From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Fri, 18 Aug 2017 16:22:58 +0100 Subject: [PATCH] arm64: kaslr: Adjust the offset to avoid Image across alignment boundary In-Reply-To: References: <20170818150435.35224-1-catalin.marinas@arm.com> <20170818151920.jpugpcgwiavgwgaf@armageddon.cambridge.arm.com> Message-ID: <20170818152257.dbllbeuxwm5nugno@armageddon.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Aug 18, 2017 at 04:20:16PM +0100, Ard Biesheuvel wrote: > On 18 August 2017 at 16:19, Catalin Marinas wrote: > > On Fri, Aug 18, 2017 at 04:04:34PM +0100, Catalin Marinas wrote: > >> With 16KB pages and a kernel Image larger than 16MB, the current > >> kaslr_early_init() logic for avoiding mappings across swapper table > >> boundaries fails since increasing the offset by kimg_sz just moves the > >> problem to the next boundary. > >> > >> This patch decreases the offset by the boundary overflow amount, with > >> slight risk of reduced entropy as the kernel is more likely to be found > >> at kimg_sz below a swapper table boundary. > >> > >> Trying-to-fix: afd0e5a87670 ("arm64: kaslr: Fix up the kernel image alignment") > >> Cc: Ard Biesheuvel > >> Cc: Mark Rutland > >> Cc: Will Deacon > >> Cc: Neeraj Upadhyay > >> Signed-off-by: Catalin Marinas > >> --- > >> > >> While preparing this email, I noticed that the kernel eventually failed > >> to boot, though after a lot more reboot iterations. Mark Rutland also > >> managed to make the KASLR kernel fail to boot with 64K pages which > >> wouldn't be explained by this patch. > >> > >> So, any suggestions are welcome. My testing method, qemu starting a > >> guest in a loop with virtio-rng-pci. > > > > Apparently, the booting gets much more stable if I disable the physical > > relocation in arm64-stub.c (but keep the virtual one with the fix in > > this patch). So I guess we are chasing two different issues. > > So this is using QEMU with 16k pages support? Qemu running on a ThunderX, so native KVM support. -- Catalin