Messages in this thread | | | From | Andrey Konovalov <> | Date | Fri, 20 Apr 2018 16:59:35 +0200 | Subject | Re: Clang arm64 build is broken |
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On Fri, Apr 20, 2018 at 10:13 AM, Marc Zyngier <marc.zyngier@arm.com> wrote: >> The issue is that >> clang doesn't know about the "S" asm constraint. I reported this to >> clang [2], and hopefully this will get fixed. In the meantime, would >> it possible to work around using the "S" constraint in the kernel? > > I have no idea, I've never used clang to build the kernel. Clang isn't > really supported to build the arm64 kernel anyway (as you mention > below), and working around clang deficiencies would mean that we leave > with the workaround forever. I'd rather enable clang once it is at > feature parity with GCC.
The fact that there are some existing issues with building arm64 kernel with clang doesn't sound like a good justification for adding new issues :)
However in this case I do believe that this is more of a bug in clang that should be fixed.
>> While we're here, regarding the other issue with kvm [3], I didn't >> receive any comments as to whether it makes sense to send the fix that >> adds -fno-jump-tables flag when building kvm with clang. > > Is that the only thing missing? Are you sure that there is no other way > for clang to generate absolute addresses that will then lead to a crash? > Again, I'd rather make sure we have the full picture.
Well, I have tried applying that patch and running kvm tests that I could find [1], and they passed (actually I think there was an issue with one of them, but I saw the same thing when I tried running them on a kernel built with GCC).
[1] https://www.linux-kvm.org/page/KVM-unit-tests
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