Re: [Crash-utility] [PATCH 6/7] x86, kaslr: report kernel offset on panic
On 10/09/2013 03:04 AM, HATAYAMA Daisuke wrote:
>>
>> Sorry, I don't understand why relocation size cannot be calculated when
>> CONFIG_PHYSICALSTART > CONFIG_PHYSICAL_ALIGN. Could you explain that?
>
> I just meant that when CONFIG_PHYSICAL_START > CONFIG_PHYSICAL_ALIGN,
> the 32-bit x86 kernel
> gets relocated (like the secondary kdump kernel), but that information
> is not readily available
> from the vmlinux/vmcore pair.
>
My understanding on CONFIG_PHYSICAL_ALIGN was that starting address of
kernel text area
is always rounded up to CONFIG_PHYSICAL_ALIGN, only. Your explanation
would be part I don't
understand well. I'll reconsider it locally...
If CONFIG_PHYSICAL_START == CONFIG_PHYSICAL_ALIGN, then it is very
likely that the kernel (in the absence of kASLR) will be run at the
CONFIG_PHYSICAL_START address, as the initial loading address, usually 1
MB, will be rounded up to CONFIG_PHYSICAL_ALIGN.
Since CONFIG_PHYSICAL_START is the unrelocated linking address, they end
up matching.
-hpa