1 //===-- SymbolRewriter.h - Symbol Rewriting Pass ----------------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file provides the prototypes and definitions related to the Symbol 11 // Rewriter pass. 12 // 13 // The Symbol Rewriter pass takes a set of rewrite descriptors which define 14 // transformations for symbol names. These can be either single name to name 15 // trnsformation or more broad regular expression based transformations. 16 // 17 // All the functions are re-written at the IR level. The Symbol Rewriter itself 18 // is exposed as a module level pass. All symbols at the module level are 19 // iterated. For any matching symbol, the requested transformation is applied, 20 // updating references to it as well (a la RAUW). The resulting binary will 21 // only contain the rewritten symbols. 22 // 23 // By performing this operation in the compiler, we are able to catch symbols 24 // that would otherwise not be possible to catch (e.g. inlined symbols). 25 // 26 // This makes it possible to cleanly transform symbols without resorting to 27 // overly-complex macro tricks and the pre-processor. An example of where this 28 // is useful is the sanitizers where we would like to intercept a well-defined 29 // set of functions across the module. 30 // 31 //===----------------------------------------------------------------------===// 32 33 #ifndef LLVM_TRANSFORMS_UTILS_SYMBOL_REWRITER_H 34 #define LLVM_TRANSFORMS_UTILS_SYMBOL_REWRITER_H 35 36 #include "llvm/ADT/ilist.h" 37 #include "llvm/ADT/ilist_node.h" 38 #include "llvm/IR/Module.h" 39 40 namespace llvm { 41 class MemoryBuffer; 42 43 namespace yaml { 44 class KeyValueNode; 45 class MappingNode; 46 class ScalarNode; 47 class Stream; 48 } 49 50 namespace SymbolRewriter { 51 /// The basic entity representing a rewrite operation. It serves as the base 52 /// class for any rewrite descriptor. It has a certain set of specializations 53 /// which describe a particular rewrite. 54 /// 55 /// The RewriteMapParser can be used to parse a mapping file that provides the 56 /// mapping for rewriting the symbols. The descriptors individually describe 57 /// whether to rewrite a function, global variable, or global alias. Each of 58 /// these can be selected either by explicitly providing a name for the ones to 59 /// be rewritten or providing a (posix compatible) regular expression that will 60 /// select the symbols to rewrite. This descriptor list is passed to the 61 /// SymbolRewriter pass. 62 class RewriteDescriptor : public ilist_node<RewriteDescriptor> { 63 RewriteDescriptor(const RewriteDescriptor &) = delete; 64 65 const RewriteDescriptor & 66 operator=(const RewriteDescriptor &) = delete; 67 68 public: 69 enum class Type { 70 Invalid, /// invalid 71 Function, /// function - descriptor rewrites a function 72 GlobalVariable, /// global variable - descriptor rewrites a global variable 73 NamedAlias, /// named alias - descriptor rewrites a global alias 74 }; 75 76 virtual ~RewriteDescriptor() {} 77 78 Type getType() const { return Kind; } 79 80 virtual bool performOnModule(Module &M) = 0; 81 82 protected: 83 explicit RewriteDescriptor(Type T) : Kind(T) {} 84 85 private: 86 const Type Kind; 87 }; 88 89 typedef iplist<RewriteDescriptor> RewriteDescriptorList; 90 91 class RewriteMapParser { 92 public: 93 bool parse(const std::string &MapFile, RewriteDescriptorList *Descriptors); 94 95 private: 96 bool parse(std::unique_ptr<MemoryBuffer> &MapFile, RewriteDescriptorList *DL); 97 bool parseEntry(yaml::Stream &Stream, yaml::KeyValueNode &Entry, 98 RewriteDescriptorList *DL); 99 bool parseRewriteFunctionDescriptor(yaml::Stream &Stream, 100 yaml::ScalarNode *Key, 101 yaml::MappingNode *Value, 102 RewriteDescriptorList *DL); 103 bool parseRewriteGlobalVariableDescriptor(yaml::Stream &Stream, 104 yaml::ScalarNode *Key, 105 yaml::MappingNode *Value, 106 RewriteDescriptorList *DL); 107 bool parseRewriteGlobalAliasDescriptor(yaml::Stream &YS, yaml::ScalarNode *K, 108 yaml::MappingNode *V, 109 RewriteDescriptorList *DL); 110 }; 111 } 112 113 template <> 114 struct ilist_traits<SymbolRewriter::RewriteDescriptor> 115 : public ilist_default_traits<SymbolRewriter::RewriteDescriptor> { 116 mutable ilist_half_node<SymbolRewriter::RewriteDescriptor> Sentinel; 117 118 public: 119 // createSentinel is used to get a reference to a node marking the end of 120 // the list. Because the sentinel is relative to this instance, use a 121 // non-static method. 122 SymbolRewriter::RewriteDescriptor *createSentinel() const { 123 // since i[p] lists always publicly derive from the corresponding 124 // traits, placing a data member in this class will augment the 125 // i[p]list. Since the NodeTy is expected to publicly derive from 126 // ilist_node<NodeTy>, there is a legal viable downcast from it to 127 // NodeTy. We use this trick to superpose i[p]list with a "ghostly" 128 // NodeTy, which becomes the sentinel. Dereferencing the sentinel is 129 // forbidden (save the ilist_node<NodeTy>) so no one will ever notice 130 // the superposition. 131 return static_cast<SymbolRewriter::RewriteDescriptor *>(&Sentinel); 132 } 133 void destroySentinel(SymbolRewriter::RewriteDescriptor *) {} 134 135 SymbolRewriter::RewriteDescriptor *provideInitialHead() const { 136 return createSentinel(); 137 } 138 139 SymbolRewriter::RewriteDescriptor * 140 ensureHead(SymbolRewriter::RewriteDescriptor *&) const { 141 return createSentinel(); 142 } 143 144 static void noteHead(SymbolRewriter::RewriteDescriptor *, 145 SymbolRewriter::RewriteDescriptor *) {} 146 }; 147 148 ModulePass *createRewriteSymbolsPass(); 149 ModulePass *createRewriteSymbolsPass(SymbolRewriter::RewriteDescriptorList &); 150 } 151 152 #endif 153
