1 //===- SymbolRewriter.h - Symbol Rewriting Pass -----------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file provides the prototypes and definitions related to the Symbol 10 // Rewriter pass. 11 // 12 // The Symbol Rewriter pass takes a set of rewrite descriptors which define 13 // transformations for symbol names. These can be either single name to name 14 // trnsformation or more broad regular expression based transformations. 15 // 16 // All the functions are re-written at the IR level. The Symbol Rewriter itself 17 // is exposed as a module level pass. All symbols at the module level are 18 // iterated. For any matching symbol, the requested transformation is applied, 19 // updating references to it as well (a la RAUW). The resulting binary will 20 // only contain the rewritten symbols. 21 // 22 // By performing this operation in the compiler, we are able to catch symbols 23 // that would otherwise not be possible to catch (e.g. inlined symbols). 24 // 25 // This makes it possible to cleanly transform symbols without resorting to 26 // overly-complex macro tricks and the pre-processor. An example of where this 27 // is useful is the sanitizers where we would like to intercept a well-defined 28 // set of functions across the module. 29 // 30 //===----------------------------------------------------------------------===// 31 32 #ifndef LLVM_TRANSFORMS_UTILS_SYMBOLREWRITER_H 33 #define LLVM_TRANSFORMS_UTILS_SYMBOLREWRITER_H 34 35 #include "llvm/IR/PassManager.h" 36 #include <list> 37 #include <memory> 38 #include <string> 39 40 namespace llvm { 41 42 class MemoryBuffer; 43 class Module; 44 45 namespace yaml { 46 47 class KeyValueNode; 48 class MappingNode; 49 class ScalarNode; 50 class Stream; 51 52 } // end namespace yaml 53 54 namespace SymbolRewriter { 55 56 /// The basic entity representing a rewrite operation. It serves as the base 57 /// class for any rewrite descriptor. It has a certain set of specializations 58 /// which describe a particular rewrite. 59 /// 60 /// The RewriteMapParser can be used to parse a mapping file that provides the 61 /// mapping for rewriting the symbols. The descriptors individually describe 62 /// whether to rewrite a function, global variable, or global alias. Each of 63 /// these can be selected either by explicitly providing a name for the ones to 64 /// be rewritten or providing a (posix compatible) regular expression that will 65 /// select the symbols to rewrite. This descriptor list is passed to the 66 /// SymbolRewriter pass. 67 class RewriteDescriptor { 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 RewriteDescriptor(const RewriteDescriptor &) = delete; 77 RewriteDescriptor &operator=(const RewriteDescriptor &) = delete; 78 virtual ~RewriteDescriptor() = default; 79 80 Type getType() const { return Kind; } 81 82 virtual bool performOnModule(Module &M) = 0; 83 84 protected: 85 explicit RewriteDescriptor(Type T) : Kind(T) {} 86 87 private: 88 const Type Kind; 89 }; 90 91 using RewriteDescriptorList = std::list<std::unique_ptr<RewriteDescriptor>>; 92 93 class RewriteMapParser { 94 public: 95 bool parse(const std::string &MapFile, RewriteDescriptorList *Descriptors); 96 97 private: 98 bool parse(std::unique_ptr<MemoryBuffer> &MapFile, RewriteDescriptorList *DL); 99 bool parseEntry(yaml::Stream &Stream, yaml::KeyValueNode &Entry, 100 RewriteDescriptorList *DL); 101 bool parseRewriteFunctionDescriptor(yaml::Stream &Stream, 102 yaml::ScalarNode *Key, 103 yaml::MappingNode *Value, 104 RewriteDescriptorList *DL); 105 bool parseRewriteGlobalVariableDescriptor(yaml::Stream &Stream, 106 yaml::ScalarNode *Key, 107 yaml::MappingNode *Value, 108 RewriteDescriptorList *DL); 109 bool parseRewriteGlobalAliasDescriptor(yaml::Stream &YS, yaml::ScalarNode *K, 110 yaml::MappingNode *V, 111 RewriteDescriptorList *DL); 112 }; 113 114 } // end namespace SymbolRewriter 115 116 class RewriteSymbolPass : public PassInfoMixin<RewriteSymbolPass> { 117 public: 118 RewriteSymbolPass() { loadAndParseMapFiles(); } 119 120 RewriteSymbolPass(SymbolRewriter::RewriteDescriptorList &DL) { 121 Descriptors.splice(Descriptors.begin(), DL); 122 } 123 124 PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM); 125 126 // Glue for old PM 127 bool runImpl(Module &M); 128 129 private: 130 void loadAndParseMapFiles(); 131 132 SymbolRewriter::RewriteDescriptorList Descriptors; 133 }; 134 135 } // end namespace llvm 136 137 #endif // LLVM_TRANSFORMS_UTILS_SYMBOLREWRITER_H 138