arch-loongarch.cc

// LoongArch is a new RISC ISA announced in 2021 by Loongson. The ISA
// feels like a modernized MIPS with a hint of RISC-V flavor, although
// it's not compatible with either one.
//
// While LoongArch is a fresh and clean ISA, its technological advantage
// over other modern RISC ISAs such as RISC-V doesn't seem to be very
// significant. It appears that the real selling point of LoongArch is
// that the ISA is developed and controlled by a Chinese company,
// reflecting a desire for domestic CPUs. Loongson is actively working on
// bootstrapping the entire ecosystem for LoongArch, sending patches to
// Linux, GCC, LLVM, etc.
//
// All instructions are 4 bytes long in LoongArch and aligned to 4-byte
// boundaries. It has 32 general-purpose registers. Among these, $t0 - $t8
// (aliases for $r12 - $r20) are temporary registers that we can use in
// our PLT and range extension thunks.
//
// The psABI defines a few linker relaxations. We haven't supported them
// yet.
//
// https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html

#if MOLD_LOONGARCH64 || MOLD_LOONGARCH32

#include "mold.h"

namespace mold::elf {

using E = MOLD_TARGET;

static u64 page(u64 val) {
  return val & 0xffff'ffff'ffff'f000;
}

static u64 hi20(u64 val, u64 pc) {
  // A PC-relative address with a 32 bit offset is materialized in a
  // register with the following instructions:
  //
  //   pcalau12i $rN, %pc_hi20(sym)
  //   addi.d    $rN, $rN, %lo12(sym)
  //
  // PCALAU12I materializes bits [63:12] by computing (pc + imm << 12)
  // and zero-clear [11:0]. ADDI.D sign-extends its 12 bit immediate and
  // add it to the register. To compensate the sign-extension, PCALAU12I
  // needs to materialize a 0x1000 larger value than the desired [63:12]
  // if [11:0] is sign-extended.
  //
  // This is similar but different from RISC-V because RISC-V's AUIPC
  // doesn't zero-clear [11:0].
  return bits(page(val + 0x800) - page(pc), 31, 12);
}

static u64 hi64(u64 val, u64 pc) {
  // A PC-relative 64-bit address is materialized with the following
  // instructions for the large code model:
  //
  //   pcalau12i $rN, %pc_hi20(sym)
  //   addi.d    $rM, $zero, %lo12(sym)
  //   lu32i.d   $rM, %pc64_lo20(sym)
  //   lu52i.d   $rM, $r12, %pc64_hi12(sym)
  //   add.d     $rN, $rN, $rM
  //
  // PCALAU12I computes (pc + imm << 12) to materialize a 64-bit value.
  // ADDI.D adds a sign-extended 12 bit value to a register. LU32I.D and
  // LU52I.D simply set bits to [51:31] and to [63:53], respectively.
  //
  // Compensating all the sign-extensions is a bit complicated.
  u64 x = page(val) - page(pc);
  if (val & 0x800)
    x += 0x1000 - 0x1'0000'0000;
  if (x & 0x8000'0000)
    x += 0x1'0000'0000;
  return x;
}

static u64 higher20(u64 val, u64 pc) {
  return bits(hi64(val, pc), 51, 32);
}

static u64 highest12(u64 val, u64 pc) {
  return bits(hi64(val, pc), 63, 52);
}

static void write_k12(u8 *loc, u32 val) {
  // opcode, [11:0], rj, rd
  *(ul32 *)loc &= 0b1111111111'000000000000'11111'11111;
  *(ul32 *)loc |= bits(val, 11, 0) << 10;
}

static void write_k16(u8 *loc, u32 val) {
  // opcode, [15:0], rj, rd
  *(ul32 *)loc &= 0b111111'0000000000000000'11111'11111;
  *(ul32 *)loc |= bits(val, 15, 0) << 10;
}

static void write_j20(u8 *loc, u32 val) {
  // opcode, [19:0], rd
  *(ul32 *)loc &= 0b1111111'00000000000000000000'11111;
  *(ul32 *)loc |= bits(val, 19, 0) << 5;
}

static void write_d5k16(u8 *loc, u32 val) {
  // opcode, [15:0], rj, [20:16]
  *(ul32 *)loc &= 0b111111'0000000000000000'11111'00000;
  *(ul32 *)loc |= bits(val, 15, 0) << 10;
  *(ul32 *)loc |= bits(val, 20, 16);
}

static void write_d10k16(u8 *loc, u32 val) {
  // opcode, [15:0], [25:16]
  *(ul32 *)loc &= 0b111111'0000000000000000'0000000000;
  *(ul32 *)loc |= bits(val, 15, 0) << 10;
  *(ul32 *)loc |= bits(val, 25, 16);
}

template <>
void write_plt_header<E>(Context<E> &ctx, u8 *buf) {
  static const ul32 insn_64[] = {
    0x1a00'000e, // pcalau12i $t2, %pc_hi20(.got.plt)
    0x0011'bdad, // sub.d     $t1, $t1, $t3
    0x28c0'01cf, // ld.d      $t3, $t2, %lo12(.got.plt) # _dl_runtime_resolve
    0x02ff'51ad, // addi.d    $t1, $t1, -44             # .plt entry
    0x02c0'01cc, // addi.d    $t0, $t2, %lo12(.got.plt) # &.got.plt
    0x0045'05ad, // srli.d    $t1, $t1, 1               # .plt entry offset
    0x28c0'218c, // ld.d      $t0, $t0, 8               # link map
    0x4c00'01e0, // jr        $t3
  };

  static const ul32 insn_32[] = {
    0x1a00'000e, // pcalau12i $t2, %pc_hi20(.got.plt)
    0x0011'3dad, // sub.w     $t1, $t1, $t3
    0x2880'01cf, // ld.w      $t3, $t2, %lo12(.got.plt) # _dl_runtime_resolve
    0x02bf'51ad, // addi.w    $t1, $t1, -44             # .plt entry
    0x0280'01cc, // addi.w    $t0, $t2, %lo12(.got.plt) # &.got.plt
    0x0044'89ad, // srli.w    $t1, $t1, 2               # .plt entry offset
    0x2880'118c, // ld.w      $t0, $t0, 4               # link map
    0x4c00'01e0, // jr        $t3
  };

  u64 gotplt = ctx.gotplt->shdr.sh_addr;
  u64 plt = ctx.plt->shdr.sh_addr;

  memcpy(buf, E::is_64 ? insn_64 : insn_32, E::plt_hdr_size);
  write_j20(buf, hi20(gotplt, plt));
  write_k12(buf + 8, gotplt);
  write_k12(buf + 16, gotplt);
}

static const ul32 plt_entry_64[] = {
  0x1a00'000f, // pcalau12i $t3, %pc_hi20(func@.got.plt)
  0x28c0'01ef, // ld.d      $t3, $t3, %lo12(func@.got.plt)
  0x4c00'01ed, // jirl      $t1, $t3, 0
  0x0340'0000, // nop
};

static const ul32 plt_entry_32[] = {
  0x1a00'000f, // pcalau12i $t3, %pc_hi20(func@.got.plt)
  0x2880'01ef, // ld.w      $t3, $t3, %lo12(func@.got.plt)
  0x4c00'01ed, // jirl      $t1, $t3, 0
  0x0340'0000, // nop
};

template <>
void write_plt_entry<E>(Context<E> &ctx, u8 *buf, Symbol<E> &sym) {
  u64 gotplt = sym.get_gotplt_addr(ctx);
  u64 plt = sym.get_plt_addr(ctx);

  memcpy(buf, E::is_64 ? plt_entry_64 : plt_entry_32, E::plt_size);
  write_j20(buf, hi20(gotplt, plt));
  write_k12(buf + 4, gotplt);
}

template <>
void write_pltgot_entry<E>(Context<E> &ctx, u8 *buf, Symbol<E> &sym) {
  u64 got = sym.get_got_pltgot_addr(ctx);
  u64 plt = sym.get_plt_addr(ctx);

  memcpy(buf, E::is_64 ? plt_entry_64 : plt_entry_32, E::plt_size);
  write_j20(buf, hi20(got, plt));
  write_k12(buf + 4, got);
}

template <>
void EhFrameSection<E>::apply_eh_reloc(Context<E> &ctx, const ElfRel<E> &rel,
                                       u64 offset, u64 val) {
  u8 *loc = ctx.buf + this->shdr.sh_offset + offset;

  switch (rel.r_type) {
  case R_NONE:
    break;
  case R_LARCH_ADD6:
    *loc = (*loc & 0b1100'0000) | ((*loc + val) & 0b0011'1111);
    break;
  case R_LARCH_ADD8:
    *loc += val;
    break;
  case R_LARCH_ADD16:
    *(ul16 *)loc += val;
    break;
  case R_LARCH_ADD32:
    *(ul32 *)loc += val;
    break;
  case R_LARCH_ADD64:
    *(ul64 *)loc += val;
    break;
  case R_LARCH_SUB6:
    *loc = (*loc & 0b1100'0000) | ((*loc - val) & 0b0011'1111);
    break;
  case R_LARCH_SUB8:
    *loc -= val;
    break;
  case R_LARCH_SUB16:
    *(ul16 *)loc -= val;
    break;
  case R_LARCH_SUB32:
    *(ul32 *)loc -= val;
    break;
  case R_LARCH_SUB64:
    *(ul64 *)loc -= val;
    break;
  case R_LARCH_32_PCREL:
    *(ul32 *)loc = val - this->shdr.sh_addr - offset;
    break;
  case R_LARCH_64_PCREL:
    *(ul64 *)loc = val - this->shdr.sh_addr - offset;
    break;
  default:
    Fatal(ctx) << "unsupported relocation in .eh_frame: " << rel;
  }
}

template <>
void InputSection<E>::apply_reloc_alloc(Context<E> &ctx, u8 *base) {
  std::span<const ElfRel<E>> rels = get_rels(ctx);

  ElfRel<E> *dynrel = nullptr;
  if (ctx.reldyn)
    dynrel = (ElfRel<E> *)(ctx.buf + ctx.reldyn->shdr.sh_offset +
                           file.reldyn_offset + this->reldyn_offset);

  for (i64 i = 0; i < rels.size(); i++) {
    const ElfRel<E> &rel = rels[i];

    if (rel.r_type == R_NONE || rel.r_type == R_LARCH_RELAX ||
        rel.r_type == R_LARCH_MARK_LA || rel.r_type == R_LARCH_MARK_PCREL ||
        rel.r_type == R_LARCH_ALIGN)
      continue;

    Symbol<E> &sym = *file.symbols[rel.r_sym];
    u8 *loc = base + rel.r_offset;

    auto check = [&](i64 val, i64 lo, i64 hi) {
      if (val < lo || hi <= val)
        Error(ctx) << *this << ": relocation " << rel << " against "
                   << sym << " out of range: " << val << " is not in ["
                   << lo << ", " << hi << ")";
    };

    auto check_branch = [&](i64 val, i64 lo, i64 hi) {
      if (val & 0b11)
        Error(ctx) << *this << ": misaligned symbol " << sym
                   << " for relocation " << rel;
      check(val, lo, hi);
    };

    // Unlike other psABIs, the LoongArch ABI uses the same relocation
    // types to refer to GOT entries for thread-local symbols and regular
    // ones. Therefore, G may refer to a TLSGD or a regular GOT slot
    // depending on the symbol type.
    //
    // Note that as of August 2023, both GCC and Clang treat TLSLD relocs
    // as if they were TLSGD relocs for LoongArch, which is a clear bug.
    // We need to handle TLSLD relocs as synonyms for TLSGD relocs for the
    // sake of bug compatibility.
    auto get_got_idx = [&] {
      if (sym.has_tlsgd(ctx))
        return sym.get_tlsgd_idx(ctx);
      return sym.get_got_idx(ctx);
    };

    u64 S = sym.get_addr(ctx);
    u64 A = rel.r_addend;
    u64 P = get_addr() + rel.r_offset;
    u64 G = get_got_idx() * sizeof(Word<E>);
    u64 GOT = ctx.got->shdr.sh_addr;

    switch (rel.r_type) {
    case R_LARCH_32:
      if constexpr (E::is_64)
        *(ul32 *)loc = S + A;
      else
        apply_dyn_absrel(ctx, sym, rel, loc, S, A, P, &dynrel);
      break;
    case R_LARCH_64:
      assert(E::is_64);
      apply_dyn_absrel(ctx, sym, rel, loc, S, A, P, &dynrel);
      break;
    case R_LARCH_B16:
      check_branch(S + A - P, -(1 << 17), 1 << 17);
      write_k16(loc, (S + A - P) >> 2);
      break;
    case R_LARCH_B21:
      check_branch(S + A - P, -(1 << 22), 1 << 22);
      write_d5k16(loc, (S + A - P) >> 2);
      break;
    case R_LARCH_B26: {
      i64 val = S + A - P;
      if (val < -(1 << 27) || (1 << 27) <= val)
        val = get_thunk_addr(i) + A - P;
      write_d10k16(loc, val >> 2);
      break;
    }
    case R_LARCH_ABS_LO12:
      write_k12(loc, S + A);
      break;
    case R_LARCH_ABS_HI20:
      write_j20(loc, (S + A) >> 12);
      break;
    case R_LARCH_ABS64_LO20:
      write_j20(loc, (S + A) >> 32);
      break;
    case R_LARCH_ABS64_HI12:
      write_k12(loc, (S + A) >> 52);
      break;
    case R_LARCH_PCALA_LO12:
      // It looks like R_LARCH_PCALA_LO12 is sometimes used for JIRL even
      // though the instruction takes a 16 bit immediate rather than 12 bits.
      // It is contrary to the psABI document, but GNU ld has special
      // code to handle it, so we accept it too.
      if ((*(ul32 *)loc & 0xfc00'0000) == 0x4c00'0000)
        write_k16(loc, sign_extend(S + A, 11) >> 2);
      else
        write_k12(loc, S + A);
      break;
    case R_LARCH_PCALA_HI20:
      write_j20(loc, hi20(S + A, P));
      break;
    case R_LARCH_PCALA64_LO20:
      write_j20(loc, higher20(S + A, P));
      break;
    case R_LARCH_PCALA64_HI12:
      write_k12(loc, highest12(S + A, P));
      break;
    case R_LARCH_GOT_PC_LO12:
      write_k12(loc, GOT + G + A);
      break;
    case R_LARCH_GOT_PC_HI20:
      write_j20(loc, hi20(GOT + G + A, P));
      break;
    case R_LARCH_GOT64_PC_LO20:
      write_j20(loc, higher20(GOT + G + A, P));
      break;
    case R_LARCH_GOT64_PC_HI12:
      write_k12(loc, highest12(GOT + G + A, P));
      break;
    case R_LARCH_GOT_LO12:
      write_k12(loc, GOT + G + A);
      break;
    case R_LARCH_GOT_HI20:
      write_j20(loc, (GOT + G + A) >> 12);
      break;
    case R_LARCH_GOT64_LO20:
      write_j20(loc, (GOT + G + A) >> 32);
      break;
    case R_LARCH_GOT64_HI12:
      write_k12(loc, (GOT + G + A) >> 52);
      break;
    case R_LARCH_TLS_LE_LO12:
      write_k12(loc, S + A - ctx.tp_addr);
      break;
    case R_LARCH_TLS_LE_HI20:
      write_j20(loc, (S + A - ctx.tp_addr) >> 12);
      break;
    case R_LARCH_TLS_LE64_LO20:
      write_j20(loc, (S + A - ctx.tp_addr) >> 32);
      break;
    case R_LARCH_TLS_LE64_HI12:
      write_k12(loc, (S + A - ctx.tp_addr) >> 52);
      break;
    case R_LARCH_TLS_IE_PC_LO12:
      write_k12(loc, sym.get_gottp_addr(ctx) + A);
      break;
    case R_LARCH_TLS_IE_PC_HI20:
      write_j20(loc, hi20(sym.get_gottp_addr(ctx) + A, P));
      break;
    case R_LARCH_TLS_IE64_PC_LO20:
      write_j20(loc, higher20(sym.get_gottp_addr(ctx) + A, P));
      break;
    case R_LARCH_TLS_IE64_PC_HI12:
      write_k12(loc, highest12(sym.get_gottp_addr(ctx) + A, P));
      break;
    case R_LARCH_TLS_IE_LO12:
      write_k12(loc, sym.get_gottp_addr(ctx) + A);
      break;
    case R_LARCH_TLS_IE_HI20:
      write_j20(loc, (sym.get_gottp_addr(ctx) + A) >> 12);
      break;
    case R_LARCH_TLS_IE64_LO20:
      write_j20(loc, (sym.get_gottp_addr(ctx) + A) >> 32);
      break;
    case R_LARCH_TLS_IE64_HI12:
      write_k12(loc, (sym.get_gottp_addr(ctx) + A) >> 52);
      break;
    case R_LARCH_TLS_LD_PC_HI20:
    case R_LARCH_TLS_GD_PC_HI20:
      check(sym.get_tlsgd_addr(ctx) + A - P, -(1LL << 31), 1LL << 31);
      write_j20(loc, hi20(sym.get_tlsgd_addr(ctx) + A, P));
      break;
    case R_LARCH_TLS_LD_HI20:
    case R_LARCH_TLS_GD_HI20:
      write_j20(loc, (sym.get_tlsgd_addr(ctx) + A) >> 12);
      break;
    case R_LARCH_ADD6:
      *loc = (*loc & 0b1100'0000) | ((*loc + S + A) & 0b0011'1111);
      break;
    case R_LARCH_ADD8:
      *loc += S + A;
      break;
    case R_LARCH_ADD16:
      *(ul16 *)loc += S + A;
      break;
    case R_LARCH_ADD32:
      *(ul32 *)loc += S + A;
      break;
    case R_LARCH_ADD64:
      *(ul64 *)loc += S + A;
      break;
    case R_LARCH_SUB6:
      *loc = (*loc & 0b1100'0000) | ((*loc - S - A) & 0b0011'1111);
      break;
    case R_LARCH_SUB8:
      *loc -= S + A;
      break;
    case R_LARCH_SUB16:
      *(ul16 *)loc -= S + A;
      break;
    case R_LARCH_SUB32:
      *(ul32 *)loc -= S + A;
      break;
    case R_LARCH_SUB64:
      *(ul64 *)loc -= S + A;
      break;
    case R_LARCH_32_PCREL:
      *(ul32 *)loc = S + A - P;
      break;
    case R_LARCH_64_PCREL:
      *(ul64 *)loc = S + A - P;
      break;
    case R_LARCH_ADD_ULEB128:
      overwrite_uleb(loc, read_uleb(loc) + S + A);
      break;
    case R_LARCH_SUB_ULEB128:
      overwrite_uleb(loc, read_uleb(loc) - S - A);
      break;
    default:
      unreachable();
    }
  }
}

template <>
void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
  std::span<const ElfRel<E>> rels = get_rels(ctx);

  for (i64 i = 0; i < rels.size(); i++) {
    const ElfRel<E> &rel = rels[i];
    if (rel.r_type == R_NONE)
      continue;

    Symbol<E> &sym = *file.symbols[rel.r_sym];
    u8 *loc = base + rel.r_offset;

    if (!sym.file) {
      record_undef_error(ctx, rel);
      continue;
    }

    SectionFragment<E> *frag;
    i64 frag_addend;
    std::tie(frag, frag_addend) = get_fragment(ctx, rel);

    u64 S = frag ? frag->get_addr(ctx) : sym.get_addr(ctx);
    u64 A = frag ? frag_addend : (i64)rel.r_addend;

    switch (rel.r_type) {
    case R_LARCH_32:
      *(ul32 *)loc = S + A;
      break;
    case R_LARCH_64:
      if (std::optional<u64> val = get_tombstone(sym, frag))
        *(ul64 *)loc = *val;
      else
        *(ul64 *)loc = S + A;
      break;
    case R_LARCH_ADD6:
      *loc = (*loc & 0b1100'0000) | ((*loc + S + A) & 0b0011'1111);
      break;
    case R_LARCH_ADD8:
      *loc += S + A;
      break;
    case R_LARCH_ADD16:
      *(ul16 *)loc += S + A;
      break;
    case R_LARCH_ADD32:
      *(ul32 *)loc += S + A;
      break;
    case R_LARCH_ADD64:
      *(ul64 *)loc += S + A;
      break;
    case R_LARCH_SUB6:
      *loc = (*loc & 0b1100'0000) | ((*loc - S - A) & 0b0011'1111);
      break;
    case R_LARCH_SUB8:
      *loc -= S + A;
      break;
    case R_LARCH_SUB16:
      *(ul16 *)loc -= S + A;
      break;
    case R_LARCH_SUB32:
      *(ul32 *)loc -= S + A;
      break;
    case R_LARCH_SUB64:
      *(ul64 *)loc -= S + A;
      break;
    case R_LARCH_TLS_DTPREL32:
      if (std::optional<u64> val = get_tombstone(sym, frag))
        *(ul32 *)loc = *val;
      else
        *(ul32 *)loc = S + A - ctx.dtp_addr;
      break;
    case R_LARCH_TLS_DTPREL64:
      if (std::optional<u64> val = get_tombstone(sym, frag))
        *(ul64 *)loc = *val;
      else
        *(ul64 *)loc = S + A - ctx.dtp_addr;
      break;
    case R_LARCH_ADD_ULEB128:
      overwrite_uleb(loc, read_uleb(loc) + S + A);
      break;
    case R_LARCH_SUB_ULEB128:
      overwrite_uleb(loc, read_uleb(loc) - S - A);
      break;
    default:
      Fatal(ctx) << *this << ": invalid relocation for non-allocated sections: "
                 << rel;
      break;
    }
  }
}

template <>
void InputSection<E>::scan_relocations(Context<E> &ctx) {
  assert(shdr().sh_flags & SHF_ALLOC);

  this->reldyn_offset = file.num_dynrel * sizeof(ElfRel<E>);
  std::span<const ElfRel<E>> rels = get_rels(ctx);

  // Scan relocations
  for (i64 i = 0; i < rels.size(); i++) {
    const ElfRel<E> &rel = rels[i];

    if (rel.r_type == R_NONE || rel.r_type == R_LARCH_RELAX ||
        rel.r_type == R_LARCH_MARK_LA || rel.r_type == R_LARCH_MARK_PCREL ||
        rel.r_type == R_LARCH_ALIGN)
      continue;

    if (record_undef_error(ctx, rel))
      continue;

    Symbol<E> &sym = *file.symbols[rel.r_sym];

    if (sym.is_ifunc())
      sym.flags |= NEEDS_GOT | NEEDS_PLT;

    switch (rel.r_type) {
    case R_LARCH_32:
      if constexpr (E::is_64)
        scan_absrel(ctx, sym, rel);
      else
        scan_dyn_absrel(ctx, sym, rel);
      break;
    case R_LARCH_64:
      assert(E::is_64);
      scan_dyn_absrel(ctx, sym, rel);
      break;
    case R_LARCH_B26:
    case R_LARCH_PCALA_HI20:
      if (sym.is_imported)
        sym.flags |= NEEDS_PLT;
      break;
    case R_LARCH_GOT_HI20:
    case R_LARCH_GOT_PC_HI20:
      sym.flags |= NEEDS_GOT;
      break;
    case R_LARCH_TLS_IE_HI20:
    case R_LARCH_TLS_IE_PC_HI20:
      sym.flags |= NEEDS_GOTTP;
      break;
    case R_LARCH_TLS_LD_PC_HI20:
    case R_LARCH_TLS_GD_PC_HI20:
    case R_LARCH_TLS_LD_HI20:
    case R_LARCH_TLS_GD_HI20:
      sym.flags |= NEEDS_TLSGD;
      break;
    case R_LARCH_32_PCREL:
    case R_LARCH_64_PCREL:
      scan_pcrel(ctx, sym, rel);
      break;
    case R_LARCH_TLS_LE_HI20:
    case R_LARCH_TLS_LE_LO12:
    case R_LARCH_TLS_LE64_LO20:
    case R_LARCH_TLS_LE64_HI12:
      check_tlsle(ctx, sym, rel);
      break;
    case R_LARCH_B16:
    case R_LARCH_B21:
    case R_LARCH_ABS_HI20:
    case R_LARCH_ABS_LO12:
    case R_LARCH_ABS64_LO20:
    case R_LARCH_ABS64_HI12:
    case R_LARCH_PCALA_LO12:
    case R_LARCH_PCALA64_LO20:
    case R_LARCH_PCALA64_HI12:
    case R_LARCH_GOT_PC_LO12:
    case R_LARCH_GOT64_PC_LO20:
    case R_LARCH_GOT64_PC_HI12:
    case R_LARCH_GOT_LO12:
    case R_LARCH_GOT64_LO20:
    case R_LARCH_GOT64_HI12:
    case R_LARCH_TLS_IE_PC_LO12:
    case R_LARCH_TLS_IE64_PC_LO20:
    case R_LARCH_TLS_IE64_PC_HI12:
    case R_LARCH_TLS_IE_LO12:
    case R_LARCH_TLS_IE64_LO20:
    case R_LARCH_TLS_IE64_HI12:
    case R_LARCH_ADD6:
    case R_LARCH_SUB6:
    case R_LARCH_ADD8:
    case R_LARCH_SUB8:
    case R_LARCH_ADD16:
    case R_LARCH_SUB16:
    case R_LARCH_ADD32:
    case R_LARCH_SUB32:
    case R_LARCH_ADD64:
    case R_LARCH_SUB64:
    case R_LARCH_ADD_ULEB128:
    case R_LARCH_SUB_ULEB128:
      break;
    default:
      Error(ctx) << *this << ": unknown relocation: " << rel;
    }
  }
}

template <>
void Thunk<E>::copy_buf(Context<E> &ctx) {
  static const ul32 insn[] = {
    0x1e00'000c, // pcaddu18i $t0, 0
    0x4c00'0180, // jirl      $zero, $t0, 0
  };

  static_assert(E::thunk_size == sizeof(insn));

  u8 *buf = ctx.buf + output_section.shdr.sh_offset + offset;
  u64 P = output_section.shdr.sh_addr + offset;

  for (Symbol<E> *sym : symbols) {
    u64 S = sym->get_addr(ctx);

    memcpy(buf, insn, sizeof(insn));
    write_j20(buf, (S - P + 0x20000) >> 18);
    write_k16(buf + 4, (S - P) >> 2);

    buf += sizeof(insn);
    P += sizeof(insn);
  }
}

} // namespace mold::elf

#endif