bolt/lib/Passes/FixRelaxationPass.cpp

   1 //===- bolt/Passes/FixRelaxationPass.cpp ------------------------*- C++ -*-===//
   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/FixRelaxationPass.h"
  10 #include "bolt/Core/ParallelUtilities.h"
  11
  12 using namespace llvm;
  13
  14 namespace llvm {
  15 namespace bolt {
  16
  17 // This function finds ADRP+ADD instruction sequences that originally before
  18 // linker relaxations were ADRP+LDR. We've modified LDR/ADD relocation properly
  19 // during relocation reading, so its targeting right symbol. As for ADRP its
  20 // target is wrong before this pass since we won't be able to recognize and
  21 // properly change R_AARCH64_ADR_GOT_PAGE relocation to
  22 // R_AARCH64_ADR_PREL_PG_HI21 during relocation reading. Now we're searching for
  23 // ADRP+ADD sequences, checking that ADRP points to the GOT-table symbol and the
  24 // target of ADD is another symbol. When found change ADRP symbol reference to
  25 // the ADDs one.
  26 void FixRelaxations::runOnFunction(BinaryFunction &BF) {
  27   BinaryContext &BC = BF.getBinaryContext();
  28   for (BinaryBasicBlock &BB : BF) {
  29     for (auto II = BB.begin(); II != BB.end(); ++II) {
  30       MCInst &Adrp = *II;
  31       if (BC.MIB->isPseudo(Adrp) || !BC.MIB->isADRP(Adrp))
  32         continue;
  33
  34       const MCSymbol *AdrpSymbol = BC.MIB->getTargetSymbol(Adrp);
  35       if (!AdrpSymbol || AdrpSymbol->getName() != "__BOLT_got_zero")
  36         continue;
  37
  38       auto NextII = std::next(II);
  39       if (NextII == BB.end())
  40         continue;
  41
  42       const MCInst &Add = *NextII;
  43       if (!BC.MIB->matchAdrpAddPair(Adrp, Add))
  44         continue;
  45
  46       const MCSymbol *Symbol = BC.MIB->getTargetSymbol(Add);
  47       if (!Symbol || AdrpSymbol == Symbol)
  48         continue;
  49
  50       auto L = BC.scopeLock();
  51       const int64_t Addend = BC.MIB->getTargetAddend(Add);
  52       BC.MIB->setOperandToSymbolRef(Adrp, /*OpNum*/ 1, Symbol, Addend,
  53                                     BC.Ctx.get(), ELF::R_AARCH64_NONE);
  54     }
  55   }
  56 }
  57
  58 Error FixRelaxations::runOnFunctions(BinaryContext &BC) {
  59   if (!BC.isAArch64() || !BC.HasRelocations)
  60     return Error::success();
  61
  62   ParallelUtilities::WorkFuncTy WorkFun = [&](BinaryFunction &BF) {
  63     runOnFunction(BF);
  64   };
  65
  66   ParallelUtilities::runOnEachFunction(
  67       BC, ParallelUtilities::SchedulingPolicy::SP_INST_LINEAR, WorkFun, nullptr,
  68       "FixRelaxations");
  69   return Error::success();
  70 }
  71
  72 } // namespace bolt
  73 } // namespace llvm