[Valgrind-developers] allowing skins to instrument conditional jumps

[Jeremy F. <je...@go...>]

I'm writing a skin to generate gprof-like output, so I need to see all
the edges in the control flow graph. In particular, I'd like to insert
some instrumentation code which is run IFF a conditional branch is
taken.

I see a few options:
        * something to properly represent uInstr sequences with
          conditionals within the ucode for one real instruction (ie,
          some way of representing jumps to real addresses rather than
          simulated addresses).  Sounds messy.
        * Intercept the jump target address and generate a completely
          new piece of code at some place within the simulated address
          space.  Ugly.
        * Introduce a new exceptional value for ebp when it is passed
          back into the dispatcher to trigger a call into the skin. 
          Would need some way to attach some kind of argument values for
          the call (encode in %edx?).  Seems like the least nasty.

Any opinions?

    J