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diff --git a/private/ntos/nthals/halalpha/haltsup.s b/private/ntos/nthals/halalpha/haltsup.s
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+//      TITLE("Halt Interrupt Support")
+//++
+//
+// Copyright (c) 1992  Digital Equipment Corporation
+// Copyright (c) 1993  Digital Equipment Corporation
+//
+// Module Name:
+//
+//    haltsup.s
+//
+// Abstract:
+//
+//    This module implements the code necessary to field halt button
+//    interrupts.
+//
+// Author:
+//
+//    Joe Notarangelo 18-Dec-1992  
+//
+// Environment:
+//
+//    Kernel mode only, IRQL halt synchronization level.
+//
+// Revision History:
+//
+//--
+
+#if !(DBG)
+
+//
+// Boolean value that controls whether to break or not for a halt button
+// interrupt on a free build.  The default value is zero and must be set
+// in the debugger to a non-zero value to trigger the breakpoint action
+// when the halt button is pressed.
+//
+
+	.data
+
+	.globl	HalpHaltButtonBreak
+HalpHaltButtonBreak:
+	.long	0 : 1
+
+#endif //!DBG
+
+
+#include "halalpha.h"
+
+        SBTTL("Halt Interrupt Support")
+//++
+//
+// Routine Description:
+//
+//    This routine is entered as the result of a halt interrupt caused by
+//    a human pushing the halt switch on the system box.  This routine is 
+//    connected directly into the IDT.  The halt interrupt is mechanical and 
+//    does not require an interrupt acknowledge.
+//
+// Arguments:
+//
+//    s6/fp - Supplies a pointer to a trap frame.
+//
+// Return Value:
+//
+//    None.
+//
+//--
+
+	.struct 0
+HaltRa:	.space  8			// saved return address
+	.space	8			// fill for alignment
+HaltFrameLength:
+
+        NESTED_ENTRY(HalpHaltInterrupt, ExceptionFrameLength, zero)
+
+	lda	sp, -HaltFrameLength(sp) // allocate stack frame
+	stq	ra, HaltRa(sp)		// save ra
+
+	PROLOGUE_END
+
+
+#if DBG
+
+//
+// Always stop in the debugger if this is a checked build.
+//
+
+	BREAK_DEBUG_STOP		// stop in the debugger
+
+#else
+
+//
+// If this is a free build then check the variable HalpHaltButtonBreak,
+// if it is non-zero then take the breakpoint, otherwise ignore it.
+//
+
+        lda	t0, HalpHaltButtonBreak // get the address of the boolean
+	ldl	t0, 0(t0)		// read the boolean
+	beq	t0, 10f			// if eq, don't stop
+	
+	BREAK_DEBUG_STOP		// stop in the debugger
+
+10:
+
+#endif //DBG
+
+	ldq	ra, HaltRa(sp)		// save ra
+	lda	sp, HaltFrameLength(sp) // deallocate stack frame
+	ret	zero, (ra)		// interrupt is dismissed
+
+        .end HalpHaltInterrupt