lld/MachO/Arch/X86_64.cpp

   1 //===- X86_64.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 "InputFiles.h"
  10 #include "Symbols.h"
  11 #include "SyntheticSections.h"
  12 #include "Target.h"
  13
  14 #include "lld/Common/ErrorHandler.h"
  15 #include "mach-o/compact_unwind_encoding.h"
  16 #include "llvm/BinaryFormat/MachO.h"
  17 #include "llvm/Support/Endian.h"
  18
  19 using namespace llvm::MachO;
  20 using namespace llvm::support::endian;
  21 using namespace lld;
  22 using namespace lld::macho;
  23
  24 namespace {
  25
  26 struct X86_64 : TargetInfo {
  27   X86_64();
  28
  29   int64_t getEmbeddedAddend(MemoryBufferRef, uint64_t offset,
  30                             const relocation_info) const override;
  31   void relocateOne(uint8_t *loc, const Reloc &, uint64_t va,
  32                    uint64_t relocVA) const override;
  33
  34   void writeStub(uint8_t *buf, const Symbol &,
  35                  uint64_t pointerVA) const override;
  36   void writeStubHelperHeader(uint8_t *buf) const override;
  37   void writeStubHelperEntry(uint8_t *buf, const Symbol &,
  38                             uint64_t entryAddr) const override;
  39
  40   void writeObjCMsgSendStub(uint8_t *buf, Symbol *sym, uint64_t stubsAddr,
  41                             uint64_t stubOffset, uint64_t selrefsVA,
  42                             uint64_t selectorIndex, uint64_t gotAddr,
  43                             uint64_t msgSendIndex) const override;
  44
  45   void relaxGotLoad(uint8_t *loc, uint8_t type) const override;
  46   uint64_t getPageSize() const override { return 4 * 1024; }
  47
  48   void handleDtraceReloc(const Symbol *sym, const Reloc &r,
  49                          uint8_t *loc) const override;
  50 };
  51 } // namespace
  52
  53 static constexpr std::array<RelocAttrs, 10> relocAttrsArray{{
  54 #define B(x) RelocAttrBits::x
  55     {"UNSIGNED",
  56      B(UNSIGNED) | B(ABSOLUTE) | B(EXTERN) | B(LOCAL) | B(BYTE4) | B(BYTE8)},
  57     {"SIGNED", B(PCREL) | B(EXTERN) | B(LOCAL) | B(BYTE4)},
  58     {"BRANCH", B(PCREL) | B(EXTERN) | B(BRANCH) | B(BYTE4)},
  59     {"GOT_LOAD", B(PCREL) | B(EXTERN) | B(GOT) | B(LOAD) | B(BYTE4)},
  60     {"GOT", B(PCREL) | B(EXTERN) | B(GOT) | B(POINTER) | B(BYTE4)},
  61     {"SUBTRACTOR", B(SUBTRAHEND) | B(EXTERN) | B(BYTE4) | B(BYTE8)},
  62     {"SIGNED_1", B(PCREL) | B(EXTERN) | B(LOCAL) | B(BYTE4)},
  63     {"SIGNED_2", B(PCREL) | B(EXTERN) | B(LOCAL) | B(BYTE4)},
  64     {"SIGNED_4", B(PCREL) | B(EXTERN) | B(LOCAL) | B(BYTE4)},
  65     {"TLV", B(PCREL) | B(EXTERN) | B(TLV) | B(LOAD) | B(BYTE4)},
  66 #undef B
  67 }};
  68
  69 static int pcrelOffset(uint8_t type) {
  70   switch (type) {
  71   case X86_64_RELOC_SIGNED_1:
  72     return 1;
  73   case X86_64_RELOC_SIGNED_2:
  74     return 2;
  75   case X86_64_RELOC_SIGNED_4:
  76     return 4;
  77   default:
  78     return 0;
  79   }
  80 }
  81
  82 int64_t X86_64::getEmbeddedAddend(MemoryBufferRef mb, uint64_t offset,
  83                                   relocation_info rel) const {
  84   auto *buf = reinterpret_cast<const uint8_t *>(mb.getBufferStart());
  85   const uint8_t *loc = buf + offset + rel.r_address;
  86
  87   switch (rel.r_length) {
  88   case 2:
  89     return static_cast<int32_t>(read32le(loc)) + pcrelOffset(rel.r_type);
  90   case 3:
  91     return read64le(loc) + pcrelOffset(rel.r_type);
  92   default:
  93     llvm_unreachable("invalid r_length");
  94   }
  95 }
  96
  97 void X86_64::relocateOne(uint8_t *loc, const Reloc &r, uint64_t value,
  98                          uint64_t relocVA) const {
  99   if (r.pcrel) {
 100     uint64_t pc = relocVA + 4 + pcrelOffset(r.type);
 101     value -= pc;
 102   }
 103
 104   switch (r.length) {
 105   case 2:
 106     if (r.type == X86_64_RELOC_UNSIGNED)
 107       checkUInt(loc, r, value, 32);
 108     else
 109       checkInt(loc, r, value, 32);
 110     write32le(loc, value);
 111     break;
 112   case 3:
 113     write64le(loc, value);
 114     break;
 115   default:
 116     llvm_unreachable("invalid r_length");
 117   }
 118 }
 119
 120 // The following methods emit a number of assembly sequences with RIP-relative
 121 // addressing. Note that RIP-relative addressing on X86-64 has the RIP pointing
 122 // to the next instruction, not the current instruction, so we always have to
 123 // account for the current instruction's size when calculating offsets.
 124 // writeRipRelative helps with that.
 125 //
 126 // bufAddr:  The virtual address corresponding to buf[0].
 127 // bufOff:   The offset within buf of the next instruction.
 128 // destAddr: The destination address that the current instruction references.
 129 static void writeRipRelative(SymbolDiagnostic d, uint8_t *buf, uint64_t bufAddr,
 130                              uint64_t bufOff, uint64_t destAddr) {
 131   uint64_t rip = bufAddr + bufOff;
 132   checkInt(buf, d, destAddr - rip, 32);
 133   // For the instructions we care about, the RIP-relative address is always
 134   // stored in the last 4 bytes of the instruction.
 135   write32le(buf + bufOff - 4, destAddr - rip);
 136 }
 137
 138 static constexpr uint8_t stub[] = {
 139     0xff, 0x25, 0, 0, 0, 0, // jmpq *__la_symbol_ptr(%rip)
 140 };
 141
 142 void X86_64::writeStub(uint8_t *buf, const Symbol &sym,
 143                        uint64_t pointerVA) const {
 144   memcpy(buf, stub, 2); // just copy the two nonzero bytes
 145   uint64_t stubAddr = in.stubs->addr + sym.stubsIndex * sizeof(stub);
 146   writeRipRelative({&sym, "stub"}, buf, stubAddr, sizeof(stub), pointerVA);
 147 }
 148
 149 static constexpr uint8_t stubHelperHeader[] = {
 150     0x4c, 0x8d, 0x1d, 0, 0, 0, 0, // 0x0: leaq ImageLoaderCache(%rip), %r11
 151     0x41, 0x53,                   // 0x7: pushq %r11
 152     0xff, 0x25, 0,    0, 0, 0,    // 0x9: jmpq *dyld_stub_binder@GOT(%rip)
 153     0x90,                         // 0xf: nop
 154 };
 155
 156 void X86_64::writeStubHelperHeader(uint8_t *buf) const {
 157   memcpy(buf, stubHelperHeader, sizeof(stubHelperHeader));
 158   SymbolDiagnostic d = {nullptr, "stub helper header"};
 159   writeRipRelative(d, buf, in.stubHelper->addr, 7,
 160                    in.imageLoaderCache->getVA());
 161   writeRipRelative(d, buf, in.stubHelper->addr, 0xf,
 162                    in.got->addr +
 163                        in.stubHelper->stubBinder->gotIndex * LP64::wordSize);
 164 }
 165
 166 static constexpr uint8_t stubHelperEntry[] = {
 167     0x68, 0, 0, 0, 0, // 0x0: pushq <bind offset>
 168     0xe9, 0, 0, 0, 0, // 0x5: jmp <__stub_helper>
 169 };
 170
 171 void X86_64::writeStubHelperEntry(uint8_t *buf, const Symbol &sym,
 172                                   uint64_t entryAddr) const {
 173   memcpy(buf, stubHelperEntry, sizeof(stubHelperEntry));
 174   write32le(buf + 1, sym.lazyBindOffset);
 175   writeRipRelative({&sym, "stub helper"}, buf, entryAddr,
 176                    sizeof(stubHelperEntry), in.stubHelper->addr);
 177 }
 178
 179 static constexpr uint8_t objcStubsFastCode[] = {
 180     0x48, 0x8b, 0x35, 0, 0, 0, 0, // 0x0: movq selrefs@selector(%rip), %rsi
 181     0xff, 0x25, 0,    0, 0, 0,    // 0x7: jmpq *_objc_msgSend@GOT(%rip)
 182 };
 183
 184 void X86_64::writeObjCMsgSendStub(uint8_t *buf, Symbol *sym, uint64_t stubsAddr,
 185                                   uint64_t stubOffset, uint64_t selrefsVA,
 186                                   uint64_t selectorIndex, uint64_t gotAddr,
 187                                   uint64_t msgSendIndex) const {
 188   memcpy(buf, objcStubsFastCode, sizeof(objcStubsFastCode));
 189   SymbolDiagnostic d = {sym, sym->getName()};
 190   uint64_t stubAddr = stubsAddr + stubOffset;
 191   writeRipRelative(d, buf, stubAddr, 7,
 192                    selrefsVA + selectorIndex * LP64::wordSize);
 193   writeRipRelative(d, buf, stubAddr, 0xd,
 194                    gotAddr + msgSendIndex * LP64::wordSize);
 195 }
 196
 197 void X86_64::relaxGotLoad(uint8_t *loc, uint8_t type) const {
 198   // Convert MOVQ to LEAQ
 199   if (loc[-2] != 0x8b)
 200     error(getRelocAttrs(type).name + " reloc requires MOVQ instruction");
 201   loc[-2] = 0x8d;
 202 }
 203
 204 X86_64::X86_64() : TargetInfo(LP64()) {
 205   cpuType = CPU_TYPE_X86_64;
 206   cpuSubtype = CPU_SUBTYPE_X86_64_ALL;
 207
 208   modeDwarfEncoding = UNWIND_X86_MODE_DWARF;
 209   subtractorRelocType = X86_64_RELOC_SUBTRACTOR;
 210   unsignedRelocType = X86_64_RELOC_UNSIGNED;
 211
 212   stubSize = sizeof(stub);
 213   stubHelperHeaderSize = sizeof(stubHelperHeader);
 214   stubHelperEntrySize = sizeof(stubHelperEntry);
 215
 216   objcStubsFastSize = sizeof(objcStubsFastCode);
 217   objcStubsAlignment = 1;
 218
 219   relocAttrs = {relocAttrsArray.data(), relocAttrsArray.size()};
 220 }
 221
 222 TargetInfo *macho::createX86_64TargetInfo() {
 223   static X86_64 t;
 224   return &t;
 225 }
 226
 227 void X86_64::handleDtraceReloc(const Symbol *sym, const Reloc &r,
 228                                uint8_t *loc) const {
 229   assert(r.type == X86_64_RELOC_BRANCH);
 230
 231   if (config->outputType == MH_OBJECT)
 232     return;
 233
 234   if (sym->getName().starts_with("___dtrace_probe")) {
 235     // change call site to a NOP
 236     loc[-1] = 0x90;
 237     write32le(loc, 0x00401F0F);
 238   } else if (sym->getName().starts_with("___dtrace_isenabled")) {
 239     // change call site to a clear eax
 240     loc[-1] = 0x33;
 241     write32le(loc, 0x909090C0);
 242   } else {
 243     error("Unrecognized dtrace symbol prefix: " + toString(*sym));
 244   }
 245 }