linux-kernel - Re: [PATCH v2] arm64: lse: fix LSE atomics with LLVM's integrated assembler

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Date:   Tue, 8 Oct 2019 17:01:59 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Andrew Murray <andrew.murray@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH v2] arm64: lse: fix LSE atomics with LLVM's integrated
 assembler

On Tue, Oct 08, 2019 at 04:59:25PM -0700, 'Sami Tolvanen' via Clang Built Linux wrote:
> On Tue, Oct 8, 2019 at 4:31 PM Andrew Murray <andrew.murray@....com> wrote:
> > This looks good to me. I can build and boot in a model with both Clang
> > (9.0.6) and GCC (7.3.1) and boot a guest without anything going bang.
> 
> Great, thank you for testing this!
> 
> > Though when I build with AS=clang, e.g.
> >
> > make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- CC=clang AS=clang Image
> 
> Note that this patch only fixes issues with inline assembly, which
> should at some point allow us to drop -no-integrated-as from clang
> builds. I believe there are still other fixes needed before AS=clang
> works.
> 
> > I get errors like this:
> >
> >   CC      init/main.o
> > In file included from init/main.c:17:
> > In file included from ./include/linux/module.h:9:
> > In file included from ./include/linux/list.h:9:
> > In file included from ./include/linux/kernel.h:12:
> > In file included from ./include/linux/bitops.h:26:
> > In file included from ./arch/arm64/include/asm/bitops.h:26:
> > In file included from ./include/asm-generic/bitops/atomic.h:5:
> > In file included from ./include/linux/atomic.h:7:
> > In file included from ./arch/arm64/include/asm/atomic.h:16:
> > In file included from ./arch/arm64/include/asm/cmpxchg.h:14:
> > In file included from ./arch/arm64/include/asm/lse.h:13:
> > In file included from ./include/linux/jump_label.h:117:
> > ./arch/arm64/include/asm/jump_label.h:24:20: error: expected a symbol reference in '.long' directive
> >                  "      .align          3                       \n\t"
> >                                                                   ^
> > <inline asm>:4:21: note: instantiated into assembly here
> >                 .long           1b - ., "" - .
> >                                            ^
> >
> > I'm assuming that I'm doing something wrong?
> 
> No, this particular issue will be fixed in clang 10:
> https://github.com/ClangBuiltLinux/linux/issues/500
> 
> Sami

I believe that it should be fixed with AOSP's Clang 9.0.8 or upstream
Clang 9.0.0.

Cheers,
Nathan