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876320d71f
Utilise the kselftest harmness to implement tests for the guard page implementation. We start by implement basic tests asserting that guard pages can be installed, removed and that touching guard pages result in SIGSEGV. We also assert that, in removing guard pages from a range, non-guard pages remain intact. We then examine different operations on regions containing guard markers behave to ensure correct behaviour: * Operations over multiple VMAs operate as expected. * Invoking MADV_GUARD_INSTALL / MADV_GUARD_REMOVE via process_madvise() in batches works correctly. * Ensuring that munmap() correctly tears down guard markers. * Using mprotect() to adjust protection bits does not in any way override or cause issues with guard markers. * Ensuring that splitting and merging VMAs around guard markers causes no issue - i.e. that a marker which 'belongs' to one VMA can function just as well 'belonging' to another. * Ensuring that madvise(..., MADV_DONTNEED) and madvise(..., MADV_FREE) do not remove guard markers. * Ensuring that mlock()'ing a range containing guard markers does not cause issues. * Ensuring that mremap() can move a guard range and retain guard markers. * Ensuring that mremap() can expand a guard range and retain guard markers (perhaps moving the range). * Ensuring that mremap() can shrink a guard range and retain guard markers. * Ensuring that forking a process correctly retains guard markers. * Ensuring that forking a VMA with VM_WIPEONFORK set behaves sanely. * Ensuring that lazyfree simply clears guard markers. * Ensuring that userfaultfd can co-exist with guard pages. * Ensuring that madvise(..., MADV_POPULATE_READ) and madvise(..., MADV_POPULATE_WRITE) error out when encountering guard markers. * Ensuring that madvise(..., MADV_COLD) and madvise(..., MADV_PAGEOUT) do not remove guard markers. If any test is unable to be run due to lack of permissions, that test is skipped. Link: https://lkml.kernel.org/r/c3dcca76b736bac0aeaf1dc085927536a253ac94.1730123433.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Shuah Khan <skhan@linuxfoundation.org> Suggested-by: Vlastimil Babka <vbabka@suse.cz> Suggested-by: Jann Horn <jannh@google.com> Suggested-by: David Hildenbrand <david@redhat.com> Cc: Arnd Bergmann <arnd@kernel.org> Cc: Christian Brauner <brauner@kernel.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Chris Zankel <chris@zankel.net> Cc: Helge Deller <deller@gmx.de> Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com> Cc: Jeff Xu <jeffxu@chromium.org> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Liam R. Howlett <Liam.Howlett@Oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Matt Turner <mattst88@gmail.com> Cc: Max Filippov <jcmvbkbc@gmail.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Richard Henderson <richard.henderson@linaro.org> Cc: Shuah Khan <shuah@kernel.org> Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: Vlastimil Babka <vbabkba@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.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 reStructuredText 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.