On Sun, Jul 29, 2018 at 08:12:00PM +0200, Sedat Dilek wrote: > [ TO Mark Rutland ] > > Hi, Hi, > I was able to build a Linux v4.18-rc6 with tip.git#locking/core [1] on > top of it here on Debian/buster AMD64. > > The patch of interest is [2]... > > df79ed2c0643 locking/atomics: Simplify cmpxchg() instrumentation > > ...and some more locking/atomics[/x86] may be interesting. > > I had also to apply an asm-goto fix to reduce the number of warnings > when building with clang-7 (version > 7.0.0-svn337957-1~exp1+0~20180725200907.1908~1.gbpcccb1b (trunk)). Just to be clear, clang 7.0.0 has not been released yet, and this is a trunk build of clang, right? Do any released versions of clang (e.g. 6.0.1) build a working kernel? > CONFIG_DRM_AMDGPU=m is BROKEN and a known issue [3]. > > I had to hack my fakeroot-sysv binary to workaround a fatal build-stop > by commenting the part "nested operation not yet supported" when using > bindeb-pkg make-target. Does upstream build at all with clang, or are you always having to apply a number of modifications? Which config are you using? > The kernel does ***not boot*** on bare metal. Ok. Does the prior commit boot? > More details see [4] and [5] for the clang-side. It's not clear to me how these relate to the patch in question. AFAICT, those are build-time errors, but you say that the kernel doesn't boot (which implies it built). Are [4,5] relevant to this commit, or to the (unrelated) issue [3]? My patch removes the switch, so this doesn't look like the same issue. Thanks, Mark. > > - Sedat - > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/log/?h=locking/core > [2] https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=locking/core&id=df79ed2c064363cdc7d2d896923c1885d4e30520 > [3] https://lists.freedesktop.org/archives/amd-gfx/2018-July/024634.html > [4] https://github.com/ClangBuiltLinux/linux/issues/3 > [5] https://bugs.llvm.org/show_bug.cgi?id=33587 > From 5c3485197eab808768271d72e188ad11b6fcecd4 Mon Sep 17 00:00:00 2001 > From: Sedat Dilek <sedat.dilek@xxxxxxxxxxx> > Date: Fri, 8 Jun 2018 18:23:26 +0200 > Subject: [PATCH] x86: Warn clang does not support asm-goto > > Signed-off-by: Sedat Dilek <sedat.dilek@xxxxxxxxxxx> > --- > arch/x86/Makefile | 2 +- > arch/x86/include/asm/cpufeature.h | 9 +-------- > 2 files changed, 2 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/Makefile b/arch/x86/Makefile > index a08e82856563..6042f6f5a1be 100644 > --- a/arch/x86/Makefile > +++ b/arch/x86/Makefile > @@ -181,7 +181,7 @@ ifdef CONFIG_FUNCTION_GRAPH_TRACER > endif > > ifndef CC_HAVE_ASM_GOTO > - $(error Compiler lacks asm-goto support.) > + $(warning Compiler lacks asm-goto support.) > endif > > # > diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h > index aced6c9290d6..79177f0efdf1 100644 > --- a/arch/x86/include/asm/cpufeature.h > +++ b/arch/x86/include/asm/cpufeature.h > @@ -140,16 +140,9 @@ extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit); > > #define setup_force_cpu_bug(bit) setup_force_cpu_cap(bit) > > +/* Clang does not support asm-goto (see LLVM bug #9295). */ > #if defined(__clang__) && !defined(CC_HAVE_ASM_GOTO) > > -/* > - * Workaround for the sake of BPF compilation which utilizes kernel > - * headers, but clang does not support ASM GOTO and fails the build. > - */ > -#ifndef __BPF_TRACING__ > -#warning "Compiler lacks ASM_GOTO support. Add -D __BPF_TRACING__ to your compiler arguments" > -#endif > - > #define static_cpu_has(bit) boot_cpu_has(bit) > > #else > -- > 2.18.0 >
