1 files changed, 363 insertions, 0 deletions
diff --git a/lld/ELF/Arch/X86.cpp b/lld/ELF/Arch/X86.cpp
new file mode 100644
index 00000000000..bc0d2b81a61
--- /dev/null
+++ b/lld/ELF/Arch/X86.cpp
@@ -0,0 +1,363 @@
+//===- X86.cpp ------------------------------------------------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Error.h"
+#include "InputFiles.h"
+#include "Memory.h"
+#include "Symbols.h"
+#include "SyntheticSections.h"
+#include "Target.h"
+#include "llvm/Support/Endian.h"
+
+using namespace llvm;
+using namespace llvm::support::endian;
+using namespace llvm::ELF;
+using namespace lld;
+using namespace lld::elf;
+
+namespace {
+class X86 final : public TargetInfo {
+public:
+  X86();
+  RelExpr getRelExpr(uint32_t Type, const SymbolBody &S,
+                     const uint8_t *Loc) const override;
+  int64_t getImplicitAddend(const uint8_t *Buf, uint32_t Type) const override;
+  void writeGotPltHeader(uint8_t *Buf) const override;
+  uint32_t getDynRel(uint32_t Type) const override;
+  void writeGotPlt(uint8_t *Buf, const SymbolBody &S) const override;
+  void writeIgotPlt(uint8_t *Buf, const SymbolBody &S) const override;
+  void writePltHeader(uint8_t *Buf) const override;
+  void writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr, uint64_t PltEntryAddr,
+                int32_t Index, unsigned RelOff) const override;
+  void relocateOne(uint8_t *Loc, uint32_t Type, uint64_t Val) const override;
+
+  RelExpr adjustRelaxExpr(uint32_t Type, const uint8_t *Data,
+                          RelExpr Expr) const override;
+  void relaxTlsGdToIe(uint8_t *Loc, uint32_t Type, uint64_t Val) const override;
+  void relaxTlsGdToLe(uint8_t *Loc, uint32_t Type, uint64_t Val) const override;
+  void relaxTlsIeToLe(uint8_t *Loc, uint32_t Type, uint64_t Val) const override;
+  void relaxTlsLdToLe(uint8_t *Loc, uint32_t Type, uint64_t Val) const override;
+};
+} // namespace
+
+X86::X86() {
+  CopyRel = R_386_COPY;
+  GotRel = R_386_GLOB_DAT;
+  PltRel = R_386_JUMP_SLOT;
+  IRelativeRel = R_386_IRELATIVE;
+  RelativeRel = R_386_RELATIVE;
+  TlsGotRel = R_386_TLS_TPOFF;
+  TlsModuleIndexRel = R_386_TLS_DTPMOD32;
+  TlsOffsetRel = R_386_TLS_DTPOFF32;
+  GotEntrySize = 4;
+  GotPltEntrySize = 4;
+  PltEntrySize = 16;
+  PltHeaderSize = 16;
+  TlsGdRelaxSkip = 2;
+
+  // 0xCC is the "int3" (call debug exception handler) instruction.
+  TrapInstr = 0xcccccccc;
+}
+
+RelExpr X86::getRelExpr(uint32_t Type, const SymbolBody &S,
+                        const uint8_t *Loc) const {
+  switch (Type) {
+  case R_386_8:
+  case R_386_16:
+  case R_386_32:
+  case R_386_TLS_LDO_32:
+    return R_ABS;
+  case R_386_TLS_GD:
+    return R_TLSGD;
+  case R_386_TLS_LDM:
+    return R_TLSLD;
+  case R_386_PLT32:
+    return R_PLT_PC;
+  case R_386_PC8:
+  case R_386_PC16:
+  case R_386_PC32:
+    return R_PC;
+  case R_386_GOTPC:
+    return R_GOTONLY_PC_FROM_END;
+  case R_386_TLS_IE:
+    return R_GOT;
+  case R_386_GOT32:
+  case R_386_GOT32X:
+    // These relocations can be calculated in two different ways.
+    // Usual calculation is G + A - GOT what means an offset in GOT table
+    // (R_GOT_FROM_END). When instruction pointed by relocation has no base
+    // register, then relocations can be used when PIC code is disabled. In that
+    // case calculation is G + A, it resolves to an address of entry in GOT
+    // (R_GOT) and not an offset.
+    //
+    // To check that instruction has no base register we scan ModR/M byte.
+    // See "Table 2-2. 32-Bit Addressing Forms with the ModR/M Byte"
+    // (http://www.intel.com/content/dam/www/public/us/en/documents/manuals/
+    //  64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf)
+    if ((Loc[-1] & 0xc7) != 0x5)
+      return R_GOT_FROM_END;
+    if (Config->Pic)
+      error(toString(S.File) + ": relocation " + toString(Type) + " against '" +
+            S.getName() +
+            "' without base register can not be used when PIC enabled");
+    return R_GOT;
+  case R_386_TLS_GOTIE:
+    return R_GOT_FROM_END;
+  case R_386_GOTOFF:
+    return R_GOTREL_FROM_END;
+  case R_386_TLS_LE:
+    return R_TLS;
+  case R_386_TLS_LE_32:
+    return R_NEG_TLS;
+  case R_386_NONE:
+    return R_NONE;
+  default:
+    error(toString(S.File) + ": unknown relocation type: " + toString(Type));
+    return R_HINT;
+  }
+}
+
+RelExpr X86::adjustRelaxExpr(uint32_t Type, const uint8_t *Data,
+                             RelExpr Expr) const {
+  switch (Expr) {
+  default:
+    return Expr;
+  case R_RELAX_TLS_GD_TO_IE:
+    return R_RELAX_TLS_GD_TO_IE_END;
+  case R_RELAX_TLS_GD_TO_LE:
+    return R_RELAX_TLS_GD_TO_LE_NEG;
+  }
+}
+
+void X86::writeGotPltHeader(uint8_t *Buf) const {
+  write32le(Buf, InX::Dynamic->getVA());
+}
+
+void X86::writeGotPlt(uint8_t *Buf, const SymbolBody &S) const {
+  // Entries in .got.plt initially points back to the corresponding
+  // PLT entries with a fixed offset to skip the first instruction.
+  write32le(Buf, S.getPltVA() + 6);
+}
+
+void X86::writeIgotPlt(uint8_t *Buf, const SymbolBody &S) const {
+  // An x86 entry is the address of the ifunc resolver function.
+  write32le(Buf, S.getVA());
+}
+
+uint32_t X86::getDynRel(uint32_t Type) const {
+  if (Type == R_386_TLS_LE)
+    return R_386_TLS_TPOFF;
+  if (Type == R_386_TLS_LE_32)
+    return R_386_TLS_TPOFF32;
+  return Type;
+}
+
+void X86::writePltHeader(uint8_t *Buf) const {
+  if (Config->Pic) {
+    const uint8_t V[] = {
+        0xff, 0xb3, 0x04, 0x00, 0x00, 0x00, // pushl GOTPLT+4(%ebx)
+        0xff, 0xa3, 0x08, 0x00, 0x00, 0x00, // jmp *GOTPLT+8(%ebx)
+        0x90, 0x90, 0x90, 0x90              // nop
+    };
+    memcpy(Buf, V, sizeof(V));
+
+    uint32_t Ebx = InX::Got->getVA() + InX::Got->getSize();
+    uint32_t GotPlt = InX::GotPlt->getVA() - Ebx;
+    write32le(Buf + 2, GotPlt + 4);
+    write32le(Buf + 8, GotPlt + 8);
+    return;
+  }
+
+  const uint8_t PltData[] = {
+      0xff, 0x35, 0x00, 0x00, 0x00, 0x00, // pushl (GOTPLT+4)
+      0xff, 0x25, 0x00, 0x00, 0x00, 0x00, // jmp *(GOTPLT+8)
+      0x90, 0x90, 0x90, 0x90              // nop
+  };
+  memcpy(Buf, PltData, sizeof(PltData));
+  uint32_t GotPlt = InX::GotPlt->getVA();
+  write32le(Buf + 2, GotPlt + 4);
+  write32le(Buf + 8, GotPlt + 8);
+}
+
+void X86::writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr,
+                   uint64_t PltEntryAddr, int32_t Index,
+                   unsigned RelOff) const {
+  const uint8_t Inst[] = {
+      0xff, 0x00, 0x00, 0x00, 0x00, 0x00, // jmp *foo_in_GOT|*foo@GOT(%ebx)
+      0x68, 0x00, 0x00, 0x00, 0x00,       // pushl $reloc_offset
+      0xe9, 0x00, 0x00, 0x00, 0x00        // jmp .PLT0@PC
+  };
+  memcpy(Buf, Inst, sizeof(Inst));
+
+  if (Config->Pic) {
+    // jmp *foo@GOT(%ebx)
+    uint32_t Ebx = InX::Got->getVA() + InX::Got->getSize();
+    Buf[1] = 0xa3;
+    write32le(Buf + 2, GotPltEntryAddr - Ebx);
+  } else {
+    // jmp *foo_in_GOT
+    Buf[1] = 0x25;
+    write32le(Buf + 2, GotPltEntryAddr);
+  }
+
+  write32le(Buf + 7, RelOff);
+  write32le(Buf + 12, -Index * PltEntrySize - PltHeaderSize - 16);
+}
+
+int64_t X86::getImplicitAddend(const uint8_t *Buf, uint32_t Type) const {
+  switch (Type) {
+  default:
+    return 0;
+  case R_386_8:
+  case R_386_PC8:
+    return SignExtend64<8>(*Buf);
+  case R_386_16:
+  case R_386_PC16:
+    return SignExtend64<16>(read16le(Buf));
+  case R_386_32:
+  case R_386_GOT32:
+  case R_386_GOT32X:
+  case R_386_GOTOFF:
+  case R_386_GOTPC:
+  case R_386_PC32:
+  case R_386_PLT32:
+  case R_386_TLS_LDO_32:
+  case R_386_TLS_LE:
+    return SignExtend64<32>(read32le(Buf));
+  }
+}
+
+void X86::relocateOne(uint8_t *Loc, uint32_t Type, uint64_t Val) const {
+  // R_386_{PC,}{8,16} are not part of the i386 psABI, but they are
+  // being used for some 16-bit programs such as boot loaders, so
+  // we want to support them.
+  switch (Type) {
+  case R_386_8:
+    checkUInt<8>(Loc, Val, Type);
+    *Loc = Val;
+    break;
+  case R_386_PC8:
+    checkInt<8>(Loc, Val, Type);
+    *Loc = Val;
+    break;
+  case R_386_16:
+    checkUInt<16>(Loc, Val, Type);
+    write16le(Loc, Val);
+    break;
+  case R_386_PC16:
+    // R_386_PC16 is normally used with 16 bit code. In that situation
+    // the PC is 16 bits, just like the addend. This means that it can
+    // point from any 16 bit address to any other if the possibility
+    // of wrapping is included.
+    // The only restriction we have to check then is that the destination
+    // address fits in 16 bits. That is impossible to do here. The problem is
+    // that we are passed the final value, which already had the
+    // current location subtracted from it.
+    // We just check that Val fits in 17 bits. This misses some cases, but
+    // should have no false positives.
+    checkInt<17>(Loc, Val, Type);
+    write16le(Loc, Val);
+    break;
+  default:
+    checkInt<32>(Loc, Val, Type);
+    write32le(Loc, Val);
+  }
+}
+
+void X86::relaxTlsGdToLe(uint8_t *Loc, uint32_t Type, uint64_t Val) const {
+  // Convert
+  //   leal x@tlsgd(, %ebx, 1),
+  //   call __tls_get_addr@plt
+  // to
+  //   movl %gs:0,%eax
+  //   subl $x@ntpoff,%eax
+  const uint8_t Inst[] = {
+      0x65, 0xa1, 0x00, 0x00, 0x00, 0x00, // movl %gs:0, %eax
+      0x81, 0xe8, 0x00, 0x00, 0x00, 0x00  // subl 0(%ebx), %eax
+  };
+  memcpy(Loc - 3, Inst, sizeof(Inst));
+  write32le(Loc + 5, Val);
+}
+
+void X86::relaxTlsGdToIe(uint8_t *Loc, uint32_t Type, uint64_t Val) const {
+  // Convert
+  //   leal x@tlsgd(, %ebx, 1),
+  //   call __tls_get_addr@plt
+  // to
+  //   movl %gs:0, %eax
+  //   addl x@gotntpoff(%ebx), %eax
+  const uint8_t Inst[] = {
+      0x65, 0xa1, 0x00, 0x00, 0x00, 0x00, // movl %gs:0, %eax
+      0x03, 0x83, 0x00, 0x00, 0x00, 0x00  // addl 0(%ebx), %eax
+  };
+  memcpy(Loc - 3, Inst, sizeof(Inst));
+  write32le(Loc + 5, Val);
+}
+
+// In some conditions, relocations can be optimized to avoid using GOT.
+// This function does that for Initial Exec to Local Exec case.
+void X86::relaxTlsIeToLe(uint8_t *Loc, uint32_t Type, uint64_t Val) const {
+  // Ulrich's document section 6.2 says that @gotntpoff can
+  // be used with MOVL or ADDL instructions.
+  // @indntpoff is similar to @gotntpoff, but for use in
+  // position dependent code.
+  uint8_t Reg = (Loc[-1] >> 3) & 7;
+
+  if (Type == R_386_TLS_IE) {
+    if (Loc[-1] == 0xa1) {
+      // "movl foo@indntpoff,%eax" -> "movl $foo,%eax"
+      // This case is different from the generic case below because
+      // this is a 5 byte instruction while below is 6 bytes.
+      Loc[-1] = 0xb8;
+    } else if (Loc[-2] == 0x8b) {
+      // "movl foo@indntpoff,%reg" -> "movl $foo,%reg"
+      Loc[-2] = 0xc7;
+      Loc[-1] = 0xc0 | Reg;
+    } else {
+      // "addl foo@indntpoff,%reg" -> "addl $foo,%reg"
+      Loc[-2] = 0x81;
+      Loc[-1] = 0xc0 | Reg;
+    }
+  } else {
+    assert(Type == R_386_TLS_GOTIE);
+    if (Loc[-2] == 0x8b) {
+      // "movl foo@gottpoff(%rip),%reg" -> "movl $foo,%reg"
+      Loc[-2] = 0xc7;
+      Loc[-1] = 0xc0 | Reg;
+    } else {
+      // "addl foo@gotntpoff(%rip),%reg" -> "leal foo(%reg),%reg"
+      Loc[-2] = 0x8d;
+      Loc[-1] = 0x80 | (Reg << 3) | Reg;
+    }
+  }
+  write32le(Loc, Val);
+}
+
+void X86::relaxTlsLdToLe(uint8_t *Loc, uint32_t Type, uint64_t Val) const {
+  if (Type == R_386_TLS_LDO_32) {
+    write32le(Loc, Val);
+    return;
+  }
+
+  // Convert
+  //   leal foo(%reg),%eax
+  //   call ___tls_get_addr
+  // to
+  //   movl %gs:0,%eax
+  //   nop
+  //   leal 0(%esi,1),%esi
+  const uint8_t Inst[] = {
+      0x65, 0xa1, 0x00, 0x00, 0x00, 0x00, // movl %gs:0,%eax
+      0x90,                               // nop
+      0x8d, 0x74, 0x26, 0x00              // leal 0(%esi,1),%esi
+  };
+  memcpy(Loc - 2, Inst, sizeof(Inst));
+}
+
+TargetInfo *elf::createX86TargetInfo() { return make<X86>(); }