1 //===- bolt/Passes/ValidateMemRefs.cpp ------------------------------------===//
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 "bolt/Passes/ValidateMemRefs.h"
10 #include "bolt/Core/ParallelUtilities.h"
11
12 #define DEBUG_TYPE "bolt-memrefs"
13
14 namespace opts {
15 extern llvm::cl::opt<llvm::bolt::JumpTableSupportLevel> JumpTables;
16 }
17
18 namespace llvm::bolt {
19
20 std::atomic<std::uint64_t> ValidateMemRefs::ReplacedReferences{0};
21
checkAndFixJTReference(BinaryFunction & BF,MCInst & Inst,uint32_t OperandNum,const MCSymbol * Sym,uint64_t Offset)22 bool ValidateMemRefs::checkAndFixJTReference(BinaryFunction &BF, MCInst &Inst,
23 uint32_t OperandNum,
24 const MCSymbol *Sym,
25 uint64_t Offset) {
26 BinaryContext &BC = BF.getBinaryContext();
27 auto L = BC.scopeLock();
28 BinaryData *BD = BC.getBinaryDataByName(Sym->getName());
29 if (!BD)
30 return false;
31
32 JumpTable *JT = BC.getJumpTableContainingAddress(BD->getAddress());
33 if (!JT)
34 return false;
35
36 const bool IsLegitAccess = llvm::is_contained(JT->Parents, &BF);
37 if (IsLegitAccess)
38 return true;
39
40 // Accessing a jump table in another function. This is not a
41 // legitimate jump table access, we need to replace the reference to
42 // the jump table label with a regular rodata reference. Get a
43 // non-JT reference by fetching the symbol 1 byte before the JT
44 // label.
45 MCSymbol *NewSym = BC.getOrCreateGlobalSymbol(BD->getAddress() - 1, "DATAat");
46 BC.MIB->setOperandToSymbolRef(Inst, OperandNum, NewSym, Offset + 1, &*BC.Ctx,
47 0);
48 LLVM_DEBUG(dbgs() << "BOLT-DEBUG: replaced reference @" << BF.getPrintName()
49 << " from " << BD->getName() << " to " << NewSym->getName()
50 << " + 1\n");
51 ++ReplacedReferences;
52 return true;
53 }
54
runOnFunction(BinaryFunction & BF)55 void ValidateMemRefs::runOnFunction(BinaryFunction &BF) {
56 MCPlusBuilder *MIB = BF.getBinaryContext().MIB.get();
57
58 for (BinaryBasicBlock &BB : BF) {
59 for (MCInst &Inst : BB) {
60 for (int I = 0, E = MCPlus::getNumPrimeOperands(Inst); I != E; ++I) {
61 const MCOperand &Operand = Inst.getOperand(I);
62 if (!Operand.isExpr())
63 continue;
64
65 const auto [Sym, Offset] = MIB->getTargetSymbolInfo(Operand.getExpr());
66 if (!Sym)
67 continue;
68
69 checkAndFixJTReference(BF, Inst, I, Sym, Offset);
70 }
71 }
72 }
73 }
74
runOnFunctions(BinaryContext & BC)75 Error ValidateMemRefs::runOnFunctions(BinaryContext &BC) {
76 if (!BC.isX86())
77 return Error::success();
78
79 // Skip validation if not moving JT
80 if (opts::JumpTables == JTS_NONE || opts::JumpTables == JTS_BASIC)
81 return Error::success();
82
83 ParallelUtilities::WorkFuncWithAllocTy ProcessFunction =
84 [&](BinaryFunction &BF, MCPlusBuilder::AllocatorIdTy AllocId) {
85 runOnFunction(BF);
86 };
87 ParallelUtilities::PredicateTy SkipPredicate = [&](const BinaryFunction &BF) {
88 return !BF.hasCFG();
89 };
90 LLVM_DEBUG(dbgs() << "BOLT-DEBUG: starting memrefs validation pass\n");
91 ParallelUtilities::runOnEachFunctionWithUniqueAllocId(
92 BC, ParallelUtilities::SchedulingPolicy::SP_INST_LINEAR, ProcessFunction,
93 SkipPredicate, "validate-mem-refs", /*ForceSequential=*/true);
94 LLVM_DEBUG(dbgs() << "BOLT-DEBUG: memrefs validation is concluded\n");
95
96 if (!ReplacedReferences)
97 return Error::success();
98
99 BC.outs() << "BOLT-INFO: validate-mem-refs updated " << ReplacedReferences
100 << " object references\n";
101 return Error::success();
102 }
103
104 } // namespace llvm::bolt
105