[PATCH] D76812: [X86] Add Indirect Thunk Support to X86 to mitigate Load Value Injection (LVI) [3/3]

[Scott Constable via Phabricator via cfe-commits]

sconstab created this revision.
sconstab added reviewers: craig.topper, andrew.w.kaylor, zbrid, chandlerc.
Herald added subscribers: jfb, hiraditya.
sconstab added a parent revision: D76811: [X86] Refactor X86IndirectThunks.cpp to Accomodate Mitigations other than Retpoline [2/3].
sconstab retitled this revision from "Add Indirect Thunk Support to X86 to mitigate Load Value Injection (LVI) [3/3]" to "[X86] Add Indirect Thunk Support to X86 to mitigate Load Value Injection (LVI) [3/3]".

This pass replaces each indirect call/jump with a direct call to a thunk that looks like:

  lfence
  jmpq *%r11

This ensures that if the value in register `%r11` was loaded from memory, then
the value in `%r11` is (architecturally) correct prior to the jump.
Also adds a new target feature to X86: +lvi-cfi
("cfi" meaning control-flow integrity)
The feature can be added via clang CLI using `-mlvi-cfi`.

This is an alternate implementation to https://reviews.llvm.org/D75934 That merges the thunk insertion functionality with the existing X86 retpoline code.


https://reviews.llvm.org/D76812

Files:
  clang/include/clang/Driver/Options.td
  clang/lib/Driver/ToolChains/Arch/X86.cpp
  llvm/lib/Target/X86/X86.td
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/lib/Target/X86/X86IndirectThunks.cpp
  llvm/lib/Target/X86/X86Subtarget.h
  llvm/test/CodeGen/X86/lvi-hardening-indirectbr.ll

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