selftests/mm: add fork CoW guard page test

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When we fork anonymous pages, apply a guard page then remove it, the
previous CoW mapping is cleared.

This might not be obvious to an outside observer without taking some time
to think about how the overall process functions, so document that this is
the case through a test, which also usefully asserts that the behaviour is
as we expect.

This is grouped with other, more important, fork tests that ensure that
guard pages are correctly propagated on fork.

Fix a typo in a nearby comment at the same time.

[ryan.roberts@arm.com: static process_madvise() wrapper for guard-pages]
  Link: https://lkml.kernel.org/r/20250107142937.1870478-1-ryan.roberts@arm.com
Link: https://lkml.kernel.org/r/20241205190748.115656-1-lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

...

This commit is contained in:

Lorenzo Stoakes 2024-12-05 19:07:48 +00:00 • committed by Andrew Morton

parent 67c8b11bd5

commit 19b65ffae9

2 changed files with 85 additions and 3 deletions

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83

tools/testing/selftests/mm/guard-pages.c

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5

tools/testing/selftests/mm/run_vmtests.sh

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