[MIPS] MT: Improved multithreading support.

[deliverable/linux.git] / arch / mips / kernel / gdb-stub.c

/*
 *  arch/mips/kernel/gdb-stub.c
 *
 *  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) 2003 MontaVista Software Inc.
 *  Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
 */

/*
 *  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=mips-linux-elf
 *    $ make
 *    $ install
 *    $ which mips-linux-elf-gdb
 *    /usr/local/bin/mips-linux-elf-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
 *
 *  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_KGDB which in turn enables your calls
 *  to:
 *     set_debug_traps();
 *     breakpoint();
 *
 *  Step 4:
 *  Start the gdb session on the host.
 *
 *  Example:
 *    $ mips-linux-elf-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/config.h>
#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/smp.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/reboot.h>

#include <asm/asm.h>
#include <asm/cacheflush.h>
#include <asm/mipsregs.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/gdb-stub.h>
#include <asm/inst.h>
#include <asm/smp.h>

/*
 * external low-level support routines
 */

extern int putDebugChar(char c);    /* write a single character      */
extern char getDebugChar(void);     /* read and return a single char */
extern void trap_low(void);

/*
 * breakpoint and test functions
 */
extern void breakpoint(void);
extern void breakinst(void);
extern void async_breakpoint(void);
extern void async_breakinst(void);
extern void adel(void);

/*
 * local prototypes
 */

static void getpacket(char *buffer);
static void putpacket(char *buffer);
static int computeSignal(int tt);
static int hex(unsigned char ch);
static int hexToInt(char **ptr, int *intValue);
static int hexToLong(char **ptr, long *longValue);
static unsigned char *mem2hex(char *mem, char *buf, int count, int may_fault);
void handle_exception(struct gdb_regs *regs);

int kgdb_enabled;

/*
 * spin locks for smp case
 */
static DEFINE_SPINLOCK(kgdb_lock);
static raw_spinlock_t kgdb_cpulock[NR_CPUS] = {
        [0 ... NR_CPUS-1] = __RAW_SPIN_LOCK_UNLOCKED,
};

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

static char input_buffer[BUFMAX];
static char output_buffer[BUFMAX];
static int initialized; /* !0 means we've been initialized */
static int kgdb_started;
static const char hexchars[]="0123456789abcdef";

/* Used to prevent crashes in memory access.  Note that they'll crash anyway if
   we haven't set up fault handlers yet... */
int kgdb_read_byte(unsigned char *address, unsigned char *dest);
int kgdb_write_byte(unsigned char val, unsigned char *dest);

/*
 * 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;
}

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

        do {
                /*
                 * wait around for the start character,
                 * ignore all other characters
                 */
                while ((ch = (getDebugChar() & 0x7f)) != '$') ;

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

                /*
                 * now, read until a # or end of buffer is found
                 */
                while (count < BUFMAX) {
                        ch = getDebugChar();
                        if (ch == '#')
                                break;
                        checksum = checksum + ch;
                        buffer[count] = ch;
                        count = count + 1;
                }

                if (count >= BUFMAX)
                        continue;

                buffer[count] = 0;

                if (ch == '#') {
                        xmitcsum = hex(getDebugChar() & 0x7f) << 4;
                        xmitcsum |= hex(getDebugChar() & 0x7f);

                        if (checksum != xmitcsum)
                                putDebugChar('-');      /* failed checksum */
                        else {
                                putDebugChar('+'); /* successful transfer */

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

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

/*
 * send the packet in buffer.
 */
static void putpacket(char *buffer)
{
        unsigned char checksum;
        int count;
        unsigned char ch;

        /*
         * $<packet info>#<checksum>.
         */

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

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

                putDebugChar('#');
                putDebugChar(hexchars[checksum >> 4]);
                putDebugChar(hexchars[checksum & 0xf]);

        }
        while ((getDebugChar() & 0x7f) != '+');
}


/*
 * Convert the memory pointed to by mem into hex, placing result in buf.
 * Return a pointer to the last char put in buf (null), in case of mem fault,
 * return 0.
 * may_fault is non-zero if we are reading from arbitrary memory, but is currently
 * not used.
 */
static unsigned char *mem2hex(char *mem, char *buf, int count, int may_fault)
{
        unsigned char ch;

        while (count-- > 0) {
                if (kgdb_read_byte(mem++, &ch) != 0)
                        return 0;
                *buf++ = hexchars[ch >> 4];
                *buf++ = hexchars[ch & 0xf];
        }

        *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 char *hex2mem(char *buf, char *mem, int count, int binary, int may_fault)
{
        int i;
        unsigned char ch;

        for (i=0; i<count; i++)
        {
                if (binary) {
                        ch = *buf++;
                        if (ch == 0x7d)
                                ch = 0x20 ^ *buf++;
                }
                else {
                        ch = hex(*buf++) << 4;
                        ch |= hex(*buf++);
                }
                if (kgdb_write_byte(ch, mem++) != 0)
                        return 0;
        }

        return mem;
}

/*
 * This table contains the mapping between SPARC hardware trap types, and
 * signals, which are primarily what GDB understands.  It also indicates
 * which hardware traps we need to commandeer when initializing the stub.
 */
static struct hard_trap_info {
        unsigned char tt;               /* Trap type code for MIPS R3xxx and R4xxx */
        unsigned char signo;            /* Signal that we map this trap into */
} hard_trap_info[] = {
        { 6, SIGBUS },                  /* instruction bus error */
        { 7, SIGBUS },                  /* data bus error */
        { 9, SIGTRAP },                 /* break */
        { 10, SIGILL },                 /* reserved instruction */
/*      { 11, SIGILL },         */      /* CPU unusable */
        { 12, SIGFPE },                 /* overflow */
        { 13, SIGTRAP },                /* trap */
        { 14, SIGSEGV },                /* virtual instruction cache coherency */
        { 15, SIGFPE },                 /* floating point exception */
        { 23, SIGSEGV },                /* watch */
        { 31, SIGSEGV },                /* virtual data cache coherency */
        { 0, 0}                         /* Must be last */
};

/* Save the normal trap handlers for user-mode traps. */
void *saved_vectors[32];

/*
 * Set up exception handlers for tracing and breakpoints
 */
void set_debug_traps(void)
{
        struct hard_trap_info *ht;
        unsigned long flags;
        unsigned char c;

        local_irq_save(flags);
        for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
                saved_vectors[ht->tt] = set_except_vector(ht->tt, trap_low);

        putDebugChar('+'); /* 'hello world' */
        /*
         * In case GDB is started before us, ack any packets
         * (presumably "$?#xx") sitting there.
         */
        while((c = getDebugChar()) != '$');
        while((c = getDebugChar()) != '#');
        c = getDebugChar(); /* eat first csum byte */
        c = getDebugChar(); /* eat second csum byte */
        putDebugChar('+'); /* ack it */

        initialized = 1;
        local_irq_restore(flags);
}

void restore_debug_traps(void)
{
        struct hard_trap_info *ht;
        unsigned long flags;

        local_irq_save(flags);
        for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
                set_except_vector(ht->tt, saved_vectors[ht->tt]);
        local_irq_restore(flags);
}

/*
 * Convert the MIPS hardware trap type code to a Unix signal number.
 */
static int computeSignal(int tt)
{
        struct hard_trap_info *ht;

        for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
                if (ht->tt == tt)
                        return ht->signo;

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

/*
 * 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);
}

static int hexToLong(char **ptr, long *longValue)
{
        int numChars = 0;
        int hexValue;

        *longValue = 0;

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

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

                (*ptr)++;
        }

        return numChars;
}


#if 0
/*
 * Print registers (on target console)
 * Used only to debug the stub...
 */
void show_gdbregs(struct gdb_regs * regs)
{
        /*
         * Saved main processor registers
         */
        printk("$0 : %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
               regs->reg0, regs->reg1, regs->reg2, regs->reg3,
               regs->reg4, regs->reg5, regs->reg6, regs->reg7);
        printk("$8 : %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
               regs->reg8, regs->reg9, regs->reg10, regs->reg11,
               regs->reg12, regs->reg13, regs->reg14, regs->reg15);
        printk("$16: %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
               regs->reg16, regs->reg17, regs->reg18, regs->reg19,
               regs->reg20, regs->reg21, regs->reg22, regs->reg23);
        printk("$24: %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
               regs->reg24, regs->reg25, regs->reg26, regs->reg27,
               regs->reg28, regs->reg29, regs->reg30, regs->reg31);

        /*
         * Saved cp0 registers
         */
        printk("epc  : %08lx\nStatus: %08lx\nCause : %08lx\n",
               regs->cp0_epc, regs->cp0_status, regs->cp0_cause);
}
#endif /* dead code */

/*
 * 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 {
        unsigned long addr;
        unsigned int val;
} step_bp[2];

#define BP 0x0000000d  /* break opcode */

/*
 * Set breakpoint instructions for single stepping.
 */
static void single_step(struct gdb_regs *regs)
{
        union mips_instruction insn;
        unsigned long targ;
        int is_branch, is_cond, i;

        targ = regs->cp0_epc;
        insn.word = *(unsigned int *)targ;
        is_branch = is_cond = 0;

        switch (insn.i_format.opcode) {
        /*
         * jr and jalr are in r_format format.
         */
        case spec_op:
                switch (insn.r_format.func) {
                case jalr_op:
                case jr_op:
                        targ = *(&regs->reg0 + insn.r_format.rs);
                        is_branch = 1;
                        break;
                }
                break;

        /*
         * This group contains:
         * bltz_op, bgez_op, bltzl_op, bgezl_op,
         * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
         */
        case bcond_op:
                is_branch = is_cond = 1;
                targ += 4 + (insn.i_format.simmediate << 2);
                break;

        /*
         * These are unconditional and in j_format.
         */
        case jal_op:
        case j_op:
                is_branch = 1;
                targ += 4;
                targ >>= 28;
                targ <<= 28;
                targ |= (insn.j_format.target << 2);
                break;

        /*
         * These are conditional.
         */
        case beq_op:
        case beql_op:
        case bne_op:
        case bnel_op:
        case blez_op:
        case blezl_op:
        case bgtz_op:
        case bgtzl_op:
        case cop0_op:
        case cop1_op:
        case cop2_op:
        case cop1x_op:
                is_branch = is_cond = 1;
                targ += 4 + (insn.i_format.simmediate << 2);
                break;
        }

        if (is_branch) {
                i = 0;
                if (is_cond && targ != (regs->cp0_epc + 8)) {
                        step_bp[i].addr = regs->cp0_epc + 8;
                        step_bp[i++].val = *(unsigned *)(regs->cp0_epc + 8);
                        *(unsigned *)(regs->cp0_epc + 8) = BP;
                }
                step_bp[i].addr = targ;
                step_bp[i].val  = *(unsigned *)targ;
                *(unsigned *)targ = BP;
        } else {
                step_bp[0].addr = regs->cp0_epc + 4;
                step_bp[0].val  = *(unsigned *)(regs->cp0_epc + 4);
                *(unsigned *)(regs->cp0_epc + 4) = BP;
        }
}

/*
 *  If asynchronously interrupted by gdb, then we need to set a breakpoint
 *  at the interrupted instruction so that we wind up stopped with a
 *  reasonable stack frame.
 */
static struct gdb_bp_save async_bp;

/*
 * Swap the interrupted EPC with our asynchronous breakpoint routine.
 * This is safer than stuffing the breakpoint in-place, since no cache
 * flushes (or resulting smp_call_functions) are required.  The
 * assumption is that only one CPU will be handling asynchronous bp's,
 * and only one can be active at a time.
 */
extern spinlock_t smp_call_lock;

void set_async_breakpoint(unsigned long *epc)
{
        /* skip breaking into userland */
        if ((*epc & 0x80000000) == 0)
                return;

#ifdef CONFIG_SMP
        /* avoid deadlock if someone is make IPC */
        if (spin_is_locked(&smp_call_lock))
                return;
#endif

        async_bp.addr = *epc;
        *epc = (unsigned long)async_breakpoint;
}

static void kgdb_wait(void *arg)
{
        unsigned flags;
        int cpu = smp_processor_id();

        local_irq_save(flags);

        __raw_spin_lock(&kgdb_cpulock[cpu]);
        __raw_spin_unlock(&kgdb_cpulock[cpu]);

        local_irq_restore(flags);
}

/*
 * GDB stub needs to call kgdb_wait on all processor with interrupts
 * disabled, so it uses it's own special variant.
 */
static int kgdb_smp_call_kgdb_wait(void)
{
#ifdef CONFIG_SMP
        struct call_data_struct data;
        int i, cpus = num_online_cpus() - 1;
        int cpu = smp_processor_id();

        /*
         * Can die spectacularly if this CPU isn't yet marked online
         */
        BUG_ON(!cpu_online(cpu));

        if (!cpus)
                return 0;

        if (spin_is_locked(&smp_call_lock)) {
                /*
                 * Some other processor is trying to make us do something
                 * but we're not going to respond... give up
                 */
                return -1;
                }

        /*
         * We will continue here, accepting the fact that
         * the kernel may deadlock if another CPU attempts
         * to call smp_call_function now...
         */

        data.func = kgdb_wait;
        data.info = NULL;
        atomic_set(&data.started, 0);
        data.wait = 0;

        spin_lock(&smp_call_lock);
        call_data = &data;
        mb();

        /* Send a message to all other CPUs and wait for them to respond */
        for (i = 0; i < NR_CPUS; i++)
                if (cpu_online(i) && i != cpu)
                        core_send_ipi(i, SMP_CALL_FUNCTION);

        /* Wait for response */
        /* FIXME: lock-up detection, backtrace on lock-up */
        while (atomic_read(&data.started) != cpus)
                barrier();

        call_data = NULL;
        spin_unlock(&smp_call_lock);
#endif

        return 0;
}

/*
 * This function does all command processing for interfacing to gdb.  It
 * returns 1 if you should skip the instruction at the trap address, 0
 * otherwise.
 */
void handle_exception (struct gdb_regs *regs)
{
        int trap;                       /* Trap type */
        int sigval;
        long addr;
        int length;
        char *ptr;
        unsigned long *stack;
        int i;
        int bflag = 0;

        kgdb_started = 1;

        /*
         * acquire the big kgdb spinlock
         */
        if (!spin_trylock(&kgdb_lock)) {
                /*
                 * some other CPU has the lock, we should go back to
                 * receive the gdb_wait IPC
                 */
                return;
        }

        /*
         * If we're in async_breakpoint(), restore the real EPC from
         * the breakpoint.
         */
        if (regs->cp0_epc == (unsigned long)async_breakinst) {
                regs->cp0_epc = async_bp.addr;
                async_bp.addr = 0;
        }

        /*
         * acquire the CPU spinlocks
         */
        for (i = num_online_cpus()-1; i >= 0; i--)
                if (__raw_spin_trylock(&kgdb_cpulock[i]) == 0)
                        panic("kgdb: couldn't get cpulock %d\n", i);

        /*
         * force other cpus to enter kgdb
         */
        kgdb_smp_call_kgdb_wait();

        /*
         * If we're in breakpoint() increment the PC
         */
        trap = (regs->cp0_cause & 0x7c) >> 2;
        if (trap == 9 && regs->cp0_epc == (unsigned long)breakinst)
                regs->cp0_epc += 4;

        /*
         * If we were single_stepping, restore the opcodes hoisted
         * for the breakpoint[s].
         */
        if (step_bp[0].addr) {
                *(unsigned *)step_bp[0].addr = step_bp[0].val;
                step_bp[0].addr = 0;

                if (step_bp[1].addr) {
                        *(unsigned *)step_bp[1].addr = step_bp[1].val;
                        step_bp[1].addr = 0;
                }
        }

        stack = (long *)regs->reg29;                    /* stack ptr */
        sigval = computeSignal(trap);

        /*
         * reply to host that an exception has occurred
         */
        ptr = output_buffer;

        /*
         * Send trap type (converted to signal)
         */
        *ptr++ = 'T';
        *ptr++ = hexchars[sigval >> 4];
        *ptr++ = hexchars[sigval & 0xf];

        /*
         * Send Error PC
         */
        *ptr++ = hexchars[REG_EPC >> 4];
        *ptr++ = hexchars[REG_EPC & 0xf];
        *ptr++ = ':';
        ptr = mem2hex((char *)&regs->cp0_epc, ptr, sizeof(long), 0);
        *ptr++ = ';';

        /*
         * Send frame pointer
         */
        *ptr++ = hexchars[REG_FP >> 4];
        *ptr++ = hexchars[REG_FP & 0xf];
        *ptr++ = ':';
        ptr = mem2hex((char *)&regs->reg30, ptr, sizeof(long), 0);
        *ptr++ = ';';

        /*
         * Send stack pointer
         */
        *ptr++ = hexchars[REG_SP >> 4];
        *ptr++ = hexchars[REG_SP & 0xf];
        *ptr++ = ':';
        ptr = mem2hex((char *)&regs->reg29, ptr, sizeof(long), 0);
        *ptr++ = ';';

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

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

                switch (input_buffer[0])
                {
                case '?':
                        output_buffer[0] = 'S';
                        output_buffer[1] = hexchars[sigval >> 4];
                        output_buffer[2] = hexchars[sigval & 0xf];
                        output_buffer[3] = 0;
                        break;

                /*
                 * Detach debugger; let CPU run
                 */
                case 'D':
                        putpacket(output_buffer);
                        goto finish_kgdb;
                        break;

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

                /*
                 * Return the value of the CPU registers
                 */
                case 'g':
                        ptr = output_buffer;
                        ptr = mem2hex((char *)&regs->reg0, ptr, 32*sizeof(long), 0); /* r0...r31 */
                        ptr = mem2hex((char *)&regs->cp0_status, ptr, 6*sizeof(long), 0); /* cp0 */
                        ptr = mem2hex((char *)&regs->fpr0, ptr, 32*sizeof(long), 0); /* f0...31 */
                        ptr = mem2hex((char *)&regs->cp1_fsr, ptr, 2*sizeof(long), 0); /* cp1 */
                        ptr = mem2hex((char *)&regs->frame_ptr, ptr, 2*sizeof(long), 0); /* frp */
                        ptr = mem2hex((char *)&regs->cp0_index, ptr, 16*sizeof(long), 0); /* cp0 */
                        break;

                /*
                 * set the value of the CPU registers - return OK
                 */
                case 'G':
                {
                        ptr = &input_buffer[1];
                        hex2mem(ptr, (char *)&regs->reg0, 32*sizeof(long), 0, 0);
                        ptr += 32*(2*sizeof(long));
                        hex2mem(ptr, (char *)&regs->cp0_status, 6*sizeof(long), 0, 0);
                        ptr += 6*(2*sizeof(long));
                        hex2mem(ptr, (char *)&regs->fpr0, 32*sizeof(long), 0, 0);
                        ptr += 32*(2*sizeof(long));
                        hex2mem(ptr, (char *)&regs->cp1_fsr, 2*sizeof(long), 0, 0);
                        ptr += 2*(2*sizeof(long));
                        hex2mem(ptr, (char *)&regs->frame_ptr, 2*sizeof(long), 0, 0);
                        ptr += 2*(2*sizeof(long));
                        hex2mem(ptr, (char *)&regs->cp0_index, 16*sizeof(long), 0, 0);
                        strcpy(output_buffer,"OK");
                 }
                break;

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

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

                /*
                 * XAA..AA,LLLL: Write LLLL escaped binary bytes at address AA.AA
                 */
                case 'X':
                        bflag = 1;
                        /* fall through */

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

                        if (hexToLong(&ptr, &addr)
                                && *ptr++ == ','
                                && hexToInt(&ptr, &length)
                                && *ptr++ == ':') {
                                if (hex2mem(ptr, (char *)addr, length, bflag, 1))
                                        strcpy(output_buffer, "OK");
                                else
                                        strcpy(output_buffer, "E03");
                        }
                        else
                                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 (hexToLong(&ptr, &addr))
                                regs->cp0_epc = addr;

                        goto exit_kgdb_exception;
                        break;

                /*
                 * kill the program; let us try to restart the machine
                 * Reset the whole machine.
                 */
                case 'k':
                case 'r':
                        machine_restart("kgdb restarts machine");
                        break;

                /*
                 * Step to next instruction
                 */
                case 's':
                        /*
                         * There is no single step insn in the MIPS ISA, so we
                         * use breakpoints and continue, instead.
                         */
                        single_step(regs);
                        goto exit_kgdb_exception;
                        /* NOTREACHED */
                        break;

                /*
                 * Set baud rate (bBB)
                 * FIXME: Needs to be written
                 */
                case 'b':
                {
#if 0
                        int baudrate;
                        extern void set_timer_3();

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

                        /* Convert baud rate to uart clock divider */

                        switch (baudrate)
                        {
                                case 38400:
                                        baudrate = 16;
                                        break;
                                case 19200:
                                        baudrate = 33;
                                        break;
                                case 9600:
                                        baudrate = 65;
                                        break;
                                default:
                                        baudrate = 0;
                                        strcpy(output_buffer,"B02");
                                        goto x1;
                        }

                        if (baudrate) {
                                putpacket("OK");        /* Ack before changing speed */
                                set_timer_3(baudrate); /* Set it */
                        }
#endif
                }
                break;

                }                       /* switch */

                /*
                 * reply to the request
                 */

                putpacket(output_buffer);

        } /* while */

        return;

finish_kgdb:
        restore_debug_traps();

exit_kgdb_exception:
        /* release locks so other CPUs can go */
        for (i = num_online_cpus()-1; i >= 0; i--)
                __raw_spin_unlock(&kgdb_cpulock[i]);
        spin_unlock(&kgdb_lock);

        __flush_cache_all();
        return;
}

/*
 * 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 breakpoint(void)
{
        if (!initialized)
                return;

        __asm__ __volatile__(
                        ".globl breakinst\n\t"
                        ".set\tnoreorder\n\t"
                        "nop\n"
                        "breakinst:\tbreak\n\t"
                        "nop\n\t"
                        ".set\treorder"
                        );
}

/* Nothing but the break; don't pollute any registers */
void async_breakpoint(void)
{
        __asm__ __volatile__(
                        ".globl async_breakinst\n\t"
                        ".set\tnoreorder\n\t"
                        "nop\n"
                        "async_breakinst:\tbreak\n\t"
                        "nop\n\t"
                        ".set\treorder"
                        );
}

void adel(void)
{
        __asm__ __volatile__(
                        ".globl\tadel\n\t"
                        "lui\t$8,0x8000\n\t"
                        "lw\t$9,1($8)\n\t"
                        );
}

/*
 * malloc is needed by gdb client in "call func()", even a private one
 * will make gdb happy
 */
static void * __attribute_used__ malloc(size_t size)
{
        return kmalloc(size, GFP_ATOMIC);
}

static void __attribute_used__ free (void *where)
{
        kfree(where);
}

#ifdef CONFIG_GDB_CONSOLE

void gdb_putsn(const char *str, int l)
{
        char outbuf[18];

        if (!kgdb_started)
                return;

        outbuf[0]='O';

        while(l) {
                int i = (l>8)?8:l;
                mem2hex((char *)str, &outbuf[1], i, 0);
                outbuf[(i*2)+1]=0;
                putpacket(outbuf);
                str += i;
                l -= i;
        }
}

static void gdb_console_write(struct console *con, const char *s, unsigned n)
{
        gdb_putsn(s, n);
}

static struct console gdb_console = {
        .name   = "gdb",
        .write  = gdb_console_write,
        .flags  = CON_PRINTBUFFER,
        .index  = -1
};

static int __init register_gdb_console(void)
{
        register_console(&gdb_console);

        return 0;
}

console_initcall(register_gdb_console);

#endif