Re: [RFC v1 08/19] ptwrite uprobes / x86: Add a user fault notifier chain

[sashiko-bot@kernel.org]

> The ptwrite uprobes need to catch faults in the user probes, otherwise a
> bad probe could crash the program. For classic probes that is handled in
> the kernel, but with these new kinds of probes the crash happens in ring 3
> code.
> 
> The existing die chain cannot be used for this because it only handles
> kernel level faults. Add a new user fault notifier chain that is supported
> for #GP, #PF, #SS. It is only called before a signal would be delivered, so
> it doesn't slow down any hot paths. The fault handler can then handle the
> fault and prevent the signal.
> 
> Add register code and the hooks for the chain.
> 
> Some of the existing fault hardware workarounds could be converted to this
> in the future (not done yet)
> 
> Assisted-by: omp:gpt-5.6-luna
> Signed-off-by: Andi Kleen <ak@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260831150651.1134594-1-ak@kernel.org?part=8