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 40namespace llvm { 41 42class MemoryBuffer; 43class Module; 44class ModulePass; 45 46namespace yaml { 47 48class KeyValueNode; 49class MappingNode; 50class ScalarNode; 51class Stream; 52 53} // end namespace yaml 54 55namespace SymbolRewriter { 56 57/// The basic entity representing a rewrite operation. It serves as the base 58/// class for any rewrite descriptor. It has a certain set of specializations 59/// which describe a particular rewrite. 60/// 61/// The RewriteMapParser can be used to parse a mapping file that provides the 62/// mapping for rewriting the symbols. The descriptors individually describe 63/// whether to rewrite a function, global variable, or global alias. Each of 64/// these can be selected either by explicitly providing a name for the ones to 65/// be rewritten or providing a (posix compatible) regular expression that will 66/// select the symbols to rewrite. This descriptor list is passed to the 67/// SymbolRewriter pass. 68class RewriteDescriptor { 69public: 70 enum class Type { 71 Invalid, /// invalid 72 Function, /// function - descriptor rewrites a function 73 GlobalVariable, /// global variable - descriptor rewrites a global variable 74 NamedAlias, /// named alias - descriptor rewrites a global alias 75 }; 76 77 RewriteDescriptor(const RewriteDescriptor &) = delete; 78 RewriteDescriptor &operator=(const RewriteDescriptor &) = delete; 79 virtual ~RewriteDescriptor() = default; 80 81 Type getType() const { return Kind; } 82 83 virtual bool performOnModule(Module &M) = 0; 84 85protected: 86 explicit RewriteDescriptor(Type T) : Kind(T) {} 87 88private: 89 const Type Kind; 90}; 91 92using RewriteDescriptorList = std::list<std::unique_ptr<RewriteDescriptor>>; 93 94class RewriteMapParser { 95public: 96 bool parse(const std::string &MapFile, RewriteDescriptorList *Descriptors); 97 98private: 99 bool parse(std::unique_ptr<MemoryBuffer> &MapFile, RewriteDescriptorList *DL); 100 bool parseEntry(yaml::Stream &Stream, yaml::KeyValueNode &Entry, 101 RewriteDescriptorList *DL); 102 bool parseRewriteFunctionDescriptor(yaml::Stream &Stream, 103 yaml::ScalarNode *Key, 104 yaml::MappingNode *Value, 105 RewriteDescriptorList *DL); 106 bool parseRewriteGlobalVariableDescriptor(yaml::Stream &Stream, 107 yaml::ScalarNode *Key, 108 yaml::MappingNode *Value, 109 RewriteDescriptorList *DL); 110 bool parseRewriteGlobalAliasDescriptor(yaml::Stream &YS, yaml::ScalarNode *K, 111 yaml::MappingNode *V, 112 RewriteDescriptorList *DL); 113}; 114 115} // end namespace SymbolRewriter 116 117ModulePass *createRewriteSymbolsPass(); 118ModulePass *createRewriteSymbolsPass(SymbolRewriter::RewriteDescriptorList &); 119 120class RewriteSymbolPass : public PassInfoMixin<RewriteSymbolPass> { 121public: 122 RewriteSymbolPass() { loadAndParseMapFiles(); } 123 124 RewriteSymbolPass(SymbolRewriter::RewriteDescriptorList &DL) { 125 Descriptors.splice(Descriptors.begin(), DL); 126 } 127 128 PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM); 129 130 // Glue for old PM 131 bool runImpl(Module &M); 132 133private: 134 void loadAndParseMapFiles(); 135 136 SymbolRewriter::RewriteDescriptorList Descriptors; 137}; 138 139} // end namespace llvm 140 141#endif //LLVM_TRANSFORMS_UTILS_SYMBOLREWRITER_H 142