xref: /linux-4.1.27/arch/cris/arch-v10/kernel/kgdb.c

/*!**************************************************************************
*!
*! FILE NAME  : kgdb.c
*!
*! DESCRIPTION: Implementation of the gdb stub with respect to ETRAX 100.
*!              It is a mix of arch/m68k/kernel/kgdb.c and cris_stub.c.
*!
*!---------------------------------------------------------------------------
*! HISTORY
*!
*! DATE         NAME            CHANGES
*! ----         ----            -------
*! Apr 26 1999  Hendrik Ruijter Initial version.
*! May  6 1999  Hendrik Ruijter Removed call to strlen in libc and removed
*!                              struct assignment as it generates calls to
*!                              memcpy in libc.
*! Jun 17 1999  Hendrik Ruijter Added gdb 4.18 support. 'X', 'qC' and 'qL'.
*! Jul 21 1999  Bjorn Wesen     eLinux port
*!
*!---------------------------------------------------------------------------
*!
*! (C) Copyright 1999, Axis Communications AB, LUND, SWEDEN
*!
*!**************************************************************************/
/* @(#) cris_stub.c 1.3 06/17/99 */

/*
 *  kgdb usage notes:
 *  -----------------
 *
 * If you select CONFIG_ETRAX_KGDB in the configuration, the kernel will be
 * built with different gcc flags: "-g" is added to get debug infos, and
 * "-fomit-frame-pointer" is omitted to make debugging easier. Since the
 * resulting kernel will be quite big (approx. > 7 MB), it will be stripped
 * before compresion. Such a kernel will behave just as usually, except if
 * given a "debug=<device>" command line option. (Only serial devices are
 * allowed for <device>, i.e. no printers or the like; possible values are
 * machine depedend and are the same as for the usual debug device, the one
 * for logging kernel messages.) If that option is given and the device can be
 * initialized, the kernel will connect to the remote gdb in trap_init(). The
 * serial parameters are fixed to 8N1 and 115200 bps, for easyness of
 * implementation.
 *
 * To start a debugging session, start that gdb with the debugging kernel
 * image (the one with the symbols, vmlinux.debug) named on the command line.
 * This file will be used by gdb to get symbol and debugging infos about the
 * kernel. Next, select remote debug mode by
 *    target remote <device>
 * where <device> is the name of the serial device over which the debugged
 * machine is connected. Maybe you have to adjust the baud rate by
 *    set remotebaud <rate>
 * or also other parameters with stty:
 *    shell stty ... </dev/...
 * If the kernel to debug has already booted, it waited for gdb and now
 * connects, and you'll see a breakpoint being reported. If the kernel isn't
 * running yet, start it now. The order of gdb and the kernel doesn't matter.
 * Another thing worth knowing about in the getting-started phase is how to
 * debug the remote protocol itself. This is activated with
 *    set remotedebug 1
 * gdb will then print out each packet sent or received. You'll also get some
 * messages about the gdb stub on the console of the debugged machine.
 *
 * If all that works, you can use lots of the usual debugging techniques on
 * the kernel, e.g. inspecting and changing variables/memory, setting
 * breakpoints, single stepping and so on. It's also possible to interrupt the
 * debugged kernel by pressing C-c in gdb. Have fun! :-)
 *
 * The gdb stub is entered (and thus the remote gdb gets control) in the
 * following situations:
 *
 *  - If breakpoint() is called. This is just after kgdb initialization, or if
 *    a breakpoint() call has been put somewhere into the kernel source.
 *    (Breakpoints can of course also be set the usual way in gdb.)
 *    In eLinux, we call breakpoint() in init/main.c after IRQ initialization.
 *
 *  - If there is a kernel exception, i.e. bad_super_trap() or die_if_kernel()
 *    are entered. All the CPU exceptions are mapped to (more or less..., see
 *    the hard_trap_info array below) appropriate signal, which are reported
 *    to gdb. die_if_kernel() is usually called after some kind of access
 *    error and thus is reported as SIGSEGV.
 *
 *  - When panic() is called. This is reported as SIGABRT.
 *
 *  - If C-c is received over the serial line, which is treated as
 *    SIGINT.
 *
 * Of course, all these signals are just faked for gdb, since there is no
 * signal concept as such for the kernel. It also isn't possible --obviously--
 * to set signal handlers from inside gdb, or restart the kernel with a
 * signal.
 *
 * Current limitations:
 *
 *  - While the kernel is stopped, interrupts are disabled for safety reasons
 *    (i.e., variables not changing magically or the like). But this also
 *    means that the clock isn't running anymore, and that interrupts from the
 *    hardware may get lost/not be served in time. This can cause some device
 *    errors...
 *
 *  - When single-stepping, only one instruction of the current thread is
 *    executed, but interrupts are allowed for that time and will be serviced
 *    if pending. Be prepared for that.
 *
 *  - All debugging happens in kernel virtual address space. There's no way to
 *    access physical memory not mapped in kernel space, or to access user
 *    space. A way to work around this is using get_user_long & Co. in gdb
 *    expressions, but only for the current process.
 *
 *  - Interrupting the kernel only works if interrupts are currently allowed,
 *    and the interrupt of the serial line isn't blocked by some other means
 *    (IPL too high, disabled, ...)
 *
 *  - The gdb stub is currently not reentrant, i.e. errors that happen therein
 *    (e.g. accessing invalid memory) may not be caught correctly. This could
 *    be removed in future by introducing a stack of struct registers.
 *
 */

/*
 *  To enable debugger support, two things need to happen.  One, a
 *  call to kgdb_init() 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().
 *
 *    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
 *
 */


#include <linux/string.h>
#include <linux/signal.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/linkage.h>
#include <linux/reboot.h>

#include <asm/setup.h>
#include <asm/ptrace.h>

#include <arch/svinto.h>
#include <asm/irq.h>

static int kgdb_started = 0;

/********************************* Register image ****************************/
/* Use the order of registers as defined in "AXIS ETRAX CRIS Programmer's
   Reference", p. 1-1, with the additional register definitions of the
   ETRAX 100LX in cris-opc.h.
   There are 16 general 32-bit registers, R0-R15, where R14 is the stack
   pointer, SP, and R15 is the program counter, PC.
   There are 16 special registers, P0-P15, where three of the unimplemented
   registers, P0, P4 and P8, are reserved as zero-registers. A read from
   any of these registers returns zero and a write has no effect. */

typedef
struct register_image
{
	/* Offset */
	unsigned int     r0;   /* 0x00 */
	unsigned int     r1;   /* 0x04 */
	unsigned int     r2;   /* 0x08 */
	unsigned int     r3;   /* 0x0C */
	unsigned int     r4;   /* 0x10 */
	unsigned int     r5;   /* 0x14 */
	unsigned int     r6;   /* 0x18 */
	unsigned int     r7;   /* 0x1C */
	unsigned int     r8;   /* 0x20 Frame pointer */
	unsigned int     r9;   /* 0x24 */
	unsigned int    r10;   /* 0x28 */
	unsigned int    r11;   /* 0x2C */
	unsigned int    r12;   /* 0x30 */
	unsigned int    r13;   /* 0x34 */
	unsigned int     sp;   /* 0x38 Stack pointer */
	unsigned int     pc;   /* 0x3C Program counter */

        unsigned char    p0;   /* 0x40 8-bit zero-register */
	unsigned char    vr;   /* 0x41 Version register */

        unsigned short   p4;   /* 0x42 16-bit zero-register */
	unsigned short  ccr;   /* 0x44 Condition code register */

	unsigned int    mof;   /* 0x46 Multiply overflow register */

        unsigned int     p8;   /* 0x4A 32-bit zero-register */
	unsigned int    ibr;   /* 0x4E Interrupt base register */
	unsigned int    irp;   /* 0x52 Interrupt return pointer */
	unsigned int    srp;   /* 0x56 Subroutine return pointer */
	unsigned int    bar;   /* 0x5A Breakpoint address register */
	unsigned int   dccr;   /* 0x5E Double condition code register */
	unsigned int    brp;   /* 0x62 Breakpoint return pointer (pc in caller) */
	unsigned int    usp;   /* 0x66 User mode stack pointer */
} registers;

/* Serial port, reads one character. ETRAX 100 specific. from debugport.c */
int getDebugChar (void);

/* Serial port, writes one character. ETRAX 100 specific. from debugport.c */
void putDebugChar (int val);

void enableDebugIRQ (void);

/******************** Prototypes for global functions. ***********************/

/* The string str is prepended with the GDB printout token and sent. */
void putDebugString (const unsigned char *str, int length); /* used by etrax100ser.c */

/* The hook for both static (compiled) and dynamic breakpoints set by GDB.
   ETRAX 100 specific. */
void handle_breakpoint (void);                          /* used by irq.c */

/* The hook for an interrupt generated by GDB. ETRAX 100 specific. */
void handle_interrupt (void);                           /* used by irq.c */

/* A static breakpoint to be used at startup. */
void breakpoint (void);                                 /* called by init/main.c */

/* From osys_int.c, executing_task contains the number of the current
   executing task in osys. Does not know of object-oriented threads. */
extern unsigned char executing_task;

/* The number of characters used for a 64 bit thread identifier. */
#define HEXCHARS_IN_THREAD_ID 16

/********************************** Packet I/O ******************************/
/* BUFMAX defines the maximum number of characters in
   inbound/outbound buffers */
#define BUFMAX 512

/* Run-length encoding maximum length. Send 64 at most. */
#define RUNLENMAX 64

/* The inbound/outbound buffers used in packet I/O */
static char remcomInBuffer[BUFMAX];
static char remcomOutBuffer[BUFMAX];

/* Error and warning messages. */
enum error_type
{
	SUCCESS, E01, E02, E03, E04, E05, E06, E07
};
static char *error_message[] =
{
	"",
	"E01 Set current or general thread - H[c,g] - internal error.",
	"E02 Change register content - P - cannot change read-only register.",
	"E03 Thread is not alive.", /* T, not used. */
	"E04 The command is not supported - [s,C,S,!,R,d,r] - internal error.",
	"E05 Change register content - P - the register is not implemented..",
	"E06 Change memory content - M - internal error.",
	"E07 Change register content - P - the register is not stored on the stack"
};
/********************************* Register image ****************************/
/* Use the order of registers as defined in "AXIS ETRAX CRIS Programmer's
   Reference", p. 1-1, with the additional register definitions of the
   ETRAX 100LX in cris-opc.h.
   There are 16 general 32-bit registers, R0-R15, where R14 is the stack
   pointer, SP, and R15 is the program counter, PC.
   There are 16 special registers, P0-P15, where three of the unimplemented
   registers, P0, P4 and P8, are reserved as zero-registers. A read from
   any of these registers returns zero and a write has no effect. */
enum register_name
{
	R0,  R1,   R2,  R3,
	R4,  R5,   R6,  R7,
	R8,  R9,   R10, R11,
	R12, R13,  SP,  PC,
	P0,  VR,   P2,  P3,
	P4,  CCR,  P6,  MOF,
	P8,  IBR,  IRP, SRP,
	BAR, DCCR, BRP, USP
};

/* The register sizes of the registers in register_name. An unimplemented register
   is designated by size 0 in this array. */
static int register_size[] =
{
	4, 4, 4, 4,
	4, 4, 4, 4,
	4, 4, 4, 4,
	4, 4, 4, 4,
	1, 1, 0, 0,
	2, 2, 0, 4,
	4, 4, 4, 4,
	4, 4, 4, 4
};

/* Contains the register image of the executing thread in the assembler
   part of the code in order to avoid horrible addressing modes. */
registers cris_reg;

/* FIXME: Should this be used? Delete otherwise. */
/* Contains the assumed consistency state of the register image. Uses the
   enum error_type for state information. */
static int consistency_status = SUCCESS;

/********************************** Handle exceptions ************************/
/* The variable cris_reg contains the register image associated with the
   current_thread_c variable. It is a complete register image created at
   entry. The reg_g contains a register image of a task where the general
   registers are taken from the stack and all special registers are taken
   from the executing task. It is associated with current_thread_g and used
   in order to provide access mainly for 'g', 'G' and 'P'.
*/

/********************************** Breakpoint *******************************/
/* Use an internal stack in the breakpoint and interrupt response routines */
#define INTERNAL_STACK_SIZE 1024
char internal_stack[INTERNAL_STACK_SIZE];

/* Due to the breakpoint return pointer, a state variable is needed to keep
   track of whether it is a static (compiled) or dynamic (gdb-invoked)
   breakpoint to be handled. A static breakpoint uses the content of register
   BRP as it is whereas a dynamic breakpoint requires subtraction with 2
   in order to execute the instruction. The first breakpoint is static. */
static unsigned char is_dyn_brkp = 0;

/********************************* String library ****************************/
/* Single-step over library functions creates trap loops. */

/* Copy char s2[] to s1[]. */
static char*
gdb_cris_strcpy (char *s1, const char *s2)
{
	char *s = s1;

	for (s = s1; (*s++ = *s2++) != '\0'; )
		;
	return (s1);
}

/* Find length of s[]. */
static int
gdb_cris_strlen (const char *s)
{
	const char *sc;

	for (sc = s; *sc != '\0'; sc++)
		;
	return (sc - s);
}

/* Find first occurrence of c in s[n]. */
static void*
gdb_cris_memchr (const void *s, int c, int n)
{
	const unsigned char uc = c;
	const unsigned char *su;

	for (su = s; 0 < n; ++su, --n)
		if (*su == uc)
			return ((void *)su);
	return (NULL);
}
/******************************* Standard library ****************************/
/* Single-step over library functions creates trap loops. */
/* Convert string to long. */
static int
gdb_cris_strtol (const char *s, char **endptr, int base)
{
	char *s1;
	char *sd;
	int x = 0;

	for (s1 = (char*)s; (sd = gdb_cris_memchr(hex_asc, *s1, base)) != NULL; ++s1)
		x = x * base + (sd - hex_asc);

        if (endptr)
        {
                /* Unconverted suffix is stored in endptr unless endptr is NULL. */
                *endptr = s1;
        }

	return x;
}

/********************************** Packet I/O ******************************/
/* Returns the integer equivalent of a hexadecimal character. */
static int
hex (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);
}

/* Convert the memory, pointed to by mem into hexadecimal representation.
   Put the result in buf, and return a pointer to the last character
   in buf (null). */

static char *
mem2hex(char *buf, unsigned char *mem, int count)
{
	int i;
	int ch;

        if (mem == NULL) {
                /* Bogus read from m0. FIXME: What constitutes a valid address? */
                for (i = 0; i < count; i++) {
                        *buf++ = '0';
                        *buf++ = '0';
                }
        } else {
                /* Valid mem address. */
                for (i = 0; i < count; i++) {
                        ch = *mem++;
			buf = hex_byte_pack(buf, ch);
                }
        }

        /* Terminate properly. */
	*buf = '\0';
	return (buf);
}

/* Convert the array, in hexadecimal representation, pointed to by buf into
   binary representation. Put the result in mem, and return a pointer to
   the character after the last byte written. */
static unsigned char*
hex2mem (unsigned char *mem, char *buf, int count)
{
	int i;
	unsigned char ch;
	for (i = 0; i < count; i++) {
		ch = hex (*buf++) << 4;
		ch = ch + hex (*buf++);
		*mem++ = ch;
	}
	return (mem);
}

/* Put the content of the array, in binary representation, pointed to by buf
   into memory pointed to by mem, and return a pointer to the character after
   the last byte written.
   Gdb will escape $, #, and the escape char (0x7d). */
static unsigned char*
bin2mem (unsigned char *mem, unsigned char *buf, int count)
{
	int i;
	unsigned char *next;
	for (i = 0; i < count; i++) {
		/* Check for any escaped characters. Be paranoid and
		   only unescape chars that should be escaped. */
		if (*buf == 0x7d) {
			next = buf + 1;
			if (*next == 0x3 || *next == 0x4 || *next == 0x5D) /* #, $, ESC */
				{
					buf++;
					*buf += 0x20;
				}
		}
		*mem++ = *buf++;
	}
	return (mem);
}

/* Await the sequence $<data>#<checksum> and store <data> in the array buffer
   returned. */
static void
getpacket (char *buffer)
{
	unsigned char checksum;
	unsigned char xmitcsum;
	int i;
	int count;
	char ch;
	do {
		while ((ch = getDebugChar ()) != '$')
			/* Wait for the start character $ and ignore all other characters */;
		checksum = 0;
		xmitcsum = -1;
		count = 0;
		/* Read until a # or the end of the buffer is reached */
		while (count < BUFMAX - 1) {
			ch = getDebugChar ();
			if (ch == '#')
				break;
			checksum = checksum + ch;
			buffer[count] = ch;
			count = count + 1;
		}
		buffer[count] = '\0';

		if (ch == '#') {
			xmitcsum = hex (getDebugChar ()) << 4;
			xmitcsum += hex (getDebugChar ());
			if (checksum != xmitcsum) {
				/* Wrong checksum */
				putDebugChar ('-');
			}
			else {
				/* Correct checksum */
				putDebugChar ('+');
				/* If sequence characters are received, reply with them */
				if (buffer[2] == ':') {
					putDebugChar (buffer[0]);
					putDebugChar (buffer[1]);
					/* Remove the sequence characters from the buffer */
					count = gdb_cris_strlen (buffer);
					for (i = 3; i <= count; i++)
						buffer[i - 3] = buffer[i];
				}
			}
		}
	} while (checksum != xmitcsum);
}

/* Send $<data>#<checksum> from the <data> in the array buffer. */

static void
putpacket(char *buffer)
{
	int checksum;
	int runlen;
	int encode;

	do {
		char *src = buffer;
		putDebugChar ('$');
		checksum = 0;
		while (*src) {
			/* Do run length encoding */
			putDebugChar (*src);
			checksum += *src;
			runlen = 0;
			while (runlen < RUNLENMAX && *src == src[runlen]) {
				runlen++;
			}
			if (runlen > 3) {
				/* Got a useful amount */
				putDebugChar ('*');
				checksum += '*';
				encode = runlen + ' ' - 4;
				putDebugChar (encode);
				checksum += encode;
				src += runlen;
			}
			else {
				src++;
			}
		}
		putDebugChar('#');
		putDebugChar(hex_asc_hi(checksum));
		putDebugChar(hex_asc_lo(checksum));
	} while(kgdb_started && (getDebugChar() != '+'));
}

/* The string str is prepended with the GDB printout token and sent. Required
   in traditional implementations. */
void
putDebugString (const unsigned char *str, int length)
{
        remcomOutBuffer[0] = 'O';
        mem2hex(&remcomOutBuffer[1], (unsigned char *)str, length);
        putpacket(remcomOutBuffer);
}

/********************************* Register image ****************************/
/* Write a value to a specified register in the register image of the current
   thread. Returns status code SUCCESS, E02 or E05. */
static int
write_register (int regno, char *val)
{
	int status = SUCCESS;
	registers *current_reg = &cris_reg;

        if (regno >= R0 && regno <= PC) {
		/* 32-bit register with simple offset. */
		hex2mem ((unsigned char *)current_reg + regno * sizeof(unsigned int),
			 val, sizeof(unsigned int));
	}
        else if (regno == P0 || regno == VR || regno == P4 || regno == P8) {
		/* Do not support read-only registers. */
		status = E02;
	}
        else if (regno == CCR) {
		/* 16 bit register with complex offset. (P4 is read-only, P6 is not implemented,
                   and P7 (MOF) is 32 bits in ETRAX 100LX. */
		hex2mem ((unsigned char *)&(current_reg->ccr) + (regno-CCR) * sizeof(unsigned short),
			 val, sizeof(unsigned short));
	}
	else if (regno >= MOF && regno <= USP) {
		/* 32 bit register with complex offset.  (P8 has been taken care of.) */
		hex2mem ((unsigned char *)&(current_reg->ibr) + (regno-IBR) * sizeof(unsigned int),
			 val, sizeof(unsigned int));
	}
        else {
		/* Do not support nonexisting or unimplemented registers (P2, P3, and P6). */
		status = E05;
	}
	return status;
}

/* Read a value from a specified register in the register image. Returns the
   value in the register or -1 for non-implemented registers.
   Should check consistency_status after a call which may be E05 after changes
   in the implementation. */
static int
read_register (char regno, unsigned int *valptr)
{
	registers *current_reg = &cris_reg;

	if (regno >= R0 && regno <= PC) {
		/* 32-bit register with simple offset. */
		*valptr = *(unsigned int *)((char *)current_reg + regno * sizeof(unsigned int));
                return SUCCESS;
	}
	else if (regno == P0 || regno == VR) {
		/* 8 bit register with complex offset. */
		*valptr = (unsigned int)(*(unsigned char *)
                                         ((char *)&(current_reg->p0) + (regno-P0) * sizeof(char)));
                return SUCCESS;
	}
	else if (regno == P4 || regno == CCR) {
		/* 16 bit register with complex offset. */
		*valptr = (unsigned int)(*(unsigned short *)
                                         ((char *)&(current_reg->p4) + (regno-P4) * sizeof(unsigned short)));
                return SUCCESS;
	}
	else if (regno >= MOF && regno <= USP) {
		/* 32 bit register with complex offset. */
		*valptr = *(unsigned int *)((char *)&(current_reg->p8)
                                            + (regno-P8) * sizeof(unsigned int));
                return SUCCESS;
	}
	else {
		/* Do not support nonexisting or unimplemented registers (P2, P3, and P6). */
		consistency_status = E05;
		return E05;
	}
}

/********************************** Handle exceptions ************************/
/* Build and send a response packet in order to inform the host the
   stub is stopped. TAAn...:r...;n...:r...;n...:r...;
                    AA = signal number
                    n... = register number (hex)
                    r... = register contents
                    n... = `thread'
                    r... = thread process ID.  This is a hex integer.
                    n... = other string not starting with valid hex digit.
                    gdb should ignore this n,r pair and go on to the next.
                    This way we can extend the protocol. */
static void
stub_is_stopped(int sigval)
{
	char *ptr = remcomOutBuffer;
	int regno;

	unsigned int reg_cont;
	int status;

	/* Send trap type (converted to signal) */

	*ptr++ = 'T';
	ptr = hex_byte_pack(ptr, sigval);

	/* Send register contents. We probably only need to send the
	 * PC, frame pointer and stack pointer here. Other registers will be
	 * explicitly asked for. But for now, send all.
	 */

	for (regno = R0; regno <= USP; regno++) {
		/* Store n...:r...; for the registers in the buffer. */

                status = read_register (regno, &reg_cont);

		if (status == SUCCESS) {
			ptr = hex_byte_pack(ptr, regno);
                        *ptr++ = ':';

                        ptr = mem2hex(ptr, (unsigned char *)&reg_cont,
                                      register_size[regno]);
                        *ptr++ = ';';
                }

	}

	/* null-terminate and send it off */

	*ptr = 0;

	putpacket (remcomOutBuffer);
}

/* Performs a complete re-start from scratch. */
static void
kill_restart (void)
{
	machine_restart("");
}

/* All expected commands are sent from remote.c. Send a response according
   to the description in remote.c. */
void
handle_exception (int sigval)
{
	/* Send response. */

	stub_is_stopped (sigval);

	for (;;) {
		remcomOutBuffer[0] = '\0';
		getpacket (remcomInBuffer);
		switch (remcomInBuffer[0]) {
			case 'g':
				/* Read registers: g
				   Success: Each byte of register data is described by two hex digits.
				   Registers are in the internal order for GDB, and the bytes
				   in a register  are in the same order the machine uses.
				   Failure: void. */

				mem2hex(remcomOutBuffer, (char *)&cris_reg, sizeof(registers));
				break;

			case 'G':
				/* Write registers. GXX..XX
				   Each byte of register data  is described by two hex digits.
				   Success: OK
				   Failure: void. */
				hex2mem((char *)&cris_reg, &remcomInBuffer[1], sizeof(registers));
				gdb_cris_strcpy (remcomOutBuffer, "OK");
				break;

			case 'P':
				/* Write register. Pn...=r...
				   Write register n..., hex value without 0x, with value r...,
				   which contains a hex value without 0x and two hex digits
				   for each byte in the register (target byte order). P1f=11223344 means
				   set register 31 to 44332211.
				   Success: OK
				   Failure: E02, E05 */
				{
					char *suffix;
					int regno = gdb_cris_strtol (&remcomInBuffer[1], &suffix, 16);
					int status;
					status = write_register (regno, suffix+1);

					switch (status) {
						case E02:
							/* Do not support read-only registers. */
							gdb_cris_strcpy (remcomOutBuffer, error_message[E02]);
							break;
						case E05:
							/* Do not support non-existing registers. */
							gdb_cris_strcpy (remcomOutBuffer, error_message[E05]);
							break;
						case E07:
							/* Do not support non-existing registers on the stack. */
							gdb_cris_strcpy (remcomOutBuffer, error_message[E07]);
							break;
						default:
							/* Valid register number. */
							gdb_cris_strcpy (remcomOutBuffer, "OK");
							break;
					}
				}
				break;

			case 'm':
				/* Read from memory. mAA..AA,LLLL
				   AA..AA is the address and LLLL is the length.
				   Success: XX..XX is the memory content.  Can be fewer bytes than
				   requested if only part of the data may be read. m6000120a,6c means
				   retrieve 108 byte from base address 6000120a.
				   Failure: void. */
				{
                                        char *suffix;
					unsigned char *addr = (unsigned char *)gdb_cris_strtol(&remcomInBuffer[1],
                                                                                               &suffix, 16);                                        int length = gdb_cris_strtol(suffix+1, 0, 16);

                                        mem2hex(remcomOutBuffer, addr, length);
                                }
				break;

			case 'X':
				/* Write to memory. XAA..AA,LLLL:XX..XX
				   AA..AA is the start address,  LLLL is the number of bytes, and
				   XX..XX is the binary data.
				   Success: OK
				   Failure: void. */
			case 'M':
				/* Write to memory. MAA..AA,LLLL:XX..XX
				   AA..AA is the start address,  LLLL is the number of bytes, and
				   XX..XX is the hexadecimal data.
				   Success: OK
				   Failure: void. */
				{
					char *lenptr;
					char *dataptr;
					unsigned char *addr = (unsigned char *)gdb_cris_strtol(&remcomInBuffer[1],
										      &lenptr, 16);
					int length = gdb_cris_strtol(lenptr+1, &dataptr, 16);
					if (*lenptr == ',' && *dataptr == ':') {
						if (remcomInBuffer[0] == 'M') {
							hex2mem(addr, dataptr + 1, length);
						}
						else /* X */ {
							bin2mem(addr, dataptr + 1, length);
						}
						gdb_cris_strcpy (remcomOutBuffer, "OK");
					}
					else {
						gdb_cris_strcpy (remcomOutBuffer, error_message[E06]);
					}
				}
				break;

			case 'c':
				/* Continue execution. cAA..AA
				   AA..AA is the address where execution is resumed. If AA..AA is
				   omitted, resume at the present address.
				   Success: return to the executing thread.
				   Failure: will never know. */
				if (remcomInBuffer[1] != '\0') {
					cris_reg.pc = gdb_cris_strtol (&remcomInBuffer[1], 0, 16);
				}
				enableDebugIRQ();
				return;

			case 's':
				/* Step. sAA..AA
				   AA..AA is the address where execution is resumed. If AA..AA is
				   omitted, resume at the present address. Success: return to the
				   executing thread. Failure: will never know.

				   Should never be invoked. The single-step is implemented on
				   the host side. If ever invoked, it is an internal error E04. */
				gdb_cris_strcpy (remcomOutBuffer, error_message[E04]);
				putpacket (remcomOutBuffer);
				return;

			case '?':
				/* The last signal which caused a stop. ?
				   Success: SAA, where AA is the signal number.
				   Failure: void. */
				remcomOutBuffer[0] = 'S';
				remcomOutBuffer[1] = hex_asc_hi(sigval);
				remcomOutBuffer[2] = hex_asc_lo(sigval);
				remcomOutBuffer[3] = 0;
				break;

			case 'D':
				/* Detach from host. D
				   Success: OK, and return to the executing thread.
				   Failure: will never know */
				putpacket ("OK");
				return;

			case 'k':
			case 'r':
				/* kill request or reset request.
				   Success: restart of target.
				   Failure: will never know. */
				kill_restart ();
				break;

			case 'C':
			case 'S':
			case '!':
			case 'R':
			case 'd':
				/* Continue with signal sig. Csig;AA..AA
				   Step with signal sig. Ssig;AA..AA
				   Use the extended remote protocol. !
				   Restart the target system. R0
				   Toggle debug flag. d
				   Search backwards. tAA:PP,MM
				   Not supported: E04 */
				gdb_cris_strcpy (remcomOutBuffer, error_message[E04]);
				break;

			default:
				/* The stub should ignore other request and send an empty
				   response ($#<checksum>). This way we can extend the protocol and GDB
				   can tell whether the stub it is talking to uses the old or the new. */
				remcomOutBuffer[0] = 0;
				break;
		}
		putpacket(remcomOutBuffer);
	}
}

/********************************** Breakpoint *******************************/
/* The hook for both a static (compiled) and a dynamic breakpoint set by GDB.
   An internal stack is used by the stub. The register image of the caller is
   stored in the structure register_image.
   Interactive communication with the host is handled by handle_exception and
   finally the register image is restored. */

void kgdb_handle_breakpoint(void);

asm ("\n"
"  .global kgdb_handle_breakpoint\n"
"kgdb_handle_breakpoint:\n"
";;\n"
";; Response to the break-instruction\n"
";;\n"
";; Create a register image of the caller\n"
";;\n"
"  move     $dccr,[cris_reg+0x5E] ; Save the flags in DCCR before disable interrupts\n"
"  di                        ; Disable interrupts\n"
"  move.d   $r0,[cris_reg]        ; Save R0\n"
"  move.d   $r1,[cris_reg+0x04]   ; Save R1\n"
"  move.d   $r2,[cris_reg+0x08]   ; Save R2\n"
"  move.d   $r3,[cris_reg+0x0C]   ; Save R3\n"
"  move.d   $r4,[cris_reg+0x10]   ; Save R4\n"
"  move.d   $r5,[cris_reg+0x14]   ; Save R5\n"
"  move.d   $r6,[cris_reg+0x18]   ; Save R6\n"
"  move.d   $r7,[cris_reg+0x1C]   ; Save R7\n"
"  move.d   $r8,[cris_reg+0x20]   ; Save R8\n"
"  move.d   $r9,[cris_reg+0x24]   ; Save R9\n"
"  move.d   $r10,[cris_reg+0x28]  ; Save R10\n"
"  move.d   $r11,[cris_reg+0x2C]  ; Save R11\n"
"  move.d   $r12,[cris_reg+0x30]  ; Save R12\n"
"  move.d   $r13,[cris_reg+0x34]  ; Save R13\n"
"  move.d   $sp,[cris_reg+0x38]   ; Save SP (R14)\n"
";; Due to the old assembler-versions BRP might not be recognized\n"
"  .word 0xE670              ; move brp,$r0\n"
"  subq     2,$r0             ; Set to address of previous instruction.\n"
"  move.d   $r0,[cris_reg+0x3c]   ; Save the address in PC (R15)\n"
"  clear.b  [cris_reg+0x40]      ; Clear P0\n"
"  move     $vr,[cris_reg+0x41]   ; Save special register P1\n"
"  clear.w  [cris_reg+0x42]      ; Clear P4\n"
"  move     $ccr,[cris_reg+0x44]  ; Save special register CCR\n"
"  move     $mof,[cris_reg+0x46]  ; P7\n"
"  clear.d  [cris_reg+0x4A]      ; Clear P8\n"
"  move     $ibr,[cris_reg+0x4E]  ; P9,\n"
"  move     $irp,[cris_reg+0x52]  ; P10,\n"
"  move     $srp,[cris_reg+0x56]  ; P11,\n"
"  move     $dtp0,[cris_reg+0x5A] ; P12, register BAR, assembler might not know BAR\n"
"                            ; P13, register DCCR already saved\n"
";; Due to the old assembler-versions BRP might not be recognized\n"
"  .word 0xE670              ; move brp,r0\n"
";; Static (compiled) breakpoints must return to the next instruction in order\n"
";; to avoid infinite loops. Dynamic (gdb-invoked) must restore the instruction\n"
";; in order to execute it when execution is continued.\n"
"  test.b   [is_dyn_brkp]    ; Is this a dynamic breakpoint?\n"
"  beq      is_static         ; No, a static breakpoint\n"
"  nop\n"
"  subq     2,$r0              ; rerun the instruction the break replaced\n"
"is_static:\n"
"  moveq    1,$r1\n"
"  move.b   $r1,[is_dyn_brkp] ; Set the state variable to dynamic breakpoint\n"
"  move.d   $r0,[cris_reg+0x62]    ; Save the return address in BRP\n"
"  move     $usp,[cris_reg+0x66]   ; USP\n"
";;\n"
";; Handle the communication\n"
";;\n"
"  move.d   internal_stack+1020,$sp ; Use the internal stack which grows upward\n"
"  moveq    5,$r10                   ; SIGTRAP\n"
"  jsr      handle_exception       ; Interactive routine\n"
";;\n"
";; Return to the caller\n"
";;\n"
"   move.d  [cris_reg],$r0         ; Restore R0\n"
"   move.d  [cris_reg+0x04],$r1    ; Restore R1\n"
"   move.d  [cris_reg+0x08],$r2    ; Restore R2\n"
"   move.d  [cris_reg+0x0C],$r3    ; Restore R3\n"
"   move.d  [cris_reg+0x10],$r4    ; Restore R4\n"
"   move.d  [cris_reg+0x14],$r5    ; Restore R5\n"
"   move.d  [cris_reg+0x18],$r6    ; Restore R6\n"
"   move.d  [cris_reg+0x1C],$r7    ; Restore R7\n"
"   move.d  [cris_reg+0x20],$r8    ; Restore R8\n"
"   move.d  [cris_reg+0x24],$r9    ; Restore R9\n"
"   move.d  [cris_reg+0x28],$r10   ; Restore R10\n"
"   move.d  [cris_reg+0x2C],$r11   ; Restore R11\n"
"   move.d  [cris_reg+0x30],$r12   ; Restore R12\n"
"   move.d  [cris_reg+0x34],$r13   ; Restore R13\n"
";;\n"
";; FIXME: Which registers should be restored?\n"
";;\n"
"   move.d  [cris_reg+0x38],$sp    ; Restore SP (R14)\n"
"   move    [cris_reg+0x56],$srp   ; Restore the subroutine return pointer.\n"
"   move    [cris_reg+0x5E],$dccr  ; Restore DCCR\n"
"   move    [cris_reg+0x66],$usp   ; Restore USP\n"
"   jump    [cris_reg+0x62]       ; A jump to the content in register BRP works.\n"
"   nop                       ;\n"
"\n");

/* The hook for an interrupt generated by GDB. An internal stack is used
   by the stub. The register image of the caller is stored in the structure
   register_image. Interactive communication with the host is handled by
   handle_exception and finally the register image is restored. Due to the
   old assembler which does not recognise the break instruction and the
   breakpoint return pointer hex-code is used. */

void kgdb_handle_serial(void);

asm ("\n"
"  .global kgdb_handle_serial\n"
"kgdb_handle_serial:\n"
";;\n"
";; Response to a serial interrupt\n"
";;\n"
"\n"
"  move     $dccr,[cris_reg+0x5E] ; Save the flags in DCCR\n"
"  di                        ; Disable interrupts\n"
"  move.d   $r0,[cris_reg]        ; Save R0\n"
"  move.d   $r1,[cris_reg+0x04]   ; Save R1\n"
"  move.d   $r2,[cris_reg+0x08]   ; Save R2\n"
"  move.d   $r3,[cris_reg+0x0C]   ; Save R3\n"
"  move.d   $r4,[cris_reg+0x10]   ; Save R4\n"
"  move.d   $r5,[cris_reg+0x14]   ; Save R5\n"
"  move.d   $r6,[cris_reg+0x18]   ; Save R6\n"
"  move.d   $r7,[cris_reg+0x1C]   ; Save R7\n"
"  move.d   $r8,[cris_reg+0x20]   ; Save R8\n"
"  move.d   $r9,[cris_reg+0x24]   ; Save R9\n"
"  move.d   $r10,[cris_reg+0x28]  ; Save R10\n"
"  move.d   $r11,[cris_reg+0x2C]  ; Save R11\n"
"  move.d   $r12,[cris_reg+0x30]  ; Save R12\n"
"  move.d   $r13,[cris_reg+0x34]  ; Save R13\n"
"  move.d   $sp,[cris_reg+0x38]   ; Save SP (R14)\n"
"  move     $irp,[cris_reg+0x3c]  ; Save the address in PC (R15)\n"
"  clear.b  [cris_reg+0x40]      ; Clear P0\n"
"  move     $vr,[cris_reg+0x41]   ; Save special register P1,\n"
"  clear.w  [cris_reg+0x42]      ; Clear P4\n"
"  move     $ccr,[cris_reg+0x44]  ; Save special register CCR\n"
"  move     $mof,[cris_reg+0x46]  ; P7\n"
"  clear.d  [cris_reg+0x4A]      ; Clear P8\n"
"  move     $ibr,[cris_reg+0x4E]  ; P9,\n"
"  move     $irp,[cris_reg+0x52]  ; P10,\n"
"  move     $srp,[cris_reg+0x56]  ; P11,\n"
"  move     $dtp0,[cris_reg+0x5A] ; P12, register BAR, assembler might not know BAR\n"
"                            ; P13, register DCCR already saved\n"
";; Due to the old assembler-versions BRP might not be recognized\n"
"  .word 0xE670              ; move brp,r0\n"
"  move.d   $r0,[cris_reg+0x62]   ; Save the return address in BRP\n"
"  move     $usp,[cris_reg+0x66]  ; USP\n"
"\n"
";; get the serial character (from debugport.c) and check if it is a ctrl-c\n"
"\n"
"  jsr getDebugChar\n"
"  cmp.b 3, $r10\n"
"  bne goback\n"
"  nop\n"
"\n"
"  move.d  [cris_reg+0x5E], $r10		; Get DCCR\n"
"  btstq	   8, $r10			; Test the U-flag.\n"
"  bmi	   goback\n"
"  nop\n"
"\n"
";;\n"
";; Handle the communication\n"
";;\n"
"  move.d   internal_stack+1020,$sp ; Use the internal stack\n"
"  moveq    2,$r10                   ; SIGINT\n"
"  jsr      handle_exception       ; Interactive routine\n"
"\n"
"goback:\n"
";;\n"
";; Return to the caller\n"
";;\n"
"   move.d  [cris_reg],$r0         ; Restore R0\n"
"   move.d  [cris_reg+0x04],$r1    ; Restore R1\n"
"   move.d  [cris_reg+0x08],$r2    ; Restore R2\n"
"   move.d  [cris_reg+0x0C],$r3    ; Restore R3\n"
"   move.d  [cris_reg+0x10],$r4    ; Restore R4\n"
"   move.d  [cris_reg+0x14],$r5    ; Restore R5\n"
"   move.d  [cris_reg+0x18],$r6    ; Restore R6\n"
"   move.d  [cris_reg+0x1C],$r7    ; Restore R7\n"
"   move.d  [cris_reg+0x20],$r8    ; Restore R8\n"
"   move.d  [cris_reg+0x24],$r9    ; Restore R9\n"
"   move.d  [cris_reg+0x28],$r10   ; Restore R10\n"
"   move.d  [cris_reg+0x2C],$r11   ; Restore R11\n"
"   move.d  [cris_reg+0x30],$r12   ; Restore R12\n"
"   move.d  [cris_reg+0x34],$r13   ; Restore R13\n"
";;\n"
";; FIXME: Which registers should be restored?\n"
";;\n"
"   move.d  [cris_reg+0x38],$sp    ; Restore SP (R14)\n"
"   move    [cris_reg+0x56],$srp   ; Restore the subroutine return pointer.\n"
"   move    [cris_reg+0x5E],$dccr  ; Restore DCCR\n"
"   move    [cris_reg+0x66],$usp   ; Restore USP\n"
"   reti                      ; Return from the interrupt routine\n"
"   nop\n"
"\n");

/* Use this static breakpoint in the start-up only. */

void
breakpoint(void)
{
	kgdb_started = 1;
	is_dyn_brkp = 0;     /* This is a static, not a dynamic breakpoint. */
	__asm__ volatile ("break 8"); /* Jump to handle_breakpoint. */
}

/* initialize kgdb. doesn't break into the debugger, but sets up irq and ports */

void
kgdb_init(void)
{
	/* could initialize debug port as well but it's done in head.S already... */

        /* breakpoint handler is now set in irq.c */
	set_int_vector(8, kgdb_handle_serial);

	enableDebugIRQ();
}

/****************************** End of file **********************************/