X86 Debug Register - DR6 - Debug Status

Debug Status

The debug status register permits the debugger to determine which debug conditions have occurred. When the processor detects an enabled debug exception, it sets the low-order bits of this register (0,1,2,3) before entering the debug exception handler.

Note that the bits of DR6 are never cleared by the processor. To avoid any confusion in identifying the next debug exception, the debug handler should move zeros to DR6 immediately before returning.