linux-kernel - Re: [PATCH] arm64: kaslr: print PHYS_OFFSET in dump_kernel

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Message-ID: <20181213181317.GD18185@edgewater-inn.cambridge.arm.com>
Date:   Thu, 13 Dec 2018 18:13:18 +0000
From:   Will Deacon <will.deacon@....com>
To:     Miles Chen <miles.chen@...iatek.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, wsd_upstream@...iatek.com,
        ard.biesheuvel@...aro.org
Subject: Re: [PATCH] arm64: kaslr: print PHYS_OFFSET in dump_kernel_offset()

[+Ard because I'll basically go with his preference on this one]

On Wed, Dec 12, 2018 at 06:56:49PM +0800, Miles Chen wrote:
> When debug with kaslr, it is sometimes necessary to have PHYS_OFFSET to
> perform linear virtual address to physical address translation.
> Sometimes we're debugging with only few information such as a kernel log
> and a symbol file, print PHYS_OFFSET in dump_kernel_offset() for that case.
> 
> Tested by:
> echo c > /proc/sysrq-trigger
> [   11.996161] SMP: stopping secondary CPUs
> [   11.996732] Kernel Offset: 0x2522200000 from 0xffffff8008000000
> [   11.996881] PHYS_OFFSET: 0xffffffeb40000000
> 
> Signed-off-by: Miles Chen <miles.chen@...iatek.com>
> Tested-by: Miles Chen <miles.chen@...iatek.com>
> ---
>  arch/arm64/kernel/setup.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index f4fc1e0544b7..4b0e1231625c 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -388,6 +388,7 @@ static int dump_kernel_offset(struct notifier_block *self, unsigned long v,
>  	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && offset > 0) {
>  		pr_emerg("Kernel Offset: 0x%lx from 0x%lx\n",
>  			 offset, KIMAGE_VADDR);
> +		pr_emerg("PHYS_OFFSET: 0x%llx\n", PHYS_OFFSET);
>  	} else {
>  		pr_emerg("Kernel Offset: disabled\n");
>  	}
> -- 
> 2.18.0
>