Re: [DynInst_API:] Call Redirection to a Library Function

[Bill Williams <bill@xxxxxxxxxxx>]

On 04/27/2014 09:01 AM, Sergej Proskurin wrote:
> Hello,
>
> The following code snippet tries to redirect an edge of the type CALL to
> the first basic block of the function 'func_name', which is included
> within a loaded library (simple .so file). Unfortunately, the code gets
> an error while trying to redirect the edge to the above mentioned
> libarary function. Is there any possibility in Dyninst to address this
> kind of issue or is not possible to redirect edges to library functions?
Sergej--

There are many things that could go wrong with code modification in 
general, but this is also functionality that's supported through 
Dyninst's BPatch layer directly. There are function replacement (all 
calls to foo now call bar), function wrapping (all calls to foo call 
bar, which then calls foo), and callsite replacement (this call to foo 
now calls bar) primitives available, and one of those is likely to be 
easier to work with than PatchAPI code modification for a simple 
function-level graft.
--bw

> ---
> ...
>
> BPatch_Vector<BPatch_function *> funcs;
> std::vector<BPatch_basicBlock*> blocks;
> BPatch_function *func_epilog;
> BPatch_image* img;
> PatchBlock *block;
>
> if(out_edge->type() == EdgeTypeEnum::CALL) {
>      bool res;
>
>      img = app->getImage();
>      img->findFunction(func_name, funcs, true, true, false);
>
>      if(!funcs.size()) {
>          error("Could not find function to be instrumented: " + func_name);
>          return;
>      }
>
>      func_epilog = funcs[0];
>
>      cfg = func_epilog->getCFG();
>      cfg->getEntryBasicBlock(blocks);
>
>      block = PatchAPI::convert(*blocks.rbegin());
>
>      res = PatchModifier::redirect(out_edge, block);
>      if(!res) {
>          error("Could not redirect edge");
>      }
> }
> ...
> ---
>
> I would really appreciate any help with the stated issue.
> Thank you very much in advance.
>
> Best regards,
> Sergej
>
>
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--
--bw

Bill Williams
Paradyn Project
bill@xxxxxxxxxxx