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Date: Sun, 6 May 2018 09:41:58 +0200 From: Dmitry Vyukov <dvyukov@...gle.com> To: sedat.dilek@...il.com Cc: Matthias Kaehlcke <mka@...omium.org>, lkml <linux-kernel@...r.kernel.org>, Arnd Bergmann <arnd@...db.de>, Nick Desaulniers <nick.desaulniers@...il.com> Subject: Re: Clang patch stacks for LTS kernels (v4.4 and v4.9) and status update On Sun, May 6, 2018 at 8:35 AM, Sedat Dilek <sedat.dilek@...il.com> wrote: > On Mon, Apr 23, 2018 at 7:42 PM, Matthias Kaehlcke <mka@...omium.org> wrote: > [...] >>> [ ASM-GOTO ] >>> >>> Foremore, I have seen you have a "refs/sandbox/mka/llvm/v4.14" Git branch. >>> Linux v4.14 is also an LTS release. >> >> Yes, there is also a follow up post: >> https://lkml.org/lkml/2017/11/22/943 >> >>> After Linux v4.9 "asm-goto" support was added which is GCC specific. >> >> asm-goto was optional until a few weeks ago, when x86 maintainers >> decided to make it mandatory, and thus break clang builds for x86: >> >> https://lkml.org/lkml/2018/4/2/486 >> >>> Is there a workaround to compile Linux-kernel with any CLANG >>> version? >> >> You could revert the patch that makes asm-goto mandatory. >> >>> You happen to know the status in LLVM upstream? >> >> I know people are actively working on this, but don't know an ETA. >> > > [ CC Dimitry ] > > Sorry for the late response. > This weekend I had some time to play with clang-7 and Linux-4.17-rcN. > > I tried with Linux v4.17-rc3-261-gc1c07416cdd4 and reverted the > mandatory patch [1]. > > commit e501ce957a786ecd076ea0cfb10b114e6e4d0f40 > "x86: Force asm-goto" > > This needed a follow up [2]... > > commit d0266046ad54e0c964941364cd82a0d0478ce286 > "x86: Remove FAST_FEATURE_TESTS" > > ...but breaks my build. > > That seems to be a known issue [3] and Dimitry bisected this to [4]. > Is there a fix for this? > > I have attached my kernel-config and the broken build-log. > > Hope this helps. > > Regards, > - Sedat - > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e501ce957a786ecd076ea0cfb10b114e6e4d0f40 > [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/x86/include/asm/cpufeature.h?id=d0266046ad54e0c964941364cd82a0d0478ce286 > [3] https://www.spinics.net/lists/linux-mm/msg147669.html > [4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8bf705d130396e69c04cd8e6e010244ad2ce71f4 Hi Sedat, Sorry for the breakage. This was reported and discussed here: https://groups.google.com/forum/#!topic/kasan-dev/oMgCP37n1vw The plan is to make clang behave the same way as gcc wrt asm constraint checking. But I don't know what's the progress.
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