linux-kernel - Re: [PATCH] arm64/bpf: use movn/movk/movk sequence to generate kernel addresses

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20181127182203.GA19721@arm.com>
Date:   Tue, 27 Nov 2018 18:22:03 +0000
From:   Will Deacon <will.deacon@....com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        catalin.marinas@....com, ast@...com, daniel@...earbox.net
Subject: Re: [PATCH] arm64/bpf: use movn/movk/movk sequence to generate
 kernel addresses

Hi Ard,

On Fri, Nov 23, 2018 at 06:29:02PM +0100, Ard Biesheuvel wrote:
> On arm64, all executable code is guaranteed to reside in the vmalloc
> space (or the module space), and so jump targets will only use 48
> bits at most, and the remaining bits are guaranteed to be 0x1.
> 
> This means we can generate an immediate jump address using a sequence
> of one MOVN (move wide negated) and two MOVK instructions, where the
> first one sets the lower 16 bits but also sets all top bits to 0x1.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> ---

Acked-by: Will Deacon <will.deacon@....com>

Denial, Alexei, shall I take this via arm64, or would you rather take
it via davem?

Cheers,

Will