[PATCH][lld] ELF/AArch64: Add support for checking for ABS32 overflow

[Will Newton]

Add support for checking overflow when applying a R_AARCH64_ABS32
relocation and add a test to ensure it behaves correctly.
---
 .../ELF/AArch64/AArch64RelocationHandler.cpp       | 20 ++++++--
 test/elf/AArch64/rel-abs32-overflow.test           | 53 ++++++++++++++++++++++
 2 files changed, 68 insertions(+), 5 deletions(-)
 create mode 100644 test/elf/AArch64/rel-abs32-overflow.test

diff --git a/lib/ReaderWriter/ELF/AArch64/AArch64RelocationHandler.cpp b/lib/ReaderWriter/ELF/AArch64/AArch64RelocationHandler.cpp
index 924836d..85a3038 100644
--- a/lib/ReaderWriter/ELF/AArch64/AArch64RelocationHandler.cpp
+++ b/lib/ReaderWriter/ELF/AArch64/AArch64RelocationHandler.cpp
@@ -16,6 +16,13 @@ using namespace elf;
 
 #define PAGE(X) ((X) & ~0x0FFFL)
 
+/// \brief Check X is in the interval (-2^(bits-1), 2^bits]
+bool withinSignedUnsignedRange(int64_t X, int bits) {
+  if (X < -(1L << (bits - 1)) || X >= (1L << bits))
+    return false;
+  return true;
+}
+
 /// \brief R_AARCH64_ABS64 - word64: S + A
 static void relocR_AARCH64_ABS64(uint8_t *location, uint64_t P, uint64_t S,
                                  int64_t A) {
@@ -41,9 +48,11 @@ static void relocR_AARCH64_PREL32(uint8_t *location, uint64_t P, uint64_t S,
 }
 
 /// \brief R_AARCH64_ABS32 - word32:  S + A
-static void relocR_AARCH64_ABS32(uint8_t *location, uint64_t P, uint64_t S,
-                                 int64_t A) {
-  int32_t result = (int32_t)(S + A);
+static std::error_code relocR_AARCH64_ABS32(uint8_t *location, uint64_t P,
+                                            uint64_t S, int64_t A) {
+  int64_t result = S + A;
+  if (!withinSignedUnsignedRange(result, 32))
+    return make_out_of_range_reloc_error();
   DEBUG_WITH_TYPE(
       "AArch64", llvm::dbgs() << "\t\tHandle " << LLVM_FUNCTION_NAME << " -";
       llvm::dbgs() << " S: 0x" << Twine::utohexstr(S);
@@ -53,6 +62,7 @@ static void relocR_AARCH64_ABS32(uint8_t *location, uint64_t P, uint64_t S,
   *reinterpret_cast<llvm::support::ulittle32_t *>(location) =
       result |
       (int32_t) * reinterpret_cast<llvm::support::little32_t *>(location);
+  return std::error_code();
 }
 
 /// \brief R_AARCH64_ADR_PREL_PG_HI21 - Page(S+A) - Page(P)
@@ -385,8 +395,8 @@ std::error_code AArch64TargetRelocationHandler::applyRelocation(
                           ref.addend());
     break;
   case R_AARCH64_ABS32:
-    relocR_AARCH64_ABS32(location, relocVAddress, targetVAddress, ref.addend());
-    break;
+    return relocR_AARCH64_ABS32(location, relocVAddress, targetVAddress,
+                                ref.addend());
   // Runtime only relocations. Ignore here.
   case R_AARCH64_RELATIVE:
   case R_AARCH64_IRELATIVE:
diff --git a/test/elf/AArch64/rel-abs32-overflow.test b/test/elf/AArch64/rel-abs32-overflow.test
new file mode 100644
index 0000000..be65ebc
--- /dev/null
+++ b/test/elf/AArch64/rel-abs32-overflow.test
@@ -0,0 +1,53 @@
+# Check handling of R_AARCH64_ABS32 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+34359738369 of type 258 (R_AARCH64_ABS32)
+# CHECK: Relocation out of range in file {{.*}}: reference from data2+0 to data1+34359738369 of type 258 (R_AARCH64_ABS32)
+
+!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_ABS32
+      Addend: 0x800000001
+    - Offset: 0x4
+      Symbol: data1
+      Type: R_AARCH64_ABS32
+      Addend: 0x800000001
+
+Symbols:
+  Global:
+    - Name: _start
+      Section: .text
+      Value: 0x0
+      Size: 4
+    - Name: data1
+      Section: .data
+      Size: 4
+    - Name: data2
+      Section: .data
+      Value: 0x4
+      Size: 4
-- 
2.1.0