[PATCH v16 00/26] Control-flow Enforcement: Shadow Stack

From: Yu-cheng Yu
Date: Wed Dec 09 2020 - 17:25:00 EST

Control-flow Enforcement (CET) is a new Intel processor feature that blocks
return/jump-oriented programming attacks. Details are in "Intel 64 and
IA-32 Architectures Software Developer's Manual" [1].

CET can protect applications and the kernel. This series enables only
application-level protection, and has three parts:

- Shadow stack [2],
- Indirect branch tracking [3], and
- Selftests [4].

I have run tests on these patches for quite some time, and they have been
very stable. Linux distributions with CET are available now, and Intel
processors with CET are already on the market. It would be nice if CET
support can be accepted into the kernel. I will be working to address any
issues should they come up.

Changes in v16:
- Rebase to v5.10-rc7.
- Replace Kconfig options for Shadow Stack and IBT with just one option,
and fix some small issues (AS dependency check, wording).
- Create a software-defined X86_FEATURE_CET to indicate either Shadow Stack
or IBT is present, simplify XSAVES dependency check. Move parameter
parsing to cpu_parse_early_param().
- Fix control-protection fault handling for kernel-mode faults.
- Drop the patch that changes _PAGE_DIRTY to _PAGE_DIRTY_HW.
- Small changes to the documentation to reflect Kconfig changes and add
LLVM information.

[1] Intel 64 and IA-32 Architectures Software Developer's Manual:

https://software.intel.com/en-us/download/intel-64-and-ia-32-
architectures-sdm-combined-volumes-1-2a-2b-2c-2d-3a-3b-3c-3d-and-4

[2] CET Shadow Stack patches v15:

https://lkml.kernel.org/r/20201110162211.9207-1-yu-cheng.yu@xxxxxxxxx/

[3] Indirect Branch Tracking patches v15.

https://lkml.kernel.org/r/20201110162448.9846-1-yu-cheng.yu@xxxxxxxxx/

[4] I am holding off the selftests changes and working to get Acked-by's.
The earlier version of the selftests patches:

https://lkml.kernel.org/r/20200521211720.20236-1-yu-cheng.yu@xxxxxxxxx/

[5] The kernel ptrace patch is tested with an Intel-internal updated GDB.
I am holding off the kernel ptrace patch to re-test it with my earlier
patch for fixing regset holes.

Yu-cheng Yu (26):
Documentation/x86: Add CET description
x86/cet/shstk: Add Kconfig option for user-mode control-flow
protection
x86/cpufeatures: Add CET CPU feature flags for Control-flow
Enforcement Technology (CET)
x86/cpufeatures: Introduce X86_FEATURE_CET and setup functions
x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states
x86/cet: Add control-protection fault handler
x86/mm: Remove _PAGE_DIRTY from kernel RO pages
x86/mm: Introduce _PAGE_COW
drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS
x86/mm: Update pte_modify for _PAGE_COW
x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for
transition from _PAGE_DIRTY to _PAGE_COW
mm: Introduce VM_SHSTK for shadow stack memory
x86/mm: Shadow Stack page fault error checking
x86/mm: Update maybe_mkwrite() for shadow stack
mm: Fixup places that call pte_mkwrite() directly
mm: Add guard pages around a shadow stack.
mm/mmap: Add shadow stack pages to memory accounting
mm: Update can_follow_write_pte() for shadow stack
mm: Re-introduce vm_flags to do_mmap()
x86/cet/shstk: User-mode shadow stack support
x86/cet/shstk: Handle signals for shadow stack
binfmt_elf: Define GNU_PROPERTY_X86_FEATURE_1_AND properties
ELF: Introduce arch_setup_elf_property()
x86/cet/shstk: Handle thread shadow stack
x86/cet/shstk: Add arch_prctl functions for shadow stack
mm: Introduce PROT_SHSTK for shadow stack

.../admin-guide/kernel-parameters.txt | 6 +
Documentation/x86/index.rst | 1 +
Documentation/x86/intel_cet.rst | 136 +++++++
arch/arm64/include/asm/elf.h | 5 +
arch/x86/Kconfig | 28 ++
arch/x86/Kconfig.assembler | 5 +
arch/x86/ia32/ia32_signal.c | 17 +
arch/x86/include/asm/cet.h | 42 +++
arch/x86/include/asm/cpufeatures.h | 4 +-
arch/x86/include/asm/disabled-features.h | 17 +-
arch/x86/include/asm/elf.h | 13 +
arch/x86/include/asm/fpu/internal.h | 10 +
arch/x86/include/asm/fpu/types.h | 23 +-
arch/x86/include/asm/fpu/xstate.h | 6 +-
arch/x86/include/asm/idtentry.h | 4 +
arch/x86/include/asm/mman.h | 83 +++++
arch/x86/include/asm/mmu_context.h | 3 +
arch/x86/include/asm/msr-index.h | 19 +
arch/x86/include/asm/page_64_types.h | 10 +
arch/x86/include/asm/pgtable.h | 202 ++++++++++-
arch/x86/include/asm/pgtable_types.h | 48 ++-
arch/x86/include/asm/processor.h | 5 +
arch/x86/include/asm/special_insns.h | 32 ++
arch/x86/include/asm/trap_pf.h | 2 +
arch/x86/include/uapi/asm/mman.h | 28 +-
arch/x86/include/uapi/asm/prctl.h | 4 +
arch/x86/include/uapi/asm/processor-flags.h | 2 +
arch/x86/include/uapi/asm/sigcontext.h | 9 +
arch/x86/kernel/Makefile | 2 +
arch/x86/kernel/cet.c | 343 ++++++++++++++++++
arch/x86/kernel/cet_prctl.c | 68 ++++
arch/x86/kernel/cpu/common.c | 40 +-
arch/x86/kernel/cpu/cpuid-deps.c | 2 +
arch/x86/kernel/fpu/signal.c | 100 +++++
arch/x86/kernel/fpu/xstate.c | 10 +-
arch/x86/kernel/idt.c | 4 +
arch/x86/kernel/process.c | 14 +-
arch/x86/kernel/process_64.c | 32 ++
arch/x86/kernel/signal.c | 10 +
arch/x86/kernel/signal_compat.c | 2 +-
arch/x86/kernel/traps.c | 59 +++
arch/x86/mm/fault.c | 19 +
arch/x86/mm/mmap.c | 2 +
arch/x86/mm/pat/set_memory.c | 2 +-
arch/x86/mm/pgtable.c | 25 ++
drivers/gpu/drm/i915/gvt/gtt.c | 2 +-
fs/aio.c | 2 +-
fs/binfmt_elf.c | 4 +
fs/proc/task_mmu.c | 3 +
include/linux/elf.h | 6 +
include/linux/mm.h | 38 +-
include/linux/pgtable.h | 35 ++
include/uapi/asm-generic/siginfo.h | 3 +-
include/uapi/linux/elf.h | 9 +
ipc/shm.c | 2 +-
mm/gup.c | 8 +-
mm/huge_memory.c | 10 +-
mm/memory.c | 5 +-
mm/migrate.c | 3 +-
mm/mmap.c | 23 +-
mm/mprotect.c | 2 +-
mm/nommu.c | 4 +-
mm/util.c | 2 +-
63 files changed, 1576 insertions(+), 83 deletions(-)
create mode 100644 Documentation/x86/intel_cet.rst
create mode 100644 arch/x86/include/asm/cet.h
create mode 100644 arch/x86/include/asm/mman.h
create mode 100644 arch/x86/kernel/cet.c
create mode 100644 arch/x86/kernel/cet_prctl.c

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2.21.0