tty/serial: Add kgdb_nmi driver

	  Say Y if you have an external 8250/16C550 UART.  If unsure, say N.

config SERIAL_KGDB_NMI

	bool "Serial console over KGDB NMI debugger port"

	depends on KGDB_SERIAL_CONSOLE

	help

	  This special driver allows you to temporary use NMI debugger port

	  as a normal console (assuming that the port is attached to KGDB).

	  Unlike KDB's disable_nmi command, with this driver you are always

	  able to go back to the debugger using KGDB escape sequence ($3#33).

	  This is because this console driver processes the input in NMI

	  context, and thus is able to intercept the magic sequence.

	  Note that since the console interprets input and uses polling

	  communication methods, for things like PPP you still must fully

	  detach debugger port from the KGDB NMI (i.e. disable_nmi), and

	  use raw console.

	  If unsure, say N.

config SERIAL_KS8695

	bool "Micrel KS8695 (Centaur) serial port support"

	depends on ARCH_KS8695

obj-$(CONFIG_SERIAL_NETX) += netx-serial.o

obj-$(CONFIG_SERIAL_OF_PLATFORM) += of_serial.o

obj-$(CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL) += nwpserial.o

obj-$(CONFIG_SERIAL_KGDB_NMI) += kgdb_nmi.o

obj-$(CONFIG_SERIAL_KS8695) += serial_ks8695.o

obj-$(CONFIG_SERIAL_OMAP) += omap-serial.o

obj-$(CONFIG_SERIAL_ALTERA_UART) += altera_uart.o

/*

 * KGDB NMI serial console

 *

 * Copyright 2010 Google, Inc.

 *		  Arve Hjønnevåg <arve@android.com>

 *		  Colin Cross <ccross@android.com>

 * Copyright 2012 Linaro Ltd.

 *		  Anton Vorontsov <anton.vorontsov@linaro.org>

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 as published

 * by the Free Software Foundation.

 */

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/compiler.h>

#include <linux/init.h>

#include <linux/slab.h>

#include <linux/errno.h>

#include <linux/atomic.h>

#include <linux/console.h>

#include <linux/tty.h>

#include <linux/tty_driver.h>

#include <linux/tty_flip.h>

#include <linux/interrupt.h>

#include <linux/hrtimer.h>

#include <linux/tick.h>

#include <linux/kfifo.h>

#include <linux/kgdb.h>

#include <linux/kdb.h>

static int kgdb_nmi_knock = 1;

module_param_named(knock, kgdb_nmi_knock, int, 0600);

MODULE_PARM_DESC(knock, "if set to 1 (default), the special '$3#33' command " \

			"must be used to enter the debugger; when set to 0, " \

			"hitting return key is enough to enter the debugger; " \

			"when set to -1, the debugger is entered immediately " \

			"upon NMI");

static char *kgdb_nmi_magic = "$3#33";

module_param_named(magic, kgdb_nmi_magic, charp, 0600);

MODULE_PARM_DESC(magic, "magic sequence to enter NMI debugger (default $3#33)");

static bool kgdb_nmi_tty_enabled;

static void kgdb_nmi_console_write(struct console *co, const char *s, uint c)

{

	int i;

	if (!kgdb_nmi_tty_enabled || atomic_read(&kgdb_active) >= 0)

		return;

	for (i = 0; i < c; i++)

		dbg_io_ops->write_char(s[i]);

}

static struct tty_driver *kgdb_nmi_tty_driver;

static struct tty_driver *kgdb_nmi_console_device(struct console *co, int *idx)

{

	*idx = co->index;

	return kgdb_nmi_tty_driver;

}

static struct console kgdb_nmi_console = {

	.name	= "ttyNMI",

	.write	= kgdb_nmi_console_write,

	.device	= kgdb_nmi_console_device,

	.flags	= CON_PRINTBUFFER | CON_ANYTIME | CON_ENABLED,

	.index	= -1,

};

/*

 * This is usually the maximum rate on debug ports. We make fifo large enough

 * to make copy-pasting to the terminal usable.

 */

#define KGDB_NMI_BAUD		115200

#define KGDB_NMI_FIFO_SIZE	roundup_pow_of_two(KGDB_NMI_BAUD / 8 / HZ)

struct kgdb_nmi_tty_priv {

	struct tty_port port;

	struct tasklet_struct tlet;

	STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo;

};

static struct kgdb_nmi_tty_priv *kgdb_nmi_port_to_priv(struct tty_port *port)

{

	return container_of(port, struct kgdb_nmi_tty_priv, port);

}

/*

 * Our debugging console is polled in a tasklet, so we'll check for input

 * every tick. In HZ-less mode, we should program the next tick.  We have

 * to use the lowlevel stuff as no locks should be grabbed.

 */

#ifdef CONFIG_HIGH_RES_TIMERS

static void kgdb_tty_poke(void)

{

	tick_program_event(ktime_get(), 0);

}

#else

static inline void kgdb_tty_poke(void) {}

#endif

static struct tty_port *kgdb_nmi_port;

static void kgdb_tty_recv(int ch)

{

	struct kgdb_nmi_tty_priv *priv;

	char c = ch;

	if (!kgdb_nmi_port || ch < 0)

		return;

	/*

	 * Can't use port->tty->driver_data as tty might be not there. Tasklet

	 * will check for tty and will get the ref, but here we don't have to

	 * do that, and actually, we can't: we're in NMI context, no locks are

	 * possible.

	 */

	priv = kgdb_nmi_port_to_priv(kgdb_nmi_port);

	kfifo_in(&priv->fifo, &c, 1);

	kgdb_tty_poke();

}

static int kgdb_nmi_poll_one_knock(void)

{

	static int n;

	int c = -1;

	const char *magic = kgdb_nmi_magic;

	size_t m = strlen(magic);

	bool printch = 0;

	c = dbg_io_ops->read_char();

	if (c == NO_POLL_CHAR)

		return c;

	if (!kgdb_nmi_knock && (c == '\r' || c == '\n')) {

		return 1;

	} else if (c == magic[n]) {

		n = (n + 1) % m;

		if (!n)

			return 1;

		printch = 1;

	} else {

		n = 0;

	}

	if (kgdb_nmi_tty_enabled) {

		kgdb_tty_recv(c);

		return 0;

	}

	if (printch) {

		kdb_printf("%c", c);

		return 0;

	}

	kdb_printf("\r%s %s to enter the debugger> %*s",

		   kgdb_nmi_knock ? "Type" : "Hit",

		   kgdb_nmi_knock ? magic  : "<return>", (int)m, "");

	while (m--)

		kdb_printf("\b");

	return 0;

}

/**

 * kgdb_nmi_poll_knock - Check if it is time to enter the debugger

 *

 * "Serial ports are often noisy, especially when muxed over another port (we

 * often use serial over the headset connector). Noise on the async command

 * line just causes characters that are ignored, on a command line that blocked

 * execution noise would be catastrophic." -- Colin Cross

 *

 * So, this function implements KGDB/KDB knocking on the serial line: we won't

 * enter the debugger until we receive a known magic phrase (which is actually

 * "$3#33", known as "escape to KDB" command. There is also a relaxed variant

 * of knocking, i.e. just pressing the return key is enough to enter the

 * debugger. And if knocking is disabled, the function always returns 1.

 */

bool kgdb_nmi_poll_knock(void)

{

	if (kgdb_nmi_knock < 0)

		return 1;

	while (1) {

		int ret;

		ret = kgdb_nmi_poll_one_knock();

		if (ret == NO_POLL_CHAR)

			return 0;

		else if (ret == 1)

			break;

	}

	return 1;

}

/*

 * The tasklet is cheap, it does not cause wakeups when reschedules itself,

 * instead it waits for the next tick.

 */

static void kgdb_nmi_tty_receiver(unsigned long data)

{

	struct kgdb_nmi_tty_priv *priv = (void *)data;

	struct tty_struct *tty;

	char ch;

	tasklet_schedule(&priv->tlet);

	if (likely(!kgdb_nmi_tty_enabled || !kfifo_len(&priv->fifo)))

		return;

	/* Port is there, but tty might be hung up, check. */

	tty = tty_port_tty_get(kgdb_nmi_port);

	if (!tty)

		return;

	while (kfifo_out(&priv->fifo, &ch, 1))

		tty_insert_flip_char(priv->port.tty, ch, TTY_NORMAL);

	tty_flip_buffer_push(priv->port.tty);

	tty_kref_put(tty);

}

static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty)

{

	struct kgdb_nmi_tty_priv *priv = tty->driver_data;

	kgdb_nmi_port = port;

	tasklet_schedule(&priv->tlet);

	return 0;

}

static void kgdb_nmi_tty_shutdown(struct tty_port *port)

{

	struct kgdb_nmi_tty_priv *priv = port->tty->driver_data;

	tasklet_kill(&priv->tlet);

	kgdb_nmi_port = NULL;

}

static const struct tty_port_operations kgdb_nmi_tty_port_ops = {

	.activate	= kgdb_nmi_tty_activate,

	.shutdown	= kgdb_nmi_tty_shutdown,

};

static int kgdb_nmi_tty_install(struct tty_driver *drv, struct tty_struct *tty)

{

	struct kgdb_nmi_tty_priv *priv;

	int ret;

	priv = kzalloc(sizeof(*priv), GFP_KERNEL);

	if (!priv)

		return -ENOMEM;

	INIT_KFIFO(priv->fifo);

	tasklet_init(&priv->tlet, kgdb_nmi_tty_receiver, (unsigned long)priv);

	tty_port_init(&priv->port);

	priv->port.ops = &kgdb_nmi_tty_port_ops;

	tty->driver_data = priv;

	ret = tty_port_install(&priv->port, drv, tty);

	if (ret) {

		pr_err("%s: can't install tty port: %d\n", __func__, ret);

		goto err;

	}

	return 0;

err:

	kfree(priv);

	return ret;

}

static void kgdb_nmi_tty_cleanup(struct tty_struct *tty)

{

	struct kgdb_nmi_tty_priv *priv = tty->driver_data;

	tty->driver_data = NULL;

	kfree(priv);

}

static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file)

{

	struct kgdb_nmi_tty_priv *priv = tty->driver_data;

	return tty_port_open(&priv->port, tty, file);

}

static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file)

{

	struct kgdb_nmi_tty_priv *priv = tty->driver_data;

	tty_port_close(&priv->port, tty, file);

}

static void kgdb_nmi_tty_hangup(struct tty_struct *tty)

{

	struct kgdb_nmi_tty_priv *priv = tty->driver_data;

	tty_port_hangup(&priv->port);

}

static int kgdb_nmi_tty_write_room(struct tty_struct *tty)

{

	/* Actually, we can handle any amount as we use polled writes. */

	return 2048;

}

static int kgdb_nmi_tty_write(struct tty_struct *tty, const unchar *buf, int c)

{

	int i;

	for (i = 0; i < c; i++)

		dbg_io_ops->write_char(buf[i]);

	return c;

}

static const struct tty_operations kgdb_nmi_tty_ops = {

	.open		= kgdb_nmi_tty_open,

	.close		= kgdb_nmi_tty_close,

	.install	= kgdb_nmi_tty_install,

	.cleanup	= kgdb_nmi_tty_cleanup,

	.hangup		= kgdb_nmi_tty_hangup,

	.write_room	= kgdb_nmi_tty_write_room,

	.write		= kgdb_nmi_tty_write,

};

static int kgdb_nmi_enable_console(int argc, const char *argv[])

{

	kgdb_nmi_tty_enabled = !(argc == 1 && !strcmp(argv[1], "off"));

	return 0;

}

int kgdb_register_nmi_console(void)

{

	int ret;

	if (!arch_kgdb_ops.enable_nmi)

		return 0;

	kgdb_nmi_tty_driver = alloc_tty_driver(1);

	if (!kgdb_nmi_tty_driver) {

		pr_err("%s: cannot allocate tty\n", __func__);

		return -ENOMEM;

	}

	kgdb_nmi_tty_driver->driver_name	= "ttyNMI";

	kgdb_nmi_tty_driver->name		= "ttyNMI";

	kgdb_nmi_tty_driver->num		= 1;

	kgdb_nmi_tty_driver->type		= TTY_DRIVER_TYPE_SERIAL;

	kgdb_nmi_tty_driver->subtype		= SERIAL_TYPE_NORMAL;

	kgdb_nmi_tty_driver->flags		= TTY_DRIVER_REAL_RAW;

	kgdb_nmi_tty_driver->init_termios	= tty_std_termios;

	tty_termios_encode_baud_rate(&kgdb_nmi_tty_driver->init_termios,

				     KGDB_NMI_BAUD, KGDB_NMI_BAUD);

	tty_set_operations(kgdb_nmi_tty_driver, &kgdb_nmi_tty_ops);

	ret = tty_register_driver(kgdb_nmi_tty_driver);

	if (ret) {

		pr_err("%s: can't register tty driver: %d\n", __func__, ret);

		goto err_drv_reg;

	}

	ret = kdb_register("nmi_console", kgdb_nmi_enable_console, "[off]",

			   "switch to Linux NMI console", 0);

	if (ret) {

		pr_err("%s: can't register kdb command: %d\n", __func__, ret);

		goto err_kdb_reg;

	}

	register_console(&kgdb_nmi_console);

	arch_kgdb_ops.enable_nmi(1);

	return 0;

err_kdb_reg:

	tty_unregister_driver(kgdb_nmi_tty_driver);

err_drv_reg:

	put_tty_driver(kgdb_nmi_tty_driver);

	return ret;

}

EXPORT_SYMBOL_GPL(kgdb_register_nmi_console);

int kgdb_unregister_nmi_console(void)

{

	int ret;

	if (!arch_kgdb_ops.enable_nmi)

		return 0;

	arch_kgdb_ops.enable_nmi(0);

	kdb_unregister("nmi_console");

	ret = unregister_console(&kgdb_nmi_console);

	if (ret)

		return ret;

	ret = tty_unregister_driver(kgdb_nmi_tty_driver);

	if (ret)

		return ret;

	put_tty_driver(kgdb_nmi_tty_driver);

	return 0;

}

EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console);

static void cleanup_kgdboc(void)

{

	if (kgdb_unregister_nmi_console())

		return;

	kgdboc_unregister_kbd();

	if (configured == 1)

		kgdb_unregister_io_module(&kgdboc_io_ops);

	if (err)

		goto noconfig;

	err = kgdb_register_nmi_console();

	if (err)

		goto nmi_con_failed;

	configured = 1;

	return 0;

nmi_con_failed:

	kgdb_unregister_io_module(&kgdboc_io_ops);

noconfig:

	kgdboc_unregister_kbd();

	config[0] = 0;

	configured = 0;

	cleanup_kgdboc();

extern unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs);

#ifdef CONFIG_SERIAL_KGDB_NMI

extern int kgdb_register_nmi_console(void);

extern int kgdb_unregister_nmi_console(void);

extern bool kgdb_nmi_poll_knock(void);

#else

static inline int kgdb_register_nmi_console(void) { return 0; }

static inline int kgdb_unregister_nmi_console(void) { return 0; }

static inline bool kgdb_nmi_poll_knock(void) { return 1; }

#endif

extern int kgdb_register_io_module(struct kgdb_io *local_kgdb_io_ops);

extern void kgdb_unregister_io_module(struct kgdb_io *local_kgdb_io_ops);

extern struct kgdb_io *dbg_io_ops;