Move kernel/kgdb.c to kernel/debug/debug_core.c

Move kgdb.c in preparation to separate the gdbstub from the debug
core and exception handling.

CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

1 files changed, 1764 insertions, 0 deletions

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
new file mode 100644
index 000000000000..11f3515ca83f
--- /dev/null
+++ b/kernel/debug/debug_core.c
@@ -0,0 +1,1764 @@
+/*
+ * 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>
+#include <asm/unaligned.h>
+
+static int kgdb_break_asap;
+
+#define KGDB_MAX_THREAD_QUERY 17
+struct kgdb_state {
+        int                     ex_vector;
+        int                     signo;
+        int                     err_code;
+        int                     cpu;
+        int                     pass_exception;
+        unsigned long           thr_query;
+        unsigned long           threadid;
+        long                    kgdb_usethreadid;
+        struct pt_regs          *linux_regs;
+};
+
+/* Exception state values */
+#define DCPU_WANT_MASTER 0x1 /* Waiting to become a master kgdb cpu */
+#define DCPU_NEXT_MASTER 0x2 /* Transition from one master cpu to another */
+#define DCPU_IS_SLAVE    0x4 /* Slave cpu enter exception */
+#define DCPU_SSTEP       0x8 /* CPU is single stepping */
+
+static struct debuggerinfo_struct {
+        void                    *debuggerinfo;
+        struct task_struct      *task;
+        int                     exception_state;
+} 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;
+pid_t                           kgdb_sstep_pid;
+
+/* 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_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);
+}
+
+int __weak kgdb_validate_break_address(unsigned long addr)
+{
+        char tmp_variable[BREAK_INSTR_SIZE];
+        int err;
+        /* Validate setting the breakpoint and then removing it.  In the
+         * remove fails, the kernel needs to emit a bad message because we
+         * are deep trouble not being able to put things back the way we
+         * found them.
+         */
+        err = kgdb_arch_set_breakpoint(addr, tmp_variable);
+        if (err)
+                return err;
+        err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
+        if (err)
+                printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
+                   "memory destroyed at: %lx", addr);
+        return err;
+}
+
+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 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(hex_asc_hi(checksum));
+                kgdb_io_ops->write_char(hex_asc_lo(checksum));
+                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 -EFAULT on failure or 0 on success.
+ * The input buf is overwitten with the result to write to mem.
+ */
+static int kgdb_ebin2mem(char *buf, char *mem, int count)
+{
+        int size = 0;
+        char *c = buf;
+
+        while (count-- > 0) {
+                c[size] = *buf++;
+                if (c[size] == 0x7d)
+                        c[size] = *buf++ ^ 0x20;
+                size++;
+        }
+
+        return probe_kernel_write(mem, c, size);
+}
+
+/*
+ * 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;
+        int negate = 0;
+
+        *long_val = 0;
+
+        if (**ptr == '-') {
+                negate = 1;
+                (*ptr)++;
+        }
+        while (**ptr) {
+                hex_val = hex(**ptr);
+                if (hex_val < 0)
+                        break;
+
+                *long_val = (*long_val << 4) | hex_val;
+                num++;
+                (*ptr)++;
+        }
+
+        if (negate)
+                *long_val = -*long_val;
+
+        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);
+                return 0;
+        }
+
+        return -EINVAL;
+}
+
+static void error_packet(char *pkt, int error)
+{
+        error = -error;
+        pkt[0] = 'E';
+        pkt[1] = hex_asc[(error / 10)];
+        pkt[2] = hex_asc[(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;
+        put_unaligned_be32(value, scan);
+}
+
+static struct task_struct *getthread(struct pt_regs *regs, int tid)
+{
+        /*
+         * Non-positive TIDs are remapped to the cpu shadow information
+         */
+        if (tid == 0 || tid == -1)
+                tid = -atomic_read(&kgdb_active) - 2;
+        if (tid < -1 && tid > -NR_CPUS - 2) {
+                if (kgdb_info[-tid - 2].task)
+                        return kgdb_info[-tid - 2].task;
+                else
+                        return idle_task(-tid - 2);
+        }
+        if (tid <= 0) {
+                printk(KERN_ERR "KGDB: Internal thread select error\n");
+                dump_stack();
+                return NULL;
+        }
+
+        /*
+         * 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);
+}
+
+/*
+ * 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;
+        int ret = 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) {
+                        ret = error;
+                        printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
+                        continue;
+                }
+
+                kgdb_flush_swbreak_addr(addr);
+                kgdb_break[i].state = BP_ACTIVE;
+        }
+        return ret;
+}
+
+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;
+        int ret = 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) {
+                        printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
+                        ret = error;
+                }
+
+                kgdb_flush_swbreak_addr(addr);
+                kgdb_break[i].state = BP_SET;
+        }
+        return ret;
+}
+
+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,
+ * CPU shadow threads are mapped to -CPU - 2
+ */
+static inline int shadow_pid(int realpid)
+{
+        if (realpid)
+                return realpid;
+
+        return -raw_smp_processor_id() - 2;
+}
+
+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_each_online_cpu(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 *g;
+        struct task_struct *p;
+        unsigned char thref[8];
+        char *ptr;
+        int i;
+        int cpu;
+        int finished = 0;
+
+        switch (remcom_in_buffer[1]) {
+        case 's':
+        case 'f':
+                if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10)) {
+                        error_packet(remcom_out_buffer, -EINVAL);
+                        break;
+                }
+
+                i = 0;
+                remcom_out_buffer[0] = 'm';
+                ptr = remcom_out_buffer + 1;
+                if (remcom_in_buffer[1] == 'f') {
+                        /* Each cpu is a shadow thread */
+                        for_each_online_cpu(cpu) {
+                                ks->thr_query = 0;
+                                int_to_threadref(thref, -cpu - 2);
+                                pack_threadid(ptr, thref);
+                                ptr += BUF_THREAD_ID_SIZE;
+                                *(ptr++) = ',';
+                                i++;
+                        }
+                }
+
+                do_each_thread(g, p) {
+                        if (i >= ks->thr_query && !finished) {
+                                int_to_threadref(thref, p->pid);
+                                pack_threadid(ptr, thref);
+                                ptr += BUF_THREAD_ID_SIZE;
+                                *(ptr++) = ',';
+                                ks->thr_query++;
+                                if (ks->thr_query % KGDB_MAX_THREAD_QUERY == 0)
+                                        finished = 1;
+                        }
+                        i++;
+                } while_each_thread(g, p);
+
+                *(--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 ((int)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, "shadowCPU%d",
+                                        (int)(-ks->threadid - 2));
+                        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 {
+                kgdb_msg_write("KGDB only knows signal 9 (pass)"
+                        " and 15 (pass and disconnect)\n"
+                        "Executing a continue without signal passing\n", 0);
+                remcom_in_buffer[0] = 'c';
+        }
+
+        /* 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;
+}
+
+static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
+{
+        unsigned long flags;
+        int sstep_tries = 100;
+        int error = 0;
+        int i, cpu;
+        int trace_on = 0;
+acquirelock:
+        /*
+         * Interrupts will be restored by the 'trap return' code, except when
+         * single stepping.
+         */
+        local_irq_save(flags);
+
+        cpu = ks->cpu;
+        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:
+         */
+        atomic_inc(&cpu_in_kgdb[cpu]);
+
+        /*
+         * CPU will loop if it is a slave or request to become a kgdb
+         * master cpu and acquire the kgdb_active lock:
+         */
+        while (1) {
+                if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
+                        if (atomic_cmpxchg(&kgdb_active, -1, cpu) == cpu)
+                                break;
+                } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
+                        if (!atomic_read(&passive_cpu_wait[cpu]))
+                                goto return_normal;
+                } else {
+return_normal:
+                        /* Return to normal operation by executing any
+                         * hw breakpoint fixup.
+                         */
+                        if (arch_kgdb_ops.correct_hw_break)
+                                arch_kgdb_ops.correct_hw_break();
+                        if (trace_on)
+                                tracing_on();
+                        atomic_dec(&cpu_in_kgdb[cpu]);
+                        touch_softlockup_watchdog_sync();
+                        clocksource_touch_watchdog();
+                        local_irq_restore(flags);
+                        return 0;
+                }
+                cpu_relax();
+        }
+
+        /*
+         * For single stepping, try to only enter on the processor
+         * that was single stepping.  To gaurd against a deadlock, the
+         * kernel will only try for the value of sstep_tries before
+         * giving up and continuing on.
+         */
+        if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
+            (kgdb_info[cpu].task &&
+             kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
+                atomic_set(&kgdb_active, -1);
+                touch_softlockup_watchdog_sync();
+                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_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) {
+                for (i = 0; i < NR_CPUS; i++)
+                        atomic_inc(&passive_cpu_wait[i]);
+        }
+
+#ifdef CONFIG_SMP
+        /* Signal the other CPUs to enter kgdb_wait() */
+        if ((!kgdb_single_step) && 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 = current;
+        exception_level = 0;
+        trace_on = tracing_is_on();
+        if (trace_on)
+                tracing_off();
+
+        /* 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();
+
+        atomic_dec(&cpu_in_kgdb[ks->cpu]);
+
+        if (!kgdb_single_step) {
+                for (i = NR_CPUS-1; i >= 0; i--)
+                        atomic_dec(&passive_cpu_wait[i]);
+                /*
+                 * 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:
+        if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
+                int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
+                if (kgdb_info[sstep_cpu].task)
+                        kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
+                else
+                        kgdb_sstep_pid = 0;
+        }
+        if (trace_on)
+                tracing_on();
+        /* Free kgdb_active */
+        atomic_set(&kgdb_active, -1);
+        touch_softlockup_watchdog_sync();
+        clocksource_touch_watchdog();
+        local_irq_restore(flags);
+
+        return error;
+}
+
+/*
+ * 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;
+        int ret;
+
+        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 ! */
+        kgdb_info[ks->cpu].exception_state |= DCPU_WANT_MASTER;
+        ret = kgdb_cpu_enter(ks, regs);
+        kgdb_info[ks->cpu].exception_state &= ~DCPU_WANT_MASTER;
+        return ret;
+}
+
+int kgdb_nmicallback(int cpu, void *regs)
+{
+#ifdef CONFIG_SMP
+        struct kgdb_state kgdb_var;
+        struct kgdb_state *ks = &kgdb_var;
+
+        memset(ks, 0, sizeof(struct kgdb_state));
+        ks->cpu                 = cpu;
+        ks->linux_regs          = regs;
+
+        if (!atomic_read(&cpu_in_kgdb[cpu]) &&
+            atomic_read(&kgdb_active) != -1 &&
+            atomic_read(&kgdb_active) != cpu) {
+                kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
+                kgdb_cpu_enter(ks, regs);
+                kgdb_info[cpu].exception_state &= ~DCPU_IS_SLAVE;
+                return 0;
+        }
+#endif
+        return 1;
+}
+
+static 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       = "debug(G)",
+        .action_msg     = "DEBUG",
+};
+#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_inc(&kgdb_setting_breakpoint);
+        wmb(); /* Sync point before breakpoint */
+        arch_kgdb_breakpoint();
+        wmb(); /* Sync point after breakpoint */
+        atomic_dec(&kgdb_setting_breakpoint);
+}
+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);