2.6.26-rc1

 kernel

diff --git a/kernel/kgdb.c b/kernel/kgdb.c
new file mode 100644
index 0000000..1bd0ec1
--- /dev/null
+++ b/kernel/kgdb.c
@@ -0,0 +1,1700 @@
+/*
+ * 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;
+   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:
+ */
+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;
+      }
+   }
+}
+
+static char *pack_hex_byte(char *pkt, u8 byte)
+{
+   *pkt++ = hexchars[byte >> 4];
+   *pkt++ = hexchars[byte & 0xf];
+
+   return pkt;
+}
+
+/*
+ * 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, 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;
+}
+
+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);