[JITLink][ELF/AARCH64] Implement R_AARCH64_PREL32 and R_AARCH64_PREL64

[sunho]

Summary

This patch implements R_AARCH64_PREL64 and R_AARCH64_PREL32 relocations that is used in eh frame pointers. The test case utlizes obj2yaml tool to create an artifical eh frame that generates related relocation types.

[sgraenitz]

llvm/test/ExecutionEngine/JITLink/AArch64/ELF_aarch64_ehframe.test

3

Trailing whitespace

62

Where do the offsets come from and what is text - eh_frame - <offset> supposed to be pointing at? I am getting these sections in the object:

.text
0000 e0031f2a c0035fd6

.eh_frame
0000 10000000 00000000 017a5200 017c1e01
0010 1b0c1f00 10000000 18000000 00000000
0020 08000000 00000000          ^^^^^^^^ eh_frame + 28
     ^^^^^^^^^^^^^^^^^ eh_frame + 32

[sunho]

llvm/test/ExecutionEngine/JITLink/AArch64/ELF_aarch64_ehframe.test

62

It's the delta from eh_frame + 28 to text + 0. eh_frame + 28 is the bytes that's going to be patched and it should point to text + 0. I can probably make it more clear by rewriting it to

jitlink-check: *{4}(eh_frame + 28) = (text + 0) - (eh_frame + 28)

[sunho]

llvm/test/ExecutionEngine/JITLink/AArch64/ELF_aarch64_ehframe.test

3

👀

[sunho]

Rebase and address stefan's comments

[lhames]

LGTM. Thanks @sunho!

llvm/test/ExecutionEngine/JITLink/AArch64/ELF_aarch64_ehframe.test

2–4

For single-file tests that don't need to name the object file in a jitlink-check expression, we usually omit the separate subdirectory:

# RUN: yaml2obj -o %t.o %s
# RUN: llvm-jitlink -noexec -check %s %t.o

I'll make this simplification here when I land the patch.

llvm/lib/ExecutionEngine/JITLink/ELF_aarch64.cpp

enum ELFAArch64RelocationKind : Edge::Kind {
     ELFAdrPage21,
     ELFAddAbs12,
     ELFLdSt8Abs12,
     ELFLdSt16Abs12,
     ELFLdSt32Abs12,
     ELFLdSt64Abs12,
     ELFLdSt128Abs12,
     ELFAbs64,
+    ELFPrel32,
+    ELFPrel64,
     ELFAdrGOTPage21,
     ELFLd64GOTLo12,
   };
 
   static Expected<ELFAArch64RelocationKind>
   getRelocationKind(const uint32_t Type) {
     using namespace aarch64;
     switch (Type) {
getRelocationKind(const uint32_t Type) {
     case ELF::R_AARCH64_LDST32_ABS_LO12_NC:
       return ELFLdSt32Abs12;
     case ELF::R_AARCH64_LDST64_ABS_LO12_NC:
       return ELFLdSt64Abs12;
     case ELF::R_AARCH64_LDST128_ABS_LO12_NC:
       return ELFLdSt128Abs12;
     case ELF::R_AARCH64_ABS64:
       return ELFAbs64;
+    case ELF::R_AARCH64_PREL32:
+      return ELFPrel32;
+    case ELF::R_AARCH64_PREL64:
+      return ELFPrel64;
     case ELF::R_AARCH64_ADR_GOT_PAGE:
       return ELFAdrGOTPage21;
     case ELF::R_AARCH64_LD64_GOT_LO12_NC:
       return ELFLd64GOTLo12;
     }
 
     return make_error<JITLinkError>("Unsupported aarch64 relocation:" +
                                     formatv("{0:d}", Type));
case ELFLdSt128Abs12: {
 
       Kind = aarch64::PageOffset12;
       break;
     }
     case ELFAbs64: {
       Kind = aarch64::Pointer64;
       break;
     }
+    case ELFPrel32: {
+      Kind = aarch64::Delta32;
+      break;
+    }
+    case ELFPrel64: {
+      Kind = aarch64::Delta64;
+      break;
+    }
     case ELFAdrGOTPage21: {
       Kind = aarch64::GOTPage21;
       break;
     }
     case ELFLd64GOTLo12: {
       Kind = aarch64::GOTPageOffset12;
       break;
     }
const char *getELFAArch64RelocationKindName(Edge::Kind R) {
     case ELFLdSt32Abs12:
       return "ELFLdSt32Abs12";
     case ELFLdSt64Abs12:
       return "ELFLdSt64Abs12";
     case ELFLdSt128Abs12:
       return "ELFLdSt128Abs12";
     case ELFAbs64:
       return "ELFAbs64";
+    case ELFPrel32:
+      return "ELFPrel32";
+    case ELFPrel64:
+      return "ELFPrel64";
     case ELFAdrGOTPage21:
       return "ELFAdrGOTPage21";
     case ELFLd64GOTLo12:
       return "ELFLd64GOTLo12";
     default:
       return getGenericEdgeKindName(static_cast<Edge::Kind>(R));
     }
   }

llvm/test/ExecutionEngine/JITLink/AArch64/ELF_aarch64_ehframe.test

+# RUN: yaml2obj -o %t.o %s
+# RUN: llvm-jitlink -noexec -check %s %t.o
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_AARCH64
+  SectionHeaderStringTable: .strtab
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x4
+    Content:         E0031F2AC0035FD6
+  - Name:            .eh_frame
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+    AddressAlign:    0x8
+    Content:         1000000000000000017A5200017C1E011B0C1F001000000018000000000000000800000000000000
+  - Name:            .rela.eh_frame
+    Type:            SHT_RELA
+    Flags:           [ SHF_INFO_LINK ]
+    Link:            .symtab
+    AddressAlign:    0x8
+    Info:            .eh_frame
+    Relocations:
+      - Offset:          0x1C
+        Symbol:          text
+        Type:            R_AARCH64_PREL32
+      - Offset:          0x20
+        Symbol:          text
+        Type:            R_AARCH64_PREL64
+  - Type:            SectionHeaderTable
+    Sections:
+      - Name:            .strtab
+      - Name:            .text
+      - Name:            .eh_frame
+      - Name:            .rela.eh_frame
+      - Name:            .symtab
+Symbols:
+  - Name:            text
+    Type:            STT_SECTION
+    Binding:         STB_GLOBAL
+    Section:         .text
+    Size:            0x8
+  - Name:            eh_frame
+    Type:            STT_SECTION
+    Binding:         STB_GLOBAL
+    Section:         .eh_frame
+    Size:            0x28
+  - Name:            main
+    Type:            STT_FUNC
+    Section:         .text
+    Binding:         STB_GLOBAL
+    Size:            0x8
+
+# jitlink-check: *{4}(eh_frame + 28) = (text + 0) - (eh_frame + 28)
+# jitlink-check: *{8}(eh_frame + 32) = (text + 0) - (eh_frame + 32)
 No newline at end of file