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@suse.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 /* Next cpu to become the master debug core */
84 /* Use kdb or gdbserver mode */
87 static int __init opt_kgdb_con(char *str)
93 early_param("kgdbcon", opt_kgdb_con);
95 module_param(kgdb_use_con, int, 0644);
98 * Holds information about breakpoints in a kernel. These breakpoints are
99 * added and removed by gdb.
101 static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
102 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
106 * The CPU# of the active CPU, or -1 if none:
108 atomic_t kgdb_active = ATOMIC_INIT(-1);
109 EXPORT_SYMBOL_GPL(kgdb_active);
112 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
113 * bootup code (which might not have percpu set up yet):
115 static atomic_t passive_cpu_wait[NR_CPUS];
116 static atomic_t cpu_in_kgdb[NR_CPUS];
117 atomic_t kgdb_setting_breakpoint;
119 struct task_struct *kgdb_usethread;
120 struct task_struct *kgdb_contthread;
122 int kgdb_single_step;
123 static pid_t kgdb_sstep_pid;
125 /* to keep track of the CPU which is doing the single stepping*/
126 atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
129 * If you are debugging a problem where roundup (the collection of
130 * all other CPUs) is a problem [this should be extremely rare],
131 * then use the nokgdbroundup option to avoid roundup. In that case
132 * the other CPUs might interfere with your debugging context, so
133 * use this with care:
135 static int kgdb_do_roundup = 1;
137 static int __init opt_nokgdbroundup(char *str)
144 early_param("nokgdbroundup", opt_nokgdbroundup);
147 * Finally, some KGDB code :-)
151 * Weak aliases for breakpoint management,
152 * can be overriden by architectures when needed:
154 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
158 err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
162 return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
166 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
168 return probe_kernel_write((char *)addr,
169 (char *)bundle, BREAK_INSTR_SIZE);
172 int __weak kgdb_validate_break_address(unsigned long addr)
174 char tmp_variable[BREAK_INSTR_SIZE];
176 /* Validate setting the breakpoint and then removing it. In the
177 * remove fails, the kernel needs to emit a bad message because we
178 * are deep trouble not being able to put things back the way we
181 err = kgdb_arch_set_breakpoint(addr, tmp_variable);
184 err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
186 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
187 "memory destroyed at: %lx", addr);
191 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
193 return instruction_pointer(regs);
196 int __weak kgdb_arch_init(void)
201 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
207 * kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
208 * @regs: Current &struct pt_regs.
210 * This function will be called if the particular architecture must
211 * disable hardware debugging while it is processing gdb packets or
212 * handling exception.
214 void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
219 * Some architectures need cache flushes when we set/clear a
222 static void kgdb_flush_swbreak_addr(unsigned long addr)
224 if (!CACHE_FLUSH_IS_SAFE)
227 if (current->mm && current->mm->mmap_cache) {
228 flush_cache_range(current->mm->mmap_cache,
229 addr, addr + BREAK_INSTR_SIZE);
231 /* Force flush instruction cache if it was outside the mm */
232 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
236 * SW breakpoint management:
238 int dbg_activate_sw_breakpoints(void)
245 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
246 if (kgdb_break[i].state != BP_SET)
249 addr = kgdb_break[i].bpt_addr;
250 error = kgdb_arch_set_breakpoint(addr,
251 kgdb_break[i].saved_instr);
254 printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
258 kgdb_flush_swbreak_addr(addr);
259 kgdb_break[i].state = BP_ACTIVE;
264 int dbg_set_sw_break(unsigned long addr)
266 int err = kgdb_validate_break_address(addr);
273 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
274 if ((kgdb_break[i].state == BP_SET) &&
275 (kgdb_break[i].bpt_addr == addr))
278 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
279 if (kgdb_break[i].state == BP_REMOVED &&
280 kgdb_break[i].bpt_addr == addr) {
287 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
288 if (kgdb_break[i].state == BP_UNDEFINED) {
298 kgdb_break[breakno].state = BP_SET;
299 kgdb_break[breakno].type = BP_BREAKPOINT;
300 kgdb_break[breakno].bpt_addr = addr;
305 int dbg_deactivate_sw_breakpoints(void)
312 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
313 if (kgdb_break[i].state != BP_ACTIVE)
315 addr = kgdb_break[i].bpt_addr;
316 error = kgdb_arch_remove_breakpoint(addr,
317 kgdb_break[i].saved_instr);
319 printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
323 kgdb_flush_swbreak_addr(addr);
324 kgdb_break[i].state = BP_SET;
329 int dbg_remove_sw_break(unsigned long addr)
333 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
334 if ((kgdb_break[i].state == BP_SET) &&
335 (kgdb_break[i].bpt_addr == addr)) {
336 kgdb_break[i].state = BP_REMOVED;
343 int kgdb_isremovedbreak(unsigned long addr)
347 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
348 if ((kgdb_break[i].state == BP_REMOVED) &&
349 (kgdb_break[i].bpt_addr == addr))
355 int dbg_remove_all_break(void)
361 /* Clear memory breakpoints. */
362 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
363 if (kgdb_break[i].state != BP_ACTIVE)
365 addr = kgdb_break[i].bpt_addr;
366 error = kgdb_arch_remove_breakpoint(addr,
367 kgdb_break[i].saved_instr);
369 printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
372 kgdb_break[i].state = BP_UNDEFINED;
375 /* Clear hardware breakpoints. */
376 if (arch_kgdb_ops.remove_all_hw_break)
377 arch_kgdb_ops.remove_all_hw_break();
383 * Return true if there is a valid kgdb I/O module. Also if no
384 * debugger is attached a message can be printed to the console about
385 * waiting for the debugger to attach.
387 * The print_wait argument is only to be true when called from inside
388 * the core kgdb_handle_exception, because it will wait for the
389 * debugger to attach.
391 static int kgdb_io_ready(int print_wait)
397 if (atomic_read(&kgdb_setting_breakpoint))
400 #ifdef CONFIG_KGDB_KDB
402 printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
404 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
410 static int kgdb_reenter_check(struct kgdb_state *ks)
414 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
417 /* Panic on recursive debugger calls: */
419 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
420 dbg_deactivate_sw_breakpoints();
423 * If the break point removed ok at the place exception
424 * occurred, try to recover and print a warning to the end
425 * user because the user planted a breakpoint in a place that
426 * KGDB needs in order to function.
428 if (dbg_remove_sw_break(addr) == 0) {
430 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
431 dbg_activate_sw_breakpoints();
432 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
438 dbg_remove_all_break();
439 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
441 if (exception_level > 1) {
443 panic("Recursive entry to debugger");
446 printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
448 panic("Recursive entry to debugger");
453 static void dbg_cpu_switch(int cpu, int next_cpu)
455 /* Mark the cpu we are switching away from as a slave when it
456 * holds the kgdb_active token. This must be done so that the
457 * that all the cpus wait in for the debug core will not enter
458 * again as the master. */
459 if (cpu == atomic_read(&kgdb_active)) {
460 kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
461 kgdb_info[cpu].exception_state &= ~DCPU_WANT_MASTER;
463 kgdb_info[next_cpu].exception_state |= DCPU_NEXT_MASTER;
466 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
469 int sstep_tries = 100;
475 * Interrupts will be restored by the 'trap return' code, except when
478 local_irq_save(flags);
481 kgdb_info[cpu].debuggerinfo = regs;
482 kgdb_info[cpu].task = current;
483 kgdb_info[cpu].ret_state = 0;
484 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
486 * Make sure the above info reaches the primary CPU before
487 * our cpu_in_kgdb[] flag setting does:
489 atomic_inc(&cpu_in_kgdb[cpu]);
492 * CPU will loop if it is a slave or request to become a kgdb
493 * master cpu and acquire the kgdb_active lock:
497 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
498 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
499 goto cpu_master_loop;
500 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
501 if (atomic_cmpxchg(&kgdb_active, -1, cpu) == cpu)
503 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
504 if (!atomic_read(&passive_cpu_wait[cpu]))
508 /* Return to normal operation by executing any
509 * hw breakpoint fixup.
511 if (arch_kgdb_ops.correct_hw_break)
512 arch_kgdb_ops.correct_hw_break();
515 atomic_dec(&cpu_in_kgdb[cpu]);
516 touch_softlockup_watchdog_sync();
517 clocksource_touch_watchdog();
518 local_irq_restore(flags);
525 * For single stepping, try to only enter on the processor
526 * that was single stepping. To gaurd against a deadlock, the
527 * kernel will only try for the value of sstep_tries before
528 * giving up and continuing on.
530 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
531 (kgdb_info[cpu].task &&
532 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
533 atomic_set(&kgdb_active, -1);
534 touch_softlockup_watchdog_sync();
535 clocksource_touch_watchdog();
536 local_irq_restore(flags);
541 if (!kgdb_io_ready(1)) {
542 kgdb_info[cpu].ret_state = 1;
543 goto kgdb_restore; /* No I/O connection, resume the system */
547 * Don't enter if we have hit a removed breakpoint.
549 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
552 /* Call the I/O driver's pre_exception routine */
553 if (dbg_io_ops->pre_exception)
554 dbg_io_ops->pre_exception();
556 kgdb_disable_hw_debug(ks->linux_regs);
559 * Get the passive CPU lock which will hold all the non-primary
560 * CPU in a spin state while the debugger is active
562 if (!kgdb_single_step) {
563 for (i = 0; i < NR_CPUS; i++)
564 atomic_inc(&passive_cpu_wait[i]);
568 /* Signal the other CPUs to enter kgdb_wait() */
569 if ((!kgdb_single_step) && kgdb_do_roundup)
570 kgdb_roundup_cpus(flags);
574 * Wait for the other CPUs to be notified and be waiting for us:
576 for_each_online_cpu(i) {
577 while (kgdb_do_roundup && !atomic_read(&cpu_in_kgdb[i]))
582 * At this point the primary processor is completely
583 * in the debugger and all secondary CPUs are quiescent
585 dbg_deactivate_sw_breakpoints();
586 kgdb_single_step = 0;
587 kgdb_contthread = current;
589 trace_on = tracing_is_on();
597 error = kdb_stub(ks);
599 error = gdb_serial_stub(ks);
602 if (error == DBG_PASS_EVENT) {
603 dbg_kdb_mode = !dbg_kdb_mode;
605 } else if (error == DBG_SWITCH_CPU_EVENT) {
606 dbg_cpu_switch(cpu, dbg_switch_cpu);
609 kgdb_info[cpu].ret_state = error;
614 /* Call the I/O driver's post_exception routine */
615 if (dbg_io_ops->post_exception)
616 dbg_io_ops->post_exception();
618 atomic_dec(&cpu_in_kgdb[ks->cpu]);
620 if (!kgdb_single_step) {
621 for (i = NR_CPUS-1; i >= 0; i--)
622 atomic_dec(&passive_cpu_wait[i]);
624 * Wait till all the CPUs have quit from the debugger,
625 * but allow a CPU that hit an exception and is
626 * waiting to become the master to remain in the debug
629 for_each_online_cpu(i) {
630 while (kgdb_do_roundup &&
631 atomic_read(&cpu_in_kgdb[i]) &&
632 !(kgdb_info[i].exception_state &
639 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
640 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
641 if (kgdb_info[sstep_cpu].task)
642 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
648 /* Free kgdb_active */
649 atomic_set(&kgdb_active, -1);
650 touch_softlockup_watchdog_sync();
651 clocksource_touch_watchdog();
652 local_irq_restore(flags);
654 return kgdb_info[cpu].ret_state;
658 * kgdb_handle_exception() - main entry point from a kernel exception
661 * interface locks, if any (begin_session)
662 * kgdb lock (kgdb_active)
665 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
667 struct kgdb_state kgdb_var;
668 struct kgdb_state *ks = &kgdb_var;
671 ks->cpu = raw_smp_processor_id();
672 ks->ex_vector = evector;
674 ks->err_code = ecode;
675 ks->kgdb_usethreadid = 0;
676 ks->linux_regs = regs;
678 if (kgdb_reenter_check(ks))
679 return 0; /* Ouch, double exception ! */
680 kgdb_info[ks->cpu].exception_state |= DCPU_WANT_MASTER;
681 ret = kgdb_cpu_enter(ks, regs);
682 kgdb_info[ks->cpu].exception_state &= ~(DCPU_WANT_MASTER |
687 int kgdb_nmicallback(int cpu, void *regs)
690 struct kgdb_state kgdb_var;
691 struct kgdb_state *ks = &kgdb_var;
693 memset(ks, 0, sizeof(struct kgdb_state));
695 ks->linux_regs = regs;
697 if (!atomic_read(&cpu_in_kgdb[cpu]) &&
698 atomic_read(&kgdb_active) != -1 &&
699 atomic_read(&kgdb_active) != cpu) {
700 kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
701 kgdb_cpu_enter(ks, regs);
702 kgdb_info[cpu].exception_state &= ~DCPU_IS_SLAVE;
709 static void kgdb_console_write(struct console *co, const char *s,
714 /* If we're debugging, or KGDB has not connected, don't try
716 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
719 local_irq_save(flags);
720 gdbstub_msg_write(s, count);
721 local_irq_restore(flags);
724 static struct console kgdbcons = {
726 .write = kgdb_console_write,
727 .flags = CON_PRINTBUFFER | CON_ENABLED,
731 #ifdef CONFIG_MAGIC_SYSRQ
732 static void sysrq_handle_dbg(int key, struct tty_struct *tty)
735 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
738 if (!kgdb_connected) {
739 #ifdef CONFIG_KGDB_KDB
741 printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
743 printk(KERN_CRIT "Entering KGDB\n");
750 static struct sysrq_key_op sysrq_dbg_op = {
751 .handler = sysrq_handle_dbg,
752 .help_msg = "debug(G)",
753 .action_msg = "DEBUG",
757 static void kgdb_register_callbacks(void)
759 if (!kgdb_io_module_registered) {
760 kgdb_io_module_registered = 1;
762 #ifdef CONFIG_MAGIC_SYSRQ
763 register_sysrq_key('g', &sysrq_dbg_op);
765 if (kgdb_use_con && !kgdb_con_registered) {
766 register_console(&kgdbcons);
767 kgdb_con_registered = 1;
772 static void kgdb_unregister_callbacks(void)
775 * When this routine is called KGDB should unregister from the
776 * panic handler and clean up, making sure it is not handling any
777 * break exceptions at the time.
779 if (kgdb_io_module_registered) {
780 kgdb_io_module_registered = 0;
782 #ifdef CONFIG_MAGIC_SYSRQ
783 unregister_sysrq_key('g', &sysrq_dbg_op);
785 if (kgdb_con_registered) {
786 unregister_console(&kgdbcons);
787 kgdb_con_registered = 0;
792 static void kgdb_initial_breakpoint(void)
796 printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
801 * kgdb_register_io_module - register KGDB IO module
802 * @new_dbg_io_ops: the io ops vector
804 * Register it with the KGDB core.
806 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
810 spin_lock(&kgdb_registration_lock);
813 spin_unlock(&kgdb_registration_lock);
815 printk(KERN_ERR "kgdb: Another I/O driver is already "
816 "registered with KGDB.\n");
820 if (new_dbg_io_ops->init) {
821 err = new_dbg_io_ops->init();
823 spin_unlock(&kgdb_registration_lock);
828 dbg_io_ops = new_dbg_io_ops;
830 spin_unlock(&kgdb_registration_lock);
832 printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
833 new_dbg_io_ops->name);
836 kgdb_register_callbacks();
839 kgdb_initial_breakpoint();
843 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
846 * kkgdb_unregister_io_module - unregister KGDB IO module
847 * @old_dbg_io_ops: the io ops vector
849 * Unregister it with the KGDB core.
851 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
853 BUG_ON(kgdb_connected);
856 * KGDB is no longer able to communicate out, so
857 * unregister our callbacks and reset state.
859 kgdb_unregister_callbacks();
861 spin_lock(&kgdb_registration_lock);
863 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
866 spin_unlock(&kgdb_registration_lock);
869 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
870 old_dbg_io_ops->name);
872 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
874 int dbg_io_get_char(void)
876 int ret = dbg_io_ops->read_char();
877 if (ret == NO_POLL_CHAR)
887 * kgdb_breakpoint - generate breakpoint exception
889 * This function will generate a breakpoint exception. It is used at the
890 * beginning of a program to sync up with a debugger and can be used
891 * otherwise as a quick means to stop program execution and "break" into
894 void kgdb_breakpoint(void)
896 atomic_inc(&kgdb_setting_breakpoint);
897 wmb(); /* Sync point before breakpoint */
898 arch_kgdb_breakpoint();
899 wmb(); /* Sync point after breakpoint */
900 atomic_dec(&kgdb_setting_breakpoint);
902 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
904 static int __init opt_kgdb_wait(char *str)
908 kdb_init(KDB_INIT_EARLY);
909 if (kgdb_io_module_registered)
910 kgdb_initial_breakpoint();
915 early_param("kgdbwait", opt_kgdb_wait);