v4.19.13 snapshot.
diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
new file mode 100644
index 0000000..93d3a0e
--- /dev/null
+++ b/drivers/tty/serial/kgdboc.c
@@ -0,0 +1,341 @@
+// 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 <jason.wessel@windriver.com>
+ *
+ * 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.
+ */
+#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);
+
+ /* 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_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 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 = -ENODEV;
+ char *cptr = config;
+ struct console *cons;
+
+ if (!strlen(config) || isspace(config[0]))
+ goto noconfig;
+
+ 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,
+ const struct kernel_param *kp)
+{
+ size_t 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 (len && 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
+static int kgdboc_option_setup(char *opt)
+{
+ if (!opt) {
+ pr_err("config string not provided\n");
+ return -EINVAL;
+ }
+
+ if (strlen(opt) >= MAX_CONFIG_LEN) {
+ pr_err("config string too long\n");
+ return -ENOSPC;
+ }
+ strcpy(config, opt);
+
+ return 0;
+}
+
+__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)
+{
+ /* 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");