[DynInst_API:] DynInst tutorial instrumenting malloc questions and issues

[Martijn <martijn@xxxxxxxxxxxxxxxxx>]

Hello,

I am looking at the DynInst API to instrument applications to detect memory errors.

Studying the maxarg.C tutorial code on http://www.paradyn.org/tutorial/ with DynInst 9.2.0 on Ubuntu 16.04 Desktop and gcc 5.3.1, I encounter two issues:

1. the maxarg tutorial tries to add a snippet to malloc() in libc.so. It tries to find the malloc function in the module with substring "libc" using findModule(). As I understand the API, this will find the module of libc.so.6, but malloc() may well be implemented in a separate source file, and hence another module name. I corrected the example by first obtaining the libc.so.6 object, and then using findFunction on the object, which walks over all modules in the libc.so.6. Clearly, I am missing a findObject() function on the BPatch_image to do this.
   
2. More severe, on Unbuntu 16.04 gcc 5.3.1, libc.so.6 does not define malloc(). The only definition is (weakly defined) in ld-2.23.so, which is a dependency of libc.so.6, but not of the test binary. Even if I explicitly link the test binary against ld-2.23.so, this library is not available in the list of objects on the image. So the maxargs example cannot find malloc() to instrument. Note that when opening the test binary statically (i.e., not via createProcess()), the ld-2.23.so dependency is included in the list of objects on the image. Could you enlighten me on what I am missing here? E.g., am I missing an event handler for a dynamic loading of ld-2.23.so?

I hope you can help me further, as I am impressed with the platform independence that DynInst offers. Thanks,

 Martijn

---------

Martijn Rutten

martijn@xxxxxxxxxxxxxxxxx

+31638237286