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Subject[PATCH v3 0/4] arm64: ARMv8.5-A: MTE: Add async mode support
This patchset implements the asynchronous mode support for ARMv8.5-A
Memory Tagging Extension (MTE), which is a debugging feature that allows
to detect with the help of the architecture the C and C++ programmatic
memory errors like buffer overflow, use-after-free, use-after-return, etc.

MTE is built on top of the AArch64 v8.0 virtual address tagging TBI
(Top Byte Ignore) feature and allows a task to set a 4 bit tag on any
subset of its address space that is multiple of a 16 bytes granule. MTE
is based on a lock-key mechanism where the lock is the tag associated to
the physical memory and the key is the tag associated to the virtual
When MTE is enabled and tags are set for ranges of address space of a task,
the PE will compare the tag related to the physical memory with the tag
related to the virtual address (tag check operation). Access to the memory
is granted only if the two tags match. In case of mismatch the PE will raise
an exception.

The exception can be handled synchronously or asynchronously. When the
asynchronous mode is enabled:
- Upon fault the PE updates the TFSR_EL1 register.
- The kernel detects the change during one of the following:
- Context switching
- Return to user/EL0
- Kernel entry from EL1
- Kernel exit to EL1
- If the register has been updated by the PE the kernel clears it and
reports the error.

The series contains as well an optimization to mte_assign_mem_tag_range().

The series is based on linux 5.11-rc3.

To simplify the testing a tree with the new patches on top has been made
available at [1].

[1] mte/v10.async

- Exposed kasan_hw_tags_mode to convert the internal
KASAN represenetation.
- Added dsb() for kernel exit paths in arm64.
- Addressed review comments.
- Fixed a compilation issue reported by krobot.
- General cleanup.

Cc: Catalin Marinas <>
Cc: Will Deacon <>
Cc: Dmitry Vyukov <>
Cc: Andrey Ryabinin <>
Cc: Alexander Potapenko <>
Cc: Marco Elver <>
Cc: Evgenii Stepanov <>
Cc: Branislav Rankov <>
Cc: Andrey Konovalov <>
Signed-off-by: Vincenzo Frascino <>
Vincenzo Frascino (4):
kasan, arm64: Add KASAN light mode
arm64: mte: Add asynchronous mode support
arm64: mte: Enable async tag check fault
arm64: mte: Optimize mte_assign_mem_tag_range()

arch/arm64/include/asm/memory.h | 2 +-
arch/arm64/include/asm/mte-kasan.h | 5 ++-
arch/arm64/include/asm/mte.h | 47 +++++++++++++++++++++-
arch/arm64/kernel/entry-common.c | 11 ++++++
arch/arm64/kernel/mte.c | 63 ++++++++++++++++++++++++++++--
arch/arm64/lib/mte.S | 15 -------
include/linux/kasan.h | 1 +
include/linux/kasan_def.h | 10 +++++
mm/kasan/hw_tags.c | 19 ++++++++-
mm/kasan/kasan.h | 2 +-
10 files changed, 151 insertions(+), 24 deletions(-)
create mode 100644 include/linux/kasan_def.h


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