Roland,
I have attached set of patches for providing breakpoint
mechanism for user processes as mentioned in
http://sourceware.org/ml/systemtap/2007-q1/msg00571.html. This patchset
provides API for insertion/removal of breakpoint. It also has provisions for
storing the original instructions in a separate area known as SSOL(Single
Step Out of Line) area. One of the intentions to store original instructions
in a separate area(SSOL area) is to allow user to do single stepping out of
line.
Utrace exploiters can make use of this feature for insertion/removal
of breakpoints and for single stepping over an out of line copy of the
instruction.
Prerequisite
Iam assuming that, API's for insertion and removal of breakpoint
are called when all threads of the process are quiesced. (Probably, one can
call these functions from a quiesce handler of a utrace engine.)
Iam posting this small piece of code with minimal feature(works only on
powerpc architecture) to collect feedback from community about my design
and approach in providing breakpoint assistance for user processes.
Patches attached in the mail briefly explains implementation,
followed by its limitations and todo section. Please let me know your
comments/views on this.
Thanks
Srinivasa DS
