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Currently, we base the KASLR randomization range on a rough estimate of the available space in the upper VA region: the lower 1/4th has the module region and the upper 1/4th has the fixmap, vmemmap and PCI I/O ranges, and so we pick a random location in the remaining space in the middle. Once we enable support for 5-level paging with 4k pages, this no longer works: the vmemmap region, being dimensioned to cover a 52-bit linear region, takes up so much space in the upper VA region (the size of which is based on a 48-bit VA space for compatibility with non-LVA hardware) that the region above the vmalloc region takes up more than a quarter of the available space. So instead of a heuristic, let's derive the randomization range from the actual boundaries of the vmalloc region. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20231213084024.2367360-16-ardb@google.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Mark Rutland <mark.rutland@arm.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.