?? wrote:
Now, my question becomes clear. How to make my inserted function call
not affect the orginal state of program?
Try looking at a similar feature. One such similar feature is the
mcount calls emitted for profiling. The various solutions for mcount
include
1) saving lots of registers before the call, and restoring lots of
registers after the call. This has a high cost which may not work in
your case.
2) Writing mcount in assembly language, so that you can avoid clobbering
any registers.
Another possible solution is to use special compiler options when
compiling the function. For instance -fcall-saved-r14 will tell gcc
that r14 must be saved/restored in the prologue/epilogue when used. If
you split your instrumentation function into a separate file, and
compile with special options, this might work. You will need to use
such an option for every normal call clobbered register. There are
quite a few of them.
Another solution is to add the instrumentation earlier, and use expand_call.
--
Jim Wilson, GNU Tools Support, http://www.specifix.com
