I noticed that the PTRACE_POKEUSR code incorrectly clears bits 56-58
of _all_ debug registers.  The intention was to only clear it for
odd-numbered registers, to ensure that user-level can only set
user-level data/instruction-breakpoints.  Patch below fixes this problem.
The patch also replaces explicit clearing of the single-step and
taken-branch PSR bits with a call to ptrace_disable() for PTRACE_KILL.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>