Subject: [Patch 0/6] PPC64-HWBKPT: Hardware Breakpoint interfaces - ver VI

From: "K.Prasad" <[email-masked]>
Date: Wed, 10 Jun 2009 14:37:25 +0530

Hi David,
	Please find a new set of patches that implement the changes described below.

Changelog - ver VI
-------------------
(Ver I: http://ozlabs.org/pipermail/linuxppc-dev/2009-May/071942.html) 
(Ver II: http://ozlabs.org/pipermail/linuxppc-dev/2009-May/072106.html)
(Ver III: http://ozlabs.org/pipermail/linuxppc-dev/2009-May/072387.html
(Ver IV: http://ozlabs.org/pipermail/linuxppc-dev/2009-May/072518.html
(Ver V: http://lists.ozlabs.org/pipermail/linuxppc-dev/2009-June/072749.html)
9th June June 2009
-------------------

Changelog - ver VI
------------------
The task of identifying 'genuine' breakpoint exceptions from those caused by
'out-of-range' accesses turned out to be more tricky than originally thought.
Some changes to this effect were made in version IV of this patchset, but they
were not sufficient for user-space. Basically the breakpoint address received
through ptrace is always aligned to 8-bytes since ptrace receives an encoded
'data' (consisting of address | translation_enable | bkpt_type), and the size of
the symbol is not known. However for kernel-space addresses, the symbol-size can
be determined using kallsyms_lookup_size_offset() and this is used to check if
DAR (in the exception context) is
'bkpt_address <= DAR <= (bkpt_address + symbol_size)', failing which we conclude
it as a stray exception.

The following changes are made to enable check:
- Addition of a symbolsize field in 'struct arch_hw_breakpoint' field.
- Store the size of the 'watched' kernel symbol into 'symbolsize' field in
  arch_store_info(0 routine.
- Verify if the above described condition is true when is_one_shot is FALSE in
  hw_breakpoint_handler().

Kindly let me know your comments on the same.

Thanks,
K.Prasad