diff options
| -rw-r--r-- | drivers/tty/serial/serial_core.c | 75 | ||||
| -rw-r--r-- | include/linux/serial_core.h | 1 | ||||
| -rw-r--r-- | lib/Kconfig.debug | 8 |
3 files changed, 77 insertions, 7 deletions
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 5444293fe2e8..863e3e0c2d39 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -20,6 +20,7 @@ #include <linux/device.h> #include <linux/serial.h> /* for serial_state and serial_icounter_struct */ #include <linux/serial_core.h> +#include <linux/sysrq.h> #include <linux/delay.h> #include <linux/mutex.h> #include <linux/security.h> @@ -40,6 +41,8 @@ static struct lock_class_key port_lock_key; #define HIGH_BITS_OFFSET ((sizeof(long)-sizeof(int))*8) +#define SYSRQ_TIMEOUT (HZ * 5) + static void uart_change_speed(struct tty_struct *tty, struct uart_state *state, struct ktermios *old_termios); static void uart_wait_until_sent(struct tty_struct *tty, int timeout); @@ -3084,6 +3087,56 @@ void uart_insert_char(struct uart_port *port, unsigned int status, } EXPORT_SYMBOL_GPL(uart_insert_char); +#ifdef CONFIG_MAGIC_SYSRQ_SERIAL +static const char sysrq_toggle_seq[] = CONFIG_MAGIC_SYSRQ_SERIAL_SEQUENCE; + +static void uart_sysrq_on(struct work_struct *w) +{ + sysrq_toggle_support(1); + pr_info("SysRq is enabled by magic sequence on serial\n"); +} +static DECLARE_WORK(sysrq_enable_work, uart_sysrq_on); + +/** + * uart_try_toggle_sysrq - Enables SysRq from serial line + * @port: uart_port structure where char(s) after BREAK met + * @ch: new character in the sequence after received BREAK + * + * Enables magic SysRq when the required sequence is met on port + * (see CONFIG_MAGIC_SYSRQ_SERIAL_SEQUENCE). + * + * Returns false if @ch is out of enabling sequence and should be + * handled some other way, true if @ch was consumed. + */ +static bool uart_try_toggle_sysrq(struct uart_port *port, unsigned int ch) +{ + if (ARRAY_SIZE(sysrq_toggle_seq) <= 1) + return false; + + BUILD_BUG_ON(ARRAY_SIZE(sysrq_toggle_seq) >= U8_MAX); + if (sysrq_toggle_seq[port->sysrq_seq] != ch) { + port->sysrq_seq = 0; + return false; + } + + /* Without the last \0 */ + if (++port->sysrq_seq < (ARRAY_SIZE(sysrq_toggle_seq) - 1)) { + port->sysrq = jiffies + SYSRQ_TIMEOUT; + return true; + } + + schedule_work(&sysrq_enable_work); + + port->sysrq = 0; + return true; +} +#else +static inline bool uart_try_toggle_sysrq(struct uart_port *port, unsigned int ch) +{ + return false; +} +#endif + int uart_handle_sysrq_char(struct uart_port *port, unsigned int ch) { if (!IS_ENABLED(CONFIG_MAGIC_SYSRQ_SERIAL)) @@ -3093,9 +3146,13 @@ int uart_handle_sysrq_char(struct uart_port *port, unsigned int ch) return 0; if (ch && time_before(jiffies, port->sysrq)) { - handle_sysrq(ch); - port->sysrq = 0; - return 1; + if (sysrq_mask()) { + handle_sysrq(ch); + port->sysrq = 0; + return 1; + } + if (uart_try_toggle_sysrq(port, ch)) + return 1; } port->sysrq = 0; @@ -3112,9 +3169,13 @@ int uart_prepare_sysrq_char(struct uart_port *port, unsigned int ch) return 0; if (ch && time_before(jiffies, port->sysrq)) { - port->sysrq_ch = ch; - port->sysrq = 0; - return 1; + if (sysrq_mask()) { + port->sysrq_ch = ch; + port->sysrq = 0; + return 1; + } + if (uart_try_toggle_sysrq(port, ch)) + return 1; } port->sysrq = 0; @@ -3154,7 +3215,7 @@ int uart_handle_break(struct uart_port *port) if (port->has_sysrq) { if (port->cons && port->cons->index == port->line) { if (!port->sysrq) { - port->sysrq = jiffies + HZ*5; + port->sysrq = jiffies + SYSRQ_TIMEOUT; return 1; } port->sysrq = 0; diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 52404ef1694e..1f4443db5474 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -243,6 +243,7 @@ struct uart_port { unsigned long sysrq; /* sysrq timeout */ unsigned int sysrq_ch; /* char for sysrq */ unsigned char has_sysrq; + unsigned char sysrq_seq; /* index in sysrq_toggle_seq */ unsigned char hub6; /* this should be in the 8250 driver */ unsigned char suspended; diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 69def4a9df00..38a8f3c99579 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -431,6 +431,14 @@ config MAGIC_SYSRQ_SERIAL This option allows you to decide whether you want to enable the magic SysRq key. +config MAGIC_SYSRQ_SERIAL_SEQUENCE + string "Char sequence that enables magic SysRq over serial" + depends on MAGIC_SYSRQ_SERIAL + default "" + help + Specifies a sequence of characters that can follow BREAK to enable + SysRq on a serial console. + config DEBUG_FS bool "Debug Filesystem" help |