Re: live kernel upgrades (was: live kernel patching design)

From: Pavel Machek
Date: Mon Feb 23 2015 - 06:42:22 EST

> More importantly, both kGraft and kpatch are pretty limited
> in what kinds of updates they allow, and neither kGraft nor
> kpatch has any clear path towards applying more complex
> fixes to kernel images that I can see: kGraft can only
> apply the simplest of fixes where both versions of a
> function are interchangeable, and kpatch is only marginally
> better at that - and that's pretty fundamental to both
> projects!
> I think all of these problems could be resolved by shooting
> for the moon instead:
> - work towards allowing arbitrary live kernel upgrades!
> not just 'live kernel patches'.

Note that live kernel upgrade would have interesting implications
outside kernel:

1) glibc does "what kernel version is this?" caches result
and alters behaviour accordingly.

2) apps will do recently_introduced_syscall(), get error
and not attempt it again.

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