FreeBSD/Linux Kernel Cross Reference
sys/kernel/kgdb.c

     /*
      * 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;
    };
    
    static struct debuggerinfo_struct {
            void                    *debuggerinfo;
            struct task_struct      *task;
    } kgdb_info[NR_CPUS];
    
    /**
     * kgdb_connected - Is a host GDB connected to us?
     */
    int                             kgdb_connected;
    EXPORT_SYMBOL_GPL(kgdb_connected);
    
    /* All the KGDB handlers are installed */
    static int                      kgdb_io_module_registered;
    
    /* Guard for recursive entry */
    static int                      exception_level;
    
    static struct kgdb_io           *kgdb_io_ops;
    static DEFINE_SPINLOCK(kgdb_registration_lock);
    
    /* kgdb console driver is loaded */
    static int kgdb_con_registered;
    /* determine if kgdb console output should be used */
    static int kgdb_use_con;
    
    static int __init opt_kgdb_con(char *str)
    {
            kgdb_use_con = 1;
           return 0;
   }
   
   early_param("kgdbcon", opt_kgdb_con);
   
   module_param(kgdb_use_con, int, 0644);
   
   /*
    * Holds information about breakpoints in a kernel. These breakpoints are
    * added and removed by gdb.
    */
   static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
           [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
   };
   
   /*
    * The CPU# of the active CPU, or -1 if none:
    */
   atomic_t                        kgdb_active = ATOMIC_INIT(-1);
   
   /*
    * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
    * bootup code (which might not have percpu set up yet):
    */
   static atomic_t                 passive_cpu_wait[NR_CPUS];
   static atomic_t                 cpu_in_kgdb[NR_CPUS];
   atomic_t                        kgdb_setting_breakpoint;
   
   struct task_struct              *kgdb_usethread;
   struct task_struct              *kgdb_contthread;
   
   int                             kgdb_single_step;
   
   /* Our I/O buffers. */
   static char                     remcom_in_buffer[BUFMAX];
   static char                     remcom_out_buffer[BUFMAX];
   
   /* Storage for the registers, in GDB format. */
   static unsigned long            gdb_regs[(NUMREGBYTES +
                                           sizeof(unsigned long) - 1) /
                                           sizeof(unsigned long)];
   
   /* to keep track of the CPU which is doing the single stepping*/
   atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
   
   /*
    * If you are debugging a problem where roundup (the collection of
    * all other CPUs) is a problem [this should be extremely rare],
    * then use the nokgdbroundup option to avoid roundup. In that case
    * the other CPUs might interfere with your debugging context, so
    * use this with care:
    */
   static int kgdb_do_roundup = 1;
   
   static int __init opt_nokgdbroundup(char *str)
   {
           kgdb_do_roundup = 0;
   
           return 0;
   }
   
   early_param("nokgdbroundup", opt_nokgdbroundup);
   
   /*
    * Finally, some KGDB code :-)
    */
   
   /*
    * Weak aliases for breakpoint management,
    * can be overriden by architectures when needed:
    */
   int __weak kgdb_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 >= '') && (ch <= '9'))
                   return ch - '';
           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 a pointer to the character after
    * the last byte written.
    */
   static int kgdb_ebin2mem(char *buf, char *mem, int count)
   {
           int err = 0;
           char c;
   
           while (count-- > 0) {
                   c = *buf++;
                   if (c == 0x7d)
                           c = *buf++ ^ 0x20;
   
                   err = probe_kernel_write(mem, &c, 1);
                   if (err)
                           break;
   
                   mem++;
           }
   
           return err;
   }
   
   /*
    * Convert the hex array pointed to by buf into binary to be placed in mem.
    * Return a pointer to the character AFTER the last byte written.
    * May return an error.
    */
   int kgdb_hex2mem(char *buf, char *mem, int count)
   {
           char *tmp_raw;
           char *tmp_hex;
   
           /*
            * We use the upper half of buf as an intermediate buffer for the
            * raw memory that is converted from hex.
            */
           tmp_raw = buf + count * 2;
   
           tmp_hex = tmp_raw - 1;
           while (tmp_hex >= buf) {
                   tmp_raw--;
                   *tmp_raw = hex(*tmp_hex--);
                   *tmp_raw |= hex(*tmp_hex--) << 4;
           }
   
           return probe_kernel_write(mem, tmp_raw, count);
   }
   
   /*
    * While we find nice hex chars, build a long_val.
    * Return number of chars processed.
    */
   int kgdb_hex2long(char **ptr, unsigned long *long_val)
   {
           int hex_val;
           int num = 0;
           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 < 0) {
                   if (kgdb_info[-tid - 2].task)
                           return kgdb_info[-tid - 2].task;
                   else
                           return idle_task(-tid - 2);
           }
   
           /*
            * 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);
           touch_softlockup_watchdog();
           clocksource_touch_watchdog();
           local_irq_restore(flags);
   }
   #endif
   
   /*
    * Some architectures need cache flushes when we set/clear a
    * breakpoint:
    */
   static void kgdb_flush_swbreak_addr(unsigned long addr)
   {
           if (!CACHE_FLUSH_IS_SAFE)
                   return;
   
           if (current->mm && current->mm->mmap_cache) {
                   flush_cache_range(current->mm->mmap_cache,
                                     addr, addr + BREAK_INSTR_SIZE);
           }
           /* Force flush instruction cache if it was outside the mm */
           flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
   }
   
   /*
    * SW breakpoint management:
    */
   static int kgdb_activate_sw_breakpoints(void)
   {
           unsigned long addr;
           int error = 0;
           int i;
   
           for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
                   if (kgdb_break[i].state != BP_SET)
                           continue;
   
                   addr = kgdb_break[i].bpt_addr;
                   error = kgdb_arch_set_breakpoint(addr,
                                   kgdb_break[i].saved_instr);
                   if (error)
                           return error;
   
                   kgdb_flush_swbreak_addr(addr);
                   kgdb_break[i].state = BP_ACTIVE;
           }
           return 0;
   }
   
   static int kgdb_set_sw_break(unsigned long addr)
   {
           int err = kgdb_validate_break_address(addr);
           int breakno = -1;
           int i;
   
           if (err)
                   return err;
   
           for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
                   if ((kgdb_break[i].state == BP_SET) &&
                                           (kgdb_break[i].bpt_addr == addr))
                           return -EEXIST;
           }
           for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
                   if (kgdb_break[i].state == BP_REMOVED &&
                                           kgdb_break[i].bpt_addr == addr) {
                           breakno = i;
                           break;
                   }
           }
   
           if (breakno == -1) {
                   for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
                           if (kgdb_break[i].state == BP_UNDEFINED) {
                                   breakno = i;
                                   break;
                           }
                   }
           }
   
           if (breakno == -1)
                   return -E2BIG;
   
           kgdb_break[breakno].state = BP_SET;
           kgdb_break[breakno].type = BP_BREAKPOINT;
           kgdb_break[breakno].bpt_addr = addr;
   
           return 0;
   }
   
   static int kgdb_deactivate_sw_breakpoints(void)
   {
           unsigned long addr;
           int error = 0;
           int i;
   
           for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
                   if (kgdb_break[i].state != BP_ACTIVE)
                           continue;
                   addr = kgdb_break[i].bpt_addr;
                   error = kgdb_arch_remove_breakpoint(addr,
                                           kgdb_break[i].saved_instr);
                   if (error)
                           return error;
   
                   kgdb_flush_swbreak_addr(addr);
                   kgdb_break[i].state = BP_SET;
           }
           return 0;
   }
   
   static int kgdb_remove_sw_break(unsigned long addr)
   {
           int i;
   
           for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
                   if ((kgdb_break[i].state == BP_SET) &&
                                   (kgdb_break[i].bpt_addr == addr)) {
                           kgdb_break[i].state = BP_REMOVED;
                           return 0;
                   }
           }
           return -ENOENT;
   }
   
   int kgdb_isremovedbreak(unsigned long addr)
   {
           int i;
   
           for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
                   if ((kgdb_break[i].state == BP_REMOVED) &&
                                           (kgdb_break[i].bpt_addr == addr))
                           return 1;
           }
           return 0;
   }
   
   static int remove_all_break(void)
   {
           unsigned long addr;
           int error;
           int i;
   
           /* Clear memory breakpoints. */
           for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
                   if (kgdb_break[i].state != BP_ACTIVE)
                           goto setundefined;
                   addr = kgdb_break[i].bpt_addr;
                   error = kgdb_arch_remove_breakpoint(addr,
                                   kgdb_break[i].saved_instr);
                   if (error)
                           printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
                              addr);
   setundefined:
                   kgdb_break[i].state = BP_UNDEFINED;
           }
   
           /* Clear hardware breakpoints. */
           if (arch_kgdb_ops.remove_all_hw_break)
                   arch_kgdb_ops.remove_all_hw_break();
   
           return 0;
   }
   
   /*
    * Remap normal tasks to their real PID,
    * 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 '' 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 != '' && *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 == '')
                  error = kgdb_set_sw_break(addr);
          else if (remcom_in_buffer[0] == 'z' && *bpt_type == '')
                  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 - '');
          else if (remcom_in_buffer[0] == 'z')
                  error = arch_kgdb_ops.remove_hw_breakpoint(addr,
                          (int) length, *bpt_type - '');
  
          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] == '' && 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);
                  touch_softlockup_watchdog();
                  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) {
                  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_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;
  
          /* 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) {
                  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);
          touch_softlockup_watchdog();
          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;
  }
  
  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_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);

Cache object: f38808615911715d1c14ee4a7ab66369