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. The series is based on v5.4-rc2. A branch for this series is available in Git [3]. This series supersedes the previous v2 posting [1], and also incorporates my proposed ELF GNU property parsing implementation. (See [2] for the ABI spec describing NT_GNU_PROPERTY_TYPE_0). Changes: * Minor cleanups / nitpick fixes only. Since this is an interim update so that Mark Brown can take over development of the series, I haven't fully retested. The series builds with defconfig. There are some outstanding discussion points: see notes in the invidual patches, particularly on patch 5. Notes: * No documentation yet. We could do with some being written before this series gets merged. * 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. [1] [PATCH v2 00/12] arm64: ARMv8.5-A: Branch Target Identification support https://lore.kernel.org/lkml/1570733080-21015-1-git-send-email-Dave.Martin@xxxxxxx/ [2] Linux Extensions to gABI https://github.com/hjl-tools/linux-abi/wiki/Linux-Extensions-to-gABI [3] Git branch: git://linux-arm.org/linux-dm.git arm64/bti/v3/head http://linux-arm.org/git?p=linux-dm.git;a=shortlog;h=refs/heads/arm64/bti/v3/head Dave Martin (12): ELF: UAPI and Kconfig additions for ELF program properties ELF: Add ELF program property parsing support mm: Reserve asm-generic prot flag 0x10 for arch use arm64: docs: cpu-feature-registers: Document ID_AA64PFR1_EL1 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 BYTPE bits when printing PSTATE arm64: traps: Fix inconsistent faulting 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 Documentation/arm64/cpu-feature-registers.rst | 17 ++- Documentation/arm64/elf_hwcaps.rst | 4 + arch/arm64/Kconfig | 31 ++++++ 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/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 | 8 ++ 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 | 1 + arch/arm64/kernel/cpufeature.c | 33 ++++++ arch/arm64/kernel/cpuinfo.c | 1 + arch/arm64/kernel/entry.S | 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 | 126 +++++++++++----------- 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/asm-generic/mman-common.h | 1 + include/uapi/linux/elf.h | 11 ++ 32 files changed, 560 insertions(+), 79 deletions(-) create mode 100644 arch/arm64/include/asm/mman.h create mode 100644 arch/arm64/include/uapi/asm/mman.h -- 2.1.4
