linux-kernel - Re: [PATCH] arm64: alternatives: Move length validation in alternative

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Date:   Thu, 15 Apr 2021 08:50:25 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Will Deacon <will@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Jian Cai <jiancai@...gle.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        "# 3.4.x" <stable@...r.kernel.org>
Subject: Re: [PATCH] arm64: alternatives: Move length validation in alternative_{insn,endif}

On Thu, Apr 15, 2021 at 7:02 AM Catalin Marinas <catalin.marinas@....com> wrote:
>
> On Thu, Apr 15, 2021 at 06:25:57AM -0700, Nathan Chancellor wrote:
> > On Thu, Apr 15, 2021 at 10:17:43AM +0100, Catalin Marinas wrote:
> > > On Tue, Apr 13, 2021 at 05:08:04PM -0700, Nathan Chancellor wrote:
> > > > After commit 2decad92f473 ("arm64: mte: Ensure TIF_MTE_ASYNC_FAULT is
> > > > set atomically"), LLVM's integrated assembler fails to build entry.S:
> > > >
> > > > <instantiation>:5:7: error: expected assembly-time absolute expression
> > > >  .org . - (664b-663b) + (662b-661b)
> > > >       ^
> > > > <instantiation>:6:7: error: expected assembly-time absolute expression
> > > >  .org . - (662b-661b) + (664b-663b)
> > > >       ^
> > >
> > > I tried the latest Linus' tree and linux-next (defconfig) with this
> > > commit in and I can't get your build error. I used both clang-10 from
> > > Debian stable and clang-11 from Debian sid. So, which clang version did
> > > you use or which kernel config options?
> >
> > Interesting, this reproduces for me with LLVM 12 or newer with just
> > defconfig.
>
> It fails for me as well with clang-12. Do you happen to know why it
> works fine with previous clang versions?

It looks like CONFIG_ARM64_AS_HAS_MTE is not set when we use the
integrated assembler with LLVM 11, and the code that breaks later
versions is gated behind CONFIG_ARM64_MTE.

Sami