOTIFY_DONE;
790 }
791 
792 static struct notifier_block kgdb_panic_event_nb = {
793        .notifier_call   = kgdb_panic_event,
794        .priority        = INT_MAX,
795 };
796 
797 void __weak kgdb_arch_late(void)
798 {
799 }
800 
801 void __init dbg_late_init(void)
802 {
803         dbg_is_early = false;
804         if (kgdb_io_module_registered)
805                 kgdb_arch_late();
806         kdb_init(KDB_INIT_FULL);
807 }
808 
809 static int
810 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
811 {
812         /*
813          * Take the following action on reboot notify depending on value:
814          *    1 == Enter debugger
815          *    0 == [the default] detatch debug client
816          *   -1 == Do nothing... and use this until the board resets
817          */
818         switch (kgdbreboot) {
819         case 1:
820                 kgdb_breakpoint();
821         case -1:
822                 goto done;
823         }
824         if (!dbg_kdb_mode)
825                 gdbstub_exit(code);
826 done:
827         return NOTIFY_DONE;
828 }
829 
830 static struct notifier_block dbg_reboot_notifier = {
831         .notifier_call          = dbg_notify_reboot,
832         .next                   = NULL,
833         .priority               = INT_MAX,
834 };
835 
836 static void kgdb_register_callbacks(void)
837 {
838         if (!kgdb_io_module_registered) {
839                 kgdb_io_module_registered = 1;
840                 kgdb_arch_init();
841                 if (!dbg_is_early)
842                         kgdb_arch_late();
843                 register_module_notifier(&dbg_module_load_nb);
844                 register_reboot_notifier(&dbg_reboot_notifier);
845                 atomic_notifier_chain_register(&panic_notifier_list,
846                                                &kgdb_panic_event_nb);
847 #ifdef CONFIG_MAGIC_SYSRQ
848                 register_sysrq_key('g', &sysrq_dbg_op);
849 #endif
850                 if (kgdb_use_con && !kgdb_con_registered) {
851                         register_console(&kgdbcons);
852                         kgdb_con_registered = 1;
853                 }
854         }
855 }
856 
857 static void kgdb_unregister_callbacks(void)
858 {
859         /*
860          * When this routine is called KGDB should unregister from the
861          * panic handler and clean up, making sure it is not handling any
862          * break exceptions at the time.
863          */
864         if (kgdb_io_module_registered) {
865                 kgdb_io_module_registered = 0;
866                 unregister_reboot_notifier(&dbg_reboot_notifier);
867                 unregister_module_notifier(&dbg_module_load_nb);
868                 atomic_notifier_chain_unregister(&panic_notifier_list,
869                                                &kgdb_panic_event_nb);
870                 kgdb_arch_exit();
871 #ifdef CONFIG_MAGIC_SYSRQ
872                 unregister_sysrq_key('g', &sysrq_dbg_op);
873 #endif
874                 if (kgdb_con_registered) {
875                         unregister_console(&kgdbcons);
876                         kgdb_con_registered = 0;
877                 }
878         }
879 }
880 
881 /*
882  * There are times a tasklet needs to be used vs a compiled in
883  * break point so as to cause an exception outside a kgdb I/O module,
884  * such as is the case with kgdboe, where calling a breakpoint in the
885  * I/O driver itself would be fatal.
886  */
887 static void kgdb_tasklet_bpt(unsigned long ing)
888 {
889         kgdb_breakpoint();
890         atomic_set(&kgdb_break_tasklet_var, 0);
891 }
892 
893 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
894 
895 void kgdb_schedule_breakpoint(void)
896 {
897         if (atomic_read(&kgdb_break_tasklet_var) ||
898                 atomic_read(&kgdb_active) != -1 ||
899                 atomic_read(&kgdb_setting_breakpoint))
900                 return;
901         atomic_inc(&kgdb_break_tasklet_var);
902         tasklet_schedule(&kgdb_tasklet_breakpoint);
903 }
904 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
905 
906 static void kgdb_initial_breakpoint(void)
907 {
908         kgdb_break_asap = 0;
909 
910         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
911         kgdb_breakpoint();
912 }
913 
914 /**
915  *      kgdb_register_io_module - register KGDB IO module
916  *      @new_dbg_io_ops: the io ops vector
917  *
918  *      Register it with the KGDB core.
919  */
920 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
921 {
922         int err;
923 
924         spin_lock(&kgdb_registration_lock);
925 
926         if (dbg_io_ops) {
927                 spin_unlock(&kgdb_registration_lock);
928 
929                 printk(KERN_ERR "kgdb: Another I/O driver is already "
930                                 "registered with KGDB.\n");
931                 return -EBUSY;
932         }
933 
934         if (new_dbg_io_ops->init) {
935                 err = new_dbg_io_ops->init();
936                 if (err) {
937                         spin_unlock(&kgdb_registration_lock);
938                         return err;
939                 }
940         }
941 
942         dbg_io_ops = new_dbg_io_ops;
943 
944         spin_unlock(&kgdb_registration_lock);
945 
946         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
947                new_dbg_io_ops->name);
948 
949         /* Arm KGDB now. */
950         kgdb_register_callbacks();
951 
952         if (kgdb_break_asap)
953                 kgdb_initial_breakpoint();
954 
955         return 0;
956 }
957 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
958 
959 /**
960  *      kkgdb_unregister_io_module - unregister KGDB IO module
961  *      @old_dbg_io_ops: the io ops vector
962  *
963  *      Unregister it with the KGDB core.
964  */
965 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
966 {
967         BUG_ON(kgdb_connected);
968 
969         /*
970          * KGDB is no longer able to communicate out, so
971          * unregister our callbacks and reset state.
972          */
973         kgdb_unregister_callbacks();
974 
975         spin_lock(&kgdb_registration_lock);
976 
977         WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
978         dbg_io_ops = NULL;
979 
980         spin_unlock(&kgdb_registration_lock);
981 
982         printk(KERN_INFO
983                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
984                 old_dbg_io_ops->name);
985 }
986 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
987 
988 int dbg_io_get_char(void)
989 {
990         int ret = dbg_io_ops->read_char();
991         if (ret == NO_POLL_CHAR)
992                 return -1;
993         if (!dbg_kdb_mode)
994                 return ret;
995         if (ret == 127)
996                 return 8;
997         return ret;
998 }
999 
1000 /**
1001  * kgdb_breakpoint - generate breakpoint exception
1002  *
1003  * This function will generate a breakpoint exception.  It is used at the
1004  * beginning of a program to sync up with a debugger and can be used
1005  * otherwise as a quick means to stop program execution and "break" into
1006  * the debugger.
1007  */
1008 void kgdb_breakpoint(void)
1009 {
1010         atomic_inc(&kgdb_setting_breakpoint);
1011         wmb(); /* Sync point before breakpoint */
1012         arch_kgdb_breakpoint();
1013         wmb(); /* Sync point after breakpoint */
1014         atomic_dec(&kgdb_setting_breakpoint);
1015 }
1016 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1017 
1018 static int __init opt_kgdb_wait(char *str)
1019 {
1020         kgdb_break_asap = 1;
1021 
1022         kdb_init(KDB_INIT_EARLY);
1023         if (kgdb_io_module_registered)
1024                 kgdb_initial_breakpoint();
1025 
1026         return 0;
1027 }
1028 
1029 early_param("kgdbwait", opt_kgdb_wait);
1030 

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