[JITLink][AArch32] Implement ELF relocation R_ARM_NONE

Author: weliveindetail

llvm/include/llvm/ExecutionEngine/JITLink/aarch32.h

@@ -101,7 +101,11 @@ enum EdgeKind_aarch32 : Edge::Kind {
   Thumb_MovtPrel,
 
   LastThumbRelocation = Thumb_MovtPrel,
-  LastRelocation = LastThumbRelocation,
+
+  /// No-op relocation
+  None,
+
+  LastRelocation = None,
 };
 
 /// Flags enum for AArch32-specific symbol properties
@@ -293,7 +297,8 @@ inline Expected<int64_t> readAddend(LinkGraph &G, Block &B,
   if (Kind <= LastThumbRelocation)
     return readAddendThumb(G, B, Offset, Kind, ArmCfg);
 
-  llvm_unreachable("Relocation must be of class Data, Arm or Thumb");
+  assert(Kind == None && "Not associated with a relocation class");
+  return 0;
 }
 
 /// Helper function to apply the fixup for Data-class relocations.
@@ -320,7 +325,8 @@ inline Error applyFixup(LinkGraph &G, Block &B, const Edge &E,
   if (Kind <= LastThumbRelocation)
     return applyFixupThumb(G, B, E, ArmCfg);
 
-  llvm_unreachable("Relocation must be of class Data, Arm or Thumb");
+  assert(Kind == None && "Not associated with a relocation class");
+  return Error::success();
 }
 
 /// Populate a Global Offset Table from edges that request it.

llvm/lib/ExecutionEngine/JITLink/ELF_aarch32.cpp

@@ -48,6 +48,8 @@ getJITLinkEdgeKind(uint32_t ELFType, const aarch32::ArmConfig &ArmCfg) {
     return aarch32::Arm_MovwAbsNC;
   case ELF::R_ARM_MOVT_ABS:
     return aarch32::Arm_MovtAbs;
+  case ELF::R_ARM_NONE:
+    return aarch32::None;
   case ELF::R_ARM_TARGET1:
     return (ArmCfg.Target1Rel) ? aarch32::Data_Delta32
                                : aarch32::Data_Pointer32;
@@ -99,6 +101,8 @@ Expected<uint32_t> getELFRelocationType(Edge::Kind Kind) {
     return ELF::R_ARM_THM_MOVW_PREL_NC;
   case aarch32::Thumb_MovtPrel:
     return ELF::R_ARM_THM_MOVT_PREL;
+  case aarch32::None:
+    return ELF::R_ARM_NONE;
   }
 
   return make_error<JITLinkError>(formatv("Invalid aarch32 edge {0:d}: ",

llvm/lib/ExecutionEngine/JITLink/aarch32.cpp

@@ -766,6 +766,7 @@ const char *getEdgeKindName(Edge::Kind K) {
     KIND_NAME_CASE(Thumb_MovtAbs)
     KIND_NAME_CASE(Thumb_MovwPrelNC)
     KIND_NAME_CASE(Thumb_MovtPrel)
+    KIND_NAME_CASE(None)
   default:
     return getGenericEdgeKindName(K);
   }

llvm/test/ExecutionEngine/JITLink/AArch32/ELF_relocations_data.s

@@ -64,6 +64,30 @@ got_prel_offset:
 	.size	got_prel_offset, .-got_prel_offset
 	.size	got_prel, .-got_prel
 
+# EH personality routine
+# CHECK-TYPE: {{[0-9a-f]+}} R_ARM_NONE __aeabi_unwind_cpp_pr0
+	.globl __aeabi_unwind_cpp_pr0
+	.type __aeabi_unwind_cpp_pr0,%function
+	.align 2
+__aeabi_unwind_cpp_pr0:
+	bx lr
+
+# Generate reference to EH personality (right now we ignore the resulting
+# R_ARM_PREL31 relocation since it's in .ARM.exidx)
+	.globl  prel31
+	.type   prel31,%function
+	.align  2
+prel31:
+	.fnstart
+	.save   {r11, lr}
+	push    {r11, lr}
+	.setfp  r11, sp
+	mov     r11, sp
+	pop     {r11, lr}
+	mov     pc, lr
+	.size   prel31,.-prel31
+	.fnend
+
 # This test is executable with any 4-byte external target:
 #  > echo "unsigned target = 42;" | clang -target armv7-linux-gnueabihf -o target.o -c -xc -
 #  > llvm-jitlink target.o armv7/out.o

llvm/unittests/ExecutionEngine/JITLink/AArch32Tests.cpp

@@ -49,7 +49,7 @@ Expected<uint32_t> getELFRelocationType(Edge::Kind Kind);
 TEST(AArch32_ELF, EdgeKinds) {
   // Fails: Invalid ELF type -> JITLink kind
   aarch32::ArmConfig Cfg;
-  Expected<uint32_t> ErrKind = getJITLinkEdgeKind(ELF::R_ARM_NONE, Cfg);
+  Expected<uint32_t> ErrKind = getJITLinkEdgeKind(ELF::R_ARM_ME_TOO, Cfg);
   EXPECT_TRUE(errorToBool(ErrKind.takeError()));
 
   // Fails: Invalid JITLink kind -> ELF type