linux-kernel - Re: [PATCH v3] arm64: sysreg: make mrs_s and msr

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Message-ID: <20190416170808.GC54708@lakrids.cambridge.arm.com>
Date:   Tue, 16 Apr 2019 18:08:09 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Alex Matveev <alxmtvv@...il.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Yury Norov <ynorov@...iumnetworks.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] arm64: sysreg: make mrs_s and msr_s macros work with
 Clang and LTO

On Mon, Apr 15, 2019 at 10:22:27AM -0700, Nick Desaulniers wrote:
> On Mon, Apr 15, 2019 at 10:06 AM Mark Rutland <mark.rutland@....com> wrote:
> > It would be nice if we could simply rely on a more recent binutils these
> > days, which supports the generic S<op0>_<op1>_<cn>_<Cm>_<op2> sysreg
> > definition. That would mean we could get rid of the whole msr_s/mrs_s
> > hack by turning that into a CPP macro which built that name.
> >
> > It looks like binutils has been able to do that since September 2014...
> >
> > Are folk using toolchains older than that to compile kernels?
> 
> Do you have a link to a commit?  If we can pinpoint the binutils
> version, that might help.

IIUC any version of binutils with commit:

  df7b4545b2b49572 ("[PATCH/AArch64] Generic support for all system registers using mrs and msr")

... should be sufficent.

That's on gitweb at:

  https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=df7b4545b2b49572ab63690c130df973af109615

> Also, I look forward to this patch for use of Clang's integrated
> assembler (regardless of LTO).  I remember getting frustrated trying
> to figure out how to resolve this for both assemblers, and I had
> forgotten this solution existed.

Is this the only blocker for the integrated assembler?

Thanks,
Mark.