1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
|
//===- StripSymbols.cpp - Strip symbols and debug info from a module ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// The StripSymbols transformation implements code stripping. Specifically, it
// can delete:
//
// * names for virtual registers
// * symbols for internal globals and functions
// * debug information
//
// Note that this transformation makes code much less readable, so it should
// only be used in situations where the 'strip' utility would be used, such as
// reducing code size or making it harder to reverse engineer code.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/ValueSymbolTable.h"
#include "llvm/TypeSymbolTable.h"
#include "llvm/Support/Compiler.h"
#include "llvm/ADT/SmallPtrSet.h"
using namespace llvm;
namespace {
class VISIBILITY_HIDDEN StripSymbols : public ModulePass {
bool OnlyDebugInfo;
public:
static char ID; // Pass identification, replacement for typeid
explicit StripSymbols(bool ODI = false)
: ModulePass((intptr_t)&ID), OnlyDebugInfo(ODI) {}
virtual bool runOnModule(Module &M);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}
};
}
char StripSymbols::ID = 0;
static RegisterPass<StripSymbols>
X("strip", "Strip all symbols from a module");
ModulePass *llvm::createStripSymbolsPass(bool OnlyDebugInfo) {
return new StripSymbols(OnlyDebugInfo);
}
static void RemoveDeadConstant(Constant *C) {
assert(C->use_empty() && "Constant is not dead!");
std::vector<Constant*> Operands;
for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
if (isa<DerivedType>(C->getOperand(i)->getType()) &&
C->getOperand(i)->hasOneUse())
Operands.push_back(C->getOperand(i));
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
if (!GV->hasInternalLinkage()) return; // Don't delete non static globals.
GV->eraseFromParent();
}
else if (!isa<Function>(C))
C->destroyConstant();
// If the constant referenced anything, see if we can delete it as well.
while (!Operands.empty()) {
RemoveDeadConstant(Operands.back());
Operands.pop_back();
}
}
// Strip the symbol table of its names.
//
static void StripSymtab(ValueSymbolTable &ST) {
for (ValueSymbolTable::iterator VI = ST.begin(), VE = ST.end(); VI != VE; ) {
Value *V = VI->getValue();
++VI;
if (!isa<GlobalValue>(V) || cast<GlobalValue>(V)->hasInternalLinkage()) {
// Set name to "", removing from symbol table!
V->setName("");
}
}
}
// Strip the symbol table of its names.
static void StripTypeSymtab(TypeSymbolTable &ST) {
for (TypeSymbolTable::iterator TI = ST.begin(), E = ST.end(); TI != E; )
ST.remove(TI++);
}
bool StripSymbols::runOnModule(Module &M) {
// If we're not just stripping debug info, strip all symbols from the
// functions and the names from any internal globals.
if (!OnlyDebugInfo) {
SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
if (GlobalVariable *LLVMUsed = M.getGlobalVariable("llvm.used")) {
llvmUsedValues.insert(LLVMUsed);
// Collect values that are preserved as per explicit request.
// llvm.used is used to list these values.
if (ConstantArray *Inits =
dyn_cast<ConstantArray>(LLVMUsed->getInitializer())) {
for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i) {
if (GlobalValue *GV = dyn_cast<GlobalValue>(Inits->getOperand(i)))
llvmUsedValues.insert(GV);
else if (ConstantExpr *CE =
dyn_cast<ConstantExpr>(Inits->getOperand(i)))
if (CE->getOpcode() == Instruction::BitCast)
if (GlobalValue *GV = dyn_cast<GlobalValue>(CE->getOperand(0)))
llvmUsedValues.insert(GV);
}
}
}
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I) {
if (I->hasInternalLinkage() && llvmUsedValues.count(I) == 0)
I->setName(""); // Internal symbols can't participate in linkage
}
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
if (I->hasInternalLinkage() && llvmUsedValues.count(I) == 0)
I->setName(""); // Internal symbols can't participate in linkage
StripSymtab(I->getValueSymbolTable());
}
// Remove all names from types.
StripTypeSymtab(M.getTypeSymbolTable());
}
// Strip debug info in the module if it exists. To do this, we remove
// llvm.dbg.func.start, llvm.dbg.stoppoint, and llvm.dbg.region.end calls, and
// any globals they point to if now dead.
Function *FuncStart = M.getFunction("llvm.dbg.func.start");
Function *StopPoint = M.getFunction("llvm.dbg.stoppoint");
Function *RegionStart = M.getFunction("llvm.dbg.region.start");
Function *RegionEnd = M.getFunction("llvm.dbg.region.end");
Function *Declare = M.getFunction("llvm.dbg.declare");
if (!FuncStart && !StopPoint && !RegionStart && !RegionEnd && !Declare)
return true;
std::vector<GlobalVariable*> DeadGlobals;
// Remove all of the calls to the debugger intrinsics, and remove them from
// the module.
if (FuncStart) {
while (!FuncStart->use_empty()) {
CallInst *CI = cast<CallInst>(FuncStart->use_back());
Value *Arg = CI->getOperand(1);
assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
CI->eraseFromParent();
if (Arg->use_empty())
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Arg))
DeadGlobals.push_back(GV);
}
FuncStart->eraseFromParent();
}
if (StopPoint) {
while (!StopPoint->use_empty()) {
CallInst *CI = cast<CallInst>(StopPoint->use_back());
Value *Arg = CI->getOperand(3);
assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
CI->eraseFromParent();
if (Arg->use_empty())
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Arg))
DeadGlobals.push_back(GV);
}
StopPoint->eraseFromParent();
}
if (RegionStart) {
while (!RegionStart->use_empty()) {
CallInst *CI = cast<CallInst>(RegionStart->use_back());
Value *Arg = CI->getOperand(1);
assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
CI->eraseFromParent();
if (Arg->use_empty())
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Arg))
DeadGlobals.push_back(GV);
}
RegionStart->eraseFromParent();
}
if (RegionEnd) {
while (!RegionEnd->use_empty()) {
CallInst *CI = cast<CallInst>(RegionEnd->use_back());
Value *Arg = CI->getOperand(1);
assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
CI->eraseFromParent();
if (Arg->use_empty())
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Arg))
DeadGlobals.push_back(GV);
}
RegionEnd->eraseFromParent();
}
if (Declare) {
while (!Declare->use_empty()) {
CallInst *CI = cast<CallInst>(Declare->use_back());
Value *Arg = CI->getOperand(2);
assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
CI->eraseFromParent();
if (Arg->use_empty())
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Arg))
DeadGlobals.push_back(GV);
}
Declare->eraseFromParent();
}
// Finally, delete any internal globals that were only used by the debugger
// intrinsics.
while (!DeadGlobals.empty()) {
GlobalVariable *GV = DeadGlobals.back();
DeadGlobals.pop_back();
if (GV->hasInternalLinkage())
RemoveDeadConstant(GV);
}
return true;
}
|
