Control flow enforcement technology (CET) is an upcoming Intel processor family feature that prevents return/jmp-oriented programming attacks. It has two components: shadow stack (SHSTK) and indirect branch tracking (IBT). The specification is at: https://software.intel.com/sites/default/files/managed/4d/2a/ control-flow-enforcement-technology-preview.pdf The SHSTK is a secondary stack allocated from system memory. The CALL instruction stores a secure copy of the return address on the SHSTK; the RET instruction compares the return address from the program stack to the SHSTK copy. Any mismatch triggers a control protection fault. When the IBT is enabled, the processor verifies an indirect CALL/JMP destination is an ENDBR instruction; otherwise, it raises a control protection fault. The compiler inserts ENDBRs at all valid branch targets. CET can be enabled for both kernel and user mode protection. The Linux kernel patches being posted are for user-mode protection. They are grouped into four series: (1) CPUID enumeration, CET XSAVES system states, and documentation; (2) Kernel config, exception handling, and memory management changes; (3) SHSTK support; (4) IBT support, command-line tool, PTRACE. Yu-cheng Yu (5): x86/cpufeatures: Add CPUIDs for Control-flow Enforcement Technology (CET) x86/fpu/xstate: Change some names to separate XSAVES system and user states x86/fpu/xstate: Enable XSAVES system states x86/fpu/xstate: Add XSAVES system states for shadow stack Documentation/x86: Add CET description Documentation/admin-guide/kernel-parameters.txt | 6 + Documentation/x86/intel_cet.txt | 161 ++++++++++++++++++++++++ arch/x86/include/asm/cpufeatures.h | 2 + arch/x86/include/asm/fpu/internal.h | 6 +- arch/x86/include/asm/fpu/types.h | 22 ++++ arch/x86/include/asm/fpu/xstate.h | 31 ++--- arch/x86/include/uapi/asm/processor-flags.h | 2 + arch/x86/kernel/cpu/scattered.c | 1 + arch/x86/kernel/fpu/core.c | 11 +- arch/x86/kernel/fpu/init.c | 10 -- arch/x86/kernel/fpu/signal.c | 6 +- arch/x86/kernel/fpu/xstate.c | 152 +++++++++++++--------- 12 files changed, 319 insertions(+), 91 deletions(-) create mode 100644 Documentation/x86/intel_cet.txt -- 2.15.1
