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1 //===- MetaRenamer.cpp - Rename everything with metasyntatic names --------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass renames everything with metasyntatic names. The intent is to use
11 // this pass after bugpoint reduction to conceal the nature of the original
12 // program.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "llvm/Transforms/IPO.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/ADT/SmallString.h"
19 #include "llvm/IR/DerivedTypes.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/IR/Module.h"
22 #include "llvm/IR/Type.h"
23 #include "llvm/IR/TypeFinder.h"
24 #include "llvm/Pass.h"
25 using namespace llvm;
26 
27 namespace {
28 
29   // This PRNG is from the ISO C spec. It is intentionally simple and
30   // unsuitable for cryptographic use. We're just looking for enough
31   // variety to surprise and delight users.
32   struct PRNG {
33     unsigned long next;
34 
srand__anonc79dede60111::PRNG35     void srand(unsigned int seed) {
36       next = seed;
37     }
38 
rand__anonc79dede60111::PRNG39     int rand() {
40       next = next * 1103515245 + 12345;
41       return (unsigned int)(next / 65536) % 32768;
42     }
43   };
44 
45   static const char *const metaNames[] = {
46     // See http://en.wikipedia.org/wiki/Metasyntactic_variable
47     "foo", "bar", "baz", "quux", "barney", "snork", "zot", "blam", "hoge",
48     "wibble", "wobble", "widget", "wombat", "ham", "eggs", "pluto", "spam"
49   };
50 
51   struct Renamer {
Renamer__anonc79dede60111::Renamer52     Renamer(unsigned int seed) {
53       prng.srand(seed);
54     }
55 
newName__anonc79dede60111::Renamer56     const char *newName() {
57       return metaNames[prng.rand() % array_lengthof(metaNames)];
58     }
59 
60     PRNG prng;
61   };
62 
63   struct MetaRenamer : public ModulePass {
64     static char ID; // Pass identification, replacement for typeid
MetaRenamer__anonc79dede60111::MetaRenamer65     MetaRenamer() : ModulePass(ID) {
66       initializeMetaRenamerPass(*PassRegistry::getPassRegistry());
67     }
68 
getAnalysisUsage__anonc79dede60111::MetaRenamer69     void getAnalysisUsage(AnalysisUsage &AU) const override {
70       AU.setPreservesAll();
71     }
72 
runOnModule__anonc79dede60111::MetaRenamer73     bool runOnModule(Module &M) override {
74       // Seed our PRNG with simple additive sum of ModuleID. We're looking to
75       // simply avoid always having the same function names, and we need to
76       // remain deterministic.
77       unsigned int randSeed = 0;
78       for (auto C : M.getModuleIdentifier())
79         randSeed += C;
80 
81       Renamer renamer(randSeed);
82 
83       // Rename all aliases
84       for (auto AI = M.alias_begin(), AE = M.alias_end(); AI != AE; ++AI) {
85         StringRef Name = AI->getName();
86         if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
87           continue;
88 
89         AI->setName("alias");
90       }
91 
92       // Rename all global variables
93       for (auto GI = M.global_begin(), GE = M.global_end(); GI != GE; ++GI) {
94         StringRef Name = GI->getName();
95         if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
96           continue;
97 
98         GI->setName("global");
99       }
100 
101       // Rename all struct types
102       TypeFinder StructTypes;
103       StructTypes.run(M, true);
104       for (StructType *STy : StructTypes) {
105         if (STy->isLiteral() || STy->getName().empty()) continue;
106 
107         SmallString<128> NameStorage;
108         STy->setName((Twine("struct.") +
109           renamer.newName()).toStringRef(NameStorage));
110       }
111 
112       // Rename all functions
113       for (auto &F : M) {
114         StringRef Name = F.getName();
115         if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
116           continue;
117 
118         F.setName(renamer.newName());
119         runOnFunction(F);
120       }
121       return true;
122     }
123 
runOnFunction__anonc79dede60111::MetaRenamer124     bool runOnFunction(Function &F) {
125       for (auto AI = F.arg_begin(), AE = F.arg_end(); AI != AE; ++AI)
126         if (!AI->getType()->isVoidTy())
127           AI->setName("arg");
128 
129       for (auto &BB : F) {
130         BB.setName("bb");
131 
132         for (auto &I : BB)
133           if (!I.getType()->isVoidTy())
134             I.setName("tmp");
135       }
136       return true;
137     }
138   };
139 }
140 
141 char MetaRenamer::ID = 0;
142 INITIALIZE_PASS(MetaRenamer, "metarenamer",
143                 "Assign new names to everything", false, false)
144 //===----------------------------------------------------------------------===//
145 //
146 // MetaRenamer - Rename everything with metasyntactic names.
147 //
createMetaRenamerPass()148 ModulePass *llvm::createMetaRenamerPass() {
149   return new MetaRenamer();
150 }
151