linux-kernel - Re: [PATCH] arm64: link with -z norelro regardless of CONFIG

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Message-ID: <20201214231827.GG8873@bubble.grove.modra.org>
Date:   Tue, 15 Dec 2020 09:48:27 +1030
From:   Alan Modra <amodra@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        kernel-team <kernel-team@...roid.com>,
        Will Deacon <will@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Smith <Peter.Smith@....com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        "# 3.4.x" <stable@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Fāng-ruì Sòng <maskray@...gle.com>,
        Quentin Perret <qperret@...gle.com>
Subject: Re: [PATCH] arm64: link with -z norelro regardless of
 CONFIG_RELOCATABLE

On Mon, Dec 14, 2020 at 01:44:06PM -0800, Nick Desaulniers wrote:
> aarch64-linux-gnu-ld: warning: -z norelro ignored
> 
> So we set the emulation mode via -maarch64elf, and our preprocessed

The default linker emulation for an aarch64-linux ld.bfd is
-maarch64linux, the default for an aarch64-elf linker is
-maarch64elf.  They are not equivalent.  If you choose -maarch64elf
you get an emulation that doesn't support -z relro.

Now I don't know why the kernel uses -maarch64elf so you shouldn't
interpret my comment as a recommendation to use -maarch64linux
instead.  That may have other unwanted effects.

-- 
Alan Modra
Australia Development Lab, IBM