[03/10] ELF/AArch64: Add support for R_AARCH64_PREL64

[zatrazz]

Summary

Hi ruiu, shankarke,

This is re-post of a previous attempt. This patch adds support for the R_AARCH64_PREL64 relocation type and add tests.

Patch by Will Newton.

[• shankar.easwaran]

Missing debug?

[ruiu]

Debug code in this file occupies more lines than the actual code in this
file, so I doubt it's really useful. It looks to me that it rather clutters
the code. It's up to the maintainer, though. LGTM.

[zatrazz]

I will add a DEBUG entry to be in par with rest of relocation code.

lib/ReaderWriter/ELF/AArch64/AArch64RelocationHandler.cpp

DEBUG(llvm::dbgs() << "\t\tHandle " << LLVM_FUNCTION_NAME << " -";
         llvm::dbgs() << " S: 0x" << Twine::utohexstr(S);
         llvm::dbgs() << " A: 0x" << Twine::utohexstr(A);
         llvm::dbgs() << " P: 0x" << Twine::utohexstr(P);
         llvm::dbgs() << " result: 0x" << Twine::utohexstr(result) << "\n");
   write16le(location, result | read16le(location));
   return std::error_code();
 }
 
+/// \brief R_AARCH64_PREL64 - word64: S + A - P
+static void relocR_AARCH64_PREL64(uint8_t *location, uint64_t P,
+                                  uint64_t S, int64_t A) {
+  int64_t result = S + A - P;
+  write64le(location, result + read64le(location));
+}
+
 /// \brief R_AARCH64_PREL32 - word32: S + A - P
 static std::error_code relocR_AARCH64_PREL32(uint8_t *location, uint64_t P,
                                              uint64_t S, int64_t A) {
   int64_t result = S + A - P;
   if (!withinSignedUnsignedRange(result, 32))
     return make_out_of_range_reloc_error();
   write32le(location, result + read32le(location));
   return std::error_code();
case R_AARCH64_NONE:
     break;
   case R_AARCH64_ABS64:
     relocR_AARCH64_ABS64(loc, reloc, target, addend);
     break;
   case R_AARCH64_ABS32:
     return relocR_AARCH64_ABS32(loc, reloc, target, addend);
   case R_AARCH64_ABS16:
     return relocR_AARCH64_ABS16(loc, reloc, target, addend);
+  case R_AARCH64_PREL64:
+    relocR_AARCH64_PREL64(loc, reloc, target, addend);
+    break;
   case R_AARCH64_PREL32:
     return relocR_AARCH64_PREL32(loc, reloc, target, addend);
   // Runtime only relocations. Ignore here.
   case R_AARCH64_RELATIVE:
   case R_AARCH64_IRELATIVE:
   case R_AARCH64_JUMP_SLOT:
   case R_AARCH64_GLOB_DAT:
     break;

test/elf/AArch64/rel-prel64.test

+# Check handling of R_AARCH64_PREL64 relocation.
+# RUN: yaml2obj -format=elf %s > %t-obj
+# RUN: lld -flavor gnu -target arm64 -o %t-exe %t-obj
+# RUN: llvm-objdump -s -t %t-exe | FileCheck %s
+
+# CHECK: Contents of section .data:
+# CHECK-NEXT: 401060 09000000 00000080 f9ffffff ffffff7f ................
+#                    ^^ data2 - data1 + 0x8000000000000001 = 0x8000000000000009
+#                                      ^^ data1 - data2 + 0x8000000000000001 = 0x7ffffffffffffff9
+# CHECK: SYMBOL TABLE:
+# CHECK: 00401060 g  .data  00000008 data1
+# CHECK: 00401068 g  .data  00000008 data2
+
+!ELF
+FileHeader: !FileHeader
+  Class: ELFCLASS64
+  Data: ELFDATA2LSB
+  Type: ET_REL
+  Machine: EM_AARCH64
+
+Sections:
+- Name: .text
+  Type: SHT_PROGBITS
+  Content: "00000000"
+  AddressAlign: 16
+  Flags: [SHF_ALLOC, SHF_EXECINSTR]
+- Name: .data
+  Type: SHT_PROGBITS
+  Content: "00000000000000000000000000000000"
+  AddressAlign: 16
+  Flags: [SHF_ALLOC, SHF_WRITE]
+
+- Name: .rela.data
+  Type: SHT_RELA
+  Info: .data
+  AddressAlign: 8
+  Relocations:
+    - Offset: 0x0
+      Symbol: data2
+      Type: R_AARCH64_PREL64
+      Addend: -9223372036854775807
+    - Offset: 0x8
+      Symbol: data1
+      Type: R_AARCH64_PREL64
+      Addend: -9223372036854775807
+
+Symbols:
+  Global:
+    - Name: _start
+      Section: .text
+      Value: 0x0
+      Size: 4
+    - Name: data1
+      Section: .data
+      Size: 8
+    - Name: data2
+      Section: .data
+      Value: 0x8
+      Size: 8