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

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Message-ID: <20191009082920.GM42880@e119886-lin.cambridge.arm.com>
Date:   Wed, 9 Oct 2019 09:29:20 +0100
From:   Andrew Murray <andrew.murray@....com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Sami Tolvanen <samitolvanen@...gle.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 05:01:59PM -0700, Nathan Chancellor wrote:
> 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.

OK, understood. You can add:

Reviewed-by: Andrew Murray <andrew.murray@....com>
Tested-by: Andrew Murray <andrew.murray@....com>

> 
> Cheers,
> Nathan