bolt/lib/Passes/ValidateMemRefs.cpp

   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
  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
  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
  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