Thanks to a suggestion by William Kucharski (like all good ideas, this
one is obviously correct), the kdb serial console sequence is now
tweakable. The patch below is incremental on kdb-v1.8-2.4.5-pre1 and
will be included in the next kdb patch set.
Index: 5-pre1.2/drivers/char/serial.c
--- 5-pre1.2/drivers/char/serial.c Thu, 26 Apr 2001 16:48:50 +1000 kaos
(linux-2.4/b/c/22_serial.c 1.4.1.2 644)
+++ 5-pre1.2(w)/drivers/char/serial.c Tue, 15 May 2001 16:17:03 +1000 kaos
+(linux-2.4/b/c/22_serial.c 1.4.1.2 644)
@@ -212,16 +212,25 @@ static char *serial_revdate = "2001-03-2
#if defined(CONFIG_KDB)
#include <linux/kdb.h>
/*
- * kdb_serial_line records the serial line number of the
- * first serial console. kdb_info will be set upon receipt
- * of the first ^A (which cannot happen until the port is
- * opened and the interrupt handler attached). To enter
- * kdb before this on a serial console-only system, you must
- * use the 'kdb=early' flag to lilo and set the appropriate
- * breakpoints.
+ * kdb_serial_line records the serial line number of the first serial console.
+ * NOTE: The kernel ignores characters on the serial line unless a user space
+ * program has opened the line first. To enter kdb before user space has opened
+ * the serial line, you can use the 'kdb=early' flag to lilo and set the
+ * appropriate breakpoints.
+ *
+ * kdb_serial_str[] is the sequence that the user must enter on the serial
+ * console to invoke kdb. It can be a single character such as "\001"
+ * (control-A) or multiple characters such as "\eKdB". NOTE: All except the
+ * last character are passed through to the application reading from the serial
+ * console.
+ *
+ * I tried to make the sequence a CONFIG_ option but most of CML1 cannot cope
+ * with '\' in strings, CML2 should be able to do it. KAO.
*/
static int kdb_serial_line = -1;
+static char kdb_serial_str[] = "\001";
+static char *kdb_serial_ptr = kdb_serial_str;
#endif /* CONFIG_KDB */
/*
* All of the compatibilty code so we can compile serial.c against
@@ -581,11 +590,15 @@ static _INLINE_ void receive_chars(struc
do {
ch = serial_inp(info, UART_RX);
#if defined(CONFIG_KDB)
- if ((info->line == kdb_serial_line)
- && (ch == 1) /* CNTRL-A */
- && kdb_on) {
- kdb(KDB_REASON_KEYBOARD, 0, (kdb_eframe_t)regs);
- break;
+ if ((info->line == kdb_serial_line) && kdb_on) {
+ if (ch == *kdb_serial_ptr) {
+ if (!(*++kdb_serial_ptr)) {
+ kdb(KDB_REASON_KEYBOARD, 0, (kdb_eframe_t)regs);
+ kdb_serial_ptr = kdb_serial_str;
+ break;
+ }
+ } else
+ kdb_serial_ptr = kdb_serial_str;
}
#endif /* CONFIG_KDB */
if (tty->flip.count >= TTY_FLIPBUF_SIZE)
