svn commit: r332752 - in head/sys: amd64/amd64 i386/i386 powerpc/powerpc sys

[Andriy Gapon]

Author: avg
Date: Thu Apr 19 05:06:56 2018
New Revision: 332752
URL: https://svnweb.freebsd.org/changeset/base/332752

Log:
  set kdb_why to "trap" when calling kdb_trap from trap_fatal
  
  This will allow to hook a ddb script to "kdb.enter.trap" event.
  Previously there was no specific name for this event, so it could only
  be handled by either "kdb.enter.unknown" or "kdb.enter.default" hooks.
  Both are very unspecific.
  
  Having a specific event is useful because the fatal trap condition is
  very similar to panic but it has an additional property that the current
  stack frame is the frame where the trap occurred.  So, both a register
  dump and a stack bottom dump have additional information that can help
  analyze the problem.
  
  I have added the event only on architectures that have trap_fatal()
  function defined.  I haven't looked at other architectures.  Their
  maintainers can add support for the event later.
  
  Sample script:
  kdb.enter.trap=bt; show reg; x/aS $rsp,20; x/agx $rsp,20
  
  Reviewed by:	kib, jhb, markj
  MFC after:	11 days
  Sponsored by:	Panzura
  Differential Revision: https://reviews.freebsd.org/D15093

Modified:
  head/sys/amd64/amd64/trap.c
  head/sys/i386/i386/trap.c
  head/sys/powerpc/powerpc/trap.c
  head/sys/sys/kdb.h

Modified: head/sys/amd64/amd64/trap.c
==============================================================================
--- head/sys/amd64/amd64/trap.c	Thu Apr 19 03:31:41 2018	(r332751)
+++ head/sys/amd64/amd64/trap.c	Thu Apr 19 05:06:56 2018	(r332752)
@@ -761,6 +761,9 @@ trap_fatal(frame, eva)
 	u_int type;
 	struct soft_segment_descriptor softseg;
 	char *msg;
+#ifdef KDB
+	bool handled;
+#endif
 
 	code = frame->tf_err;
 	type = frame->tf_trapno;
@@ -811,9 +814,13 @@ trap_fatal(frame, eva)
 	    curproc->p_pid, curthread->td_name);
 
 #ifdef KDB
-	if (debugger_on_panic)
-		if (kdb_trap(type, 0, frame))
+	if (debugger_on_panic) {
+		kdb_why = KDB_WHY_TRAP;
+		handled = kdb_trap(type, 0, frame);
+		kdb_why = KDB_WHY_UNSET;
+		if (handled)
 			return;
+	}
 #endif
 	printf("trap number		= %d\n", type);
 	if (type <= MAX_TRAP_MSG)

Modified: head/sys/i386/i386/trap.c
==============================================================================
--- head/sys/i386/i386/trap.c	Thu Apr 19 03:31:41 2018	(r332751)
+++ head/sys/i386/i386/trap.c	Thu Apr 19 05:06:56 2018	(r332752)
@@ -879,6 +879,9 @@ trap_fatal(frame, eva)
 	int code, ss, esp;
 	u_int type;
 	struct soft_segment_descriptor softseg;
+#ifdef KDB
+	bool handled;
+#endif
 
 	code = frame->tf_err;
 	type = frame->tf_trapno;
@@ -940,12 +943,13 @@ trap_fatal(frame, eva)
 
 #ifdef KDB
 	if (debugger_on_panic) {
+		kdb_why = KDB_WHY_TRAP;
 		frame->tf_err = eva;	/* smuggle fault address to ddb */
-		if (kdb_trap(type, 0, frame)) {
-			frame->tf_err = code;	/* restore error code */
+		handled = kdb_trap(type, 0, frame);
+		frame->tf_err = code;	/* restore error code */
+		kdb_why = KDB_WHY_UNSET;
+		if (handled)
 			return;
-		}
-		frame->tf_err = code;		/* restore error code */
 	}
 #endif
 	printf("trap number		= %d\n", type);

Modified: head/sys/powerpc/powerpc/trap.c
==============================================================================
--- head/sys/powerpc/powerpc/trap.c	Thu Apr 19 03:31:41 2018	(r332751)
+++ head/sys/powerpc/powerpc/trap.c	Thu Apr 19 05:06:56 2018	(r332752)
@@ -449,11 +449,19 @@ trap(struct trapframe *frame)
 static void
 trap_fatal(struct trapframe *frame)
 {
+#ifdef KDB
+	bool handled;
+#endif
 
 	printtrap(frame->exc, frame, 1, (frame->srr1 & PSL_PR));
 #ifdef KDB
-	if (debugger_on_panic && kdb_trap(frame->exc, 0, frame))
-		return;
+	if (debugger_on_panic) {
+		kdb_why = KDB_WHY_TRAP;
+		handled = kdb_trap(frame->exc, 0, frame);
+		kdb_why = KDB_WHY_UNSET;
+		if (handled)
+			return;
+	}
 #endif
 	panic("%s trap", trapname(frame->exc));
 }

Modified: head/sys/sys/kdb.h
==============================================================================
--- head/sys/sys/kdb.h	Thu Apr 19 03:31:41 2018	(r332751)
+++ head/sys/sys/kdb.h	Thu Apr 19 05:06:56 2018	(r332752)
@@ -101,6 +101,7 @@ extern const char * volatile kdb_why;
 #define	KDB_WHY_UNSET		NULL		/* No reason set. */
 #define	KDB_WHY_PANIC		"panic"		/* panic() was called. */
 #define	KDB_WHY_KASSERT		"kassert"	/* kassert failed. */
+#define	KDB_WHY_TRAP		"trap"		/* Fatal trap. */
 #define	KDB_WHY_SYSCTL		"sysctl"	/* Sysctl entered debugger. */
 #define	KDB_WHY_BOOTFLAGS	"bootflags"	/* Boot flags were set. */
 #define	KDB_WHY_WITNESS		"witness"	/* Witness entered debugger. */