ELF/AArch64: Add support for R_AARCH64_PREL16

Add support for the R_AARCH64_PREL16 relocation type and add tests.

Patch by Will Newton.

llvm-svn: 234742

lld/lib/ReaderWriter/ELF/AArch64/AArch64RelocationHandler.cpp

@@ -98,6 +98,21 @@ static std::error_code relocR_AARCH64_PREL32(uint8_t *location, uint64_t P,
   return std::error_code();
 }
 
+/// \brief R_AARCH64_PREL16 - word16: S + A - P
+static std::error_code relocR_AARCH64_PREL16(uint8_t *location, uint64_t P,
+                                             uint64_t S, int64_t A) {
+  int64_t result = S + A - P;
+  if (!withinSignedUnsignedRange(result, 16))
+    return make_out_of_range_reloc_error();
+  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_ADR_PREL_PG_HI21 - Page(S+A) - Page(P)
 static void relocR_AARCH64_ADR_PREL_PG_HI21(uint8_t *location, uint64_t P,
                                             uint64_t S, int64_t A) {
@@ -115,7 +130,6 @@ static void relocR_AARCH64_ADR_PREL_PG_HI21(uint8_t *location, uint64_t P,
         llvm::dbgs() << " immlo: " << Twine::utohexstr(immlo);
         llvm::dbgs() << " result: " << Twine::utohexstr(result) << "\n");
   write32le(location, immlo | immhi | read32le(location));
-  // TODO: Make sure this is correct!
 }
 
 /// \brief R_AARCH64_ADR_PREL_LO21 - S + A - P
@@ -382,6 +396,8 @@ std::error_code AArch64TargetRelocationHandler::applyRelocation(
     break;
   case R_AARCH64_PREL32:
     return relocR_AARCH64_PREL32(loc, reloc, target, addend);
+  case R_AARCH64_PREL16:
+    return relocR_AARCH64_PREL16(loc, reloc, target, addend);
   // Runtime only relocations. Ignore here.
   case R_AARCH64_RELATIVE:
   case R_AARCH64_IRELATIVE:

lld/test/elf/AArch64/rel-prel16-overflow.test

@@ -0,0 +1,53 @@
+# Check handling of R_AARCH64_PREL16 relocation overflow.
+# RUN: yaml2obj -format=elf %s > %t-obj
+# RUN: not lld -flavor gnu -target arm64 -o %t-exe %t-obj 2>&1 | FileCheck %s
+
+# CHECK: Relocation out of range in file {{.*}}: reference from data1+0 to data2+524289 of type 262 (R_AARCH64_PREL16)
+# CHECK: Relocation out of range in file {{.*}}: reference from data2+0 to data1+524289 of type 262 (R_AARCH64_PREL16)
+
+!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: "0000000000000000"
+  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_PREL16
+      Addend: 0x80001
+    - Offset: 0x2
+      Symbol: data1
+      Type: R_AARCH64_PREL16
+      Addend: 0x80001
+
+Symbols:
+  Global:
+    - Name: _start
+      Section: .text
+      Value: 0x0
+      Size: 4
+    - Name: data1
+      Section: .data
+      Size: 2
+    - Name: data2
+      Section: .data
+      Value: 0x2
+      Size: 2

lld/test/elf/AArch64/rel-prel16.test

@@ -0,0 +1,59 @@
+# Check handling of R_AARCH64_PREL16 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 0380ff7f 00000000 ........
+#                    ^^ data2 - data1 + 0x8001 = 0x8003
+#                             ^^ data1 - data2 + 0x8001 = 0x7fff
+# CHECK: SYMBOL TABLE:
+# CHECK: 00401060 g  .data  00000002 data1
+# CHECK: 00401062 g  .data  00000006 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: "0000000000000000"
+  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_PREL16
+      Addend: 0x8001
+    - Offset: 0x2
+      Symbol: data1
+      Type: R_AARCH64_PREL16
+      Addend: 0x8001
+
+Symbols:
+  Global:
+    - Name: _start
+      Section: .text
+      Value: 0x0
+      Size: 4
+    - Name: data1
+      Section: .data
+      Size: 2
+    - Name: data2
+      Section: .data
+      Value: 0x2
+      Size: 2