diff options
Diffstat (limited to 'drivers/tty/serial/kgdboc.c')
| -rw-r--r-- | drivers/tty/serial/kgdboc.c | 83 |
1 files changed, 64 insertions, 19 deletions
diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c index 49d0c7f2b29b..5a955c80a853 100644 --- a/drivers/tty/serial/kgdboc.c +++ b/drivers/tty/serial/kgdboc.c @@ -19,6 +19,7 @@ #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> @@ -48,6 +49,25 @@ 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, @@ -99,10 +119,17 @@ static void kgdboc_restore_input_helper(struct work_struct *dummy) 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)) - schedule_work(&kgdboc_restore_input_work); + irq_work_queue(&kgdboc_restore_input_irq_work); } static int kgdboc_register_kbd(char **cptr) @@ -133,6 +160,7 @@ static void kgdboc_unregister_kbd(void) i--; } } + irq_work_sync(&kgdboc_restore_input_irq_work); flush_work(&kgdboc_restore_input_work); } #else /* ! CONFIG_KDB_KEYBOARD */ @@ -158,8 +186,6 @@ static void cleanup_kgdboc(void) if (configured != 1) return; - if (kgdb_unregister_nmi_console()) - return; kgdboc_unregister_kbd(); kgdb_unregister_io_module(&kgdboc_io_ops); } @@ -171,6 +197,7 @@ static int configure_kgdboc(void) int err = -ENODEV; char *cptr = config; struct console *cons; + int cookie; if (!strlen(config) || isspace(config[0])) { err = 0; @@ -193,7 +220,15 @@ static int configure_kgdboc(void) if (!p) goto noconfig; - for_each_console(cons) { + /* + * 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) { @@ -201,6 +236,9 @@ static int configure_kgdboc(void) break; } } + console_srcu_read_unlock(cookie); + + console_unlock(); kgdb_tty_driver = p; kgdb_tty_line = tty_line; @@ -210,16 +248,10 @@ do_register: 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; @@ -342,7 +374,7 @@ static int param_set_kgdboc_var(const char *kmessage, /* * 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 + * with "modprobe kgdboc kgdboc=..." or if they happen to use * the odd syntax of "kgdboc.kgdboc=..." on the kernel command. */ if (configured >= 0) @@ -403,16 +435,16 @@ static int kgdboc_option_setup(char *opt) { if (!opt) { pr_err("config string not provided\n"); - return -EINVAL; + return 1; } if (strlen(opt) >= MAX_CONFIG_LEN) { pr_err("config string too long\n"); - return -ENOSPC; + return 1; } strcpy(config, opt); - return 0; + return 1; } __setup("kgdboc=", kgdboc_option_setup); @@ -449,6 +481,7 @@ static void kgdboc_earlycon_pre_exp_handler(void) { struct console *con; static bool already_warned; + int cookie; if (already_warned) return; @@ -461,9 +494,14 @@ static void kgdboc_earlycon_pre_exp_handler(void) * serial drivers might be OK with this, print a warning once per * boot if we detect this case. */ - for_each_console(con) + cookie = console_srcu_read_lock(); + for_each_console_srcu(con) { if (con == kgdboc_earlycon_io_ops.cons) - return; + break; + } + console_srcu_read_unlock(cookie); + if (con) + return; already_warned = true; pr_warn("kgdboc_earlycon is still using bootconsole\n"); @@ -528,10 +566,17 @@ static int __init kgdboc_earlycon_init(char *opt) * Look for a matching console, or if the name was left blank just * pick the first one we find. */ - console_lock(); + + /* + * 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; } @@ -570,7 +615,7 @@ static int __init kgdboc_earlycon_init(char *opt) } unlock: - console_unlock(); + console_list_unlock(); /* Non-zero means malformed option so we always return zero */ return 0; |