1 //===- EntryExitInstrumenter.cpp - Function Entry/Exit Instrumentation ----===//
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 #include "llvm/Transforms/Utils/EntryExitInstrumenter.h"
10 #include "llvm/Analysis/GlobalsModRef.h"
11 #include "llvm/IR/DebugInfoMetadata.h"
12 #include "llvm/IR/Dominators.h"
13 #include "llvm/IR/Function.h"
14 #include "llvm/IR/Instructions.h"
15 #include "llvm/IR/Intrinsics.h"
16 #include "llvm/IR/Module.h"
17 #include "llvm/IR/Type.h"
18 #include "llvm/TargetParser/Triple.h"
19
20 using namespace llvm;
21
insertCall(Function & CurFn,StringRef Func,Instruction * InsertionPt,DebugLoc DL)22 static void insertCall(Function &CurFn, StringRef Func,
23 Instruction *InsertionPt, DebugLoc DL) {
24 Module &M = *InsertionPt->getParent()->getParent()->getParent();
25 LLVMContext &C = InsertionPt->getParent()->getContext();
26
27 if (Func == "mcount" ||
28 Func == ".mcount" ||
29 Func == "llvm.arm.gnu.eabi.mcount" ||
30 Func == "\01_mcount" ||
31 Func == "\01mcount" ||
32 Func == "__mcount" ||
33 Func == "_mcount" ||
34 Func == "__cyg_profile_func_enter_bare") {
35 Triple TargetTriple(M.getTargetTriple());
36 if (TargetTriple.isOSAIX() && Func == "__mcount") {
37 Type *SizeTy = M.getDataLayout().getIntPtrType(C);
38 Type *SizePtrTy = PointerType::getUnqual(C);
39 GlobalVariable *GV = new GlobalVariable(M, SizeTy, /*isConstant=*/false,
40 GlobalValue::InternalLinkage,
41 ConstantInt::get(SizeTy, 0));
42 CallInst *Call = CallInst::Create(
43 M.getOrInsertFunction(Func,
44 FunctionType::get(Type::getVoidTy(C), {SizePtrTy},
45 /*isVarArg=*/false)),
46 {GV}, "", InsertionPt);
47 Call->setDebugLoc(DL);
48 } else {
49 FunctionCallee Fn = M.getOrInsertFunction(Func, Type::getVoidTy(C));
50 CallInst *Call = CallInst::Create(Fn, "", InsertionPt);
51 Call->setDebugLoc(DL);
52 }
53 return;
54 }
55
56 if (Func == "__cyg_profile_func_enter" || Func == "__cyg_profile_func_exit") {
57 Type *ArgTypes[] = {PointerType::getUnqual(C), PointerType::getUnqual(C)};
58
59 FunctionCallee Fn = M.getOrInsertFunction(
60 Func, FunctionType::get(Type::getVoidTy(C), ArgTypes, false));
61
62 Instruction *RetAddr = CallInst::Create(
63 Intrinsic::getDeclaration(&M, Intrinsic::returnaddress),
64 ArrayRef<Value *>(ConstantInt::get(Type::getInt32Ty(C), 0)), "",
65 InsertionPt);
66 RetAddr->setDebugLoc(DL);
67
68 Value *Args[] = {&CurFn, RetAddr};
69 CallInst *Call =
70 CallInst::Create(Fn, ArrayRef<Value *>(Args), "", InsertionPt);
71 Call->setDebugLoc(DL);
72 return;
73 }
74
75 // We only know how to call a fixed set of instrumentation functions, because
76 // they all expect different arguments, etc.
77 report_fatal_error(Twine("Unknown instrumentation function: '") + Func + "'");
78 }
79
runOnFunction(Function & F,bool PostInlining)80 static bool runOnFunction(Function &F, bool PostInlining) {
81 // The asm in a naked function may reasonably expect the argument registers
82 // and the return address register (if present) to be live. An inserted
83 // function call will clobber these registers. Simply skip naked functions for
84 // all targets.
85 if (F.hasFnAttribute(Attribute::Naked))
86 return false;
87
88 StringRef EntryAttr = PostInlining ? "instrument-function-entry-inlined"
89 : "instrument-function-entry";
90
91 StringRef ExitAttr = PostInlining ? "instrument-function-exit-inlined"
92 : "instrument-function-exit";
93
94 StringRef EntryFunc = F.getFnAttribute(EntryAttr).getValueAsString();
95 StringRef ExitFunc = F.getFnAttribute(ExitAttr).getValueAsString();
96
97 bool Changed = false;
98
99 // If the attribute is specified, insert instrumentation and then "consume"
100 // the attribute so that it's not inserted again if the pass should happen to
101 // run later for some reason.
102
103 if (!EntryFunc.empty()) {
104 DebugLoc DL;
105 if (auto SP = F.getSubprogram())
106 DL = DILocation::get(SP->getContext(), SP->getScopeLine(), 0, SP);
107
108 insertCall(F, EntryFunc, &*F.begin()->getFirstInsertionPt(), DL);
109 Changed = true;
110 F.removeFnAttr(EntryAttr);
111 }
112
113 if (!ExitFunc.empty()) {
114 for (BasicBlock &BB : F) {
115 Instruction *T = BB.getTerminator();
116 if (!isa<ReturnInst>(T))
117 continue;
118
119 // If T is preceded by a musttail call, that's the real terminator.
120 if (CallInst *CI = BB.getTerminatingMustTailCall())
121 T = CI;
122
123 DebugLoc DL;
124 if (DebugLoc TerminatorDL = T->getDebugLoc())
125 DL = TerminatorDL;
126 else if (auto SP = F.getSubprogram())
127 DL = DILocation::get(SP->getContext(), 0, 0, SP);
128
129 insertCall(F, ExitFunc, T, DL);
130 Changed = true;
131 }
132 F.removeFnAttr(ExitAttr);
133 }
134
135 return Changed;
136 }
137
138 PreservedAnalyses
run(Function & F,FunctionAnalysisManager & AM)139 llvm::EntryExitInstrumenterPass::run(Function &F, FunctionAnalysisManager &AM) {
140 runOnFunction(F, PostInlining);
141 PreservedAnalyses PA;
142 PA.preserveSet<CFGAnalyses>();
143 return PA;
144 }
145
printPipeline(raw_ostream & OS,function_ref<StringRef (StringRef)> MapClassName2PassName)146 void llvm::EntryExitInstrumenterPass::printPipeline(
147 raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
148 static_cast<PassInfoMixin<llvm::EntryExitInstrumenterPass> *>(this)
149 ->printPipeline(OS, MapClassName2PassName);
150 OS << '<';
151 if (PostInlining)
152 OS << "post-inline";
153 OS << '>';
154 }
155