[Bug dynamic-link/30134] DT_AUDIT is ignored for dlopen()ed solib

["janderson at rice dot edu" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=30134

Jonathon Anderson <janderson at rice dot edu> changed:

           What    |Removed                     |Added
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                 CC|                            |janderson at rice dot edu

--- Comment #8 from Jonathon Anderson <janderson at rice dot edu> ---
(In reply to Stas Sergeev from comment #7)
> (In reply to Florian Weimer from comment #6)
> > If the auditor cannot intercept libc.so.6 calls because it is already
> > loaded, then it can even use the main libc.so.6, and no fully separate
> > namespace is needed at all.
> 
> Certainly I don't know the implications,
> but in all projects where I needed to
> intercept the glibc calls I was using
> LD_PRELOAD (or the more advanced techniques
> like dlmopen() the libc into another
> namespace and intercept it there), but
> not LD_AUDIT. I've yet to understand is
> there something special in those complex
> pltenter/pltexit call-backs that you can't
> do by some other means, and are there
> many/any users of them?

pltenter/pltexit allows you to wrap symbols without knowing the signature of
the wrapped function. AFAIK there isn't a way to write a function that does
that in standard or GNU C (...without writing straight assembly based on the
call ABI, not fun).

That said, I don't personally know any users besides sotruss, one of the Glibc
dev tools. So do with that what you will. :D

> But having audit modules in the main
> namespace would help me a lot.

My group relies on LD_AUDIT to reliably "escape" the main namespace and acquire
symbols that won't be overridden by any other in-process tools operating at the
same time. Merging those namespaces will cause us some significant grief.

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