1 //===----------- BPFPreserveDIType.cpp - Preserve DebugInfo Types ---------===//
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 // Preserve Debuginfo types encoded in __builtin_btf_type_id() metadata.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "BPF.h"
14 #include "BPFCORE.h"
15 #include "llvm/IR/DebugInfoMetadata.h"
16 #include "llvm/IR/GlobalVariable.h"
17 #include "llvm/IR/Instruction.h"
18 #include "llvm/IR/Instructions.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/IR/PassManager.h"
21 #include "llvm/IR/Type.h"
22 #include "llvm/IR/User.h"
23 #include "llvm/IR/Value.h"
24 #include "llvm/Pass.h"
25 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
26
27 #define DEBUG_TYPE "bpf-preserve-di-type"
28
29 namespace llvm {
30 constexpr StringRef BPFCoreSharedInfo::TypeIdAttr;
31 } // namespace llvm
32
33 using namespace llvm;
34
35 namespace {
36
BPFPreserveDITypeImpl(Function & F)37 static bool BPFPreserveDITypeImpl(Function &F) {
38 LLVM_DEBUG(dbgs() << "********** preserve debuginfo type **********\n");
39
40 Module *M = F.getParent();
41
42 // Bail out if no debug info.
43 if (M->debug_compile_units().empty())
44 return false;
45
46 std::vector<CallInst *> PreserveDITypeCalls;
47
48 for (auto &BB : F) {
49 for (auto &I : BB) {
50 auto *Call = dyn_cast<CallInst>(&I);
51 if (!Call)
52 continue;
53
54 const auto *GV = dyn_cast<GlobalValue>(Call->getCalledOperand());
55 if (!GV)
56 continue;
57
58 if (GV->getName().startswith("llvm.bpf.btf.type.id")) {
59 if (!Call->getMetadata(LLVMContext::MD_preserve_access_index))
60 report_fatal_error(
61 "Missing metadata for llvm.bpf.btf.type.id intrinsic");
62 PreserveDITypeCalls.push_back(Call);
63 }
64 }
65 }
66
67 if (PreserveDITypeCalls.empty())
68 return false;
69
70 std::string BaseName = "llvm.btf_type_id.";
71 static int Count = 0;
72 for (auto Call : PreserveDITypeCalls) {
73 const ConstantInt *Flag = dyn_cast<ConstantInt>(Call->getArgOperand(1));
74 assert(Flag);
75 uint64_t FlagValue = Flag->getValue().getZExtValue();
76
77 if (FlagValue >= BPFCoreSharedInfo::MAX_BTF_TYPE_ID_FLAG)
78 report_fatal_error("Incorrect flag for llvm.bpf.btf.type.id intrinsic");
79
80 MDNode *MD = Call->getMetadata(LLVMContext::MD_preserve_access_index);
81
82 uint32_t Reloc;
83 if (FlagValue == BPFCoreSharedInfo::BTF_TYPE_ID_LOCAL_RELOC) {
84 Reloc = BPFCoreSharedInfo::BTF_TYPE_ID_LOCAL;
85 } else {
86 Reloc = BPFCoreSharedInfo::BTF_TYPE_ID_REMOTE;
87 DIType *Ty = cast<DIType>(MD);
88 while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
89 unsigned Tag = DTy->getTag();
90 if (Tag != dwarf::DW_TAG_const_type &&
91 Tag != dwarf::DW_TAG_volatile_type)
92 break;
93 Ty = DTy->getBaseType();
94 }
95
96 if (Ty->getName().empty())
97 report_fatal_error("Empty type name for BTF_TYPE_ID_REMOTE reloc");
98 MD = Ty;
99 }
100
101 BasicBlock *BB = Call->getParent();
102 IntegerType *VarType = Type::getInt64Ty(BB->getContext());
103 std::string GVName = BaseName + std::to_string(Count) + "$" +
104 std::to_string(Reloc);
105 GlobalVariable *GV = new GlobalVariable(
106 *M, VarType, false, GlobalVariable::ExternalLinkage, NULL, GVName);
107 GV->addAttribute(BPFCoreSharedInfo::TypeIdAttr);
108 GV->setMetadata(LLVMContext::MD_preserve_access_index, MD);
109
110 // Load the global variable which represents the type info.
111 auto *LDInst =
112 new LoadInst(Type::getInt64Ty(BB->getContext()), GV, "", Call);
113 Instruction *PassThroughInst =
114 BPFCoreSharedInfo::insertPassThrough(M, BB, LDInst, Call);
115 Call->replaceAllUsesWith(PassThroughInst);
116 Call->eraseFromParent();
117 Count++;
118 }
119
120 return true;
121 }
122
123 class BPFPreserveDIType final : public FunctionPass {
124 bool runOnFunction(Function &F) override;
125
126 public:
127 static char ID;
BPFPreserveDIType()128 BPFPreserveDIType() : FunctionPass(ID) {}
129 };
130 } // End anonymous namespace
131
132 char BPFPreserveDIType::ID = 0;
133 INITIALIZE_PASS(BPFPreserveDIType, DEBUG_TYPE, "BPF Preserve Debuginfo Type",
134 false, false)
135
createBPFPreserveDIType()136 FunctionPass *llvm::createBPFPreserveDIType() {
137 return new BPFPreserveDIType();
138 }
139
runOnFunction(Function & F)140 bool BPFPreserveDIType::runOnFunction(Function &F) {
141 return BPFPreserveDITypeImpl(F);
142 }
143
run(Function & F,FunctionAnalysisManager & AM)144 PreservedAnalyses BPFPreserveDITypePass::run(Function &F,
145 FunctionAnalysisManager &AM) {
146 return BPFPreserveDITypeImpl(F) ? PreservedAnalyses::none()
147 : PreservedAnalyses::all();
148 }
149