ARM64Common.cpp

//===- ARM64Common.cpp ----------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "Arch/ARM64Common.h"

#include "lld/Common/ErrorHandler.h"
#include "llvm/Support/Endian.h"

using namespace llvm::MachO;
using namespace llvm::support::endian;
using namespace lld;
using namespace lld::macho;

int64_t ARM64Common::getEmbeddedAddend(MemoryBufferRef mb, uint64_t offset,
                                       const relocation_info rel) const {
  if (rel.r_type != ARM64_RELOC_UNSIGNED &&
      rel.r_type != ARM64_RELOC_SUBTRACTOR) {
    // All other reloc types should use the ADDEND relocation to store their
    // addends.
    // TODO(gkm): extract embedded addend just so we can assert that it is 0
    return 0;
  }

  const auto *buf = reinterpret_cast<const uint8_t *>(mb.getBufferStart());
  const uint8_t *loc = buf + offset + rel.r_address;
  switch (rel.r_length) {
  case 2:
    return static_cast<int32_t>(read32le(loc));
  case 3:
    return read64le(loc);
  default:
    llvm_unreachable("invalid r_length");
  }
}

static void writeValue(uint8_t *loc, const Reloc &r, uint64_t value) {
  switch (r.length) {
  case 2:
    checkInt(loc, r, value, 32);
    write32le(loc, value);
    break;
  case 3:
    write64le(loc, value);
    break;
  default:
    llvm_unreachable("invalid r_length");
  }
}

// For instruction relocations (load, store, add), the base
// instruction is pre-populated in the text section. A pre-populated
// instruction has opcode & register-operand bits set, with immediate
// operands zeroed. We read it from text, OR-in the immediate
// operands, then write-back the completed instruction.
void ARM64Common::relocateOne(uint8_t *loc, const Reloc &r, uint64_t value,
                              uint64_t pc) const {
  auto loc32 = reinterpret_cast<uint32_t *>(loc);
  uint32_t base = ((r.length == 2) ? read32le(loc) : 0);
  switch (r.type) {
  case ARM64_RELOC_BRANCH26:
    encodeBranch26(loc32, r, base, value - pc);
    break;
  case ARM64_RELOC_SUBTRACTOR:
  case ARM64_RELOC_UNSIGNED:
    writeValue(loc, r, value);
    break;
  case ARM64_RELOC_POINTER_TO_GOT:
    if (r.pcrel)
      value -= pc;
    writeValue(loc, r, value);
    break;
  case ARM64_RELOC_PAGE21:
  case ARM64_RELOC_GOT_LOAD_PAGE21:
  case ARM64_RELOC_TLVP_LOAD_PAGE21:
    assert(r.pcrel);
    encodePage21(loc32, r, base, pageBits(value) - pageBits(pc));
    break;
  case ARM64_RELOC_PAGEOFF12:
  case ARM64_RELOC_GOT_LOAD_PAGEOFF12:
  case ARM64_RELOC_TLVP_LOAD_PAGEOFF12:
    assert(!r.pcrel);
    encodePageOff12(loc32, r, base, value);
    break;
  default:
    llvm_unreachable("unexpected relocation type");
  }
}

void ARM64Common::relaxGotLoad(uint8_t *loc, uint8_t type) const {
  // The instruction format comments below are quoted from
  // Arm® Architecture Reference Manual
  // Armv8, for Armv8-A architecture profile
  // ARM DDI 0487G.a (ID011921)
  uint32_t instruction = read32le(loc);
  // C6.2.132 LDR (immediate)
  // This matches both the 64- and 32-bit variants:
  // LDR <(X|W)t>, [<Xn|SP>{, #<pimm>}]
  if ((instruction & 0xbfc00000) != 0xb9400000)
    error(getRelocAttrs(type).name + " reloc requires LDR instruction");
  assert(((instruction >> 10) & 0xfff) == 0 &&
         "non-zero embedded LDR immediate");
  // C6.2.4 ADD (immediate)
  // ADD <Xd|SP>, <Xn|SP>, #<imm>{, <shift>}
  instruction = ((instruction & 0x001fffff) | 0x91000000);
  write32le(loc, instruction);
}

void ARM64Common::handleDtraceReloc(const Symbol *sym, const Reloc &r,
                                    uint8_t *loc) const {
  assert(r.type == ARM64_RELOC_BRANCH26);

  if (config->outputType == MH_OBJECT)
    return;

  if (sym->getName().starts_with("___dtrace_probe")) {
    // change call site to a NOP
    write32le(loc, 0xD503201F);
  } else if (sym->getName().starts_with("___dtrace_isenabled")) {
    // change call site to 'MOVZ X0,0'
    write32le(loc, 0xD2800000);
  } else {
    error("Unrecognized dtrace symbol prefix: " + toString(*sym));
  }
}

static void reportUnalignedLdrStr(Twine loc, uint64_t va, int align,
                                  const Symbol *sym) {
  std::string symbolHint;
  if (sym)
    symbolHint = " (" + toString(*sym) + ")";
  error(loc + ": " + Twine(8 * align) + "-bit LDR/STR to 0x" +
        llvm::utohexstr(va) + symbolHint + " is not " + Twine(align) +
        "-byte aligned");
}

void macho::reportUnalignedLdrStr(void *loc, const lld::macho::Reloc &r,
                                  uint64_t va, int align) {
  uint64_t off = reinterpret_cast<const uint8_t *>(loc) - in.bufferStart;
  const InputSection *isec = offsetToInputSection(&off);
  std::string locStr = isec ? isec->getLocation(off) : "(invalid location)";
  ::reportUnalignedLdrStr(locStr, va, align, r.referent.dyn_cast<Symbol *>());
}

void macho::reportUnalignedLdrStr(void *loc, lld::macho::SymbolDiagnostic d,
                                  uint64_t va, int align) {
  ::reportUnalignedLdrStr(d.reason, va, align, d.symbol);
}