403 lines
9.8 KiB
C
403 lines
9.8 KiB
C
![]() |
/*
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* KGDB NMI serial console
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*
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* Copyright 2010 Google, Inc.
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* Arve Hjønnevåg <arve@android.com>
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* Colin Cross <ccross@android.com>
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* Copyright 2012 Linaro Ltd.
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* Anton Vorontsov <anton.vorontsov@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published
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* by the Free Software Foundation.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/compiler.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/errno.h>
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#include <linux/atomic.h>
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#include <linux/console.h>
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#include <linux/tty.h>
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#include <linux/tty_driver.h>
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#include <linux/tty_flip.h>
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#include <linux/interrupt.h>
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#include <linux/hrtimer.h>
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#include <linux/tick.h>
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#include <linux/kfifo.h>
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#include <linux/kgdb.h>
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#include <linux/kdb.h>
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static int kgdb_nmi_knock = 1;
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module_param_named(knock, kgdb_nmi_knock, int, 0600);
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MODULE_PARM_DESC(knock, "if set to 1 (default), the special '$3#33' command " \
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"must be used to enter the debugger; when set to 0, " \
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"hitting return key is enough to enter the debugger; " \
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"when set to -1, the debugger is entered immediately " \
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"upon NMI");
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static char *kgdb_nmi_magic = "$3#33";
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module_param_named(magic, kgdb_nmi_magic, charp, 0600);
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MODULE_PARM_DESC(magic, "magic sequence to enter NMI debugger (default $3#33)");
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static bool kgdb_nmi_tty_enabled;
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static void kgdb_nmi_console_write(struct console *co, const char *s, uint c)
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{
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int i;
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if (!kgdb_nmi_tty_enabled || atomic_read(&kgdb_active) >= 0)
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return;
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for (i = 0; i < c; i++)
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dbg_io_ops->write_char(s[i]);
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}
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static struct tty_driver *kgdb_nmi_tty_driver;
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static struct tty_driver *kgdb_nmi_console_device(struct console *co, int *idx)
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{
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*idx = co->index;
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return kgdb_nmi_tty_driver;
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}
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static struct console kgdb_nmi_console = {
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.name = "ttyNMI",
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.write = kgdb_nmi_console_write,
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.device = kgdb_nmi_console_device,
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.flags = CON_PRINTBUFFER | CON_ANYTIME | CON_ENABLED,
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.index = -1,
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};
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/*
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* This is usually the maximum rate on debug ports. We make fifo large enough
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* to make copy-pasting to the terminal usable.
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*/
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#define KGDB_NMI_BAUD 115200
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#define KGDB_NMI_FIFO_SIZE roundup_pow_of_two(KGDB_NMI_BAUD / 8 / HZ)
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struct kgdb_nmi_tty_priv {
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struct tty_port port;
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struct tasklet_struct tlet;
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STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo;
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};
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static struct kgdb_nmi_tty_priv *kgdb_nmi_port_to_priv(struct tty_port *port)
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{
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return container_of(port, struct kgdb_nmi_tty_priv, port);
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}
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/*
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* Our debugging console is polled in a tasklet, so we'll check for input
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* every tick. In HZ-less mode, we should program the next tick. We have
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* to use the lowlevel stuff as no locks should be grabbed.
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*/
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#ifdef CONFIG_HIGH_RES_TIMERS
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static void kgdb_tty_poke(void)
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{
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tick_program_event(ktime_get(), 0);
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}
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#else
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static inline void kgdb_tty_poke(void) {}
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#endif
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static struct tty_port *kgdb_nmi_port;
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static void kgdb_tty_recv(int ch)
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{
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struct kgdb_nmi_tty_priv *priv;
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char c = ch;
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if (!kgdb_nmi_port || ch < 0)
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return;
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/*
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* Can't use port->tty->driver_data as tty might be not there. Tasklet
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* will check for tty and will get the ref, but here we don't have to
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* do that, and actually, we can't: we're in NMI context, no locks are
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* possible.
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*/
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priv = kgdb_nmi_port_to_priv(kgdb_nmi_port);
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kfifo_in(&priv->fifo, &c, 1);
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kgdb_tty_poke();
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}
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static int kgdb_nmi_poll_one_knock(void)
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{
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static int n;
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int c = -1;
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const char *magic = kgdb_nmi_magic;
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size_t m = strlen(magic);
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bool printch = 0;
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c = dbg_io_ops->read_char();
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if (c == NO_POLL_CHAR)
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return c;
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if (!kgdb_nmi_knock && (c == '\r' || c == '\n')) {
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return 1;
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} else if (c == magic[n]) {
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n = (n + 1) % m;
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if (!n)
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return 1;
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printch = 1;
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} else {
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n = 0;
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}
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if (kgdb_nmi_tty_enabled) {
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kgdb_tty_recv(c);
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return 0;
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}
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if (printch) {
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kdb_printf("%c", c);
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return 0;
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}
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kdb_printf("\r%s %s to enter the debugger> %*s",
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kgdb_nmi_knock ? "Type" : "Hit",
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kgdb_nmi_knock ? magic : "<return>", (int)m, "");
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while (m--)
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kdb_printf("\b");
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return 0;
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}
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/**
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* kgdb_nmi_poll_knock - Check if it is time to enter the debugger
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*
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* "Serial ports are often noisy, especially when muxed over another port (we
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* often use serial over the headset connector). Noise on the async command
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* line just causes characters that are ignored, on a command line that blocked
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* execution noise would be catastrophic." -- Colin Cross
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*
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* So, this function implements KGDB/KDB knocking on the serial line: we won't
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* enter the debugger until we receive a known magic phrase (which is actually
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* "$3#33", known as "escape to KDB" command. There is also a relaxed variant
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* of knocking, i.e. just pressing the return key is enough to enter the
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* debugger. And if knocking is disabled, the function always returns 1.
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*/
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bool kgdb_nmi_poll_knock(void)
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{
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if (kgdb_nmi_knock < 0)
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return 1;
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while (1) {
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int ret;
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ret = kgdb_nmi_poll_one_knock();
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if (ret == NO_POLL_CHAR)
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return 0;
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else if (ret == 1)
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break;
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}
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return 1;
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}
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/*
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* The tasklet is cheap, it does not cause wakeups when reschedules itself,
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* instead it waits for the next tick.
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*/
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static void kgdb_nmi_tty_receiver(unsigned long data)
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{
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struct kgdb_nmi_tty_priv *priv = (void *)data;
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struct tty_struct *tty;
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char ch;
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tasklet_schedule(&priv->tlet);
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if (likely(!kgdb_nmi_tty_enabled || !kfifo_len(&priv->fifo)))
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return;
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/* Port is there, but tty might be hung up, check. */
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tty = tty_port_tty_get(kgdb_nmi_port);
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if (!tty)
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return;
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while (kfifo_out(&priv->fifo, &ch, 1))
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tty_insert_flip_char(priv->port.tty, ch, TTY_NORMAL);
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tty_flip_buffer_push(priv->port.tty);
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tty_kref_put(tty);
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}
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static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty)
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{
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struct kgdb_nmi_tty_priv *priv = tty->driver_data;
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kgdb_nmi_port = port;
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tasklet_schedule(&priv->tlet);
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return 0;
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}
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static void kgdb_nmi_tty_shutdown(struct tty_port *port)
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{
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struct kgdb_nmi_tty_priv *priv = port->tty->driver_data;
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tasklet_kill(&priv->tlet);
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kgdb_nmi_port = NULL;
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}
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static const struct tty_port_operations kgdb_nmi_tty_port_ops = {
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.activate = kgdb_nmi_tty_activate,
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.shutdown = kgdb_nmi_tty_shutdown,
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};
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static int kgdb_nmi_tty_install(struct tty_driver *drv, struct tty_struct *tty)
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{
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struct kgdb_nmi_tty_priv *priv;
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int ret;
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priv = kzalloc(sizeof(*priv), GFP_KERNEL);
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if (!priv)
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return -ENOMEM;
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INIT_KFIFO(priv->fifo);
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tasklet_init(&priv->tlet, kgdb_nmi_tty_receiver, (unsigned long)priv);
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tty_port_init(&priv->port);
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priv->port.ops = &kgdb_nmi_tty_port_ops;
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tty->driver_data = priv;
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ret = tty_port_install(&priv->port, drv, tty);
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if (ret) {
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pr_err("%s: can't install tty port: %d\n", __func__, ret);
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goto err;
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}
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return 0;
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err:
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kfree(priv);
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return ret;
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}
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static void kgdb_nmi_tty_cleanup(struct tty_struct *tty)
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{
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struct kgdb_nmi_tty_priv *priv = tty->driver_data;
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tty->driver_data = NULL;
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kfree(priv);
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}
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static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file)
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{
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struct kgdb_nmi_tty_priv *priv = tty->driver_data;
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return tty_port_open(&priv->port, tty, file);
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}
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static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file)
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{
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struct kgdb_nmi_tty_priv *priv = tty->driver_data;
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tty_port_close(&priv->port, tty, file);
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}
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static void kgdb_nmi_tty_hangup(struct tty_struct *tty)
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{
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struct kgdb_nmi_tty_priv *priv = tty->driver_data;
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tty_port_hangup(&priv->port);
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}
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static int kgdb_nmi_tty_write_room(struct tty_struct *tty)
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{
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/* Actually, we can handle any amount as we use polled writes. */
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return 2048;
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}
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static int kgdb_nmi_tty_write(struct tty_struct *tty, const unchar *buf, int c)
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{
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int i;
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for (i = 0; i < c; i++)
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dbg_io_ops->write_char(buf[i]);
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return c;
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}
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static const struct tty_operations kgdb_nmi_tty_ops = {
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.open = kgdb_nmi_tty_open,
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.close = kgdb_nmi_tty_close,
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.install = kgdb_nmi_tty_install,
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.cleanup = kgdb_nmi_tty_cleanup,
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.hangup = kgdb_nmi_tty_hangup,
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.write_room = kgdb_nmi_tty_write_room,
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.write = kgdb_nmi_tty_write,
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};
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static int kgdb_nmi_enable_console(int argc, const char *argv[])
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{
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kgdb_nmi_tty_enabled = !(argc == 1 && !strcmp(argv[1], "off"));
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return 0;
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}
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int kgdb_register_nmi_console(void)
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{
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int ret;
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if (!arch_kgdb_ops.enable_nmi)
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return 0;
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kgdb_nmi_tty_driver = alloc_tty_driver(1);
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if (!kgdb_nmi_tty_driver) {
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pr_err("%s: cannot allocate tty\n", __func__);
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return -ENOMEM;
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}
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kgdb_nmi_tty_driver->driver_name = "ttyNMI";
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kgdb_nmi_tty_driver->name = "ttyNMI";
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kgdb_nmi_tty_driver->num = 1;
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kgdb_nmi_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
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kgdb_nmi_tty_driver->subtype = SERIAL_TYPE_NORMAL;
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kgdb_nmi_tty_driver->flags = TTY_DRIVER_REAL_RAW;
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kgdb_nmi_tty_driver->init_termios = tty_std_termios;
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tty_termios_encode_baud_rate(&kgdb_nmi_tty_driver->init_termios,
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KGDB_NMI_BAUD, KGDB_NMI_BAUD);
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tty_set_operations(kgdb_nmi_tty_driver, &kgdb_nmi_tty_ops);
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ret = tty_register_driver(kgdb_nmi_tty_driver);
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if (ret) {
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pr_err("%s: can't register tty driver: %d\n", __func__, ret);
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goto err_drv_reg;
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}
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ret = kdb_register("nmi_console", kgdb_nmi_enable_console, "[off]",
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"switch to Linux NMI console", 0);
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if (ret) {
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pr_err("%s: can't register kdb command: %d\n", __func__, ret);
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goto err_kdb_reg;
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}
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register_console(&kgdb_nmi_console);
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arch_kgdb_ops.enable_nmi(1);
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return 0;
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err_kdb_reg:
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tty_unregister_driver(kgdb_nmi_tty_driver);
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err_drv_reg:
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put_tty_driver(kgdb_nmi_tty_driver);
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return ret;
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}
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EXPORT_SYMBOL_GPL(kgdb_register_nmi_console);
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int kgdb_unregister_nmi_console(void)
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{
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int ret;
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if (!arch_kgdb_ops.enable_nmi)
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return 0;
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arch_kgdb_ops.enable_nmi(0);
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kdb_unregister("nmi_console");
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ret = unregister_console(&kgdb_nmi_console);
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if (ret)
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return ret;
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ret = tty_unregister_driver(kgdb_nmi_tty_driver);
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if (ret)
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return ret;
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put_tty_driver(kgdb_nmi_tty_driver);
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return 0;
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}
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EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console);
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