[PATCH v2 1/3] compiler_types: Introduce the Clang __preserve_most function attribute

[Peter Zijlstra]

On Mon, Aug 07, 2023 at 02:36:53PM +0200, Florian Weimer wrote:

> I think the GCC vs Clang thing is expected to work today, isn't it?
> Using the Clang-based BPF tools with a GCC-compiled kernel requires a
> matching ABI.

Nope, all bets are off. There is no module ABI, in the widest possible
sense.

There's all sorts of subtle breakage, I don't remember the exact
details, but IIRC building the kernel with a compiler that has
asm-goto-output and modules with a compiler that doesn't have it gets
you fireworks.

We absolutely do even bother tracking any of this.

There's also things like GCC plugins, they can randomly (literally in
the case of struct randomization) change things around that isn't
compatible with what the other compiler does -- or perhaps even a later
version of the same compiler.