# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
#	           ChangeSet	1.155   -> 1.156  
#	arch/i386/kernel/traps.c	1.11    -> 1.12   
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/02/22	hch@sb.bsdonline.org	1.156
# Clear TF flag when the kernel was entered using lcall7.
# (Patch from Stephan Springl)
# --------------------------------------------
#
diff -Nru a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
--- a/arch/i386/kernel/traps.c	Mon Feb 25 20:14:35 2002
+++ b/arch/i386/kernel/traps.c	Mon Feb 25 20:14:35 2002
@@ -478,9 +478,29 @@
 {
 	unsigned int condition;
 	struct task_struct *tsk = current;
+	unsigned long eip = regs->eip;
 	siginfo_t info;
 
 	__asm__ __volatile__("movl %%db6,%0" : "=r" (condition));
+
+	/*
+	 * Entering the kernel via lcall7 or lcall27 does not clear the TF bit.
+	 * Leaving it set in kernel code will stop the machine.  The first
+	 * instructions of lcall7 and lcall27 in entry.S save the CPU flags.
+	 * The saved flags should have the TF bit set, so we ignore this trap.
+	 */
+	if (eip == (unsigned long)&lcall7 || eip == (unsigned long)&lcall27)
+		return;
+
+	/*
+	 * After having saved the flags, TF will fire the single step trap
+	 * again.  This time TF should be cleared. It will be restored by the
+	 * iret instruction returning to user mode.  This way, the very next
+	 * instruction after lcall in the user programm will not be stopped at.
+	 */
+	eip--; /* pushfl is a one-byte opcode */
+	if (eip == (unsigned long)&lcall7 || eip == (unsigned long)&lcall27)
+		goto clear_TF;
 
 	/* Mask out spurious debug traps due to lazy DR7 setting */
 	if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3)) {