On Wed, Sep 23, 2020 at 08:11:36PM +0200, Solar Designer wrote:

On Wed, Sep 23, 2020 at 04:39:31PM +0200, Florian Weimer wrote:

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* Solar Designer:

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While I share my opinion here, I don't mean that to block Madhavan's
work.  I'd rather defer to people more knowledgeable in current userland
and ABI issues/limitations and plans on dealing with those, especially
to Florian Weimer.  I haven't seen Florian say anything specific for or
against Madhavan's proposal, and I'd like to.  (Have I missed that?)

[...]

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I think it's unnecessary for the libffi use case.

[...]

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I don't know if kernel support could
make sense in this context, but it would be a completely different
patch.

Thanks.  Are there currently relevant use cases where the proposed
trampfd would be useful and likely actually made use of by userland -
e.g., specific userland project developers saying they'd use it, or
Madhavan intending to develop and contribute userland patches?

Alexander

The trampoline it provides in this version can be implemented completely
in userspace. The kernel part of it is essentially just providing a way
to do text relocations without needing a WX mapping, but the text
relocations would be unnecessary in the first place if the trampoline
was position-independent code.