[ARM][LLD] Initial support for local dynamic TLS for ARM Target

[peter.smith]

Summary

Add support for the local dynamic model ARM TLS relocations:

• R_ARM_TLS_LDM32
• R_ARM_TLS_LDO32

The local dynamic model was not in the inital ARM TLS patch as there was a dependency on llvm-mc (https://reviews.llvm.org/D22461) which has now been closed.

The local dynamic implementation and tests follows the same model as the other ARM TLS models. The R_ARM_TLS_LDO32 is implemented as R_ABS expr type as the getVA() for a TLS symbol will return the offset from the start of the TLS block.

References:
TLS model: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0045e/IHI0045E_ABI_addenda.pdf
Relocations: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044f/IHI0044F_aaelf.pdf

[ruiu]

LGTM

[peter.smith]

Thank you for the quick review. Committed as r276123.

[Eugene.Zelenko]

Looks like commit was not detected by Differential.

[emaste]

Looks like commit was not detected by Differential.

Seems the : was missing after Differential Revision in rL276123

ELF/Target.cpp

 };
 
 class ARMTargetInfo final : public TargetInfo {
 public:
   ARMTargetInfo();
   RelExpr getRelExpr(uint32_t Type, const SymbolBody &S) const override;
   uint32_t getDynRel(uint32_t Type) const override;
   uint64_t getImplicitAddend(const uint8_t *Buf, uint32_t Type) const override;
+  bool isTlsLocalDynamicRel(uint32_t Type) const override;
   bool isTlsGlobalDynamicRel(uint32_t Type) const override;
   bool isTlsInitialExecRel(uint32_t Type) const override;
   void writeGotPlt(uint8_t *Buf, const SymbolBody &S) const override;
   void writePltHeader(uint8_t *Buf) const override;
   void writePlt(uint8_t *Buf, uint64_t GotEntryAddr, uint64_t PltEntryAddr,
                 int32_t Index, unsigned RelOff) const override;
   RelExpr getThunkExpr(RelExpr Expr, uint32_t RelocType,
                        const InputFile &File,
case R_ARM_GOT_BREL:
     // GOT(S) + A - GOT_ORG
     return R_GOT_OFF;
   case R_ARM_GOT_PREL:
   case R_ARM_TLS_IE32:
     // GOT(S) + A - P
     return R_GOT_PC;
   case R_ARM_TLS_GD32:
     return R_TLSGD_PC;
+  case R_ARM_TLS_LDM32:
+    return R_TLSLD_PC;
   case R_ARM_BASE_PREL:
     // B(S) + A - P
     // FIXME: currently B(S) assumed to be .got, this may not hold for all
     // platforms.
     return R_GOTONLY_PC;
   case R_ARM_MOVW_PREL_NC:
   case R_ARM_MOVT_PREL:
   case R_ARM_PREL31:
void ARMTargetInfo::relocateOne(uint8_t *Loc, uint32_t Type,
   case R_ARM_ABS32:
   case R_ARM_BASE_PREL:
   case R_ARM_GOTOFF32:
   case R_ARM_GOT_BREL:
   case R_ARM_GOT_PREL:
   case R_ARM_REL32:
   case R_ARM_TLS_GD32:
   case R_ARM_TLS_IE32:
+  case R_ARM_TLS_LDM32:
+  case R_ARM_TLS_LDO32:
   case R_ARM_TLS_LE32:
     write32le(Loc, Val);
     break;
   case R_ARM_PREL31:
     checkInt<31>(Val, Type);
     write32le(Loc, (read32le(Loc) & 0x80000000) | (Val & ~0x80000000));
     break;
   case R_ARM_CALL:
default:
     return 0;
   case R_ARM_ABS32:
   case R_ARM_BASE_PREL:
   case R_ARM_GOTOFF32:
   case R_ARM_GOT_BREL:
   case R_ARM_GOT_PREL:
   case R_ARM_REL32:
   case R_ARM_TLS_GD32:
+  case R_ARM_TLS_LDM32:
+  case R_ARM_TLS_LDO32:
   case R_ARM_TLS_IE32:
   case R_ARM_TLS_LE32:
     return SignExtend64<32>(read32le(Buf));
   case R_ARM_PREL31:
     return SignExtend64<31>(read32le(Buf));
   case R_ARM_CALL:
   case R_ARM_JUMP24:
   case R_ARM_PC24:
case R_ARM_THM_MOVT_PREL: {
     return SignExtend64<16>(((Hi & 0x000f) << 12) | // imm4
                             ((Hi & 0x0400) << 1) |  // i
                             ((Lo & 0x7000) >> 4) |  // imm3
                             (Lo & 0x00ff));         // imm8
   }
   }
 }
 
+bool ARMTargetInfo::isTlsLocalDynamicRel(uint32_t Type) const {
+  return Type == R_ARM_TLS_LDO32 || Type == R_ARM_TLS_LDM32;
+}
+
 bool ARMTargetInfo::isTlsGlobalDynamicRel(uint32_t Type) const {
   return Type == R_ARM_TLS_GD32;
 }
 
 bool ARMTargetInfo::isTlsInitialExecRel(uint32_t Type) const {
   return Type == R_ARM_TLS_IE32;
 }
 

test/ELF/arm-tls-ldm32.s

+// RUN: llvm-mc %s -o %t.o -filetype=obj -triple=armv7a-linux-gnueabi
+// RUN: ld.lld %t.o -o %t.so -shared
+// RUN: llvm-readobj -s -dyn-relocations %t.so | FileCheck --check-prefix=SEC %s
+// RUN: llvm-objdump -d -triple=armv7a-linux-gnueabi %t.so | FileCheck %s
+// REQUIRES: arm
+
+// Test the handling of the local-dynamic TLS model. Dynamic loader finds
+// module index R_ARM_TLS_DTPMOD32. The offset in the next GOT slot is 0
+// The R_ARM_TLS_LDO is the offset of the variable within the TLS block.
+ .global __tls_get_addr
+ .text
+ .p2align  2
+ .global _start
+ .syntax unified
+ .arm
+ .type   _start, %function
+_start:
+.L0:
+ nop
+
+ .word   x(tlsldm) + (. - .L0 - 8)
+ .word   x(tlsldo)
+ .word   y(tlsldo)
+
+ .section        .tbss,"awT",%nobits
+ .p2align  2
+ .type   y, %object
+y:
+ .space  4
+ .section        .tdata,"awT",%progbits
+ .p2align  2
+ .type   x, %object
+x:
+ .word   10
+
+// SEC:      Name: .tdata
+// SEC-NEXT: Type: SHT_PROGBITS
+// SEC-NEXT: Flags [
+// SEC-NEXT:   SHF_ALLOC
+// SEC-NEXT:   SHF_TLS
+// SEC-NEXT:   SHF_WRITE
+// SEC-NEXT: ]
+// SEC-NEXT: Address: 0x2000
+// SEC:    Size: 4
+// SEC:    Name: .tbss
+// SEC-NEXT: Type: SHT_NOBITS (0x8)
+// SEC-NEXT: Flags [
+// SEC-NEXT:   SHF_ALLOC
+// SEC-NEXT:   SHF_TLS
+// SEC-NEXT:   SHF_WRITE
+// SEC-NEXT: ]
+// SEC-NEXT: Address: 0x2004
+// SEC:      Size: 4
+
+// SEC: Dynamic Relocations {
+// SEC-NEXT:  0x204C R_ARM_TLS_DTPMOD32 - 0x0
+
+// CHECK: Disassembly of section .text:
+// CHECK-NEXT: _start:
+// CHECK-NEXT: 1000:       00 f0 20 e3     nop
+
+// (0x204c - 0x1004) + (0x1004 - 0x1000 - 8) = 0x1044
+// CHECK:      1004:       44 10 00 00
+// CHECK-NEXT: 1008:       00 00 00 00
+// CHECK-NEXT: 100c:       04 00 00 00
+
+// CHECK-EXE: Disassembly of section .text:
+// CHECK-NEXT-EXE: _start:
+// CHECK-NEXT-EXE:   11000:       00 f0 20 e3     nop
+
+// CHECK-EXE:   11004:       fc 0f 00 00
+// CHECK-EXE:   11008:       00 00 00 00
+// CHECK-EXE:   1100c:       04 00 00 00