aboutsummaryrefslogblamecommitdiffstats
path: root/kernel/kgdb.c
blob: 14787de568b3c916320d06e5f73184e65966dfcc (plain) (tree)
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134





























                                                                          
                              































                                               
                                         



















































































                                                                             
                               




















































                                                                               










                                                                        






































































































































                                                                            



















































































                                                                            
                                                      

























































































































                                                                        












                                                          
                                     












                                                            
                                                     

                                                                 
         

                                                                    


















































































































                                                                         
                                 






                                                    

                                                     



                                                           



                                                                                




























































































































































































































































































































































































































                                                                                
                                                      

                                                                
                                                       























































































































































































                                                                                

                                                                                  





































































                                                                               
                                             

































                                                                                





                                                                 





                                                                       












































                                                                            
                                     








                                              

                                                                               



























































































                                                                              
                                                         




































































































                                                                         
/*
 * KGDB stub.
 *
 * Maintainer: Jason Wessel <jason.wessel@windriver.com>
 *
 * Copyright (C) 2000-2001 VERITAS Software Corporation.
 * Copyright (C) 2002-2004 Timesys Corporation
 * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
 * Copyright (C) 2004 Pavel Machek <pavel@suse.cz>
 * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
 * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
 * Copyright (C) 2005-2008 Wind River Systems, Inc.
 * Copyright (C) 2007 MontaVista Software, Inc.
 * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 * Contributors at various stages not listed above:
 *  Jason Wessel ( jason.wessel@windriver.com )
 *  George Anzinger <george@mvista.com>
 *  Anurekh Saxena (anurekh.saxena@timesys.com)
 *  Lake Stevens Instrument Division (Glenn Engel)
 *  Jim Kingdon, Cygnus Support.
 *
 * Original KGDB stub: David Grothe <dave@gcom.com>,
 * Tigran Aivazian <tigran@sco.com>
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2. This program is licensed "as is" without any warranty of any
 * kind, whether express or implied.
 */
#include <linux/pid_namespace.h>
#include <linux/clocksource.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/console.h>
#include <linux/threads.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/reboot.h>
#include <linux/string.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/sysrq.h>
#include <linux/init.h>
#include <linux/kgdb.h>
#include <linux/pid.h>
#include <linux/smp.h>
#include <linux/mm.h>

#include <asm/cacheflush.h>
#include <asm/byteorder.h>
#include <asm/atomic.h>
#include <asm/system.h>

static int kgdb_break_asap;

struct kgdb_state {
	int			ex_vector;
	int			signo;
	int			err_code;
	int			cpu;
	int			pass_exception;
	unsigned long		threadid;
	long			kgdb_usethreadid;
	struct pt_regs		*linux_regs;
};

static struct debuggerinfo_struct {
	void			*debuggerinfo;
	struct task_struct	*task;
} kgdb_info[NR_CPUS];

/**
 * kgdb_connected - Is a host GDB connected to us?
 */
int				kgdb_connected;
EXPORT_SYMBOL_GPL(kgdb_connected);

/* All the KGDB handlers are installed */
static int			kgdb_io_module_registered;

/* Guard for recursive entry */
static int			exception_level;

static struct kgdb_io		*kgdb_io_ops;
static DEFINE_SPINLOCK(kgdb_registration_lock);

/* kgdb console driver is loaded */
static int kgdb_con_registered;
/* determine if kgdb console output should be used */
static int kgdb_use_con;

static int __init opt_kgdb_con(char *str)
{
	kgdb_use_con = 1;
	return 0;
}

early_param("kgdbcon", opt_kgdb_con);

module_param(kgdb_use_con, int, 0644);

/*
 * Holds information about breakpoints in a kernel. These breakpoints are
 * added and removed by gdb.
 */
static struct kgdb_bkpt		kgdb_break[KGDB_MAX_BREAKPOINTS] = {
	[0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
};

/*
 * The CPU# of the active CPU, or -1 if none:
 */
atomic_t			kgdb_active = ATOMIC_INIT(-1);

/*
 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
 * bootup code (which might not have percpu set up yet):
 */
static atomic_t			passive_cpu_wait[NR_CPUS];
static atomic_t			cpu_in_kgdb[NR_CPUS];
atomic_t			kgdb_setting_breakpoint;

struct task_struct		*kgdb_usethread;
struct task_struct		*kgdb_contthread;

int				kgdb_single_step;

/* Our I/O buffers. */
static char			remcom_in_buffer[BUFMAX];
static char			remcom_out_buffer[BUFMAX];

/* Storage for the registers, in GDB format. */
static unsigned long		gdb_regs[(NUMREGBYTES +
					sizeof(unsigned long) - 1) /
					sizeof(unsigned long)];

/* to keep track of the CPU which is doing the single stepping*/
atomic_t			kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);

/*
 * If you are debugging a problem where roundup (the collection of
 * all other CPUs) is a problem [this should be extremely rare],
 * then use the nokgdbroundup option to avoid roundup. In that case
 * the other CPUs might interfere with your debugging context, so
 * use this with care:
 */
static int kgdb_do_roundup = 1;

static int __init opt_nokgdbroundup(char *str)
{
	kgdb_do_roundup = 0;

	return 0;
}

early_param("nokgdbroundup", opt_nokgdbroundup);

/*
 * Finally, some KGDB code :-)
 */

/*
 * Weak aliases for breakpoint management,
 * can be overriden by architectures when needed:
 */
int __weak kgdb_validate_break_address(unsigned long addr)
{
	char tmp_variable[BREAK_INSTR_SIZE];

	return probe_kernel_read(tmp_variable, (char *)addr, BREAK_INSTR_SIZE);
}

int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
{
	int err;

	err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
	if (err)
		return err;

	return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
				  BREAK_INSTR_SIZE);
}

int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
{
	return probe_kernel_write((char *)addr,
				  (char *)bundle, BREAK_INSTR_SIZE);
}

unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
{
	return instruction_pointer(regs);
}

int __weak kgdb_arch_init(void)
{
	return 0;
}

int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
{
	return 0;
}

void __weak
kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
{
	return;
}

/**
 *	kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
 *	@regs: Current &struct pt_regs.
 *
 *	This function will be called if the particular architecture must
 *	disable hardware debugging while it is processing gdb packets or
 *	handling exception.
 */
void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
{
}

/*
 * GDB remote protocol parser:
 */

static const char	hexchars[] = "0123456789abcdef";

static int hex(char ch)
{
	if ((ch >= 'a') && (ch <= 'f'))
		return ch - 'a' + 10;
	if ((ch >= '0') && (ch <= '9'))
		return ch - '0';
	if ((ch >= 'A') && (ch <= 'F'))
		return ch - 'A' + 10;
	return -1;
}

/* scan for the sequence $<data>#<checksum> */
static void get_packet(char *buffer)
{
	unsigned char checksum;
	unsigned char xmitcsum;
	int count;
	char ch;

	do {
		/*
		 * Spin and wait around for the start character, ignore all
		 * other characters:
		 */
		while ((ch = (kgdb_io_ops->read_char())) != '$')
			/* nothing */;

		kgdb_connected = 1;
		checksum = 0;
		xmitcsum = -1;

		count = 0;

		/*
		 * now, read until a # or end of buffer is found:
		 */
		while (count < (BUFMAX - 1)) {
			ch = kgdb_io_ops->read_char();
			if (ch == '#')
				break;
			checksum = checksum + ch;
			buffer[count] = ch;
			count = count + 1;
		}
		buffer[count] = 0;

		if (ch == '#') {
			xmitcsum = hex(kgdb_io_ops->read_char()) << 4;
			xmitcsum += hex(kgdb_io_ops->read_char());

			if (checksum != xmitcsum)
				/* failed checksum */
				kgdb_io_ops->write_char('-');
			else
				/* successful transfer */
				kgdb_io_ops->write_char('+');
			if (kgdb_io_ops->flush)
				kgdb_io_ops->flush();
		}
	} while (checksum != xmitcsum);
}

/*
 * Send the packet in buffer.
 * Check for gdb connection if asked for.
 */
static void put_packet(char *buffer)
{
	unsigned char checksum;
	int count;
	char ch;

	/*
	 * $<packet info>#<checksum>.
	 */
	while (1) {
		kgdb_io_ops->write_char('$');
		checksum = 0;
		count = 0;

		while ((ch = buffer[count])) {
			kgdb_io_ops->write_char(ch);
			checksum += ch;
			count++;
		}

		kgdb_io_ops->write_char('#');
		kgdb_io_ops->write_char(hexchars[checksum >> 4]);
		kgdb_io_ops->write_char(hexchars[checksum & 0xf]);
		if (kgdb_io_ops->flush)
			kgdb_io_ops->flush();

		/* Now see what we get in reply. */
		ch = kgdb_io_ops->read_char();

		if (ch == 3)
			ch = kgdb_io_ops->read_char();

		/* If we get an ACK, we are done. */
		if (ch == '+')
			return;

		/*
		 * If we get the start of another packet, this means
		 * that GDB is attempting to reconnect.  We will NAK
		 * the packet being sent, and stop trying to send this
		 * packet.
		 */
		if (ch == '$') {
			kgdb_io_ops->write_char('-');
			if (kgdb_io_ops->flush)
				kgdb_io_ops->flush();
			return;
		}
	}
}

/*
 * Convert the memory pointed to by mem into hex, placing result in buf.
 * Return a pointer to the last char put in buf (null). May return an error.
 */
int kgdb_mem2hex(char *mem, char *buf, int count)
{
	char *tmp;
	int err;

	/*
	 * We use the upper half of buf as an intermediate buffer for the
	 * raw memory copy.  Hex conversion will work against this one.
	 */
	tmp = buf + count;

	err = probe_kernel_read(tmp, mem, count);
	if (!err) {
		while (count > 0) {
			buf = pack_hex_byte(buf, *tmp);
			tmp++;
			count--;
		}

		*buf = 0;
	}

	return err;
}

/*
 * Copy the binary array pointed to by buf into mem.  Fix $, #, and
 * 0x7d escaped with 0x7d.  Return a pointer to the character after
 * the last byte written.
 */
static int kgdb_ebin2mem(char *buf, char *mem, int count)
{
	int err = 0;
	char c;

	while (count-- > 0) {
		c = *buf++;
		if (c == 0x7d)
			c = *buf++ ^ 0x20;

		err = probe_kernel_write(mem, &c, 1);
		if (err)
			break;

		mem++;
	}

	return err;
}

/*
 * Convert the hex array pointed to by buf into binary to be placed in mem.
 * Return a pointer to the character AFTER the last byte written.
 * May return an error.
 */
int kgdb_hex2mem(char *buf, char *mem, int count)
{
	char *tmp_raw;
	char *tmp_hex;

	/*
	 * We use the upper half of buf as an intermediate buffer for the
	 * raw memory that is converted from hex.
	 */
	tmp_raw = buf + count * 2;

	tmp_hex = tmp_raw - 1;
	while (tmp_hex >= buf) {
		tmp_raw--;
		*tmp_raw = hex(*tmp_hex--);
		*tmp_raw |= hex(*tmp_hex--) << 4;
	}

	return probe_kernel_write(mem, tmp_raw, count);
}

/*
 * While we find nice hex chars, build a long_val.
 * Return number of chars processed.
 */
int kgdb_hex2long(char **ptr, unsigned long *long_val)
{
	int hex_val;
	int num = 0;

	*long_val = 0;

	while (**ptr) {
		hex_val = hex(**ptr);
		if (hex_val < 0)
			break;

		*long_val = (*long_val << 4) | hex_val;
		num++;
		(*ptr)++;
	}

	return num;
}

/* Write memory due to an 'M' or 'X' packet. */
static int write_mem_msg(int binary)
{
	char *ptr = &remcom_in_buffer[1];
	unsigned long addr;
	unsigned long length;
	int err;

	if (kgdb_hex2long(&ptr, &addr) > 0 && *(ptr++) == ',' &&
	    kgdb_hex2long(&ptr, &length) > 0 && *(ptr++) == ':') {
		if (binary)
			err = kgdb_ebin2mem(ptr, (char *)addr, length);
		else
			err = kgdb_hex2mem(ptr, (char *)addr, length);
		if (err)
			return err;
		if (CACHE_FLUSH_IS_SAFE)
			flush_icache_range(addr, addr + length + 1);
		return 0;
	}

	return -EINVAL;
}

static void error_packet(char *pkt, int error)
{
	error = -error;
	pkt[0] = 'E';
	pkt[1] = hexchars[(error / 10)];
	pkt[2] = hexchars[(error % 10)];
	pkt[3] = '\0';
}

/*
 * Thread ID accessors. We represent a flat TID space to GDB, where
 * the per CPU idle threads (which under Linux all have PID 0) are
 * remapped to negative TIDs.
 */

#define BUF_THREAD_ID_SIZE	16

static char *pack_threadid(char *pkt, unsigned char *id)
{
	char *limit;

	limit = pkt + BUF_THREAD_ID_SIZE;
	while (pkt < limit)
		pkt = pack_hex_byte(pkt, *id++);

	return pkt;
}

static void int_to_threadref(unsigned char *id, int value)
{
	unsigned char *scan;
	int i = 4;

	scan = (unsigned char *)id;
	while (i--)
		*scan++ = 0;
	*scan++ = (value >> 24) & 0xff;
	*scan++ = (value >> 16) & 0xff;
	*scan++ = (value >> 8) & 0xff;
	*scan++ = (value & 0xff);
}

static struct task_struct *getthread(struct pt_regs *regs, int tid)
{
	/*
	 * Non-positive TIDs are remapped idle tasks:
	 */
	if (tid <= 0)
		return idle_task(-tid);

	/*
	 * find_task_by_pid_ns() does not take the tasklist lock anymore
	 * but is nicely RCU locked - hence is a pretty resilient
	 * thing to use:
	 */
	return find_task_by_pid_ns(tid, &init_pid_ns);
}

/*
 * CPU debug state control:
 */

#ifdef CONFIG_SMP
static void kgdb_wait(struct pt_regs *regs)
{
	unsigned long flags;
	int cpu;

	local_irq_save(flags);
	cpu = raw_smp_processor_id();
	kgdb_info[cpu].debuggerinfo = regs;
	kgdb_info[cpu].task = current;
	/*
	 * Make sure the above info reaches the primary CPU before
	 * our cpu_in_kgdb[] flag setting does:
	 */
	smp_wmb();
	atomic_set(&cpu_in_kgdb[cpu], 1);

	/* Wait till primary CPU is done with debugging */
	while (atomic_read(&passive_cpu_wait[cpu]))
		cpu_relax();

	kgdb_info[cpu].debuggerinfo = NULL;
	kgdb_info[cpu].task = NULL;

	/* fix up hardware debug registers on local cpu */
	if (arch_kgdb_ops.correct_hw_break)
		arch_kgdb_ops.correct_hw_break();

	/* Signal the primary CPU that we are done: */
	atomic_set(&cpu_in_kgdb[cpu], 0);
	clocksource_touch_watchdog();
	local_irq_restore(flags);
}
#endif

/*
 * Some architectures need cache flushes when we set/clear a
 * breakpoint:
 */
static void kgdb_flush_swbreak_addr(unsigned long addr)
{
	if (!CACHE_FLUSH_IS_SAFE)
		return;

	if (current->mm && current->mm->mmap_cache) {
		flush_cache_range(current->mm->mmap_cache,
				  addr, addr + BREAK_INSTR_SIZE);
	}
	/* Force flush instruction cache if it was outside the mm */
	flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
}

/*
 * SW breakpoint management:
 */
static int kgdb_activate_sw_breakpoints(void)
{
	unsigned long addr;
	int error = 0;
	int i;

	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if (kgdb_break[i].state != BP_SET)
			continue;

		addr = kgdb_break[i].bpt_addr;
		error = kgdb_arch_set_breakpoint(addr,
				kgdb_break[i].saved_instr);
		if (error)
			return error;

		kgdb_flush_swbreak_addr(addr);
		kgdb_break[i].state = BP_ACTIVE;
	}
	return 0;
}

static int kgdb_set_sw_break(unsigned long addr)
{
	int err = kgdb_validate_break_address(addr);
	int breakno = -1;
	int i;

	if (err)
		return err;

	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if ((kgdb_break[i].state == BP_SET) &&
					(kgdb_break[i].bpt_addr == addr))
			return -EEXIST;
	}
	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if (kgdb_break[i].state == BP_REMOVED &&
					kgdb_break[i].bpt_addr == addr) {
			breakno = i;
			break;
		}
	}

	if (breakno == -1) {
		for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
			if (kgdb_break[i].state == BP_UNDEFINED) {
				breakno = i;
				break;
			}
		}
	}

	if (breakno == -1)
		return -E2BIG;

	kgdb_break[breakno].state = BP_SET;
	kgdb_break[breakno].type = BP_BREAKPOINT;
	kgdb_break[breakno].bpt_addr = addr;

	return 0;
}

static int kgdb_deactivate_sw_breakpoints(void)
{
	unsigned long addr;
	int error = 0;
	int i;

	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if (kgdb_break[i].state != BP_ACTIVE)
			continue;
		addr = kgdb_break[i].bpt_addr;
		error = kgdb_arch_remove_breakpoint(addr,
					kgdb_break[i].saved_instr);
		if (error)
			return error;

		kgdb_flush_swbreak_addr(addr);
		kgdb_break[i].state = BP_SET;
	}
	return 0;
}

static int kgdb_remove_sw_break(unsigned long addr)
{
	int i;

	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if ((kgdb_break[i].state == BP_SET) &&
				(kgdb_break[i].bpt_addr == addr)) {
			kgdb_break[i].state = BP_REMOVED;
			return 0;
		}
	}
	return -ENOENT;
}

int kgdb_isremovedbreak(unsigned long addr)
{
	int i;

	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if ((kgdb_break[i].state == BP_REMOVED) &&
					(kgdb_break[i].bpt_addr == addr))
			return 1;
	}
	return 0;
}

static int remove_all_break(void)
{
	unsigned long addr;
	int error;
	int i;

	/* Clear memory breakpoints. */
	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if (kgdb_break[i].state != BP_ACTIVE)
			goto setundefined;
		addr = kgdb_break[i].bpt_addr;
		error = kgdb_arch_remove_breakpoint(addr,
				kgdb_break[i].saved_instr);
		if (error)
			printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
			   addr);
setundefined:
		kgdb_break[i].state = BP_UNDEFINED;
	}

	/* Clear hardware breakpoints. */
	if (arch_kgdb_ops.remove_all_hw_break)
		arch_kgdb_ops.remove_all_hw_break();

	return 0;
}

/*
 * Remap normal tasks to their real PID, idle tasks to -1 ... -NR_CPUs:
 */
static inline int shadow_pid(int realpid)
{
	if (realpid)
		return realpid;

	return -1-raw_smp_processor_id();
}

static char gdbmsgbuf[BUFMAX + 1];

static void kgdb_msg_write(const char *s, int len)
{
	char *bufptr;
	int wcount;
	int i;

	/* 'O'utput */
	gdbmsgbuf[0] = 'O';

	/* Fill and send buffers... */
	while (len > 0) {
		bufptr = gdbmsgbuf + 1;

		/* Calculate how many this time */
		if ((len << 1) > (BUFMAX - 2))
			wcount = (BUFMAX - 2) >> 1;
		else
			wcount = len;

		/* Pack in hex chars */
		for (i = 0; i < wcount; i++)
			bufptr = pack_hex_byte(bufptr, s[i]);
		*bufptr = '\0';

		/* Move up */
		s += wcount;
		len -= wcount;

		/* Write packet */
		put_packet(gdbmsgbuf);
	}
}

/*
 * Return true if there is a valid kgdb I/O module.  Also if no
 * debugger is attached a message can be printed to the console about
 * waiting for the debugger to attach.
 *
 * The print_wait argument is only to be true when called from inside
 * the core kgdb_handle_exception, because it will wait for the
 * debugger to attach.
 */
static int kgdb_io_ready(int print_wait)
{
	if (!kgdb_io_ops)
		return 0;
	if (kgdb_connected)
		return 1;
	if (atomic_read(&kgdb_setting_breakpoint))
		return 1;
	if (print_wait)
		printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
	return 1;
}

/*
 * All the functions that start with gdb_cmd are the various
 * operations to implement the handlers for the gdbserial protocol
 * where KGDB is communicating with an external debugger
 */

/* Handle the '?' status packets */
static void gdb_cmd_status(struct kgdb_state *ks)
{
	/*
	 * We know that this packet is only sent
	 * during initial connect.  So to be safe,
	 * we clear out our breakpoints now in case
	 * GDB is reconnecting.
	 */
	remove_all_break();

	remcom_out_buffer[0] = 'S';
	pack_hex_byte(&remcom_out_buffer[1], ks->signo);
}

/* Handle the 'g' get registers request */
static void gdb_cmd_getregs(struct kgdb_state *ks)
{
	struct task_struct *thread;
	void *local_debuggerinfo;
	int i;

	thread = kgdb_usethread;
	if (!thread) {
		thread = kgdb_info[ks->cpu].task;
		local_debuggerinfo = kgdb_info[ks->cpu].debuggerinfo;
	} else {
		local_debuggerinfo = NULL;
		for (i = 0; i < NR_CPUS; i++) {
			/*
			 * Try to find the task on some other
			 * or possibly this node if we do not
			 * find the matching task then we try
			 * to approximate the results.
			 */
			if (thread == kgdb_info[i].task)
				local_debuggerinfo = kgdb_info[i].debuggerinfo;
		}
	}

	/*
	 * All threads that don't have debuggerinfo should be
	 * in __schedule() sleeping, since all other CPUs
	 * are in kgdb_wait, and thus have debuggerinfo.
	 */
	if (local_debuggerinfo) {
		pt_regs_to_gdb_regs(gdb_regs, local_debuggerinfo);
	} else {
		/*
		 * Pull stuff saved during switch_to; nothing
		 * else is accessible (or even particularly
		 * relevant).
		 *
		 * This should be enough for a stack trace.
		 */
		sleeping_thread_to_gdb_regs(gdb_regs, thread);
	}
	kgdb_mem2hex((char *)gdb_regs, remcom_out_buffer, NUMREGBYTES);
}

/* Handle the 'G' set registers request */
static void gdb_cmd_setregs(struct kgdb_state *ks)
{
	kgdb_hex2mem(&remcom_in_buffer[1], (char *)gdb_regs, NUMREGBYTES);

	if (kgdb_usethread && kgdb_usethread != current) {
		error_packet(remcom_out_buffer, -EINVAL);
	} else {
		gdb_regs_to_pt_regs(gdb_regs, ks->linux_regs);
		strcpy(remcom_out_buffer, "OK");
	}
}

/* Handle the 'm' memory read bytes */
static void gdb_cmd_memread(struct kgdb_state *ks)
{
	char *ptr = &remcom_in_buffer[1];
	unsigned long length;
	unsigned long addr;
	int err;

	if (kgdb_hex2long(&ptr, &addr) > 0 && *ptr++ == ',' &&
					kgdb_hex2long(&ptr, &length) > 0) {
		err = kgdb_mem2hex((char *)addr, remcom_out_buffer, length);
		if (err)
			error_packet(remcom_out_buffer, err);
	} else {
		error_packet(remcom_out_buffer, -EINVAL);
	}
}

/* Handle the 'M' memory write bytes */
static void gdb_cmd_memwrite(struct kgdb_state *ks)
{
	int err = write_mem_msg(0);

	if (err)
		error_packet(remcom_out_buffer, err);
	else
		strcpy(remcom_out_buffer, "OK");
}

/* Handle the 'X' memory binary write bytes */
static void gdb_cmd_binwrite(struct kgdb_state *ks)
{
	int err = write_mem_msg(1);

	if (err)
		error_packet(remcom_out_buffer, err);
	else
		strcpy(remcom_out_buffer, "OK");
}

/* Handle the 'D' or 'k', detach or kill packets */
static void gdb_cmd_detachkill(struct kgdb_state *ks)
{
	int error;

	/* The detach case */
	if (remcom_in_buffer[0] == 'D') {
		error = remove_all_break();
		if (error < 0) {
			error_packet(remcom_out_buffer, error);
		} else {
			strcpy(remcom_out_buffer, "OK");
			kgdb_connected = 0;
		}
		put_packet(remcom_out_buffer);
	} else {
		/*
		 * Assume the kill case, with no exit code checking,
		 * trying to force detach the debugger:
		 */
		remove_all_break();
		kgdb_connected = 0;
	}
}

/* Handle the 'R' reboot packets */
static int gdb_cmd_reboot(struct kgdb_state *ks)
{
	/* For now, only honor R0 */
	if (strcmp(remcom_in_buffer, "R0") == 0) {
		printk(KERN_CRIT "Executing emergency reboot\n");
		strcpy(remcom_out_buffer, "OK");
		put_packet(remcom_out_buffer);

		/*
		 * Execution should not return from
		 * machine_emergency_restart()
		 */
		machine_emergency_restart();
		kgdb_connected = 0;

		return 1;
	}
	return 0;
}

/* Handle the 'q' query packets */
static void gdb_cmd_query(struct kgdb_state *ks)
{
	struct task_struct *thread;
	unsigned char thref[8];
	char *ptr;
	int i;

	switch (remcom_in_buffer[1]) {
	case 's':
	case 'f':
		if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10)) {
			error_packet(remcom_out_buffer, -EINVAL);
			break;
		}

		if (remcom_in_buffer[1] == 'f')
			ks->threadid = 1;

		remcom_out_buffer[0] = 'm';
		ptr = remcom_out_buffer + 1;

		for (i = 0; i < 17; ks->threadid++) {
			thread = getthread(ks->linux_regs, ks->threadid);
			if (thread) {
				int_to_threadref(thref, ks->threadid);
				pack_threadid(ptr, thref);
				ptr += BUF_THREAD_ID_SIZE;
				*(ptr++) = ',';
				i++;
			}
		}
		*(--ptr) = '\0';
		break;

	case 'C':
		/* Current thread id */
		strcpy(remcom_out_buffer, "QC");
		ks->threadid = shadow_pid(current->pid);
		int_to_threadref(thref, ks->threadid);
		pack_threadid(remcom_out_buffer + 2, thref);
		break;
	case 'T':
		if (memcmp(remcom_in_buffer + 1, "ThreadExtraInfo,", 16)) {
			error_packet(remcom_out_buffer, -EINVAL);
			break;
		}
		ks->threadid = 0;
		ptr = remcom_in_buffer + 17;
		kgdb_hex2long(&ptr, &ks->threadid);
		if (!getthread(ks->linux_regs, ks->threadid)) {
			error_packet(remcom_out_buffer, -EINVAL);
			break;
		}
		if (ks->threadid > 0) {
			kgdb_mem2hex(getthread(ks->linux_regs,
					ks->threadid)->comm,
					remcom_out_buffer, 16);
		} else {
			static char tmpstr[23 + BUF_THREAD_ID_SIZE];

			sprintf(tmpstr, "Shadow task %d for pid 0",
					(int)(-ks->threadid-1));
			kgdb_mem2hex(tmpstr, remcom_out_buffer, strlen(tmpstr));
		}
		break;
	}
}

/* Handle the 'H' task query packets */
static void gdb_cmd_task(struct kgdb_state *ks)
{
	struct task_struct *thread;
	char *ptr;

	switch (remcom_in_buffer[1]) {
	case 'g':
		ptr = &remcom_in_buffer[2];
		kgdb_hex2long(&ptr, &ks->threadid);
		thread = getthread(ks->linux_regs, ks->threadid);
		if (!thread && ks->threadid > 0) {
			error_packet(remcom_out_buffer, -EINVAL);
			break;
		}
		kgdb_usethread = thread;
		ks->kgdb_usethreadid = ks->threadid;
		strcpy(remcom_out_buffer, "OK");
		break;
	case 'c':
		ptr = &remcom_in_buffer[2];
		kgdb_hex2long(&ptr, &ks->threadid);
		if (!ks->threadid) {
			kgdb_contthread = NULL;
		} else {
			thread = getthread(ks->linux_regs, ks->threadid);
			if (!thread && ks->threadid > 0) {
				error_packet(remcom_out_buffer, -EINVAL);
				break;
			}
			kgdb_contthread = thread;
		}
		strcpy(remcom_out_buffer, "OK");
		break;
	}
}

/* Handle the 'T' thread query packets */
static void gdb_cmd_thread(struct kgdb_state *ks)
{
	char *ptr = &remcom_in_buffer[1];
	struct task_struct *thread;

	kgdb_hex2long(&ptr, &ks->threadid);
	thread = getthread(ks->linux_regs, ks->threadid);
	if (thread)
		strcpy(remcom_out_buffer, "OK");
	else
		error_packet(remcom_out_buffer, -EINVAL);
}

/* Handle the 'z' or 'Z' breakpoint remove or set packets */
static void gdb_cmd_break(struct kgdb_state *ks)
{
	/*
	 * Since GDB-5.3, it's been drafted that '0' is a software
	 * breakpoint, '1' is a hardware breakpoint, so let's do that.
	 */
	char *bpt_type = &remcom_in_buffer[1];
	char *ptr = &remcom_in_buffer[2];
	unsigned long addr;
	unsigned long length;
	int error = 0;

	if (arch_kgdb_ops.set_hw_breakpoint && *bpt_type >= '1') {
		/* Unsupported */
		if (*bpt_type > '4')
			return;
	} else {
		if (*bpt_type != '0' && *bpt_type != '1')
			/* Unsupported. */
			return;
	}

	/*
	 * Test if this is a hardware breakpoint, and
	 * if we support it:
	 */
	if (*bpt_type == '1' && !(arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT))
		/* Unsupported. */
		return;

	if (*(ptr++) != ',') {
		error_packet(remcom_out_buffer, -EINVAL);
		return;
	}
	if (!kgdb_hex2long(&ptr, &addr)) {
		error_packet(remcom_out_buffer, -EINVAL);
		return;
	}
	if (*(ptr++) != ',' ||
		!kgdb_hex2long(&ptr, &length)) {
		error_packet(remcom_out_buffer, -EINVAL);
		return;
	}

	if (remcom_in_buffer[0] == 'Z' && *bpt_type == '0')
		error = kgdb_set_sw_break(addr);
	else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
		error = kgdb_remove_sw_break(addr);
	else if (remcom_in_buffer[0] == 'Z')
		error = arch_kgdb_ops.set_hw_breakpoint(addr,
			(int)length, *bpt_type - '0');
	else if (remcom_in_buffer[0] == 'z')
		error = arch_kgdb_ops.remove_hw_breakpoint(addr,
			(int) length, *bpt_type - '0');

	if (error == 0)
		strcpy(remcom_out_buffer, "OK");
	else
		error_packet(remcom_out_buffer, error);
}

/* Handle the 'C' signal / exception passing packets */
static int gdb_cmd_exception_pass(struct kgdb_state *ks)
{
	/* C09 == pass exception
	 * C15 == detach kgdb, pass exception
	 */
	if (remcom_in_buffer[1] == '0' && remcom_in_buffer[2] == '9') {

		ks->pass_exception = 1;
		remcom_in_buffer[0] = 'c';

	} else if (remcom_in_buffer[1] == '1' && remcom_in_buffer[2] == '5') {

		ks->pass_exception = 1;
		remcom_in_buffer[0] = 'D';
		remove_all_break();
		kgdb_connected = 0;
		return 1;

	} else {
		error_packet(remcom_out_buffer, -EINVAL);
		return 0;
	}

	/* Indicate fall through */
	return -1;
}

/*
 * This function performs all gdbserial command procesing
 */
static int gdb_serial_stub(struct kgdb_state *ks)
{
	int error = 0;
	int tmp;

	/* Clear the out buffer. */
	memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));

	if (kgdb_connected) {
		unsigned char thref[8];
		char *ptr;

		/* Reply to host that an exception has occurred */
		ptr = remcom_out_buffer;
		*ptr++ = 'T';
		ptr = pack_hex_byte(ptr, ks->signo);
		ptr += strlen(strcpy(ptr, "thread:"));
		int_to_threadref(thref, shadow_pid(current->pid));
		ptr = pack_threadid(ptr, thref);
		*ptr++ = ';';
		put_packet(remcom_out_buffer);
	}

	kgdb_usethread = kgdb_info[ks->cpu].task;
	ks->kgdb_usethreadid = shadow_pid(kgdb_info[ks->cpu].task->pid);
	ks->pass_exception = 0;

	while (1) {
		error = 0;

		/* Clear the out buffer. */
		memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));

		get_packet(remcom_in_buffer);

		switch (remcom_in_buffer[0]) {
		case '?': /* gdbserial status */
			gdb_cmd_status(ks);
			break;
		case 'g': /* return the value of the CPU registers */
			gdb_cmd_getregs(ks);
			break;
		case 'G': /* set the value of the CPU registers - return OK */
			gdb_cmd_setregs(ks);
			break;
		case 'm': /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
			gdb_cmd_memread(ks);
			break;
		case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA..AA */
			gdb_cmd_memwrite(ks);
			break;
		case 'X': /* XAA..AA,LLLL: Write LLLL bytes at address AA..AA */
			gdb_cmd_binwrite(ks);
			break;
			/* kill or detach. KGDB should treat this like a
			 * continue.
			 */
		case 'D': /* Debugger detach */
		case 'k': /* Debugger detach via kill */
			gdb_cmd_detachkill(ks);
			goto default_handle;
		case 'R': /* Reboot */
			if (gdb_cmd_reboot(ks))
				goto default_handle;
			break;
		case 'q': /* query command */
			gdb_cmd_query(ks);
			break;
		case 'H': /* task related */
			gdb_cmd_task(ks);
			break;
		case 'T': /* Query thread status */
			gdb_cmd_thread(ks);
			break;
		case 'z': /* Break point remove */
		case 'Z': /* Break point set */
			gdb_cmd_break(ks);
			break;
		case 'C': /* Exception passing */
			tmp = gdb_cmd_exception_pass(ks);
			if (tmp > 0)
				goto default_handle;
			if (tmp == 0)
				break;
			/* Fall through on tmp < 0 */
		case 'c': /* Continue packet */
		case 's': /* Single step packet */
			if (kgdb_contthread && kgdb_contthread != current) {
				/* Can't switch threads in kgdb */
				error_packet(remcom_out_buffer, -EINVAL);
				break;
			}
			kgdb_activate_sw_breakpoints();
			/* Fall through to default processing */
		default:
default_handle:
			error = kgdb_arch_handle_exception(ks->ex_vector,
						ks->signo,
						ks->err_code,
						remcom_in_buffer,
						remcom_out_buffer,
						ks->linux_regs);
			/*
			 * Leave cmd processing on error, detach,
			 * kill, continue, or single step.
			 */
			if (error >= 0 || remcom_in_buffer[0] == 'D' ||
			    remcom_in_buffer[0] == 'k') {
				error = 0;
				goto kgdb_exit;
			}

		}

		/* reply to the request */
		put_packet(remcom_out_buffer);
	}

kgdb_exit:
	if (ks->pass_exception)
		error = 1;
	return error;
}

static int kgdb_reenter_check(struct kgdb_state *ks)
{
	unsigned long addr;

	if (atomic_read(&kgdb_active) != raw_smp_processor_id())
		return 0;

	/* Panic on recursive debugger calls: */
	exception_level++;
	addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
	kgdb_deactivate_sw_breakpoints();

	/*
	 * If the break point removed ok at the place exception
	 * occurred, try to recover and print a warning to the end
	 * user because the user planted a breakpoint in a place that
	 * KGDB needs in order to function.
	 */
	if (kgdb_remove_sw_break(addr) == 0) {
		exception_level = 0;
		kgdb_skipexception(ks->ex_vector, ks->linux_regs);
		kgdb_activate_sw_breakpoints();
		printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
			addr);
		WARN_ON_ONCE(1);

		return 1;
	}
	remove_all_break();
	kgdb_skipexception(ks->ex_vector, ks->linux_regs);

	if (exception_level > 1) {
		dump_stack();
		panic("Recursive entry to debugger");
	}

	printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
	dump_stack();
	panic("Recursive entry to debugger");

	return 1;
}

/*
 * kgdb_handle_exception() - main entry point from a kernel exception
 *
 * Locking hierarchy:
 *	interface locks, if any (begin_session)
 *	kgdb lock (kgdb_active)
 */
int
kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
{
	struct kgdb_state kgdb_var;
	struct kgdb_state *ks = &kgdb_var;
	unsigned long flags;
	int error = 0;
	int i, cpu;

	ks->cpu			= raw_smp_processor_id();
	ks->ex_vector		= evector;
	ks->signo		= signo;
	ks->ex_vector		= evector;
	ks->err_code		= ecode;
	ks->kgdb_usethreadid	= 0;
	ks->linux_regs		= regs;

	if (kgdb_reenter_check(ks))
		return 0; /* Ouch, double exception ! */

acquirelock:
	/*
	 * Interrupts will be restored by the 'trap return' code, except when
	 * single stepping.
	 */
	local_irq_save(flags);

	cpu = raw_smp_processor_id();

	/*
	 * Acquire the kgdb_active lock:
	 */
	while (atomic_cmpxchg(&kgdb_active, -1, cpu) != -1)
		cpu_relax();

	/*
	 * Do not start the debugger connection on this CPU if the last
	 * instance of the exception handler wanted to come into the
	 * debugger on a different CPU via a single step
	 */
	if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
	    atomic_read(&kgdb_cpu_doing_single_step) != cpu) {

		atomic_set(&kgdb_active, -1);
		clocksource_touch_watchdog();
		local_irq_restore(flags);

		goto acquirelock;
	}

	if (!kgdb_io_ready(1)) {
		error = 1;
		goto kgdb_restore; /* No I/O connection, so resume the system */
	}

	/*
	 * Don't enter if we have hit a removed breakpoint.
	 */
	if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
		goto kgdb_restore;

	/* Call the I/O driver's pre_exception routine */
	if (kgdb_io_ops->pre_exception)
		kgdb_io_ops->pre_exception();

	kgdb_info[ks->cpu].debuggerinfo = ks->linux_regs;
	kgdb_info[ks->cpu].task = current;

	kgdb_disable_hw_debug(ks->linux_regs);

	/*
	 * Get the passive CPU lock which will hold all the non-primary
	 * CPU in a spin state while the debugger is active
	 */
	if (!kgdb_single_step || !kgdb_contthread) {
		for (i = 0; i < NR_CPUS; i++)
			atomic_set(&passive_cpu_wait[i], 1);
	}

	/*
	 * spin_lock code is good enough as a barrier so we don't
	 * need one here:
	 */
	atomic_set(&cpu_in_kgdb[ks->cpu], 1);

#ifdef CONFIG_SMP
	/* Signal the other CPUs to enter kgdb_wait() */
	if ((!kgdb_single_step || !kgdb_contthread) && kgdb_do_roundup)
		kgdb_roundup_cpus(flags);
#endif

	/*
	 * Wait for the other CPUs to be notified and be waiting for us:
	 */
	for_each_online_cpu(i) {
		while (!atomic_read(&cpu_in_kgdb[i]))
			cpu_relax();
	}

	/*
	 * At this point the primary processor is completely
	 * in the debugger and all secondary CPUs are quiescent
	 */
	kgdb_post_primary_code(ks->linux_regs, ks->ex_vector, ks->err_code);
	kgdb_deactivate_sw_breakpoints();
	kgdb_single_step = 0;
	kgdb_contthread = NULL;
	exception_level = 0;

	/* Talk to debugger with gdbserial protocol */
	error = gdb_serial_stub(ks);

	/* Call the I/O driver's post_exception routine */
	if (kgdb_io_ops->post_exception)
		kgdb_io_ops->post_exception();

	kgdb_info[ks->cpu].debuggerinfo = NULL;
	kgdb_info[ks->cpu].task = NULL;
	atomic_set(&cpu_in_kgdb[ks->cpu], 0);

	if (!kgdb_single_step || !kgdb_contthread) {
		for (i = NR_CPUS-1; i >= 0; i--)
			atomic_set(&passive_cpu_wait[i], 0);
		/*
		 * Wait till all the CPUs have quit
		 * from the debugger.
		 */
		for_each_online_cpu(i) {
			while (atomic_read(&cpu_in_kgdb[i]))
				cpu_relax();
		}
	}

kgdb_restore:
	/* Free kgdb_active */
	atomic_set(&kgdb_active, -1);
	clocksource_touch_watchdog();
	local_irq_restore(flags);

	return error;
}

int kgdb_nmicallback(int cpu, void *regs)
{
#ifdef CONFIG_SMP
	if (!atomic_read(&cpu_in_kgdb[cpu]) &&
			atomic_read(&kgdb_active) != cpu &&
			atomic_read(&cpu_in_kgdb[atomic_read(&kgdb_active)])) {
		kgdb_wait((struct pt_regs *)regs);
		return 0;
	}
#endif
	return 1;
}

void kgdb_console_write(struct console *co, const char *s, unsigned count)
{
	unsigned long flags;

	/* If we're debugging, or KGDB has not connected, don't try
	 * and print. */
	if (!kgdb_connected || atomic_read(&kgdb_active) != -1)
		return;

	local_irq_save(flags);
	kgdb_msg_write(s, count);
	local_irq_restore(flags);
}

static struct console kgdbcons = {
	.name		= "kgdb",
	.write		= kgdb_console_write,
	.flags		= CON_PRINTBUFFER | CON_ENABLED,
	.index		= -1,
};

#ifdef CONFIG_MAGIC_SYSRQ
static void sysrq_handle_gdb(int key, struct tty_struct *tty)
{
	if (!kgdb_io_ops) {
		printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
		return;
	}
	if (!kgdb_connected)
		printk(KERN_CRIT "Entering KGDB\n");

	kgdb_breakpoint();
}

static struct sysrq_key_op sysrq_gdb_op = {
	.handler	= sysrq_handle_gdb,
	.help_msg	= "Gdb",
	.action_msg	= "GDB",
};
#endif

static void kgdb_register_callbacks(void)
{
	if (!kgdb_io_module_registered) {
		kgdb_io_module_registered = 1;
		kgdb_arch_init();
#ifdef CONFIG_MAGIC_SYSRQ
		register_sysrq_key('g', &sysrq_gdb_op);
#endif
		if (kgdb_use_con && !kgdb_con_registered) {
			register_console(&kgdbcons);
			kgdb_con_registered = 1;
		}
	}
}

static void kgdb_unregister_callbacks(void)
{
	/*
	 * When this routine is called KGDB should unregister from the
	 * panic handler and clean up, making sure it is not handling any
	 * break exceptions at the time.
	 */
	if (kgdb_io_module_registered) {
		kgdb_io_module_registered = 0;
		kgdb_arch_exit();
#ifdef CONFIG_MAGIC_SYSRQ
		unregister_sysrq_key('g', &sysrq_gdb_op);
#endif
		if (kgdb_con_registered) {
			unregister_console(&kgdbcons);
			kgdb_con_registered = 0;
		}
	}
}

static void kgdb_initial_breakpoint(void)
{
	kgdb_break_asap = 0;

	printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
	kgdb_breakpoint();
}

/**
 *	kgdb_register_io_module - register KGDB IO module
 *	@new_kgdb_io_ops: the io ops vector
 *
 *	Register it with the KGDB core.
 */
int kgdb_register_io_module(struct kgdb_io *new_kgdb_io_ops)
{
	int err;

	spin_lock(&kgdb_registration_lock);

	if (kgdb_io_ops) {
		spin_unlock(&kgdb_registration_lock);

		printk(KERN_ERR "kgdb: Another I/O driver is already "
				"registered with KGDB.\n");
		return -EBUSY;
	}

	if (new_kgdb_io_ops->init) {
		err = new_kgdb_io_ops->init();
		if (err) {
			spin_unlock(&kgdb_registration_lock);
			return err;
		}
	}

	kgdb_io_ops = new_kgdb_io_ops;

	spin_unlock(&kgdb_registration_lock);

	printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
	       new_kgdb_io_ops->name);

	/* Arm KGDB now. */
	kgdb_register_callbacks();

	if (kgdb_break_asap)
		kgdb_initial_breakpoint();

	return 0;
}
EXPORT_SYMBOL_GPL(kgdb_register_io_module);

/**
 *	kkgdb_unregister_io_module - unregister KGDB IO module
 *	@old_kgdb_io_ops: the io ops vector
 *
 *	Unregister it with the KGDB core.
 */
void kgdb_unregister_io_module(struct kgdb_io *old_kgdb_io_ops)
{
	BUG_ON(kgdb_connected);

	/*
	 * KGDB is no longer able to communicate out, so
	 * unregister our callbacks and reset state.
	 */
	kgdb_unregister_callbacks();

	spin_lock(&kgdb_registration_lock);

	WARN_ON_ONCE(kgdb_io_ops != old_kgdb_io_ops);
	kgdb_io_ops = NULL;

	spin_unlock(&kgdb_registration_lock);

	printk(KERN_INFO
		"kgdb: Unregistered I/O driver %s, debugger disabled.\n",
		old_kgdb_io_ops->name);
}
EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);

/**
 * kgdb_breakpoint - generate breakpoint exception
 *
 * This function will generate a breakpoint exception.  It is used at the
 * beginning of a program to sync up with a debugger and can be used
 * otherwise as a quick means to stop program execution and "break" into
 * the debugger.
 */
void kgdb_breakpoint(void)
{
	atomic_set(&kgdb_setting_breakpoint, 1);
	wmb(); /* Sync point before breakpoint */
	arch_kgdb_breakpoint();
	wmb(); /* Sync point after breakpoint */
	atomic_set(&kgdb_setting_breakpoint, 0);
}
EXPORT_SYMBOL_GPL(kgdb_breakpoint);

static int __init opt_kgdb_wait(char *str)
{
	kgdb_break_asap = 1;

	if (kgdb_io_module_registered)
		kgdb_initial_breakpoint();

	return 0;
}

early_param("kgdbwait", opt_kgdb_wait);