Commit d157a9bc authored by Andrew Paverd's avatar Andrew Paverd Committed by David Chisnall
Browse files

Add Windows Control Flow Guard checks (/guard:cf). 

Summary:
A new function pass (Transforms/CFGuard/CFGuard.cpp) inserts CFGuard checks on
indirect function calls, using either the check mechanism (X86, ARM, AArch64) or
or the dispatch mechanism (X86-64). The check mechanism requires a new calling
convention for the supported targets. The dispatch mechanism adds the target as
an operand bundle, which is processed by SelectionDAG. Another pass
(CodeGen/CFGuardLongjmp.cpp) identifies and emits valid longjmp targets, as
required by /guard:cf. This feature is enabled using the `cfguard` CC1 option.

Reviewers: thakis, rnk, theraven, pcc

Subscribers: ychen, hans, metalcanine, dmajor, tomrittervg, alex, mehdi_amini, mgorny, javed.absar, kristof.beyls, hiraditya, steven_wu, dexonsmith, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D65761
parent a233e7d7

clang/docs/ClangCommandLineReference.rst

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@@ -124,7 +124,11 @@ Output path for the plist report 


.. option:: -cfguard



Emit tables required for Windows Control Flow Guard.

Emit tables and checks for Windows Control Flow Guard.



.. option:: -cfguard-no-checks



Emit tables required for Windows Control Flow Guard without checks.



.. option:: -client\_name<arg>

clang/include/clang/Basic/CodeGenOptions.def

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@@ -37,6 +37,7 @@ CODEGENOPT(AssumeSaneOperatorNew , 1, 1) ///< implicit __attribute__((malloc)) o 
CODEGENOPT(Autolink          , 1, 1) ///< -fno-autolink

CODEGENOPT(ObjCAutoRefCountExceptions , 1, 0) ///< Whether ARC should be EH-safe.

CODEGENOPT(Backchain         , 1, 0) ///< -mbackchain

CODEGENOPT(ControlFlowGuardNoChecks  , 1, 0) ///< -cfguard-no-checks

CODEGENOPT(ControlFlowGuard  , 1, 0) ///< -cfguard

CODEGENOPT(CoverageExtraChecksum, 1, 0) ///< Whether we need a second checksum for functions in GCNO files.

CODEGENOPT(CoverageNoFunctionNamesInData, 1, 0) ///< Do not include function names in GCDA files.

clang/include/clang/Driver/CC1Options.td

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@@ -400,6 +400,10 @@ def msign_return_address_key_EQ : Joined<["-"], "msign-return-address-key=">, 
    Values<"a_key,b_key">;

def mbranch_target_enforce : Flag<["-"], "mbranch-target-enforce">;

def fno_dllexport_inlines : Flag<["-"], "fno-dllexport-inlines">;

def cfguard_no_checks : Flag<["-"], "cfguard-no-checks">,

    HelpText<"Emit Windows Control Flow Guard tables only (no checks)">;

def cfguard : Flag<["-"], "cfguard">,

    HelpText<"Emit Windows Control Flow Guard tables and checks">;



//===----------------------------------------------------------------------===//

// Dependency Output Options

clang/include/clang/Driver/Options.td

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@@ -503,8 +503,6 @@ def bind__at__load : Flag<["-"], "bind_at_load">; 
def bundle__loader : Separate<["-"], "bundle_loader">;

def bundle : Flag<["-"], "bundle">;

def b : JoinedOrSeparate<["-"], "b">, Flags<[Unsupported]>;

def cfguard : Flag<["-"], "cfguard">, Flags<[CC1Option]>,

  HelpText<"Emit tables required for Windows Control Flow Guard.">;

def cl_opt_disable : Flag<["-"], "cl-opt-disable">, Group<opencl_Group>, Flags<[CC1Option]>,

  HelpText<"OpenCL only. This option disables all optimizations. By default optimizations are enabled.">;

def cl_strict_aliasing : Flag<["-"], "cl-strict-aliasing">, Group<opencl_Group>, Flags<[CC1Option]>,

clang/lib/CodeGen/CodeGenModule.cpp

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@@ -482,8 +482,11 @@ void CodeGenModule::Release() { 
    getModule().addModuleFlag(llvm::Module::Warning, "CodeViewGHash", 1);

  }

  if (CodeGenOpts.ControlFlowGuard) {

    // We want function ID tables for Control Flow Guard.

    getModule().addModuleFlag(llvm::Module::Warning, "cfguardtable", 1);

    // Function ID tables and checks for Control Flow Guard (cfguard=2).

    getModule().addModuleFlag(llvm::Module::Warning, "cfguard", 2);

  } else if (CodeGenOpts.ControlFlowGuardNoChecks) {

    // Function ID tables for Control Flow Guard (cfguard=1).

    getModule().addModuleFlag(llvm::Module::Warning, "cfguard", 1);

  }

  if (CodeGenOpts.OptimizationLevel > 0 && CodeGenOpts.StrictVTablePointers) {

    // We don't support LTO with 2 with different StrictVTablePointers