linux-kernel - Re: [PATCH v2] arm64, kaslr: export offset in VMCOREINFO ELF notes

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Message-ID: <20180731092629.GD4680@arm.com>
Date:   Tue, 31 Jul 2018 10:26:29 +0100
From:   Will Deacon <will.deacon@....com>
To:     James Morse <james.morse@....com>
Cc:     Bhupesh Sharma <bhsharma@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kexec@...ts.infradead.org, bhupesh.linux@...il.com,
        takahiro.akashi@...aro.org, catalin.marinas@....com,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2] arm64, kaslr: export offset in VMCOREINFO ELF notes

On Tue, Jul 31, 2018 at 10:19:35AM +0100, James Morse wrote:
> Hi Bhupesh,
> 
> On 30/07/18 07:24, Bhupesh Sharma wrote:
> > Include KASLR offset in arm64 VMCOREINFO ELF notes to assist in
> > debugging. vmcore parsing in user-space already expects this value in
> > the notes and we are providing it for portability of those existing
> > tools with x86.
> > 
> > Ideally we would like core code to do this (so that way this
> > information won't be missed when an architecture adds KASLR support),
> > but mips has CONFIG_RANDOMIZE_BASE, and doesn't provide kaslr_offset(),
> > so I am not sure if this is needed for mips (and other such similar arch
> > cases in future). So, lets keep this architecture specific for now.
> 
> (heh, I assumed you would rewrite my train-of-thought, but I guess this works!)
> 
> 
> > As an example of a user-space use-case, consider the
> > makedumpfile user-space utility which will need fixup to use this
> > KASLR offset to work with cases where we need to find a way to
> > translate symbol address from vmlinux to kernel run time address
> > in case of KASLR boot on arm64.
> 
> Acked-by: James Morse <james.morse@....com>
> 
> If we want to send this to stable, it looks like it should have been part of the
> KASLR series, f80fb3a3d5084 ("arm64: add support for kernel ASLR") was merged
> for v4.6.
> CC: <stable@...r.kernel.org> # 4.6.x

Hmm, does this warrant a stable backport? This hasn't ever worked, right?

Will