Re: [PATCH][v8] PM / hibernate: Verify the consistent of e820 memory map by md5 value
From: Pavel Machek <hidden>
Date: 2016-08-28 16:37:03
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On Mon 2016-08-29 00:35:40, Chen Yu wrote:
On some platforms, there is occasional panic triggered when trying to resume from hibernation, a typical panic looks like: "BUG: unable to handle kernel paging request at ffff880085894000 IP: [<ffffffff810c5dc2>] load_image_lzo+0x8c2/0xe70" This is because e820 map has been changed by BIOS across hibernation, and one of the page frames from first kernel is right located in second kernel's unmapped region, so panic comes out when accessing unmapped kernel address. In order to expose this issue earlier, the md5 hash of e820 map is passed from suspend kernel to resume kernel, and the system will trigger panic once it finds the md5 value of previous kernel is not the same as current resume kernel. Note: 1. Without this patch applied, it is possible that BIOS has provided an inconsistent memory map, but the resume kernel is still able to restore the image anyway(e.g., E820_RAM region is the subset of the previous one), although the system might be unstable. So this patch tries to treat any inconsistent e820 as illegal. 2. Another case is, this patch replies on comparing the e820_saved, but currently the e820_save might not be strictly the same across hibernation, even if BIOS has provided consistent e820 map - In theory mptable might modify the BIOS-provided e820_saved dynamically in early_reserve_e820_mpc_new, which would allocate a buffer from E820_RAM, and marks it from E820_RAM to E820_RESERVED). This is a potential and rare case we need to deal with in OS in the future. Suggested-by: Pavel Machek <redacted> Suggested-by: Rafael J. Wysocki <redacted> Cc: Lee, Chun-Yi <jlee@suse.com> Cc: Borislav Petkov <bp@alien8.de> Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Acked-by: Pavel Machek <redacted> You might want to verify that panic is actually visible on affected platform. Thanks for your patience ;-). Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html