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Peter Anvin" , "Kirill A. Shutemov" , Baoquan He , Chao Fan , x86@kernel.org Subject: [PATCH 0/3] x86/boot/KASLR: enhance randomness of kernel load addr when using GiB hugepage Date: Thu, 6 Sep 2018 10:36:19 +0800 Message-Id: <1536201382-13133-1-git-send-email-kernelfans@gmail.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org commit 747ff6265db4 ("x86/boot/KASLR: Skip specified number of 1GB huge pages when doing physical randomization (KASLR)") and commit 9b912485e0e7 ("x86/boot/KASLR: Add two new functions for 1GB huge pages handling") prevent the physical load addr of kernel from spoiling a good candidate of GiB page. But the algorithm deterministicly chooses the most front GiB page for hugetlb, and sacrifices the randomness, which is the heart of the KASLR. This patch tries to enlarge the randomness in the cases where hugepages=X < the num Y of good candidate of GiB page. To comparison, taking a typical KVM guest for example, the head 3GiB mem can not be used as GiB hugetlb. Denoting the total mem size as Z(GiB), when Z=5, then Y=2, assuming X=1, the randomness range before this patch is 4GiB, after this patch is 5GiB, and get a 25% improvement of randomness. If Z=6, then Y=3, assuming X=2, the improvement equals: 50%( 6/(6-2) - 1); assuming X=1, the improvement will be: 20% (6/(6-1) - 1) Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: "Kirill A. Shutemov" Cc: Baoquan He Cc: Chao Fan (authored:1/16=6%) Cc: x86@kernel.org Pingfan Liu (3): x86/boot/KASLR: change the prototypes of process_efi_entries/process_e820_entries x86/boot/KASLR: change the prototype of process_mem_region() to meet the align requirement x86/boot/KASLR: enhance randomness when using GiB hugepage arch/x86/boot/compressed/kaslr.c | 228 ++++++++++++++++++++++++++------------- 1 file changed, 152 insertions(+), 76 deletions(-) -- 2.7.4