[RFC Patch 0/6] PPC64: Hardware Breakpoint interfaces - ver III

[K.Prasad]

Hi All,
        Please find a new patchset that includes suggestions from the community
and a few issues discovered during code inspection and testing. The changes are
as documented below.

Kindly let me know your comments on the same, in the absence of which I intend
to submit the patchset for upstream inclusion in the subsequent iteration.

Changelog - ver III
------------------
(Ver I: http://ozlabs.org/pipermail/linuxppc-dev/2009-May/071942.html) 
(Ver II: http://ozlabs.org/pipermail/linuxppc-dev/2009-May/072106.html)
19th May 2009
--------------

- Patches are based on commit 08f16e060bf54bdc34f800ed8b5362cdeda75d8b of -tip
tree.

- The declarations in arch/powerpc/include/asm/hw_breakpoint.h are done only if
CONFIG_PPC64 is defined. This eliminates the need to conditionally include this
header file.

- load_debug_registers() is done in start_secondary() i.e. during CPU
initialisation.

- arch_check_va_<> routines in hw_breakpoint.c are now replaced with a much
simpler is_kernel_addr() check in arch_validate_hwbkpt_settings()

- Return code of hw_breakpoint_handler() when triggered due to Lazy debug
register switching is now changed to NOTIFY_STOP.

- The ptrace code no longer sets the TIF_DEBUG task flag as it is proposed to
be done in register_user_hw_breakpoint() routine.

- hw_breakpoint_handler() is now modified to use hbp_kernel_pos value to
  determine if the trigger was a user/kernel space address. The DAR register
  value is checked with the address stored in 'struct hw_breakpoint' to avoid
  handling of exceptions that belong to kprobe/Xmon.

Thanks,
K.Prasad