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-rw-r--r--include/linux/serial_core.h83
1 files changed, 65 insertions, 18 deletions
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index cf3a1e789bf5..85598519b3ea 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -150,6 +150,9 @@ struct uart_port {
struct console *cons; /* struct console, if any */
#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)
unsigned long sysrq; /* sysrq timeout */
+#ifdef CONFIG_MAGIC_SYSRQ_BREAK_EMULATION
+ char sysrq_emul; /* sysrq break emulation */
+#endif
#endif
upf_t flags;
@@ -364,24 +367,6 @@ extern void uart_handle_cts_change(struct uart_port *uport,
extern void uart_insert_char(struct uart_port *port, unsigned int status,
unsigned int overrun, unsigned int ch, unsigned int flag);
-#ifdef SUPPORT_SYSRQ
-static inline int
-uart_handle_sysrq_char(struct uart_port *port, unsigned int ch)
-{
- if (port->sysrq) {
- if (ch && time_before(jiffies, port->sysrq)) {
- handle_sysrq(ch);
- port->sysrq = 0;
- return 1;
- }
- port->sysrq = 0;
- }
- return 0;
-}
-#else
-#define uart_handle_sysrq_char(port,ch) ({ (void)port; 0; })
-#endif
-
/*
* We do the SysRQ and SAK checking like this...
*/
@@ -406,6 +391,68 @@ static inline int uart_handle_break(struct uart_port *port)
return 0;
}
+#if defined(SUPPORT_SYSRQ) && defined(CONFIG_MAGIC_SYSRQ_BREAK_EMULATION)
+/*
+ * Emulate a break if we are the serial console and receive ^B, ^R, ^K.
+ */
+static inline int
+uart_handle_sysrq_break_emulation(struct uart_port *port, unsigned int ch)
+{
+ const unsigned int ctrlb = 'B' & 31;
+ const unsigned int ctrlr = 'R' & 31;
+ const unsigned int ctrlk = 'K' & 31;
+
+ if (uart_console(port)) {
+ if ((port->sysrq_emul == 0 && ch == ctrlb) ||
+ (port->sysrq_emul == ctrlb && ch == ctrlr)) {
+ /* for either of the first two trigger characters
+ * update the state variable and move on.
+ */
+ port->sysrq_emul = ch;
+ return 1;
+ } else if (port->sysrq_emul == ctrlr &&
+ ch == ctrlk && uart_handle_break(port)) {
+ /* the break has already been emulated whilst
+ * evaluating the condition, tidy up and move on
+ */
+ port->sysrq_emul = 0;
+ return 1;
+ }
+ }
+
+ if (port->sysrq_emul) {
+ /* received a partial (false) trigger, tidy up and move on */
+ uart_insert_char(port, 0, 0, ctrlb, TTY_NORMAL);
+ if (port->sysrq_emul == ctrlr)
+ uart_insert_char(port, 0, 0, ctrlr, TTY_NORMAL);
+ port->sysrq_emul = 0;
+ }
+
+ return 0;
+}
+#else
+#define uart_handle_sysrq_break_emulation(port,ch) ({ (void)port; 0; })
+#endif
+
+#ifdef SUPPORT_SYSRQ
+static inline int
+uart_handle_sysrq_char(struct uart_port *port, unsigned int ch)
+{
+ if (port->sysrq) {
+ if (ch && time_before(jiffies, port->sysrq)) {
+ handle_sysrq(ch);
+ port->sysrq = 0;
+ return 1;
+ }
+ port->sysrq = 0;
+ }
+
+ return uart_handle_sysrq_break_emulation(port, ch);
+}
+#else
+#define uart_handle_sysrq_char(port,ch) ({ (void)port; 0; })
+#endif
+
/*
* UART_ENABLE_MS - determine if port should enable modem status irqs
*/