[PATCH] x86_64: Allow a kernel debugger to hide single steps in more cases.

Allow a kernel debugger to hide single steps in more cases.

Apparently helps the kgdb people.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/kernel/traps.c

@@ -691,7 +691,9 @@ asmlinkage void *do_debug(struct pt_regs * regs, unsigned long error_code)
 	tsk->thread.debugreg6 = condition;
 
 	/* Mask out spurious TF errors due to lazy TF clearing */
-	if (condition & DR_STEP) {
+	if ((condition & DR_STEP) &&
+	    (notify_die(DIE_DEBUGSTEP, "debugstep", regs, condition,
+			1, SIGTRAP) != NOTIFY_STOP)) {
 		/*
 		 * The TF error should be masked out only if the current
 		 * process is not traced and if the TRAP flag has been set

include/asm-x86_64/kdebug.h

@@ -23,6 +23,7 @@ enum die_val {
 	DIE_OOPS = 1,
 	DIE_INT3,
 	DIE_DEBUG,
+	DIE_DEBUGSTEP,
 	DIE_PANIC,
 	DIE_NMI,
 	DIE_DIE,