[lld][ELF] Add basic TLSDESC support for LoongArch

LoongArch does not yet implement transition from TLSDESC to LE/IE,
so TLSDESC dynamic relocation needs to be generated for each desc,
which is ultimately handled by the dynamic linker.

The test cases reference RISC-V: #79239

Reviewed By: MaskRay, SixWeining

Pull Request: https://github.com/llvm/llvm-project/pull/94451

4 files changed, 55 insertions, 0 deletions

diff --git a/lld/ELF/Arch/LoongArch.cpp b/lld/ELF/Arch/LoongArch.cpp
index 2c5d5df..c6ee73f 100644
--- a/lld/ELF/Arch/LoongArch.cpp
+++ b/lld/ELF/Arch/LoongArch.cpp
@@ -98,11 +98,13 @@ uint64_t elf::getLoongArchPageDelta(uint64_t dest, uint64_t pc, RelType type) {
   case R_LARCH_PCALA64_LO20:
   case R_LARCH_GOT64_PC_LO20:
   case R_LARCH_TLS_IE64_PC_LO20:
+  case R_LARCH_TLS_DESC64_PC_LO20:
     pcalau12i_pc = pc - 8;
     break;
   case R_LARCH_PCALA64_HI12:
   case R_LARCH_GOT64_PC_HI12:
   case R_LARCH_TLS_IE64_PC_HI12:
+  case R_LARCH_TLS_DESC64_PC_HI12:
     pcalau12i_pc = pc - 12;
     break;
   default:
@@ -190,11 +192,13 @@ LoongArch::LoongArch() {
     tlsModuleIndexRel = R_LARCH_TLS_DTPMOD64;
     tlsOffsetRel = R_LARCH_TLS_DTPREL64;
     tlsGotRel = R_LARCH_TLS_TPREL64;
+    tlsDescRel = R_LARCH_TLS_DESC64;
   } else {
     symbolicRel = R_LARCH_32;
     tlsModuleIndexRel = R_LARCH_TLS_DTPMOD32;
     tlsOffsetRel = R_LARCH_TLS_DTPREL32;
     tlsGotRel = R_LARCH_TLS_TPREL32;
+    tlsDescRel = R_LARCH_TLS_DESC32;
   }
 
   gotRel = symbolicRel;
@@ -294,6 +298,10 @@ int64_t LoongArch::getImplicitAddend(const uint8_t *buf, RelType type) const {
   case R_LARCH_JUMP_SLOT:
     // These relocations are defined as not having an implicit addend.
     return 0;
+  case R_LARCH_TLS_DESC32:
+    return read32le(buf + 4);
+  case R_LARCH_TLS_DESC64:
+    return read64le(buf + 8);
   }
 }
 
@@ -486,6 +494,19 @@ RelExpr LoongArch::getRelExpr(const RelType type, const Symbol &s,
     return config->relax ? R_RELAX_HINT : R_NONE;
   case R_LARCH_ALIGN:
     return R_RELAX_HINT;
+  case R_LARCH_TLS_DESC_PC_HI20:
+  case R_LARCH_TLS_DESC64_PC_LO20:
+  case R_LARCH_TLS_DESC64_PC_HI12:
+    return R_LOONGARCH_TLSDESC_PAGE_PC;
+  case R_LARCH_TLS_DESC_PC_LO12:
+  case R_LARCH_TLS_DESC_LD:
+  case R_LARCH_TLS_DESC_HI20:
+  case R_LARCH_TLS_DESC_LO12:
+  case R_LARCH_TLS_DESC64_LO20:
+  case R_LARCH_TLS_DESC64_HI12:
+    return R_TLSDESC;
+  case R_LARCH_TLS_DESC_CALL:
+    return R_TLSDESC_CALL;
 
   // Other known relocs that are explicitly unimplemented:
   //
@@ -510,6 +531,8 @@ bool LoongArch::usesOnlyLowPageBits(RelType type) const {
   case R_LARCH_GOT_LO12:
   case R_LARCH_GOT_PC_LO12:
   case R_LARCH_TLS_IE_PC_LO12:
+  case R_LARCH_TLS_DESC_LO12:
+  case R_LARCH_TLS_DESC_PC_LO12:
     return true;
   }
 }
@@ -594,6 +617,8 @@ void LoongArch::relocate(uint8_t *loc, const Relocation &rel,
   case R_LARCH_TLS_LE_LO12:
   case R_LARCH_TLS_IE_PC_LO12:
   case R_LARCH_TLS_IE_LO12:
+  case R_LARCH_TLS_DESC_PC_LO12:
+  case R_LARCH_TLS_DESC_LO12:
     write32le(loc, setK12(read32le(loc), extractBits(val, 11, 0)));
     return;
 
@@ -609,6 +634,8 @@ void LoongArch::relocate(uint8_t *loc, const Relocation &rel,
   case R_LARCH_TLS_LD_HI20:
   case R_LARCH_TLS_GD_PC_HI20:
   case R_LARCH_TLS_GD_HI20:
+  case R_LARCH_TLS_DESC_PC_HI20:
+  case R_LARCH_TLS_DESC_HI20:
     write32le(loc, setJ20(read32le(loc), extractBits(val, 31, 12)));
     return;
 
@@ -620,6 +647,8 @@ void LoongArch::relocate(uint8_t *loc, const Relocation &rel,
   case R_LARCH_TLS_LE64_LO20:
   case R_LARCH_TLS_IE64_PC_LO20:
   case R_LARCH_TLS_IE64_LO20:
+  case R_LARCH_TLS_DESC64_PC_LO20:
+  case R_LARCH_TLS_DESC64_LO20:
     write32le(loc, setJ20(read32le(loc), extractBits(val, 51, 32)));
     return;
 
@@ -631,6 +660,8 @@ void LoongArch::relocate(uint8_t *loc, const Relocation &rel,
   case R_LARCH_TLS_LE64_HI12:
   case R_LARCH_TLS_IE64_PC_HI12:
   case R_LARCH_TLS_IE64_HI12:
+  case R_LARCH_TLS_DESC64_PC_HI12:
+  case R_LARCH_TLS_DESC64_HI12:
     write32le(loc, setK12(read32le(loc), extractBits(val, 63, 52)));
     return;
 
@@ -679,6 +710,15 @@ void LoongArch::relocate(uint8_t *loc, const Relocation &rel,
   case R_LARCH_RELAX:
     return; // Ignored (for now)
 
+  case R_LARCH_TLS_DESC_LD:
+    return; // nothing to do.
+  case R_LARCH_TLS_DESC32:
+    write32le(loc + 4, val);
+    return;
+  case R_LARCH_TLS_DESC64:
+    write64le(loc + 8, val);
+    return;
+
   default:
     llvm_unreachable("unknown relocation");
   }
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index f4287bc..be12218 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -877,6 +877,8 @@ uint64_t InputSectionBase::getRelocTargetVA(const InputFile *file, RelType type,
     return in.got->getTlsDescAddr(sym) + a - in.gotPlt->getVA();
   case R_AARCH64_TLSDESC_PAGE:
     return getAArch64Page(in.got->getTlsDescAddr(sym) + a) - getAArch64Page(p);
+  case R_LOONGARCH_TLSDESC_PAGE_PC:
+    return getLoongArchPageDelta(in.got->getTlsDescAddr(sym) + a, p, type);
   case R_TLSGD_GOT:
     return in.got->getGlobalDynOffset(sym) + a;
   case R_TLSGD_GOTPLT:
diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
index 04db413..1b08339 100644
--- a/lld/ELF/Relocations.cpp
+++ b/lld/ELF/Relocations.cpp
@@ -1297,6 +1297,18 @@ static unsigned handleTlsRelocation(RelType type, Symbol &sym,
 
   if (config->emachine == EM_MIPS)
     return handleMipsTlsRelocation(type, sym, c, offset, addend, expr);
+
+  // LoongArch does not yet implement transition from TLSDESC to LE/IE, so
+  // generate TLSDESC dynamic relocation for the dynamic linker to handle.
+  if (config->emachine == EM_LOONGARCH &&
+      oneof<R_LOONGARCH_TLSDESC_PAGE_PC, R_TLSDESC, R_TLSDESC_CALL>(expr)) {
+    if (expr != R_TLSDESC_CALL) {
+      sym.setFlags(NEEDS_TLSDESC);
+      c.addReloc({expr, type, offset, addend, &sym});
+    }
+    return 1;
+  }
+
   bool isRISCV = config->emachine == EM_RISCV;
 
   if (oneof<R_AARCH64_TLSDESC_PAGE, R_TLSDESC, R_TLSDESC_CALL, R_TLSDESC_PC,
diff --git a/lld/ELF/Relocations.h b/lld/ELF/Relocations.h
index b7b9c09..e299d23 100644
--- a/lld/ELF/Relocations.h
+++ b/lld/ELF/Relocations.h
@@ -116,6 +116,7 @@ enum RelExpr {
   R_LOONGARCH_GOT,
   R_LOONGARCH_GOT_PAGE_PC,
   R_LOONGARCH_TLSGD_PAGE_PC,
+  R_LOONGARCH_TLSDESC_PAGE_PC,
 };
 
 // Architecture-neutral representation of relocation.