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Date: Sun, 6 May 2018 09:58:04 +0200 From: Sedat Dilek <sedat.dilek@...il.com> To: Dmitry Vyukov <dvyukov@...gle.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 9:41 AM, Dmitry Vyukov <dvyukov@...gle.com> wrote: > 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. Hi Dimitry, that's the thread I looked into and also looked into the involved commits and appropriate files in the linux-source without knowing of [1]. Just just for the records... I used the kernel-config of Debian's linux-image-4.17.0-rc3-amd64-unsigned (4.17~rc3-1~exp1) as a base with this modification: $ cd /path/to/linux-source $ LINUX_CONFIG="./.config" $ scripts/config --file $LINUX_CONFIG --disable X86_X32 ...and... # CONFIG_KASAN is not set ...if this matters. Kind regards, - Sedat - [1] https://bugs.llvm.org/show_bug.cgi?id=33587 [2] https://packages.debian.org/experimental/linux-image-4.17.0-rc3-amd64-unsigned
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