4 * Maintainer: Jason Wessel <jason.wessel@windriver.com>
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>
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.
23 * Original KGDB stub: David Grothe <dave@gcom.com>,
24 * Tigran Aivazian <tigran@sco.com>
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.
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>
51 #include <asm/cacheflush.h>
52 #include <asm/byteorder.h>
53 #include <asm/atomic.h>
54 #include <asm/system.h>
56 #include "debug_core.h"
58 static int kgdb_break_asap;
60 struct debuggerinfo_struct kgdb_info[NR_CPUS];
63 * kgdb_connected - Is a host GDB connected to us?
66 EXPORT_SYMBOL_GPL(kgdb_connected);
68 /* All the KGDB handlers are installed */
69 int kgdb_io_module_registered;
71 /* Guard for recursive entry */
72 static int exception_level;
74 struct kgdb_io *dbg_io_ops;
75 static DEFINE_SPINLOCK(kgdb_registration_lock);
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 */
86 /* Use kdb or gdbserver mode */
89 static int __init opt_kgdb_con(char *str)
95 early_param("kgdbcon", opt_kgdb_con);
97 module_param(kgdb_use_con, int, 0644);
100 * Holds information about breakpoints in a kernel. These breakpoints are
101 * added and removed by gdb.
103 static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
104 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
108 * The CPU# of the active CPU, or -1 if none:
110 atomic_t kgdb_active = ATOMIC_INIT(-1);
111 EXPORT_SYMBOL_GPL(kgdb_active);
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):
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;
122 struct task_struct *kgdb_usethread;
123 struct task_struct *kgdb_contthread;
125 int kgdb_single_step;
126 static pid_t kgdb_sstep_pid;
128 /* to keep track of the CPU which is doing the single stepping*/
129 atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
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:
138 static int kgdb_do_roundup = 1;
140 static int __init opt_nokgdbroundup(char *str)
147 early_param("nokgdbroundup", opt_nokgdbroundup);
150 * Finally, some KGDB code :-)
154 * Weak aliases for breakpoint management,
155 * can be overriden by architectures when needed:
157 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
161 err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
165 return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
169 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
171 return probe_kernel_write((char *)addr,
172 (char *)bundle, BREAK_INSTR_SIZE);
175 int __weak kgdb_validate_break_address(unsigned long addr)
177 char tmp_variable[BREAK_INSTR_SIZE];
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
184 err = kgdb_arch_set_breakpoint(addr, tmp_variable);
187 err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
189 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
190 "memory destroyed at: %lx", addr);
194 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
196 return instruction_pointer(regs);
199 int __weak kgdb_arch_init(void)
204 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
210 * kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
211 * @regs: Current &struct pt_regs.
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.
217 void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
222 * Some architectures need cache flushes when we set/clear a
225 static void kgdb_flush_swbreak_addr(unsigned long addr)
227 if (!CACHE_FLUSH_IS_SAFE)
230 if (current->mm && current->mm->mmap_cache) {
231 flush_cache_range(current->mm->mmap_cache,
232 addr, addr + BREAK_INSTR_SIZE);
234 /* Force flush instruction cache if it was outside the mm */
235 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
239 * SW breakpoint management:
241 int dbg_activate_sw_breakpoints(void)
248 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
249 if (kgdb_break[i].state != BP_SET)
252 addr = kgdb_break[i].bpt_addr;
253 error = kgdb_arch_set_breakpoint(addr,
254 kgdb_break[i].saved_instr);
257 printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
261 kgdb_flush_swbreak_addr(addr);
262 kgdb_break[i].state = BP_ACTIVE;
267 int dbg_set_sw_break(unsigned long addr)
269 int err = kgdb_validate_break_address(addr);
276 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
277 if ((kgdb_break[i].state == BP_SET) &&
278 (kgdb_break[i].bpt_addr == addr))
281 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
282 if (kgdb_break[i].state == BP_REMOVED &&
283 kgdb_break[i].bpt_addr == addr) {
290 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
291 if (kgdb_break[i].state == BP_UNDEFINED) {
301 kgdb_break[breakno].state = BP_SET;
302 kgdb_break[breakno].type = BP_BREAKPOINT;
303 kgdb_break[breakno].bpt_addr = addr;
308 int dbg_deactivate_sw_breakpoints(void)
315 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
316 if (kgdb_break[i].state != BP_ACTIVE)
318 addr = kgdb_break[i].bpt_addr;
319 error = kgdb_arch_remove_breakpoint(addr,
320 kgdb_break[i].saved_instr);
322 printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
326 kgdb_flush_swbreak_addr(addr);
327 kgdb_break[i].state = BP_SET;
332 int dbg_remove_sw_break(unsigned long addr)
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;
346 int kgdb_isremovedbreak(unsigned long addr)
350 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
351 if ((kgdb_break[i].state == BP_REMOVED) &&
352 (kgdb_break[i].bpt_addr == addr))
358 int dbg_remove_all_break(void)
364 /* Clear memory breakpoints. */
365 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
366 if (kgdb_break[i].state != BP_ACTIVE)
368 addr = kgdb_break[i].bpt_addr;
369 error = kgdb_arch_remove_breakpoint(addr,
370 kgdb_break[i].saved_instr);
372 printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
375 kgdb_break[i].state = BP_UNDEFINED;
378 /* Clear hardware breakpoints. */
379 if (arch_kgdb_ops.remove_all_hw_break)
380 arch_kgdb_ops.remove_all_hw_break();
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.
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.
394 static int kgdb_io_ready(int print_wait)
400 if (atomic_read(&kgdb_setting_breakpoint))
403 #ifdef CONFIG_KGDB_KDB
405 printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
407 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
413 static int kgdb_reenter_check(struct kgdb_state *ks)
417 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
420 /* Panic on recursive debugger calls: */
422 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
423 dbg_deactivate_sw_breakpoints();
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.
431 if (dbg_remove_sw_break(addr) == 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",
441 dbg_remove_all_break();
442 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
444 if (exception_level > 1) {
446 panic("Recursive entry to debugger");
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 */
455 panic("Recursive entry to debugger");
460 static void dbg_cpu_switch(int cpu, int next_cpu)
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;
470 kgdb_info[next_cpu].exception_state |= DCPU_NEXT_MASTER;
473 static void dbg_touch_watchdogs(void)
475 touch_softlockup_watchdog_sync();
476 clocksource_touch_watchdog();
479 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
482 int sstep_tries = 100;
488 * Interrupts will be restored by the 'trap return' code, except when
491 local_irq_save(flags);
494 kgdb_info[cpu].debuggerinfo = regs;
495 kgdb_info[cpu].task = current;
496 kgdb_info[cpu].ret_state = 0;
497 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
499 * Make sure the above info reaches the primary CPU before
500 * our cpu_in_kgdb[] flag setting does:
502 atomic_inc(&cpu_in_kgdb[cpu]);
504 if (exception_level == 1)
505 goto cpu_master_loop;
508 * CPU will loop if it is a slave or request to become a kgdb
509 * master cpu and acquire the kgdb_active lock:
513 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
514 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
515 goto cpu_master_loop;
516 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
517 if (atomic_cmpxchg(&kgdb_active, -1, cpu) == cpu)
519 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
520 if (!atomic_read(&passive_cpu_wait[cpu]))
524 /* Return to normal operation by executing any
525 * hw breakpoint fixup.
527 if (arch_kgdb_ops.correct_hw_break)
528 arch_kgdb_ops.correct_hw_break();
531 atomic_dec(&cpu_in_kgdb[cpu]);
532 dbg_touch_watchdogs();
533 local_irq_restore(flags);
540 * For single stepping, try to only enter on the processor
541 * that was single stepping. To gaurd against a deadlock, the
542 * kernel will only try for the value of sstep_tries before
543 * giving up and continuing on.
545 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
546 (kgdb_info[cpu].task &&
547 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
548 atomic_set(&kgdb_active, -1);
549 dbg_touch_watchdogs();
550 local_irq_restore(flags);
555 if (!kgdb_io_ready(1)) {
556 kgdb_info[cpu].ret_state = 1;
557 goto kgdb_restore; /* No I/O connection, resume the system */
561 * Don't enter if we have hit a removed breakpoint.
563 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
566 /* Call the I/O driver's pre_exception routine */
567 if (dbg_io_ops->pre_exception)
568 dbg_io_ops->pre_exception();
570 kgdb_disable_hw_debug(ks->linux_regs);
573 * Get the passive CPU lock which will hold all the non-primary
574 * CPU in a spin state while the debugger is active
576 if (!kgdb_single_step) {
577 for (i = 0; i < NR_CPUS; i++)
578 atomic_inc(&passive_cpu_wait[i]);
582 /* Signal the other CPUs to enter kgdb_wait() */
583 if ((!kgdb_single_step) && kgdb_do_roundup)
584 kgdb_roundup_cpus(flags);
588 * Wait for the other CPUs to be notified and be waiting for us:
590 for_each_online_cpu(i) {
591 while (kgdb_do_roundup && !atomic_read(&cpu_in_kgdb[i]))
596 * At this point the primary processor is completely
597 * in the debugger and all secondary CPUs are quiescent
599 dbg_deactivate_sw_breakpoints();
600 kgdb_single_step = 0;
601 kgdb_contthread = current;
603 trace_on = tracing_is_on();
611 error = kdb_stub(ks);
616 error = gdb_serial_stub(ks);
619 if (error == DBG_PASS_EVENT) {
620 dbg_kdb_mode = !dbg_kdb_mode;
621 } else if (error == DBG_SWITCH_CPU_EVENT) {
622 dbg_cpu_switch(cpu, dbg_switch_cpu);
625 kgdb_info[cpu].ret_state = error;
630 /* Call the I/O driver's post_exception routine */
631 if (dbg_io_ops->post_exception)
632 dbg_io_ops->post_exception();
634 atomic_dec(&cpu_in_kgdb[ks->cpu]);
636 if (!kgdb_single_step) {
637 for (i = NR_CPUS-1; i >= 0; i--)
638 atomic_dec(&passive_cpu_wait[i]);
640 * Wait till all the CPUs have quit from the debugger,
641 * but allow a CPU that hit an exception and is
642 * waiting to become the master to remain in the debug
645 for_each_online_cpu(i) {
646 while (kgdb_do_roundup &&
647 atomic_read(&cpu_in_kgdb[i]) &&
648 !(kgdb_info[i].exception_state &
655 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
656 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
657 if (kgdb_info[sstep_cpu].task)
658 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
664 /* Free kgdb_active */
665 atomic_set(&kgdb_active, -1);
666 dbg_touch_watchdogs();
667 local_irq_restore(flags);
669 return kgdb_info[cpu].ret_state;
673 * kgdb_handle_exception() - main entry point from a kernel exception
676 * interface locks, if any (begin_session)
677 * kgdb lock (kgdb_active)
680 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
682 struct kgdb_state kgdb_var;
683 struct kgdb_state *ks = &kgdb_var;
686 ks->cpu = raw_smp_processor_id();
687 ks->ex_vector = evector;
689 ks->err_code = ecode;
690 ks->kgdb_usethreadid = 0;
691 ks->linux_regs = regs;
693 if (kgdb_reenter_check(ks))
694 return 0; /* Ouch, double exception ! */
695 kgdb_info[ks->cpu].exception_state |= DCPU_WANT_MASTER;
696 ret = kgdb_cpu_enter(ks, regs);
697 kgdb_info[ks->cpu].exception_state &= ~(DCPU_WANT_MASTER |
702 int kgdb_nmicallback(int cpu, void *regs)
705 struct kgdb_state kgdb_var;
706 struct kgdb_state *ks = &kgdb_var;
708 memset(ks, 0, sizeof(struct kgdb_state));
710 ks->linux_regs = regs;
712 if (!atomic_read(&cpu_in_kgdb[cpu]) &&
713 atomic_read(&kgdb_active) != -1 &&
714 atomic_read(&kgdb_active) != cpu) {
715 kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
716 kgdb_cpu_enter(ks, regs);
717 kgdb_info[cpu].exception_state &= ~DCPU_IS_SLAVE;
724 static void kgdb_console_write(struct console *co, const char *s,
729 /* If we're debugging, or KGDB has not connected, don't try
731 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
734 local_irq_save(flags);
735 gdbstub_msg_write(s, count);
736 local_irq_restore(flags);
739 static struct console kgdbcons = {
741 .write = kgdb_console_write,
742 .flags = CON_PRINTBUFFER | CON_ENABLED,
746 #ifdef CONFIG_MAGIC_SYSRQ
747 static void sysrq_handle_dbg(int key)
750 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
753 if (!kgdb_connected) {
754 #ifdef CONFIG_KGDB_KDB
756 printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
758 printk(KERN_CRIT "Entering KGDB\n");
765 static struct sysrq_key_op sysrq_dbg_op = {
766 .handler = sysrq_handle_dbg,
767 .help_msg = "debug(G)",
768 .action_msg = "DEBUG",
772 static int kgdb_panic_event(struct notifier_block *self,
777 kdb_printf("PANIC: %s\n", (char *)data);
782 static struct notifier_block kgdb_panic_event_nb = {
783 .notifier_call = kgdb_panic_event,
787 void __weak kgdb_arch_late(void)
791 void __init dbg_late_init(void)
793 dbg_is_early = false;
794 if (kgdb_io_module_registered)
796 kdb_init(KDB_INIT_FULL);
799 static void kgdb_register_callbacks(void)
801 if (!kgdb_io_module_registered) {
802 kgdb_io_module_registered = 1;
806 atomic_notifier_chain_register(&panic_notifier_list,
807 &kgdb_panic_event_nb);
808 #ifdef CONFIG_MAGIC_SYSRQ
809 register_sysrq_key('g', &sysrq_dbg_op);
811 if (kgdb_use_con && !kgdb_con_registered) {
812 register_console(&kgdbcons);
813 kgdb_con_registered = 1;
818 static void kgdb_unregister_callbacks(void)
821 * When this routine is called KGDB should unregister from the
822 * panic handler and clean up, making sure it is not handling any
823 * break exceptions at the time.
825 if (kgdb_io_module_registered) {
826 kgdb_io_module_registered = 0;
827 atomic_notifier_chain_unregister(&panic_notifier_list,
828 &kgdb_panic_event_nb);
830 #ifdef CONFIG_MAGIC_SYSRQ
831 unregister_sysrq_key('g', &sysrq_dbg_op);
833 if (kgdb_con_registered) {
834 unregister_console(&kgdbcons);
835 kgdb_con_registered = 0;
841 * There are times a tasklet needs to be used vs a compiled in
842 * break point so as to cause an exception outside a kgdb I/O module,
843 * such as is the case with kgdboe, where calling a breakpoint in the
844 * I/O driver itself would be fatal.
846 static void kgdb_tasklet_bpt(unsigned long ing)
849 atomic_set(&kgdb_break_tasklet_var, 0);
852 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
854 void kgdb_schedule_breakpoint(void)
856 if (atomic_read(&kgdb_break_tasklet_var) ||
857 atomic_read(&kgdb_active) != -1 ||
858 atomic_read(&kgdb_setting_breakpoint))
860 atomic_inc(&kgdb_break_tasklet_var);
861 tasklet_schedule(&kgdb_tasklet_breakpoint);
863 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
865 static void kgdb_initial_breakpoint(void)
869 printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
874 * kgdb_register_io_module - register KGDB IO module
875 * @new_dbg_io_ops: the io ops vector
877 * Register it with the KGDB core.
879 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
883 spin_lock(&kgdb_registration_lock);
886 spin_unlock(&kgdb_registration_lock);
888 printk(KERN_ERR "kgdb: Another I/O driver is already "
889 "registered with KGDB.\n");
893 if (new_dbg_io_ops->init) {
894 err = new_dbg_io_ops->init();
896 spin_unlock(&kgdb_registration_lock);
901 dbg_io_ops = new_dbg_io_ops;
903 spin_unlock(&kgdb_registration_lock);
905 printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
906 new_dbg_io_ops->name);
909 kgdb_register_callbacks();
912 kgdb_initial_breakpoint();
916 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
919 * kkgdb_unregister_io_module - unregister KGDB IO module
920 * @old_dbg_io_ops: the io ops vector
922 * Unregister it with the KGDB core.
924 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
926 BUG_ON(kgdb_connected);
929 * KGDB is no longer able to communicate out, so
930 * unregister our callbacks and reset state.
932 kgdb_unregister_callbacks();
934 spin_lock(&kgdb_registration_lock);
936 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
939 spin_unlock(&kgdb_registration_lock);
942 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
943 old_dbg_io_ops->name);
945 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
947 int dbg_io_get_char(void)
949 int ret = dbg_io_ops->read_char();
950 if (ret == NO_POLL_CHAR)
960 * kgdb_breakpoint - generate breakpoint exception
962 * This function will generate a breakpoint exception. It is used at the
963 * beginning of a program to sync up with a debugger and can be used
964 * otherwise as a quick means to stop program execution and "break" into
967 void kgdb_breakpoint(void)
969 atomic_inc(&kgdb_setting_breakpoint);
970 wmb(); /* Sync point before breakpoint */
971 arch_kgdb_breakpoint();
972 wmb(); /* Sync point after breakpoint */
973 atomic_dec(&kgdb_setting_breakpoint);
975 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
977 static int __init opt_kgdb_wait(char *str)
981 kdb_init(KDB_INIT_EARLY);
982 if (kgdb_io_module_registered)
983 kgdb_initial_breakpoint();
988 early_param("kgdbwait", opt_kgdb_wait);