Hi,
The attached set patches enable systemtap translator to probe kernel 
hardware breakpoints on x86.
It introduces the following language constructs :

1. probe kernel.data(ADDRESS).write     {....}   : To probe writes at 
the given address
2. probe kernel.data(ADDRESS).rw         {....}   : To probe read & 
write access to the given address.
3. probe kernel.data("SYMBOL").write   {....}
4. probe kernel.data("SYMBOL").rw       {....}   : Similar to 1,2, but 
using a symbol name as argument.

These are agnostic to dwarf/debuginfo and depend on the hardware 
breakpoint infrastructure for resolving symbols.

Things that remain to be done :
1. Translator support for probing hardware breakpoints on other 
architectures (ppc/s390 etc)
2. Implementation of userspace hardware breakpoints.

I'm still testing it...Looking for comments and feedback :-)

-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India