feat(asm): emit the riscv64 local-exec TLS sequence

Assisted-by: GLM 5.3

asm/elfriscv.go

@@ -24,6 +24,8 @@ const (
 	rRISCVPCRELHI20  = 23 // R_RISCV_PCREL_HI20
 	rRISCVPCRELLO12I = 24 // R_RISCV_PCREL_LO12_I
 	rRISCVPCRELLO12S = 25 // R_RISCV_PCREL_LO12_S
+	rRISCVTPRELHI20  = 29 // R_RISCV_TPREL_HI20
+	rRISCVTPRELLO12I = 30 // R_RISCV_TPREL_LO12_I
 	// R_RISCV_32 (debug/elf 1): the absolute 32-bit address of a symbol,
 	// the R_ADDR shape a 4-byte DATA field carries.  R_RISCV_64 (2) lives
 	// with the DWARF fixup constants as rRISCVAbs64.
@@ -128,6 +130,15 @@ func (img *Image) ELFRISCVObject() ([]byte, error) {
 				)
 			case RelRISCVJal:
 				relas = append(relas, elfRela{off: uint64(fn.Offset + r.Off), typ: rRISCVJAL, sym: idx, addend: r.Addend})
+			case RelRISCVTLSLE:
+				// The local-exec pair splits into the TPREL HI20 on the LUI
+				// and the TPREL LO12_I on the ADDIW, both against the symbol
+				// (a thread offset, not PC-relative, so the LO12 needs no
+				// label indirection).
+				relas = append(relas,
+					elfRela{off: uint64(fn.Offset + r.Off), typ: rRISCVTPRELHI20, sym: idx, addend: r.Addend},
+					elfRela{off: uint64(fn.Offset + r.Off + 4), typ: rRISCVTPRELLO12I, sym: idx, addend: r.Addend},
+				)
 			default:
 				return nil, fmt.Errorf("relocation kind %v unsupported in ELF emission", r.Kind)
 			}