Revert D121556 "[randstruct] Add randomize structure layout support"

This reverts commit 3f0587d.

Not all tests pass after a few rounds of fixes.

I spot one failure that std::shuffle (potentially different results with
different STL implementations) was misused and replaced it with llvm::shuffle,
but there appears to be another failure in a Windows build.

The latest failure is reported on https://reviews.llvm.org/D121556#3440383

Author: MaskRay

clang/docs/ReleaseNotes.rst

@@ -54,20 +54,6 @@ Major New Features
   There is an analogous ``zero_call_used_regs`` attribute to allow for finer
   control of this feature.
 
-- Clang now supports randomizing structure layout in C. This feature is a
-  compile-time hardening technique, making it more difficult for an attacker to
-  retrieve data from structures. Specify randomization with the
-  ``randomize_layout`` attribute. The corresponding ``no_randomize_layout``
-  attribute can be used to turn the feature off.
-
-  A seed value is required to enable randomization, and is deterministic based
-  on a seed value. Use the ``-frandomize-layout-seed=`` or
-  ``-frandomize-layout-seed-file=`` flags.
-
-  .. note::
-
-      Randomizing structure layout is a C-only feature.
-
 Bug Fixes
 ------------------
 - ``CXXNewExpr::getArraySize()`` previously returned a ``llvm::Optional``

clang/include/clang/AST/Decl.h

@@ -4051,12 +4051,6 @@ class RecordDecl : public TagDecl {
     RecordDeclBits.ParamDestroyedInCallee = V;
   }
 
-  bool isRandomized() const { return RecordDeclBits.IsRandomized; }
-
-  void setIsRandomized(bool V) { RecordDeclBits.IsRandomized = V; }
-
-  void reorderFields(const SmallVectorImpl<Decl *> &Fields);
-
   /// Determines whether this declaration represents the
   /// injected class name.
   ///

clang/include/clang/AST/DeclBase.h

@@ -313,7 +313,6 @@ class alignas(8) Decl {
   friend class ASTReader;
   friend class CXXClassMemberWrapper;
   friend class LinkageComputer;
-  friend class RecordDecl;
   template<typename decl_type> friend class Redeclarable;
 
   /// Access - Used by C++ decls for the access specifier.
@@ -1541,13 +1540,10 @@ class DeclContext {
 
     /// Represents the way this type is passed to a function.
     uint64_t ArgPassingRestrictions : 2;
-
-    /// Indicates whether this struct has had its field layout randomized.
-    uint64_t IsRandomized : 1;
   };
 
   /// Number of non-inherited bits in RecordDeclBitfields.
-  enum { NumRecordDeclBits = 15 };
+  enum { NumRecordDeclBits = 14 };
 
   /// Stores the bits used by OMPDeclareReductionDecl.
   /// If modified NumOMPDeclareReductionDeclBits and the accessor

clang/include/clang/AST/Randstruct.h

@@ -3957,18 +3957,3 @@ def HLSLNumThreads: InheritableAttr {
   let LangOpts = [HLSL];
   let Documentation = [NumThreadsDocs];
 }
-
-def RandomizeLayout : InheritableAttr {
-  let Spellings = [GCC<"randomize_layout">];
-  let Subjects = SubjectList<[Record]>;
-  let Documentation = [ClangRandomizeLayoutDocs];
-  let LangOpts = [COnly];
-}
-
-def NoRandomizeLayout : InheritableAttr {
-  let Spellings = [GCC<"no_randomize_layout">];
-  let Subjects = SubjectList<[Record]>;
-  let Documentation = [ClangRandomizeLayoutDocs];
-  let LangOpts = [COnly];
-}
-def : MutualExclusions<[RandomizeLayout, NoRandomizeLayout]>;

clang/include/clang/Basic/Attr.td

@@ -6379,35 +6379,3 @@ dictate the thread id. Total number of threads executed is ``X * Y * Z``.
 The full documentation is available here: https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/sm5-attributes-numthreads
   }];
 }
-
-def ClangRandomizeLayoutDocs : Documentation {
-  let Category = DocCatDecl;
-  let Heading = "randomize_layout, no_randomize_layout";
-  let Content = [{
-The attribute ``randomize_layout``, when attached to a C structure, selects it
-for structure layout field randomization; a compile-time hardening technique. A
-"seed" value, is specified via the ``-frandomize-layout-seed=`` command line flag.
-For example:
-
-.. code-block:: bash
-
-  SEED=`od -A n -t x8 -N 32 /dev/urandom | tr -d ' \n'`
-  make ... CFLAGS="-frandomize-layout-seed=$SEED" ...
-
-You can also supply the seed in a file with ``-frandomize-layout-seed-file=``.
-For example:
-
-.. code-block:: bash
-
-  od -A n -t x8 -N 32 /dev/urandom | tr -d ' \n' > /tmp/seed_file.txt
-  make ... CFLAGS="-frandomize-layout-seed-file=/tmp/seed_file.txt" ...
-
-The randomization is deterministic based for a given seed, so the entire
-program should be compiled with the same seed, but keep the seed safe
-otherwise.
-
-The attribute ``no_randomize_layout``, when attached to a C structure,
-instructs the compiler that this structure should not have its field layout
-randomized.
-  }];
-}

clang/include/clang/Basic/AttrDocs.td

@@ -165,8 +165,6 @@ def err_drv_amdgpu_ieee_without_no_honor_nans : Error<
   "invalid argument '-mno-amdgpu-ieee' only allowed with relaxed NaN handling">;
 def err_drv_argument_not_allowed_with : Error<
   "invalid argument '%0' not allowed with '%1'">;
-def err_drv_cannot_open_randomize_layout_seed_file : Error<
-  "cannot read randomize layout seed file '%0'">;
 def err_drv_invalid_version_number : Error<
   "invalid version number in '%0'">;
 def err_drv_no_linker_llvm_support : Error<

clang/include/clang/Basic/DiagnosticDriverKinds.td

@@ -11588,7 +11588,5 @@ def err_hlsl_numthreads_argument_oor : Error<"argument '%select{X|Y|Z}0' to numt
 def err_hlsl_numthreads_invalid : Error<"total number of threads cannot exceed %0">;
 def err_hlsl_attribute_param_mismatch : Error<"%0 attribute parameters do not match the previous declaration">;
 
-// Layout randomization warning.
-def err_cast_from_randomized_struct : Error<
-  "casting from randomized structure pointer type %0 to %1">;
 } // end of sema component.
+

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -445,9 +445,6 @@ class LangOptions : public LangOptionsBase {
   /// The default stream kind used for HIP kernel launching.
   GPUDefaultStreamKind GPUDefaultStream;
 
-  /// The seed used by the randomize structure layout feature.
-  std::string RandstructSeed;
-
   LangOptions();
 
   // Define accessors/mutators for language options of enumeration type.

clang/include/clang/Basic/LangOptions.h

@@ -2122,12 +2122,6 @@ defm merge_all_constants : BoolFOption<"merge-all-constants",
 def fmessage_length_EQ : Joined<["-"], "fmessage-length=">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Format message diagnostics so that they fit within N columns">,
   MarshallingInfoInt<DiagnosticOpts<"MessageLength">>;
-def frandomize_layout_seed_EQ : Joined<["-"], "frandomize-layout-seed=">,
-  MetaVarName<"<seed>">, Group<f_clang_Group>, Flags<[CC1Option]>,
-  HelpText<"The seed used by the randomize structure layout feature">;
-def frandomize_layout_seed_file_EQ : Joined<["-"], "frandomize-layout-seed-file=">,
-  MetaVarName<"<file>">, Group<f_clang_Group>, Flags<[CC1Option]>,
-  HelpText<"File holding the seed used by the randomize structure layout feature">;
 def fms_compatibility : Flag<["-"], "fms-compatibility">, Group<f_Group>, Flags<[CC1Option, CoreOption]>,
   HelpText<"Enable full Microsoft Visual C++ compatibility">,
   MarshallingInfoFlag<LangOpts<"MSVCCompat">>;