lld/MachO/Arch/X86_64.cpp - llvm-project - Git at Google

 //===- X86_64.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 "InputFiles.h"
 #include "Symbols.h"
 #include "SyntheticSections.h"
 #include "Target.h"

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

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

 namespace {

 struct X86_64 : TargetInfo {
   X86_64();

   uint64_t getImplicitAddend(MemoryBufferRef, const section_64 &,
                              const relocation_info &) const override;
   void relocateOne(uint8_t *loc, const Reloc &, uint64_t val) const override;

   void writeStub(uint8_t *buf, const DylibSymbol &) const override;
   void writeStubHelperHeader(uint8_t *buf) const override;
   void writeStubHelperEntry(uint8_t *buf, const DylibSymbol &,
                             uint64_t entryAddr) const override;

   void prepareSymbolRelocation(lld::macho::Symbol &, const InputSection *,
                                const Reloc &) override;
   uint64_t getSymbolVA(const lld::macho::Symbol &, uint8_t type) const override;
 };

 } // namespace

 static std::string getErrorLocation(MemoryBufferRef mb, const section_64 &sec,
                                     const relocation_info &rel) {
   return ("invalid relocation at offset " + std::to_string(rel.r_address) +
           " of " + sec.segname + "," + sec.sectname + " in " +
           mb.getBufferIdentifier())
       .str();
 }

 static void validateLength(MemoryBufferRef mb, const section_64 &sec,
                            const relocation_info &rel,
                            const std::vector<uint8_t> &validLengths) {
   if (std::find(validLengths.begin(), validLengths.end(), rel.r_length) !=
       validLengths.end())
     return;

   std::string msg = getErrorLocation(mb, sec, rel) + ": relocations of type " +
                     std::to_string(rel.r_type) + " must have r_length of ";
   bool first = true;
   for (uint8_t length : validLengths) {
     if (!first)
       msg += " or ";
     first = false;
     msg += std::to_string(length);
   }
   fatal(msg);
 }

 uint64_t X86_64::getImplicitAddend(MemoryBufferRef mb, const section_64 &sec,
                                    const relocation_info &rel) const {
   auto *buf = reinterpret_cast<const uint8_t *>(mb.getBufferStart());
   const uint8_t *loc = buf + sec.offset + rel.r_address;
   switch (rel.r_type) {
   case X86_64_RELOC_BRANCH:
     // XXX: ld64 also supports r_length = 0 here but I'm not sure when such a
     // relocation will actually be generated.
     validateLength(mb, sec, rel, {2});
     break;
   case X86_64_RELOC_SIGNED:
   case X86_64_RELOC_SIGNED_1:
   case X86_64_RELOC_SIGNED_2:
   case X86_64_RELOC_SIGNED_4:
   case X86_64_RELOC_GOT_LOAD:
   case X86_64_RELOC_GOT:
     if (!rel.r_pcrel)
       fatal(getErrorLocation(mb, sec, rel) + ": relocations of type " +
             std::to_string(rel.r_type) + " must be pcrel");
     validateLength(mb, sec, rel, {2});
     break;
   case X86_64_RELOC_UNSIGNED:
     if (rel.r_pcrel)
       fatal(getErrorLocation(mb, sec, rel) + ": relocations of type " +
             std::to_string(rel.r_type) + " must not be pcrel");
     validateLength(mb, sec, rel, {2, 3});
     break;
   default:
     error("TODO: Unhandled relocation type " + std::to_string(rel.r_type));
     return 0;
   }

   switch (rel.r_length) {
   case 0:
     return *loc;
   case 1:
     return read16le(loc);
   case 2:
     return read32le(loc);
   case 3:
     return read64le(loc);
   default:
     llvm_unreachable("invalid r_length");
   }
 }

 void X86_64::relocateOne(uint8_t *loc, const Reloc &r, uint64_t val) const {
   switch (r.type) {
   case X86_64_RELOC_BRANCH:
   case X86_64_RELOC_SIGNED:
   case X86_64_RELOC_SIGNED_1:
   case X86_64_RELOC_SIGNED_2:
   case X86_64_RELOC_SIGNED_4:
   case X86_64_RELOC_GOT_LOAD:
   case X86_64_RELOC_GOT:
     // These types are only used for pc-relative relocations, so offset by 4
     // since the RIP has advanced by 4 at this point. This is only valid when
     // r_length = 2, which is enforced by validateLength().
     val -= 4;
     break;
   case X86_64_RELOC_UNSIGNED:
     break;
   default:
     llvm_unreachable(
         "getImplicitAddend should have flagged all unhandled relocation types");
   }

   switch (r.length) {
   case 0:
     *loc = val;
     break;
   case 1:
     write16le(loc, val);
     break;
   case 2:
     write32le(loc, val);
     break;
   case 3:
     write64le(loc, val);
     break;
   default:
     llvm_unreachable("invalid r_length");
   }
 }

 // The following methods emit a number of assembly sequences with RIP-relative
 // addressing. Note that RIP-relative addressing on X86-64 has the RIP pointing
 // to the next instruction, not the current instruction, so we always have to
 // account for the current instruction's size when calculating offsets.
 // writeRipRelative helps with that.
 //
 // bufAddr:  The virtual address corresponding to buf[0].
 // bufOff:   The offset within buf of the next instruction.
 // destAddr: The destination address that the current instruction references.
 static void writeRipRelative(uint8_t *buf, uint64_t bufAddr, uint64_t bufOff,
                              uint64_t destAddr) {
   uint64_t rip = bufAddr + bufOff;
   // For the instructions we care about, the RIP-relative address is always
   // stored in the last 4 bytes of the instruction.
   write32le(buf + bufOff - 4, destAddr - rip);
 }

 static constexpr uint8_t stub[] = {
     0xff, 0x25, 0, 0, 0, 0, // jmpq *__la_symbol_ptr(%rip)
 };

 void X86_64::writeStub(uint8_t *buf, const DylibSymbol &sym) const {
   memcpy(buf, stub, 2); // just copy the two nonzero bytes
   uint64_t stubAddr = in.stubs->addr + sym.stubsIndex * sizeof(stub);
   writeRipRelative(buf, stubAddr, sizeof(stub),
                    in.lazyPointers->addr + sym.stubsIndex * WordSize);
 }

 static constexpr uint8_t stubHelperHeader[] = {
     0x4c, 0x8d, 0x1d, 0, 0, 0, 0, // 0x0: leaq ImageLoaderCache(%rip), %r11
     0x41, 0x53,                   // 0x7: pushq %r11
     0xff, 0x25, 0,    0, 0, 0,    // 0x9: jmpq *dyld_stub_binder@GOT(%rip)
     0x90,                         // 0xf: nop
 };

 static constexpr uint8_t stubHelperEntry[] = {
     0x68, 0, 0, 0, 0, // 0x0: pushq <bind offset>
     0xe9, 0, 0, 0, 0, // 0x5: jmp <__stub_helper>
 };

 void X86_64::writeStubHelperHeader(uint8_t *buf) const {
   memcpy(buf, stubHelperHeader, sizeof(stubHelperHeader));
   writeRipRelative(buf, in.stubHelper->addr, 7, in.imageLoaderCache->getVA());
   writeRipRelative(buf, in.stubHelper->addr, 0xf,
                    in.got->addr +
                        in.stubHelper->stubBinder->gotIndex * WordSize);
 }

 void X86_64::writeStubHelperEntry(uint8_t *buf, const DylibSymbol &sym,
                                   uint64_t entryAddr) const {
   memcpy(buf, stubHelperEntry, sizeof(stubHelperEntry));
   write32le(buf + 1, sym.lazyBindOffset);
   writeRipRelative(buf, entryAddr, sizeof(stubHelperEntry),
                    in.stubHelper->addr);
 }

 void X86_64::prepareSymbolRelocation(lld::macho::Symbol &sym,
                                      const InputSection *isec, const Reloc &r) {
   switch (r.type) {
   case X86_64_RELOC_GOT_LOAD:
     // TODO: implement mov -> lea relaxation for non-dynamic symbols
   case X86_64_RELOC_GOT:
     in.got->addEntry(sym);
     break;
   case X86_64_RELOC_BRANCH: {
     if (auto *dysym = dyn_cast<DylibSymbol>(&sym))
       in.stubs->addEntry(*dysym);
     break;
   }
   case X86_64_RELOC_UNSIGNED: {
     if (auto *dysym = dyn_cast<DylibSymbol>(&sym)) {
       if (r.length != 3) {
         error("X86_64_RELOC_UNSIGNED referencing the dynamic symbol " +
               dysym->getName() + " must have r_length = 3");
         return;
       }
       in.binding->addEntry(dysym, isec, r.offset, r.addend);
     }
     break;
   }
   case X86_64_RELOC_SIGNED:
   case X86_64_RELOC_SIGNED_1:
   case X86_64_RELOC_SIGNED_2:
   case X86_64_RELOC_SIGNED_4:
     break;
   case X86_64_RELOC_SUBTRACTOR:
   case X86_64_RELOC_TLV:
     fatal("TODO: handle relocation type " + std::to_string(r.type));
     break;
   default:
     llvm_unreachable("unexpected relocation type");
   }
 }

 uint64_t X86_64::getSymbolVA(const lld::macho::Symbol &sym,
                              uint8_t type) const {
   switch (type) {
   case X86_64_RELOC_GOT_LOAD:
   case X86_64_RELOC_GOT:
     return in.got->addr + sym.gotIndex * WordSize;
   case X86_64_RELOC_BRANCH:
     if (auto *dysym = dyn_cast<DylibSymbol>(&sym))
       return in.stubs->addr + dysym->stubsIndex * sizeof(stub);
     return sym.getVA();
   case X86_64_RELOC_UNSIGNED:
   case X86_64_RELOC_SIGNED:
   case X86_64_RELOC_SIGNED_1:
   case X86_64_RELOC_SIGNED_2:
   case X86_64_RELOC_SIGNED_4:
     return sym.getVA();
   case X86_64_RELOC_SUBTRACTOR:
   case X86_64_RELOC_TLV:
     fatal("TODO: handle relocation type " + std::to_string(type));
   default:
     llvm_unreachable("Unexpected relocation type");
   }
 }

 X86_64::X86_64() {
   cpuType = CPU_TYPE_X86_64;
   cpuSubtype = CPU_SUBTYPE_X86_64_ALL;

   stubSize = sizeof(stub);
   stubHelperHeaderSize = sizeof(stubHelperHeader);
   stubHelperEntrySize = sizeof(stubHelperEntry);
 }

 TargetInfo *macho::createX86_64TargetInfo() {
   static X86_64 t;
   return &t;
 }
	//===- X86_64.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 "InputFiles.h"
	#include "Symbols.h"
	#include "SyntheticSections.h"
	#include "Target.h"

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

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

	namespace {

	struct X86_64 : TargetInfo {
	X86_64();

	uint64_t getImplicitAddend(MemoryBufferRef, const section_64 &,
	const relocation_info &) const override;
	void relocateOne(uint8_t *loc, const Reloc &, uint64_t val) const override;

	void writeStub(uint8_t *buf, const DylibSymbol &) const override;
	void writeStubHelperHeader(uint8_t *buf) const override;
	void writeStubHelperEntry(uint8_t *buf, const DylibSymbol &,
	uint64_t entryAddr) const override;

	void prepareSymbolRelocation(lld::macho::Symbol &, const InputSection *,
	const Reloc &) override;
	uint64_t getSymbolVA(const lld::macho::Symbol &, uint8_t type) const override;
	};

	} // namespace

	static std::string getErrorLocation(MemoryBufferRef mb, const section_64 &sec,
	const relocation_info &rel) {
	return ("invalid relocation at offset " + std::to_string(rel.r_address) +
	" of " + sec.segname + "," + sec.sectname + " in " +
	mb.getBufferIdentifier())
	.str();
	}

	static void validateLength(MemoryBufferRef mb, const section_64 &sec,
	const relocation_info &rel,
	const std::vector<uint8_t> &validLengths) {
	if (std::find(validLengths.begin(), validLengths.end(), rel.r_length) !=
	validLengths.end())
	return;

	std::string msg = getErrorLocation(mb, sec, rel) + ": relocations of type " +
	std::to_string(rel.r_type) + " must have r_length of ";
	bool first = true;
	for (uint8_t length : validLengths) {
	if (!first)
	msg += " or ";
	first = false;
	msg += std::to_string(length);
	}
	fatal(msg);
	}

	uint64_t X86_64::getImplicitAddend(MemoryBufferRef mb, const section_64 &sec,
	const relocation_info &rel) const {
	auto buf = reinterpret_cast<const uint8_t >(mb.getBufferStart());
	const uint8_t *loc = buf + sec.offset + rel.r_address;
	switch (rel.r_type) {
	case X86_64_RELOC_BRANCH:
	// XXX: ld64 also supports r_length = 0 here but I'm not sure when such a
	// relocation will actually be generated.
	validateLength(mb, sec, rel, {2});
	break;
	case X86_64_RELOC_SIGNED:
	case X86_64_RELOC_SIGNED_1:
	case X86_64_RELOC_SIGNED_2:
	case X86_64_RELOC_SIGNED_4:
	case X86_64_RELOC_GOT_LOAD:
	case X86_64_RELOC_GOT:
	if (!rel.r_pcrel)
	fatal(getErrorLocation(mb, sec, rel) + ": relocations of type " +
	std::to_string(rel.r_type) + " must be pcrel");
	validateLength(mb, sec, rel, {2});
	break;
	case X86_64_RELOC_UNSIGNED:
	if (rel.r_pcrel)
	fatal(getErrorLocation(mb, sec, rel) + ": relocations of type " +
	std::to_string(rel.r_type) + " must not be pcrel");
	validateLength(mb, sec, rel, {2, 3});
	break;
	default:
	error("TODO: Unhandled relocation type " + std::to_string(rel.r_type));
	return 0;
	}

	switch (rel.r_length) {
	case 0:
	return *loc;
	case 1:
	return read16le(loc);
	case 2:
	return read32le(loc);
	case 3:
	return read64le(loc);
	default:
	llvm_unreachable("invalid r_length");
	}
	}

	void X86_64::relocateOne(uint8_t *loc, const Reloc &r, uint64_t val) const {
	switch (r.type) {
	case X86_64_RELOC_BRANCH:
	case X86_64_RELOC_SIGNED:
	case X86_64_RELOC_SIGNED_1:
	case X86_64_RELOC_SIGNED_2:
	case X86_64_RELOC_SIGNED_4:
	case X86_64_RELOC_GOT_LOAD:
	case X86_64_RELOC_GOT:
	// These types are only used for pc-relative relocations, so offset by 4
	// since the RIP has advanced by 4 at this point. This is only valid when
	// r_length = 2, which is enforced by validateLength().
	val -= 4;
	break;
	case X86_64_RELOC_UNSIGNED:
	break;
	default:
	llvm_unreachable(
	"getImplicitAddend should have flagged all unhandled relocation types");
	}

	switch (r.length) {
	case 0:
	*loc = val;
	break;
	case 1:
	write16le(loc, val);
	break;
	case 2:
	write32le(loc, val);
	break;
	case 3:
	write64le(loc, val);
	break;
	default:
	llvm_unreachable("invalid r_length");
	}
	}

	// The following methods emit a number of assembly sequences with RIP-relative
	// addressing. Note that RIP-relative addressing on X86-64 has the RIP pointing
	// to the next instruction, not the current instruction, so we always have to
	// account for the current instruction's size when calculating offsets.
	// writeRipRelative helps with that.
	//
	// bufAddr: The virtual address corresponding to buf[0].
	// bufOff: The offset within buf of the next instruction.
	// destAddr: The destination address that the current instruction references.
	static void writeRipRelative(uint8_t *buf, uint64_t bufAddr, uint64_t bufOff,
	uint64_t destAddr) {
	uint64_t rip = bufAddr + bufOff;
	// For the instructions we care about, the RIP-relative address is always
	// stored in the last 4 bytes of the instruction.
	write32le(buf + bufOff - 4, destAddr - rip);
	}

	static constexpr uint8_t stub[] = {
	0xff, 0x25, 0, 0, 0, 0, // jmpq *__la_symbol_ptr(%rip)
	};

	void X86_64::writeStub(uint8_t *buf, const DylibSymbol &sym) const {
	memcpy(buf, stub, 2); // just copy the two nonzero bytes
	uint64_t stubAddr = in.stubs->addr + sym.stubsIndex * sizeof(stub);
	writeRipRelative(buf, stubAddr, sizeof(stub),
	in.lazyPointers->addr + sym.stubsIndex * WordSize);
	}

	static constexpr uint8_t stubHelperHeader[] = {
	0x4c, 0x8d, 0x1d, 0, 0, 0, 0, // 0x0: leaq ImageLoaderCache(%rip), %r11
	0x41, 0x53, // 0x7: pushq %r11
	0xff, 0x25, 0, 0, 0, 0, // 0x9: jmpq *dyld_stub_binder@GOT(%rip)
	0x90, // 0xf: nop
	};

	static constexpr uint8_t stubHelperEntry[] = {
	0x68, 0, 0, 0, 0, // 0x0: pushq <bind offset>
	0xe9, 0, 0, 0, 0, // 0x5: jmp <__stub_helper>
	};

	void X86_64::writeStubHelperHeader(uint8_t *buf) const {
	memcpy(buf, stubHelperHeader, sizeof(stubHelperHeader));
	writeRipRelative(buf, in.stubHelper->addr, 7, in.imageLoaderCache->getVA());
	writeRipRelative(buf, in.stubHelper->addr, 0xf,
	in.got->addr +
	in.stubHelper->stubBinder->gotIndex * WordSize);
	}

	void X86_64::writeStubHelperEntry(uint8_t *buf, const DylibSymbol &sym,
	uint64_t entryAddr) const {
	memcpy(buf, stubHelperEntry, sizeof(stubHelperEntry));
	write32le(buf + 1, sym.lazyBindOffset);
	writeRipRelative(buf, entryAddr, sizeof(stubHelperEntry),
	in.stubHelper->addr);
	}

	void X86_64::prepareSymbolRelocation(lld::macho::Symbol &sym,
	const InputSection *isec, const Reloc &r) {
	switch (r.type) {
	case X86_64_RELOC_GOT_LOAD:
	// TODO: implement mov -> lea relaxation for non-dynamic symbols
	case X86_64_RELOC_GOT:
	in.got->addEntry(sym);
	break;
	case X86_64_RELOC_BRANCH: {
	if (auto *dysym = dyn_cast<DylibSymbol>(&sym))
	in.stubs->addEntry(*dysym);
	break;
	}
	case X86_64_RELOC_UNSIGNED: {
	if (auto *dysym = dyn_cast<DylibSymbol>(&sym)) {
	if (r.length != 3) {
	error("X86_64_RELOC_UNSIGNED referencing the dynamic symbol " +
	dysym->getName() + " must have r_length = 3");
	return;
	}
	in.binding->addEntry(dysym, isec, r.offset, r.addend);
	}
	break;
	}
	case X86_64_RELOC_SIGNED:
	case X86_64_RELOC_SIGNED_1:
	case X86_64_RELOC_SIGNED_2:
	case X86_64_RELOC_SIGNED_4:
	break;
	case X86_64_RELOC_SUBTRACTOR:
	case X86_64_RELOC_TLV:
	fatal("TODO: handle relocation type " + std::to_string(r.type));
	break;
	default:
	llvm_unreachable("unexpected relocation type");
	}
	}

	uint64_t X86_64::getSymbolVA(const lld::macho::Symbol &sym,
	uint8_t type) const {
	switch (type) {
	case X86_64_RELOC_GOT_LOAD:
	case X86_64_RELOC_GOT:
	return in.got->addr + sym.gotIndex * WordSize;
	case X86_64_RELOC_BRANCH:
	if (auto *dysym = dyn_cast<DylibSymbol>(&sym))
	return in.stubs->addr + dysym->stubsIndex * sizeof(stub);
	return sym.getVA();
	case X86_64_RELOC_UNSIGNED:
	case X86_64_RELOC_SIGNED:
	case X86_64_RELOC_SIGNED_1:
	case X86_64_RELOC_SIGNED_2:
	case X86_64_RELOC_SIGNED_4:
	return sym.getVA();
	case X86_64_RELOC_SUBTRACTOR:
	case X86_64_RELOC_TLV:
	fatal("TODO: handle relocation type " + std::to_string(type));
	default:
	llvm_unreachable("Unexpected relocation type");
	}
	}

	X86_64::X86_64() {
	cpuType = CPU_TYPE_X86_64;
	cpuSubtype = CPU_SUBTYPE_X86_64_ALL;

	stubSize = sizeof(stub);
	stubHelperHeaderSize = sizeof(stubHelperHeader);
	stubHelperEntrySize = sizeof(stubHelperEntry);
	}

	TargetInfo *macho::createX86_64TargetInfo() {
	static X86_64 t;
	return &t;
	}