Bug Summary

File:lib/CodeGen/SafeStack.cpp
Warning:line 592, column 7
Value stored to 'Size' is never read

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name SafeStack.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-8/lib/clang/8.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-8~svn350071/build-llvm/lib/CodeGen -I /build/llvm-toolchain-snapshot-8~svn350071/lib/CodeGen -I /build/llvm-toolchain-snapshot-8~svn350071/build-llvm/include -I /build/llvm-toolchain-snapshot-8~svn350071/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/include/clang/8.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-8/lib/clang/8.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-8~svn350071/build-llvm/lib/CodeGen -fdebug-prefix-map=/build/llvm-toolchain-snapshot-8~svn350071=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2018-12-27-042839-1215-1 -x c++ /build/llvm-toolchain-snapshot-8~svn350071/lib/CodeGen/SafeStack.cpp -faddrsig
1//===- SafeStack.cpp - Safe Stack Insertion -------------------------------===//
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 splits the stack into the safe stack (kept as-is for LLVM backend)
11// and the unsafe stack (explicitly allocated and managed through the runtime
12// support library).
13//
14// http://clang.llvm.org/docs/SafeStack.html
15//
16//===----------------------------------------------------------------------===//
17
18#include "SafeStackColoring.h"
19#include "SafeStackLayout.h"
20#include "llvm/ADT/APInt.h"
21#include "llvm/ADT/ArrayRef.h"
22#include "llvm/ADT/SmallPtrSet.h"
23#include "llvm/ADT/SmallVector.h"
24#include "llvm/ADT/Statistic.h"
25#include "llvm/Analysis/AssumptionCache.h"
26#include "llvm/Analysis/BranchProbabilityInfo.h"
27#include "llvm/Analysis/InlineCost.h"
28#include "llvm/Analysis/LoopInfo.h"
29#include "llvm/Analysis/ScalarEvolution.h"
30#include "llvm/Analysis/ScalarEvolutionExpressions.h"
31#include "llvm/Analysis/TargetLibraryInfo.h"
32#include "llvm/Transforms/Utils/Local.h"
33#include "llvm/CodeGen/TargetLowering.h"
34#include "llvm/CodeGen/TargetPassConfig.h"
35#include "llvm/CodeGen/TargetSubtargetInfo.h"
36#include "llvm/IR/Argument.h"
37#include "llvm/IR/Attributes.h"
38#include "llvm/IR/CallSite.h"
39#include "llvm/IR/ConstantRange.h"
40#include "llvm/IR/Constants.h"
41#include "llvm/IR/DIBuilder.h"
42#include "llvm/IR/DataLayout.h"
43#include "llvm/IR/DerivedTypes.h"
44#include "llvm/IR/Dominators.h"
45#include "llvm/IR/Function.h"
46#include "llvm/IR/IRBuilder.h"
47#include "llvm/IR/InstIterator.h"
48#include "llvm/IR/Instruction.h"
49#include "llvm/IR/Instructions.h"
50#include "llvm/IR/IntrinsicInst.h"
51#include "llvm/IR/Intrinsics.h"
52#include "llvm/IR/MDBuilder.h"
53#include "llvm/IR/Module.h"
54#include "llvm/IR/Type.h"
55#include "llvm/IR/Use.h"
56#include "llvm/IR/User.h"
57#include "llvm/IR/Value.h"
58#include "llvm/Pass.h"
59#include "llvm/Support/Casting.h"
60#include "llvm/Support/Debug.h"
61#include "llvm/Support/ErrorHandling.h"
62#include "llvm/Support/MathExtras.h"
63#include "llvm/Support/raw_ostream.h"
64#include "llvm/Target/TargetMachine.h"
65#include "llvm/Transforms/Utils/BasicBlockUtils.h"
66#include "llvm/Transforms/Utils/Cloning.h"
67#include <algorithm>
68#include <cassert>
69#include <cstdint>
70#include <string>
71#include <utility>
72
73using namespace llvm;
74using namespace llvm::safestack;
75
76#define DEBUG_TYPE"safe-stack" "safe-stack"
77
78namespace llvm {
79
80STATISTIC(NumFunctions, "Total number of functions")static llvm::Statistic NumFunctions = {"safe-stack", "NumFunctions"
, "Total number of functions", {0}, {false}}
;
81STATISTIC(NumUnsafeStackFunctions, "Number of functions with unsafe stack")static llvm::Statistic NumUnsafeStackFunctions = {"safe-stack"
, "NumUnsafeStackFunctions", "Number of functions with unsafe stack"
, {0}, {false}}
;
82STATISTIC(NumUnsafeStackRestorePointsFunctions,static llvm::Statistic NumUnsafeStackRestorePointsFunctions =
{"safe-stack", "NumUnsafeStackRestorePointsFunctions", "Number of functions that use setjmp or exceptions"
, {0}, {false}}
83 "Number of functions that use setjmp or exceptions")static llvm::Statistic NumUnsafeStackRestorePointsFunctions =
{"safe-stack", "NumUnsafeStackRestorePointsFunctions", "Number of functions that use setjmp or exceptions"
, {0}, {false}}
;
84
85STATISTIC(NumAllocas, "Total number of allocas")static llvm::Statistic NumAllocas = {"safe-stack", "NumAllocas"
, "Total number of allocas", {0}, {false}}
;
86STATISTIC(NumUnsafeStaticAllocas, "Number of unsafe static allocas")static llvm::Statistic NumUnsafeStaticAllocas = {"safe-stack"
, "NumUnsafeStaticAllocas", "Number of unsafe static allocas"
, {0}, {false}}
;
87STATISTIC(NumUnsafeDynamicAllocas, "Number of unsafe dynamic allocas")static llvm::Statistic NumUnsafeDynamicAllocas = {"safe-stack"
, "NumUnsafeDynamicAllocas", "Number of unsafe dynamic allocas"
, {0}, {false}}
;
88STATISTIC(NumUnsafeByValArguments, "Number of unsafe byval arguments")static llvm::Statistic NumUnsafeByValArguments = {"safe-stack"
, "NumUnsafeByValArguments", "Number of unsafe byval arguments"
, {0}, {false}}
;
89STATISTIC(NumUnsafeStackRestorePoints, "Number of setjmps and landingpads")static llvm::Statistic NumUnsafeStackRestorePoints = {"safe-stack"
, "NumUnsafeStackRestorePoints", "Number of setjmps and landingpads"
, {0}, {false}}
;
90
91} // namespace llvm
92
93/// Use __safestack_pointer_address even if the platform has a faster way of
94/// access safe stack pointer.
95static cl::opt<bool>
96 SafeStackUsePointerAddress("safestack-use-pointer-address",
97 cl::init(false), cl::Hidden);
98
99
100namespace {
101
102/// Rewrite an SCEV expression for a memory access address to an expression that
103/// represents offset from the given alloca.
104///
105/// The implementation simply replaces all mentions of the alloca with zero.
106class AllocaOffsetRewriter : public SCEVRewriteVisitor<AllocaOffsetRewriter> {
107 const Value *AllocaPtr;
108
109public:
110 AllocaOffsetRewriter(ScalarEvolution &SE, const Value *AllocaPtr)
111 : SCEVRewriteVisitor(SE), AllocaPtr(AllocaPtr) {}
112
113 const SCEV *visitUnknown(const SCEVUnknown *Expr) {
114 if (Expr->getValue() == AllocaPtr)
115 return SE.getZero(Expr->getType());
116 return Expr;
117 }
118};
119
120/// The SafeStack pass splits the stack of each function into the safe
121/// stack, which is only accessed through memory safe dereferences (as
122/// determined statically), and the unsafe stack, which contains all
123/// local variables that are accessed in ways that we can't prove to
124/// be safe.
125class SafeStack {
126 Function &F;
127 const TargetLoweringBase &TL;
128 const DataLayout &DL;
129 ScalarEvolution &SE;
130
131 Type *StackPtrTy;
132 Type *IntPtrTy;
133 Type *Int32Ty;
134 Type *Int8Ty;
135
136 Value *UnsafeStackPtr = nullptr;
137
138 /// Unsafe stack alignment. Each stack frame must ensure that the stack is
139 /// aligned to this value. We need to re-align the unsafe stack if the
140 /// alignment of any object on the stack exceeds this value.
141 ///
142 /// 16 seems like a reasonable upper bound on the alignment of objects that we
143 /// might expect to appear on the stack on most common targets.
144 enum { StackAlignment = 16 };
145
146 /// Return the value of the stack canary.
147 Value *getStackGuard(IRBuilder<> &IRB, Function &F);
148
149 /// Load stack guard from the frame and check if it has changed.
150 void checkStackGuard(IRBuilder<> &IRB, Function &F, ReturnInst &RI,
151 AllocaInst *StackGuardSlot, Value *StackGuard);
152
153 /// Find all static allocas, dynamic allocas, return instructions and
154 /// stack restore points (exception unwind blocks and setjmp calls) in the
155 /// given function and append them to the respective vectors.
156 void findInsts(Function &F, SmallVectorImpl<AllocaInst *> &StaticAllocas,
157 SmallVectorImpl<AllocaInst *> &DynamicAllocas,
158 SmallVectorImpl<Argument *> &ByValArguments,
159 SmallVectorImpl<ReturnInst *> &Returns,
160 SmallVectorImpl<Instruction *> &StackRestorePoints);
161
162 /// Calculate the allocation size of a given alloca. Returns 0 if the
163 /// size can not be statically determined.
164 uint64_t getStaticAllocaAllocationSize(const AllocaInst* AI);
165
166 /// Allocate space for all static allocas in \p StaticAllocas,
167 /// replace allocas with pointers into the unsafe stack and generate code to
168 /// restore the stack pointer before all return instructions in \p Returns.
169 ///
170 /// \returns A pointer to the top of the unsafe stack after all unsafe static
171 /// allocas are allocated.
172 Value *moveStaticAllocasToUnsafeStack(IRBuilder<> &IRB, Function &F,
173 ArrayRef<AllocaInst *> StaticAllocas,
174 ArrayRef<Argument *> ByValArguments,
175 ArrayRef<ReturnInst *> Returns,
176 Instruction *BasePointer,
177 AllocaInst *StackGuardSlot);
178
179 /// Generate code to restore the stack after all stack restore points
180 /// in \p StackRestorePoints.
181 ///
182 /// \returns A local variable in which to maintain the dynamic top of the
183 /// unsafe stack if needed.
184 AllocaInst *
185 createStackRestorePoints(IRBuilder<> &IRB, Function &F,
186 ArrayRef<Instruction *> StackRestorePoints,
187 Value *StaticTop, bool NeedDynamicTop);
188
189 /// Replace all allocas in \p DynamicAllocas with code to allocate
190 /// space dynamically on the unsafe stack and store the dynamic unsafe stack
191 /// top to \p DynamicTop if non-null.
192 void moveDynamicAllocasToUnsafeStack(Function &F, Value *UnsafeStackPtr,
193 AllocaInst *DynamicTop,
194 ArrayRef<AllocaInst *> DynamicAllocas);
195
196 bool IsSafeStackAlloca(const Value *AllocaPtr, uint64_t AllocaSize);
197
198 bool IsMemIntrinsicSafe(const MemIntrinsic *MI, const Use &U,
199 const Value *AllocaPtr, uint64_t AllocaSize);
200 bool IsAccessSafe(Value *Addr, uint64_t Size, const Value *AllocaPtr,
201 uint64_t AllocaSize);
202
203 bool ShouldInlinePointerAddress(CallSite &CS);
204 void TryInlinePointerAddress();
205
206public:
207 SafeStack(Function &F, const TargetLoweringBase &TL, const DataLayout &DL,
208 ScalarEvolution &SE)
209 : F(F), TL(TL), DL(DL), SE(SE),
210 StackPtrTy(Type::getInt8PtrTy(F.getContext())),
211 IntPtrTy(DL.getIntPtrType(F.getContext())),
212 Int32Ty(Type::getInt32Ty(F.getContext())),
213 Int8Ty(Type::getInt8Ty(F.getContext())) {}
214
215 // Run the transformation on the associated function.
216 // Returns whether the function was changed.
217 bool run();
218};
219
220uint64_t SafeStack::getStaticAllocaAllocationSize(const AllocaInst* AI) {
221 uint64_t Size = DL.getTypeAllocSize(AI->getAllocatedType());
222 if (AI->isArrayAllocation()) {
223 auto C = dyn_cast<ConstantInt>(AI->getArraySize());
224 if (!C)
225 return 0;
226 Size *= C->getZExtValue();
227 }
228 return Size;
229}
230
231bool SafeStack::IsAccessSafe(Value *Addr, uint64_t AccessSize,
232 const Value *AllocaPtr, uint64_t AllocaSize) {
233 AllocaOffsetRewriter Rewriter(SE, AllocaPtr);
234 const SCEV *Expr = Rewriter.visit(SE.getSCEV(Addr));
235
236 uint64_t BitWidth = SE.getTypeSizeInBits(Expr->getType());
237 ConstantRange AccessStartRange = SE.getUnsignedRange(Expr);
238 ConstantRange SizeRange =
239 ConstantRange(APInt(BitWidth, 0), APInt(BitWidth, AccessSize));
240 ConstantRange AccessRange = AccessStartRange.add(SizeRange);
241 ConstantRange AllocaRange =
242 ConstantRange(APInt(BitWidth, 0), APInt(BitWidth, AllocaSize));
243 bool Safe = AllocaRange.contains(AccessRange);
244
245 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] " << (isa
<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
<< *AllocaPtr << "\n" << " Access "
<< *Addr << "\n" << " SCEV " <<
*Expr << " U: " << SE.getUnsignedRange(Expr) <<
", S: " << SE.getSignedRange(Expr) << "\n" <<
" Range " << AccessRange << "\n" <<
" AllocaRange " << AllocaRange << "\n"
<< " " << (Safe ? "safe" : "unsafe") <<
"\n"; } } while (false)
246 dbgs() << "[SafeStack] "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] " << (isa
<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
<< *AllocaPtr << "\n" << " Access "
<< *Addr << "\n" << " SCEV " <<
*Expr << " U: " << SE.getUnsignedRange(Expr) <<
", S: " << SE.getSignedRange(Expr) << "\n" <<
" Range " << AccessRange << "\n" <<
" AllocaRange " << AllocaRange << "\n"
<< " " << (Safe ? "safe" : "unsafe") <<
"\n"; } } while (false)
247 << (isa<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] " << (isa
<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
<< *AllocaPtr << "\n" << " Access "
<< *Addr << "\n" << " SCEV " <<
*Expr << " U: " << SE.getUnsignedRange(Expr) <<
", S: " << SE.getSignedRange(Expr) << "\n" <<
" Range " << AccessRange << "\n" <<
" AllocaRange " << AllocaRange << "\n"
<< " " << (Safe ? "safe" : "unsafe") <<
"\n"; } } while (false)
248 << *AllocaPtr << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] " << (isa
<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
<< *AllocaPtr << "\n" << " Access "
<< *Addr << "\n" << " SCEV " <<
*Expr << " U: " << SE.getUnsignedRange(Expr) <<
", S: " << SE.getSignedRange(Expr) << "\n" <<
" Range " << AccessRange << "\n" <<
" AllocaRange " << AllocaRange << "\n"
<< " " << (Safe ? "safe" : "unsafe") <<
"\n"; } } while (false)
249 << " Access " << *Addr << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] " << (isa
<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
<< *AllocaPtr << "\n" << " Access "
<< *Addr << "\n" << " SCEV " <<
*Expr << " U: " << SE.getUnsignedRange(Expr) <<
", S: " << SE.getSignedRange(Expr) << "\n" <<
" Range " << AccessRange << "\n" <<
" AllocaRange " << AllocaRange << "\n"
<< " " << (Safe ? "safe" : "unsafe") <<
"\n"; } } while (false)
250 << " SCEV " << *Exprdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] " << (isa
<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
<< *AllocaPtr << "\n" << " Access "
<< *Addr << "\n" << " SCEV " <<
*Expr << " U: " << SE.getUnsignedRange(Expr) <<
", S: " << SE.getSignedRange(Expr) << "\n" <<
" Range " << AccessRange << "\n" <<
" AllocaRange " << AllocaRange << "\n"
<< " " << (Safe ? "safe" : "unsafe") <<
"\n"; } } while (false)
251 << " U: " << SE.getUnsignedRange(Expr)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] " << (isa
<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
<< *AllocaPtr << "\n" << " Access "
<< *Addr << "\n" << " SCEV " <<
*Expr << " U: " << SE.getUnsignedRange(Expr) <<
", S: " << SE.getSignedRange(Expr) << "\n" <<
" Range " << AccessRange << "\n" <<
" AllocaRange " << AllocaRange << "\n"
<< " " << (Safe ? "safe" : "unsafe") <<
"\n"; } } while (false)
252 << ", S: " << SE.getSignedRange(Expr) << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] " << (isa
<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
<< *AllocaPtr << "\n" << " Access "
<< *Addr << "\n" << " SCEV " <<
*Expr << " U: " << SE.getUnsignedRange(Expr) <<
", S: " << SE.getSignedRange(Expr) << "\n" <<
" Range " << AccessRange << "\n" <<
" AllocaRange " << AllocaRange << "\n"
<< " " << (Safe ? "safe" : "unsafe") <<
"\n"; } } while (false)
253 << " Range " << AccessRange << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] " << (isa
<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
<< *AllocaPtr << "\n" << " Access "
<< *Addr << "\n" << " SCEV " <<
*Expr << " U: " << SE.getUnsignedRange(Expr) <<
", S: " << SE.getSignedRange(Expr) << "\n" <<
" Range " << AccessRange << "\n" <<
" AllocaRange " << AllocaRange << "\n"
<< " " << (Safe ? "safe" : "unsafe") <<
"\n"; } } while (false)
254 << " AllocaRange " << AllocaRange << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] " << (isa
<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
<< *AllocaPtr << "\n" << " Access "
<< *Addr << "\n" << " SCEV " <<
*Expr << " U: " << SE.getUnsignedRange(Expr) <<
", S: " << SE.getSignedRange(Expr) << "\n" <<
" Range " << AccessRange << "\n" <<
" AllocaRange " << AllocaRange << "\n"
<< " " << (Safe ? "safe" : "unsafe") <<
"\n"; } } while (false)
255 << " " << (Safe ? "safe" : "unsafe") << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] " << (isa
<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
<< *AllocaPtr << "\n" << " Access "
<< *Addr << "\n" << " SCEV " <<
*Expr << " U: " << SE.getUnsignedRange(Expr) <<
", S: " << SE.getSignedRange(Expr) << "\n" <<
" Range " << AccessRange << "\n" <<
" AllocaRange " << AllocaRange << "\n"
<< " " << (Safe ? "safe" : "unsafe") <<
"\n"; } } while (false)
;
256
257 return Safe;
258}
259
260bool SafeStack::IsMemIntrinsicSafe(const MemIntrinsic *MI, const Use &U,
261 const Value *AllocaPtr,
262 uint64_t AllocaSize) {
263 if (auto MTI = dyn_cast<MemTransferInst>(MI)) {
264 if (MTI->getRawSource() != U && MTI->getRawDest() != U)
265 return true;
266 } else {
267 if (MI->getRawDest() != U)
268 return true;
269 }
270
271 const auto *Len = dyn_cast<ConstantInt>(MI->getLength());
272 // Non-constant size => unsafe. FIXME: try SCEV getRange.
273 if (!Len) return false;
274 return IsAccessSafe(U, Len->getZExtValue(), AllocaPtr, AllocaSize);
275}
276
277/// Check whether a given allocation must be put on the safe
278/// stack or not. The function analyzes all uses of AI and checks whether it is
279/// only accessed in a memory safe way (as decided statically).
280bool SafeStack::IsSafeStackAlloca(const Value *AllocaPtr, uint64_t AllocaSize) {
281 // Go through all uses of this alloca and check whether all accesses to the
282 // allocated object are statically known to be memory safe and, hence, the
283 // object can be placed on the safe stack.
284 SmallPtrSet<const Value *, 16> Visited;
285 SmallVector<const Value *, 8> WorkList;
286 WorkList.push_back(AllocaPtr);
287
288 // A DFS search through all uses of the alloca in bitcasts/PHI/GEPs/etc.
289 while (!WorkList.empty()) {
290 const Value *V = WorkList.pop_back_val();
291 for (const Use &UI : V->uses()) {
292 auto I = cast<const Instruction>(UI.getUser());
293 assert(V == UI.get())((V == UI.get()) ? static_cast<void> (0) : __assert_fail
("V == UI.get()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/CodeGen/SafeStack.cpp"
, 293, __PRETTY_FUNCTION__))
;
294
295 switch (I->getOpcode()) {
296 case Instruction::Load:
297 if (!IsAccessSafe(UI, DL.getTypeStoreSize(I->getType()), AllocaPtr,
298 AllocaSize))
299 return false;
300 break;
301
302 case Instruction::VAArg:
303 // "va-arg" from a pointer is safe.
304 break;
305 case Instruction::Store:
306 if (V == I->getOperand(0)) {
307 // Stored the pointer - conservatively assume it may be unsafe.
308 LLVM_DEBUG(dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] Unsafe alloca: "
<< *AllocaPtr << "\n store of address: "
<< *I << "\n"; } } while (false)
309 << "[SafeStack] Unsafe alloca: " << *AllocaPtrdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] Unsafe alloca: "
<< *AllocaPtr << "\n store of address: "
<< *I << "\n"; } } while (false)
310 << "\n store of address: " << *I << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] Unsafe alloca: "
<< *AllocaPtr << "\n store of address: "
<< *I << "\n"; } } while (false)
;
311 return false;
312 }
313
314 if (!IsAccessSafe(UI, DL.getTypeStoreSize(I->getOperand(0)->getType()),
315 AllocaPtr, AllocaSize))
316 return false;
317 break;
318
319 case Instruction::Ret:
320 // Information leak.
321 return false;
322
323 case Instruction::Call:
324 case Instruction::Invoke: {
325 ImmutableCallSite CS(I);
326
327 if (I->isLifetimeStartOrEnd())
328 continue;
329
330 if (const MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
331 if (!IsMemIntrinsicSafe(MI, UI, AllocaPtr, AllocaSize)) {
332 LLVM_DEBUG(dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] Unsafe alloca: "
<< *AllocaPtr << "\n unsafe memintrinsic: "
<< *I << "\n"; } } while (false)
333 << "[SafeStack] Unsafe alloca: " << *AllocaPtrdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] Unsafe alloca: "
<< *AllocaPtr << "\n unsafe memintrinsic: "
<< *I << "\n"; } } while (false)
334 << "\n unsafe memintrinsic: " << *I << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] Unsafe alloca: "
<< *AllocaPtr << "\n unsafe memintrinsic: "
<< *I << "\n"; } } while (false)
;
335 return false;
336 }
337 continue;
338 }
339
340 // LLVM 'nocapture' attribute is only set for arguments whose address
341 // is not stored, passed around, or used in any other non-trivial way.
342 // We assume that passing a pointer to an object as a 'nocapture
343 // readnone' argument is safe.
344 // FIXME: a more precise solution would require an interprocedural
345 // analysis here, which would look at all uses of an argument inside
346 // the function being called.
347 ImmutableCallSite::arg_iterator B = CS.arg_begin(), E = CS.arg_end();
348 for (ImmutableCallSite::arg_iterator A = B; A != E; ++A)
349 if (A->get() == V)
350 if (!(CS.doesNotCapture(A - B) && (CS.doesNotAccessMemory(A - B) ||
351 CS.doesNotAccessMemory()))) {
352 LLVM_DEBUG(dbgs() << "[SafeStack] Unsafe alloca: " << *AllocaPtrdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] Unsafe alloca: "
<< *AllocaPtr << "\n unsafe call: " <<
*I << "\n"; } } while (false)
353 << "\n unsafe call: " << *I << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] Unsafe alloca: "
<< *AllocaPtr << "\n unsafe call: " <<
*I << "\n"; } } while (false)
;
354 return false;
355 }
356 continue;
357 }
358
359 default:
360 if (Visited.insert(I).second)
361 WorkList.push_back(cast<const Instruction>(I));
362 }
363 }
364 }
365
366 // All uses of the alloca are safe, we can place it on the safe stack.
367 return true;
368}
369
370Value *SafeStack::getStackGuard(IRBuilder<> &IRB, Function &F) {
371 Value *StackGuardVar = TL.getIRStackGuard(IRB);
372 if (!StackGuardVar)
373 StackGuardVar =
374 F.getParent()->getOrInsertGlobal("__stack_chk_guard", StackPtrTy);
375 return IRB.CreateLoad(StackGuardVar, "StackGuard");
376}
377
378void SafeStack::findInsts(Function &F,
379 SmallVectorImpl<AllocaInst *> &StaticAllocas,
380 SmallVectorImpl<AllocaInst *> &DynamicAllocas,
381 SmallVectorImpl<Argument *> &ByValArguments,
382 SmallVectorImpl<ReturnInst *> &Returns,
383 SmallVectorImpl<Instruction *> &StackRestorePoints) {
384 for (Instruction &I : instructions(&F)) {
385 if (auto AI = dyn_cast<AllocaInst>(&I)) {
386 ++NumAllocas;
387
388 uint64_t Size = getStaticAllocaAllocationSize(AI);
389 if (IsSafeStackAlloca(AI, Size))
390 continue;
391
392 if (AI->isStaticAlloca()) {
393 ++NumUnsafeStaticAllocas;
394 StaticAllocas.push_back(AI);
395 } else {
396 ++NumUnsafeDynamicAllocas;
397 DynamicAllocas.push_back(AI);
398 }
399 } else if (auto RI = dyn_cast<ReturnInst>(&I)) {
400 Returns.push_back(RI);
401 } else if (auto CI = dyn_cast<CallInst>(&I)) {
402 // setjmps require stack restore.
403 if (CI->getCalledFunction() && CI->canReturnTwice())
404 StackRestorePoints.push_back(CI);
405 } else if (auto LP = dyn_cast<LandingPadInst>(&I)) {
406 // Exception landing pads require stack restore.
407 StackRestorePoints.push_back(LP);
408 } else if (auto II = dyn_cast<IntrinsicInst>(&I)) {
409 if (II->getIntrinsicID() == Intrinsic::gcroot)
410 report_fatal_error(
411 "gcroot intrinsic not compatible with safestack attribute");
412 }
413 }
414 for (Argument &Arg : F.args()) {
415 if (!Arg.hasByValAttr())
416 continue;
417 uint64_t Size =
418 DL.getTypeStoreSize(Arg.getType()->getPointerElementType());
419 if (IsSafeStackAlloca(&Arg, Size))
420 continue;
421
422 ++NumUnsafeByValArguments;
423 ByValArguments.push_back(&Arg);
424 }
425}
426
427AllocaInst *
428SafeStack::createStackRestorePoints(IRBuilder<> &IRB, Function &F,
429 ArrayRef<Instruction *> StackRestorePoints,
430 Value *StaticTop, bool NeedDynamicTop) {
431 assert(StaticTop && "The stack top isn't set.")((StaticTop && "The stack top isn't set.") ? static_cast
<void> (0) : __assert_fail ("StaticTop && \"The stack top isn't set.\""
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/CodeGen/SafeStack.cpp"
, 431, __PRETTY_FUNCTION__))
;
432
433 if (StackRestorePoints.empty())
434 return nullptr;
435
436 // We need the current value of the shadow stack pointer to restore
437 // after longjmp or exception catching.
438
439 // FIXME: On some platforms this could be handled by the longjmp/exception
440 // runtime itself.
441
442 AllocaInst *DynamicTop = nullptr;
443 if (NeedDynamicTop) {
444 // If we also have dynamic alloca's, the stack pointer value changes
445 // throughout the function. For now we store it in an alloca.
446 DynamicTop = IRB.CreateAlloca(StackPtrTy, /*ArraySize=*/nullptr,
447 "unsafe_stack_dynamic_ptr");
448 IRB.CreateStore(StaticTop, DynamicTop);
449 }
450
451 // Restore current stack pointer after longjmp/exception catch.
452 for (Instruction *I : StackRestorePoints) {
453 ++NumUnsafeStackRestorePoints;
454
455 IRB.SetInsertPoint(I->getNextNode());
456 Value *CurrentTop = DynamicTop ? IRB.CreateLoad(DynamicTop) : StaticTop;
457 IRB.CreateStore(CurrentTop, UnsafeStackPtr);
458 }
459
460 return DynamicTop;
461}
462
463void SafeStack::checkStackGuard(IRBuilder<> &IRB, Function &F, ReturnInst &RI,
464 AllocaInst *StackGuardSlot, Value *StackGuard) {
465 Value *V = IRB.CreateLoad(StackGuardSlot);
466 Value *Cmp = IRB.CreateICmpNE(StackGuard, V);
467
468 auto SuccessProb = BranchProbabilityInfo::getBranchProbStackProtector(true);
469 auto FailureProb = BranchProbabilityInfo::getBranchProbStackProtector(false);
470 MDNode *Weights = MDBuilder(F.getContext())
471 .createBranchWeights(SuccessProb.getNumerator(),
472 FailureProb.getNumerator());
473 Instruction *CheckTerm =
474 SplitBlockAndInsertIfThen(Cmp, &RI,
475 /* Unreachable */ true, Weights);
476 IRBuilder<> IRBFail(CheckTerm);
477 // FIXME: respect -fsanitize-trap / -ftrap-function here?
478 Constant *StackChkFail = F.getParent()->getOrInsertFunction(
479 "__stack_chk_fail", IRB.getVoidTy());
480 IRBFail.CreateCall(StackChkFail, {});
481}
482
483/// We explicitly compute and set the unsafe stack layout for all unsafe
484/// static alloca instructions. We save the unsafe "base pointer" in the
485/// prologue into a local variable and restore it in the epilogue.
486Value *SafeStack::moveStaticAllocasToUnsafeStack(
487 IRBuilder<> &IRB, Function &F, ArrayRef<AllocaInst *> StaticAllocas,
488 ArrayRef<Argument *> ByValArguments, ArrayRef<ReturnInst *> Returns,
489 Instruction *BasePointer, AllocaInst *StackGuardSlot) {
490 if (StaticAllocas.empty() && ByValArguments.empty())
491 return BasePointer;
492
493 DIBuilder DIB(*F.getParent());
494
495 StackColoring SSC(F, StaticAllocas);
496 SSC.run();
497 SSC.removeAllMarkers();
498
499 // Unsafe stack always grows down.
500 StackLayout SSL(StackAlignment);
501 if (StackGuardSlot) {
502 Type *Ty = StackGuardSlot->getAllocatedType();
503 unsigned Align =
504 std::max(DL.getPrefTypeAlignment(Ty), StackGuardSlot->getAlignment());
505 SSL.addObject(StackGuardSlot, getStaticAllocaAllocationSize(StackGuardSlot),
506 Align, SSC.getFullLiveRange());
507 }
508
509 for (Argument *Arg : ByValArguments) {
510 Type *Ty = Arg->getType()->getPointerElementType();
511 uint64_t Size = DL.getTypeStoreSize(Ty);
512 if (Size == 0)
513 Size = 1; // Don't create zero-sized stack objects.
514
515 // Ensure the object is properly aligned.
516 unsigned Align = std::max((unsigned)DL.getPrefTypeAlignment(Ty),
517 Arg->getParamAlignment());
518 SSL.addObject(Arg, Size, Align, SSC.getFullLiveRange());
519 }
520
521 for (AllocaInst *AI : StaticAllocas) {
522 Type *Ty = AI->getAllocatedType();
523 uint64_t Size = getStaticAllocaAllocationSize(AI);
524 if (Size == 0)
525 Size = 1; // Don't create zero-sized stack objects.
526
527 // Ensure the object is properly aligned.
528 unsigned Align =
529 std::max((unsigned)DL.getPrefTypeAlignment(Ty), AI->getAlignment());
530
531 SSL.addObject(AI, Size, Align, SSC.getLiveRange(AI));
532 }
533
534 SSL.computeLayout();
535 unsigned FrameAlignment = SSL.getFrameAlignment();
536
537 // FIXME: tell SSL that we start at a less-then-MaxAlignment aligned location
538 // (AlignmentSkew).
539 if (FrameAlignment > StackAlignment) {
540 // Re-align the base pointer according to the max requested alignment.
541 assert(isPowerOf2_32(FrameAlignment))((isPowerOf2_32(FrameAlignment)) ? static_cast<void> (0
) : __assert_fail ("isPowerOf2_32(FrameAlignment)", "/build/llvm-toolchain-snapshot-8~svn350071/lib/CodeGen/SafeStack.cpp"
, 541, __PRETTY_FUNCTION__))
;
542 IRB.SetInsertPoint(BasePointer->getNextNode());
543 BasePointer = cast<Instruction>(IRB.CreateIntToPtr(
544 IRB.CreateAnd(IRB.CreatePtrToInt(BasePointer, IntPtrTy),
545 ConstantInt::get(IntPtrTy, ~uint64_t(FrameAlignment - 1))),
546 StackPtrTy));
547 }
548
549 IRB.SetInsertPoint(BasePointer->getNextNode());
550
551 if (StackGuardSlot) {
552 unsigned Offset = SSL.getObjectOffset(StackGuardSlot);
553 Value *Off = IRB.CreateGEP(BasePointer, // BasePointer is i8*
554 ConstantInt::get(Int32Ty, -Offset));
555 Value *NewAI =
556 IRB.CreateBitCast(Off, StackGuardSlot->getType(), "StackGuardSlot");
557
558 // Replace alloc with the new location.
559 StackGuardSlot->replaceAllUsesWith(NewAI);
560 StackGuardSlot->eraseFromParent();
561 }
562
563 for (Argument *Arg : ByValArguments) {
564 unsigned Offset = SSL.getObjectOffset(Arg);
565 unsigned Align = SSL.getObjectAlignment(Arg);
566 Type *Ty = Arg->getType()->getPointerElementType();
567
568 uint64_t Size = DL.getTypeStoreSize(Ty);
569 if (Size == 0)
570 Size = 1; // Don't create zero-sized stack objects.
571
572 Value *Off = IRB.CreateGEP(BasePointer, // BasePointer is i8*
573 ConstantInt::get(Int32Ty, -Offset));
574 Value *NewArg = IRB.CreateBitCast(Off, Arg->getType(),
575 Arg->getName() + ".unsafe-byval");
576
577 // Replace alloc with the new location.
578 replaceDbgDeclare(Arg, BasePointer, BasePointer->getNextNode(), DIB,
579 DIExpression::NoDeref, -Offset, DIExpression::NoDeref);
580 Arg->replaceAllUsesWith(NewArg);
581 IRB.SetInsertPoint(cast<Instruction>(NewArg)->getNextNode());
582 IRB.CreateMemCpy(Off, Align, Arg, Arg->getParamAlignment(), Size);
583 }
584
585 // Allocate space for every unsafe static AllocaInst on the unsafe stack.
586 for (AllocaInst *AI : StaticAllocas) {
587 IRB.SetInsertPoint(AI);
588 unsigned Offset = SSL.getObjectOffset(AI);
589
590 uint64_t Size = getStaticAllocaAllocationSize(AI);
591 if (Size == 0)
592 Size = 1; // Don't create zero-sized stack objects.
Value stored to 'Size' is never read
593
594 replaceDbgDeclareForAlloca(AI, BasePointer, DIB, DIExpression::NoDeref,
595 -Offset, DIExpression::NoDeref);
596 replaceDbgValueForAlloca(AI, BasePointer, DIB, -Offset);
597
598 // Replace uses of the alloca with the new location.
599 // Insert address calculation close to each use to work around PR27844.
600 std::string Name = std::string(AI->getName()) + ".unsafe";
601 while (!AI->use_empty()) {
602 Use &U = *AI->use_begin();
603 Instruction *User = cast<Instruction>(U.getUser());
604
605 Instruction *InsertBefore;
606 if (auto *PHI = dyn_cast<PHINode>(User))
607 InsertBefore = PHI->getIncomingBlock(U)->getTerminator();
608 else
609 InsertBefore = User;
610
611 IRBuilder<> IRBUser(InsertBefore);
612 Value *Off = IRBUser.CreateGEP(BasePointer, // BasePointer is i8*
613 ConstantInt::get(Int32Ty, -Offset));
614 Value *Replacement = IRBUser.CreateBitCast(Off, AI->getType(), Name);
615
616 if (auto *PHI = dyn_cast<PHINode>(User)) {
617 // PHI nodes may have multiple incoming edges from the same BB (why??),
618 // all must be updated at once with the same incoming value.
619 auto *BB = PHI->getIncomingBlock(U);
620 for (unsigned I = 0; I < PHI->getNumIncomingValues(); ++I)
621 if (PHI->getIncomingBlock(I) == BB)
622 PHI->setIncomingValue(I, Replacement);
623 } else {
624 U.set(Replacement);
625 }
626 }
627
628 AI->eraseFromParent();
629 }
630
631 // Re-align BasePointer so that our callees would see it aligned as
632 // expected.
633 // FIXME: no need to update BasePointer in leaf functions.
634 unsigned FrameSize = alignTo(SSL.getFrameSize(), StackAlignment);
635
636 // Update shadow stack pointer in the function epilogue.
637 IRB.SetInsertPoint(BasePointer->getNextNode());
638
639 Value *StaticTop =
640 IRB.CreateGEP(BasePointer, ConstantInt::get(Int32Ty, -FrameSize),
641 "unsafe_stack_static_top");
642 IRB.CreateStore(StaticTop, UnsafeStackPtr);
643 return StaticTop;
644}
645
646void SafeStack::moveDynamicAllocasToUnsafeStack(
647 Function &F, Value *UnsafeStackPtr, AllocaInst *DynamicTop,
648 ArrayRef<AllocaInst *> DynamicAllocas) {
649 DIBuilder DIB(*F.getParent());
650
651 for (AllocaInst *AI : DynamicAllocas) {
652 IRBuilder<> IRB(AI);
653
654 // Compute the new SP value (after AI).
655 Value *ArraySize = AI->getArraySize();
656 if (ArraySize->getType() != IntPtrTy)
657 ArraySize = IRB.CreateIntCast(ArraySize, IntPtrTy, false);
658
659 Type *Ty = AI->getAllocatedType();
660 uint64_t TySize = DL.getTypeAllocSize(Ty);
661 Value *Size = IRB.CreateMul(ArraySize, ConstantInt::get(IntPtrTy, TySize));
662
663 Value *SP = IRB.CreatePtrToInt(IRB.CreateLoad(UnsafeStackPtr), IntPtrTy);
664 SP = IRB.CreateSub(SP, Size);
665
666 // Align the SP value to satisfy the AllocaInst, type and stack alignments.
667 unsigned Align = std::max(
668 std::max((unsigned)DL.getPrefTypeAlignment(Ty), AI->getAlignment()),
669 (unsigned)StackAlignment);
670
671 assert(isPowerOf2_32(Align))((isPowerOf2_32(Align)) ? static_cast<void> (0) : __assert_fail
("isPowerOf2_32(Align)", "/build/llvm-toolchain-snapshot-8~svn350071/lib/CodeGen/SafeStack.cpp"
, 671, __PRETTY_FUNCTION__))
;
672 Value *NewTop = IRB.CreateIntToPtr(
673 IRB.CreateAnd(SP, ConstantInt::get(IntPtrTy, ~uint64_t(Align - 1))),
674 StackPtrTy);
675
676 // Save the stack pointer.
677 IRB.CreateStore(NewTop, UnsafeStackPtr);
678 if (DynamicTop)
679 IRB.CreateStore(NewTop, DynamicTop);
680
681 Value *NewAI = IRB.CreatePointerCast(NewTop, AI->getType());
682 if (AI->hasName() && isa<Instruction>(NewAI))
683 NewAI->takeName(AI);
684
685 replaceDbgDeclareForAlloca(AI, NewAI, DIB, DIExpression::NoDeref, 0,
686 DIExpression::NoDeref);
687 AI->replaceAllUsesWith(NewAI);
688 AI->eraseFromParent();
689 }
690
691 if (!DynamicAllocas.empty()) {
692 // Now go through the instructions again, replacing stacksave/stackrestore.
693 for (inst_iterator It = inst_begin(&F), Ie = inst_end(&F); It != Ie;) {
694 Instruction *I = &*(It++);
695 auto II = dyn_cast<IntrinsicInst>(I);
696 if (!II)
697 continue;
698
699 if (II->getIntrinsicID() == Intrinsic::stacksave) {
700 IRBuilder<> IRB(II);
701 Instruction *LI = IRB.CreateLoad(UnsafeStackPtr);
702 LI->takeName(II);
703 II->replaceAllUsesWith(LI);
704 II->eraseFromParent();
705 } else if (II->getIntrinsicID() == Intrinsic::stackrestore) {
706 IRBuilder<> IRB(II);
707 Instruction *SI = IRB.CreateStore(II->getArgOperand(0), UnsafeStackPtr);
708 SI->takeName(II);
709 assert(II->use_empty())((II->use_empty()) ? static_cast<void> (0) : __assert_fail
("II->use_empty()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/CodeGen/SafeStack.cpp"
, 709, __PRETTY_FUNCTION__))
;
710 II->eraseFromParent();
711 }
712 }
713 }
714}
715
716bool SafeStack::ShouldInlinePointerAddress(CallSite &CS) {
717 Function *Callee = CS.getCalledFunction();
718 if (CS.hasFnAttr(Attribute::AlwaysInline) && isInlineViable(*Callee))
719 return true;
720 if (Callee->isInterposable() || Callee->hasFnAttribute(Attribute::NoInline) ||
721 CS.isNoInline())
722 return false;
723 return true;
724}
725
726void SafeStack::TryInlinePointerAddress() {
727 if (!isa<CallInst>(UnsafeStackPtr))
728 return;
729
730 if(F.hasFnAttribute(Attribute::OptimizeNone))
731 return;
732
733 CallSite CS(UnsafeStackPtr);
734 Function *Callee = CS.getCalledFunction();
735 if (!Callee || Callee->isDeclaration())
736 return;
737
738 if (!ShouldInlinePointerAddress(CS))
739 return;
740
741 InlineFunctionInfo IFI;
742 InlineFunction(CS, IFI);
743}
744
745bool SafeStack::run() {
746 assert(F.hasFnAttribute(Attribute::SafeStack) &&((F.hasFnAttribute(Attribute::SafeStack) && "Can't run SafeStack on a function without the attribute"
) ? static_cast<void> (0) : __assert_fail ("F.hasFnAttribute(Attribute::SafeStack) && \"Can't run SafeStack on a function without the attribute\""
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/CodeGen/SafeStack.cpp"
, 747, __PRETTY_FUNCTION__))
747 "Can't run SafeStack on a function without the attribute")((F.hasFnAttribute(Attribute::SafeStack) && "Can't run SafeStack on a function without the attribute"
) ? static_cast<void> (0) : __assert_fail ("F.hasFnAttribute(Attribute::SafeStack) && \"Can't run SafeStack on a function without the attribute\""
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/CodeGen/SafeStack.cpp"
, 747, __PRETTY_FUNCTION__))
;
748 assert(!F.isDeclaration() && "Can't run SafeStack on a function declaration")((!F.isDeclaration() && "Can't run SafeStack on a function declaration"
) ? static_cast<void> (0) : __assert_fail ("!F.isDeclaration() && \"Can't run SafeStack on a function declaration\""
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/CodeGen/SafeStack.cpp"
, 748, __PRETTY_FUNCTION__))
;
749
750 ++NumFunctions;
751
752 SmallVector<AllocaInst *, 16> StaticAllocas;
753 SmallVector<AllocaInst *, 4> DynamicAllocas;
754 SmallVector<Argument *, 4> ByValArguments;
755 SmallVector<ReturnInst *, 4> Returns;
756
757 // Collect all points where stack gets unwound and needs to be restored
758 // This is only necessary because the runtime (setjmp and unwind code) is
759 // not aware of the unsafe stack and won't unwind/restore it properly.
760 // To work around this problem without changing the runtime, we insert
761 // instrumentation to restore the unsafe stack pointer when necessary.
762 SmallVector<Instruction *, 4> StackRestorePoints;
763
764 // Find all static and dynamic alloca instructions that must be moved to the
765 // unsafe stack, all return instructions and stack restore points.
766 findInsts(F, StaticAllocas, DynamicAllocas, ByValArguments, Returns,
767 StackRestorePoints);
768
769 if (StaticAllocas.empty() && DynamicAllocas.empty() &&
770 ByValArguments.empty() && StackRestorePoints.empty())
771 return false; // Nothing to do in this function.
772
773 if (!StaticAllocas.empty() || !DynamicAllocas.empty() ||
774 !ByValArguments.empty())
775 ++NumUnsafeStackFunctions; // This function has the unsafe stack.
776
777 if (!StackRestorePoints.empty())
778 ++NumUnsafeStackRestorePointsFunctions;
779
780 IRBuilder<> IRB(&F.front(), F.begin()->getFirstInsertionPt());
781 // Calls must always have a debug location, or else inlining breaks. So
782 // we explicitly set a artificial debug location here.
783 if (DISubprogram *SP = F.getSubprogram())
784 IRB.SetCurrentDebugLocation(DebugLoc::get(SP->getScopeLine(), 0, SP));
785 if (SafeStackUsePointerAddress) {
786 Value *Fn = F.getParent()->getOrInsertFunction(
787 "__safestack_pointer_address", StackPtrTy->getPointerTo(0));
788 UnsafeStackPtr = IRB.CreateCall(Fn);
789 } else {
790 UnsafeStackPtr = TL.getSafeStackPointerLocation(IRB);
791 }
792
793 // Load the current stack pointer (we'll also use it as a base pointer).
794 // FIXME: use a dedicated register for it ?
795 Instruction *BasePointer =
796 IRB.CreateLoad(UnsafeStackPtr, false, "unsafe_stack_ptr");
797 assert(BasePointer->getType() == StackPtrTy)((BasePointer->getType() == StackPtrTy) ? static_cast<void
> (0) : __assert_fail ("BasePointer->getType() == StackPtrTy"
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/CodeGen/SafeStack.cpp"
, 797, __PRETTY_FUNCTION__))
;
798
799 AllocaInst *StackGuardSlot = nullptr;
800 // FIXME: implement weaker forms of stack protector.
801 if (F.hasFnAttribute(Attribute::StackProtect) ||
802 F.hasFnAttribute(Attribute::StackProtectStrong) ||
803 F.hasFnAttribute(Attribute::StackProtectReq)) {
804 Value *StackGuard = getStackGuard(IRB, F);
805 StackGuardSlot = IRB.CreateAlloca(StackPtrTy, nullptr);
806 IRB.CreateStore(StackGuard, StackGuardSlot);
807
808 for (ReturnInst *RI : Returns) {
809 IRBuilder<> IRBRet(RI);
810 checkStackGuard(IRBRet, F, *RI, StackGuardSlot, StackGuard);
811 }
812 }
813
814 // The top of the unsafe stack after all unsafe static allocas are
815 // allocated.
816 Value *StaticTop =
817 moveStaticAllocasToUnsafeStack(IRB, F, StaticAllocas, ByValArguments,
818 Returns, BasePointer, StackGuardSlot);
819
820 // Safe stack object that stores the current unsafe stack top. It is updated
821 // as unsafe dynamic (non-constant-sized) allocas are allocated and freed.
822 // This is only needed if we need to restore stack pointer after longjmp
823 // or exceptions, and we have dynamic allocations.
824 // FIXME: a better alternative might be to store the unsafe stack pointer
825 // before setjmp / invoke instructions.
826 AllocaInst *DynamicTop = createStackRestorePoints(
827 IRB, F, StackRestorePoints, StaticTop, !DynamicAllocas.empty());
828
829 // Handle dynamic allocas.
830 moveDynamicAllocasToUnsafeStack(F, UnsafeStackPtr, DynamicTop,
831 DynamicAllocas);
832
833 // Restore the unsafe stack pointer before each return.
834 for (ReturnInst *RI : Returns) {
835 IRB.SetInsertPoint(RI);
836 IRB.CreateStore(BasePointer, UnsafeStackPtr);
837 }
838
839 TryInlinePointerAddress();
840
841 LLVM_DEBUG(dbgs() << "[SafeStack] safestack applied\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] safestack applied\n"
; } } while (false)
;
842 return true;
843}
844
845class SafeStackLegacyPass : public FunctionPass {
846 const TargetMachine *TM = nullptr;
847
848public:
849 static char ID; // Pass identification, replacement for typeid..
850
851 SafeStackLegacyPass() : FunctionPass(ID) {
852 initializeSafeStackLegacyPassPass(*PassRegistry::getPassRegistry());
853 }
854
855 void getAnalysisUsage(AnalysisUsage &AU) const override {
856 AU.addRequired<TargetPassConfig>();
857 AU.addRequired<TargetLibraryInfoWrapperPass>();
858 AU.addRequired<AssumptionCacheTracker>();
859 }
860
861 bool runOnFunction(Function &F) override {
862 LLVM_DEBUG(dbgs() << "[SafeStack] Function: " << F.getName() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] Function: " <<
F.getName() << "\n"; } } while (false)
;
863
864 if (!F.hasFnAttribute(Attribute::SafeStack)) {
865 LLVM_DEBUG(dbgs() << "[SafeStack] safestack is not requested"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] safestack is not requested"
" for this function\n"; } } while (false)
866 " for this function\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] safestack is not requested"
" for this function\n"; } } while (false)
;
867 return false;
868 }
869
870 if (F.isDeclaration()) {
871 LLVM_DEBUG(dbgs() << "[SafeStack] function definition"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] function definition"
" is not available\n"; } } while (false)
872 " is not available\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("safe-stack")) { dbgs() << "[SafeStack] function definition"
" is not available\n"; } } while (false)
;
873 return false;
874 }
875
876 TM = &getAnalysis<TargetPassConfig>().getTM<TargetMachine>();
877 auto *TL = TM->getSubtargetImpl(F)->getTargetLowering();
878 if (!TL)
879 report_fatal_error("TargetLowering instance is required");
880
881 auto *DL = &F.getParent()->getDataLayout();
882 auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
883 auto &ACT = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
884
885 // Compute DT and LI only for functions that have the attribute.
886 // This is only useful because the legacy pass manager doesn't let us
887 // compute analyzes lazily.
888 // In the backend pipeline, nothing preserves DT before SafeStack, so we
889 // would otherwise always compute it wastefully, even if there is no
890 // function with the safestack attribute.
891 DominatorTree DT(F);
892 LoopInfo LI(DT);
893
894 ScalarEvolution SE(F, TLI, ACT, DT, LI);
895
896 return SafeStack(F, *TL, *DL, SE).run();
897 }
898};
899
900} // end anonymous namespace
901
902char SafeStackLegacyPass::ID = 0;
903
904INITIALIZE_PASS_BEGIN(SafeStackLegacyPass, DEBUG_TYPE,static void *initializeSafeStackLegacyPassPassOnce(PassRegistry
&Registry) {
905 "Safe Stack instrumentation pass", false, false)static void *initializeSafeStackLegacyPassPassOnce(PassRegistry
&Registry) {
906INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)initializeTargetPassConfigPass(Registry);
907INITIALIZE_PASS_END(SafeStackLegacyPass, DEBUG_TYPE,PassInfo *PI = new PassInfo( "Safe Stack instrumentation pass"
, "safe-stack", &SafeStackLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<SafeStackLegacyPass>), false, false); Registry
.registerPass(*PI, true); return PI; } static llvm::once_flag
InitializeSafeStackLegacyPassPassFlag; void llvm::initializeSafeStackLegacyPassPass
(PassRegistry &Registry) { llvm::call_once(InitializeSafeStackLegacyPassPassFlag
, initializeSafeStackLegacyPassPassOnce, std::ref(Registry));
}
908 "Safe Stack instrumentation pass", false, false)PassInfo *PI = new PassInfo( "Safe Stack instrumentation pass"
, "safe-stack", &SafeStackLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<SafeStackLegacyPass>), false, false); Registry
.registerPass(*PI, true); return PI; } static llvm::once_flag
InitializeSafeStackLegacyPassPassFlag; void llvm::initializeSafeStackLegacyPassPass
(PassRegistry &Registry) { llvm::call_once(InitializeSafeStackLegacyPassPassFlag
, initializeSafeStackLegacyPassPassOnce, std::ref(Registry));
}
909
910FunctionPass *llvm::createSafeStackPass() { return new SafeStackLegacyPass(); }