<p></p>
<p dir="auto">I'm running Cog on aarch64, and because I have an old linux kernel (v3.18.140) which I cannot upgrade (it's a repurposed PostmarketOS Android device), Cog yields illegal instruction trying to execute <code>mrs x0, id_aa64isar0_el1</code>. This instruction is privileged, but later linux kernels trap and emulate it for userspace.</p>
<p dir="auto">Given that it's currently only being used to detect presence of atomic instructions (<code>self setHasAtomicInstructions: (idISAR0 >> 20 bitAnd: 2r1111) = 2r10</code>), and there's a kernel API for retrieving that specific bit of information (<a href="https://www.kernel.org/doc/html/latest/arm64/elf_hwcaps.html" rel="nofollow">https://www.kernel.org/doc/html/latest/arm64/elf_hwcaps.html</a> suggests HWCAP_ATOMICS), perhaps instead of using the instruction directly Cog could call the relevant <code>getauxval</code> variant?</p>
<p dir="auto">For now, I have the Stack VM running well on aarch64, so I can make progress, even if it is a little slower than it could be :-)</p>

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