Re: [PATCH 6/6] x86: kaslr: report kernel offset on panic

[Borislav Petkov <bp@alien8.de>]

On Fri, Apr 26, 2013 at 12:03:25PM -0700, Kees Cook wrote:
> When the system panics, include the kernel offset in the report to assist
> in debugging.
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/x86/kernel/setup.c |   24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index fae9134..95a33b1 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -830,6 +830,18 @@ static void __init trim_low_memory_range(void)
>  }
>  	
>  /*
> + * Dump out kernel offset information on panic.
> + */
> +static int
> +dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p)
> +{
> +	pr_emerg("Kernel Offset: 0x%lx\n",
> +		 (unsigned long)&_text - __START_KERNEL);

So what's wrong with subtracting the offset from the function addresses
on the stack so that traces can show the addresses as they are in
vmlinux, completely agnostic of any randomization?

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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