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If a Cortex-A715 cpu sees a page mapping permissions change from executable to non-executable, it may corrupt the ESR_ELx and FAR_ELx registers, on the next instruction abort caused by permission fault. Only user-space does executable to non-executable permission transition via mprotect() system call which calls ptep_modify_prot_start() and ptep_modify _prot_commit() helpers, while changing the page mapping. The platform code can override these helpers via __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION. Work around the problem via doing a break-before-make TLB invalidation, for all executable user space mappings, that go through mprotect() system call. This overrides ptep_modify_prot_start() and ptep_modify_prot_commit(), via defining HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION on the platform thus giving an opportunity to intercept user space exec mappings, and do the necessary TLB invalidation. Similar interceptions are also implemented for HugeTLB. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Mark Rutland <mark.rutland@arm.com> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Link: https://lore.kernel.org/r/20221116140915.356601-3-anshuman.khandual@arm.com Signed-off-by: Will Deacon <will@kernel.org>
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.