From cf3c69ea3b765ca6b7b9b807220568eff20f8cb5 Mon Sep 17 00:00:00 2001
From: ws <ws@NetBSD.org>
Date: Mon, 20 Dec 1993 17:16:42 +0000
Subject: [PATCH] Correct support for single stepping of syscalls and fpu
 emulation

---
 sys/arch/i386/i386/locore.s |  3 +++
 sys/arch/i386/i386/trap.c   | 10 +++-------
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/sys/arch/i386/i386/locore.s b/sys/arch/i386/i386/locore.s
index 6791075cabdd..f88982a568dc 100644
--- a/sys/arch/i386/i386/locore.s
+++ b/sys/arch/i386/i386/locore.s
@@ -1867,6 +1867,9 @@ bpttraps:
 IDTVEC(syscall)
 	pushl	$0	# Room for tf_err
 	pushfl		# Room for tf_trapno
+	pushfl		# turn off trace bit
+	andb	$~(PSL_T>>8),1(%esp)
+	popfl
 	INTRENTRY
 	movl	TF_TRAPNO(%esp),%eax	# copy eflags from tf_trapno to fs_eflags
 	movl	%eax,TF_EFLAGS(%esp)
diff --git a/sys/arch/i386/i386/trap.c b/sys/arch/i386/i386/trap.c
index bf6bfea42aff..9e37ee87612f 100644
--- a/sys/arch/i386/i386/trap.c
+++ b/sys/arch/i386/i386/trap.c
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)trap.c	7.4 (Berkeley) 5/13/91
- *	$Id: trap.c,v 1.20 1993/12/19 06:58:15 mycroft Exp $
+ *	$Id: trap.c,v 1.21 1993/12/20 17:16:47 ws Exp $
  */
 
 /*
@@ -260,10 +260,8 @@ trap(frame)
 #ifdef MATH_EMULATE
 		rv = math_emulate(&frame);
 		if (rv == 0) {
-#ifdef		TRACE_EMU			/* XXX is this necessary? */
 			if (frame.tf_eflags & PSL_T)
 				goto trace;
-#endif
 			return;
 		}
 #else
@@ -378,10 +376,8 @@ trap(frame)
 
 #ifndef DDB
 	/* XXX need to deal with this when DDB is present, too */
-	case T_TRCTRAP:
-		/* kernel trace trap -- someone single stepping lcall's */
-		frame.tf_eflags &= ~PSL_T;
-		/* restored later from lcall frame */
+	case T_TRCTRAP: /* kernel trace trap -- someone single stepping lcall's */
+			/* syscall has to turn off the trace bit itself */
 		return;
 #endif