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Date: Tue, 29 Apr 2025 11:17:42 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
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On Mon, Apr 28, 2025 at 12:34:27PM -0700, Linus Torvalds wrote:

> And yes, this really is a very potential and real security issue. In
> the kernel I don't think we have this ever happening, partly because a
> lot of configurations use gcc which afaik doesn't have this particular
> horrendous model of UD.

I see more and more people use clang, in a large part because of Rust.

Anyway, I've seen clang pull this stop-codegen-on-UB trick before (link
was upstream in the thread) and yes, it is horrific crap. At the time I
proposed emitting at the very least a UD2 instruction rather than just
straight up stopping code gen, but I think your proposal for a code-gen
knob to just not do this 'optimisation' at all is much better.