// SPDX-License-Identifier: GPL-2.0
/*
* 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.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#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/irq_work.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/serial_core.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 DEFINE_MUTEX(config_mutex);
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;
static struct platform_device *kgdboc_pdev;
#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
static struct kgdb_io kgdboc_earlycon_io_ops;
static int (*earlycon_orig_exit)(struct console *con);
#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
/*
* When we leave the debug trap handler we need to reset the keyboard status
* (since the original keyboard state gets partially clobbered by kdb use of
* the keyboard).
*
* The path to deliver the reset is somewhat circuitous.
*
* To deliver the reset we register an input handler, reset the keyboard and
* then deregister the input handler. However, to get this done right, we do
* have to carefully manage the calling context because we can only register
* input handlers from task context.
*
* In particular we need to trigger the action from the debug trap handler with
* all its NMI and/or NMI-like oddities. To solve this the kgdboc trap exit code
* (the "post_exception" callback) uses irq_work_queue(), which is NMI-safe, to
* schedule a callback from a hardirq context. From there we have to defer the
* work again, this time using schedule_work(), to get a callback using the
* system workqueue, which runs in task context.
*/
#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);
/* Return 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_queue_restore_input_helper(struct irq_work *unused)
{
schedule_work(&kgdboc_restore_input_work);
}
static DEFINE_IRQ_WORK(kgdboc_restore_input_irq_work, kgdboc_queue_restore_input_helper);
static void kgdboc_restore_input(void)
{
if (likely(system_state == SYSTEM_RUNNING))
irq_work_queue(&kgdboc_restore_input_irq_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--;
}
}
irq_work_sync(&kgdboc_restore_input_irq_work);
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 */
#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
static void cleanup_earlycon(void)
{
if (kgdboc_earlycon_io_ops.cons)
kgdb_unregister_io_module(&kgdboc_earlycon_io_ops);
}
#else /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
static inline void cleanup_earlycon(void) { }
#endif /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
static void cleanup_kgdboc(void)
{
cleanup_earlycon();
if (configured != 1)
return;
if (kgdb_unregister_nmi_console())
return;
kgdboc_unregister_kbd();
kgdb_unregister_io_module(&kgdboc_io_ops);
}
static int configure_kgdboc(void)
{
struct tty_driver *p;
int tty_line = 0;
int err = -ENODEV;
char *cptr = config;
struct console *cons;
int cookie;
if (!strlen(config) || isspace(config[0])) {
err = 0;
goto noconfig;
}
kgdboc_io_ops.cons = NULL;
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;
/*
* Take console_lock to serialize device() callback with
* other console operations. For example, fg_console is
* modified under console_lock when switching vt.
*/
console_lock();
cookie = console_srcu_read_lock();
for_each_console_srcu(cons) {
int idx;
if (cons->device && cons->device(cons, &idx) == p &&
idx == tty_line) {
kgdboc_io_ops.cons = cons;
break;
}
}
console_srcu_read_unlock(cookie);
console_unlock();
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();
configured = 0;
return err;
}
static int kgdboc_probe(struct platform_device *pdev)
{
int ret = 0;
mutex_lock(&config_mutex);
if (configured != 1) {
ret = configure_kgdboc();
/* Convert "no device" to "defer" so we'll keep trying */
if (ret == -ENODEV)
ret = -EPROBE_DEFER;
}
mutex_unlock(&config_mutex);
return ret;
}
static struct platform_driver kgdboc_platform_driver = {
.probe = kgdboc_probe,
.driver = {
.name = "kgdboc",
.suppress_bind_attrs = true,
},
};
static int __init init_kgdboc(void)
{
int ret;
/*
* kgdboc is a little bit of an odd "platform_driver". It can be
* up and running long before the platform_driver object is
* created and thus doesn't actually store anything in it. There's
* only one instance of kgdb so anything is stored as global state.
* The platform_driver is only created so that we can leverage the
* kernel's mechanisms (like -EPROBE_DEFER) to call us when our
* underlying tty is ready. Here we init our platform driver and
* then create the single kgdboc instance.
*/
ret = platform_driver_register(&kgdboc_platform_driver);
if (ret)
return ret;
kgdboc_pdev = platform_device_alloc("kgdboc", PLATFORM_DEVID_NONE);
if (!kgdboc_pdev) {
ret = -ENOMEM;
goto err_did_register;
}
ret = platform_device_add(kgdboc_pdev);
if (!ret)
return 0;
platform_device_put(kgdboc_pdev);
err_did_register:
platform_driver_unregister(&kgdboc_platform_driver);
return ret;
}
static void exit_kgdboc(void)
{
mutex_lock(&config_mutex);
cleanup_kgdboc();
mutex_unlock(&config_mutex);
platform_device_unregister(kgdboc_pdev);
platform_driver_unregister(&kgdboc_platform_driver);
}
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,
const struct kernel_param *kp)
{
size_t len = strlen(kmessage);
int ret = 0;
if (len >= MAX_CONFIG_LEN) {
pr_err("config string too long\n");
return -ENOSPC;
}
if (kgdb_connected) {
pr_err("Cannot reconfigure while KGDB is connected.\n");
return -EBUSY;
}
mutex_lock(&config_mutex);
strcpy(config, kmessage);
/* Chop out \n char as a result of echo */
if (len && config[len - 1] == '\n')
config[len - 1] = '\0';
if (configured == 1)
cleanup_kgdboc();
/*
* Configure with the new params as long as init already ran.
* Note that we can get called before init if someone loads us
* with "modprobe kgdboc kgdboc=..." or if they happen to use
* the odd syntax of "kgdboc.kgdboc=..." on the kernel command.
*/
if (configured >= 0)
ret = configure_kgdboc();
/*
* If we couldn't configure then clear out the config. Note that
* specifying an invalid config on the kernel command line vs.
* through sysfs have slightly different behaviors. If we fail
* to configure what was specified on the kernel command line
* we'll leave it in the 'config' and return -EPROBE_DEFER from
* our probe. When specified through sysfs userspace is
* responsible for loading the tty driver before setting up.
*/
if (ret)
config[0] = '\0';
mutex_unlock(&config_mutex);
return ret;
}
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,
};
#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
static int kgdboc_option_setup(char *opt)
{
if (!opt) {
pr_err("config string not provided\n");
return 1;
}
if (strlen(opt) >= MAX_CONFIG_LEN) {
pr_err("config string too long\n");
return 1;
}
strcpy(config, opt);
return 1;
}
__setup("kgdboc=", kgdboc_option_setup);
/* This is only available if kgdboc is a built in for early debugging */
static int __init kgdboc_early_init(char *opt)
{
kgdboc_option_setup(opt);
configure_kgdboc();
return 0;
}
early_param("ekgdboc", kgdboc_early_init);
static int kgdboc_earlycon_get_char(void)
{
char c;
if (!kgdboc_earlycon_io_ops.cons->read(kgdboc_earlycon_io_ops.cons,
&c, 1))
return NO_POLL_CHAR;
return c;
}
static void kgdboc_earlycon_put_char(u8 chr)
{
kgdboc_earlycon_io_ops.cons->write(kgdboc_earlycon_io_ops.cons, &chr,
1);
}
static void kgdboc_earlycon_pre_exp_handler(void)
{
struct console *con;
static bool already_warned;
int cookie;
if (already_warned)
return;
/*
* When the first normal console comes up the kernel will take all
* the boot consoles out of the list. Really, we should stop using
* the boot console when it does that but until a TTY is registered
* we have no other choice so we keep using it. Since not all
* serial drivers might be OK with this, print a warning once per
* boot if we detect this case.
*/
cookie = console_srcu_read_lock();
for_each_console_srcu(con) {
if (con == kgdboc_earlycon_io_ops.cons)
break;
}
console_srcu_read_unlock(cookie);
if (con)
return;
already_warned = true;
pr_warn("kgdboc_earlycon is still using bootconsole\n");
}
static int kgdboc_earlycon_deferred_exit(struct console *con)
{
/*
* If we get here it means the boot console is going away but we
* don't yet have a suitable replacement. Don't pass through to
* the original exit routine. We'll call it later in our deinit()
* function. For now, restore the original exit() function pointer
* as a sentinal that we've hit this point.
*/
con->exit = earlycon_orig_exit;
return 0;
}
static void kgdboc_earlycon_deinit(void)
{
if (!kgdboc_earlycon_io_ops.cons)
return;
if (kgdboc_earlycon_io_ops.cons->exit == kgdboc_earlycon_deferred_exit)
/*
* kgdboc_earlycon is exiting but original boot console exit
* was never called (AKA kgdboc_earlycon_deferred_exit()
* didn't ever run). Undo our trap.
*/
kgdboc_earlycon_io_ops.cons->exit = earlycon_orig_exit;
else if (kgdboc_earlycon_io_ops.cons->exit)
/*
* We skipped calling the exit() routine so we could try to
* keep using the boot console even after it went away. We're
* finally done so call the function now.
*/
kgdboc_earlycon_io_ops.cons->exit(kgdboc_earlycon_io_ops.cons);
kgdboc_earlycon_io_ops.cons = NULL;
}
static struct kgdb_io kgdboc_earlycon_io_ops = {
.name = "kgdboc_earlycon",
.read_char = kgdboc_earlycon_get_char,
.write_char = kgdboc_earlycon_put_char,
.pre_exception = kgdboc_earlycon_pre_exp_handler,
.deinit = kgdboc_earlycon_deinit,
};
#define MAX_CONSOLE_NAME_LEN (sizeof((struct console *) 0)->name)
static char kgdboc_earlycon_param[MAX_CONSOLE_NAME_LEN] __initdata;
static bool kgdboc_earlycon_late_enable __initdata;
static int __init kgdboc_earlycon_init(char *opt)
{
struct console *con;
kdb_init(KDB_INIT_EARLY);
/*
* Look for a matching console, or if the name was left blank just
* pick the first one we find.
*/
/*
* Hold the console_list_lock to guarantee that no consoles are
* unregistered until the kgdboc_earlycon setup is complete.
* Trapping the exit() callback relies on exit() not being
* called until the trap is setup. This also allows safe
* traversal of the console list and race-free reading of @flags.
*/
console_list_lock();
for_each_console(con) {
if (con->write && con->read &&
(con->flags & (CON_BOOT | CON_ENABLED)) &&
(!opt || !opt[0] || strcmp(con->name, opt) == 0))
break;
}
if (!con) {
/*
* Both earlycon and kgdboc_earlycon are initialized during
* early parameter parsing. We cannot guarantee earlycon gets
* in first and, in any case, on ACPI systems earlycon may
* defer its own initialization (usually to somewhere within
* setup_arch() ). To cope with either of these situations
* we can defer our own initialization to a little later in
* the boot.
*/
if (!kgdboc_earlycon_late_enable) {
pr_info("No suitable earlycon yet, will try later\n");
if (opt)
strscpy(kgdboc_earlycon_param, opt,
sizeof(kgdboc_earlycon_param));
kgdboc_earlycon_late_enable = true;
} else {
pr_info("Couldn't find kgdb earlycon\n");
}
goto unlock;
}
kgdboc_earlycon_io_ops.cons = con;
pr_info("Going to register kgdb with earlycon '%s'\n", con->name);
if (kgdb_register_io_module(&kgdboc_earlycon_io_ops) != 0) {
kgdboc_earlycon_io_ops.cons = NULL;
pr_info("Failed to register kgdb with earlycon\n");
} else {
/* Trap exit so we can keep earlycon longer if needed. */
earlycon_orig_exit = con->exit;
con->exit = kgdboc_earlycon_deferred_exit;
}
unlock:
console_list_unlock();
/* Non-zero means malformed option so we always return zero */
return 0;
}
early_param("kgdboc_earlycon", kgdboc_earlycon_init);
/*
* This is only intended for the late adoption of an early console.
*
* It is not a reliable way to adopt regular consoles because we can not
* control what order console initcalls are made and, in any case, many
* regular consoles are registered much later in the boot process than
* the console initcalls!
*/
static int __init kgdboc_earlycon_late_init(void)
{
if (kgdboc_earlycon_late_enable)
kgdboc_earlycon_init(kgdboc_earlycon_param);
return 0;
}
console_initcall(kgdboc_earlycon_late_init);
#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
module_init(init_kgdboc);
module_exit(exit_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");
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