[X86] Add a Pass that builds a Condensed CFG for Load Value Injection (LVI) Gadgets

Adds a new data structure, ImmutableGraph, and uses RDF to find LVI gadgets and add them to a MachineGadgetGraph.

More specifically, a new X86 machine pass finds Load Value Injection (LVI) gadgets consisting of a load from memory (i.e., SOURCE), and any operation that may transmit the value loaded from memory over a covert channel, or use the value loaded from memory to determine a branch/call target (i.e., SINK).

Also adds a new target feature to X86: +lvi-load-hardening

The feature can be added via the clang CLI using -mlvi-hardening.

Differential Revision: https://reviews.llvm.org/D75936

Author: scottconstable

clang/include/clang/Driver/Options.td

@@ -2309,6 +2309,10 @@ def mspeculative_load_hardening : Flag<["-"], "mspeculative-load-hardening">,
   Group<m_Group>, Flags<[CoreOption,CC1Option]>;
 def mno_speculative_load_hardening : Flag<["-"], "mno-speculative-load-hardening">,
   Group<m_Group>, Flags<[CoreOption]>;
+def mlvi_hardening : Flag<["-"], "mlvi-hardening">, Group<m_Group>, Flags<[CoreOption,DriverOption]>,
+  HelpText<"Enable all mitigations for Load Value Injection (LVI)">;
+def mno_lvi_hardening : Flag<["-"], "mno-lvi-hardening">, Group<m_Group>, Flags<[CoreOption,DriverOption]>,
+  HelpText<"Disable mitigations for Load Value Injection (LVI)">;
 def mlvi_cfi : Flag<["-"], "mlvi-cfi">, Group<m_Group>, Flags<[CoreOption,DriverOption]>,
   HelpText<"Enable only control-flow mitigations for Load Value Injection (LVI)">;
 def mno_lvi_cfi : Flag<["-"], "mno-lvi-cfi">, Group<m_Group>, Flags<[CoreOption,DriverOption]>,

clang/lib/Driver/ToolChains/Arch/X86.cpp

@@ -173,7 +173,13 @@ void x86::getX86TargetFeatures(const Driver &D, const llvm::Triple &Triple,
   }
 
   auto LVIOpt = clang::driver::options::ID::OPT_INVALID;
-  if (Args.hasFlag(options::OPT_mlvi_cfi, options::OPT_mno_lvi_cfi, false)) {
+  if (Args.hasFlag(options::OPT_mlvi_hardening, options::OPT_mno_lvi_hardening,
+                   false)) {
+    Features.push_back("+lvi-load-hardening");
+    Features.push_back("+lvi-cfi"); // load hardening implies CFI protection
+    LVIOpt = options::OPT_mlvi_hardening;
+  } else if (Args.hasFlag(options::OPT_mlvi_cfi, options::OPT_mno_lvi_cfi,
+                          false)) {
     Features.push_back("+lvi-cfi");
     LVIOpt = options::OPT_mlvi_cfi;
   }

clang/test/Driver/x86-target-features.c

@@ -159,6 +159,11 @@
 // LVICFI: "-target-feature" "+lvi-cfi"
 // NO-LVICFI-NOT: lvi-cfi
 
+// RUN: %clang -target i386-linux-gnu -mlvi-hardening %s -### -o %t.o 2>&1 | FileCheck -check-prefix=LVIHARDENING %s
+// RUN: %clang -target i386-linux-gnu -mno-lvi-hardening %s -### -o %t.o 2>&1 | FileCheck -check-prefix=NO-LVIHARDENING %s
+// LVIHARDENING: "-target-feature" "+lvi-load-hardening" "-target-feature" "+lvi-cfi"
+// NO-LVIHARDENING-NOT: lvi
+
 // RUN: %clang -target i386-linux-gnu -mwaitpkg %s -### -o %t.o 2>&1 | FileCheck -check-prefix=WAITPKG %s
 // RUN: %clang -target i386-linux-gnu -mno-waitpkg %s -### -o %t.o 2>&1 | FileCheck -check-prefix=NO-WAITPKG %s
 // WAITPKG: "-target-feature" "+waitpkg"

llvm/lib/Target/X86/CMakeLists.txt

@@ -52,6 +52,7 @@ set(sources
   X86InstrInfo.cpp
   X86EvexToVex.cpp
   X86LegalizerInfo.cpp
+  X86LoadValueInjectionLoadHardening.cpp
   X86LoadValueInjectionRetHardening.cpp
   X86MCInstLower.cpp
   X86MachineFunctionInfo.cpp