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 
getType()80   Type getType() const { return Kind; }
81 
82   virtual bool performOnModule(Module &M) = 0;
83 
84 protected:
RewriteDescriptor(Type T)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:
RewriteSymbolPass()118   RewriteSymbolPass() { loadAndParseMapFiles(); }
119 
RewriteSymbolPass(SymbolRewriter::RewriteDescriptorList & DL)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