b2aba15ad6
Currently, when kdb is compiled with keyboard support, then we will use schedule_work() to provoke reset of the keyboard status. Unfortunately schedule_work() gets called from the kgdboc post-debug-exception handler. That risks deadlock since schedule_work() is not NMI-safe and, even on platforms where the NMI is not directly used for debugging, the debug trap can have NMI-like behaviour depending on where breakpoints are placed. Fix this by using the irq work system, which is NMI-safe, to defer the call to schedule_work() to a point when it is safe to call. Reported-by: Liuye <liu.yeC@h3c.com> Closes: https://lore.kernel.org/all/20240228025602.3087748-1-liu.yeC@h3c.com/ Cc: stable@vger.kernel.org Reviewed-by: Douglas Anderson <dianders@chromium.org> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Link: https://lore.kernel.org/r/20240424-kgdboc_fix_schedule_work-v2-1-50f5a490aec5@linaro.org Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
659 lines
17 KiB
C
659 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Based on the same principle as kgdboe using the NETPOLL api, this
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* driver uses a console polling api to implement a gdb serial inteface
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* which is multiplexed on a console port.
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*
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* Maintainer: Jason Wessel <jason.wessel@windriver.com>
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*
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* 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/kernel.h>
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#include <linux/ctype.h>
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#include <linux/kgdb.h>
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#include <linux/kdb.h>
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#include <linux/tty.h>
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#include <linux/console.h>
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#include <linux/vt_kern.h>
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#include <linux/input.h>
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#include <linux/irq_work.h>
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#include <linux/module.h>
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#include <linux/platform_device.h>
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#include <linux/serial_core.h>
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#define MAX_CONFIG_LEN 40
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static struct kgdb_io kgdboc_io_ops;
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/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
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static int configured = -1;
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static DEFINE_MUTEX(config_mutex);
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static char config[MAX_CONFIG_LEN];
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static struct kparam_string kps = {
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.string = config,
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.maxlen = MAX_CONFIG_LEN,
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};
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static int kgdboc_use_kms; /* 1 if we use kernel mode switching */
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static struct tty_driver *kgdb_tty_driver;
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static int kgdb_tty_line;
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static struct platform_device *kgdboc_pdev;
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#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
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static struct kgdb_io kgdboc_earlycon_io_ops;
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static int (*earlycon_orig_exit)(struct console *con);
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#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
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/*
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* When we leave the debug trap handler we need to reset the keyboard status
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* (since the original keyboard state gets partially clobbered by kdb use of
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* the keyboard).
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*
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* The path to deliver the reset is somewhat circuitous.
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*
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* To deliver the reset we register an input handler, reset the keyboard and
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* then deregister the input handler. However, to get this done right, we do
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* have to carefully manage the calling context because we can only register
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* input handlers from task context.
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*
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* In particular we need to trigger the action from the debug trap handler with
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* all its NMI and/or NMI-like oddities. To solve this the kgdboc trap exit code
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* (the "post_exception" callback) uses irq_work_queue(), which is NMI-safe, to
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* schedule a callback from a hardirq context. From there we have to defer the
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* work again, this time using schedule_work(), to get a callback using the
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* system workqueue, which runs in task context.
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*/
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#ifdef CONFIG_KDB_KEYBOARD
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static int kgdboc_reset_connect(struct input_handler *handler,
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struct input_dev *dev,
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const struct input_device_id *id)
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{
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input_reset_device(dev);
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/* Return an error - we do not want to bind, just to reset */
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return -ENODEV;
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}
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static void kgdboc_reset_disconnect(struct input_handle *handle)
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{
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/* We do not expect anyone to actually bind to us */
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BUG();
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}
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static const struct input_device_id kgdboc_reset_ids[] = {
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{
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.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
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.evbit = { BIT_MASK(EV_KEY) },
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},
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{ }
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};
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static struct input_handler kgdboc_reset_handler = {
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.connect = kgdboc_reset_connect,
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.disconnect = kgdboc_reset_disconnect,
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.name = "kgdboc_reset",
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.id_table = kgdboc_reset_ids,
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};
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static DEFINE_MUTEX(kgdboc_reset_mutex);
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static void kgdboc_restore_input_helper(struct work_struct *dummy)
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{
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/*
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* We need to take a mutex to prevent several instances of
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* this work running on different CPUs so they don't try
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* to register again already registered handler.
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*/
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mutex_lock(&kgdboc_reset_mutex);
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if (input_register_handler(&kgdboc_reset_handler) == 0)
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input_unregister_handler(&kgdboc_reset_handler);
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mutex_unlock(&kgdboc_reset_mutex);
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}
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static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper);
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static void kgdboc_queue_restore_input_helper(struct irq_work *unused)
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{
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schedule_work(&kgdboc_restore_input_work);
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}
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static DEFINE_IRQ_WORK(kgdboc_restore_input_irq_work, kgdboc_queue_restore_input_helper);
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static void kgdboc_restore_input(void)
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{
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if (likely(system_state == SYSTEM_RUNNING))
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irq_work_queue(&kgdboc_restore_input_irq_work);
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}
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static int kgdboc_register_kbd(char **cptr)
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{
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if (strncmp(*cptr, "kbd", 3) == 0 ||
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strncmp(*cptr, "kdb", 3) == 0) {
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if (kdb_poll_idx < KDB_POLL_FUNC_MAX) {
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kdb_poll_funcs[kdb_poll_idx] = kdb_get_kbd_char;
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kdb_poll_idx++;
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if (cptr[0][3] == ',')
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*cptr += 4;
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else
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return 1;
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}
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}
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return 0;
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}
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static void kgdboc_unregister_kbd(void)
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{
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int i;
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for (i = 0; i < kdb_poll_idx; i++) {
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if (kdb_poll_funcs[i] == kdb_get_kbd_char) {
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kdb_poll_idx--;
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kdb_poll_funcs[i] = kdb_poll_funcs[kdb_poll_idx];
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kdb_poll_funcs[kdb_poll_idx] = NULL;
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i--;
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}
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}
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irq_work_sync(&kgdboc_restore_input_irq_work);
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flush_work(&kgdboc_restore_input_work);
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}
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#else /* ! CONFIG_KDB_KEYBOARD */
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#define kgdboc_register_kbd(x) 0
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#define kgdboc_unregister_kbd()
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#define kgdboc_restore_input()
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#endif /* ! CONFIG_KDB_KEYBOARD */
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#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
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static void cleanup_earlycon(void)
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{
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if (kgdboc_earlycon_io_ops.cons)
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kgdb_unregister_io_module(&kgdboc_earlycon_io_ops);
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}
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#else /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
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static inline void cleanup_earlycon(void) { }
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#endif /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
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static void cleanup_kgdboc(void)
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{
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cleanup_earlycon();
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if (configured != 1)
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return;
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if (kgdb_unregister_nmi_console())
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return;
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kgdboc_unregister_kbd();
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kgdb_unregister_io_module(&kgdboc_io_ops);
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}
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static int configure_kgdboc(void)
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{
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struct tty_driver *p;
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int tty_line = 0;
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int err = -ENODEV;
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char *cptr = config;
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struct console *cons;
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int cookie;
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if (!strlen(config) || isspace(config[0])) {
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err = 0;
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goto noconfig;
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}
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kgdboc_io_ops.cons = NULL;
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kgdb_tty_driver = NULL;
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kgdboc_use_kms = 0;
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if (strncmp(cptr, "kms,", 4) == 0) {
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cptr += 4;
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kgdboc_use_kms = 1;
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}
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if (kgdboc_register_kbd(&cptr))
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goto do_register;
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p = tty_find_polling_driver(cptr, &tty_line);
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if (!p)
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goto noconfig;
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/*
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* Take console_lock to serialize device() callback with
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* other console operations. For example, fg_console is
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* modified under console_lock when switching vt.
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*/
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console_lock();
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cookie = console_srcu_read_lock();
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for_each_console_srcu(cons) {
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int idx;
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if (cons->device && cons->device(cons, &idx) == p &&
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idx == tty_line) {
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kgdboc_io_ops.cons = cons;
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break;
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}
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}
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console_srcu_read_unlock(cookie);
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console_unlock();
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kgdb_tty_driver = p;
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kgdb_tty_line = tty_line;
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do_register:
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err = kgdb_register_io_module(&kgdboc_io_ops);
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if (err)
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goto noconfig;
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err = kgdb_register_nmi_console();
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if (err)
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goto nmi_con_failed;
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configured = 1;
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return 0;
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nmi_con_failed:
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kgdb_unregister_io_module(&kgdboc_io_ops);
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noconfig:
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kgdboc_unregister_kbd();
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configured = 0;
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return err;
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}
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static int kgdboc_probe(struct platform_device *pdev)
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{
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int ret = 0;
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mutex_lock(&config_mutex);
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if (configured != 1) {
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ret = configure_kgdboc();
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/* Convert "no device" to "defer" so we'll keep trying */
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if (ret == -ENODEV)
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ret = -EPROBE_DEFER;
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}
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mutex_unlock(&config_mutex);
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return ret;
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}
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static struct platform_driver kgdboc_platform_driver = {
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.probe = kgdboc_probe,
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.driver = {
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.name = "kgdboc",
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.suppress_bind_attrs = true,
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},
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};
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static int __init init_kgdboc(void)
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{
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int ret;
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/*
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* kgdboc is a little bit of an odd "platform_driver". It can be
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* up and running long before the platform_driver object is
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* created and thus doesn't actually store anything in it. There's
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* only one instance of kgdb so anything is stored as global state.
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* The platform_driver is only created so that we can leverage the
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* kernel's mechanisms (like -EPROBE_DEFER) to call us when our
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* underlying tty is ready. Here we init our platform driver and
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* then create the single kgdboc instance.
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*/
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ret = platform_driver_register(&kgdboc_platform_driver);
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if (ret)
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return ret;
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kgdboc_pdev = platform_device_alloc("kgdboc", PLATFORM_DEVID_NONE);
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if (!kgdboc_pdev) {
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ret = -ENOMEM;
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goto err_did_register;
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}
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ret = platform_device_add(kgdboc_pdev);
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if (!ret)
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return 0;
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platform_device_put(kgdboc_pdev);
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err_did_register:
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platform_driver_unregister(&kgdboc_platform_driver);
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return ret;
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}
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static void exit_kgdboc(void)
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{
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mutex_lock(&config_mutex);
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cleanup_kgdboc();
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mutex_unlock(&config_mutex);
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platform_device_unregister(kgdboc_pdev);
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platform_driver_unregister(&kgdboc_platform_driver);
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}
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static int kgdboc_get_char(void)
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{
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if (!kgdb_tty_driver)
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return -1;
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return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,
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kgdb_tty_line);
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}
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static void kgdboc_put_char(u8 chr)
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{
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if (!kgdb_tty_driver)
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return;
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kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,
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kgdb_tty_line, chr);
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}
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static int param_set_kgdboc_var(const char *kmessage,
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const struct kernel_param *kp)
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{
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size_t len = strlen(kmessage);
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int ret = 0;
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if (len >= MAX_CONFIG_LEN) {
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pr_err("config string too long\n");
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return -ENOSPC;
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}
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if (kgdb_connected) {
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pr_err("Cannot reconfigure while KGDB is connected.\n");
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return -EBUSY;
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}
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mutex_lock(&config_mutex);
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strcpy(config, kmessage);
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/* Chop out \n char as a result of echo */
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if (len && config[len - 1] == '\n')
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config[len - 1] = '\0';
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if (configured == 1)
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cleanup_kgdboc();
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/*
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* Configure with the new params as long as init already ran.
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* Note that we can get called before init if someone loads us
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* with "modprobe kgdboc kgdboc=..." or if they happen to use
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* the odd syntax of "kgdboc.kgdboc=..." on the kernel command.
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*/
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if (configured >= 0)
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ret = configure_kgdboc();
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/*
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* If we couldn't configure then clear out the config. Note that
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* specifying an invalid config on the kernel command line vs.
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* through sysfs have slightly different behaviors. If we fail
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* to configure what was specified on the kernel command line
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* we'll leave it in the 'config' and return -EPROBE_DEFER from
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* our probe. When specified through sysfs userspace is
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* responsible for loading the tty driver before setting up.
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*/
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if (ret)
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config[0] = '\0';
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mutex_unlock(&config_mutex);
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return ret;
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}
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static int dbg_restore_graphics;
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static void kgdboc_pre_exp_handler(void)
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{
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if (!dbg_restore_graphics && kgdboc_use_kms) {
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dbg_restore_graphics = 1;
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con_debug_enter(vc_cons[fg_console].d);
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}
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/* Increment the module count when the debugger is active */
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if (!kgdb_connected)
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try_module_get(THIS_MODULE);
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}
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static void kgdboc_post_exp_handler(void)
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{
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/* decrement the module count when the debugger detaches */
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if (!kgdb_connected)
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module_put(THIS_MODULE);
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if (kgdboc_use_kms && dbg_restore_graphics) {
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dbg_restore_graphics = 0;
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con_debug_leave();
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}
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kgdboc_restore_input();
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}
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static struct kgdb_io kgdboc_io_ops = {
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.name = "kgdboc",
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.read_char = kgdboc_get_char,
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.write_char = kgdboc_put_char,
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.pre_exception = kgdboc_pre_exp_handler,
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.post_exception = kgdboc_post_exp_handler,
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};
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#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
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static int kgdboc_option_setup(char *opt)
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{
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if (!opt) {
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pr_err("config string not provided\n");
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return 1;
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}
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if (strlen(opt) >= MAX_CONFIG_LEN) {
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pr_err("config string too long\n");
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return 1;
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}
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strcpy(config, opt);
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return 1;
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}
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__setup("kgdboc=", kgdboc_option_setup);
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/* This is only available if kgdboc is a built in for early debugging */
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static int __init kgdboc_early_init(char *opt)
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{
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kgdboc_option_setup(opt);
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configure_kgdboc();
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return 0;
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}
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early_param("ekgdboc", kgdboc_early_init);
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static int kgdboc_earlycon_get_char(void)
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{
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char c;
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if (!kgdboc_earlycon_io_ops.cons->read(kgdboc_earlycon_io_ops.cons,
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&c, 1))
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return NO_POLL_CHAR;
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return c;
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}
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static void kgdboc_earlycon_put_char(u8 chr)
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{
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kgdboc_earlycon_io_ops.cons->write(kgdboc_earlycon_io_ops.cons, &chr,
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1);
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}
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static void kgdboc_earlycon_pre_exp_handler(void)
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{
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struct console *con;
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static bool already_warned;
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int cookie;
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if (already_warned)
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return;
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/*
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* When the first normal console comes up the kernel will take all
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* the boot consoles out of the list. Really, we should stop using
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* the boot console when it does that but until a TTY is registered
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* we have no other choice so we keep using it. Since not all
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* serial drivers might be OK with this, print a warning once per
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* boot if we detect this case.
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*/
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cookie = console_srcu_read_lock();
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for_each_console_srcu(con) {
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if (con == kgdboc_earlycon_io_ops.cons)
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break;
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}
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console_srcu_read_unlock(cookie);
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if (con)
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return;
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already_warned = true;
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pr_warn("kgdboc_earlycon is still using bootconsole\n");
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}
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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");
|