kernel/1035: traps causes DDB to be invoked even when ddb.panic = 0

[assar@stacken.kth.se]

>Number:         1035
>Category:       kernel
>Synopsis:       traps causes DDB to be invoked even when ddb.panic = 0
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Dec 29 09:40:01 MST 1999
>Last-Modified:
>Originator:     Assar Westerlund
>Organization:
none
>Release:        2.6 and current
>Environment:
	System      : OpenBSD 2.6
	Architecture: OpenBSD.i386
	Machine     : i386
>Description:

ddb is invoked on traps even when ddb.panic = 0.  This makes it hard
to have ddb in the running kernel of a remote machine.

>How-To-Repeat:

# This is a shell archive.  Save it in a file, remove anything before
# this line, and then unpack it by entering "sh file".  Note, it may
# create directories; files and directories will be owned by you and
# have default permissions.
#
# This archive contains:
#
#	Makefile
#	trapmod.1
#	trapmod.c
#
echo x - Makefile
sed 's/^X//' >Makefile << 'END-of-Makefile'
XLKM=trapmod
X
X.include <bsd.lkm.mk>
END-of-Makefile
echo x - trapmod.1
sed 's/^X//' >trapmod.1 << 'END-of-trapmod.1'
X.Dd December 29, 1999
X.Dt TRAP 8
X.Os
X.Sh NAME
X.Nm trapmod
X.Nd a kernel module that causes a trap
X.Sh DESCRIPTION
X.Nm
Xgenerates a trap when loaded that causes the kernel to either panic or
Xinvoke the debugger.
X.Sh EXAMPLES
Xmodload trapmod.o
X.Sh SEE ALSO
X.Xr lkm 4 ,
X.Xr modload 8 .
X.Sh STANDARDS
XNone (hopefully).
END-of-trapmod.1
echo x - trapmod.c
sed 's/^X//' >trapmod.c << 'END-of-trapmod.c'
X#include <sys/param.h>
X#include <sys/systm.h>
X#include <sys/conf.h>
X#include <sys/exec.h>
X#include <sys/lkm.h>
X
XMOD_MISC("trapmod")
X
Xint
Xtrapmod (struct lkm_table *lkmtp, int cmd, int ver)
X{
X  return *((int *)0);
X}
END-of-trapmod.c
exit

>Fix:

Index: arch/i386/db_interface.c
===================================================================
RCS file: /cvs/src/sys/arch/i386/i386/db_interface.c,v
retrieving revision 1.6
diff -u -w -r1.6 db_interface.c
--- arch/i386/db_interface.c	1996/05/07 07:21:34	1.6
+++ arch/i386/db_interface.c	1999/12/29 16:31:30
@@ -48,8 +48,8 @@
 #include <ddb/db_extern.h>
 #include <ddb/db_access.h>
 #include <ddb/db_output.h>
+#include <ddb/db_var.h>
 
-
 extern label_t	*db_recover;
 extern char *trap_type[];
 extern int trap_types;
@@ -83,17 +83,16 @@
 {
 	int s;
 
-#if 0
-	if ((boothowto&RB_KDB) == 0)
-		return(0);
-#endif
-
 	switch (type) {
 	case T_BPTFLT:	/* breakpoint */
 	case T_TRCTRAP:	/* single_step */
+	case T_NMI:	/* NMI */
 	case -1:	/* keyboard interrupt */
 		break;
 	default:
+		if (!db_panic)
+			return (0);
+
 		kdbprinttrap(type, code);
 		if (db_recover != 0) {
 			db_error("Faulted in DDB; continuing...\n");

>Audit-Trail:
>Unformatted: