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;
44
45namespace yaml {
46
47class KeyValueNode;
48class MappingNode;
49class ScalarNode;
50class Stream;
51
52} // end namespace yaml
53
54namespace 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.
67class RewriteDescriptor {
68public:
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
84protected:
85  explicit RewriteDescriptor(Type T) : Kind(T) {}
86
87private:
88  const Type Kind;
89};
90
91using RewriteDescriptorList = std::list<std::unique_ptr<RewriteDescriptor>>;
92
93class RewriteMapParser {
94public:
95  bool parse(const std::string &MapFile, RewriteDescriptorList *Descriptors);
96
97private:
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
116class RewriteSymbolPass : public PassInfoMixin<RewriteSymbolPass> {
117public:
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
129private:
130  void loadAndParseMapFiles();
131
132  SymbolRewriter::RewriteDescriptorList Descriptors;
133};
134
135} // end namespace llvm
136
137#endif // LLVM_TRANSFORMS_UTILS_SYMBOLREWRITER_H
138