Hi,
This is the second version (first version here [1]) of the series
proposing the user-space support for the ARMv8.5 Memory Tagging
Extension ([2], [3]). The patches are also available on this branch:
git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux devel/mte-v2
Changes in this version:
- HWCAP2_MTE moved to bit 18.
- Changed the polarity of the tag exclusion mask passed to prctl() for
setting the GCR_EL1.Excl field. It is now an include mask, defaulting
to 0 (no tag generated by IRG by default).
- Dropped #ifdef __aarch64__ in the generic siginfo.h, renumbered
SEGV_MTE* after the SEGV_ADI* macros.
- Following an architecture update/fix, accesses to user memory done by
the kernel now use the user-selected tag checking mode
(SCTLR_EL1.TCF0). This required clearing the PSTATE.TCO on the kernel
exception entry and setting the TIF_MTE_ASYNC_FAULT on context switch
if any uaccess routine generated an asynchronous tag check fault.
- For asynchronous faults in user space, a SIGSEGV is now delivered
before processing the syscall (using -ERESTARTNOINTR).
- Moved the MTE-related code from arch/arm64/kernel/process.c to mte.c.
- Documentation updated following the above ABI changes.
- Some of the preparatory or clean-up patches have been merged (as-instr
support in Kconfig files, prot flags 0x10 and 0x20 reserved in the
generic file, MAIR_EL1 setting cleanup).
- Some small fixes and clean-ups following review.
While there are still missing bits, I'm posting a v2 to continue the
discussion with the libc folk on the main ABI aspects. Additional
features will be posted in due course:
- ptrace() support to be able to access the tags in memory of a
different process, something like PTRACE_{PEEK,POKE}MTETAGS. Under
development.
- Swap support, currently under development.
- Related to the above is suspend to disk.
- DT and ACPI description on whether the SoC support MTE (CPUID checking
is insufficient).
- coredump (user) currently does not contain the tags.
- kselftests, under development.
- Clarify whether mmap(tagged_addr, PROT_MTE) pre-tags the memory with
the tag given in the tagged_addr hint. Following commit ce18d171cb73
("mm: untag user pointers in mmap/munmap/mremap/brk"), mmap() no
longer accepts tagged hint addresses. This could be relaxed only when
PROT_MTE is passed, however a deeper investigation is needed on
whether we can still keep the zero page on arm64 for mappings that do
not require pre-tagging.
[1] https://lore.kernel.org/linux-arm-kernel/20191211184027.20130-1-catalin.marinas@xxxxxxx/
[2] https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/posts/enhancing-memory-safety
[3] https://developer.arm.com/-/media/Arm%20Developer%20Community/PDF/Arm_Memory_Tagging_Extension_Whitepaper.pdf
Catalin Marinas (10):
arm64: alternative: Allow alternative_insn to always issue the first
instruction
arm64: mte: Use Normal Tagged attributes for the linear map
arm64: mte: Assembler macros and default architecture for .S files
arm64: Tags-aware memcmp_pages() implementation
arm64: mte: Add PROT_MTE support to mmap() and mprotect()
mm: Introduce arch_validate_flags()
arm64: mte: Validate the PROT_MTE request via arch_validate_flags()
mm: Allow arm64 mmap(PROT_MTE) on RAM-based files
arm64: mte: Allow user control of the tag check mode via prctl()
arm64: mte: Allow user control of the generated random tags via
prctl()
Kevin Brodsky (1):
mm: Introduce arch_calc_vm_flag_bits()
Vincenzo Frascino (8):
arm64: mte: system register definitions
arm64: mte: CPU feature detection and initial sysreg configuration
arm64: mte: Tags-aware clear_page() implementation
arm64: mte: Tags-aware copy_page() implementation
arm64: mte: Add specific SIGSEGV codes
arm64: mte: Handle synchronous and asynchronous tag check faults
arm64: mte: Kconfig entry
arm64: mte: Add Memory Tagging Extension documentation
Documentation/arm64/cpu-feature-registers.rst | 2 +
Documentation/arm64/elf_hwcaps.rst | 5 +
Documentation/arm64/index.rst | 1 +
.../arm64/memory-tagging-extension.rst | 228 ++++++++++++++++++
arch/arm64/Kconfig | 32 +++
arch/arm64/include/asm/alternative.h | 8 +-
arch/arm64/include/asm/assembler.h | 17 ++
arch/arm64/include/asm/cpucaps.h | 4 +-
arch/arm64/include/asm/cpufeature.h | 6 +
arch/arm64/include/asm/hwcap.h | 1 +
arch/arm64/include/asm/kvm_arm.h | 3 +-
arch/arm64/include/asm/memory.h | 17 +-
arch/arm64/include/asm/mman.h | 78 ++++++
arch/arm64/include/asm/mte.h | 35 +++
arch/arm64/include/asm/page.h | 4 +-
arch/arm64/include/asm/pgtable-prot.h | 2 +
arch/arm64/include/asm/pgtable.h | 7 +-
arch/arm64/include/asm/processor.h | 4 +
arch/arm64/include/asm/sysreg.h | 62 +++++
arch/arm64/include/asm/thread_info.h | 4 +-
arch/arm64/include/uapi/asm/hwcap.h | 2 +
arch/arm64/include/uapi/asm/mman.h | 14 ++
arch/arm64/include/uapi/asm/ptrace.h | 1 +
arch/arm64/kernel/Makefile | 1 +
arch/arm64/kernel/cpufeature.c | 60 +++++
arch/arm64/kernel/cpuinfo.c | 2 +
arch/arm64/kernel/entry.S | 27 +++
arch/arm64/kernel/mte.c | 137 +++++++++++
arch/arm64/kernel/process.c | 22 +-
arch/arm64/kernel/ptrace.c | 2 +-
arch/arm64/kernel/signal.c | 8 +
arch/arm64/kernel/syscall.c | 10 +
arch/arm64/lib/Makefile | 2 +
arch/arm64/lib/clear_page.S | 7 +-
arch/arm64/lib/copy_page.S | 23 ++
arch/arm64/lib/mte.S | 46 ++++
arch/arm64/mm/Makefile | 1 +
arch/arm64/mm/cmppages.c | 26 ++
arch/arm64/mm/dump.c | 4 +
arch/arm64/mm/fault.c | 9 +-
arch/arm64/mm/mmu.c | 22 +-
arch/arm64/mm/proc.S | 8 +-
fs/proc/task_mmu.c | 4 +
include/linux/mm.h | 8 +
include/linux/mman.h | 22 +-
include/uapi/asm-generic/siginfo.h | 4 +-
include/uapi/linux/prctl.h | 9 +
mm/mmap.c | 9 +
mm/mprotect.c | 6 +
mm/shmem.c | 3 +
mm/util.c | 2 +-
51 files changed, 994 insertions(+), 27 deletions(-)
create mode 100644 Documentation/arm64/memory-tagging-extension.rst
create mode 100644 arch/arm64/include/asm/mman.h
create mode 100644 arch/arm64/include/asm/mte.h
create mode 100644 arch/arm64/include/uapi/asm/mman.h
create mode 100644 arch/arm64/kernel/mte.c
create mode 100644 arch/arm64/lib/mte.S
create mode 100644 arch/arm64/mm/cmppages.c
