linux-kernel - Re: [RFC v5 00/57] objtool: Add support for arm64

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Date:   Tue, 21 Jan 2020 10:30:26 +0000
From:   Will Deacon <will@...nel.org>
To:     Julien Thierry <jthierry@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        jpoimboe@...hat.com, peterz@...radead.org, raphael.gault@....com,
        catalin.marinas@....com
Subject: Re: [RFC v5 00/57] objtool: Add support for arm64

On Thu, Jan 09, 2020 at 04:02:03PM +0000, Julien Thierry wrote:
> This patch series is the continuation of Raphael's work [1]. All the
> patches can be retrieved from:
> git clone -b arm64-objtool-v5 https://github.com/julien-thierry/linux.git

[...]

>   objtool: arm64: Decode unknown instructions
>   objtool: arm64: Decode simple data processing instructions
>   objtool: arm64: Decode add/sub immediate instructions
>   objtool: arm64: Decode logical data processing instructions
>   objtool: arm64: Decode system instructions not affecting the flow
>   objtool: arm64: Decode calls to higher EL
>   objtool: arm64: Decode brk instruction
>   objtool: arm64: Decode instruction triggering context switch
>   objtool: arm64: Decode branch instructions with PC relative immediates
>   objtool: arm64: Decode branch to register instruction
>   objtool: arm64: Decode basic load/stores
>   objtool: arm64: Decode load/store with register offset
>   objtool: arm64: Decode load/store register pair instructions
>   objtool: arm64: Decode FP/SIMD load/store instructions
>   objtool: arm64: Decode load/store exclusive
>   objtool: arm64: Decode atomic load/store
>   objtool: arm64: Decode pointer auth load instructions
>   objtool: arm64: Decode load acquire/store release
>   objtool: arm64: Decode load/store with memory tag
>   objtool: arm64: Decode load literal
>   objtool: arm64: Decode register data processing instructions
>   objtool: arm64: Decode FP/SIMD data processing instructions
>   objtool: arm64: Decode SVE instructions

That's a lot of decoding logic which we already have in
arch/arm64/{kernel/insn.c,include/asm/insn.h}. I'd prefer to see this stuff
reused or generated from a single source, since it's really easy to get it
wrong, has a tendency to bitrot and is nasty to debug.

Will