[ELF][X86] Write R_X86_64_TLSDESC addends with -z rel

[MaskRay]

Summary

Similar to D100544 for AArch64.

lld/ELF/Arch/X86_64.cpp

int64_t X86_64::getImplicitAddend(const uint8_t *buf, RelType type) const {
   case R_X86_64_GLOB_DAT:
   case R_X86_64_GOT64:
   case R_X86_64_GOTOFF64:
   case R_X86_64_GOTPC64:
   case R_X86_64_PLTOFF64:
   case R_X86_64_IRELATIVE:
   case R_X86_64_RELATIVE:
     return read64le(buf);
+  case R_X86_64_TLSDESC:
+    return read64le(buf + 8);
   case R_X86_64_JUMP_SLOT:
   case R_X86_64_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;
void X86_64::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
   case R_X86_64_PC64:
   case R_X86_64_SIZE64:
   case R_X86_64_GOT64:
   case R_X86_64_GOTOFF64:
   case R_X86_64_GOTPC64:
   case R_X86_64_PLTOFF64:
     write64le(loc, val);
     break;
+  case R_X86_64_TLSDESC:
+    // The addend is stored in the second 64-bit word.
+    write64le(loc + 8, val);
+    break;
   default:
     llvm_unreachable("unknown relocation");
   }
 }
 
 RelExpr X86_64::adjustGotPcExpr(RelType type, int64_t addend,
                                 const uint8_t *loc) const {
   // Only R_X86_64_[REX_]GOTPCRELX can be relaxed. GNU as may emit GOTPCRELX

lld/test/ELF/x86-64-tlsdesc-gd.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
-# RUN: echo '.tbss; .globl b; b:' | llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
+# RUN: echo '.tbss; .globl c; c: .zero 4' | llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
 # RUN: ld.lld -shared -soname=t1.so %t1.o -o %t1.so
 
 # RUN: ld.lld -shared %t.o %t1.o -o %t.so
-# RUN: llvm-readobj -r %t.so | FileCheck --check-prefix=GD-REL %s
+# RUN: llvm-readobj -r -x .got %t.so | FileCheck --check-prefix=GD-RELA %s
 # RUN: llvm-objdump -d --no-show-raw-insn %t.so | FileCheck --check-prefix=GD %s
 
+# RUN: ld.lld -shared %t.o %t1.o -o %t-rel.so -z rel
+# RUN: llvm-readobj -r -x .got %t-rel.so | FileCheck --check-prefix=GD-REL %s
+
 # RUN: ld.lld %t.o %t1.o -o %t
 # RUN: llvm-readelf -r %t | FileCheck --check-prefix=NOREL %s
 # RUN: llvm-objdump -d --no-show-raw-insn %t | FileCheck --check-prefix=LE %s
 
 # RUN: ld.lld %t.o %t1.so -o %t
 # RUN: llvm-readobj -r %t | FileCheck --check-prefix=IE-REL %s
 # RUN: llvm-objdump -d --no-show-raw-insn %t | FileCheck --check-prefix=IE %s
 
-# GD-REL:      .rela.dyn {
-# GD-REL-NEXT:   0x2380 R_X86_64_TLSDESC a 0x0
-# GD-REL-NEXT:   0x2390 R_X86_64_TLSDESC b 0x0
-# GD-REL-NEXT: }
+# GD-RELA:      .rela.dyn {
+# GD-RELA-NEXT:   0x23B8 R_X86_64_TLSDESC - 0xB
+# GD-RELA-NEXT:   0x23A8 R_X86_64_TLSDESC a 0x0
+# GD-RELA-NEXT:   0x23C8 R_X86_64_TLSDESC c 0x0
+# GD-RELA-NEXT: }
+# GD-RELA:      Hex dump of section '.got':
+# GD-RELA-NEXT: 0x000023a8 00000000 00000000 00000000 00000000
+# GD-RELA-NEXT: 0x000023b8 00000000 00000000 00000000 00000000
+# GD-RELA-NEXT: 0x000023c8 00000000 00000000 00000000 00000000
+
+# GD-REL:       .rel.dyn {
+# GD-REL-NEXT:    0x23A0 R_X86_64_TLSDESC -
+# GD-REL-NEXT:    0x2390 R_X86_64_TLSDESC a
+# GD-REL-NEXT:    0x23B0 R_X86_64_TLSDESC c
+# GD-REL-NEXT:  }
+# GD-REL:       Hex dump of section '.got':
+# GD-REL-NEXT:  0x00002390 00000000 00000000 00000000 00000000
+# GD-REL-NEXT:  0x000023a0 00000000 00000000 0b000000 00000000
+# GD-REL-NEXT:  0x000023b0 00000000 00000000 00000000 00000000
+
+## &.rela.dyn[a]-pc = 0x23A8-0x12e7 = 4289
+# GD:            leaq 4289(%rip), %rax
+# GD-NEXT: 12e7: callq *(%rax)
+# GD-NEXT:       movl %fs:(%rax), %eax
 
-# 0x2380-0x12cf = 4273
-# GD:            leaq 4273(%rip), %rax
-# GD-NEXT: 12cf: callq *(%rax)
+## &.rela.dyn[b]-pc = 0x23B8-0x12f3 = 4293
+# GD-NEXT:       leaq 4293(%rip), %rax
+# GD-NEXT: 12f3: callq *(%rax)
 # GD-NEXT:       movl %fs:(%rax), %eax
 
-# 0x2390-0x12db = 4277
-# GD-NEXT:       leaq 4277(%rip), %rax
-# GD-NEXT: 12db: callq *(%rax)
+## &.rela.dyn[c]-pc = 0x23C8-0x12f3 = 4297
+# GD-NEXT:       leaq 4297(%rip), %rax
+# GD-NEXT: 12ff: callq *(%rax)
 # GD-NEXT:       movl %fs:(%rax), %eax
 
 # NOREL: no relocations
 
-## offset(a) = -4
-# LE:      movq $-4, %rax
+## tpoff(a) = st_value(a) - tls_size = -8
+# LE:      movq $-8, %rax
+# LE-NEXT: nop
+# LE-NEXT: movl %fs:(%rax), %eax
+## tpoff(b) = st_value(b) - tls_size = -5
+# LE:      movq $-5, %rax
 # LE-NEXT: nop
 # LE-NEXT: movl %fs:(%rax), %eax
-## offset(b) = 0
-# LE:      movq $0, %rax
+## tpoff(c) = st_value(c) - tls_size = -4
+# LE:      movq $-4, %rax
 # LE-NEXT: nop
 # LE-NEXT: movl %fs:(%rax), %eax
 
 # IE-REL:      .rela.dyn {
-# IE-REL-NEXT:   0x202360 R_X86_64_TPOFF64 b 0x0
+# IE-REL-NEXT:   0x202370 R_X86_64_TPOFF64 c 0x0
 # IE-REL-NEXT: }
 
 ## a is relaxed to use LE.
 # IE:              movq $-4, %rax
 # IE-NEXT:         nop
 # IE-NEXT:         movl %fs:(%rax), %eax
-## 0x202360 - 0x20129b = 4293
-# IE-NEXT:         movq 4293(%rip), %rax
-# IE-NEXT: 20129b: nop
+# IE-NEXT:         movq $-1, %rax
+# IE-NEXT:         nop
+# IE-NEXT:         movl %fs:(%rax), %eax
+## &.rela.dyn[c]-pc = 0x202370 - 0x2012a7 = 4297
+# IE-NEXT:         movq 4297(%rip), %rax
+# IE-NEXT: 2012a7: nop
 # IE-NEXT:         movl %fs:(%rax), %eax
 
 leaq a@tlsdesc(%rip), %rax
 call *a@tlscall(%rax)
 movl %fs:(%rax), %eax
 
 leaq b@tlsdesc(%rip), %rax
 call *b@tlscall(%rax)
 movl %fs:(%rax), %eax
 
+leaq c@tlsdesc(%rip), %rax
+call *c@tlscall(%rax)
+movl %fs:(%rax), %eax
+
 .section .tbss
 .globl a
 .zero 8
 a:
-.zero 4
+.zero 3
+b:
+.zero 1