If not in the debugger or if the user requests it with the

debug.ddb_use_printf sysctl, output kernel debugger data to both the
console and kernel message buffer via printf.  This fixes the case where
backtrace() went directly to the console and should help debugging greatly.
Thanks to Ian Dowse for the work, minor edits or any bugs are by myself.

Submitted by:	iedowse

1 files changed, 27 insertions, 1 deletions

diff --git a/sys/ddb/db_output.c b/sys/ddb/db_output.c
index 2fa8554..464d9162 100644
--- a/sys/ddb/db_output.c
+++ b/sys/ddb/db_output.c
@@ -38,6 +38,8 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/cons.h>
+#include <sys/kernel.h>
+#include <sys/sysctl.h>
 
 #include <machine/stdarg.h>
 
@@ -66,8 +68,11 @@ static int	db_newlines;			/* # lines this page */
 static int	db_maxlines = -1;		/* max lines per page */
 static db_page_calloutfcn_t *db_page_callout = NULL;
 static void	*db_page_callout_arg = NULL;
+static int	ddb_use_printf = 0;
+SYSCTL_INT(_debug, OID_AUTO, ddb_use_printf, CTLFLAG_RW, &ddb_use_printf, 0,
+    "use printf for all ddb output");
 
-static void db_putchar(int c, void *arg);
+static void	db_putchar(int c, void *arg);
 
 /*
  * Force pending whitespace.
@@ -103,6 +108,27 @@ db_putchar(c, arg)
 	void *	arg;
 {
 
+	/*
+	 * If not in the debugger or the user requests it, output data to
+	 * both the console and the message buffer.
+	 */
+	if (!db_active || ddb_use_printf) {
+		printf("%c", c);
+		if (!db_active)
+			return;
+		if (c == '\r' || c == '\n')
+			db_check_interrupt();
+		if (c == '\n' && db_maxlines > 0 && db_page_callout != NULL) {
+			db_newlines++;
+			if (db_newlines >= db_maxlines) {
+				db_maxlines = -1;
+				db_page_callout(db_page_callout_arg);
+			}
+		}
+		return;
+	}
+
+	/* Otherwise, output data directly to the console. */
 	if (c > ' ' && c <= '~') {
 	    /*
 	     * Printing character.