tty: kgdb_nmi: Automatically manage tty enable
At present it is not possible to boot with the ttyNMI0 console treating character input normally, instead character input triggers a prompt telling the user how to trigger the knock detector and enter the debugger. To use the console normally requires that kdb be entered and the nmi_console command be used to enable the console (or if only kgdb is present then gdb must directly manipulate the value of kgdb_nmi_tty_enabled). This patch automates the management of kgdb_nmi_tty_enabled by keeping track of the number of file handles that are open for reading and using that to determine how to tty should operate. The approach means that: 1. Behaviour before init starts is unchanged. 2. If the userspace runs a getty or some other interactive process on /dev/console (or explicitly on /dev/ttyNMI0) the tty will treat character input like any other tty. 3. If the userspace doesn't use /dev/console or if it uses /dev/console only to log messages (O_WRONLY) then the user prompt is retained. Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Cc: Jiri Slaby <jslaby@suse.cz> Cc: linux-serial@vger.kernel.org Cc: Jason Wessel <jason.wessel@windriver.com> Cc: kgdb-bugreport@lists.sourceforge.net Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -42,7 +42,7 @@ static char *kgdb_nmi_magic = "$3#33";
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module_param_named(magic, kgdb_nmi_magic, charp, 0600);
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module_param_named(magic, kgdb_nmi_magic, charp, 0600);
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MODULE_PARM_DESC(magic, "magic sequence to enter NMI debugger (default $3#33)");
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MODULE_PARM_DESC(magic, "magic sequence to enter NMI debugger (default $3#33)");
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static bool kgdb_nmi_tty_enabled;
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static atomic_t kgdb_nmi_num_readers = ATOMIC_INIT(0);
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static int kgdb_nmi_console_setup(struct console *co, char *options)
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static int kgdb_nmi_console_setup(struct console *co, char *options)
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{
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{
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@ -136,7 +136,7 @@ static int kgdb_nmi_poll_one_knock(void)
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n = 0;
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n = 0;
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}
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}
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if (kgdb_nmi_tty_enabled) {
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if (atomic_read(&kgdb_nmi_num_readers)) {
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kgdb_tty_recv(c);
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kgdb_tty_recv(c);
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return 0;
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return 0;
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}
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}
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@ -197,7 +197,8 @@ static void kgdb_nmi_tty_receiver(unsigned long data)
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priv->timer.expires = jiffies + (HZ/100);
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priv->timer.expires = jiffies + (HZ/100);
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add_timer(&priv->timer);
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add_timer(&priv->timer);
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if (likely(!kgdb_nmi_tty_enabled || !kfifo_len(&priv->fifo)))
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if (likely(!atomic_read(&kgdb_nmi_num_readers) ||
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!kfifo_len(&priv->fifo)))
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return;
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return;
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while (kfifo_out(&priv->fifo, &ch, 1))
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while (kfifo_out(&priv->fifo, &ch, 1))
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@ -270,13 +271,23 @@ static void kgdb_nmi_tty_cleanup(struct tty_struct *tty)
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static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file)
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static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file)
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{
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{
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struct kgdb_nmi_tty_priv *priv = tty->driver_data;
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struct kgdb_nmi_tty_priv *priv = tty->driver_data;
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unsigned int mode = file->f_flags & O_ACCMODE;
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int ret;
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return tty_port_open(&priv->port, tty, file);
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ret = tty_port_open(&priv->port, tty, file);
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if (!ret && (mode == O_RDONLY || mode == O_RDWR))
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atomic_inc(&kgdb_nmi_num_readers);
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return ret;
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}
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}
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static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file)
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static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file)
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{
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{
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struct kgdb_nmi_tty_priv *priv = tty->driver_data;
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struct kgdb_nmi_tty_priv *priv = tty->driver_data;
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unsigned int mode = file->f_flags & O_ACCMODE;
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if (mode == O_RDONLY || mode == O_RDWR)
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atomic_dec(&kgdb_nmi_num_readers);
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tty_port_close(&priv->port, tty, file);
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tty_port_close(&priv->port, tty, file);
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}
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}
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@ -313,12 +324,6 @@ static const struct tty_operations kgdb_nmi_tty_ops = {
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.write = kgdb_nmi_tty_write,
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.write = kgdb_nmi_tty_write,
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};
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};
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static int kgdb_nmi_enable_console(int argc, const char *argv[])
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{
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kgdb_nmi_tty_enabled = !(argc == 1 && !strcmp(argv[1], "off"));
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return 0;
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}
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int kgdb_register_nmi_console(void)
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int kgdb_register_nmi_console(void)
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{
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{
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int ret;
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int ret;
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@ -348,19 +353,10 @@ int kgdb_register_nmi_console(void)
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goto err_drv_reg;
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goto err_drv_reg;
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}
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}
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ret = kdb_register("nmi_console", kgdb_nmi_enable_console, "[off]",
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"switch to Linux NMI console", 0);
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if (ret) {
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pr_err("%s: can't register kdb command: %d\n", __func__, ret);
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goto err_kdb_reg;
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}
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register_console(&kgdb_nmi_console);
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register_console(&kgdb_nmi_console);
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arch_kgdb_ops.enable_nmi(1);
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arch_kgdb_ops.enable_nmi(1);
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return 0;
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return 0;
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err_kdb_reg:
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tty_unregister_driver(kgdb_nmi_tty_driver);
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err_drv_reg:
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err_drv_reg:
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put_tty_driver(kgdb_nmi_tty_driver);
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put_tty_driver(kgdb_nmi_tty_driver);
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return ret;
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return ret;
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@ -375,8 +371,6 @@ int kgdb_unregister_nmi_console(void)
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return 0;
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return 0;
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arch_kgdb_ops.enable_nmi(0);
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arch_kgdb_ops.enable_nmi(0);
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kdb_unregister("nmi_console");
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ret = unregister_console(&kgdb_nmi_console);
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ret = unregister_console(&kgdb_nmi_console);
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if (ret)
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if (ret)
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return ret;
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return ret;
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