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 static 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_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
213 * kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
214 * @regs: Current &struct pt_regs.
216 * This function will be called if the particular architecture must
217 * disable hardware debugging while it is processing gdb packets or
218 * handling exception.
220 void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
225 * Some architectures need cache flushes when we set/clear a
228 static void kgdb_flush_swbreak_addr(unsigned long addr)
230 if (!CACHE_FLUSH_IS_SAFE)
233 if (current->mm && current->mm->mmap_cache) {
234 flush_cache_range(current->mm->mmap_cache,
235 addr, addr + BREAK_INSTR_SIZE);
237 /* Force flush instruction cache if it was outside the mm */
238 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
242 * SW breakpoint management:
244 int dbg_activate_sw_breakpoints(void)
251 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
252 if (kgdb_break[i].state != BP_SET)
255 addr = kgdb_break[i].bpt_addr;
256 error = kgdb_arch_set_breakpoint(addr,
257 kgdb_break[i].saved_instr);
260 printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
264 kgdb_flush_swbreak_addr(addr);
265 kgdb_break[i].state = BP_ACTIVE;
270 int dbg_set_sw_break(unsigned long addr)
272 int err = kgdb_validate_break_address(addr);
279 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
280 if ((kgdb_break[i].state == BP_SET) &&
281 (kgdb_break[i].bpt_addr == addr))
284 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
285 if (kgdb_break[i].state == BP_REMOVED &&
286 kgdb_break[i].bpt_addr == addr) {
293 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
294 if (kgdb_break[i].state == BP_UNDEFINED) {
304 kgdb_break[breakno].state = BP_SET;
305 kgdb_break[breakno].type = BP_BREAKPOINT;
306 kgdb_break[breakno].bpt_addr = addr;
311 int dbg_deactivate_sw_breakpoints(void)
318 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
319 if (kgdb_break[i].state != BP_ACTIVE)
321 addr = kgdb_break[i].bpt_addr;
322 error = kgdb_arch_remove_breakpoint(addr,
323 kgdb_break[i].saved_instr);
325 printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
329 kgdb_flush_swbreak_addr(addr);
330 kgdb_break[i].state = BP_SET;
335 int dbg_remove_sw_break(unsigned long addr)
339 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
340 if ((kgdb_break[i].state == BP_SET) &&
341 (kgdb_break[i].bpt_addr == addr)) {
342 kgdb_break[i].state = BP_REMOVED;
349 int kgdb_isremovedbreak(unsigned long addr)
353 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
354 if ((kgdb_break[i].state == BP_REMOVED) &&
355 (kgdb_break[i].bpt_addr == addr))
361 int dbg_remove_all_break(void)
367 /* Clear memory breakpoints. */
368 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
369 if (kgdb_break[i].state != BP_ACTIVE)
371 addr = kgdb_break[i].bpt_addr;
372 error = kgdb_arch_remove_breakpoint(addr,
373 kgdb_break[i].saved_instr);
375 printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
378 kgdb_break[i].state = BP_UNDEFINED;
381 /* Clear hardware breakpoints. */
382 if (arch_kgdb_ops.remove_all_hw_break)
383 arch_kgdb_ops.remove_all_hw_break();
389 * Return true if there is a valid kgdb I/O module. Also if no
390 * debugger is attached a message can be printed to the console about
391 * waiting for the debugger to attach.
393 * The print_wait argument is only to be true when called from inside
394 * the core kgdb_handle_exception, because it will wait for the
395 * debugger to attach.
397 static int kgdb_io_ready(int print_wait)
403 if (atomic_read(&kgdb_setting_breakpoint))
406 #ifdef CONFIG_KGDB_KDB
408 printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
410 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
416 static int kgdb_reenter_check(struct kgdb_state *ks)
420 if (atomic_read(&kgdb_active) != raw_smp_processor_id())
423 /* Panic on recursive debugger calls: */
425 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
426 dbg_deactivate_sw_breakpoints();
429 * If the break point removed ok at the place exception
430 * occurred, try to recover and print a warning to the end
431 * user because the user planted a breakpoint in a place that
432 * KGDB needs in order to function.
434 if (dbg_remove_sw_break(addr) == 0) {
436 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
437 dbg_activate_sw_breakpoints();
438 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
444 dbg_remove_all_break();
445 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
447 if (exception_level > 1) {
449 panic("Recursive entry to debugger");
452 printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
454 panic("Recursive entry to debugger");
459 static void dbg_cpu_switch(int cpu, int next_cpu)
461 /* Mark the cpu we are switching away from as a slave when it
462 * holds the kgdb_active token. This must be done so that the
463 * that all the cpus wait in for the debug core will not enter
464 * again as the master. */
465 if (cpu == atomic_read(&kgdb_active)) {
466 kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
467 kgdb_info[cpu].exception_state &= ~DCPU_WANT_MASTER;
469 kgdb_info[next_cpu].exception_state |= DCPU_NEXT_MASTER;
472 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
475 int sstep_tries = 100;
481 * Interrupts will be restored by the 'trap return' code, except when
484 local_irq_save(flags);
487 kgdb_info[cpu].debuggerinfo = regs;
488 kgdb_info[cpu].task = current;
489 kgdb_info[cpu].ret_state = 0;
490 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
492 * Make sure the above info reaches the primary CPU before
493 * our cpu_in_kgdb[] flag setting does:
495 atomic_inc(&cpu_in_kgdb[cpu]);
498 * CPU will loop if it is a slave or request to become a kgdb
499 * master cpu and acquire the kgdb_active lock:
503 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
504 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
505 goto cpu_master_loop;
506 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
507 if (atomic_cmpxchg(&kgdb_active, -1, cpu) == cpu)
509 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
510 if (!atomic_read(&passive_cpu_wait[cpu]))
514 /* Return to normal operation by executing any
515 * hw breakpoint fixup.
517 if (arch_kgdb_ops.correct_hw_break)
518 arch_kgdb_ops.correct_hw_break();
521 atomic_dec(&cpu_in_kgdb[cpu]);
522 touch_softlockup_watchdog_sync();
523 clocksource_touch_watchdog();
524 local_irq_restore(flags);
531 * For single stepping, try to only enter on the processor
532 * that was single stepping. To gaurd against a deadlock, the
533 * kernel will only try for the value of sstep_tries before
534 * giving up and continuing on.
536 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
537 (kgdb_info[cpu].task &&
538 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
539 atomic_set(&kgdb_active, -1);
540 touch_softlockup_watchdog_sync();
541 clocksource_touch_watchdog();
542 local_irq_restore(flags);
547 if (!kgdb_io_ready(1)) {
548 kgdb_info[cpu].ret_state = 1;
549 goto kgdb_restore; /* No I/O connection, resume the system */
553 * Don't enter if we have hit a removed breakpoint.
555 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
558 /* Call the I/O driver's pre_exception routine */
559 if (dbg_io_ops->pre_exception)
560 dbg_io_ops->pre_exception();
562 kgdb_disable_hw_debug(ks->linux_regs);
565 * Get the passive CPU lock which will hold all the non-primary
566 * CPU in a spin state while the debugger is active
568 if (!kgdb_single_step) {
569 for (i = 0; i < NR_CPUS; i++)
570 atomic_inc(&passive_cpu_wait[i]);
574 /* Signal the other CPUs to enter kgdb_wait() */
575 if ((!kgdb_single_step) && kgdb_do_roundup)
576 kgdb_roundup_cpus(flags);
580 * Wait for the other CPUs to be notified and be waiting for us:
582 for_each_online_cpu(i) {
583 while (kgdb_do_roundup && !atomic_read(&cpu_in_kgdb[i]))
588 * At this point the primary processor is completely
589 * in the debugger and all secondary CPUs are quiescent
591 kgdb_post_primary_code(ks->linux_regs, ks->ex_vector, ks->err_code);
592 dbg_deactivate_sw_breakpoints();
593 kgdb_single_step = 0;
594 kgdb_contthread = current;
596 trace_on = tracing_is_on();
604 error = kdb_stub(ks);
606 error = gdb_serial_stub(ks);
609 if (error == DBG_PASS_EVENT) {
610 dbg_kdb_mode = !dbg_kdb_mode;
612 } else if (error == DBG_SWITCH_CPU_EVENT) {
613 dbg_cpu_switch(cpu, dbg_switch_cpu);
616 kgdb_info[cpu].ret_state = error;
621 /* Call the I/O driver's post_exception routine */
622 if (dbg_io_ops->post_exception)
623 dbg_io_ops->post_exception();
625 atomic_dec(&cpu_in_kgdb[ks->cpu]);
627 if (!kgdb_single_step) {
628 for (i = NR_CPUS-1; i >= 0; i--)
629 atomic_dec(&passive_cpu_wait[i]);
631 * Wait till all the CPUs have quit from the debugger,
632 * but allow a CPU that hit an exception and is
633 * waiting to become the master to remain in the debug
636 for_each_online_cpu(i) {
637 while (kgdb_do_roundup &&
638 atomic_read(&cpu_in_kgdb[i]) &&
639 !(kgdb_info[i].exception_state &
646 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
647 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
648 if (kgdb_info[sstep_cpu].task)
649 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
655 /* Free kgdb_active */
656 atomic_set(&kgdb_active, -1);
657 touch_softlockup_watchdog_sync();
658 clocksource_touch_watchdog();
659 local_irq_restore(flags);
661 return kgdb_info[cpu].ret_state;
665 * kgdb_handle_exception() - main entry point from a kernel exception
668 * interface locks, if any (begin_session)
669 * kgdb lock (kgdb_active)
672 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
674 struct kgdb_state kgdb_var;
675 struct kgdb_state *ks = &kgdb_var;
678 ks->cpu = raw_smp_processor_id();
679 ks->ex_vector = evector;
681 ks->ex_vector = evector;
682 ks->err_code = ecode;
683 ks->kgdb_usethreadid = 0;
684 ks->linux_regs = regs;
686 if (kgdb_reenter_check(ks))
687 return 0; /* Ouch, double exception ! */
688 kgdb_info[ks->cpu].exception_state |= DCPU_WANT_MASTER;
689 ret = kgdb_cpu_enter(ks, regs);
690 kgdb_info[ks->cpu].exception_state &= ~(DCPU_WANT_MASTER |
695 int kgdb_nmicallback(int cpu, void *regs)
698 struct kgdb_state kgdb_var;
699 struct kgdb_state *ks = &kgdb_var;
701 memset(ks, 0, sizeof(struct kgdb_state));
703 ks->linux_regs = regs;
705 if (!atomic_read(&cpu_in_kgdb[cpu]) &&
706 atomic_read(&kgdb_active) != -1 &&
707 atomic_read(&kgdb_active) != cpu) {
708 kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
709 kgdb_cpu_enter(ks, regs);
710 kgdb_info[cpu].exception_state &= ~DCPU_IS_SLAVE;
717 static void kgdb_console_write(struct console *co, const char *s,
722 /* If we're debugging, or KGDB has not connected, don't try
724 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
727 local_irq_save(flags);
728 gdbstub_msg_write(s, count);
729 local_irq_restore(flags);
732 static struct console kgdbcons = {
734 .write = kgdb_console_write,
735 .flags = CON_PRINTBUFFER | CON_ENABLED,
739 #ifdef CONFIG_MAGIC_SYSRQ
740 static void sysrq_handle_dbg(int key, struct tty_struct *tty)
743 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
746 if (!kgdb_connected) {
747 #ifdef CONFIG_KGDB_KDB
749 printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
751 printk(KERN_CRIT "Entering KGDB\n");
758 static struct sysrq_key_op sysrq_dbg_op = {
759 .handler = sysrq_handle_dbg,
760 .help_msg = "debug(G)",
761 .action_msg = "DEBUG",
765 static void kgdb_register_callbacks(void)
767 if (!kgdb_io_module_registered) {
768 kgdb_io_module_registered = 1;
770 #ifdef CONFIG_MAGIC_SYSRQ
771 register_sysrq_key('g', &sysrq_dbg_op);
773 if (kgdb_use_con && !kgdb_con_registered) {
774 register_console(&kgdbcons);
775 kgdb_con_registered = 1;
780 static void kgdb_unregister_callbacks(void)
783 * When this routine is called KGDB should unregister from the
784 * panic handler and clean up, making sure it is not handling any
785 * break exceptions at the time.
787 if (kgdb_io_module_registered) {
788 kgdb_io_module_registered = 0;
790 #ifdef CONFIG_MAGIC_SYSRQ
791 unregister_sysrq_key('g', &sysrq_dbg_op);
793 if (kgdb_con_registered) {
794 unregister_console(&kgdbcons);
795 kgdb_con_registered = 0;
800 static void kgdb_initial_breakpoint(void)
804 printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
809 * kgdb_register_io_module - register KGDB IO module
810 * @new_dbg_io_ops: the io ops vector
812 * Register it with the KGDB core.
814 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
818 spin_lock(&kgdb_registration_lock);
821 spin_unlock(&kgdb_registration_lock);
823 printk(KERN_ERR "kgdb: Another I/O driver is already "
824 "registered with KGDB.\n");
828 if (new_dbg_io_ops->init) {
829 err = new_dbg_io_ops->init();
831 spin_unlock(&kgdb_registration_lock);
836 dbg_io_ops = new_dbg_io_ops;
838 spin_unlock(&kgdb_registration_lock);
840 printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
841 new_dbg_io_ops->name);
844 kgdb_register_callbacks();
847 kgdb_initial_breakpoint();
851 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
854 * kkgdb_unregister_io_module - unregister KGDB IO module
855 * @old_dbg_io_ops: the io ops vector
857 * Unregister it with the KGDB core.
859 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
861 BUG_ON(kgdb_connected);
864 * KGDB is no longer able to communicate out, so
865 * unregister our callbacks and reset state.
867 kgdb_unregister_callbacks();
869 spin_lock(&kgdb_registration_lock);
871 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
874 spin_unlock(&kgdb_registration_lock);
877 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
878 old_dbg_io_ops->name);
880 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
882 int dbg_io_get_char(void)
884 int ret = dbg_io_ops->read_char();
885 if (ret == NO_POLL_CHAR)
895 * kgdb_breakpoint - generate breakpoint exception
897 * This function will generate a breakpoint exception. It is used at the
898 * beginning of a program to sync up with a debugger and can be used
899 * otherwise as a quick means to stop program execution and "break" into
902 void kgdb_breakpoint(void)
904 atomic_inc(&kgdb_setting_breakpoint);
905 wmb(); /* Sync point before breakpoint */
906 arch_kgdb_breakpoint();
907 wmb(); /* Sync point after breakpoint */
908 atomic_dec(&kgdb_setting_breakpoint);
910 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
912 static int __init opt_kgdb_wait(char *str)
916 kdb_init(KDB_INIT_EARLY);
917 if (kgdb_io_module_registered)
918 kgdb_initial_breakpoint();
923 early_param("kgdbwait", opt_kgdb_wait);