[v6,00/11] arm64: Branch Target Identification support

Message

Mark Brown Feb. 12, 2020, 7:28 p.m. UTC

This patch implements support for ARMv8.5-A Branch Target Identification
(BTI), which is a control flow integrity protection feature introduced
as part of the ARMv8.5-A extensions.

Changes:

v6:
 - Rebase onto v5.6-rc1.
 - Fix typos s/BYTPE/BTYPE/ in commit log for "arm64: BTI: Decode BYTPE
   bits when printing PSTATE".
v5:
 - Changed a bunch of -EIO to -ENOEXEC in the ELF parsing code.
 - Move PSR_BTYPE defines to UAPI.
 - Use compat_user_mode() rather than open coding.
 - Fix a typo s/BYTPE/BTYPE/ in syscall.c
v4:
 - Dropped patch fixing existing documentation as it has already been merged.
 - Convert WARN_ON() to WARN_ON_ONCE() in "ELF: Add ELF program property
   parsing support".
 - Added display of guarded pages to ptdump.
 - Updated for conversion of exception handling from assembler to C.

Notes:

 * GCC 9 can compile backwards-compatible BTI-enabled code with
   -mbranch-protection=bti or -mbranch-protection=standard.

 * Binutils trunk supports the new ELF note, but this wasn't in a release
   the last time I posted this series.  (The situation _might_ have changed
   in the meantime...)

   Creation of a BTI-enabled binary requires _everything_ linked in to
   be BTI-enabled.  For now ld --force-bti can be used to override this,
   but some things may break until the required C library support is in
   place.

   There is no straightforward way to mark a .s file as BTI-enabled:
   scraping the output from gcc -S works as a quick hack for now.

   readelf -n can be used to examing the program properties in an ELF
   file.

 * Runtime mmap() and mprotect() can be used to enable BTI on a
   page-by-page basis using the new PROT_BTI, but the code in the
   affected pages still needs to be written or compiled to contain the
   appopriate BTI landing pads.

Dave Martin (10):
  ELF: UAPI and Kconfig additions for ELF program properties
  ELF: Add ELF program property parsing support
  arm64: Basic Branch Target Identification support
  elf: Allow arch to tweak initial mmap prot flags
  arm64: elf: Enable BTI at exec based on ELF program properties
  arm64: BTI: Decode BTYPE bits when printing PSTATE
  arm64: unify native/compat instruction skipping
  arm64: traps: Shuffle code to eliminate forward declarations
  arm64: BTI: Reset BTYPE when skipping emulated instructions
  KVM: arm64: BTI: Reset BTYPE when skipping emulated instructions

Mark Brown (1):
  arm64: mm: Display guarded pages in ptdump

 Documentation/arm64/cpu-feature-registers.rst |   2 +
 Documentation/arm64/elf_hwcaps.rst            |   5 +
 arch/arm64/Kconfig                            |  25 +++
 arch/arm64/include/asm/cpucaps.h              |   3 +-
 arch/arm64/include/asm/cpufeature.h           |   6 +
 arch/arm64/include/asm/elf.h                  |  50 ++++++
 arch/arm64/include/asm/esr.h                  |   2 +-
 arch/arm64/include/asm/exception.h            |   1 +
 arch/arm64/include/asm/hwcap.h                |   1 +
 arch/arm64/include/asm/kvm_emulate.h          |   6 +-
 arch/arm64/include/asm/mman.h                 |  37 +++++
 arch/arm64/include/asm/pgtable-hwdef.h        |   1 +
 arch/arm64/include/asm/pgtable.h              |   2 +-
 arch/arm64/include/asm/ptrace.h               |   1 +
 arch/arm64/include/asm/sysreg.h               |   4 +
 arch/arm64/include/uapi/asm/hwcap.h           |   1 +
 arch/arm64/include/uapi/asm/mman.h            |   9 ++
 arch/arm64/include/uapi/asm/ptrace.h          |   9 ++
 arch/arm64/kernel/cpufeature.c                |  33 ++++
 arch/arm64/kernel/cpuinfo.c                   |   1 +
 arch/arm64/kernel/entry-common.c              |  11 ++
 arch/arm64/kernel/process.c                   |  36 ++++-
 arch/arm64/kernel/ptrace.c                    |   2 +-
 arch/arm64/kernel/signal.c                    |  16 ++
 arch/arm64/kernel/syscall.c                   |  18 +++
 arch/arm64/kernel/traps.c                     | 127 +++++++--------
 arch/arm64/mm/dump.c                          |   5 +
 fs/Kconfig.binfmt                             |   6 +
 fs/binfmt_elf.c                               | 145 +++++++++++++++++-
 fs/compat_binfmt_elf.c                        |   4 +
 include/linux/elf.h                           |  43 ++++++
 include/linux/mm.h                            |   3 +
 include/uapi/linux/elf.h                      |  11 ++
 33 files changed, 551 insertions(+), 75 deletions(-)
 create mode 100644 arch/arm64/include/asm/mman.h
 create mode 100644 arch/arm64/include/uapi/asm/mman.h