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KASLR uses hack to detect whether we booted via startup_32() or startup_64(): it checks what is loaded into cr3 and compares it to _pgtables. _pgtables is the array of page tables where early code allocates page table from. KASLR expects cr3 to point to _pgtables if we booted via startup_32(), but that's not true if we booted with 5-level paging enabled. In this case top level page table is allocated separately and only the first p4d page table is allocated from the array. Let's modify the check to cover both 4- and 5-level paging cases. The patch also renames 'level4p' to 'top_level_pgt' as it now can hold page table for 4th or 5th level, depending on configuration. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-arch@vger.kernel.org Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20170628121730.43079-1-kirill.shutemov@linux.intel.com 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.