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.
31 #define pr_fmt(fmt) "KGDB: " fmt
33 #include <linux/pid_namespace.h>
34 #include <linux/clocksource.h>
35 #include <linux/serial_core.h>
36 #include <linux/interrupt.h>
37 #include <linux/spinlock.h>
38 #include <linux/console.h>
39 #include <linux/threads.h>
40 #include <linux/uaccess.h>
41 #include <linux/kernel.h>
42 #include <linux/module.h>
43 #include <linux/ptrace.h>
44 #include <linux/string.h>
45 #include <linux/delay.h>
46 #include <linux/sched.h>
47 #include <linux/sysrq.h>
48 #include <linux/reboot.h>
49 #include <linux/init.h>
50 #include <linux/kgdb.h>
51 #include <linux/kdb.h>
52 #include <linux/nmi.h>
53 #include <linux/pid.h>
54 #include <linux/smp.h>
56 #include <linux/vmacache.h>
57 #include <linux/rcupdate.h>
58 #include <linux/irq.h>
60 #include <asm/cacheflush.h>
61 #include <asm/byteorder.h>
62 #include <linux/atomic.h>
64 #include "debug_core.h"
66 static int kgdb_break_asap;
68 struct debuggerinfo_struct kgdb_info[NR_CPUS];
71 * kgdb_connected - Is a host GDB connected to us?
74 EXPORT_SYMBOL_GPL(kgdb_connected);
76 /* All the KGDB handlers are installed */
77 int kgdb_io_module_registered;
79 /* Guard for recursive entry */
80 static int exception_level;
82 struct kgdb_io *dbg_io_ops;
83 static DEFINE_SPINLOCK(kgdb_registration_lock);
85 /* Action for the reboot notifiter, a global allow kdb to change it */
86 static int kgdbreboot;
87 /* kgdb console driver is loaded */
88 static int kgdb_con_registered;
89 /* determine if kgdb console output should be used */
90 static int kgdb_use_con;
91 /* Flag for alternate operations for early debugging */
92 bool dbg_is_early = true;
93 /* Next cpu to become the master debug core */
96 /* Use kdb or gdbserver mode */
99 static int __init opt_kgdb_con(char *str)
105 early_param("kgdbcon", opt_kgdb_con);
107 module_param(kgdb_use_con, int, 0644);
108 module_param(kgdbreboot, int, 0644);
111 * Holds information about breakpoints in a kernel. These breakpoints are
112 * added and removed by gdb.
114 static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
115 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
119 * The CPU# of the active CPU, or -1 if none:
121 atomic_t kgdb_active = ATOMIC_INIT(-1);
122 EXPORT_SYMBOL_GPL(kgdb_active);
123 static DEFINE_RAW_SPINLOCK(dbg_master_lock);
124 static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
127 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
128 * bootup code (which might not have percpu set up yet):
130 static atomic_t masters_in_kgdb;
131 static atomic_t slaves_in_kgdb;
132 static atomic_t kgdb_break_tasklet_var;
133 atomic_t kgdb_setting_breakpoint;
135 struct task_struct *kgdb_usethread;
136 struct task_struct *kgdb_contthread;
138 int kgdb_single_step;
139 static pid_t kgdb_sstep_pid;
141 /* to keep track of the CPU which is doing the single stepping*/
142 atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
145 * If you are debugging a problem where roundup (the collection of
146 * all other CPUs) is a problem [this should be extremely rare],
147 * then use the nokgdbroundup option to avoid roundup. In that case
148 * the other CPUs might interfere with your debugging context, so
149 * use this with care:
151 static int kgdb_do_roundup = 1;
153 static int __init opt_nokgdbroundup(char *str)
160 early_param("nokgdbroundup", opt_nokgdbroundup);
163 * Finally, some KGDB code :-)
167 * Weak aliases for breakpoint management,
168 * can be overriden by architectures when needed:
170 int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
174 err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
178 err = probe_kernel_write((char *)bpt->bpt_addr,
179 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
183 int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
185 return probe_kernel_write((char *)bpt->bpt_addr,
186 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
189 int __weak kgdb_validate_break_address(unsigned long addr)
191 struct kgdb_bkpt tmp;
193 /* Validate setting the breakpoint and then removing it. If the
194 * remove fails, the kernel needs to emit a bad message because we
195 * are deep trouble not being able to put things back the way we
199 err = kgdb_arch_set_breakpoint(&tmp);
202 err = kgdb_arch_remove_breakpoint(&tmp);
204 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
209 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
211 return instruction_pointer(regs);
214 int __weak kgdb_arch_init(void)
219 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
227 * Default (weak) implementation for kgdb_roundup_cpus
230 static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd);
232 void __weak kgdb_call_nmi_hook(void *ignored)
235 * NOTE: get_irq_regs() is supposed to get the registers from
236 * before the IPI interrupt happened and so is supposed to
237 * show where the processor was. In some situations it's
238 * possible we might be called without an IPI, so it might be
239 * safer to figure out how to make kgdb_breakpoint() work
242 kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
245 void __weak kgdb_roundup_cpus(void)
247 call_single_data_t *csd;
248 int this_cpu = raw_smp_processor_id();
252 for_each_online_cpu(cpu) {
253 /* No need to roundup ourselves */
257 csd = &per_cpu(kgdb_roundup_csd, cpu);
260 * If it didn't round up last time, don't try again
261 * since smp_call_function_single_async() will block.
263 * If rounding_up is false then we know that the
264 * previous call must have at least started and that
265 * means smp_call_function_single_async() won't block.
267 if (kgdb_info[cpu].rounding_up)
269 kgdb_info[cpu].rounding_up = true;
271 csd->func = kgdb_call_nmi_hook;
272 ret = smp_call_function_single_async(cpu, csd);
274 kgdb_info[cpu].rounding_up = false;
281 * Some architectures need cache flushes when we set/clear a
284 static void kgdb_flush_swbreak_addr(unsigned long addr)
286 if (!CACHE_FLUSH_IS_SAFE)
292 for (i = 0; i < VMACACHE_SIZE; i++) {
293 if (!current->vmacache.vmas[i])
295 flush_cache_range(current->vmacache.vmas[i],
296 addr, addr + BREAK_INSTR_SIZE);
300 /* Force flush instruction cache if it was outside the mm */
301 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
305 * SW breakpoint management:
307 int dbg_activate_sw_breakpoints(void)
313 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
314 if (kgdb_break[i].state != BP_SET)
317 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
320 pr_info("BP install failed: %lx\n",
321 kgdb_break[i].bpt_addr);
325 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
326 kgdb_break[i].state = BP_ACTIVE;
331 int dbg_set_sw_break(unsigned long addr)
333 int err = kgdb_validate_break_address(addr);
340 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
341 if ((kgdb_break[i].state == BP_SET) &&
342 (kgdb_break[i].bpt_addr == addr))
345 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
346 if (kgdb_break[i].state == BP_REMOVED &&
347 kgdb_break[i].bpt_addr == addr) {
354 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
355 if (kgdb_break[i].state == BP_UNDEFINED) {
365 kgdb_break[breakno].state = BP_SET;
366 kgdb_break[breakno].type = BP_BREAKPOINT;
367 kgdb_break[breakno].bpt_addr = addr;
372 int dbg_deactivate_sw_breakpoints(void)
378 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
379 if (kgdb_break[i].state != BP_ACTIVE)
381 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
383 pr_info("BP remove failed: %lx\n",
384 kgdb_break[i].bpt_addr);
388 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
389 kgdb_break[i].state = BP_SET;
394 int dbg_remove_sw_break(unsigned long addr)
398 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
399 if ((kgdb_break[i].state == BP_SET) &&
400 (kgdb_break[i].bpt_addr == addr)) {
401 kgdb_break[i].state = BP_REMOVED;
408 int kgdb_isremovedbreak(unsigned long addr)
412 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
413 if ((kgdb_break[i].state == BP_REMOVED) &&
414 (kgdb_break[i].bpt_addr == addr))
420 int dbg_remove_all_break(void)
425 /* Clear memory breakpoints. */
426 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
427 if (kgdb_break[i].state != BP_ACTIVE)
429 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
431 pr_err("breakpoint remove failed: %lx\n",
432 kgdb_break[i].bpt_addr);
434 kgdb_break[i].state = BP_UNDEFINED;
437 /* Clear hardware breakpoints. */
438 if (arch_kgdb_ops.remove_all_hw_break)
439 arch_kgdb_ops.remove_all_hw_break();
445 * Return true if there is a valid kgdb I/O module. Also if no
446 * debugger is attached a message can be printed to the console about
447 * waiting for the debugger to attach.
449 * The print_wait argument is only to be true when called from inside
450 * the core kgdb_handle_exception, because it will wait for the
451 * debugger to attach.
453 static int kgdb_io_ready(int print_wait)
459 if (atomic_read(&kgdb_setting_breakpoint))
462 #ifdef CONFIG_KGDB_KDB
464 pr_crit("waiting... or $3#33 for KDB\n");
466 pr_crit("Waiting for remote debugger\n");
472 static int kgdb_reenter_check(struct kgdb_state *ks)
476 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
479 /* Panic on recursive debugger calls: */
481 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
482 dbg_deactivate_sw_breakpoints();
485 * If the break point removed ok at the place exception
486 * occurred, try to recover and print a warning to the end
487 * user because the user planted a breakpoint in a place that
488 * KGDB needs in order to function.
490 if (dbg_remove_sw_break(addr) == 0) {
492 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
493 dbg_activate_sw_breakpoints();
494 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
499 dbg_remove_all_break();
500 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
502 if (exception_level > 1) {
504 panic("Recursive entry to debugger");
507 pr_crit("re-enter exception: ALL breakpoints killed\n");
508 #ifdef CONFIG_KGDB_KDB
509 /* Allow kdb to debug itself one level */
513 panic("Recursive entry to debugger");
518 static void dbg_touch_watchdogs(void)
520 touch_softlockup_watchdog_sync();
521 clocksource_touch_watchdog();
522 rcu_cpu_stall_reset();
525 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
529 int sstep_tries = 100;
533 int online_cpus = num_online_cpus();
536 kgdb_info[ks->cpu].enter_kgdb++;
537 kgdb_info[ks->cpu].exception_state |= exception_state;
539 if (exception_state == DCPU_WANT_MASTER)
540 atomic_inc(&masters_in_kgdb);
542 atomic_inc(&slaves_in_kgdb);
544 if (arch_kgdb_ops.disable_hw_break)
545 arch_kgdb_ops.disable_hw_break(regs);
549 * Interrupts will be restored by the 'trap return' code, except when
552 local_irq_save(flags);
555 kgdb_info[cpu].debuggerinfo = regs;
556 kgdb_info[cpu].task = current;
557 kgdb_info[cpu].ret_state = 0;
558 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
560 /* Make sure the above info reaches the primary CPU */
563 if (exception_level == 1) {
564 if (raw_spin_trylock(&dbg_master_lock))
565 atomic_xchg(&kgdb_active, cpu);
566 goto cpu_master_loop;
570 * CPU will loop if it is a slave or request to become a kgdb
571 * master cpu and acquire the kgdb_active lock:
575 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
576 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
577 goto cpu_master_loop;
578 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
579 if (raw_spin_trylock(&dbg_master_lock)) {
580 atomic_xchg(&kgdb_active, cpu);
583 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
584 if (!raw_spin_is_locked(&dbg_slave_lock))
588 /* Return to normal operation by executing any
589 * hw breakpoint fixup.
591 if (arch_kgdb_ops.correct_hw_break)
592 arch_kgdb_ops.correct_hw_break();
595 kgdb_info[cpu].exception_state &=
596 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
597 kgdb_info[cpu].enter_kgdb--;
598 smp_mb__before_atomic();
599 atomic_dec(&slaves_in_kgdb);
600 dbg_touch_watchdogs();
601 local_irq_restore(flags);
608 * For single stepping, try to only enter on the processor
609 * that was single stepping. To guard against a deadlock, the
610 * kernel will only try for the value of sstep_tries before
611 * giving up and continuing on.
613 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
614 (kgdb_info[cpu].task &&
615 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
616 atomic_set(&kgdb_active, -1);
617 raw_spin_unlock(&dbg_master_lock);
618 dbg_touch_watchdogs();
619 local_irq_restore(flags);
624 if (!kgdb_io_ready(1)) {
625 kgdb_info[cpu].ret_state = 1;
626 goto kgdb_restore; /* No I/O connection, resume the system */
630 * Don't enter if we have hit a removed breakpoint.
632 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
635 /* Call the I/O driver's pre_exception routine */
636 if (dbg_io_ops->pre_exception)
637 dbg_io_ops->pre_exception();
640 * Get the passive CPU lock which will hold all the non-primary
641 * CPU in a spin state while the debugger is active
643 if (!kgdb_single_step)
644 raw_spin_lock(&dbg_slave_lock);
647 /* If send_ready set, slaves are already waiting */
649 atomic_set(ks->send_ready, 1);
651 /* Signal the other CPUs to enter kgdb_wait() */
652 else if ((!kgdb_single_step) && kgdb_do_roundup)
657 * Wait for the other CPUs to be notified and be waiting for us:
659 time_left = MSEC_PER_SEC;
660 while (kgdb_do_roundup && --time_left &&
661 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
665 pr_crit("Timed out waiting for secondary CPUs.\n");
668 * At this point the primary processor is completely
669 * in the debugger and all secondary CPUs are quiescent
671 dbg_deactivate_sw_breakpoints();
672 kgdb_single_step = 0;
673 kgdb_contthread = current;
675 trace_on = tracing_is_on();
683 error = kdb_stub(ks);
688 error = gdb_serial_stub(ks);
691 if (error == DBG_PASS_EVENT) {
692 dbg_kdb_mode = !dbg_kdb_mode;
693 } else if (error == DBG_SWITCH_CPU_EVENT) {
694 kgdb_info[dbg_switch_cpu].exception_state |=
698 kgdb_info[cpu].ret_state = error;
703 /* Call the I/O driver's post_exception routine */
704 if (dbg_io_ops->post_exception)
705 dbg_io_ops->post_exception();
707 if (!kgdb_single_step) {
708 raw_spin_unlock(&dbg_slave_lock);
709 /* Wait till all the CPUs have quit from the debugger. */
710 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
715 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
716 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
717 if (kgdb_info[sstep_cpu].task)
718 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
722 if (arch_kgdb_ops.correct_hw_break)
723 arch_kgdb_ops.correct_hw_break();
727 kgdb_info[cpu].exception_state &=
728 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
729 kgdb_info[cpu].enter_kgdb--;
730 smp_mb__before_atomic();
731 atomic_dec(&masters_in_kgdb);
732 /* Free kgdb_active */
733 atomic_set(&kgdb_active, -1);
734 raw_spin_unlock(&dbg_master_lock);
735 dbg_touch_watchdogs();
736 local_irq_restore(flags);
738 return kgdb_info[cpu].ret_state;
742 * kgdb_handle_exception() - main entry point from a kernel exception
745 * interface locks, if any (begin_session)
746 * kgdb lock (kgdb_active)
749 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
751 struct kgdb_state kgdb_var;
752 struct kgdb_state *ks = &kgdb_var;
755 if (arch_kgdb_ops.enable_nmi)
756 arch_kgdb_ops.enable_nmi(0);
758 * Avoid entering the debugger if we were triggered due to an oops
759 * but panic_timeout indicates the system should automatically
760 * reboot on panic. We don't want to get stuck waiting for input
761 * on such systems, especially if its "just" an oops.
763 if (signo != SIGTRAP && panic_timeout)
766 memset(ks, 0, sizeof(struct kgdb_state));
767 ks->cpu = raw_smp_processor_id();
768 ks->ex_vector = evector;
770 ks->err_code = ecode;
771 ks->linux_regs = regs;
773 if (kgdb_reenter_check(ks))
774 goto out; /* Ouch, double exception ! */
775 if (kgdb_info[ks->cpu].enter_kgdb != 0)
778 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
780 if (arch_kgdb_ops.enable_nmi)
781 arch_kgdb_ops.enable_nmi(1);
786 * GDB places a breakpoint at this function to know dynamically
787 * loaded objects. It's not defined static so that only one instance with this
788 * name exists in the kernel.
791 static int module_event(struct notifier_block *self, unsigned long val,
797 static struct notifier_block dbg_module_load_nb = {
798 .notifier_call = module_event,
801 int kgdb_nmicallback(int cpu, void *regs)
804 struct kgdb_state kgdb_var;
805 struct kgdb_state *ks = &kgdb_var;
807 kgdb_info[cpu].rounding_up = false;
809 memset(ks, 0, sizeof(struct kgdb_state));
811 ks->linux_regs = regs;
813 if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
814 raw_spin_is_locked(&dbg_master_lock)) {
815 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
822 int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
823 atomic_t *send_ready)
826 if (!kgdb_io_ready(0) || !send_ready)
829 if (kgdb_info[cpu].enter_kgdb == 0) {
830 struct kgdb_state kgdb_var;
831 struct kgdb_state *ks = &kgdb_var;
833 memset(ks, 0, sizeof(struct kgdb_state));
835 ks->ex_vector = trapnr;
837 ks->err_code = err_code;
838 ks->linux_regs = regs;
839 ks->send_ready = send_ready;
840 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
847 static void kgdb_console_write(struct console *co, const char *s,
852 /* If we're debugging, or KGDB has not connected, don't try
854 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
857 local_irq_save(flags);
858 gdbstub_msg_write(s, count);
859 local_irq_restore(flags);
862 static struct console kgdbcons = {
864 .write = kgdb_console_write,
865 .flags = CON_PRINTBUFFER | CON_ENABLED,
869 #ifdef CONFIG_MAGIC_SYSRQ
870 static void sysrq_handle_dbg(int key)
873 pr_crit("ERROR: No KGDB I/O module available\n");
876 if (!kgdb_connected) {
877 #ifdef CONFIG_KGDB_KDB
879 pr_crit("KGDB or $3#33 for KDB\n");
881 pr_crit("Entering KGDB\n");
888 static struct sysrq_key_op sysrq_dbg_op = {
889 .handler = sysrq_handle_dbg,
890 .help_msg = "debug(g)",
891 .action_msg = "DEBUG",
895 static int kgdb_panic_event(struct notifier_block *self,
900 * Avoid entering the debugger if we were triggered due to a panic
901 * We don't want to get stuck waiting for input from user in such case.
902 * panic_timeout indicates the system should automatically
909 kdb_printf("PANIC: %s\n", (char *)data);
914 static struct notifier_block kgdb_panic_event_nb = {
915 .notifier_call = kgdb_panic_event,
919 void __weak kgdb_arch_late(void)
923 void __init dbg_late_init(void)
925 dbg_is_early = false;
926 if (kgdb_io_module_registered)
928 kdb_init(KDB_INIT_FULL);
932 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
935 * Take the following action on reboot notify depending on value:
936 * 1 == Enter debugger
937 * 0 == [the default] detatch debug client
938 * -1 == Do nothing... and use this until the board resets
940 switch (kgdbreboot) {
952 static struct notifier_block dbg_reboot_notifier = {
953 .notifier_call = dbg_notify_reboot,
958 static void kgdb_register_callbacks(void)
960 if (!kgdb_io_module_registered) {
961 kgdb_io_module_registered = 1;
965 register_module_notifier(&dbg_module_load_nb);
966 register_reboot_notifier(&dbg_reboot_notifier);
967 atomic_notifier_chain_register(&panic_notifier_list,
968 &kgdb_panic_event_nb);
969 #ifdef CONFIG_MAGIC_SYSRQ
970 register_sysrq_key('g', &sysrq_dbg_op);
972 if (kgdb_use_con && !kgdb_con_registered) {
973 register_console(&kgdbcons);
974 kgdb_con_registered = 1;
979 static void kgdb_unregister_callbacks(void)
982 * When this routine is called KGDB should unregister from the
983 * panic handler and clean up, making sure it is not handling any
984 * break exceptions at the time.
986 if (kgdb_io_module_registered) {
987 kgdb_io_module_registered = 0;
988 unregister_reboot_notifier(&dbg_reboot_notifier);
989 unregister_module_notifier(&dbg_module_load_nb);
990 atomic_notifier_chain_unregister(&panic_notifier_list,
991 &kgdb_panic_event_nb);
993 #ifdef CONFIG_MAGIC_SYSRQ
994 unregister_sysrq_key('g', &sysrq_dbg_op);
996 if (kgdb_con_registered) {
997 unregister_console(&kgdbcons);
998 kgdb_con_registered = 0;
1004 * There are times a tasklet needs to be used vs a compiled in
1005 * break point so as to cause an exception outside a kgdb I/O module,
1006 * such as is the case with kgdboe, where calling a breakpoint in the
1007 * I/O driver itself would be fatal.
1009 static void kgdb_tasklet_bpt(unsigned long ing)
1012 atomic_set(&kgdb_break_tasklet_var, 0);
1015 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
1017 void kgdb_schedule_breakpoint(void)
1019 if (atomic_read(&kgdb_break_tasklet_var) ||
1020 atomic_read(&kgdb_active) != -1 ||
1021 atomic_read(&kgdb_setting_breakpoint))
1023 atomic_inc(&kgdb_break_tasklet_var);
1024 tasklet_schedule(&kgdb_tasklet_breakpoint);
1026 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
1028 static void kgdb_initial_breakpoint(void)
1030 kgdb_break_asap = 0;
1032 pr_crit("Waiting for connection from remote gdb...\n");
1037 * kgdb_register_io_module - register KGDB IO module
1038 * @new_dbg_io_ops: the io ops vector
1040 * Register it with the KGDB core.
1042 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
1046 spin_lock(&kgdb_registration_lock);
1049 spin_unlock(&kgdb_registration_lock);
1051 pr_err("Another I/O driver is already registered with KGDB\n");
1055 if (new_dbg_io_ops->init) {
1056 err = new_dbg_io_ops->init();
1058 spin_unlock(&kgdb_registration_lock);
1063 dbg_io_ops = new_dbg_io_ops;
1065 spin_unlock(&kgdb_registration_lock);
1067 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1070 kgdb_register_callbacks();
1072 if (kgdb_break_asap)
1073 kgdb_initial_breakpoint();
1077 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1080 * kkgdb_unregister_io_module - unregister KGDB IO module
1081 * @old_dbg_io_ops: the io ops vector
1083 * Unregister it with the KGDB core.
1085 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1087 BUG_ON(kgdb_connected);
1090 * KGDB is no longer able to communicate out, so
1091 * unregister our callbacks and reset state.
1093 kgdb_unregister_callbacks();
1095 spin_lock(&kgdb_registration_lock);
1097 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1100 spin_unlock(&kgdb_registration_lock);
1102 pr_info("Unregistered I/O driver %s, debugger disabled\n",
1103 old_dbg_io_ops->name);
1105 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1107 int dbg_io_get_char(void)
1109 int ret = dbg_io_ops->read_char();
1110 if (ret == NO_POLL_CHAR)
1120 * kgdb_breakpoint - generate breakpoint exception
1122 * This function will generate a breakpoint exception. It is used at the
1123 * beginning of a program to sync up with a debugger and can be used
1124 * otherwise as a quick means to stop program execution and "break" into
1127 noinline void kgdb_breakpoint(void)
1129 atomic_inc(&kgdb_setting_breakpoint);
1130 wmb(); /* Sync point before breakpoint */
1131 arch_kgdb_breakpoint();
1132 wmb(); /* Sync point after breakpoint */
1133 atomic_dec(&kgdb_setting_breakpoint);
1135 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1137 static int __init opt_kgdb_wait(char *str)
1139 kgdb_break_asap = 1;
1141 kdb_init(KDB_INIT_EARLY);
1142 if (kgdb_io_module_registered)
1143 kgdb_initial_breakpoint();
1148 early_param("kgdbwait", opt_kgdb_wait);