/* MN10300 GDB stub
 *
 * Originally written by Glenn Engel, Lake Stevens Instrument Division
 *
 * Contributed by HP Systems
 *
 * Modified for SPARC by Stu Grossman, Cygnus Support.
 *
 * Modified for Linux/MIPS (and MIPS in general) by Andreas Busse
 * Send complaints, suggestions etc. to <andy@waldorf-gmbh.de>
 *
 * Copyright (C) 1995 Andreas Busse
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Modified for Linux/mn10300 by David Howells <dhowells@redhat.com>
 */

/*
 *  To enable debugger support, two things need to happen.  One, a
 *  call to set_debug_traps() is necessary in order to allow any breakpoints
 *  or error conditions to be properly intercepted and reported to gdb.
 *  Two, a breakpoint needs to be generated to begin communication.  This
 *  is most easily accomplished by a call to breakpoint().  Breakpoint()
 *  simulates a breakpoint by executing a BREAK instruction.
 *
 *
 *    The following gdb commands are supported:
 *
 * command          function                               Return value
 *
 *    g             return the value of the CPU registers  hex data or ENN
 *    G             set the value of the CPU registers     OK or ENN
 *
 *    mAA..AA,LLLL  Read LLLL bytes at address AA..AA      hex data or ENN
 *    MAA..AA,LLLL: Write LLLL bytes at address AA.AA      OK or ENN
 *
 *    c             Resume at current address              SNN   ( signal NN)
 *    cAA..AA       Continue at address AA..AA             SNN
 *
 *    s             Step one instruction                   SNN
 *    sAA..AA       Step one instruction from AA..AA       SNN
 *
 *    k             kill
 *
 *    ?             What was the last sigval ?             SNN   (signal NN)
 *
 *    bBB..BB       Set baud rate to BB..BB                OK or BNN, then sets
 *                                                         baud rate
 *
 * All commands and responses are sent with a packet which includes a
 * checksum.  A packet consists of
 *
 * $<packet info>#<checksum>.
 *
 * where
 * <packet info> :: <characters representing the command or response>
 * <checksum>    :: < two hex digits computed as modulo 256 sum of <packetinfo>>
 *
 * When a packet is received, it is first acknowledged with either '+' or '-'.
 * '+' indicates a successful transfer.  '-' indicates a failed transfer.
 *
 * Example:
 *
 * Host:                  Reply:
 * $m0,10#2a               +$00010203040506070809101112131415#42
 *
 *
 *  ==============
 *  MORE EXAMPLES:
 *  ==============
 *
 *  For reference -- the following are the steps that one
 *  company took (RidgeRun Inc) to get remote gdb debugging
 *  going. In this scenario the host machine was a PC and the
 *  target platform was a Galileo EVB64120A MIPS evaluation
 *  board.
 *
 *  Step 1:
 *  First download gdb-5.0.tar.gz from the internet.
 *  and then build/install the package.
 *
 *  Example:
 *    $ tar zxf gdb-5.0.tar.gz
 *    $ cd gdb-5.0
 *    $ ./configure --target=am33_2.0-linux-gnu
 *    $ make
 *    $ install
 *    am33_2.0-linux-gnu-gdb
 *
 *  Step 2:
 *  Configure linux for remote debugging and build it.
 *
 *  Example:
 *    $ cd ~/linux
 *    $ make menuconfig <go to "Kernel Hacking" and turn on remote debugging>
 *    $ make dep; make vmlinux
 *
 *  Step 3:
 *  Download the kernel to the remote target and start
 *  the kernel running. It will promptly halt and wait
 *  for the host gdb session to connect. It does this
 *  since the "Kernel Hacking" option has defined
 *  CONFIG_REMOTE_DEBUG which in turn enables your calls
 *  to:
 *     set_debug_traps();
 *     breakpoint();
 *
 *  Step 4:
 *  Start the gdb session on the host.
 *
 *  Example:
 *    $ am33_2.0-linux-gnu-gdb vmlinux
 *    (gdb) set remotebaud 115200
 *    (gdb) target remote /dev/ttyS1
 *    ...at this point you are connected to
 *       the remote target and can use gdb
 *       in the normal fasion. Setting
 *       breakpoints, single stepping,
 *       printing variables, etc.
 *
 */

#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/console.h>
#include <linux/init.h>
#include <linux/bug.h>

#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/gdb-stub.h>
#include <asm/exceptions.h>
#include <asm/debugger.h>
#include <asm/serial-regs.h>
#include <asm/busctl-regs.h>
#include <unit/leds.h>
#include <unit/serial.h>

/* define to use F7F7 rather than FF which is subverted by JTAG debugger */
#undef GDBSTUB_USE_F7F7_AS_BREAKPOINT

/*
 * BUFMAX defines the maximum number of characters in inbound/outbound buffers
 * at least NUMREGBYTES*2 are needed for register packets
 */
#define BUFMAX 2048

static const char gdbstub_banner[] =
        "Linux/MN10300 GDB Stub (c) RedHat 2007\n";

u8      gdbstub_rx_buffer[PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
u32     gdbstub_rx_inp;
u32     gdbstub_rx_outp;
u8      gdbstub_busy;
u8      gdbstub_rx_overflow;
u8      gdbstub_rx_unget;

static u8       gdbstub_flush_caches;
static char     input_buffer[BUFMAX];
static char     output_buffer[BUFMAX];
static char     trans_buffer[BUFMAX];

struct gdbstub_bkpt {
        u8      *addr;          /* address of breakpoint */
        u8      len;            /* size of breakpoint */
        u8      origbytes[7];   /* original bytes */
};

static struct gdbstub_bkpt gdbstub_bkpts[256];

/*
 * local prototypes
 */
static void getpacket(char *buffer);
static int putpacket(char *buffer);
static int computeSignal(enum exception_code excep);
static int hex(unsigned char ch);
static int hexToInt(char **ptr, int *intValue);
static unsigned char *mem2hex(const void *mem, char *buf, int count,
                              int may_fault);
static const char *hex2mem(const char *buf, void *_mem, int count,
                           int may_fault);

/*
 * Convert ch from a hex digit to an int
 */
static int hex(unsigned 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;
}

#ifdef CONFIG_GDBSTUB_DEBUGGING

void debug_to_serial(const char *p, int n)
{
        __debug_to_serial(p, n);
        /* gdbstub_console_write(NULL, p, n); */
}

void gdbstub_printk(const char *fmt, ...)
{
        va_list args;
        int len;

        /* Emit the output into the temporary buffer */
        va_start(args, fmt);
        len = vsnprintf(trans_buffer, sizeof(trans_buffer), fmt, args);
        va_end(args);
        debug_to_serial(trans_buffer, len);
}

#endif

static inline char *gdbstub_strcpy(char *dst, const char *src)
{
        int loop = 0;
        while ((dst[loop] = src[loop]))
               loop++;
        return dst;
}

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

        for (;;) {
                /*
                 * wait around for the start character,
                 * ignore all other characters
                 */
                do {
                        gdbstub_io_rx_char(&ch, 0);
                } while (ch != '$');

                checksum = 0;
                xmitcsum = -1;
                count = 0;
                error = 0;

                /*
                 * now, read until a # or end of buffer is found
                 */
                while (count < BUFMAX) {
                        ret = gdbstub_io_rx_char(&ch, 0);
                        if (ret < 0)
                                error = ret;

                        if (ch == '#')
                                break;
                        checksum += ch;
                        buffer[count] = ch;
                        count++;
                }

                if (error == -EIO) {
                        gdbstub_proto("### GDB Rx Error - Skipping packet"
                                      " ###\n");
                        gdbstub_proto("### GDB Tx NAK\n");
                        gdbstub_io_tx_char('-');
                        continue;
                }

                if (count >= BUFMAX || error)
                        continue;

                buffer[count] = 0;

                /* read the checksum */
                ret = gdbstub_io_rx_char(&ch, 0);
                if (ret < 0)
                        error = ret;
                xmitcsum = hex(ch) << 4;

                ret = gdbstub_io_rx_char(&ch, 0);
                if (ret < 0)
                        error = ret;
                xmitcsum |= hex(ch);

                if (error) {
                        if (error == -EIO)
                                gdbstub_io("### GDB Rx Error -"
                                           " Skipping packet\n");
                        gdbstub_io("### GDB Tx NAK\n");
                        gdbstub_io_tx_char('-');
                        continue;
                }

                /* check the checksum */
                if (checksum != xmitcsum) {
                        gdbstub_io("### GDB Tx NAK\n");
                        gdbstub_io_tx_char('-');        /* failed checksum */
                        continue;
                }

                gdbstub_proto("### GDB Rx '$%s#%02x' ###\n", buffer, checksum);
                gdbstub_io("### GDB Tx ACK\n");
                gdbstub_io_tx_char('+'); /* successful transfer */

                /*
                 * if a sequence char is present,
                 * reply the sequence ID
                 */
                if (buffer[2] == ':') {
                        gdbstub_io_tx_char(buffer[0]);
                        gdbstub_io_tx_char(buffer[1]);

                        /*
                         * remove sequence chars from buffer
                         */
                        count = 0;
                        while (buffer[count])
                                count++;
                        for (i = 3; i <= count; i++)
                                buffer[i - 3] = buffer[i];
                }

                break;
        }
}

/*
 * send the packet in buffer.
 * - return 0 if successfully ACK'd
 * - return 1 if abandoned due to new incoming packet
 */
static int putpacket(char *buffer)
{
        unsigned char checksum;
        unsigned char ch;
        int count;

        /*
         * $<packet info>#<checksum>.
         */
        gdbstub_proto("### GDB Tx $'%s'#?? ###\n", buffer);

        do {
                gdbstub_io_tx_char('$');
                checksum = 0;
                count = 0;

                while ((ch = buffer[count]) != 0) {
                        gdbstub_io_tx_char(ch);
                        checksum += ch;
                        count += 1;
                }

                gdbstub_io_tx_char('#');
                gdbstub_io_tx_char(hex_asc_hi(checksum));
                gdbstub_io_tx_char(hex_asc_lo(checksum));

        } while (gdbstub_io_rx_char(&ch, 0),
                 ch == '-' && (gdbstub_io("### GDB Rx NAK\n"), 0),
                 ch != '-' && ch != '+' &&
                 (gdbstub_io("### GDB Rx ??? %02x\n", ch), 0),
                 ch != '+' && ch != '$');

        if (ch == '+') {
                gdbstub_io("### GDB Rx ACK\n");
                return 0;
        }

        gdbstub_io("### GDB Tx Abandoned\n");
        gdbstub_rx_unget = ch;
        return 1;
}

/*
 * While we find nice hex chars, build an int.
 * Return number of chars processed.
 */
static int hexToInt(char **ptr, int *intValue)
{
        int numChars = 0;
        int hexValue;

        *intValue = 0;

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

                *intValue = (*intValue << 4) | hexValue;
                numChars++;

                (*ptr)++;
        }

        return (numChars);
}

#ifdef CONFIG_GDBSTUB_ALLOW_SINGLE_STEP
/*
 * We single-step by setting breakpoints. When an exception
 * is handled, we need to restore the instructions hoisted
 * when the breakpoints were set.
 *
 * This is where we save the original instructions.
 */
static struct gdb_bp_save {
        u8      *addr;
        u8      opcode[2];
} step_bp[2];

static const unsigned char gdbstub_insn_sizes[256] =
{
        /* 1  2  3  4  5  6  7  8  9  a  b  c  d  e  f */
        1, 3, 3, 3, 1, 3, 3, 3, 1, 3, 3, 3, 1, 3, 3, 3, /* 0 */
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 1 */
        2, 2, 2, 2, 3, 3, 3, 3, 2, 2, 2, 2, 3, 3, 3, 3, /* 2 */
        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 1, 1, 1, 1, /* 3 */
        1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, /* 4 */
        1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, /* 5 */
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 6 */
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 7 */
        2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* 8 */
        2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* 9 */
        2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* a */
        2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* b */
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 2, 2, /* c */
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* d */
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* e */
        0, 2, 2, 2, 2, 2, 2, 4, 0, 3, 0, 4, 0, 6, 7, 1  /* f */
};

static int __gdbstub_mark_bp(u8 *addr, int ix)
{
        /* vmalloc area */
        if (((u8 *) VMALLOC_START <= addr) && (addr < (u8 *) VMALLOC_END))
                goto okay;
        /* SRAM, SDRAM */
        if (((u8 *) 0x80000000UL <= addr) && (addr < (u8 *) 0xa0000000UL))
                goto okay;
        return 0;

okay:
        if (gdbstub_read_byte(addr + 0, &step_bp[ix].opcode[0]) < 0 ||
            gdbstub_read_byte(addr + 1, &step_bp[ix].opcode[1]) < 0)
                return 0;

        step_bp[ix].addr = addr;
        return 1;
}

static inline void __gdbstub_restore_bp(void)
{
#ifdef GDBSTUB_USE_F7F7_AS_BREAKPOINT
        if (step_bp[0].addr) {
                gdbstub_write_byte(step_bp[0].opcode[0], step_bp[0].addr + 0);
                gdbstub_write_byte(step_bp[0].opcode[1], step_bp[0].addr + 1);
        }
        if (step_bp[1].addr) {
                gdbstub_write_byte(step_bp[1].opcode[0], step_bp[1].addr + 0);
                gdbstub_write_byte(step_bp[1].opcode[1], step_bp[1].addr + 1);
        }
#else
        if (step_bp[0].addr)
                gdbstub_write_byte(step_bp[0].opcode[0], step_bp[0].addr + 0);
        if (step_bp[1].addr)
                gdbstub_write_byte(step_bp[1].opcode[0], step_bp[1].addr + 0);
#endif

        gdbstub_flush_caches = 1;

        step_bp[0].addr         = NULL;
        step_bp[0].opcode[0]    = 0;
        step_bp[0].opcode[1]    = 0;
        step_bp[1].addr         = NULL;
        step_bp[1].opcode[0]    = 0;
        step_bp[1].opcode[1]    = 0;
}

/*
 * emulate single stepping by means of breakpoint instructions
 */
static int gdbstub_single_step(struct pt_regs *regs)
{
        unsigned size;
        uint32_t x;
        uint8_t cur, *pc, *sp;

        step_bp[0].addr         = NULL;
        step_bp[0].opcode[0]    = 0;
        step_bp[0].opcode[1]    = 0;
        step_bp[1].addr         = NULL;
        step_bp[1].opcode[0]    = 0;
        step_bp[1].opcode[1]    = 0;
        x = 0;

        pc = (u8 *) regs->pc;
        sp = (u8 *) (regs + 1);
        if (gdbstub_read_byte(pc, &cur) < 0)
                return -EFAULT;

        gdbstub_bkpt("Single Step from %p { %02x }\n", pc, cur);

        gdbstub_flush_caches = 1;

        size = gdbstub_insn_sizes[cur];
        if (size > 0) {
                if (!__gdbstub_mark_bp(pc + size, 0))
                        goto fault;
        } else {
                switch (cur) {
                        /* Bxx (d8,PC) */
                case 0xc0 ... 0xca:
                        if (gdbstub_read_byte(pc + 1, (u8 *) &x) < 0)
                                goto fault;
                        if (!__gdbstub_mark_bp(pc + 2, 0))
                                goto fault;
                        if ((x < 0 || x > 2) &&
                            !__gdbstub_mark_bp(pc + (s8) x, 1))
                                goto fault;
                        break;

                        /* LXX (d8,PC) */
                case 0xd0 ... 0xda:
                        if (!__gdbstub_mark_bp(pc + 1, 0))
                                goto fault;
                        if (regs->pc != regs->lar &&
                            !__gdbstub_mark_bp((u8 *) regs->lar, 1))
                                goto fault;
                        break;

                        /* SETLB - loads the next for bytes into the LIR
                         * register */
                case 0xdb:
                        if (!__gdbstub_mark_bp(pc + 1, 0))
                                goto fault;
                        break;

                        /* JMP (d16,PC) or CALL (d16,PC) */
                case 0xcc:
                case 0xcd:
                        if (gdbstub_read_byte(pc + 1, ((u8 *) &x) + 0) < 0 ||
                            gdbstub_read_byte(pc + 2, ((u8 *) &x) + 1) < 0)
                                goto fault;
                        if (!__gdbstub_mark_bp(pc + (s16) x, 0))
                                goto fault;
                        break;

                        /* JMP (d32,PC) or CALL (d32,PC) */
                case 0xdc:
                case 0xdd:
                        if (gdbstub_read_byte(pc + 1, ((u8 *) &x) + 0) < 0 ||
                            gdbstub_read_byte(pc + 2, ((u8 *) &x) + 1) < 0 ||
                            gdbstub_read_byte(pc + 3, ((u8 *) &x) + 2) < 0 ||
                            gdbstub_read_byte(pc + 4, ((u8 *) &x) + 3) < 0)
                                goto fault;
                        if (!__gdbstub_mark_bp(pc + (s32) x, 0))
                                goto fault;
                        break;

                        /* RETF */
                case 0xde:
                        if (!__gdbstub_mark_bp((u8 *) regs->mdr, 0))
                                goto fault;
                        break;

                        /* RET */
                case 0xdf:
                        if (gdbstub_read_byte(pc + 2, (u8 *) &x) < 0)
                                goto fault;
                        sp += (s8)x;
                        if (gdbstub_read_byte(sp + 0, ((u8 *) &x) + 0) < 0 ||
                            gdbstub_read_byte(sp + 1, ((u8 *) &x) + 1) < 0 ||
                            gdbstub_read_byte(sp + 2, ((u8 *) &x) + 2) < 0 ||
                            gdbstub_read_byte(sp + 3, ((u8 *) &x) + 3) < 0)
                                goto fault;
                        if (!__gdbstub_mark_bp((u8 *) x, 0))
                                goto fault;
                        break;

                case 0xf0:
                        if (gdbstub_read_byte(pc + 1, &cur) < 0)
                                goto fault;

                        if (cur >= 0xf0 && cur <= 0xf7) {
                                /* JMP (An) / CALLS (An) */
                                switch (cur & 3) {
                                case 0: x = regs->a0; break;
                                case 1: x = regs->a1; break;
                                case 2: x = regs->a2; break;
                                case 3: x = regs->a3; break;
                                }
                                if (!__gdbstub_mark_bp((u8 *) x, 0))
                                        goto fault;
                        } else if (cur == 0xfc) {
                                /* RETS */
                                if (gdbstub_read_byte(
                                            sp + 0, ((u8 *) &x) + 0) < 0 ||
                                    gdbstub_read_byte(
                                            sp + 1, ((u8 *) &x) + 1) < 0 ||
                                    gdbstub_read_byte(
                                            sp + 2, ((u8 *) &x) + 2) < 0 ||
                                    gdbstub_read_byte(
                                            sp + 3, ((u8 *) &x) + 3) < 0)
                                        goto fault;
                                if (!__gdbstub_mark_bp((u8 *) x, 0))
                                        goto fault;
                        } else if (cur == 0xfd) {
                                /* RTI */
                                if (gdbstub_read_byte(
                                            sp + 4, ((u8 *) &x) + 0) < 0 ||
                                    gdbstub_read_byte(
                                            sp + 5, ((u8 *) &x) + 1) < 0 ||
                                    gdbstub_read_byte(
                                            sp + 6, ((u8 *) &x) + 2) < 0 ||
                                    gdbstub_read_byte(
                                            sp + 7, ((u8 *) &x) + 3) < 0)
                                        goto fault;
                                if (!__gdbstub_mark_bp((u8 *) x, 0))
                                        goto fault;
                        } else {
                                if (!__gdbstub_mark_bp(pc + 2, 0))
                                        goto fault;
                        }

                        break;

                        /* potential 3-byte conditional branches */
                case 0xf8:
                        if (gdbstub_read_byte(pc + 1, &cur) < 0)
                                goto fault;
                        if (!__gdbstub_mark_bp(pc + 3, 0))
                                goto fault;

                        if (cur >= 0xe8 && cur <= 0xeb) {
                                if (gdbstub_read_byte(
                                            pc + 2, ((u8 *) &x) + 0) < 0)
                                        goto fault;
                                if ((x < 0 || x > 3) &&
                                    !__gdbstub_mark_bp(pc + (s8) x, 1))
                                        goto fault;
                        }
                        break;

                case 0xfa:
                        if (gdbstub_read_byte(pc + 1, &cur) < 0)
                                goto fault;

                        if (cur == 0xff) {
                                /* CALLS (d16,PC) */
                                if (gdbstub_read_byte(
                                            pc + 2, ((u8 *) &x) + 0) < 0 ||
                                    gdbstub_read_byte(
                                            pc + 3, ((u8 *) &x) + 1) < 0)
                                        goto fault;
                                if (!__gdbstub_mark_bp(pc + (s16) x, 0))
                                        goto fault;
                        } else {
                                if (!__gdbstub_mark_bp(pc + 4, 0))
                                        goto fault;
                        }
                        break;

                case 0xfc:
                        if (gdbstub_read_byte(pc + 1, &cur) < 0)
                                goto fault;
                        if (cur == 0xff) {
                                /* CALLS (d32,PC) */
                                if (gdbstub_read_byte(
                                            pc + 2, ((u8 *) &x) + 0) < 0 ||
                                    gdbstub_read_byte(
                                            pc + 3, ((u8 *) &x) + 1) < 0 ||
                                    gdbstub_read_byte(
                                            pc + 4, ((u8 *) &x) + 2) < 0 ||
                                    gdbstub_read_byte(
                                            pc + 5, ((u8 *) &x) + 3) < 0)
                                        goto fault;
                                if (!__gdbstub_mark_bp(
                                            pc + (s32) x, 0))
                                        goto fault;
                        } else {
                                if (!__gdbstub_mark_bp(
                                            pc + 6, 0))
                                        goto fault;
                        }
                        break;

                }
        }

        gdbstub_bkpt("Step: %02x at %p; %02x at %p\n",
                     step_bp[0].opcode[0], step_bp[0].addr,
                     step_bp[1].opcode[0], step_bp[1].addr);

        if (step_bp[0].addr) {
#ifdef GDBSTUB_USE_F7F7_AS_BREAKPOINT
                if (gdbstub_write_byte(0xF7, step_bp[0].addr + 0) < 0 ||
                    gdbstub_write_byte(0xF7, step_bp[0].addr + 1) < 0)
                        goto fault;
#else
                if (gdbstub_write_byte(0xFF, step_bp[0].addr + 0) < 0)
                        goto fault;
#endif
        }

        if (step_bp[1].addr) {
#ifdef GDBSTUB_USE_F7F7_AS_BREAKPOINT
                if (gdbstub_write_byte(0xF7, step_bp[1].addr + 0) < 0 ||
                    gdbstub_write_byte(0xF7, step_bp[1].addr + 1) < 0)
                        goto fault;
#else
                if (gdbstub_write_byte(0xFF, step_bp[1].addr + 0) < 0)
                        goto fault;
#endif
        }

        return 0;

 fault:
        /* uh-oh - silly address alert, try and restore things */
        __gdbstub_restore_bp();
        return -EFAULT;
}
#endif /* CONFIG_GDBSTUB_ALLOW_SINGLE_STEP */

#ifdef CONFIG_GDBSTUB_CONSOLE

void gdbstub_console_write(struct console *con, const char *p, unsigned n)
{
        static const char gdbstub_cr[] = { 0x0d };
        char outbuf[26];
        int qty;
        u8 busy;

        busy = gdbstub_busy;
        gdbstub_busy = 1;

        outbuf[0] = 'O';

        while (n > 0) {
                qty = 1;

                while (n > 0 && qty < 20) {
                        mem2hex(p, outbuf + qty, 2, 0);
                        qty += 2;
                        if (*p == 0x0a) {
                                mem2hex(gdbstub_cr, outbuf + qty, 2, 0);
                                qty += 2;
                        }
                        p++;
                        n--;
                }

                outbuf[qty] = 0;
                putpacket(outbuf);
        }

        gdbstub_busy = busy;
}

static kdev_t gdbstub_console_dev(struct console *con)
{
        return MKDEV(1, 3); /* /dev/null */
}

static struct console gdbstub_console = {
        .name   = "gdb",
        .write  = gdbstub_console_write,
        .device = gdbstub_console_dev,
        .flags  = CON_PRINTBUFFER,
        .index  = -1,
};

#endif

/*
 * Convert the memory pointed to by mem into hex, placing result in buf.
 * - if successful, return a pointer to the last char put in buf (NUL)
 * - in case of mem fault, return NULL
 * may_fault is non-zero if we are reading from arbitrary memory, but is
 * currently not used.
 */
static
unsigned char *mem2hex(const void *_mem, char *buf, int count, int may_fault)
{
        const u8 *mem = _mem;
        u8 ch[4];

        if ((u32) mem & 1 && count >= 1) {
                if (gdbstub_read_byte(mem, ch) != 0)
                        return 0;
                buf = pack_hex_byte(buf, ch[0]);
                mem++;
                count--;
        }

        if ((u32) mem & 3 && count >= 2) {
                if (gdbstub_read_word(mem, ch) != 0)
                        return 0;
                buf = pack_hex_byte(buf, ch[0]);
                buf = pack_hex_byte(buf, ch[1]);
                mem += 2;
                count -= 2;
        }

        while (count >= 4) {
                if (gdbstub_read_dword(mem, ch) != 0)
                        return 0;
                buf = pack_hex_byte(buf, ch[0]);
                buf = pack_hex_byte(buf, ch[1]);
                buf = pack_hex_byte(buf, ch[2]);
                buf = pack_hex_byte(buf, ch[3]);
                mem += 4;
                count -= 4;
        }

        if (count >= 2) {
                if (gdbstub_read_word(mem, ch) != 0)
                        return 0;
                buf = pack_hex_byte(buf, ch[0]);
                buf = pack_hex_byte(buf, ch[1]);
                mem += 2;
                count -= 2;
        }

        if (count >= 1) {
                if (gdbstub_read_byte(mem, ch) != 0)
                        return 0;
                buf = pack_hex_byte(buf, ch[0]);
        }

        *buf = 0;
        return buf;
}

/*
 * 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_fault is non-zero if we are reading from arbitrary memory, but is
 * currently not used.
 */
static
const char *hex2mem(const char *buf, void *_mem, int count, int may_fault)
{
        u8 *mem = _mem;
        union {
                u32 val;
                u8 b[4];
        } ch;

        if ((u32) mem & 1 && count >= 1) {
                ch.b[0]  = hex(*buf++) << 4;
                ch.b[0] |= hex(*buf++);
                if (gdbstub_write_byte(ch.val, mem) != 0)
                        return 0;
                mem++;
                count--;
        }

        if ((u32) mem & 3 && count >= 2) {
                ch.b[0]  = hex(*buf++) << 4;
                ch.b[0] |= hex(*buf++);
                ch.b[1]  = hex(*buf++) << 4;
                ch.b[1] |= hex(*buf++);
                if (gdbstub_write_word(ch.val, mem) != 0)
                        return 0;
                mem += 2;
                count -= 2;
        }

        while (count >= 4) {
                ch.b[0]  = hex(*buf++) << 4;
                ch.b[0] |= hex(*buf++);
                ch.b[1]  = hex(*buf++) << 4;
                ch.b[1] |= hex(*buf++);
                ch.b[2]  = hex(*buf++) << 4;
                ch.b[2] |= hex(*buf++);
                ch.b[3]  = hex(*buf++) << 4;
                ch.b[3] |= hex(*buf++);
                if (gdbstub_write_dword(ch.val, mem) != 0)
                        return 0;
                mem += 4;
                count -= 4;
        }

        if (count >= 2) {
                ch.b[0]  = hex(*buf++) << 4;
                ch.b[0] |= hex(*buf++);
                ch.b[1]  = hex(*buf++) << 4;
                ch.b[1] |= hex(*buf++);
                if (gdbstub_write_word(ch.val, mem) != 0)
                        return 0;
                mem += 2;
                count -= 2;
        }

        if (count >= 1) {
                ch.b[0]  = hex(*buf++) << 4;
                ch.b[0] |= hex(*buf++);
                if (gdbstub_write_byte(ch.val, mem) != 0)
                        return 0;
        }

        return buf;
}

/*
 * This table contains the mapping between MN10300 exception codes, and
 * signals, which are primarily what GDB understands.  It also indicates
 * which hardware traps we need to commandeer when initializing the stub.
 */
static const struct excep_to_sig_map {
        enum exception_code     excep;  /* MN10300 exception code */
        unsigned char           signo;  /* Signal that we map this into */
} excep_to_sig_map[] = {
        { EXCEP_ITLBMISS,       SIGSEGV         },
        { EXCEP_DTLBMISS,       SIGSEGV         },
        { EXCEP_TRAP,           SIGTRAP         },
        { EXCEP_ISTEP,          SIGTRAP         },
        { EXCEP_IBREAK,         SIGTRAP         },
        { EXCEP_OBREAK,         SIGTRAP         },
        { EXCEP_UNIMPINS,       SIGILL          },
        { EXCEP_UNIMPEXINS,     SIGILL          },
        { EXCEP_MEMERR,         SIGSEGV         },
        { EXCEP_MISALIGN,       SIGSEGV         },
        { EXCEP_BUSERROR,       SIGBUS          },
        { EXCEP_ILLINSACC,      SIGSEGV         },
        { EXCEP_ILLDATACC,      SIGSEGV         },
        { EXCEP_IOINSACC,       SIGSEGV         },
        { EXCEP_PRIVINSACC,     SIGSEGV         },
        { EXCEP_PRIVDATACC,     SIGSEGV         },
        { EXCEP_FPU_DISABLED,   SIGFPE          },
        { EXCEP_FPU_UNIMPINS,   SIGFPE          },
        { EXCEP_FPU_OPERATION,  SIGFPE          },
        { EXCEP_WDT,            SIGALRM         },
        { EXCEP_NMI,            SIGQUIT         },
        { EXCEP_IRQ_LEVEL0,     SIGINT          },
        { EXCEP_IRQ_LEVEL1,     SIGINT          },
        { EXCEP_IRQ_LEVEL2,     SIGINT          },
        { EXCEP_IRQ_LEVEL3,     SIGINT          },
        { EXCEP_IRQ_LEVEL4,     SIGINT          },
        { EXCEP_IRQ_LEVEL5,     SIGINT          },
        { EXCEP_IRQ_LEVEL6,     SIGINT          },
        { 0, 0}
};

/*
 * convert the MN10300 exception code into a UNIX signal number
 */
static int computeSignal(enum exception_code excep)
{
        const struct excep_to_sig_map *map;

        for (map = excep_to_sig_map; map->signo; map++)
                if (map->excep == excep)
                        return map->signo;

        return SIGHUP; /* default for things we don't know about */
}

static u32 gdbstub_fpcr, gdbstub_fpufs_array[32];

/*
 *
 */
static void gdbstub_store_fpu(void)
{
#ifdef CONFIG_FPU

        asm volatile(
                "or %2,epsw\n"
#ifdef CONFIG_MN10300_PROC_MN103E010
                "nop\n"
                "nop\n"
#endif
                "mov %1, a1\n"
                "fmov fs0,  (a1+)\n"
                "fmov fs1,  (a1+)\n"
                "fmov fs2,  (a1+)\n"
                "fmov fs3,  (a1+)\n"
                "fmov fs4,  (a1+)\n"
                "fmov fs5,  (a1+)\n"
                "fmov fs6,  (a1+)\n"
                "fmov fs7,  (a1+)\n"
                "fmov fs8,  (a1+)\n"
                "fmov fs9,  (a1+)\n"
                "fmov fs10, (a1+)\n"
                "fmov fs11, (a1+)\n"
                "fmov fs12, (a1+)\n"
                "fmov fs13, (a1+)\n"
                "fmov fs14, (a1+)\n"

                "fmov fs15, (a1+)\n"
                "fmov fs16, (a1+)\n"
                "fmov fs17, (a1+)\n"
                "fmov fs18, (a1+)\n"
                "fmov fs19, (a1+)\n"
                "fmov fs20, (a1+)\n"
                "fmov fs21, (a1+)\n"
                "fmov fs22, (a1+)\n"
                "fmov fs23, (a1+)\n"
                "fmov fs24, (a1+)\n"
                "fmov fs25, (a1+)\n"
                "fmov fs26, (a1+)\n"
                "fmov fs27, (a1+)\n"
                "fmov fs28, (a1+)\n"
                "fmov fs29, (a1+)\n"
                "fmov fs30, (a1+)\n"
                "fmov fs31, (a1+)\n"
                "fmov fpcr, %0\n"
                : "=d"(gdbstub_fpcr)
                : "g" (&gdbstub_fpufs_array), "i"(EPSW_FE)
                : "a1"
                );
#endif
}

/*
 *
 */
static void gdbstub_load_fpu(void)
{
#ifdef CONFIG_FPU

        asm volatile(
                "or %1,epsw\n"
#ifdef CONFIG_MN10300_PROC_MN103E010
                "nop\n"
                "nop\n"
#endif
                "mov %0, a1\n"
                "fmov (a1+), fs0\n"
                "fmov (a1+), fs1\n"
                "fmov (a1+), fs2\n"
                "fmov (a1+), fs3\n"
                "fmov (a1+), fs4\n"
                "fmov (a1+), fs5\n"
                "fmov (a1+), fs6\n"
                "fmov (a1+), fs7\n"
                "fmov (a1+), fs8\n"
                "fmov (a1+), fs9\n"
                "fmov (a1+), fs10\n"
                "fmov (a1+), fs11\n"
                "fmov (a1+), fs12\n"
                "fmov (a1+), fs13\n"
                "fmov (a1+), fs14\n"
                "fmov (a1+), fs15\n"
                "fmov (a1+), fs16\n"
                "fmov (a1+), fs17\n"
                "fmov (a1+), fs18\n"
                "fmov (a1+), fs19\n"
                "fmov (a1+), fs20\n"
                "fmov (a1+), fs21\n"
                "fmov (a1+), fs22\n"
                "fmov (a1+), fs23\n"
                "fmov (a1+), fs24\n"
                "fmov (a1+), fs25\n"
                "fmov (a1+), fs26\n"
                "fmov (a1+), fs27\n"
                "fmov (a1+), fs28\n"
                "fmov (a1+), fs29\n"
                "fmov (a1+), fs30\n"
                "fmov (a1+), fs31\n"
                "fmov %2, fpcr\n"
                :
                : "g" (&gdbstub_fpufs_array), "i"(EPSW_FE), "d"(gdbstub_fpcr)
                : "a1"
        );
#endif
}

/*
 * set a software breakpoint
 */
int gdbstub_set_breakpoint(u8 *addr, int len)
{
        int bkpt, loop, xloop;

#ifdef GDBSTUB_USE_F7F7_AS_BREAKPOINT
        len = (len + 1) & ~1;
#endif

        gdbstub_bkpt("setbkpt(%p,%d)\n", addr, len);

        for (bkpt = 255; bkpt >= 0; bkpt--)
                if (!gdbstub_bkpts[bkpt].addr)
                        break;
        if (bkpt < 0)
                return -ENOSPC;

        for (loop = 0; loop < len; loop++)
                if (gdbstub_read_byte(&addr[loop],
                                      &gdbstub_bkpts[bkpt].origbytes[loop]
                                      ) < 0)
                        return -EFAULT;

        gdbstub_flush_caches = 1;

#ifdef GDBSTUB_USE_F7F7_AS_BREAKPOINT
        for (loop = 0; loop < len; loop++)
                if (gdbstub_write_byte(0xF7, &addr[loop]) < 0)
                        goto restore;
#else
        for (loop = 0; loop < len; loop++)
                if (gdbstub_write_byte(0xFF, &addr[loop]) < 0)
                        goto restore;
#endif

        gdbstub_bkpts[bkpt].addr = addr;
        gdbstub_bkpts[bkpt].len = len;

        gdbstub_bkpt("Set BKPT[%02x]: %p-%p {%02x%02x%02x%02x%02x%02x%02x}\n",
                     bkpt,
                     gdbstub_bkpts[bkpt].addr,
                     gdbstub_bkpts[bkpt].addr + gdbstub_bkpts[bkpt].len - 1,
                     gdbstub_bkpts[bkpt].origbytes[0],
                     gdbstub_bkpts[bkpt].origbytes[1],
                     gdbstub_bkpts[bkpt].origbytes[2],
                     gdbstub_bkpts[bkpt].origbytes[3],
                     gdbstub_bkpts[bkpt].origbytes[4],
                     gdbstub_bkpts[bkpt].origbytes[5],
                     gdbstub_bkpts[bkpt].origbytes[6]
                     );

        return 0;

restore:
        for (xloop = 0; xloop < loop; xloop++)
                gdbstub_write_byte(gdbstub_bkpts[bkpt].origbytes[xloop],
                                   addr + xloop);
        return -EFAULT;
}

/*
 * clear a software breakpoint
 */
int gdbstub_clear_breakpoint(u8 *addr, int len)
{
        int bkpt, loop;

#ifdef GDBSTUB_USE_F7F7_AS_BREAKPOINT
        len = (len + 1) & ~1;
#endif

        gdbstub_bkpt("clearbkpt(%p,%d)\n", addr, len);

        for (bkpt = 255; bkpt >= 0; bkpt--)
                if (gdbstub_bkpts[bkpt].addr == addr &&
                    gdbstub_bkpts[bkpt].len == len)
                        break;
        if (bkpt < 0)
                return -ENOENT;

        gdbstub_bkpts[bkpt].addr = NULL;

        gdbstub_flush_caches = 1;

        for (loop = 0; loop < len; loop++)
                if (gdbstub_write_byte(gdbstub_bkpts[bkpt].origbytes[loop],
                                       addr + loop) < 0)
                        return -EFAULT;

        return 0;
}

/*
 * This function does all command processing for interfacing to gdb
 * - returns 0 if the exception should be skipped, -ERROR otherwise.
 */
static int gdbstub(struct pt_regs *regs, enum exception_code excep)
{
        unsigned long *stack;
        unsigned long epsw, mdr;
        uint32_t zero, ssp;
        uint8_t broke;
        char *ptr;
        int sigval;
        int addr;
        int length;
        int loop;

        if (excep == EXCEP_FPU_DISABLED)
                return -ENOTSUPP;

        gdbstub_flush_caches = 0;

        mn10300_set_gdbleds(1);

        asm volatile("mov mdr,%0" : "=d"(mdr));
        local_save_flags(epsw);
        arch_local_change_intr_mask_level(
                NUM2EPSW_IM(CONFIG_DEBUGGER_IRQ_LEVEL + 1));

        gdbstub_store_fpu();

#ifdef CONFIG_GDBSTUB_IMMEDIATE
        /* skip the initial pause loop */
        if (regs->pc == (unsigned long) __gdbstub_pause)
                regs->pc = (unsigned long) start_kernel;
#endif

        /* if we were single stepping, restore the opcodes hoisted for the
         * breakpoint[s] */
        broke = 0;
#ifdef CONFIG_GDBSTUB_ALLOW_SINGLE_STEP
        if ((step_bp[0].addr && step_bp[0].addr == (u8 *) regs->pc) ||
            (step_bp[1].addr && step_bp[1].addr == (u8 *) regs->pc))
                broke = 1;

        __gdbstub_restore_bp();
#endif

        if (gdbstub_rx_unget) {
                sigval = SIGINT;
                if (gdbstub_rx_unget != 3)
                        goto packet_waiting;
                gdbstub_rx_unget = 0;
        }

        stack = (unsigned long *) regs->sp;
        sigval = broke ? SIGTRAP : computeSignal(excep);

        /* send information about a BUG() */
        if (!user_mode(regs) && excep == EXCEP_SYSCALL15) {
                const struct bug_entry *bug;

                bug = find_bug(regs->pc);
                if (bug)
                        goto found_bug;
                length = snprintf(trans_buffer, sizeof(trans_buffer),
                                  "BUG() at address %lx\n", regs->pc);
                goto send_bug_pkt;

        found_bug:
                length = snprintf(trans_buffer, sizeof(trans_buffer),
                                  "BUG() at address %lx (%s:%d)\n",
                                  regs->pc, bug->file, bug->line);

        send_bug_pkt:
                ptr = output_buffer;
                *ptr++ = 'O';
                ptr = mem2hex(trans_buffer, ptr, length, 0);
                *ptr = 0;
                putpacket(output_buffer);

                regs->pc -= 2;
                sigval = SIGABRT;
        } else if (regs->pc == (unsigned long) __gdbstub_bug_trap) {
                regs->pc = regs->mdr;
                sigval = SIGABRT;
        }

        /*
         * send a message to the debugger's user saying what happened if it may
         * not be clear cut (we can't map exceptions onto signals properly)
         */
        if (sigval != SIGINT && sigval != SIGTRAP && sigval != SIGILL) {
                static const char title[] = "Excep ", tbcberr[] = "BCBERR ";
                static const char crlf[] = "\r\n";
                char hx;
                u32 bcberr = BCBERR;

                ptr = output_buffer;
                *ptr++ = 'O';
                ptr = mem2hex(title, ptr, sizeof(title) - 1, 0);

                hx = hex_asc_hi(excep >> 8);
                ptr = pack_hex_byte(ptr, hx);
                hx = hex_asc_lo(excep >> 8);
                ptr = pack_hex_byte(ptr, hx);
                hx = hex_asc_hi(excep);
                ptr = pack_hex_byte(ptr, hx);
                hx = hex_asc_lo(excep);
                ptr = pack_hex_byte(ptr, hx);

                ptr = mem2hex(crlf, ptr, sizeof(crlf) - 1, 0);
                *ptr = 0;
                putpacket(output_buffer);       /* send it off... */

                /* BCBERR */
                ptr = output_buffer;
                *ptr++ = 'O';
                ptr = mem2hex(tbcberr, ptr, sizeof(tbcberr) - 1, 0);

                hx = hex_asc_hi(bcberr >> 24);
                ptr = pack_hex_byte(ptr, hx);
                hx = hex_asc_lo(bcberr >> 24);
                ptr = pack_hex_byte(ptr, hx);
                hx = hex_asc_hi(bcberr >> 16);
                ptr = pack_hex_byte(ptr, hx);
                hx = hex_asc_lo(bcberr >> 16);
                ptr = pack_hex_byte(ptr, hx);
                hx = hex_asc_hi(bcberr >> 8);
                ptr = pack_hex_byte(ptr, hx);
                hx = hex_asc_lo(bcberr >> 8);
                ptr = pack_hex_byte(ptr, hx);
                hx = hex_asc_hi(bcberr);
                ptr = pack_hex_byte(ptr, hx);
                hx = hex_asc_lo(bcberr);
                ptr = pack_hex_byte(ptr, hx);

                ptr = mem2hex(crlf, ptr, sizeof(crlf) - 1, 0);
                *ptr = 0;
                putpacket(output_buffer);       /* send it off... */
        }

        /*
         * tell the debugger that an exception has occurred
         */
        ptr = output_buffer;

        /*
         * Send trap type (converted to signal)
         */
        *ptr++ = 'T';
        ptr = pack_hex_byte(ptr, sigval);

        /*
         * Send Error PC
         */
        ptr = pack_hex_byte(ptr, GDB_REGID_PC);
        *ptr++ = ':';
        ptr = mem2hex(&regs->pc, ptr, 4, 0);
        *ptr++ = ';';

        /*
         * Send frame pointer
         */
        ptr = pack_hex_byte(ptr, GDB_REGID_FP);
        *ptr++ = ':';
        ptr = mem2hex(&regs->a3, ptr, 4, 0);
        *ptr++ = ';';

        /*
         * Send stack pointer
         */
        ssp = (unsigned long) (regs + 1);
        ptr = pack_hex_byte(ptr, GDB_REGID_SP);
        *ptr++ = ':';
        ptr = mem2hex(&ssp, ptr, 4, 0);
        *ptr++ = ';';

        *ptr++ = 0;
        putpacket(output_buffer);       /* send it off... */

packet_waiting:
        /*
         * Wait for input from remote GDB
         */
        while (1) {
                output_buffer[0] = 0;
                getpacket(input_buffer);

                switch (input_buffer[0]) {
                        /* request repeat of last signal number */
                case '?':
                        output_buffer[0] = 'S';
                        output_buffer[1] = hex_asc_hi(sigval);
                        output_buffer[2] = hex_asc_lo(sigval);
                        output_buffer[3] = 0;
                        break;

                case 'd':
                        /* toggle debug flag */
                        break;

                        /*
                         * Return the value of the CPU registers
                         */
                case 'g':
                        zero = 0;
                        ssp = (u32) (regs + 1);
                        ptr = output_buffer;
                        ptr = mem2hex(&regs->d0, ptr, 4, 0);
                        ptr = mem2hex(&regs->d1, ptr, 4, 0);
                        ptr = mem2hex(&regs->d2, ptr, 4, 0);
                        ptr = mem2hex(&regs->d3, ptr, 4, 0);
                        ptr = mem2hex(&regs->a0, ptr, 4, 0);
                        ptr = mem2hex(&regs->a1, ptr, 4, 0);
                        ptr = mem2hex(&regs->a2, ptr, 4, 0);
                        ptr = mem2hex(&regs->a3, ptr, 4, 0);

                        ptr = mem2hex(&ssp, ptr, 4, 0);         /* 8 */
                        ptr = mem2hex(&regs->pc, ptr, 4, 0);
                        ptr = mem2hex(&regs->mdr, ptr, 4, 0);
                        ptr = mem2hex(&regs->epsw, ptr, 4, 0);
                        ptr = mem2hex(&regs->lir, ptr, 4, 0);
                        ptr = mem2hex(&regs->lar, ptr, 4, 0);
                        ptr = mem2hex(&regs->mdrq, ptr, 4, 0);

                        ptr = mem2hex(&regs->e0, ptr, 4, 0);    /* 15 */
                        ptr = mem2hex(&regs->e1, ptr, 4, 0);
                        ptr = mem2hex(&regs->e2, ptr, 4, 0);
                        ptr = mem2hex(&regs->e3, ptr, 4, 0);
                        ptr = mem2hex(&regs->e4, ptr, 4, 0);
                        ptr = mem2hex(&regs->e5, ptr, 4, 0);
                        ptr = mem2hex(&regs->e6, ptr, 4, 0);
                        ptr = mem2hex(&regs->e7, ptr, 4, 0);

                        ptr = mem2hex(&ssp, ptr, 4, 0);
                        ptr = mem2hex(&regs, ptr, 4, 0);
                        ptr = mem2hex(&regs->sp, ptr, 4, 0);
                        ptr = mem2hex(&regs->mcrh, ptr, 4, 0);  /* 26 */
                        ptr = mem2hex(&regs->mcrl, ptr, 4, 0);
                        ptr = mem2hex(&regs->mcvf, ptr, 4, 0);

                        ptr = mem2hex(&gdbstub_fpcr, ptr, 4, 0); /* 29 - FPCR */
                        ptr = mem2hex(&zero, ptr, 4, 0);
                        ptr = mem2hex(&zero, ptr, 4, 0);
                        for (loop = 0; loop < 32; loop++)
                                ptr = mem2hex(&gdbstub_fpufs_array[loop],
                                              ptr, 4, 0); /* 32 - FS0-31 */

                        break;

                        /*
                         * set the value of the CPU registers - return OK
                         */
                case 'G':
                {
                        const char *ptr;

                        ptr = &input_buffer[1];
                        ptr = hex2mem(ptr, &regs->d0, 4, 0);
                        ptr = hex2mem(ptr, &regs->d1, 4, 0);
                        ptr = hex2mem(ptr, &regs->d2, 4, 0);
                        ptr = hex2mem(ptr, &regs->d3, 4, 0);
                        ptr = hex2mem(ptr, &regs->a0, 4, 0);
                        ptr = hex2mem(ptr, &regs->a1, 4, 0);
                        ptr = hex2mem(ptr, &regs->a2, 4, 0);
                        ptr = hex2mem(ptr, &regs->a3, 4, 0);

                        ptr = hex2mem(ptr, &ssp, 4, 0);         /* 8 */
                        ptr = hex2mem(ptr, &regs->pc, 4, 0);
                        ptr = hex2mem(ptr, &regs->mdr, 4, 0);
                        ptr = hex2mem(ptr, &regs->epsw, 4, 0);
                        ptr = hex2mem(ptr, &regs->lir, 4, 0);
                        ptr = hex2mem(ptr, &regs->lar, 4, 0);
                        ptr = hex2mem(ptr, &regs->mdrq, 4, 0);

                        ptr = hex2mem(ptr, &regs->e0, 4, 0);    /* 15 */
                        ptr = hex2mem(ptr, &regs->e1, 4, 0);
                        ptr = hex2mem(ptr, &regs->e2, 4, 0);
                        ptr = hex2mem(ptr, &regs->e3, 4, 0);
                        ptr = hex2mem(ptr, &regs->e4, 4, 0);
                        ptr = hex2mem(ptr, &regs->e5, 4, 0);
                        ptr = hex2mem(ptr, &regs->e6, 4, 0);
                        ptr = hex2mem(ptr, &regs->e7, 4, 0);

                        ptr = hex2mem(ptr, &ssp, 4, 0);
                        ptr = hex2mem(ptr, &zero, 4, 0);
                        ptr = hex2mem(ptr, &regs->sp, 4, 0);
                        ptr = hex2mem(ptr, &regs->mcrh, 4, 0);  /* 26 */
                        ptr = hex2mem(ptr, &regs->mcrl, 4, 0);
                        ptr = hex2mem(ptr, &regs->mcvf, 4, 0);

                        ptr = hex2mem(ptr, &zero, 4, 0);        /* 29 - FPCR */
                        ptr = hex2mem(ptr, &zero, 4, 0);
                        ptr = hex2mem(ptr, &zero, 4, 0);
                        for (loop = 0; loop < 32; loop++)     /* 32 - FS0-31 */
                                ptr = hex2mem(ptr, &zero, 4, 0);

#if 0
                        /*
                         * See if the stack pointer has moved. If so, then copy
                         * the saved locals and ins to the new location.
                         */
                        unsigned long *newsp = (unsigned long *) registers[SP];
                        if (sp != newsp)
                                sp = memcpy(newsp, sp, 16 * 4);
#endif

                        gdbstub_strcpy(output_buffer, "OK");
                }
                break;

                /*
                 * mAA..AA,LLLL  Read LLLL bytes at address AA..AA
                 */
                case 'm':
                        ptr = &input_buffer[1];

                        if (hexToInt(&ptr, &addr) &&
                            *ptr++ == ',' &&
                            hexToInt(&ptr, &length)
                            ) {
                                if (mem2hex((char *) addr, output_buffer,
                                            length, 1))
                                        break;
                                gdbstub_strcpy(output_buffer, "E03");
                        } else {
                                gdbstub_strcpy(output_buffer, "E01");
                        }
                        break;

                        /*
                         * MAA..AA,LLLL: Write LLLL bytes at address AA.AA
                         * return OK
                         */
                case 'M':
                        ptr = &input_buffer[1];

                        if (hexToInt(&ptr, &addr) &&
                            *ptr++ == ',' &&
                            hexToInt(&ptr, &length) &&
                            *ptr++ == ':'
                            ) {
                                if (hex2mem(ptr, (char *) addr, length, 1))
                                        gdbstub_strcpy(output_buffer, "OK");
                                else
                                        gdbstub_strcpy(output_buffer, "E03");

                                gdbstub_flush_caches = 1;
                        } else {
                                gdbstub_strcpy(output_buffer, "E02");
                        }
                        break;

                        /*
                         * cAA..AA    Continue at address AA..AA(optional)
                         */
                case 'c':
                        /* try to read optional parameter, pc unchanged if no
                         * parm */

                        ptr = &input_buffer[1];
                        if (hexToInt(&ptr, &addr))
                                regs->pc = addr;
                        goto done;

                        /*
                         * kill the program
                         */
                case 'k' :
                        goto done;      /* just continue */

                        /*
                         * Reset the whole machine (FIXME: system dependent)
                         */
                case 'r':
                        break;

                        /*
                         * Step to next instruction
                         */
                case 's':
                        /* Using the T flag doesn't seem to perform single
                         * stepping (it seems to wind up being caught by the
                         * JTAG unit), so we have to use breakpoints and
                         * continue instead.
                         */
#ifdef CONFIG_GDBSTUB_ALLOW_SINGLE_STEP
                        if (gdbstub_single_step(regs) < 0)
                                /* ignore any fault error for now */
                                gdbstub_printk("unable to set single-step"
                                               " bp\n");
                        goto done;
#else
                        gdbstub_strcpy(output_buffer, "E01");
                        break;
#endif

                        /*
                         * Set baud rate (bBB)
                         */
                case 'b':
                        do {
                                int baudrate;

                                ptr = &input_buffer[1];
                                if (!hexToInt(&ptr, &baudrate)) {
                                        gdbstub_strcpy(output_buffer, "B01");
                                        break;
                                }

                                if (baudrate) {
                                        /* ACK before changing speed */
                                        putpacket("OK");
                                        gdbstub_io_set_baud(baudrate);
                                }
                        } while (0);
                        break;

                        /*
                         * Set breakpoint
                         */
                case 'Z':
                        ptr = &input_buffer[1];

                        if (!hexToInt(&ptr, &loop) || *ptr++ != ',' ||
                            !hexToInt(&ptr, &addr) || *ptr++ != ',' ||
                            !hexToInt(&ptr, &length)
                            ) {
                                gdbstub_strcpy(output_buffer, "E01");
                                break;
                        }

                        /* only support software breakpoints */
                        gdbstub_strcpy(output_buffer, "E03");
                        if (loop != 0 ||
                            length < 1 ||
                            length > 7 ||
                            (unsigned long) addr < 4096)
                                break;

                        if (gdbstub_set_breakpoint((u8 *) addr, length) < 0)
                                break;

                        gdbstub_strcpy(output_buffer, "OK");
                        break;

                        /*
                         * Clear breakpoint
                         */
                case 'z':
                        ptr = &input_buffer[1];

                        if (!hexToInt(&ptr, &loop) || *ptr++ != ',' ||
                            !hexToInt(&ptr, &addr) || *ptr++ != ',' ||
                            !hexToInt(&ptr, &length)
                            ) {
                                gdbstub_strcpy(output_buffer, "E01");
                                break;
                        }

                        /* only support software breakpoints */
                        gdbstub_strcpy(output_buffer, "E03");
                        if (loop != 0 ||
                            length < 1 ||
                            length > 7 ||
                            (unsigned long) addr < 4096)
                                break;

                        if (gdbstub_clear_breakpoint((u8 *) addr, length) < 0)
                                break;

                        gdbstub_strcpy(output_buffer, "OK");
                        break;

                default:
                        gdbstub_proto("### GDB Unsupported Cmd '%s'\n",
                                      input_buffer);
                        break;
                }

                /* reply to the request */
                putpacket(output_buffer);
        }

done:
        /*
         * Need to flush the instruction cache here, as we may
         * have deposited a breakpoint, and the icache probably
         * has no way of knowing that a data ref to some location
         * may have changed something that is in the instruction
         * cache.
         * NB: We flush both caches, just to be sure...
         */
        if (gdbstub_flush_caches)
                debugger_local_cache_flushinv();

        gdbstub_load_fpu();
        mn10300_set_gdbleds(0);
        if (excep == EXCEP_NMI)
                NMICR = NMICR_NMIF;

        touch_softlockup_watchdog();

        local_irq_restore(epsw);
        return 0;
}

/*
 * Determine if we hit a debugger special breakpoint that needs skipping over
 * automatically.
 */
int at_debugger_breakpoint(struct pt_regs *regs)
{
        return 0;
}

/*
 * handle event interception
 */
asmlinkage int debugger_intercept(enum exception_code excep,
                                  int signo, int si_code, struct pt_regs *regs)
{
        static u8 notfirst = 1;
        int ret;

        if (gdbstub_busy)
                gdbstub_printk("--> gdbstub reentered itself\n");
        gdbstub_busy = 1;

        if (notfirst) {
                unsigned long mdr;
                asm("mov mdr,%0" : "=d"(mdr));

                gdbstub_entry(
                        "--> debugger_intercept(%p,%04x) [MDR=%lx PC=%lx]\n",
                        regs, excep, mdr, regs->pc);

                gdbstub_entry(
                        "PC:  %08lx EPSW:  %08lx  SSP: %08lx mode: %s\n",
                        regs->pc, regs->epsw, (unsigned long) &ret,
                        user_mode(regs) ? "User" : "Super");
                gdbstub_entry(
                        "d0:  %08lx   d1:  %08lx   d2: %08lx   d3: %08lx\n",
                        regs->d0, regs->d1, regs->d2, regs->d3);
                gdbstub_entry(
                        "a0:  %08lx   a1:  %08lx   a2: %08lx   a3: %08lx\n",
                        regs->a0, regs->a1, regs->a2, regs->a3);
                gdbstub_entry(
                        "e0:  %08lx   e1:  %08lx   e2: %08lx   e3: %08lx\n",
                        regs->e0, regs->e1, regs->e2, regs->e3);
                gdbstub_entry(
                        "e4:  %08lx   e5:  %08lx   e6: %08lx   e7: %08lx\n",
                        regs->e4, regs->e5, regs->e6, regs->e7);
                gdbstub_entry(
                        "lar: %08lx   lir: %08lx  mdr: %08lx  usp: %08lx\n",
                        regs->lar, regs->lir, regs->mdr, regs->sp);
                gdbstub_entry(
                        "cvf: %08lx   crl: %08lx  crh: %08lx  drq: %08lx\n",
                        regs->mcvf, regs->mcrl, regs->mcrh, regs->mdrq);
                gdbstub_entry(
                        "threadinfo=%p task=%p)\n",
                        current_thread_info(), current);
        } else {
                notfirst = 1;
        }

        ret = gdbstub(regs, excep);

        gdbstub_entry("<-- debugger_intercept()\n");
        gdbstub_busy = 0;
        return ret;
}

/*
 * handle the GDB stub itself causing an exception
 */
asmlinkage void gdbstub_exception(struct pt_regs *regs,
                                  enum exception_code excep)
{
        unsigned long mdr;

        asm("mov mdr,%0" : "=d"(mdr));
        gdbstub_entry("--> gdbstub exception({%p},%04x) [MDR=%lx]\n",
                      regs, excep, mdr);

        while ((unsigned long) regs == 0xffffffff) {}

        /* handle guarded memory accesses where we know it might fault */
        if (regs->pc == (unsigned) gdbstub_read_byte_guard) {
                regs->pc = (unsigned) gdbstub_read_byte_cont;
                goto fault;
        }

        if (regs->pc == (unsigned) gdbstub_read_word_guard) {
                regs->pc = (unsigned) gdbstub_read_word_cont;
                goto fault;
        }

        if (regs->pc == (unsigned) gdbstub_read_dword_guard) {
                regs->pc = (unsigned) gdbstub_read_dword_cont;
                goto fault;
        }

        if (regs->pc == (unsigned) gdbstub_write_byte_guard) {
                regs->pc = (unsigned) gdbstub_write_byte_cont;
                goto fault;
        }

        if (regs->pc == (unsigned) gdbstub_write_word_guard) {
                regs->pc = (unsigned) gdbstub_write_word_cont;
                goto fault;
        }

        if (regs->pc == (unsigned) gdbstub_write_dword_guard) {
                regs->pc = (unsigned) gdbstub_write_dword_cont;
                goto fault;
        }

        gdbstub_printk("\n### GDB stub caused an exception ###\n");

        /* something went horribly wrong */
        console_verbose();
        show_registers(regs);

        panic("GDB Stub caused an unexpected exception - can't continue\n");

        /* we caught an attempt by the stub to access silly memory */
fault:
        gdbstub_entry("<-- gdbstub exception() = EFAULT\n");
        regs->d0 = -EFAULT;
        return;
}

/*
 * send an exit message to GDB
 */
void gdbstub_exit(int status)
{
        unsigned char checksum;
        unsigned char ch;
        int count;

        gdbstub_busy = 1;
        output_buffer[0] = 'W';
        output_buffer[1] = hex_asc_hi(status);
        output_buffer[2] = hex_asc_lo(status);
        output_buffer[3] = 0;

        gdbstub_io_tx_char('$');
        checksum = 0;
        count = 0;

        while ((ch = output_buffer[count]) != 0) {
                gdbstub_io_tx_char(ch);
                checksum += ch;
                count += 1;
        }

        gdbstub_io_tx_char('#');
        gdbstub_io_tx_char(hex_asc_hi(checksum));
        gdbstub_io_tx_char(hex_asc_lo(checksum));

        /* make sure the output is flushed, or else RedBoot might clobber it */
        gdbstub_io_tx_flush();

        gdbstub_busy = 0;
}

/*
 * initialise the GDB stub
 */
asmlinkage void __init gdbstub_init(void)
{
#ifdef CONFIG_GDBSTUB_IMMEDIATE
        unsigned char ch;
        int ret;
#endif

        gdbstub_busy = 1;

        printk(KERN_INFO "%s", gdbstub_banner);

        gdbstub_io_init();

        gdbstub_entry("--> gdbstub_init\n");

        /* try to talk to GDB (or anyone insane enough to want to type GDB
         * protocol by hand) */
        gdbstub_io("### GDB Tx ACK\n");
        gdbstub_io_tx_char('+'); /* 'hello world' */

#ifdef CONFIG_GDBSTUB_IMMEDIATE
        gdbstub_printk("GDB Stub waiting for packet\n");

        /* in case GDB is started before us, ACK any packets that are already
         * sitting there (presumably "$?#xx")
         */
        do { gdbstub_io_rx_char(&ch, 0); } while (ch != '$');
        do { gdbstub_io_rx_char(&ch, 0); } while (ch != '#');
        /* eat first csum byte */
        do { ret = gdbstub_io_rx_char(&ch, 0); } while (ret != 0);
        /* eat second csum byte */
        do { ret = gdbstub_io_rx_char(&ch, 0); } while (ret != 0);

        gdbstub_io("### GDB Tx NAK\n");
        gdbstub_io_tx_char('-'); /* NAK it */

#else
        printk("GDB Stub ready\n");
#endif

        gdbstub_busy = 0;
        gdbstub_entry("<-- gdbstub_init\n");
}

/*
 * register the console at a more appropriate time
 */
#ifdef CONFIG_GDBSTUB_CONSOLE
static int __init gdbstub_postinit(void)
{
        printk(KERN_NOTICE "registering console\n");
        register_console(&gdbstub_console);
        return 0;
}

__initcall(gdbstub_postinit);
#endif

/*
 * handle character reception on GDB serial port
 * - jump into the GDB stub if BREAK is detected on the serial line
 */
asmlinkage void gdbstub_rx_irq(struct pt_regs *regs, enum exception_code excep)
{
        char ch;
        int ret;

        gdbstub_entry("--> gdbstub_rx_irq\n");

        do {
                ret = gdbstub_io_rx_char(&ch, 1);
                if (ret != -EIO && ret != -EAGAIN) {
                        if (ret != -EINTR)
                                gdbstub_rx_unget = ch;
                        gdbstub(regs, excep);
                }
        } while (ret != -EAGAIN);

        gdbstub_entry("<-- gdbstub_rx_irq\n");
}