[PATCH v6 0/9] Add support for memory sealing

[Adhemerval Zanella Netto]

On 13/10/25 05:17, Florian Weimer wrote:
> * Jeff Xu:
> 
>> Based on the discussion in [1], [2], and [3], it seems that the Nvidia
>> drivers issue is related to loading a 32-bit app and has either a
>> workaround or a fix. If this is indeed a bug, glibc memory sealing can
>> help prevent or detect such a bug earlier.
> 
>> Link: https://bugzilla.redhat.com/show_bug.cgi?id=2357062#c11 [1]
>> Link: https://bugzilla.rpmfusion.org/show_bug.cgi?id=7180#c25 [2]
>> Link: https://gitlab.freedesktop.org/glvnd/libglvnd/-/issues/252#note_2918141 [3]
> 
> I interpret this comment
> 
> | NVIDIA driver releases >= r575 will not do this (broken) patching by default.
> 
> <https://gitlab.freedesktop.org/glvnd/libglvnd/-/issues/252#note_2918155>
> 
> in such a way that the patching code is still there, just disabled by
> default.  I don't know what this means from a compatibility perspective.
> 
> We have since learned that UCX <https://github.com/openucx/ucx> performs
> similar patching.  It commonly shows up on systems as a dependency of
> OpenMPI <https://www.open-mpi.org/>, which is one of the more widely
> used MPI libraries.
> 
> We noticed a while back that the UCX patching does not work on POWER10
> 
>   ucx incorrectly patches glibc functions on Power10+ ppc64le systems
>   <https://github.com/openucx/ucx/issues/10780>
> 
> (it blindly overwrites instructions that it does not recognize).  So I'm
> not sure how actively this part of the code is being maintained, and if
> there's a chance to move it to a more supportable mechanism.
> 
>> There are two solutions for such a case in the future:
>> 1. Do not turn on sealing when building the main binary.
>> 2. Use the .gnu.mutable solution to mark specific areas/variables to
>> be not sealable.
> 
> (1) does not work if we are dealing with code that is usually loaded
> through dlopen (such as userspace graphics drivers and Python modules).
> 
> (2) does not really apply here because this would have to be done during
> the glibc build.

This (2) can be done at glibc build to make _dl_debug_update mutable, and
that's the idea of adding the mutable.