kgdboc.c

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/*
 * Based on the same principle as kgdboe using the NETPOLL api, this
 * driver uses a console polling api to implement a gdb serial inteface
 * which is multiplexed on a console port.
 *
 * Maintainer: Jason Wessel <[email protected]>
 *
 * 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */
#include <linux/kernel.h>
#include <linux/ctype.h>
#include <linux/kgdb.h>
#include <linux/kdb.h>
#include <linux/tty.h>
#include <linux/console.h>
#include <linux/vt_kern.h>
#include <linux/input.h>
#include <linux/module.h>

#define MAX_CONFIG_LEN      40

static struct kgdb_io       kgdboc_io_ops;

/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
static int configured       = -1;

static char config[MAX_CONFIG_LEN];
static struct kparam_string kps = {
    .string         = config,
    .maxlen         = MAX_CONFIG_LEN,
};

static int kgdboc_use_kms;  /* 1 if we use kernel mode switching */
static struct tty_driver    *kgdb_tty_driver;
static int          kgdb_tty_line;

#ifdef CONFIG_KDB_KEYBOARD
static int kgdboc_reset_connect(struct input_handler *handler,
                struct input_dev *dev,
                const struct input_device_id *id)
{
    input_reset_device(dev);

    /* Retrun an error - we do not want to bind, just to reset */
    return -ENODEV;
}

static void kgdboc_reset_disconnect(struct input_handle *handle)
{
    /* We do not expect anyone to actually bind to us */
    BUG();
}

static const struct input_device_id kgdboc_reset_ids[] = {
    {
        .flags = INPUT_DEVICE_ID_MATCH_EVBIT,
        .evbit = { BIT_MASK(EV_KEY) },
    },
    { }
};

static struct input_handler kgdboc_reset_handler = {
    .connect    = kgdboc_reset_connect,
    .disconnect = kgdboc_reset_disconnect,
    .name       = "kgdboc_reset",
    .id_table   = kgdboc_reset_ids,
};

static DEFINE_MUTEX(kgdboc_reset_mutex);

static void kgdboc_restore_input_helper(struct work_struct *dummy)
{
    /*
     * We need to take a mutex to prevent several instances of
     * this work running on different CPUs so they don't try
     * to register again already registered handler.
     */
    mutex_lock(&kgdboc_reset_mutex);

    if (input_register_handler(&kgdboc_reset_handler) == 0)
        input_unregister_handler(&kgdboc_reset_handler);

    mutex_unlock(&kgdboc_reset_mutex);
}

static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper);

static void kgdboc_restore_input(void)
{
    if (likely(system_state == SYSTEM_RUNNING))
        schedule_work(&kgdboc_restore_input_work);
}

static int kgdboc_register_kbd(char **cptr)
{
    if (strncmp(*cptr, "kbd", 3) == 0 ||
        strncmp(*cptr, "kdb", 3) == 0) {
        if (kdb_poll_idx < KDB_POLL_FUNC_MAX) {
            kdb_poll_funcs[kdb_poll_idx] = kdb_get_kbd_char;
            kdb_poll_idx++;
            if (cptr[0][3] == ',')
                *cptr += 4;
            else
                return 1;
        }
    }
    return 0;
}

static void kgdboc_unregister_kbd(void)
{
    int i;

    for (i = 0; i < kdb_poll_idx; i++) {
        if (kdb_poll_funcs[i] == kdb_get_kbd_char) {
            kdb_poll_idx--;
            kdb_poll_funcs[i] = kdb_poll_funcs[kdb_poll_idx];
            kdb_poll_funcs[kdb_poll_idx] = NULL;
            i--;
        }
    }
    flush_work(&kgdboc_restore_input_work);
}
#else /* ! CONFIG_KDB_KEYBOARD */
#define kgdboc_register_kbd(x) 0
#define kgdboc_unregister_kbd()
#define kgdboc_restore_input()
#endif /* ! CONFIG_KDB_KEYBOARD */

static int kgdboc_option_setup(char *opt)
{
    if (strlen(opt) >= MAX_CONFIG_LEN) {
        printk(KERN_ERR "kgdboc: config string too long\n");
        return -ENOSPC;
    }
    strcpy(config, opt);

    return 0;
}

__setup("kgdboc=", kgdboc_option_setup);

static void cleanup_kgdboc(void)
{
    if (kgdb_unregister_nmi_console())
        return;
    kgdboc_unregister_kbd();
    if (configured == 1)
        kgdb_unregister_io_module(&kgdboc_io_ops);
}

static int configure_kgdboc(void)
{
    struct tty_driver *p;
    int tty_line = 0;
    int err;
    char *cptr = config;
    struct console *cons;

    err = kgdboc_option_setup(config);
    if (err || !strlen(config) || isspace(config[0]))
        goto noconfig;

    err = -ENODEV;
    kgdboc_io_ops.is_console = 0;
    kgdb_tty_driver = NULL;

    kgdboc_use_kms = 0;
    if (strncmp(cptr, "kms,", 4) == 0) {
        cptr += 4;
        kgdboc_use_kms = 1;
    }

    if (kgdboc_register_kbd(&cptr))
        goto do_register;

    p = tty_find_polling_driver(cptr, &tty_line);
    if (!p)
        goto noconfig;

    cons = console_drivers;
    while (cons) {
        int idx;
        if (cons->device && cons->device(cons, &idx) == p &&
            idx == tty_line) {
            kgdboc_io_ops.is_console = 1;
            break;
        }
        cons = cons->next;
    }

    kgdb_tty_driver = p;
    kgdb_tty_line = tty_line;

do_register:
    err = kgdb_register_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();

    return err;
}

static int __init init_kgdboc(void)
{
    /* Already configured? */
    if (configured == 1)
        return 0;

    return configure_kgdboc();
}

static int kgdboc_get_char(void)
{
    if (!kgdb_tty_driver)
        return -1;
    return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,
                        kgdb_tty_line);
}

static void kgdboc_put_char(u8 chr)
{
    if (!kgdb_tty_driver)
        return;
    kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,
                    kgdb_tty_line, chr);
}

static int param_set_kgdboc_var(const char *kmessage, struct kernel_param *kp)
{
    int len = strlen(kmessage);

    if (len >= MAX_CONFIG_LEN) {
        printk(KERN_ERR "kgdboc: config string too long\n");
        return -ENOSPC;
    }

    /* Only copy in the string if the init function has not run yet */
    if (configured < 0) {
        strcpy(config, kmessage);
        return 0;
    }

    if (kgdb_connected) {
        printk(KERN_ERR
               "kgdboc: Cannot reconfigure while KGDB is connected.\n");

        return -EBUSY;
    }

    strcpy(config, kmessage);
    /* Chop out \n char as a result of echo */
    if (config[len - 1] == '\n')
        config[len - 1] = '\0';

    if (configured == 1)
        cleanup_kgdboc();

    /* Go and configure with the new params. */
    return configure_kgdboc();
}

static int dbg_restore_graphics;

static void kgdboc_pre_exp_handler(void)
{
    if (!dbg_restore_graphics && kgdboc_use_kms) {
        dbg_restore_graphics = 1;
        con_debug_enter(vc_cons[fg_console].d);
    }
    /* Increment the module count when the debugger is active */
    if (!kgdb_connected)
        try_module_get(THIS_MODULE);
}

static void kgdboc_post_exp_handler(void)
{
    /* decrement the module count when the debugger detaches */
    if (!kgdb_connected)
        module_put(THIS_MODULE);
    if (kgdboc_use_kms && dbg_restore_graphics) {
        dbg_restore_graphics = 0;
        con_debug_leave();
    }
    kgdboc_restore_input();
}

static struct kgdb_io kgdboc_io_ops = {
    .name           = "kgdboc",
    .read_char      = kgdboc_get_char,
    .write_char     = kgdboc_put_char,
    .pre_exception      = kgdboc_pre_exp_handler,
    .post_exception     = kgdboc_post_exp_handler,
};

#ifdef CONFIG_KGDB_SERIAL_CONSOLE
/* This is only available if kgdboc is a built in for early debugging */
static int __init kgdboc_early_init(char *opt)
{
    /* save the first character of the config string because the
     * init routine can destroy it.
     */
    char save_ch;

    kgdboc_option_setup(opt);
    save_ch = config[0];
    init_kgdboc();
    config[0] = save_ch;
    return 0;
}

early_param("ekgdboc", kgdboc_early_init);
#endif /* CONFIG_KGDB_SERIAL_CONSOLE */

module_init(init_kgdboc);
module_exit(cleanup_kgdboc);
module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
MODULE_DESCRIPTION("KGDB Console TTY Driver");
MODULE_LICENSE("GPL");