Re: [Valgrind-users] Clarification on functions in pub_tool_tooliface.h

[Siddharth N. <si...@gm...>]

Hi Ivo,

The goal is to get at the

Thanks,
Sid

On 9 May 2017 at 00:48, Ivo Raisr <iv...@iv...> wrote:

> 2017-05-08 20:39 GMT+02:00 Siddharth Nilakantan <si...@gm...>:
> > Hi Mike and Ivo,
> >
> > I noticed a thread where you guys had a discussion going.
> >
> > https://sourceforge.net/p/valgrind/mailman/message/35687503/
> >
> > I was playing around with writing a tool that does some online analysis
> of
> > register reads/writes. Basically, the tool needs to know every register
> > read/write performed by the user program.
>
> Hi Sid,
>
> What is the ultimate goal of your analysis tool?


I want to discover the critical paths in different phases of a program, the
first step of which is to able to build paths.


> > Due to minor ambiguity in the  documentation (both in the code and the
> PLDI paper), I discovered the hard
> > way that VG_(track_post_reg_write) and VG_(track_pre_reg_read) are
> functions
> > that are called only around syscalls. I'm guessing that any
> VG_(track_pre_*)
> > and VG_(track_post_*) functions occur only around syscalls.
>
> Yes, indeed.
> Every tool also works with the IR (intermediate representation) - this
> where you
> can catch (and instrument) register reads and writes.
>
> I.
>
Yes this is what I had originally started doing. I found it a bit more
challenging than expected. Iex_Gets represent register reads. The
instrument function sees a lot of IRExpr* for Load data or Put data, which
we need to recursively explore to find Iex_Gets...