arm64: mm: permit use of tagged pointers at EL0

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TCR.TBI0 can be used to cause hardware address translation to ignore the
top byte of userspace virtual addresses. Whilst not especially useful in
standard C programs, this can be used by JITs to `tag' pointers with
various pieces of metadata.

This patch enables this bit for AArch64 Linux, and adds a new file to
Documentation/arm64/ which describes some potential caveats when using
tagged virtual addresses.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

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Will Deacon 2013-06-12 16:28:04 +01:00 • committed by Catalin Marinas

parent 909e3ee411

commit d50240a5f6

4 changed files with 37 additions and 1 deletions

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34

Documentation/arm64/tagged-pointers.txt

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1

arch/arm64/include/asm/pgtable-hwdef.h

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1

arch/arm64/kernel/entry.S

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2

arch/arm64/mm/proc.S

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