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From: "stsp at users dot sourceforge.net"
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To: glibc-bugs@sourceware.org
Subject: [Bug dynamic-link/30127] [rfe]: enable ld audit at run-time
Date: Thu, 02 Mar 2023 19:56:58 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D30127

--- Comment #32 from Stas Sergeev <stsp at users dot sourceforge.net> ---
(In reply to Jonathon Anderson from comment #31)
> I can't say the current solutions are appealing. You've made it very
> difficult for a dynamically-loaded auditor to accomplish any auditor-like

Posted v7 which just calls la_objopen()
for pre-existing libs, similar to dl_main().

> You mentioned in another ticket
> (https://sourceware.org/bugzilla/show_bug.cgi?id=3D30007#c2) that the who=
le
> point of this is to access data objects in the solib. Do you write this
> solib?

I write a shim that should load (via dlmem()) other
libs, built from some 30 years old sources (that neither
me nor anyone else writes today), and allows them to work
on a current system. I.e. this is a compatibility layer.
Compatibility layer, unfortunately, can't require changing
the legacy code. What you propose, will require mostly a
full rewrites, eg I have no idea how would the one identify
all pointers to all vars and change all such vars to a heap
objects...

> Could you override mmap itself for the files you want mapped in the right
> locations?

But it won't be relocated to that address.

> You mentioned DT_AUDIT wouldn't work, so I presume the executable is out =
of
> your control, e.g. you're extending a VM with an solib plugin? If so, do =
you
> not have the access to set LD_AUDIT in the environment before launching t=
he
> executable? You can always make your auditor "no-op" except when needed.

This is possible but a quite clumsy solution IMO.
And of course it would still need all other patches
(dlmem etc) except this one. So I'd rather concentrate
on making dlload_audit_module() suitable for your needs.

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