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This reverts commit 0bfc445dec9dd8130d22c9f4476eed7598524129. When we change the permissions of regions mapped using contiguous entries, the architecture requires us to follow a Break-Before-Make strategy, breaking *all* associated entries before we can change any of the following properties from the entries: - presence of the contiguous bit - output address - attributes - permissiones Failure to do so can result in a number of problems (e.g. TLB conflict aborts and/or erroneous results from TLB lookups). See ARM DDI 0487A.k_iss10775, "Misprogramming of the Contiguous bit", page D4-1762. We do not take this into account when altering the permissions of kernel segments in mark_rodata_ro(), where we change the permissions of live contiguous entires one-by-one, leaving them transiently inconsistent. This has been observed to result in failures on some fast model configurations. Unfortunately, we cannot follow Break-Before-Make here as we'd have to unmap kernel text and data used to perform the sequence. For the timebeing, revert commit 0bfc445dec9dd813 so as to avoid issues resulting from this misuse of the contiguous bit. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reported-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <Will.Deacon@arm.com> Cc: stable@vger.kernel.org # v4.10 Signed-off-by: Will Deacon <will.deacon@arm.com>
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.