[ELF] Emit relocation for GOT entry even if it is an absolute symbol

[evgeny777]

Summary

This should be done in the following case

sample.s:

.long symbol@gotpcrel

sample.t:

PROVIDE_HIDDEN(symbol = ADDR(.section));

Both ld and gold will produce *_RELATIVE relocation for 'symbol' if we compile sample.s and link shared object using script shared.t.
This patch implements the same behavior for lld.

[ruiu]

I think this is fine, but I'd like to hear what Rafael would say.

[evgeny777]

Rafael, do you have any objections against this?

[evgeny777]

Ping

ELF/Relocations.cpp

if (refersToGotEntry(Expr)) {
                   false, &Body, 0});
         continue;
       }
 
       if (Body.isInGot())
         continue;
 
       Out<ELFT>::Got->addEntry(Body);
-      if (Preemptible || (Config->Pic && !isAbsolute<ELFT>(Body))) {
+      if (Preemptible || Config->Pic) {
         uint32_t DynType;
         if (Body.isTls())
           DynType = Target->TlsGotRel;
         else if (Preemptible)
           DynType = Target->GotRel;
         else
           DynType = Target->RelativeRel;
         AddDyn({DynType, Out<ELFT>::Got, Body.getGotOffset<ELFT>(),

test/ELF/abs-hidden.s

 // CHECK-NEXT: Address: 0x1000
 // CHECK-NEXT: Offset:
 // CHECK-NEXT: Size: 12
 // CHECK-NEXT: Link: 0
 // CHECK-NEXT: Info: 0
 // CHECK-NEXT: AddressAlignment: 4
 // CHECK-NEXT: EntrySize: 0
 // CHECK-NEXT: SectionData (
-// CHECK-NEXT:   0000: 42000000 00000000 58100000
-//                                       0x2060 - (0x1000 + 8) = 1058
+// CHECK-NEXT:   0000: 42000000 00000000 98100000
+//                                       0x20a0 - (0x1000 + 8) = 1098
 // CHECK-NEXT: )
 
-// CHECK:      Name: .got (38)
+// CHECK:      Name: .got (48)
 // CHECK-NEXT: Type: SHT_PROGBITS
 // CHECK-NEXT: Flags [
 // CHECK-NEXT:   SHF_ALLOC
 // CHECK-NEXT:   SHF_WRITE
 // CHECK-NEXT: ]
-// CHECK-NEXT: Address: 0x2060
+// CHECK-NEXT: Address: 0x20A0
 // CHECK-NEXT: Offset:
 // CHECK-NEXT: Size: 8
 // CHECK-NEXT: Link: 0
 // CHECK-NEXT: Info: 0
 // CHECK-NEXT: AddressAlignment: 8
 // CHECK-NEXT: EntrySize: 0
 // CHECK-NEXT: SectionData (
 // CHECK-NEXT:   0000: 42000000 00000000
 // CHECK-NEXT: )
 
 // CHECK:      Relocations [
+// CHECK-NEXT:  Section (4) .rela.dyn {
+// CHECK-NEXT:    0x20A0 R_X86_64_RELATIVE - 0x42
+// CHECK-NEXT:  }
 // CHECK-NEXT: ]
+

test/ELF/arm-got-relative.s

 
  .globl function
  .align 2
 function:
  .type function, %function
  bx lr
 
 // CHECK: Dynamic Relocations {
-// CHECK-NEXT:  0x204C R_ARM_GLOB_DAT function 0x0
+// CHECK-NEXT:  0x2050 R_ARM_RELATIVE - 0x0
+// CHECK-NEXT:  0x2054 R_ARM_GLOB_DAT function 0x0
 
 // CHECK: Name: _GLOBAL_OFFSET_TABLE_ (16)
 // CHECK-NEXT:    Value: 0x0
 // CHECK-NEXT:    Size:
 // CHECK-NEXT:    Binding: Local
 // CHECK-NEXT:    Type: None
 // CHECK-NEXT:    Other [
 // CHECK-NEXT:      STV_HIDDEN
 // CHECK-NEXT:    ]
 // CHECK-NEXT:    Section: Absolute
 
 // CODE: Disassembly of section .text:
 // CODE-NEXT: _start:
 // CODE-NEXT:    1000:        08 30 9f e5    ldr     r3, [pc, #8]
 // CODE-NEXT:    1004:        08 20 9f e5    ldr     r2, [pc, #8]
 // CODE-NEXT:    1008:        03 00 8f e0    add     r0, pc, r3
 // CODE-NEXT:    100c:        1e ff 2f e1    bx      lr
 // CODE:$d.1:
 // (_GLOBAL_OFFSET_TABLE_ = 0x2048) - (0x1008 + 8) 0x1038
-// CODE-NEXT:    1010:        38 10 00 00
+// CODE-NEXT:    1010:        40 10 00 00
 // (Got(function) - GotBase = 0x4
 // CODE-NEXT:    1014:        04 00 00 00

test/ELF/pie-weak.s

 # RUN: llvm-mc -filetype=obj -relax-relocations=false -triple=x86_64-unknown-linux %s -o %t.o
 # RUN: ld.lld -pie %t.o -o %t
 # RUN: llvm-readobj -r %t | FileCheck --check-prefix=RELOCS %s
 # RUN: llvm-objdump -d %t | FileCheck --check-prefix=DISASM %s
 
 # RELOCS:      Relocations [
+# RELOCS-NEXT:  Section (4) .rela.dyn {
+# RELOCS-NEXT:    0x20B0 R_X86_64_RELATIVE - 0x0
+# RELOCS-NEXT:  }
 # RELOCS-NEXT: ]
 
 .weak foo
 
 .globl _start
 _start:
 # DISASM: _start:
-# DISASM-NEXT: 1000: 48 8b 05 69 10 00 00 movq 4201(%rip), %rax
+# DISASM-NEXT:1000: 48 8b 05 a9 10 00 00  movq  4265(%rip), %rax
 #                                              ^ .got - (.text + 7)
 mov foo@gotpcrel(%rip), %rax