Commit 75516c75 authored Apr 23, 2021 by Catalin Marinas

arm64: doc: Add brk/mmap/mremap() to the Tagged Address ABI Exceptions



Prior to commit dcde2373 ("mm: Avoid creating virtual address
aliases in brk()/mmap()/mremap()"), the kernel allowed tagged addresses
to be passed to the brk/mmap/mremap() syscalls. This relaxation was
tightened in 5.6 (backported to stable 5.4) but the
tagged-address-abi.rst document was only partially updated.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Fixes: dcde2373 ("mm: Avoid creating virtual address aliases in brk()/mmap()/mremap()")
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lore.kernel.org/r/20210423175134.14838-1-catalin.marinas@arm.com


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent 9b924f4f

Documentation/arm64/tagged-address-abi.rst

+6 −0

Original line number	Diff line number	Diff line
		@@ -113,6 +113,12 @@ ABI relaxation:

		- ``shmat()`` and ``shmdt()``.

		- ``brk()`` (since kernel v5.6).

		- ``mmap()`` (since kernel v5.6).

		- ``mremap()``, the ``new_address`` argument (since kernel v5.6).

		Any attempt to use non-zero tagged pointers may result in an error code
		being returned, a (fatal) signal being raised, or other modes of
		failure.