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