Messages in this thread | | | Date | Wed, 09 Oct 2013 07:13:26 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 6/7] x86, kaslr: report kernel offset on panic |
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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
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