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