The 03/16/2020 16:50, Mark Brown wrote: > This patch series 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. i was playing with this and it seems the kernel does not add PROT_BTI to non-static executables (i.e. there is an interpreter). i thought any elf that the kernel maps would get PROT_BTI from the kernel. (i want to remove the mprotect in glibc when not necessary) i tested by linking a hello world exe with -Wl,-z,force-bti (and verified that the property note is there) and expected it to crash (with SIGILL) when the dynamic linker jumps to _start in the exe, but it executed without errors (if i do the mprotect in glibc then i get SIGILL as expected). is this deliberate? does the kernel map static exe and dynamic linked exe differently? i cant tell looking at the patches where this logic comes from. > > Changes: > > v10: > - Fix build for !COMPAT configurations. > v9: > - Move Kconfig addition to final patch in series. > - Add patch from Daniel Kiss adding BTI information to smaps, this has > a trivial conflict with a .rst conversion in -next. > v8: > - Remove a redundant IS_ENABLED(CONFIG_ARM64_BTI) check. > v7: > - Rebase onto v5.6-rc3. > - Move comment about keeping NT_GNU_PROPERTY_TYPE_0 internal into first > patch. > - Add an explicit check for system_supports_bti() when parsing BTI ELF > property for improved robustness. > 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 2.33 and later support the new ELF note. > > 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 > appropriate BTI landing pads. > > Daniel Kiss (1): > mm: smaps: Report arm64 guarded pages in smaps > > Dave Martin (11): > 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 BYTPE 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 > arm64: BTI: Add Kconfig entry for userspace BTI > > Mark Brown (1): > arm64: mm: Display guarded pages in ptdump > > Documentation/arm64/cpu-feature-registers.rst | 2 + > Documentation/arm64/elf_hwcaps.rst | 5 + > Documentation/filesystems/proc.txt | 1 + > 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 | 131 ++++++++-------- > arch/arm64/mm/dump.c | 5 + > fs/Kconfig.binfmt | 6 + > fs/binfmt_elf.c | 145 +++++++++++++++++- > fs/compat_binfmt_elf.c | 4 + > fs/proc/task_mmu.c | 3 + > include/linux/elf.h | 43 ++++++ > include/linux/mm.h | 3 + > include/uapi/linux/elf.h | 11 ++ > 35 files changed, 560 insertions(+), 74 deletions(-) > create mode 100644 arch/arm64/include/asm/mman.h > create mode 100644 arch/arm64/include/uapi/asm/mman.h > > > base-commit: f8788d86ab28f61f7b46eb6be375f8a726783636 > -- > 2.20.1 > --
