patch-2.4.22 linux-2.4.22/arch/mips64/kernel/gdb-stub.c

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diff -urN linux-2.4.21/arch/mips64/kernel/gdb-stub.c linux-2.4.22/arch/mips64/kernel/gdb-stub.c
@@ -0,0 +1,1082 @@
+/*
+ *  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 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_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/mipsregs.h>
+#include <asm/pgtable.h>
+#include <asm/system.h>
+#include <asm/gdb-stub.h>
+#include <asm/inst.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);
+
+/*
+ * spin locks for smp case
+ */
+static spinlock_t kgdb_lock = SPIN_LOCK_UNLOCKED;
+static spinlock_t kgdb_cpulock[NR_CPUS] = { [0 ... NR_CPUS-1] = 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() & 0x7f;
+			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 may_fault)
+{
+	int i;
+	unsigned char ch;
+
+	for (i=0; i<count; i++)
+	{
+		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;
+
+	save_and_cli(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;
+	restore_flags(flags);
+}
+
+void restore_debug_traps(void)
+{
+	struct hard_trap_info *ht;
+	unsigned long flags;
+
+	save_and_cli(flags);
+	for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
+		set_except_vector(ht->tt, saved_vectors[ht->tt]);
+	restore_flags(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;
+
+	/* avoid deadlock if someone is make IPC */
+	if (spin_is_locked(&smp_call_lock))
+		return;
+
+	async_bp.addr = *epc;
+	*epc = (unsigned long)async_breakpoint;
+}
+
+void kgdb_wait(void *arg)
+{
+	unsigned flags;
+	int cpu = smp_processor_id();
+
+	local_irq_save(flags);
+
+	spin_lock(&kgdb_cpulock[cpu]);
+	spin_unlock(&kgdb_cpulock[cpu]);
+
+	local_irq_restore(flags);
+}
+
+
+/*
+ * 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;
+
+	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=0; i< smp_num_cpus; i++) 
+		if (spin_trylock(&kgdb_cpulock[i]) == 0)
+			panic("kgdb: couldn't get cpulock %d\n", i);
+
+	/*
+	 * force other cpus to enter kgdb
+	 */
+	smp_call_function(kgdb_wait, NULL, 0, 0);
+
+	/*
+	 * 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, 8, 0);
+	*ptr++ = ';';
+
+	/*
+	 * Send frame pointer
+	 */
+	*ptr++ = hexchars[REG_FP >> 4];
+	*ptr++ = hexchars[REG_FP & 0xf];
+	*ptr++ = ':';
+	ptr = mem2hex((char *)&regs->reg30, ptr, 8, 0);
+	*ptr++ = ';';
+
+	/*
+	 * Send stack pointer
+	 */
+	*ptr++ = hexchars[REG_SP >> 4];
+	*ptr++ = hexchars[REG_SP & 0xf];
+	*ptr++ = ':';
+	ptr = mem2hex((char *)&regs->reg29, ptr, 8, 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);
+
+		if (0) {
+#include <asm/sibyte/board.h>
+			prom_printf("got %c\n", input_buffer[0]);
+		}
+
+		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*8, 0); /* r0...r31 */
+			ptr = mem2hex((char *)&regs->cp0_status, ptr, 6*8, 0); /* cp0 */
+			ptr = mem2hex((char *)&regs->fpr0, ptr, 32*8, 0); /* f0...31 */
+			ptr = mem2hex((char *)&regs->cp1_fsr, ptr, 2*8, 0); /* cp1 */
+			ptr = mem2hex((char *)&regs->frame_ptr, ptr, 2*8, 0); /* frp */
+			ptr = mem2hex((char *)&regs->cp0_index, ptr, 16*8, 0); /* cp0 */
+			break;
+
+		/*
+		 * set the value of the CPU registers - return OK
+		 */
+		case 'G':
+		{
+			ptr = &input_buffer[1];
+			hex2mem(ptr, (char *)&regs->reg0, 32*8, 0);
+			ptr += 32*16;
+			hex2mem(ptr, (char *)&regs->cp0_status, 6*8, 0);
+			ptr += 6*16;
+			hex2mem(ptr, (char *)&regs->fpr0, 32*8, 0);
+			ptr += 32*16;
+			hex2mem(ptr, (char *)&regs->cp1_fsr, 2*8, 0);
+			ptr += 2*16;
+			hex2mem(ptr, (char *)&regs->frame_ptr, 2*8, 0);
+			ptr += 2*16;
+			hex2mem(ptr, (char *)&regs->cp0_index, 16*8, 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;
+
+		/*
+		 * 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, 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=0; i < smp_num_cpus; i++) 
+		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\t"
+			"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\t"
+			"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 *malloc(size_t size)
+{
+	return kmalloc(size, GFP_ATOMIC);
+}
+
+static void 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 kdev_t gdb_console_dev(struct console *con)
+{
+	return MKDEV(1, 3); /* /dev/null */
+}
+
+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,
+	.device	= gdb_console_dev,
+	.flags	= CON_PRINTBUFFER,
+	.index	= -1
+};
+
+__init void register_gdb_console(void)
+{
+	register_console(&gdb_console);
+}
+
+#endif
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)