[ltt-dev] Question about instruction pointer and address attributes

[Mathieu Desnoyers]

* Francis Giraldeau (Francis.Giraldeau at USherbrooke.ca) wrote:
> Hi,
>
> I want to relate trace events to source code. For testing, I did a small 
> C program that does a file access. In the event kernel.syscall_entry 
> sys_access, I got the instruction pointer ip=0x7fa4fba26ee7. I dumped the 
> process memory map from /proc/$PID/maps, and this address doesn't fit in 
> the process memory space. It's somewhat close to libc addresses, that are 
> in the range of 0x7f6471f56000-0x7f64724fc000.
>
> Another example, inside a TRAP, I got two addresses,  
> ip=0xffffffff812c722b

This looks like the vDSO.

 and address=0x7fa4fba2cbc0, those two addresses  
> doesn't map in the process space.
>
> First, what is the difference between ip and address attribute? And wow 
> does the ip can be converted back to the process address space?

Make sure you cat the /proc/$PID/maps from the exact same process you
gather the trace from, because the addresses at which the libraries are
loaded and the stack is located are randomised between executions.

Cheers,

Mathieu

>
> Cheer,
>
> Francis
>
>
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-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com