kgdb.c

Kernel code of linux kernel

	}
	if (!kgdb_hex2long(&ptr, &addr)) {
		error_packet(remcom_out_buffer, -EINVAL);
		return;
	}
	if (*(ptr++) != ',' ||
		!kgdb_hex2long(&ptr, &length)) {
		error_packet(remcom_out_buffer, -EINVAL);
		return;
	}

	if (remcom_in_buffer[0] == 'Z' && *bpt_type == '0')
		error = kgdb_set_sw_break(addr);
	else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
		error = kgdb_remove_sw_break(addr);
	else if (remcom_in_buffer[0] == 'Z')
		error = arch_kgdb_ops.set_hw_breakpoint(addr,
			(int)length, *bpt_type - '0');
	else if (remcom_in_buffer[0] == 'z')
		error = arch_kgdb_ops.remove_hw_breakpoint(addr,
			(int) length, *bpt_type - '0');

	if (error == 0)
		strcpy(remcom_out_buffer, "OK");
	else
		error_packet(remcom_out_buffer, error);
}

/* Handle the 'C' signal / exception passing packets */
static int gdb_cmd_exception_pass(struct kgdb_state *ks)
{
	/* C09 == pass exception
	 * C15 == detach kgdb, pass exception
	 */
	if (remcom_in_buffer[1] == '0' && remcom_in_buffer[2] == '9') {

		ks->pass_exception = 1;
		remcom_in_buffer[0] = 'c';

	} else if (remcom_in_buffer[1] == '1' && remcom_in_buffer[2] == '5') {

		ks->pass_exception = 1;
		remcom_in_buffer[0] = 'D';
		remove_all_break();
		kgdb_connected = 0;
		return 1;

	} else {
		error_packet(remcom_out_buffer, -EINVAL);
		return 0;
	}

	/* Indicate fall through */
	return -1;
}

/*
 * This function performs all gdbserial command procesing
 */
static int gdb_serial_stub(struct kgdb_state *ks)
{
	int error = 0;
	int tmp;

	/* Clear the out buffer. */
	memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));

	if (kgdb_connected) {
		unsigned char thref[8];
		char *ptr;

		/* Reply to host that an exception has occurred */
		ptr = remcom_out_buffer;
		*ptr++ = 'T';
		ptr = pack_hex_byte(ptr, ks->signo);
		ptr += strlen(strcpy(ptr, "thread:"));
		int_to_threadref(thref, shadow_pid(current->pid));
		ptr = pack_threadid(ptr, thref);
		*ptr++ = ';';
		put_packet(remcom_out_buffer);
	}

	kgdb_usethread = kgdb_info[ks->cpu].task;
	ks->kgdb_usethreadid = shadow_pid(kgdb_info[ks->cpu].task->pid);
	ks->pass_exception = 0;

	while (1) {
		error = 0;

		/* Clear the out buffer. */
		memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));

		get_packet(remcom_in_buffer);

		switch (remcom_in_buffer[0]) {
		case '?': /* gdbserial status */
			gdb_cmd_status(ks);
			break;
		case 'g': /* return the value of the CPU registers */
			gdb_cmd_getregs(ks);
			break;
		case 'G': /* set the value of the CPU registers - return OK */
			gdb_cmd_setregs(ks);
			break;
		case 'm': /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
			gdb_cmd_memread(ks);
			break;
		case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA..AA */
			gdb_cmd_memwrite(ks);
			break;
		case 'X': /* XAA..AA,LLLL: Write LLLL bytes at address AA..AA */
			gdb_cmd_binwrite(ks);
			break;
			/* kill or detach. KGDB should treat this like a
			 * continue.
			 */
		case 'D': /* Debugger detach */
		case 'k': /* Debugger detach via kill */
			gdb_cmd_detachkill(ks);
			goto default_handle;
		case 'R': /* Reboot */
			if (gdb_cmd_reboot(ks))
				goto default_handle;
			break;
		case 'q': /* query command */
			gdb_cmd_query(ks);
			break;
		case 'H': /* task related */
			gdb_cmd_task(ks);
			break;
		case 'T': /* Query thread status */
			gdb_cmd_thread(ks);
			break;
		case 'z': /* Break point remove */
		case 'Z': /* Break point set */
			gdb_cmd_break(ks);
			break;
		case 'C': /* Exception passing */
			tmp = gdb_cmd_exception_pass(ks);
			if (tmp > 0)
				goto default_handle;
			if (tmp == 0)
				break;
			/* Fall through on tmp < 0 */
		case 'c': /* Continue packet */
		case 's': /* Single step packet */
			if (kgdb_contthread && kgdb_contthread != current) {
				/* Can't switch threads in kgdb */
				error_packet(remcom_out_buffer, -EINVAL);
				break;
			}
			kgdb_activate_sw_breakpoints();
			/* Fall through to default processing */
		default:
default_handle:
			error = kgdb_arch_handle_exception(ks->ex_vector,
						ks->signo,
						ks->err_code,
						remcom_in_buffer,
						remcom_out_buffer,
						ks->linux_regs);
			/*
			 * Leave cmd processing on error, detach,
			 * kill, continue, or single step.
			 */
			if (error >= 0 || remcom_in_buffer[0] == 'D' ||
			    remcom_in_buffer[0] == 'k') {
				error = 0;
				goto kgdb_exit;
			}

		}

		/* reply to the request */
		put_packet(remcom_out_buffer);
	}

kgdb_exit:
	if (ks->pass_exception)
		error = 1;
	return error;
}

static int kgdb_reenter_check(struct kgdb_state *ks)
{
	unsigned long addr;

	if (atomic_read(&kgdb_active) != raw_smp_processor_id())
		return 0;

	/* Panic on recursive debugger calls: */
	exception_level++;
	addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
	kgdb_deactivate_sw_breakpoints();

	/*
	 * If the break point removed ok at the place exception
	 * occurred, try to recover and print a warning to the end
	 * user because the user planted a breakpoint in a place that
	 * KGDB needs in order to function.
	 */
	if (kgdb_remove_sw_break(addr) == 0) {
		exception_level = 0;
		kgdb_skipexception(ks->ex_vector, ks->linux_regs);
		kgdb_activate_sw_breakpoints();
		printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
			addr);
		WARN_ON_ONCE(1);

		return 1;
	}
	remove_all_break();
	kgdb_skipexception(ks->ex_vector, ks->linux_regs);

	if (exception_level > 1) {
		dump_stack();
		panic("Recursive entry to debugger");
	}

	printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
	dump_stack();
	panic("Recursive entry to debugger");

	return 1;
}

/*
 * kgdb_handle_exception() - main entry point from a kernel exception
 *
 * Locking hierarchy:
 *	interface locks, if any (begin_session)
 *	kgdb lock (kgdb_active)
 */
int
kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
{
	struct kgdb_state kgdb_var;
	struct kgdb_state *ks = &kgdb_var;
	unsigned long flags;
	int error = 0;
	int i, cpu;

	ks->cpu			= raw_smp_processor_id();
	ks->ex_vector		= evector;
	ks->signo		= signo;
	ks->ex_vector		= evector;
	ks->err_code		= ecode;
	ks->kgdb_usethreadid	= 0;
	ks->linux_regs		= regs;

	if (kgdb_reenter_check(ks))
		return 0; /* Ouch, double exception ! */

acquirelock:
	/*
	 * Interrupts will be restored by the 'trap return' code, except when
	 * single stepping.
	 */
	local_irq_save(flags);

	cpu = raw_smp_processor_id();

	/*
	 * Acquire the kgdb_active lock:
	 */
	while (atomic_cmpxchg(&kgdb_active, -1, cpu) != -1)
		cpu_relax();

	/*
	 * Do not start the debugger connection on this CPU if the last
	 * instance of the exception handler wanted to come into the
	 * debugger on a different CPU via a single step
	 */
	if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
	    atomic_read(&kgdb_cpu_doing_single_step) != cpu) {

		atomic_set(&kgdb_active, -1);
		touch_softlockup_watchdog();
		clocksource_touch_watchdog();
		local_irq_restore(flags);

		goto acquirelock;
	}

	if (!kgdb_io_ready(1)) {
		error = 1;
		goto kgdb_restore; /* No I/O connection, so resume the system */
	}

	/*
	 * Don't enter if we have hit a removed breakpoint.
	 */
	if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
		goto kgdb_restore;

	/* Call the I/O driver's pre_exception routine */
	if (kgdb_io_ops->pre_exception)
		kgdb_io_ops->pre_exception();

	kgdb_info[ks->cpu].debuggerinfo = ks->linux_regs;
	kgdb_info[ks->cpu].task = current;

	kgdb_disable_hw_debug(ks->linux_regs);

	/*
	 * Get the passive CPU lock which will hold all the non-primary
	 * CPU in a spin state while the debugger is active
	 */
	if (!kgdb_single_step) {
		for (i = 0; i < NR_CPUS; i++)
			atomic_set(&passive_cpu_wait[i], 1);
	}

	/*
	 * spin_lock code is good enough as a barrier so we don't
	 * need one here:
	 */
	atomic_set(&cpu_in_kgdb[ks->cpu], 1);

#ifdef CONFIG_SMP
	/* Signal the other CPUs to enter kgdb_wait() */
	if ((!kgdb_single_step) && kgdb_do_roundup)
		kgdb_roundup_cpus(flags);
#endif

	/*
	 * Wait for the other CPUs to be notified and be waiting for us:
	 */
	for_each_online_cpu(i) {
		while (!atomic_read(&cpu_in_kgdb[i]))
			cpu_relax();
	}

	/*
	 * At this point the primary processor is completely
	 * in the debugger and all secondary CPUs are quiescent
	 */
	kgdb_post_primary_code(ks->linux_regs, ks->ex_vector, ks->err_code);
	kgdb_deactivate_sw_breakpoints();
	kgdb_single_step = 0;
	kgdb_contthread = current;
	exception_level = 0;

	/* Talk to debugger with gdbserial protocol */
	error = gdb_serial_stub(ks);

	/* Call the I/O driver's post_exception routine */
	if (kgdb_io_ops->post_exception)
		kgdb_io_ops->post_exception();

	kgdb_info[ks->cpu].debuggerinfo = NULL;
	kgdb_info[ks->cpu].task = NULL;
	atomic_set(&cpu_in_kgdb[ks->cpu], 0);

	if (!kgdb_single_step) {
		for (i = NR_CPUS-1; i >= 0; i--)
			atomic_set(&passive_cpu_wait[i], 0);
		/*
		 * Wait till all the CPUs have quit
		 * from the debugger.
		 */
		for_each_online_cpu(i) {
			while (atomic_read(&cpu_in_kgdb[i]))
				cpu_relax();
		}
	}

kgdb_restore:
	/* Free kgdb_active */
	atomic_set(&kgdb_active, -1);
	touch_softlockup_watchdog();
	clocksource_touch_watchdog();
	local_irq_restore(flags);

	return error;
}

int kgdb_nmicallback(int cpu, void *regs)
{
#ifdef CONFIG_SMP
	if (!atomic_read(&cpu_in_kgdb[cpu]) &&
			atomic_read(&kgdb_active) != cpu &&
			atomic_read(&cpu_in_kgdb[atomic_read(&kgdb_active)])) {
		kgdb_wait((struct pt_regs *)regs);
		return 0;
	}
#endif
	return 1;
}

static void kgdb_console_write(struct console *co, const char *s,
   unsigned count)
{
	unsigned long flags;

	/* If we're debugging, or KGDB has not connected, don't try
	 * and print. */
	if (!kgdb_connected || atomic_read(&kgdb_active) != -1)
		return;

	local_irq_save(flags);
	kgdb_msg_write(s, count);
	local_irq_restore(flags);
}

static struct console kgdbcons = {
	.name		= "kgdb",
	.write		= kgdb_console_write,
	.flags		= CON_PRINTBUFFER | CON_ENABLED,
	.index		= -1,
};

#ifdef CONFIG_MAGIC_SYSRQ
static void sysrq_handle_gdb(int key, struct tty_struct *tty)
{
	if (!kgdb_io_ops) {
		printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
		return;
	}
	if (!kgdb_connected)
		printk(KERN_CRIT "Entering KGDB\n");

	kgdb_breakpoint();
}

static struct sysrq_key_op sysrq_gdb_op = {
	.handler	= sysrq_handle_gdb,
	.help_msg	= "Gdb",
	.action_msg	= "GDB",
};
#endif

static void kgdb_register_callbacks(void)
{
	if (!kgdb_io_module_registered) {
		kgdb_io_module_registered = 1;
		kgdb_arch_init();
#ifdef CONFIG_MAGIC_SYSRQ
		register_sysrq_key('g', &sysrq_gdb_op);
#endif
		if (kgdb_use_con && !kgdb_con_registered) {
			register_console(&kgdbcons);
			kgdb_con_registered = 1;
		}
	}
}

static void kgdb_unregister_callbacks(void)
{
	/*
	 * When this routine is called KGDB should unregister from the
	 * panic handler and clean up, making sure it is not handling any
	 * break exceptions at the time.
	 */
	if (kgdb_io_module_registered) {
		kgdb_io_module_registered = 0;
		kgdb_arch_exit();
#ifdef CONFIG_MAGIC_SYSRQ
		unregister_sysrq_key('g', &sysrq_gdb_op);
#endif
		if (kgdb_con_registered) {
			unregister_console(&kgdbcons);
			kgdb_con_registered = 0;
		}
	}
}

static void kgdb_initial_breakpoint(void)
{
	kgdb_break_asap = 0;

	printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
	kgdb_breakpoint();
}

/**
 *	kgdb_register_io_module - register KGDB IO module
 *	@new_kgdb_io_ops: the io ops vector
 *
 *	Register it with the KGDB core.
 */
int kgdb_register_io_module(struct kgdb_io *new_kgdb_io_ops)
{
	int err;

	spin_lock(&kgdb_registration_lock);

	if (kgdb_io_ops) {
		spin_unlock(&kgdb_registration_lock);

		printk(KERN_ERR "kgdb: Another I/O driver is already "
				"registered with KGDB.\n");
		return -EBUSY;
	}

	if (new_kgdb_io_ops->init) {
		err = new_kgdb_io_ops->init();
		if (err) {
			spin_unlock(&kgdb_registration_lock);
			return err;
		}
	}

	kgdb_io_ops = new_kgdb_io_ops;

	spin_unlock(&kgdb_registration_lock);

	printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
	       new_kgdb_io_ops->name);

	/* Arm KGDB now. */
	kgdb_register_callbacks();

	if (kgdb_break_asap)
		kgdb_initial_breakpoint();

	return 0;
}
EXPORT_SYMBOL_GPL(kgdb_register_io_module);

/**
 *	kkgdb_unregister_io_module - unregister KGDB IO module
 *	@old_kgdb_io_ops: the io ops vector
 *
 *	Unregister it with the KGDB core.
 */
void kgdb_unregister_io_module(struct kgdb_io *old_kgdb_io_ops)
{
	BUG_ON(kgdb_connected);

	/*
	 * KGDB is no longer able to communicate out, so
	 * unregister our callbacks and reset state.
	 */
	kgdb_unregister_callbacks();

	spin_lock(&kgdb_registration_lock);

	WARN_ON_ONCE(kgdb_io_ops != old_kgdb_io_ops);
	kgdb_io_ops = NULL;

	spin_unlock(&kgdb_registration_lock);

	printk(KERN_INFO
		"kgdb: Unregistered I/O driver %s, debugger disabled.\n",
		old_kgdb_io_ops->name);
}
EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);

/**
 * kgdb_breakpoint - generate breakpoint exception
 *
 * 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 kgdb_breakpoint(void)
{
	atomic_set(&kgdb_setting_breakpoint, 1);
	wmb(); /* Sync point before breakpoint */
	arch_kgdb_breakpoint();
	wmb(); /* Sync point after breakpoint */
	atomic_set(&kgdb_setting_breakpoint, 0);
}
EXPORT_SYMBOL_GPL(kgdb_breakpoint);

static int __init opt_kgdb_wait(char *str)
{
	kgdb_break_asap = 1;

	if (kgdb_io_module_registered)
		kgdb_initial_breakpoint();

	return 0;
}

early_param("kgdbwait", opt_kgdb_wait);