kgdb_stub.c

linux-2.6.15.6

	char *src;
	int runlen;
	int encode;

	do {
		src = buffer;
		put_debug_char('$');
		checksum = 0;

		/* Continue while we still have chars left */
		while (*src) {
			/* Check for runs up to 99 chars long */
			for (runlen = 1; runlen < 99; runlen++) {
				if (src[0] != src[runlen])
					break;
			}

			if (runlen > 3) {
				/* Got a useful amount, send encoding */
				encode = runlen + ' ' - 4;
				put_debug_char(*src);   checksum += *src;
				put_debug_char('*');    checksum += '*';
				put_debug_char(encode); checksum += encode;
				src += runlen;
			} else {
				/* Otherwise just send the current char */
				put_debug_char(*src);   checksum += *src;
				src += 1;
			}
		}

		/* '#' Separator, put high and low components of checksum */
		put_debug_char('#');
		put_debug_char(highhex(checksum));
		put_debug_char(lowhex(checksum));
	}
	while ((get_debug_char()) != '+');	/* While no ack */
}

/* A bus error has occurred - perform a longjmp to return execution and
   allow handling of the error */
static void kgdb_handle_bus_error(void)
{
	longjmp(rem_com_env, 1);
}

/* Translate SH-3/4 exception numbers to unix-like signal values */
static int compute_signal(const int excep_code)
{
	int sigval;

	switch (excep_code) {

	case INVALID_INSN_VEC:
	case INVALID_SLOT_VEC:
		sigval = SIGILL;
		break;
	case ADDRESS_ERROR_LOAD_VEC:
	case ADDRESS_ERROR_STORE_VEC:
		sigval = SIGSEGV;
		break;

	case SERIAL_BREAK_VEC:
	case NMI_VEC:
		sigval = SIGINT;
		break;

	case USER_BREAK_VEC:
	case TRAP_VEC:
		sigval = SIGTRAP;
		break;

	default:
		sigval = SIGBUS;	/* "software generated" */
		break;
	}

	return (sigval);
}

/* Make a local copy of the registers passed into the handler (bletch) */
static void kgdb_regs_to_gdb_regs(const struct kgdb_regs *regs,
				  int *gdb_regs)
{
	gdb_regs[R0] = regs->regs[R0];
	gdb_regs[R1] = regs->regs[R1];
	gdb_regs[R2] = regs->regs[R2];
	gdb_regs[R3] = regs->regs[R3];
	gdb_regs[R4] = regs->regs[R4];
	gdb_regs[R5] = regs->regs[R5];
	gdb_regs[R6] = regs->regs[R6];
	gdb_regs[R7] = regs->regs[R7];
	gdb_regs[R8] = regs->regs[R8];
	gdb_regs[R9] = regs->regs[R9];
	gdb_regs[R10] = regs->regs[R10];
	gdb_regs[R11] = regs->regs[R11];
	gdb_regs[R12] = regs->regs[R12];
	gdb_regs[R13] = regs->regs[R13];
	gdb_regs[R14] = regs->regs[R14];
	gdb_regs[R15] = regs->regs[R15];
	gdb_regs[PC] = regs->pc;
	gdb_regs[PR] = regs->pr;
	gdb_regs[GBR] = regs->gbr;
	gdb_regs[MACH] = regs->mach;
	gdb_regs[MACL] = regs->macl;
	gdb_regs[SR] = regs->sr;
	gdb_regs[VBR] = regs->vbr;
}

/* Copy local gdb registers back to kgdb regs, for later copy to kernel */
static void gdb_regs_to_kgdb_regs(const int *gdb_regs,
				  struct kgdb_regs *regs)
{
	regs->regs[R0] = gdb_regs[R0];
	regs->regs[R1] = gdb_regs[R1];
	regs->regs[R2] = gdb_regs[R2];
	regs->regs[R3] = gdb_regs[R3];
	regs->regs[R4] = gdb_regs[R4];
	regs->regs[R5] = gdb_regs[R5];
	regs->regs[R6] = gdb_regs[R6];
	regs->regs[R7] = gdb_regs[R7];
	regs->regs[R8] = gdb_regs[R8];
	regs->regs[R9] = gdb_regs[R9];
	regs->regs[R10] = gdb_regs[R10];
	regs->regs[R11] = gdb_regs[R11];
	regs->regs[R12] = gdb_regs[R12];
	regs->regs[R13] = gdb_regs[R13];
	regs->regs[R14] = gdb_regs[R14];
	regs->regs[R15] = gdb_regs[R15];
	regs->pc = gdb_regs[PC];
	regs->pr = gdb_regs[PR];
	regs->gbr = gdb_regs[GBR];
	regs->mach = gdb_regs[MACH];
	regs->macl = gdb_regs[MACL];
	regs->sr = gdb_regs[SR];
	regs->vbr = gdb_regs[VBR];
}

#ifdef CONFIG_KGDB_THREAD
/* Make a local copy of registers from the specified thread */
asmlinkage void ret_from_fork(void);
static void thread_regs_to_gdb_regs(const struct task_struct *thread,
				    int *gdb_regs)
{
	int regno;
	int *tregs;

	/* Initialize to zero */
	for (regno = 0; regno < MAXREG; regno++)
		gdb_regs[regno] = 0;

	/* Just making sure... */
	if (thread == NULL)
		return;

	/* A new fork has pt_regs on the stack from a fork() call */
	if (thread->thread.pc == (unsigned long)ret_from_fork) {

		int vbr_val;
		struct pt_regs *kregs;
		kregs = (struct pt_regs*)thread->thread.sp;

		gdb_regs[R0] = kregs->regs[R0];
		gdb_regs[R1] = kregs->regs[R1];
		gdb_regs[R2] = kregs->regs[R2];
		gdb_regs[R3] = kregs->regs[R3];
		gdb_regs[R4] = kregs->regs[R4];
		gdb_regs[R5] = kregs->regs[R5];
		gdb_regs[R6] = kregs->regs[R6];
		gdb_regs[R7] = kregs->regs[R7];
		gdb_regs[R8] = kregs->regs[R8];
		gdb_regs[R9] = kregs->regs[R9];
		gdb_regs[R10] = kregs->regs[R10];
		gdb_regs[R11] = kregs->regs[R11];
		gdb_regs[R12] = kregs->regs[R12];
		gdb_regs[R13] = kregs->regs[R13];
		gdb_regs[R14] = kregs->regs[R14];
		gdb_regs[R15] = kregs->regs[R15];
		gdb_regs[PC] = kregs->pc;
		gdb_regs[PR] = kregs->pr;
		gdb_regs[GBR] = kregs->gbr;
		gdb_regs[MACH] = kregs->mach;
		gdb_regs[MACL] = kregs->macl;
		gdb_regs[SR] = kregs->sr;

		asm("stc vbr, %0":"=r"(vbr_val));
		gdb_regs[VBR] = vbr_val;
		return;
	}

	/* Otherwise, we have only some registers from switch_to() */
	tregs = (int *)thread->thread.sp;
	gdb_regs[R15] = (int)tregs;
	gdb_regs[R14] = *tregs++;
	gdb_regs[R13] = *tregs++;
	gdb_regs[R12] = *tregs++;
	gdb_regs[R11] = *tregs++;
	gdb_regs[R10] = *tregs++;
	gdb_regs[R9] = *tregs++;
	gdb_regs[R8] = *tregs++;
	gdb_regs[PR] = *tregs++;
	gdb_regs[GBR] = *tregs++;
	gdb_regs[PC] = thread->thread.pc;
}
#endif /* CONFIG_KGDB_THREAD */

/* Calculate the new address for after a step */
static short *get_step_address(void)
{
	short op = *(short *) trap_registers.pc;
	long addr;

	/* BT */
	if (OPCODE_BT(op)) {
		if (trap_registers.sr & SR_T_BIT_MASK)
			addr = trap_registers.pc + 4 + OPCODE_BTF_DISP(op);
		else
			addr = trap_registers.pc + 2;
	}

	/* BTS */
	else if (OPCODE_BTS(op)) {
		if (trap_registers.sr & SR_T_BIT_MASK)
			addr = trap_registers.pc + 4 + OPCODE_BTF_DISP(op);
		else
			addr = trap_registers.pc + 4;	/* Not in delay slot */
	}

	/* BF */
	else if (OPCODE_BF(op)) {
		if (!(trap_registers.sr & SR_T_BIT_MASK))
			addr = trap_registers.pc + 4 + OPCODE_BTF_DISP(op);
		else
			addr = trap_registers.pc + 2;
	}

	/* BFS */
	else if (OPCODE_BFS(op)) {
		if (!(trap_registers.sr & SR_T_BIT_MASK))
			addr = trap_registers.pc + 4 + OPCODE_BTF_DISP(op);
		else
			addr = trap_registers.pc + 4;	/* Not in delay slot */
	}

	/* BRA */
	else if (OPCODE_BRA(op))
		addr = trap_registers.pc + 4 + OPCODE_BRA_DISP(op);

	/* BRAF */
	else if (OPCODE_BRAF(op))
		addr = trap_registers.pc + 4
		    + trap_registers.regs[OPCODE_BRAF_REG(op)];

	/* BSR */
	else if (OPCODE_BSR(op))
		addr = trap_registers.pc + 4 + OPCODE_BSR_DISP(op);

	/* BSRF */
	else if (OPCODE_BSRF(op))
		addr = trap_registers.pc + 4
		    + trap_registers.regs[OPCODE_BSRF_REG(op)];

	/* JMP */
	else if (OPCODE_JMP(op))
		addr = trap_registers.regs[OPCODE_JMP_REG(op)];

	/* JSR */
	else if (OPCODE_JSR(op))
		addr = trap_registers.regs[OPCODE_JSR_REG(op)];

	/* RTS */
	else if (OPCODE_RTS(op))
		addr = trap_registers.pr;

	/* RTE */
	else if (OPCODE_RTE(op))
		addr = trap_registers.regs[15];

	/* Other */
	else
		addr = trap_registers.pc + 2;

	kgdb_flush_icache_range(addr, addr + 2);
	return (short *) addr;
}

/* Set up a single-step.  Replace the instruction immediately after the 
   current instruction (i.e. next in the expected flow of control) with a
   trap instruction, so that returning will cause only a single instruction
   to be executed. Note that this model is slightly broken for instructions
   with delay slots (e.g. B[TF]S, BSR, BRA etc), where both the branch
   and the instruction in the delay slot will be executed. */
static void do_single_step(void)
{
	unsigned short *addr = 0;

	/* Determine where the target instruction will send us to */
	addr = get_step_address();
	stepped_address = (int)addr;

	/* Replace it */
	stepped_opcode = *(short *)addr;
	*addr = STEP_OPCODE;

	/* Flush and return */
	kgdb_flush_icache_range((long) addr, (long) addr + 2);
	return;
}

/* Undo a single step */
static void undo_single_step(void)
{
	/* If we have stepped, put back the old instruction */
	/* Use stepped_address in case we stopped elsewhere */
	if (stepped_opcode != 0) {
		*(short*)stepped_address = stepped_opcode;
		kgdb_flush_icache_range(stepped_address, stepped_address + 2);
	}
	stepped_opcode = 0;
}

/* Send a signal message */
static void send_signal_msg(const int signum)
{
#ifndef CONFIG_KGDB_THREAD
	out_buffer[0] = 'S';
	out_buffer[1] = highhex(signum);
	out_buffer[2] = lowhex(signum);
	out_buffer[3] = 0;
	put_packet(out_buffer);
#else /* CONFIG_KGDB_THREAD */
	int threadid;
	threadref thref;
	char *out = out_buffer;
	const char *tstring = "thread";

	*out++ = 'T';
	*out++ = highhex(signum);
	*out++ = lowhex(signum);

	while (*tstring) {
		*out++ = *tstring++;
	}
	*out++ = ':';

	threadid = trapped_thread->pid;
	if (threadid == 0) threadid = PID_MAX;
	int_to_threadref(&thref, threadid);
	pack_threadid(out, &thref);
	out += BUF_THREAD_ID_SIZE;
	*out++ = ';';

	*out = 0;
	put_packet(out_buffer);
#endif /* CONFIG_KGDB_THREAD */
}

/* Reply that all was well */
static void send_ok_msg(void)
{
	strcpy(out_buffer, "OK");
	put_packet(out_buffer);
}

/* Reply that an error occurred */
static void send_err_msg(void)
{
	strcpy(out_buffer, "E01");
	put_packet(out_buffer);
}

/* Empty message indicates unrecognised command */
static void send_empty_msg(void)
{
	put_packet("");
}

/* Read memory due to 'm' message */
static void read_mem_msg(void)
{
	char *ptr;
	int addr;
	int length;

	/* Jmp, disable bus error handler */
	if (setjmp(rem_com_env) == 0) {

		kgdb_nofault = 1;

		/* Walk through, have m<addr>,<length> */
		ptr = &in_buffer[1];
		if (hex_to_int(&ptr, &addr) && (*ptr++ == ','))
			if (hex_to_int(&ptr, &length)) {
				ptr = 0;
				if (length * 2 > OUTBUFMAX)
					length = OUTBUFMAX / 2;
				mem_to_hex((char *) addr, out_buffer, length);
			}
		if (ptr)
			send_err_msg();
		else
			put_packet(out_buffer);
	} else
		send_err_msg();

	/* Restore bus error handler */
	kgdb_nofault = 0;
}

/* Write memory due to 'M' or 'X' message */
static void write_mem_msg(int binary)
{
	char *ptr;
	int addr;
	int length;

	if (setjmp(rem_com_env) == 0) {

		kgdb_nofault = 1;

		/* Walk through, have M<addr>,<length>:<data> */
		ptr = &in_buffer[1];
		if (hex_to_int(&ptr, &addr) && (*ptr++ == ','))
			if (hex_to_int(&ptr, &length) && (*ptr++ == ':')) {
				if (binary)
					ebin_to_mem(ptr, (char*)addr, length);
				else
					hex_to_mem(ptr, (char*)addr, length);
				kgdb_flush_icache_range(addr, addr + length);
				ptr = 0;
				send_ok_msg();
			}
		if (ptr)
			send_err_msg();
	} else
		send_err_msg();

	/* Restore bus error handler */
	kgdb_nofault = 0;
}

/* Continue message  */
static void continue_msg(void)
{
	/* Try to read optional parameter, PC unchanged if none */
	char *ptr = &in_buffer[1];
	int addr;

	if (hex_to_int(&ptr, &addr))
		trap_registers.pc = addr;
}

/* Continue message with signal */
static void continue_with_sig_msg(void)
{
	int signal;
	char *ptr = &in_buffer[1];
	int addr;

	/* Report limitation */
	kgdb_to_gdb("Cannot force signal in kgdb, continuing anyway.\n");

	/* Signal */
	hex_to_int(&ptr, &signal);
	if (*ptr == ';')
		ptr++;

	/* Optional address */
	if (hex_to_int(&ptr, &addr))
		trap_registers.pc = addr;
}

/* Step message */
static void step_msg(void)
{
	continue_msg();
	do_single_step();
}

/* Step message with signal */
static void step_with_sig_msg(void)
{
	continue_with_sig_msg();
	do_single_step();
}

/* Send register contents */
static void send_regs_msg(void)
{
#ifdef CONFIG_KGDB_THREAD
	if (!current_thread)
		kgdb_regs_to_gdb_regs(&trap_registers, registers);
	else
		thread_regs_to_gdb_regs(current_thread, registers);
#else
	kgdb_regs_to_gdb_regs(&trap_registers, registers);
#endif