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Currently KASLR will parse all e820 entries of RAM type and add all candidate positions into the slots array. After that we choose one slot randomly as the new position which the kernel will be decompressed into and run at. On systems with EFI enabled, e820 memory regions are coming from EFI memory regions by combining adjacent regions. These EFI memory regions have various attributes, and the "mirrored" attribute is one of them. The physical memory region whose descriptors in EFI memory map has EFI_MEMORY_MORE_RELIABLE attribute (bit: 16) are mirrored. The address range mirroring feature of the kernel arranges such mirrored regions into normal zones and other regions into movable zones. With the mirroring feature enabled, the code and data of the kernel can only be located in the more reliable mirrored regions. However, the current KASLR code doesn't check EFI memory entries, and could choose a new kernel position in non-mirrored regions. This will break the intended functionality of the address range mirroring feature. To fix this, if EFI is detected, iterate EFI memory map and pick the mirrored region to process for adding candidate of randomization slot. If EFI is disabled or no mirrored region found, still process the e820 memory map. Signed-off-by: Baoquan He <bhe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: ard.biesheuvel@linaro.org Cc: fanc.fnst@cn.fujitsu.com Cc: izumi.taku@jp.fujitsu.com Cc: keescook@chromium.org Cc: linux-efi@vger.kernel.org Cc: matt@codeblueprint.co.uk Cc: n-horiguchi@ah.jp.nec.com Cc: thgarnie@google.com Link: http://lkml.kernel.org/r/1502722464-20614-3-git-send-email-bhe@redhat.com [ Rewrote most of the text. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.