[PATCH v2 00/19] arm64: Memory Tagging Extension user-space support

[Catalin Marinas <catalin.marinas@arm.com>]

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@arm.com/
[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