Proposal to reduce anti-bundling requirements

[Florian Weimer]

On 09/16/2015 03:47 PM, Dave Love wrote:
> Michael Stahl <mstahl at redhat.com> writes:
> 
>>> Symbol interposition is used a lot for very useful features, blocking
>>> interposition would break a lot of stuff.
>>
>> really?  i've always thought that it was only useful for libc symbols,
>> but maybe that's because i don't work on base OS stuff.
> 
> I'd guess most uses are not to do with base OS stuff.  It's important in
> a lot of cases in research-type computing support, though that doesn't
> seem to count for much.
> 
> Profiling and other instrumentation in the high performance computing
> world (where it's taken quite seriously) typically uses LD_PRELOAD
> libraries.

I think it is important to keep the LD_PRELOAD case separate from
implicit interposition between the main program (if linked with -E) and
DSOs or between different DSOs.  LD_PRELOAD is quite explicit in what it
wants to do.

What I'm really interested in is a use case where something pulls in a
library with DT_NEEDED and relies on predictable linking order to
override a specific symbol.

We have cases where this happens, but they all seem accidents to me.

-- 
Florian Weimer / Red Hat Product Security