Date: Wed, 09 Oct 2013 07:13:26 -0700 From: "H. Peter Anvin" <hpa@...or.com> To: HATAYAMA Daisuke <d.hatayama@...fujitsu.com> CC: Dave Anderson <anderson@...hat.com>, Kees Cook <keescook@...omium.org>, LKML <linux-kernel@...r.kernel.org>, x86@...nel.org, kernel-hardening@...ts.openwall.com, Aaron Durbin <adurbin@...gle.com>, Eric Northup <digitaleric@...gle.com>, Julien Tinnes <jln@...gle.com>, Will Drewry <wad@...gle.com>, Mathias Krause <minipli@...glemail.com>, Zhang Yanfei <zhangyanfei@...fujitsu.com>, "Discussion list for crash utility usage, maintenance and development" <crash-utility@...hat.com> Subject: Re: [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
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