1 files changed, 57 insertions, 433 deletions

diff --git a/arch/sh/kernel/kgdb_stub.c b/arch/sh/kernel/kgdb_stub.c
index d8927d85492e..a5323364cbca 100644
--- a/arch/sh/kernel/kgdb_stub.c
+++ b/arch/sh/kernel/kgdb_stub.c
@@ -6,11 +6,11 @@
  * David Grothe <dave@gcom.com>, Tigran Aivazian <tigran@sco.com>,
  * Amit S. Kale <akale@veritas.com>,  William Gatliff <bgat@open-widgets.com>,
  * Ben Lee, Steve Chamberlain and Benoit Miller <fulg@iname.com>.
- * 
+ *
  * This version by Henry Bell <henry.bell@st.com>
  * Minor modifications by Jeremy Siegel <jsiegel@mvista.com>
- * 
- * Contains low-level support for remote debug using GDB. 
+ *
+ * Contains low-level support for remote debug using GDB.
  *
  * To enable debugger support, two things need to happen. A call to
  * set_debug_traps() is necessary in order to allow any breakpoints
@@ -48,7 +48,7 @@
  *    k             kill (Detach GDB)
  *
  *    d             Toggle debug flag
- *    D             Detach GDB 
+ *    D             Detach GDB
  *
  *    Hct           Set thread t for operations,           OK or ENN
  *                  c = 'c' (step, cont), c = 'g' (other
@@ -58,7 +58,7 @@
  *    qfThreadInfo  Get list of current threads (first)    m<id>
  *    qsThreadInfo   "    "  "     "      "   (subsequent)
  *    qOffsets      Get section offsets                  Text=x;Data=y;Bss=z
- * 
+ *
  *    TXX           Find if thread XX is alive             OK or ENN
  *    ?             What was the last sigval ?             SNN   (signal NN)
  *    O             Output to GDB console
@@ -74,7 +74,7 @@
  *       '$' or '#'.  If <data> starts with two characters followed by
  *       ':', then the existing stubs interpret this as a sequence number.
  *
- *       CSUM1 and CSUM2 are ascii hex representation of an 8-bit 
+ *       CSUM1 and CSUM2 are ascii hex representation of an 8-bit
  *       checksum of <data>, the most significant nibble is sent first.
  *       the hex digits 0-9,a-f are used.
  *
@@ -86,8 +86,8 @@
  * Responses can be run-length encoded to save space.  A '*' means that
  * the next character is an ASCII encoding giving a repeat count which
  * stands for that many repititions of the character preceding the '*'.
- * The encoding is n+29, yielding a printable character where n >=3 
- * (which is where RLE starts to win).  Don't use an n > 126. 
+ * The encoding is n+29, yielding a printable character where n >=3
+ * (which is where RLE starts to win).  Don't use an n > 126.
  *
  * So "0* " means the same as "0000".
  */
@@ -100,12 +100,10 @@
 #include <linux/delay.h>
 #include <linux/linkage.h>
 #include <linux/init.h>
-
-#ifdef CONFIG_SH_KGDB_CONSOLE
 #include <linux/console.h>
-#endif
-
+#include <linux/sysrq.h>
 #include <asm/system.h>
+#include <asm/cacheflush.h>
 #include <asm/current.h>
 #include <asm/signal.h>
 #include <asm/pgtable.h>
@@ -153,7 +151,6 @@ char kgdb_in_gdb_mode;
 char in_nmi;                    /* Set during NMI to prevent reentry */
 int kgdb_nofault;               /* Boolean to ignore bus errs (i.e. in GDB) */
 int kgdb_enabled = 1;           /* Default to enabled, cmdline can disable */
-int kgdb_halt;
 
 /* Exposed for user access */
 struct task_struct *kgdb_current;
@@ -246,14 +243,6 @@ static char out_buffer[OUTBUFMAX];
 
 static void kgdb_to_gdb(const char *s);
 
-#ifdef CONFIG_KGDB_THREAD
-static struct task_struct *trapped_thread;
-static struct task_struct *current_thread;
-typedef unsigned char threadref[8];
-#define BUF_THREAD_ID_SIZE 16
-#endif
-
-
 /* Convert ch to hex */
 static int hex(const char ch)
 {
@@ -328,7 +317,7 @@ static int hex_to_int(char **ptr, int *int_value)
 }
 
 /*  Copy the binary array pointed to by buf into mem.  Fix $, #,
-    and 0x7d escaped with 0x7d.  Return a pointer to the character 
+    and 0x7d escaped with 0x7d.  Return a pointer to the character
     after the last byte written. */
 static char *ebin_to_mem(const char *buf, char *mem, int count)
 {
@@ -349,66 +338,6 @@ static char *pack_hex_byte(char *pkt, int byte)
         return pkt;
 }
 
-#ifdef CONFIG_KGDB_THREAD
-
-/* Pack a thread ID */
-static char *pack_threadid(char *pkt, threadref * id)
-{
-        char *limit;
-        unsigned char *altid;
-
-        altid = (unsigned char *) id;
-
-        limit = pkt + BUF_THREAD_ID_SIZE;
-        while (pkt < limit)
-                pkt = pack_hex_byte(pkt, *altid++);
-        return pkt;
-}
-
-/* Convert an integer into our threadref */
-static void int_to_threadref(threadref * id, const int value)
-{
-        unsigned char *scan = (unsigned char *) id;
-        int i = 4;
-
-        while (i--)
-                *scan++ = 0;
-
-        *scan++ = (value >> 24) & 0xff;
-        *scan++ = (value >> 16) & 0xff;
-        *scan++ = (value >> 8) & 0xff;
-        *scan++ = (value & 0xff);
-}
-
-/* Return a task structure ptr for a particular pid */
-static struct task_struct *get_thread(int pid)
-{
-        struct task_struct *thread;
-
-        /* Use PID_MAX w/gdb for pid 0 */
-        if (pid == PID_MAX) pid = 0;
-
-        /* First check via PID */
-        thread = find_task_by_pid(pid);
-
-        if (thread)
-                return thread;
-
-        /* Start at the start */
-        thread = init_tasks[0];
-
-        /* Walk along the linked list of tasks */
-        do {
-                if (thread->pid == pid)
-                        return thread;
-                thread = thread->next_task;
-        } while (thread != init_tasks[0]);
-
-        return NULL;
-}
-
-#endif /* CONFIG_KGDB_THREAD */
-
 /* Scan for the start char '$', read the packet and check the checksum */
 static void get_packet(char *buffer, int buflen)
 {
@@ -452,7 +381,7 @@ static void get_packet(char *buffer, int buflen)
                                 /* Ack successful transfer */
                                 put_debug_char('+');
 
-                                /* If a sequence char is present, reply 
+                                /* If a sequence char is present, reply
                                    the sequence ID */
                                 if (buffer[2] == ':') {
                                         put_debug_char(buffer[0]);
@@ -611,74 +540,6 @@ static void gdb_regs_to_kgdb_regs(const int *gdb_regs,
         regs->vbr = gdb_regs[VBR];
 }
 
-#ifdef CONFIG_KGDB_THREAD
-/* Make a local copy of registers from the specified thread */
-asmlinkage void ret_from_fork(void);
-static void thread_regs_to_gdb_regs(const struct task_struct *thread,
-                                    int *gdb_regs)
-{
-        int regno;
-        int *tregs;
-
-        /* Initialize to zero */
-        for (regno = 0; regno < MAXREG; regno++)
-                gdb_regs[regno] = 0;
-
-        /* Just making sure... */
-        if (thread == NULL)
-                return;
-
-        /* A new fork has pt_regs on the stack from a fork() call */
-        if (thread->thread.pc == (unsigned long)ret_from_fork) {
-
-                int vbr_val;
-                struct pt_regs *kregs;
-                kregs = (struct pt_regs*)thread->thread.sp;
-
-                gdb_regs[R0] = kregs->regs[R0];
-                gdb_regs[R1] = kregs->regs[R1];
-                gdb_regs[R2] = kregs->regs[R2];
-                gdb_regs[R3] = kregs->regs[R3];
-                gdb_regs[R4] = kregs->regs[R4];
-                gdb_regs[R5] = kregs->regs[R5];
-                gdb_regs[R6] = kregs->regs[R6];
-                gdb_regs[R7] = kregs->regs[R7];
-                gdb_regs[R8] = kregs->regs[R8];
-                gdb_regs[R9] = kregs->regs[R9];
-                gdb_regs[R10] = kregs->regs[R10];
-                gdb_regs[R11] = kregs->regs[R11];
-                gdb_regs[R12] = kregs->regs[R12];
-                gdb_regs[R13] = kregs->regs[R13];
-                gdb_regs[R14] = kregs->regs[R14];
-                gdb_regs[R15] = kregs->regs[R15];
-                gdb_regs[PC] = kregs->pc;
-                gdb_regs[PR] = kregs->pr;
-                gdb_regs[GBR] = kregs->gbr;
-                gdb_regs[MACH] = kregs->mach;
-                gdb_regs[MACL] = kregs->macl;
-                gdb_regs[SR] = kregs->sr;
-
-                asm("stc vbr, %0":"=r"(vbr_val));
-                gdb_regs[VBR] = vbr_val;
-                return;
-        }
-
-        /* Otherwise, we have only some registers from switch_to() */
-        tregs = (int *)thread->thread.sp;
-        gdb_regs[R15] = (int)tregs;
-        gdb_regs[R14] = *tregs++;
-        gdb_regs[R13] = *tregs++;
-        gdb_regs[R12] = *tregs++;
-        gdb_regs[R11] = *tregs++;
-        gdb_regs[R10] = *tregs++;
-        gdb_regs[R9] = *tregs++;
-        gdb_regs[R8] = *tregs++;
-        gdb_regs[PR] = *tregs++;
-        gdb_regs[GBR] = *tregs++;
-        gdb_regs[PC] = thread->thread.pc;
-}
-#endif /* CONFIG_KGDB_THREAD */
-
 /* Calculate the new address for after a step */
 static short *get_step_address(void)
 {
@@ -759,7 +620,7 @@ static short *get_step_address(void)
         return (short *) addr;
 }
 
-/* Set up a single-step.  Replace the instruction immediately after the 
+/* Set up a single-step.  Replace the instruction immediately after the
    current instruction (i.e. next in the expected flow of control) with a
    trap instruction, so that returning will cause only a single instruction
    to be executed. Note that this model is slightly broken for instructions
@@ -797,37 +658,11 @@ static void undo_single_step(void)
 /* Send a signal message */
 static void send_signal_msg(const int signum)
 {
-#ifndef CONFIG_KGDB_THREAD
         out_buffer[0] = 'S';
         out_buffer[1] = highhex(signum);
         out_buffer[2] = lowhex(signum);
         out_buffer[3] = 0;
         put_packet(out_buffer);
-#else /* CONFIG_KGDB_THREAD */
-        int threadid;
-        threadref thref;
-        char *out = out_buffer;
-        const char *tstring = "thread";
-
-        *out++ = 'T';
-        *out++ = highhex(signum);
-        *out++ = lowhex(signum);
-
-        while (*tstring) {
-                *out++ = *tstring++;
-        }
-        *out++ = ':';
-
-        threadid = trapped_thread->pid;
-        if (threadid == 0) threadid = PID_MAX;
-        int_to_threadref(&thref, threadid);
-        pack_threadid(out, &thref);
-        out += BUF_THREAD_ID_SIZE;
-        *out++ = ';';
-
-        *out = 0;
-        put_packet(out_buffer);
-#endif /* CONFIG_KGDB_THREAD */
 }
 
 /* Reply that all was well */
@@ -962,15 +797,7 @@ static void step_with_sig_msg(void)
 /* Send register contents */
 static void send_regs_msg(void)
 {
-#ifdef CONFIG_KGDB_THREAD
-        if (!current_thread)
-                kgdb_regs_to_gdb_regs(&trap_registers, registers);
-        else
-                thread_regs_to_gdb_regs(current_thread, registers);
-#else
         kgdb_regs_to_gdb_regs(&trap_registers, registers);
-#endif
-
         mem_to_hex((char *) registers, out_buffer, NUMREGBYTES);
         put_packet(out_buffer);
 }
@@ -978,201 +805,13 @@ static void send_regs_msg(void)
 /* Set register contents - currently can't set other thread's registers */
 static void set_regs_msg(void)
 {
-#ifdef CONFIG_KGDB_THREAD
-        if (!current_thread) {
-#endif
-                kgdb_regs_to_gdb_regs(&trap_registers, registers);
-                hex_to_mem(&in_buffer[1], (char *) registers, NUMREGBYTES);
-                gdb_regs_to_kgdb_regs(registers, &trap_registers);
-                send_ok_msg();
-#ifdef CONFIG_KGDB_THREAD
-        } else
-                send_err_msg();
-#endif
-}
-
-
-#ifdef CONFIG_KGDB_THREAD
-
-/* Set the status for a thread */
-void set_thread_msg(void)
-{
-        int threadid;
-        struct task_struct *thread = NULL;
-        char *ptr;
-
-        switch (in_buffer[1]) {
-
-        /* To select which thread for gG etc messages, i.e. supported */
-        case 'g':
-
-                ptr = &in_buffer[2];
-                hex_to_int(&ptr, &threadid);
-                thread = get_thread(threadid);
-
-                /* If we haven't found it */
-                if (!thread) {
-                        send_err_msg();
-                        break;
-                }
-
-                /* Set current_thread (or not) */
-                if (thread == trapped_thread)
-                        current_thread = NULL;
-                else
-                        current_thread = thread;
-                send_ok_msg();
-                break;
-
-        /* To select which thread for cCsS messages, i.e. unsupported */
-        case 'c':
-                send_ok_msg();
-                break;
-
-        default:
-                send_empty_msg();
-                break;
-        }
-}
-
-/* Is a thread alive? */
-static void thread_status_msg(void)
-{
-        char *ptr;
-        int threadid;
-        struct task_struct *thread = NULL;
-
-        ptr = &in_buffer[1];
-        hex_to_int(&ptr, &threadid);
-        thread = get_thread(threadid);
-        if (thread)
-                send_ok_msg();
-        else
-                send_err_msg();
-}
-/* Send the current thread ID */
-static void thread_id_msg(void)
-{
-        int threadid;
-        threadref thref;
-
-        out_buffer[0] = 'Q';
-        out_buffer[1] = 'C';
-
-        if (current_thread)
-                threadid = current_thread->pid;
-        else if (trapped_thread)
-                threadid = trapped_thread->pid;
-        else /* Impossible, but just in case! */
-        {
-                send_err_msg();
-                return;
-        }
-
-        /* Translate pid 0 to PID_MAX for gdb */
-        if (threadid == 0) threadid = PID_MAX;
-
-        int_to_threadref(&thref, threadid);
-        pack_threadid(out_buffer + 2, &thref);
-        out_buffer[2 + BUF_THREAD_ID_SIZE] = '\0';
-        put_packet(out_buffer);
-}
-
-/* Send thread info */
-static void thread_info_msg(void)
-{
-        struct task_struct *thread = NULL;
-        int threadid;
-        char *pos;
-        threadref thref;
-
-        /* Start with 'm' */
-        out_buffer[0] = 'm';
-        pos = &out_buffer[1];
-
-        /* For all possible thread IDs - this will overrun if > 44 threads! */
-        /* Start at 1 and include PID_MAX (since GDB won't use pid 0...) */
-        for (threadid = 1; threadid <= PID_MAX; threadid++) {
-
-                read_lock(&tasklist_lock);
-                thread = get_thread(threadid);
-                read_unlock(&tasklist_lock);
-
-                /* If it's a valid thread */
-                if (thread) {
-                        int_to_threadref(&thref, threadid);
-                        pack_threadid(pos, &thref);
-                        pos += BUF_THREAD_ID_SIZE;
-                        *pos++ = ',';
-                }
-        }
-        *--pos = 0;             /* Lose final comma */
-        put_packet(out_buffer);
-
-}
-
-/* Return printable info for gdb's 'info threads' command */
-static void thread_extra_info_msg(void)
-{
-        int threadid;
-        struct task_struct *thread = NULL;
-        char buffer[20], *ptr;
-        int i;
-
-        /* Extract thread ID */
-        ptr = &in_buffer[17];
-        hex_to_int(&ptr, &threadid);
-        thread = get_thread(threadid);
-
-        /* If we don't recognise it, say so */
-        if (thread == NULL)
-                strcpy(buffer, "(unknown)");
-        else
-                strcpy(buffer, thread->comm);
-
-        /* Construct packet */
-        for (i = 0, ptr = out_buffer; buffer[i]; i++)
-                ptr = pack_hex_byte(ptr, buffer[i]);
-
-        if (thread->thread.pc == (unsigned long)ret_from_fork) {
-                strcpy(buffer, "<new fork>");
-                for (i = 0; buffer[i]; i++)
-                        ptr = pack_hex_byte(ptr, buffer[i]);
-        }
-
-        *ptr = '\0';
-        put_packet(out_buffer);
-}
-
-/* Handle all qFooBarBaz messages - have to use an if statement as
-   opposed to a switch because q messages can have > 1 char id. */
-static void query_msg(void)
-{
-        const char *q_start = &in_buffer[1];
-
-        /* qC = return current thread ID */
-        if (strncmp(q_start, "C", 1) == 0)
-                thread_id_msg();
-
-        /* qfThreadInfo = query all threads (first) */
-        else if (strncmp(q_start, "fThreadInfo", 11) == 0)
-                thread_info_msg();
-
-        /* qsThreadInfo = query all threads (subsequent). We know we have sent
-           them all after the qfThreadInfo message, so there are no to send */
-        else if (strncmp(q_start, "sThreadInfo", 11) == 0)
-                put_packet("l");        /* el = last */
-
-        /* qThreadExtraInfo = supply printable information per thread */
-        else if (strncmp(q_start, "ThreadExtraInfo", 15) == 0)
-                thread_extra_info_msg();
-
-        /* Unsupported - empty message as per spec */
-        else
-                send_empty_msg();
+        kgdb_regs_to_gdb_regs(&trap_registers, registers);
+        hex_to_mem(&in_buffer[1], (char *) registers, NUMREGBYTES);
+        gdb_regs_to_kgdb_regs(registers, &trap_registers);
+        send_ok_msg();
 }
-#endif /* CONFIG_KGDB_THREAD */
 
+#ifdef CONFIG_SH_KGDB_CONSOLE
 /*
  * Bring up the ports..
  */
@@ -1185,6 +824,9 @@ static int kgdb_serial_setup(void)
 
         return 0;
 }
+#else
+#define kgdb_serial_setup()     0
+#endif
 
 /* The command loop, read and act on requests */
 static void kgdb_command_loop(const int excep_code, const int trapa_value)
@@ -1193,7 +835,7 @@ static void kgdb_command_loop(const int excep_code, const int trapa_value)
 
         if (excep_code == NMI_VEC) {
 #ifndef CONFIG_KGDB_NMI
-                KGDB_PRINTK("Ignoring unexpected NMI?\n");
+                printk(KERN_NOTICE "KGDB: Ignoring unexpected NMI?\n");
                 return;
 #else /* CONFIG_KGDB_NMI */
                 if (!kgdb_enabled) {
@@ -1207,19 +849,10 @@ static void kgdb_command_loop(const int excep_code, const int trapa_value)
         if (!kgdb_enabled)
                 return;
 
-#ifdef CONFIG_KGDB_THREAD
-        /* Until GDB specifies a thread */
-        current_thread = NULL;
-        trapped_thread = current;
-#endif
-
         /* Enter GDB mode (e.g. after detach) */
         if (!kgdb_in_gdb_mode) {
                 /* Do serial setup, notify user, issue preemptive ack */
-                kgdb_serial_setup();
-                KGDB_PRINTK("Waiting for GDB (on %s%d at %d baud)\n",
-                            (kgdb_porttype ? kgdb_porttype->name : ""),
-                            kgdb_portnum, kgdb_baud);
+                printk(KERN_NOTICE "KGDB: Waiting for GDB\n");
                 kgdb_in_gdb_mode = 1;
                 put_debug_char('+');
         }
@@ -1233,21 +866,18 @@ static void kgdb_command_loop(const int excep_code, const int trapa_value)
            will later be replaced by its original one.  Do NOT do this for
            trap 0xff, since that indicates a compiled-in breakpoint which
            will not be replaced (and we would retake the trap forever) */
-        if ((excep_code == TRAP_VEC) && (trapa_value != (0xff << 2))) {
+        if ((excep_code == TRAP_VEC) && (trapa_value != (0x3c << 2)))
                 trap_registers.pc -= 2;
-        }
 
         /* Undo any stepping we may have done */
         undo_single_step();
 
         while (1) {
-
                 out_buffer[0] = 0;
                 get_packet(in_buffer, BUFMAX);
 
                 /* Examine first char of buffer to see what we need to do */
                 switch (in_buffer[0]) {
-
                 case '?':       /* Send which signal we've received */
                         send_signal_msg(sigval);
                         break;
@@ -1291,21 +921,6 @@ static void kgdb_command_loop(const int excep_code, const int trapa_value)
                         step_msg();
                         return;
 
-#ifdef CONFIG_KGDB_THREAD
-
-                case 'H':       /* Task related */
-                        set_thread_msg();
-                        break;
-
-                case 'T':       /* Query thread status */
-                        thread_status_msg();
-                        break;
-
-                case 'q':       /* Handle query - currently thread-related */
-                        query_msg();
-                        break;
-#endif
-
                 case 'k':       /* 'Kill the program' with a kernel ? */
                         break;
 
@@ -1323,11 +938,8 @@ static void kgdb_command_loop(const int excep_code, const int trapa_value)
 }
 
 /* There has been an exception, most likely a breakpoint. */
-asmlinkage void kgdb_handle_exception(unsigned long r4, unsigned long r5,
-                                      unsigned long r6, unsigned long r7,
-                                      struct pt_regs __regs)
+static void handle_exception(struct pt_regs *regs)
 {
-        struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
         int excep_code, vbr_val;
         int count;
         int trapa_value = ctrl_inl(TRA);
@@ -1355,7 +967,7 @@ asmlinkage void kgdb_handle_exception(unsigned long r4, unsigned long r5,
         kgdb_trapa_val = trapa_value;
 
         /* Act on the exception */
-        kgdb_command_loop(excep_code >> 5, trapa_value);
+        kgdb_command_loop(excep_code, trapa_value);
 
         kgdb_current = NULL;
 
@@ -1373,14 +985,12 @@ asmlinkage void kgdb_handle_exception(unsigned long r4, unsigned long r5,
         asm("ldc %0, vbr": :"r"(vbr_val));
 }
 
-/* Trigger a breakpoint by function */
-void breakpoint(void)
+asmlinkage void kgdb_handle_exception(unsigned long r4, unsigned long r5,
+                                      unsigned long r6, unsigned long r7,
+                                      struct pt_regs __regs)
 {
-        if (!kgdb_enabled) {
-                kgdb_enabled = 1;
-                kgdb_init();
-        }
-        BREAKPOINT();
+        struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
+        handle_exception(regs);
 }
 
 /* Initialise the KGDB data structures and serial configuration */
@@ -1395,24 +1005,16 @@ int kgdb_init(void)
         kgdb_in_gdb_mode = 0;
 
         if (kgdb_serial_setup() != 0) {
-                KGDB_PRINTK("serial setup error\n");
+                printk(KERN_NOTICE "KGDB: serial setup error\n");
                 return -1;
         }
 
         /* Init ptr to exception handler */
-        kgdb_debug_hook = kgdb_handle_exception;
+        kgdb_debug_hook = handle_exception;
         kgdb_bus_err_hook = kgdb_handle_bus_error;
 
         /* Enter kgdb now if requested, or just report init done */
-        if (kgdb_halt) {
-                kgdb_in_gdb_mode = 1;
-                put_debug_char('+');
-                breakpoint();
-        }
-        else
-        {
-                KGDB_PRINTK("stub is initialized.\n");
-        }
+        printk(KERN_NOTICE "KGDB: stub is initialized.\n");
 
         return 0;
 }
@@ -1437,7 +1039,7 @@ static void kgdb_msg_write(const char *s, unsigned count)
 
                 /* Calculate how many this time */
                 wcount = (count > MAXOUT) ? MAXOUT : count;
-                
+
                 /* Pack in hex chars */
                 for (i = 0; i < wcount; i++)
                         bufptr = pack_hex_byte(bufptr, s[i]);
@@ -1467,3 +1069,25 @@ void kgdb_console_write(struct console *co, const char *s, unsigned count)
         kgdb_msg_write(s, count);
 }
 #endif
+
+#ifdef CONFIG_KGDB_SYSRQ
+static void sysrq_handle_gdb(int key, struct tty_struct *tty)
+{
+        printk("Entering GDB stub\n");
+        breakpoint();
+}
+
+static struct sysrq_key_op sysrq_gdb_op = {
+        .handler        = sysrq_handle_gdb,
+        .help_msg       = "Gdb",
+        .action_msg     = "GDB",
+};
+
+static int gdb_register_sysrq(void)
+{
+        printk("Registering GDB sysrq handler\n");
+        register_sysrq_key('g', &sysrq_gdb_op);
+        return 0;
+}
+module_init(gdb_register_sysrq);
+#endif