Seedarg/member/wip

clang/include/clang/AST/Decl.h

@@ -65,6 +65,7 @@ class Module;
 class NamespaceDecl;
 class ParmVarDecl;
 class RecordDecl;
+class RecordFieldReorganizer;
 class Stmt;
 class StringLiteral;
 class TagDecl;

clang/include/clang/AST/DeclBase.h

@@ -1270,6 +1270,8 @@ class DeclContext {
   friend class ExternalASTSource;
   /// For CreateStoredDeclsMap
   friend class DependentDiagnostic;
+  /// For fine-grained control of field order
+  friend class RecordFieldReorganizer;
   /// For hasNeedToReconcileExternalVisibleStorage,
   /// hasLazyLocalLexicalLookups, hasLazyExternalLexicalLookups
   friend class ASTWriter;

clang/include/clang/AST/RandstructSeed.h

@@ -0,0 +1,8 @@
+#ifndef RANDSTRUCTSEED_H
+#define RANDSTRUCTSEED_H
+#include <string>
+namespace clang {
+extern std::string RandstructSeed;
+extern bool RandstructAutoSelect;
+}
+#endif

clang/include/clang/AST/RecordFieldReorganizer.h

@@ -0,0 +1,61 @@
+//===-- RecordFieldReorganizer.h - Interface for manipulating field order --*-
+// C++
+//-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This header file contains the base class that defines an interface for
+// manipulating a RecordDecl's field layouts.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_LIB_AST_RECORDFIELDREORGANIZER_H
+#define LLVM_CLANG_LIB_AST_RECORDFIELDREORGANIZER_H
+
+#include "Decl.h"
+#include <random>
+
+namespace clang {
+
+// FIXME: Find a better alternative to SmallVector with hardcoded size!
+
+class RecordFieldReorganizer {
+public:
+  virtual ~RecordFieldReorganizer() = default;
+  void reorganizeFields(const ASTContext &C, const RecordDecl *D);
+
+protected:
+  virtual void reorganize(const ASTContext &C, const RecordDecl *D,
+                          SmallVector<Decl *, 64> &NewOrder) = 0;
+
+private:
+  void commit(const RecordDecl *D,
+              SmallVectorImpl<Decl *> &NewFieldOrder) const;
+};
+
+class Randstruct : public RecordFieldReorganizer {
+private:
+  std::seed_seq Seq;
+  std::default_random_engine rng;
+
+public:
+  /// Determines if the Record can be safely and easily randomized based on
+  /// certain criteria (see implementation).
+  Randstruct(std::string seed) : Seq(seed.begin(), seed.end()), rng(Seq) {}
+  static bool isTriviallyRandomizable(const RecordDecl *D);
+
+protected:
+  SmallVector<Decl *, 64> randomize(SmallVector<Decl *, 64> fields);
+  SmallVector<Decl *, 64> perfrandomize(const ASTContext &ctx,
+                                        SmallVector<Decl *, 64> fields);
+  virtual void reorganize(const ASTContext &C, const RecordDecl *D,
+                          SmallVector<Decl *, 64> &NewOrder) override;
+};
+
+} // namespace clang
+
+#endif

clang/include/clang/Basic/Attr.td

@@ -3201,3 +3201,10 @@ def ObjCExternallyRetained : InheritableAttr {
   let Subjects = SubjectList<[NonParmVar, Function, Block, ObjCMethod]>;
   let Documentation = [ObjCExternallyRetainedDocs];
 }
+
+def RandomizeLayout : InheritableAttr {
+  let Spellings = [GCC<"randomize_layout">, Declspec<"randomize_layout">,
+    Keyword<"randomize_layout">];
+  let Subjects = SubjectList<[Record]>;
+  let Documentation = [ClangRandstructDocs];
+}

clang/include/clang/Basic/AttrDocs.td

@@ -4094,4 +4094,22 @@ Likewise, when applied to a strong local variable, that variable becomes
 ``const`` and is considered externally-retained.
 
 When compiled without ``-fobjc-arc``, this attribute is ignored.
-}]; }
+}]; 
+}
+
+def ClangRandstructDocs : Documentation {
+  let Category = DocCatVariable;
+  let Content = [{
+The attribute ``randomize_layout`` can be applied to the declaration of
+a record. ``randomize_layout`` instructs the compiler to randomize the memory layout 
+of the member variables of the record.
+.. code-block:: c
+
+  // Indicates that this struct should be randomized by Randstruct implementation.
+  struct s {
+    char *a;
+    char *b;
+    char *c;
+  }__attribute__((randomize_layout));
+}];
+}

clang/include/clang/Basic/DiagnosticASTKinds.td

@@ -343,4 +343,6 @@ def warn_padded_struct_size : Warning<
   InGroup<Padded>, DefaultIgnore;
 def warn_unnecessary_packed : Warning<
   "packed attribute is unnecessary for %0">, InGroup<Packed>, DefaultIgnore;
+def warn_randomize_attr_union : Warning<
+  "union declared with 'randomize_layout' attribute">, InGroup<DiagGroup<"randomize-layout">>;
 }

clang/include/clang/Driver/CC1Options.td

@@ -422,6 +422,8 @@ def fcaret_diagnostics_max_lines :
   HelpText<"Set the maximum number of source lines to show in a caret diagnostic">;
 def fmessage_length : Separate<["-"], "fmessage-length">, MetaVarName<"<N>">,
   HelpText<"Format message diagnostics so that they fit within N columns or fewer, when possible.">;
+def randstruct_seed : Separate<["-"], "randstruct-seed">, MetaVarName<"<N>">,
+  HelpText<"Randomization seed for random struct layouts">;
 def verify_EQ : CommaJoined<["-"], "verify=">,
   MetaVarName<"<prefixes>">,
   HelpText<"Verify diagnostic output using comment directives that start with"

clang/include/clang/Driver/Options.td

@@ -1258,6 +1258,7 @@ def fmacro_backtrace_limit_EQ : Joined<["-"], "fmacro-backtrace-limit=">,
 def fmerge_all_constants : Flag<["-"], "fmerge-all-constants">, Group<f_Group>,
   Flags<[CC1Option, CoreOption]>, HelpText<"Allow merging of constants">;
 def fmessage_length_EQ : Joined<["-"], "fmessage-length=">, Group<f_Group>;
+def randstruct_seed_EQ : Joined<["-"], "randstruct-seed=">, Group<f_Group>;
 def fms_extensions : Flag<["-"], "fms-extensions">, Group<f_Group>, Flags<[CC1Option, CoreOption]>,
   HelpText<"Accept some non-standard constructs supported by the Microsoft compiler">;
 def fms_compatibility : Flag<["-"], "fms-compatibility">, Group<f_Group>, Flags<[CC1Option, CoreOption]>,
@@ -1750,6 +1751,9 @@ def freroll_loops : Flag<["-"], "freroll-loops">, Group<f_Group>,
   HelpText<"Turn on loop reroller">, Flags<[CC1Option]>;
 def fno_reroll_loops : Flag<["-"], "fno-reroll-loops">, Group<f_Group>,
   HelpText<"Turn off loop reroller">;
+def randstruct_auto : Flag<["-"], "randstruct-auto">,
+  HelpText<"Enable automatic structure selection for field randomization; "
+           "Disable for specific structures with attribute no_randomize_layout">, Flags<[CC1Option]>;
 def ftrigraphs : Flag<["-"], "ftrigraphs">, Group<f_Group>,
   HelpText<"Process trigraph sequences">, Flags<[CC1Option]>;
 def fno_trigraphs : Flag<["-"], "fno-trigraphs">, Group<f_Group>,

clang/lib/AST/CMakeLists.txt

@@ -44,6 +44,7 @@ add_clang_library(clangAST
   InheritViz.cpp
   ItaniumCXXABI.cpp
   ItaniumMangle.cpp
+  RecordFieldReorganizer.cpp
   Mangle.cpp
   MicrosoftCXXABI.cpp
   MicrosoftMangle.cpp

clang/lib/AST/DeclBase.cpp

@@ -1257,6 +1257,9 @@ DeclContext::BuildDeclChain(ArrayRef<Decl *> Decls,
     PrevDecl = D;
   }
 
+  // The last one in the chain should have a null next!
+  PrevDecl->NextInContextAndBits.setPointer(nullptr);
+
   return std::make_pair(FirstNewDecl, PrevDecl);
 }