[ELF2/AArch64] Add lazy relocation for AArch64 target.

[ruiu]

LGTM with a nit.

ELF/Target.cpp

617

Remove this function.

[davide]

Looks good, thanks.

[ikudrin]

ELF/Target.cpp

617

Why? If I remove it, I'll need to fill PCRelReloc instead, but this function is called for different types of relocations, R_AARCH64_JUMP26 and R_AARCH64_CALL26 in particular. And these relocations are supported by the relocateOne() method anyway.

[ruiu]

LGTM

ELF/Target.cpp

617

I'm sorry I thought that this is a dead function. It is not.

The name of this function is inconsistent. Could you do s/PLT/Plt/ in a follow-up patch?

[ikudrin]

ELF/Target.cpp

617

Sure.

ELF/Target.cpp

public:
   void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
                    uint64_t SA) const override;
   bool isRelRelative(uint32_t Type) const override;
 };
 
 class AArch64TargetInfo final : public TargetInfo {
 public:
   AArch64TargetInfo();
+  unsigned getPLTRefReloc(unsigned Type) const override;
   void writeGotPltEntry(uint8_t *Buf, uint64_t Plt) const override;
   void writePltZeroEntry(uint8_t *Buf, uint64_t GotEntryAddr,
                          uint64_t PltEntryAddr) const override;
   void writePltEntry(uint8_t *Buf, uint64_t GotEntryAddr,
                      uint64_t PltEntryAddr, int32_t Index) const override;
   bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const override;
   bool relocNeedsPlt(uint32_t Type, const SymbolBody &S) const override;
   void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
void PPC64TargetInfo::relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
   case R_PPC64_TOC:
     write64be(Loc, SA);
     break;
   default:
     error("unrecognized reloc " + Twine(Type));
   }
 }
 
-AArch64TargetInfo::AArch64TargetInfo() {}
+AArch64TargetInfo::AArch64TargetInfo() {
+  PltReloc = R_AARCH64_JUMP_SLOT;
+  LazyRelocations = true;
+  PltEntrySize = 16;
+  PltZeroEntrySize = 32;
+}
+
+unsigned AArch64TargetInfo::getPLTRefReloc(unsigned Type) const { return Type; }
+
+void AArch64TargetInfo::writeGotPltEntry(uint8_t *Buf, uint64_t Plt) const {
+  write64le(Buf, Out<ELF64LE>::Plt->getVA());
+}
 
-void AArch64TargetInfo::writeGotPltEntry(uint8_t *Buf, uint64_t Plt) const {}
 void AArch64TargetInfo::writePltZeroEntry(uint8_t *Buf, uint64_t GotEntryAddr,
-                                          uint64_t PltEntryAddr) const {}
+                                          uint64_t PltEntryAddr) const {
+  const uint8_t PltData[] = {
+      0xf0, 0x7b, 0xbf, 0xa9, // stp  x16, x30, [sp,#-16]!
+      0x10, 0x00, 0x00, 0x90, // adrp  x16, Page(&(.plt.got[2]))
+      0x11, 0x02, 0x40, 0xf9, // ldr  x17, [x16, Offset(&(.plt.got[2]))]
+      0x10, 0x02, 0x00, 0x91, // add  x16, x16, Offset(&(.plt.got[2]))
+      0x20, 0x02, 0x1f, 0xd6, // br x17
+      0x1f, 0x20, 0x03, 0xd5, // nop
+      0x1f, 0x20, 0x03, 0xd5, // nop
+      0x1f, 0x20, 0x03, 0xd5  // nop
+  };
+  memcpy(Buf, PltData, sizeof(PltData));
+
+  relocateOne(Buf + 4, Buf + 8, R_AARCH64_ADR_PREL_PG_HI21, PltEntryAddr + 4,
+              GotEntryAddr + 16);
+  relocateOne(Buf + 8, Buf + 12, R_AARCH64_LDST64_ABS_LO12_NC, PltEntryAddr + 8,
+              GotEntryAddr + 16);
+  relocateOne(Buf + 12, Buf + 16, R_AARCH64_ADD_ABS_LO12_NC, PltEntryAddr + 12,
+              GotEntryAddr + 16);
+}
+
 void AArch64TargetInfo::writePltEntry(uint8_t *Buf, uint64_t GotEntryAddr,
-                                      uint64_t PltEntryAddr, int32_t Index) const {}
+                                      uint64_t PltEntryAddr,
+                                      int32_t Index) const {
+  const uint8_t Inst[] = {
+      0x10, 0x00, 0x00, 0x90, // adrp x16, Page(&(.plt.got[n]))
+      0x11, 0x02, 0x40, 0xf9, // ldr  x17, [x16, Offset(&(.plt.got[n]))]
+      0x10, 0x02, 0x00, 0x91, // add  x16, x16, Offset(&(.plt.got[n]))
+      0x20, 0x02, 0x1f, 0xd6  // br   x17
+  };
+  memcpy(Buf, Inst, sizeof(Inst));
+
+  relocateOne(Buf, Buf + 4, R_AARCH64_ADR_PREL_PG_HI21, PltEntryAddr,
+              GotEntryAddr);
+  relocateOne(Buf + 4, Buf + 8, R_AARCH64_LDST64_ABS_LO12_NC, PltEntryAddr + 4,
+              GotEntryAddr);
+  relocateOne(Buf + 8, Buf + 12, R_AARCH64_ADD_ABS_LO12_NC, PltEntryAddr + 8,
+              GotEntryAddr);
+}
+
 bool AArch64TargetInfo::relocNeedsGot(uint32_t Type,
                                       const SymbolBody &S) const {
-  return false;
+  return relocNeedsPlt(Type, S);
 }
+
 bool AArch64TargetInfo::relocNeedsPlt(uint32_t Type,
                                       const SymbolBody &S) const {
+  switch (Type) {
+  default:
     return false;
+  case R_AARCH64_JUMP26:
+  case R_AARCH64_CALL26:
+    return canBePreempted(&S, true);
+  }
 }
 
 static void updateAArch64Adr(uint8_t *L, uint64_t Imm) {
   uint32_t ImmLo = (Imm & 0x3) << 29;
   uint32_t ImmHi = ((Imm & 0x1FFFFC) >> 2) << 5;
   uint64_t Mask = (0x3 << 29) | (0x7FFFF << 5);
   write32le(L, (read32le(L) & ~Mask) | ImmLo | ImmHi);
 }

test/ELF/aarch64-call26-error.s

 // RUN: llvm-mc -filetype=obj -triple=aarch64-pc-freebsd %S/Inputs/abs.s -o %tabs
 // RUN: llvm-mc -filetype=obj -triple=aarch64-pc-freebsd %s -o %t
-// RUN: not ld.lld2 -shared %t %tabs -o %t2 2>&1 | FileCheck %s
+// RUN: not ld.lld2 %t %tabs -o %t2 2>&1 | FileCheck %s
 // REQUIRES: aarch64
 
 .text
+.globl _start
+_start:
     bl big
 
 // CHECK: R_AARCH64_CALL26 out of range

test/ELF/aarch64-jump26-error.s

 // RUN: llvm-mc -filetype=obj -triple=aarch64-pc-freebsd %S/Inputs/abs.s -o %tabs
 // RUN: llvm-mc -filetype=obj -triple=aarch64-pc-freebsd %s -o %t
-// RUN: not ld.lld2 -shared %t %tabs -o %t2 2>&1 | FileCheck %s
+// RUN: not ld.lld2 %t %tabs -o %t2 2>&1 | FileCheck %s
 // REQUIRES: aarch64
 
 .text
+.globl _start
+_start:
     b big
 
 // CHECK: R_AARCH64_JUMP26 out of range

test/ELF/plt-aarch64.s

+// RUN: llvm-mc -filetype=obj -triple=aarch64-pc-freebsd %s -o %t.o
+// RUN: llvm-mc -filetype=obj -triple=aarch64-pc-freebsd %p/Inputs/shared.s -o %t2.o
+// RUN: ld.lld2 -shared %t2.o -o %t2.so
+// RUN: ld.lld2 -shared %t.o %t2.so -o %t.so
+// RUN: ld.lld2 %t.o %t2.so -o %t.exe
+// RUN: llvm-readobj -s -r %t.so | FileCheck --check-prefix=CHECKDSO %s
+// RUN: llvm-objdump -s -section=.got.plt %t.so | FileCheck --check-prefix=DUMPDSO %s
+// RUN: llvm-objdump -d %t.so | FileCheck --check-prefix=DISASMDSO %s
+// RUN: llvm-readobj -s -r %t.exe | FileCheck --check-prefix=CHECKEXE %s
+// RUN: llvm-objdump -s -section=.got.plt %t.exe | FileCheck --check-prefix=DUMPEXE %s
+// RUN: llvm-objdump -d %t.exe | FileCheck --check-prefix=DISASMEXE %s
+
+// REQUIRES: aarch64
+
+// CHECKDSO:     Name: .plt
+// CHECKDSO-NEXT:     Type: SHT_PROGBITS
+// CHECKDSO-NEXT:     Flags [
+// CHECKDSO-NEXT:       SHF_ALLOC
+// CHECKDSO-NEXT:       SHF_EXECINSTR
+// CHECKDSO-NEXT:     ]
+// CHECKDSO-NEXT:     Address: 0x1010
+// CHECKDSO-NEXT:     Offset:
+// CHECKDSO-NEXT:     Size: 80
+// CHECKDSO-NEXT:     Link:
+// CHECKDSO-NEXT:     Info:
+// CHECKDSO-NEXT:     AddressAlignment: 16
+
+// CHECKDSO:     Name: .got.plt
+// CHECKDSO-NEXT:     Type: SHT_PROGBITS
+// CHECKDSO-NEXT:     Flags [
+// CHECKDSO-NEXT:       SHF_ALLOC
+// CHECKDSO-NEXT:       SHF_WRITE
+// CHECKDSO-NEXT:     ]
+// CHECKDSO-NEXT:     Address: 0x20B0
+// CHECKDSO-NEXT:     Offset:
+// CHECKDSO-NEXT:     Size: 48
+// CHECKDSO-NEXT:     Link:
+// CHECKDSO-NEXT:     Info:
+// CHECKDSO-NEXT:     AddressAlignment: 8
+
+// CHECKDSO: Relocations [
+// CHECKDSO-NEXT:   Section ({{.*}}) .rela.plt {
+
+// &(.got.plt[3]) = 0x20B0 + 3 * 8 = 0x20C8
+// CHECKDSO-NEXT:     0x20C8 R_AARCH64_JUMP_SLOT foo
+
+// &(.got.plt[4]) = 0x20B0 + 4 * 8 = 0x20D0
+// CHECKDSO-NEXT:     0x20D0 R_AARCH64_JUMP_SLOT bar
+
+// &(.got.plt[5]) = 0x20B0 + 5 * 8 = 0x20D8
+// CHECKDSO-NEXT:     0x20D8 R_AARCH64_JUMP_SLOT weak
+// CHECKDSO-NEXT:   }
+// CHECKDSO-NEXT: ]
+
+// DUMPDSO: Contents of section .got.plt:
+// .got.plt[0..2] = 0 (reserved)
+// .got.plt[3..5] = .plt = 0x1010
+// DUMPDSO-NEXT:  20b0 00000000 00000000 00000000 00000000  ................
+// DUMPDSO-NEXT:  20c0 00000000 00000000 10100000 00000000  ................
+// DUMPDSO-NEXT:  20d0 10100000 00000000 10100000 00000000  ................
+
+// DISASMDSO: _start:
+// 0x1030 - 0x1000 = 0x30 = 48
+// DISASMDSO-NEXT:     1000:  0c 00 00 14   b #48
+// 0x1040 - 0x1004 = 0x3c = 60
+// DISASMDSO-NEXT:     1004:  0f 00 00 14   b #60
+// 0x1050 - 0x1008 = 0x48 = 72
+// DISASMDSO-NEXT:     1008:  12 00 00 14   b #72
+
+// DISASMDSO: foo:
+// DISASMDSO-NEXT:     100c:  1f 20 03 d5   nop
+
+// DISASMDSO: Disassembly of section .plt:
+// DISASMDSO-NEXT: .plt:
+// DISASMDSO-NEXT:     1010:  f0 7b bf a9   stp x16, x30, [sp, #-16]!
+// &(.got.plt[2]) = 0x20B0 + 2 * 8 = 0x20C0
+// Page(0x20C0) - Page(0x1014) = 0x2000 - 0x1000 = 0x1000 = 4096
+// DISASMDSO-NEXT:     1014:  10 00 00 b0   adrp  x16, #4096
+// 0x20c0 & 0xFFF = 0xC0 = 192
+// DISASMDSO-NEXT:     1018:  11 62 40 f9   ldr x17, [x16, #192]
+// DISASMDSO-NEXT:     101c:  10 02 03 91   add x16, x16, #192
+// DISASMDSO-NEXT:     1020:  20 02 1f d6   br  x17
+// DISASMDSO-NEXT:     1024:  1f 20 03 d5   nop
+// DISASMDSO-NEXT:     1028:  1f 20 03 d5   nop
+// DISASMDSO-NEXT:     102c:  1f 20 03 d5   nop
+
+// foo@plt
+// Page(0x20C8) - Page(0x1030) = 0x2000 - 0x1000 = 0x1000 = 4096
+// DISASMDSO-NEXT:     1030:  10 00 00 b0   adrp  x16, #4096
+// 0x20C8 & 0xFFF = 0xC8 = 200
+// DISASMDSO-NEXT:     1034:  11 66 40 f9   ldr x17, [x16, #200]
+// DISASMDSO-NEXT:     1038:  10 22 03 91   add x16, x16, #200
+// DISASMDSO-NEXT:     103c:  20 02 1f d6   br  x17
+
+// bar@plt
+// Page(0x20D0) - Page(0x1040) = 0x2000 - 0x1000 = 0x1000 = 4096
+// DISASMDSO-NEXT:     1040:  10 00 00 b0   adrp  x16, #4096
+// 0x20D0 & 0xFFF = 0xD0 = 208
+// DISASMDSO-NEXT:     1044:  11 6a 40 f9   ldr x17, [x16, #208]
+// DISASMDSO-NEXT:     1048:  10 42 03 91   add x16, x16, #208
+// DISASMDSO-NEXT:     104c:  20 02 1f d6   br  x17
+
+// weak@plt
+// Page(0x20D8) - Page(0x1050) = 0x2000 - 0x1000 = 0x1000 = 4096
+// DISASMDSO-NEXT:     1050:  10 00 00 b0   adrp  x16, #4096
+// 0x20D8 & 0xFFF = 0xD8 = 216
+// DISASMDSO-NEXT:     1054:  11 6e 40 f9   ldr x17, [x16, #216]
+// DISASMDSO-NEXT:     1058:  10 62 03 91   add x16, x16, #216
+// DISASMDSO-NEXT:     105c:  20 02 1f d6   br  x17
+
+// CHECKEXE:     Name: .plt
+// CHECKEXE-NEXT:     Type: SHT_PROGBITS
+// CHECKEXE-NEXT:     Flags [
+// CHECKEXE-NEXT:       SHF_ALLOC
+// CHECKEXE-NEXT:       SHF_EXECINSTR
+// CHECKEXE-NEXT:     ]
+// CHECKEXE-NEXT:     Address: 0x11010
+// CHECKEXE-NEXT:     Offset:
+// CHECKEXE-NEXT:     Size: 64
+// CHECKEXE-NEXT:     Link:
+// CHECKEXE-NEXT:     Info:
+// CHECKEXE-NEXT:     AddressAlignment: 16
+
+// CHECKEXE:     Name: .got.plt
+// CHECKEXE-NEXT:     Type: SHT_PROGBITS
+// CHECKEXE-NEXT:     Flags [
+// CHECKEXE-NEXT:       SHF_ALLOC
+// CHECKEXE-NEXT:       SHF_WRITE
+// CHECKEXE-NEXT:     ]
+// CHECKEXE-NEXT:     Address: 0x120B0
+// CHECKEXE-NEXT:     Offset:
+// CHECKEXE-NEXT:     Size: 40
+// CHECKEXE-NEXT:     Link:
+// CHECKEXE-NEXT:     Info:
+// CHECKEXE-NEXT:     AddressAlignment: 8
+
+// CHECKEXE: Relocations [
+// CHECKEXE-NEXT:   Section ({{.*}}) .rela.plt {
+
+// &(.got.plt[3]) = 0x120B0 + 3 * 8 = 0x120C8
+// CHECKEXE-NEXT:     0x120C8 R_AARCH64_JUMP_SLOT bar 0x0
+
+// &(.got.plt[4]) = 0x120B0 + 4 * 8 = 0x120D0
+// CHECKEXE-NEXT:     0x120D0 R_AARCH64_JUMP_SLOT weak 0x0
+// CHECKEXE-NEXT:   }
+// CHECKEXE-NEXT: ]
+
+// DUMPEXE: Contents of section .got.plt:
+// .got.plt[0..2] = 0 (reserved)
+// .got.plt[3..4] = .plt = 0x11010
+// DUMPEXE-NEXT:  120b0 00000000 00000000 00000000 00000000  ................
+// DUMPEXE-NEXT:  120c0 00000000 00000000 10100100 00000000  ................
+// DUMPEXE-NEXT:  120d0 10100100 00000000                    ........
+
+// DISASMEXE: _start:
+// 0x1100c - 0x11000 = 0xc = 12
+// DISASMEXE-NEXT:    11000:  03 00 00 14   b #12
+// 0x11030 - 0x11004 = 0x2c = 44
+// DISASMEXE-NEXT:    11004:  0b 00 00 14   b #44
+// 0x11040 - 0x11008 = 0x38 = 56
+// DISASMEXE-NEXT:    11008:  0e 00 00 14   b #56
+
+// DISASMEXE: foo:
+// DISASMEXE-NEXT:    1100c:  1f 20 03 d5   nop
+
+// DISASMEXE: Disassembly of section .plt:
+// DISASMEXE-NEXT: .plt:
+// DISASMEXE-NEXT:    11010:  f0 7b bf a9   stp x16, x30, [sp, #-16]!
+// &(.got.plt[2]) = 0x120B0 + 2 * 8 = 0x120C0
+// Page(0x120C0) - Page(0x11014) = 0x12000 - 0x11000 = 0x1000 = 4096
+// DISASMEXE-NEXT:    11014:  10 00 00 b0   adrp  x16, #4096
+// 0x120c0 & 0xFFF = 0xC0 = 192
+// DISASMEXE-NEXT:    11018:  11 62 40 f9   ldr x17, [x16, #192]
+// DISASMEXE-NEXT:    1101c:  10 02 03 91   add x16, x16, #192
+// DISASMEXE-NEXT:    11020:  20 02 1f d6   br  x17
+// DISASMEXE-NEXT:    11024:  1f 20 03 d5   nop
+// DISASMEXE-NEXT:    11028:  1f 20 03 d5   nop
+// DISASMEXE-NEXT:    1102c:  1f 20 03 d5   nop
+
+// bar@plt
+// Page(0x120C8) - Page(0x11030) = 0x12000 - 0x11000 = 0x1000 = 4096
+// DISASMEXE-NEXT:    11030:  10 00 00 b0   adrp  x16, #4096
+// 0x120C8 & 0xFFF = 0xC8 = 200
+// DISASMEXE-NEXT:    11034:  11 66 40 f9   ldr x17, [x16, #200]
+// DISASMEXE-NEXT:    11038:  10 22 03 91   add x16, x16, #200
+// DISASMEXE-NEXT:    1103c:  20 02 1f d6   br  x17
+
+// weak@plt
+// Page(0x120D0) - Page(0x11040) = 0x12000 - 0x11000 = 0x1000 = 4096
+// DISASMEXE-NEXT:    11040:  10 00 00 b0   adrp  x16, #4096
+// 0x120D0 & 0xFFF = 0xD0 = 208
+// DISASMEXE-NEXT:    11044:  11 6a 40 f9   ldr x17, [x16, #208]
+// DISASMEXE-NEXT:    11048:  10 42 03 91   add x16, x16, #208
+// DISASMEXE-NEXT:    1104c:  20 02 1f d6   br  x17
+
+.global _start,foo,bar
+.weak weak
+_start:
+  b foo
+  b bar
+  b weak
+
+.section .text2,"ax",@progbits
+foo:
+  nop