Messages in this thread | | | Subject | Re: arm64 kvm built with clang doesn't boot | From | Marc Zyngier <> | Date | Fri, 16 Mar 2018 14:13:31 +0000 |
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Hi Andrey,
On 16/03/18 13:49, Andrey Konovalov wrote: > Hi! > > I've recently tried to boot clang built kernel on real hardware > (Odroid C2 board) instead of using a VM. The issue that I stumbled > upon is that arm64 kvm built with clang doesn't boot. > > Adding -fno-jump-tables compiler flag to arch/arm64/kvm/* helps. There > was a patch some time ago that did exactly that > (https://patchwork.kernel.org/patch/10060381/), but it wasn't accepted > AFAICT (see the discussion on that thread).
I wasn't aware of that discussion, but this is indeed quite annoying. Note that you should be able to restrict this to arch/arm64/kvm/hyp/* and virt/kvm/arm/hyp/*.
> What would be the best way to get this fixed?
Ideally, I'd like to see is a way to stick to PC-relative addressing within a compilation unit.
> I've also had to disable CONFIG_JUMP_LABEL to get the kernel boot > (even without kvm enabled), but that might be a different (though > related) issue.
That's quite bizarre. Does clang has the equivalent of "asm goto"? Or do you rely on reading a variable to decide whether or not to branch?
Thanks,
M. -- Jazz is not dead. It just smells funny...
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