linux-kernel - Re: [PATCH] x86/tools: deal with 64-bit relative relocations for per-CPU symbols

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Date:   Fri, 24 May 2019 12:42:24 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Ard Biesheuvel <ard.biesheuvel@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, marc.zyngier@....com,
        james.morse@....com, will.deacon@....com, guillaume.gardet@....com,
        mark.rutland@....com, mingo@...nel.org, jeyu@...nel.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        arnd@...db.de, x86@...nel.org
Subject: Re: [PATCH] x86/tools: deal with 64-bit relative relocations for
 per-CPU symbols

On Wed, May 22, 2019 at 06:40:57PM +0100, Ard Biesheuvel wrote:
> In order to fix an issue in the place relative ksymtab code, we
> need to switch to 64-bit place relative references, which
> require special handling in the x86 'relocs' tool. The reason
> is that per-CPU symbols on x86_64 live in a separate link time
> section, whose load time address is not reflected in the ELF
> metadata, and so relative references emitted by the toolchain
> are guaranteed to be wrong.
> 
> So fix this by extending the handling of 32-bit relative references
> to per-CPU variables to support 64-bit relative references as
> well.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@....com>
> ---
> This is a follow-up to [0] and a prerequisite to the change it
> implements: using 64-bit relative references on x86_64 requires
> this handling in the 'relocs' tool and in the decompressor.
> 
> [0] https://lore.kernel.org/linux-arm-kernel/20190522150239.19314-1-ard.biesheuvel@arm.com
> 
> This patch plus [0] build and boot tested with x86_64_defconfig on QEMU/kvm + OVMF.

NACK based on

https://lkml.kernel.org/r/f2141ee5-d07a-6dd9-47c6-97e8fbdccf34@arm.com

-- 
Josh