[lld] [lld] Add target support for SystemZ (s390x) (PR #75643)

Fangrui Song via llvm-commits llvm-commits at lists.llvm.org
Tue Dec 19 17:40:25 PST 2023


================
@@ -0,0 +1,581 @@
+//===- SystemZ.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 "OutputSections.h"
+#include "Symbols.h"
+#include "SyntheticSections.h"
+#include "Target.h"
+#include "lld/Common/ErrorHandler.h"
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/Support/Endian.h"
+
+using namespace llvm;
+using namespace llvm::object;
+using namespace llvm::support::endian;
+using namespace llvm::ELF;
+using namespace lld;
+using namespace lld::elf;
+
+namespace {
+class SystemZ : public TargetInfo {
+public:
+  SystemZ();
+  RelExpr getRelExpr(RelType type, const Symbol &s,
+                     const uint8_t *loc) const override;
+  RelType getDynRel(RelType type) const override;
+  void writeGotHeader(uint8_t *buf) const override;
+  void writeGotPlt(uint8_t *buf, const Symbol &s) const override;
+  void writeIgotPlt(uint8_t *buf, const Symbol &s) const override;
+  void writePltHeader(uint8_t *buf) const override;
+  void writePlt(uint8_t *buf, const Symbol &sym,
+                uint64_t pltEntryAddr) const override;
+  RelExpr adjustTlsExpr(RelType type, RelExpr expr) const override;
+  RelExpr adjustGotPcExpr(RelType type, int64_t addend,
+                          const uint8_t *loc) const override;
+  bool relaxOnce(int pass) const override;
+  void relocate(uint8_t *loc, const Relocation &rel,
+                uint64_t val) const override;
+  int64_t getImplicitAddend(const uint8_t *buf, RelType type) const override;
+private:
+  void relaxGot(uint8_t *loc, const Relocation &rel, uint64_t val) const;
+  void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
+  void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
+  void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
+};
+} // namespace
+
+SystemZ::SystemZ() {
+  copyRel = R_390_COPY;
+  gotRel = R_390_GLOB_DAT;
+  pltRel = R_390_JMP_SLOT;
+  relativeRel = R_390_RELATIVE;
+  iRelativeRel = R_390_IRELATIVE;
+  symbolicRel = R_390_64;
+  tlsGotRel = R_390_TLS_TPOFF;
+  tlsModuleIndexRel = R_390_TLS_DTPMOD;
+  tlsOffsetRel = R_390_TLS_DTPOFF;
+  gotHeaderEntriesNum = 3;
+  gotPltHeaderEntriesNum = 0;
+  gotEntrySize = 8;
+  pltHeaderSize = 32;
+  pltEntrySize = 32;
+  ipltEntrySize = 32;
+
+  // This "trap instruction" is used to fill gaps between sections.
+  // On SystemZ, the behavior of the GNU ld is to fill those gaps
+  // with nop instructions instead - and unfortunately the default
+  // glibc crt object files (used to) rely on that behavior since
+  // they use an alignment on the .init section fragments that causes
+  // gaps which must be filled with nops as they are being executed.
+  // Therefore, we provide a nop instruction as "trapInstr" here.
+  trapInstr = {0x07, 0x07, 0x07, 0x07};
+
+  defaultImageBase = 0x1000000;
+}
+
+RelExpr SystemZ::getRelExpr(RelType type, const Symbol &s,
+                            const uint8_t *loc) const {
+  switch (type) {
+  case R_390_NONE:
+    return R_NONE;
+  // Relocations targeting the symbol value.
+  case R_390_8:
+  case R_390_12:
+  case R_390_16:
+  case R_390_20:
+  case R_390_32:
+  case R_390_64:
+    return R_ABS;
+  case R_390_PC16:
+  case R_390_PC32:
+  case R_390_PC64:
+  case R_390_PC12DBL:
+  case R_390_PC16DBL:
+  case R_390_PC24DBL:
+  case R_390_PC32DBL:
+    return R_PC;
+  case R_390_GOTOFF16:
+  case R_390_GOTOFF: // a.k.a. R_390_GOTOFF32
+  case R_390_GOTOFF64:
+    return R_GOTREL;
+  // Relocations targeting the PLT associated with the symbol.
+  case R_390_PLT32:
+  case R_390_PLT64:
+  case R_390_PLT12DBL:
+  case R_390_PLT16DBL:
+  case R_390_PLT24DBL:
+  case R_390_PLT32DBL:
+    return R_PLT_PC;
+  case R_390_PLTOFF16:
+  case R_390_PLTOFF32:
+  case R_390_PLTOFF64:
+    return R_PLT_GOTREL;
+  // Relocations targeting the GOT entry associated with the symbol.
+  case R_390_GOTENT:
+    return R_GOT_PC;
+  case R_390_GOT12:
+  case R_390_GOT16:
+  case R_390_GOT20:
+  case R_390_GOT32:
+  case R_390_GOT64:
+    return R_GOT_OFF;
+  // Relocations targeting the GOTPLT entry associated with the symbol.
+  case R_390_GOTPLTENT:
+    return R_GOTPLT_PC;
+  case R_390_GOTPLT12:
+  case R_390_GOTPLT16:
+  case R_390_GOTPLT20:
+  case R_390_GOTPLT32:
+  case R_390_GOTPLT64:
+    return R_GOTPLT_OFF;
+  // Relocations targeting _GLOBAL_OFFSET_TABLE_.
+  case R_390_GOTPC:
+  case R_390_GOTPCDBL:
+    return R_GOTONLY_PC;
+  // TLS-related relocations.
+  case R_390_TLS_LOAD:
+    return R_NONE;
+  case R_390_TLS_GDCALL:
+    return R_TLSGD_PC;
+  case R_390_TLS_LDCALL:
+    return R_TLSLD_PC;
+  case R_390_TLS_GD32:
+  case R_390_TLS_GD64:
+    return R_TLSGD_GOT;
+  case R_390_TLS_LDM32:
+  case R_390_TLS_LDM64:
+    return R_TLSLD_GOT;
+  case R_390_TLS_LDO32:
+  case R_390_TLS_LDO64:
+    return R_DTPREL;
+  case R_390_TLS_LE32:
+  case R_390_TLS_LE64:
+    return R_TPREL;
+  case R_390_TLS_IE32:
+  case R_390_TLS_IE64:
+    return R_GOT;
+  case R_390_TLS_GOTIE12:
+  case R_390_TLS_GOTIE20:
+  case R_390_TLS_GOTIE32:
+  case R_390_TLS_GOTIE64:
+    return R_GOT_OFF;
+  case R_390_TLS_IEENT:
+    return R_GOT_PC;
+
+  default:
+    error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) +
+          ") against symbol " + toString(s));
+    return R_NONE;
+  }
+}
+
+void SystemZ::writeGotHeader(uint8_t *buf) const {
+  // _GLOBAL_OFFSET_TABLE_[0] holds the value of _DYNAMIC.
+  // _GLOBAL_OFFSET_TABLE_[1] and [2] are reserved.
+  write64be(buf, mainPart->dynamic->getVA());
+}
+
+void SystemZ::writeGotPlt(uint8_t *buf, const Symbol &s) const {
+  write64be(buf, s.getPltVA() + 14);
+}
+
+void SystemZ::writeIgotPlt(uint8_t *buf, const Symbol &s) const {
+  if (config->writeAddends)
+    write64be(buf, s.getVA());
+}
+
+void SystemZ::writePltHeader(uint8_t *buf) const {
+  const uint8_t pltData[] = {
+      0xe3, 0x10, 0xf0, 0x38, 0x00, 0x24, // stg     %r1,56(%r15)
+      0xc0, 0x10, 0x00, 0x00, 0x00, 0x00, // larl    %r1,_GLOBAL_OFFSET_TABLE_
+      0xd2, 0x07, 0xf0, 0x30, 0x10, 0x08, // mvc     48(8,%r15),8(%r1)
+      0xe3, 0x10, 0x10, 0x10, 0x00, 0x04, // lg      %r1,16(%r1)
+      0x07, 0xf1,                         // br      %r1
+      0x07, 0x00,                         // nopr
+      0x07, 0x00,                         // nopr
+      0x07, 0x00,                         // nopr
+  };
+  memcpy(buf, pltData, sizeof(pltData));
+  uint64_t got = in.got->getVA();
+  uint64_t plt = in.plt->getVA();
+  write32be(buf + 8, (got - plt - 6) >> 1);
+}
+
+void SystemZ::writePlt(uint8_t *buf, const Symbol &sym,
+                       uint64_t pltEntryAddr) const {
+  const uint8_t inst[] = {
+      0xc0, 0x10, 0x00, 0x00, 0x00, 0x00, // larl    %r1,<.got.plt slot>
+      0xe3, 0x10, 0x10, 0x00, 0x00, 0x04, // lg      %r1,0(%r1)
+      0x07, 0xf1,                         // br      %r1
+      0x0d, 0x10,                         // basr    %r1,%r0
+      0xe3, 0x10, 0x10, 0x0c, 0x00, 0x14, // lgf     %r1,12(%r1)
+      0xc0, 0xf4, 0x00, 0x00, 0x00, 0x00, // jg      <plt header>
+      0x00, 0x00, 0x00, 0x00,             // <relocation offset>
+  };
+  memcpy(buf, inst, sizeof(inst));
+
+  write32be(buf + 2, (sym.getGotPltVA() - pltEntryAddr) >> 1);
+  write32be(buf + 24, (in.plt->getVA() - pltEntryAddr - 22) >> 1);
+  write32be(buf + 28, in.relaPlt->entsize * sym.getPltIdx());
+}
+
+int64_t SystemZ::getImplicitAddend(const uint8_t *buf, RelType type) const {
+  switch (type) {
+  case R_390_8:
+    return SignExtend64<8>(*buf);
+  case R_390_16:
+  case R_390_PC16:
+    return SignExtend64<16>(read16be(buf));
+  case R_390_PC16DBL:
+    return SignExtend64<16>(read16be(buf)) << 1;
+  case R_390_32:
+  case R_390_PC32:
+    return SignExtend64<32>(read32be(buf));
+  case R_390_PC32DBL:
+    return SignExtend64<32>(read32be(buf)) << 1;
+  case R_390_64:
+  case R_390_PC64:
+  case R_390_TLS_DTPMOD:
+  case R_390_TLS_DTPOFF:
+  case R_390_TLS_TPOFF:
+  case R_390_GLOB_DAT:
+  case R_390_RELATIVE:
+  case R_390_IRELATIVE:
+    return read64be(buf);
+  case R_390_COPY:
+  case R_390_JMP_SLOT:
+  case R_390_NONE:
+    // These relocations are defined as not having an implicit addend.
+    return 0;
+  default:
+    internalLinkerError(getErrorLocation(buf),
+                        "cannot read addend for relocation " + toString(type));
+    return 0;
+  }
+}
+
+RelType SystemZ::getDynRel(RelType type) const {
+  if (type == R_390_64 || type == R_390_PC64)
+    return type;
+  return R_390_NONE;
+}
+
+RelExpr SystemZ::adjustTlsExpr(RelType type, RelExpr expr) const {
+  if (expr == R_RELAX_TLS_GD_TO_IE)
+    return R_RELAX_TLS_GD_TO_IE_GOT_OFF;
+  return expr;
+}
+
+void SystemZ::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
+                             uint64_t val) const {
+  // The general-dynamic code sequence for a global `x`:
+  //
+  // Instruction                      Relocation                Symbol
+  // ear %rX,%a0
+  // sllg %rX,%rX,32
+  // ear %rX,%a1
+  // larl %r12,_GLOBAL_OFFSET_TABLE_  R_390_GOTPCDBL            _GLOBAL_OFFSET_TABLE_
+  // lgrl %r2,.LC0                    R_390_PC32DBL             .LC0
+  // brasl %r14,__tls_get_offset at plt  R_390_TLS_GDCALL          x
+  //            :tls_gdcall:x         R_390_PLT32DBL            __tls_get_offset
+  // la %r2,0(%r2,%rX)
+  //
+  // .LC0:
+  // .quad   x at TLSGD                  R_390_TLS_GD64            x
+  //
+  // Relaxing to initial-exec entails:
+  // 1) Replacing the call by a load from the GOT.
+  // 2) Replacing the relocation on the constant LC0 by R_390_TLS_GOTIE64.
+
+  switch (rel.type) {
+  case R_390_TLS_GDCALL:
+    /* brasl %r14,__tls_get_offset at plt -> lg %r2,0(%r2,%r12)  */
+    write16be(loc, 0xe322);
+    write16be(loc + 2, 0xc000);
+    write16be(loc + 4, 0x0004);
+    break;
+  case R_390_TLS_GD64:
+    relocateNoSym(loc, R_390_TLS_GOTIE64, val);
+    break;
+  default:
+    llvm_unreachable("unsupported relocation for TLS GD to IE relaxation");
+  }
+}
+
+void SystemZ::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
+                             uint64_t val) const {
+  // The general-dynamic code sequence for a global `x`:
+  //
+  // Instruction                      Relocation                Symbol
+  // ear %rX,%a0
+  // sllg %rX,%rX,32
+  // ear %rX,%a1
+  // larl %r12,_GLOBAL_OFFSET_TABLE_  R_390_GOTPCDBL            _GLOBAL_OFFSET_TABLE_
+  // lgrl %r2,.LC0                    R_390_PC32DBL             .LC0
+  // brasl %r14,__tls_get_offset at plt  R_390_TLS_GDCALL          x
+  //            :tls_gdcall:x         R_390_PLT32DBL            __tls_get_offset
+  // la %r2,0(%r2,%rX)
+  //
+  // .LC0:
+  // .quad   x at tlsgd                  R_390_TLS_GD64            x
+  //
+  // Relaxing to local-exec entails:
+  // 1) Replacing the call by a nop.
+  // 2) Replacing the relocation on the constant LC0 by R_390_TLS_LE64.
+
+  switch (rel.type) {
+  case R_390_TLS_GDCALL:
+    /* brasl %r14,__tls_get_offset at plt -> brcl 0,. */
+    write16be(loc, 0xc004);
+    write16be(loc + 2, 0x0000);
+    write16be(loc + 4, 0x0000);
+    break;
+  case R_390_TLS_GD64:
+    relocateNoSym(loc, R_390_TLS_LE64, val);
+    break;
+  default:
+    llvm_unreachable("unsupported relocation for TLS GD to LE relaxation");
+  }
+}
+
+void SystemZ::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
+                             uint64_t val) const {
+  // The local-dynamic code sequence for a global `x`:
+  //
+  // Instruction                      Relocation                Symbol
+  // ear %rX,%a0
+  // sllg %rX,%rX,32
+  // ear %rX,%a1
+  // larl %r12,_GLOBAL_OFFSET_TABLE_  R_390_GOTPCDBL            _GLOBAL_OFFSET_TABLE_
+  // lgrl %r2,.LC0                    R_390_PC32DBL             .LC0
+  // brasl %r14,__tls_get_offset at plt  R_390_TLS_LDCALL          <sym>
+  //            :tls_ldcall:<sym>     R_390_PLT32DBL            __tls_get_offset
+  // la %r2,0(%r2,%rX)
+  // lgrl %rY,.LC1                    R_390_PC32DBL             .LC1
+  // la %r2,0(%r2,%rY)
+  //
+  // .LC0:
+  // .quad   <sym>@tlsldm             R_390_TLS_LDM64           <sym>
+  // .LC1:
+  // .quad   x at dtpoff                 R_390_TLS_LDO64           x
+  //
+  // Relaxing to local-exec entails:
+  // 1) Replacing the call by a nop.
+  // 2) Replacing the constant LC0 by 0 (i.e. ignoring the relocation).
+  // 3) Replacing the relocation on the constant LC1 by R_390_TLS_LE64.
+
+  switch (rel.type) {
+  case R_390_TLS_LDCALL:
+    /* brasl %r14,__tls_get_offset at plt -> brcl 0,. */
+    write16be(loc, 0xc004);
+    write16be(loc + 2, 0x0000);
+    write16be(loc + 4, 0x0000);
+    break;
+  case R_390_TLS_LDM64:
+    break;
+  case R_390_TLS_LDO64:
+    relocateNoSym(loc, R_390_TLS_LE64, val);
+    break;
+  default:
+    llvm_unreachable("unsupported relocation for TLS LD to LE relaxation");
+  }
+}
+
+RelExpr SystemZ::adjustGotPcExpr(RelType type, int64_t addend,
+                                 const uint8_t *loc) const {
+  // Only R_390_GOTENT with addend 2 can be relaxed.
+  if (!config->relax || addend != 2 || type != R_390_GOTENT)
+    return R_GOT_PC;
+  const uint16_t op = read16be(loc - 2);
+
+  // lgrl rx,sym at GOTENT -> larl rx, sym
+  // This relaxation is legal if "sym" binds locally (which was
+  // already verified by our caller) and is in-range and properly
+  // aligned for a LARL instruction.  We cannot verify the latter
+  // constraint here, so we assume it is true and revert the decision
+  // later on in relaxOnce if necessary.
+  if ((op & 0xff0f) == 0xc408)
+    return R_RELAX_GOT_PC;
+
+  return R_GOT_PC;
+}
+
+bool SystemZ::relaxOnce(int pass) const {
+  // If we decided in adjustGotPcExpr to relax a R_390_GOTENT,
+  // we need to validate the target symbol is in-range and aligned.
+  SmallVector<InputSection *, 0> storage;
+  bool changed = false;
+  for (OutputSection *osec : outputSections) {
+    if (!(osec->flags & SHF_EXECINSTR))
+      continue;
+    for (InputSection *sec : getInputSections(*osec, storage)) {
+      for (Relocation &rel : sec->relocs()) {
+        if (rel.expr != R_RELAX_GOT_PC)
+          continue;
+
+        uint64_t v = sec->getRelocTargetVA(
+            sec->file, rel.type, rel.addend,
+            sec->getOutputSection()->addr + rel.offset, *rel.sym, rel.expr);
+        if (isInt<33>(v) && !(v & 1))
+          continue;
+        if (rel.sym->auxIdx == 0) {
+          rel.sym->allocateAux();
+          addGotEntry(*rel.sym);
+          changed = true;
+        }
+        rel.expr = R_GOT_PC;
+      }
+    }
+  }
+  return changed;
+}
+
+void SystemZ::relaxGot(uint8_t *loc, const Relocation &rel,
+                       uint64_t val) const {
+  assert(isInt<33>(val) &&
+         "R_390_GOTENT should not have been relaxed if it overflows");
+  assert(!(val & 1) &&
+         "R_390_GOTENT should not have been relaxed if it is misaligned");
+  const uint16_t op = read16be(loc - 2);
+
+  // lgrl rx,sym at GOTENT -> larl rx, sym
+  if ((op & 0xff0f) == 0xc408) {
+    write16be(loc - 2, 0xc000 | (op & 0x00f0));
+    write32be(loc, val >> 1);
+    return;
+  }
+}
+
+void SystemZ::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
+  switch (rel.expr) {
+  case R_RELAX_GOT_PC:
+    return relaxGot(loc, rel, val);
+  case R_RELAX_TLS_GD_TO_IE_GOT_OFF:
+    return relaxTlsGdToIe(loc, rel, val);
+  case R_RELAX_TLS_GD_TO_LE:
+    return relaxTlsGdToLe(loc, rel, val);
+  case R_RELAX_TLS_LD_TO_LE:
+    return relaxTlsLdToLe(loc, rel, val);
+  default:
+    break;
+  }
+  switch (rel.type) {
+  case R_390_8:
+    checkIntUInt(loc, val, 8, rel);
+    *loc = val;
+    break;
+  case R_390_12:
+  case R_390_GOT12:
+  case R_390_GOTPLT12:
+  case R_390_TLS_GOTIE12:
+    checkUInt(loc, val, 12, rel);
+    write16be(loc, (read16be(loc) & 0xF000) | val);
+    break;
+  case R_390_PC12DBL:
+  case R_390_PLT12DBL:
+    checkInt(loc, val, 13, rel);
+    checkAlignment(loc, val, 2, rel);
+    write16be(loc, (read16be(loc) & 0xF000) | (val >> 1));
+    break;
+  case R_390_16:
+  case R_390_GOT16:
+  case R_390_GOTPLT16:
+  case R_390_GOTOFF16:
+  case R_390_PLTOFF16:
+    checkIntUInt(loc, val, 16, rel);
+    write16be(loc, val);
+    break;
+  case R_390_PC16:
+    checkInt(loc, val, 16, rel);
+    write16be(loc, val);
+    break;
+  case R_390_PC16DBL:
+  case R_390_PLT16DBL:
+    checkInt(loc, val, 17, rel);
+    checkAlignment(loc, val, 2, rel);
+    write16be(loc, val >> 1);
+    break;
+  case R_390_20:
+  case R_390_GOT20:
+  case R_390_GOTPLT20:
+  case R_390_TLS_GOTIE20:
+    checkInt(loc, val, 20, rel);
+    write32be(loc, (read32be(loc) & 0xF00000FF)
+		   | ((val & 0xFFF) << 16) | ((val & 0xFF000) >> 4));
+    break;
+  case R_390_PC24DBL:
+  case R_390_PLT24DBL:
+    checkInt(loc, val, 25, rel);
+    loc[0] = val >> 17;
+    loc[1] = val >> 9;
+    loc[2] = val >> 1;
+    break;
+  case R_390_32:
+  case R_390_GOT32:
+  case R_390_GOTPLT32:
+  case R_390_GOTOFF:
+  case R_390_PLTOFF32:
+  case R_390_TLS_IE32:
+  case R_390_TLS_GOTIE32:
+  case R_390_TLS_GD32:
+  case R_390_TLS_LDM32:
+  case R_390_TLS_LDO32:
+  case R_390_TLS_LE32:
+    checkIntUInt(loc, val, 32, rel);
+    write32be(loc, val);
+    break;
+  case R_390_PC32:
+  case R_390_PLT32:
+    checkInt(loc, val, 32, rel);
+    write32be(loc, val);
+    break;
+  case R_390_PC32DBL:
+  case R_390_PLT32DBL:
+  case R_390_GOTPCDBL:
+  case R_390_GOTENT:
+  case R_390_GOTPLTENT:
+  case R_390_TLS_IEENT:
+    checkInt(loc, val, 33, rel);
+    checkAlignment(loc, val, 2, rel);
+    write32be(loc, val >> 1);
+    break;
+  case R_390_64:
+  case R_390_PC64:
+  case R_390_PLT64:
+  case R_390_GOT64:
+  case R_390_GOTPLT64:
+  case R_390_GOTOFF64:
+  case R_390_PLTOFF64:
+  case R_390_GOTPC:
+  case R_390_TLS_IE64:
+  case R_390_TLS_GOTIE64:
+  case R_390_TLS_GD64:
+  case R_390_TLS_LDM64:
+  case R_390_TLS_LDO64:
+  case R_390_TLS_LE64:
+  case R_390_TLS_DTPMOD:
+  case R_390_TLS_DTPOFF:
+  case R_390_TLS_TPOFF:
+    write64be(loc, val);
+    break;
+  case R_390_TLS_LOAD:
+  case R_390_TLS_GDCALL:
+  case R_390_TLS_LDCALL:
+    break;
+  default:
+    error(getErrorLocation(loc) + "unknown relocation (" + Twine(rel.type) + ")");
+    llvm_unreachable("unknown relocation");
+  }
+}
+
+static TargetInfo *getTargetInfo() {
----------------
MaskRay wrote:

inline this trivial function

https://github.com/llvm/llvm-project/pull/75643


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