[LLDB][ObjectFileELF] Support LoongArch64 in ApplyReloctions

[SixWeining]

Summary

Currently ApplyReloctions() deals with different archs' relocation types
together (in a single switch() {..}). I think it is incorrect because
different relocation types of different archs may have same enum values.
For example:
R_LARCH_32 and R_X86_64_64 are both 1;
R_LARCH_64 and R_X86_64_PC32 are both 2.

This patch handles each arch in seperate switch() to solve the enum
values conflict issue.

And a new test is added for LoongArch64.

[DavidSpickett]

I see from /usr/include/elf.h on my system that the numbers do restart for each architecture. We got away with it for the set of relocations we were looking at. I like the new structure, it is clearer especially for the signed checks.

I presume the definitions for the relocations actually come from llvm/include/llvm/BinaryFormat/ELFRelocs/LoongArch.def, so this will build fine with a toolchain that doesn't know about LoongArch yet.

lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

2623

Should this be || not &&?

[DavidSpickett]

lldb/test/Shell/ObjectFile/ELF/loongarch64-relocations.yaml

11

Please add a comment to explain briefly how this proves the relocations are being processed. As it is I don't see how the content of the data section proves that any work was done, besides us not crashing.

Or the other way around, if the relocations were not applied what would we see here?

[SixWeining]

lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

2623

Yes I think so. This should be an error in original code but not introduced this time. Do you mind I include the fix in current patch or in a separate one?

lldb/test/Shell/ObjectFile/ELF/loongarch64-relocations.yaml

11

No problem.

Actually I just add this test like what aarch64 and i386 did before. Let me simplify the test and make it more readable. Thanks.

[SixWeining]

Address @DavidSpickett's comments.

1. Fix the && issue.
2. Make the test more readable.

[DavidSpickett]

LGTM.

lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

2623

In this patch is fine.

lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

ObjectFileELF::ParseTrampolineSymbols(Symtab *symbol_table, user_id_t start_id,
   if (!rel_type)
     return 0;
 
   return ParsePLTRelocations(symbol_table, start_id, rel_type, &m_header,
                              rel_hdr, plt_hdr, sym_hdr, plt_section_sp,
                              rel_data, symtab_data, strtab_data);
 }
 
+static void ApplyELF64ABS64Relocation(Symtab *symtab, ELFRelocation &rel,
+                                      DataExtractor &debug_data,
+                                      Section *rel_section) {
+  Symbol *symbol = symtab->FindSymbolByID(ELFRelocation::RelocSymbol64(rel));
+  if (symbol) {
+    addr_t value = symbol->GetAddressRef().GetFileAddress();
+    DataBufferSP &data_buffer_sp = debug_data.GetSharedDataBuffer();
+    // ObjectFileELF creates a WritableDataBuffer in CreateInstance.
+    WritableDataBuffer *data_buffer =
+        llvm::cast<WritableDataBuffer>(data_buffer_sp.get());
+    uint64_t *dst = reinterpret_cast<uint64_t *>(
+        data_buffer->GetBytes() + rel_section->GetFileOffset() +
+        ELFRelocation::RelocOffset64(rel));
+    uint64_t val_offset = value + ELFRelocation::RelocAddend64(rel);
+    memcpy(dst, &val_offset, sizeof(uint64_t));
+  }
+}
+
+static void ApplyELF64ABS32Relocation(Symtab *symtab, ELFRelocation &rel,
+                                      DataExtractor &debug_data,
+                                      Section *rel_section, bool is_signed) {
+  Symbol *symbol = symtab->FindSymbolByID(ELFRelocation::RelocSymbol64(rel));
+  if (symbol) {
+    addr_t value = symbol->GetAddressRef().GetFileAddress();
+    value += ELFRelocation::RelocAddend32(rel);
+    if ((!is_signed && (value > UINT32_MAX)) ||
+        (is_signed &&
+         ((int64_t)value > INT32_MAX || (int64_t)value < INT32_MIN))) {
+      Log *log = GetLog(LLDBLog::Modules);
+      LLDB_LOGF(log, "Failed to apply debug info relocations");
+      return;
+    }
+    uint32_t truncated_addr = (value & 0xFFFFFFFF);
+    DataBufferSP &data_buffer_sp = debug_data.GetSharedDataBuffer();
+    // ObjectFileELF creates a WritableDataBuffer in CreateInstance.
+    WritableDataBuffer *data_buffer =
+        llvm::cast<WritableDataBuffer>(data_buffer_sp.get());
+    uint32_t *dst = reinterpret_cast<uint32_t *>(
+        data_buffer->GetBytes() + rel_section->GetFileOffset() +
+        ELFRelocation::RelocOffset32(rel));
+    memcpy(dst, &truncated_addr, sizeof(uint32_t));
+  }
+}
+
 unsigned ObjectFileELF::ApplyRelocations(
     Symtab *symtab, const ELFHeader *hdr, const ELFSectionHeader *rel_hdr,
     const ELFSectionHeader *symtab_hdr, const ELFSectionHeader *debug_hdr,
     DataExtractor &rel_data, DataExtractor &symtab_data,
     DataExtractor &debug_data, Section *rel_section) {
   ELFRelocation rel(rel_hdr->sh_type);
   lldb::addr_t offset = 0;
   const unsigned num_relocations = rel_hdr->sh_size / rel_hdr->sh_entsize;
if (hdr->Is32Bit()) {
       case R_386_PC32:
       default:
         GetModule()->ReportError("unsupported 32-bit relocation:"
                                  " .rel{0}[{1}], type {2}",
                                  rel_section->GetName().AsCString(), i,
                                  reloc_type(rel));
       }
     } else {
+      switch (hdr->e_machine) {
+      case llvm::ELF::EM_AARCH64:
         switch (reloc_type(rel)) {
         case R_AARCH64_ABS64:
-      case R_X86_64_64: {
-        symbol = symtab->FindSymbolByID(reloc_symbol(rel));
-        if (symbol) {
-          addr_t value = symbol->GetAddressRef().GetFileAddress();
-          DataBufferSP &data_buffer_sp = debug_data.GetSharedDataBuffer();
-          // ObjectFileELF creates a WritableDataBuffer in CreateInstance.
-          WritableDataBuffer *data_buffer =
-              llvm::cast<WritableDataBuffer>(data_buffer_sp.get());
-          uint64_t *dst = reinterpret_cast<uint64_t *>(
-              data_buffer->GetBytes() + rel_section->GetFileOffset() +
-              ELFRelocation::RelocOffset64(rel));
-          uint64_t val_offset = value + ELFRelocation::RelocAddend64(rel);
-          memcpy(dst, &val_offset, sizeof(uint64_t));
+          ApplyELF64ABS64Relocation(symtab, rel, debug_data, rel_section);
+          break;
+        case R_AARCH64_ABS32:
+          ApplyELF64ABS32Relocation(symtab, rel, debug_data, rel_section, true);
+          break;
+        default:
+          assert(false && "unexpected relocation type");
         }
         break;
+      case llvm::ELF::EM_LOONGARCH:
+        switch (reloc_type(rel)) {
+        case R_LARCH_64:
+          ApplyELF64ABS64Relocation(symtab, rel, debug_data, rel_section);
+          break;
+        case R_LARCH_32:
+          ApplyELF64ABS32Relocation(symtab, rel, debug_data, rel_section, true);
+          break;
+        default:
+          assert(false && "unexpected relocation type");
         }
+        break;
+      case llvm::ELF::EM_X86_64:
+        switch (reloc_type(rel)) {
+        case R_X86_64_64:
+          ApplyELF64ABS64Relocation(symtab, rel, debug_data, rel_section);
+          break;
         case R_X86_64_32:
-      case R_X86_64_32S:
-      case R_AARCH64_ABS32: {
-        symbol = symtab->FindSymbolByID(reloc_symbol(rel));
-        if (symbol) {
-          addr_t value = symbol->GetAddressRef().GetFileAddress();
-          value += ELFRelocation::RelocAddend32(rel);
-          if ((reloc_type(rel) == R_X86_64_32 && (value > UINT32_MAX)) ||
-              (reloc_type(rel) == R_X86_64_32S &&
-               ((int64_t)value > INT32_MAX && (int64_t)value < INT32_MIN)) ||
-              (reloc_type(rel) == R_AARCH64_ABS32 &&
-               ((int64_t)value > INT32_MAX && (int64_t)value < INT32_MIN))) {
-            Log *log = GetLog(LLDBLog::Modules);
-            LLDB_LOGF(log, "Failed to apply debug info relocations");
-            break;
-          }
-          uint32_t truncated_addr = (value & 0xFFFFFFFF);
-          DataBufferSP &data_buffer_sp = debug_data.GetSharedDataBuffer();
-          // ObjectFileELF creates a WritableDataBuffer in CreateInstance.
-          WritableDataBuffer *data_buffer =
-              llvm::cast<WritableDataBuffer>(data_buffer_sp.get());
-          uint32_t *dst = reinterpret_cast<uint32_t *>(
-              data_buffer->GetBytes() + rel_section->GetFileOffset() +
-              ELFRelocation::RelocOffset32(rel));
-          memcpy(dst, &truncated_addr, sizeof(uint32_t));
-        }
+          ApplyELF64ABS32Relocation(symtab, rel, debug_data, rel_section,
+                                    false);
+        case R_X86_64_32S:
+          ApplyELF64ABS32Relocation(symtab, rel, debug_data, rel_section, true);
           break;
-      }
         case R_X86_64_PC32:
         default:
           assert(false && "unexpected relocation type");
         }
+        break;
+      default:
+        assert(false && "unsupported machine");
+      }
     }
   }
 
   return 0;
 }
 
 unsigned ObjectFileELF::RelocateDebugSections(const ELFSectionHeader *rel_hdr,
                                               user_id_t rel_id,

lldb/test/Shell/ObjectFile/ELF/loongarch64-relocations.yaml

+# RUN: yaml2obj %s -o %t
+# RUN: lldb-test object-file -contents %t | FileCheck %s
+
+## Test that relocations are correctly applied to the .debug_info section on loongarch64.
+
+# CHECK:      Name: .debug_info
+# CHECK:      Data:  (
+## Before relocation:
+##                0000: 00000000 00000000 00000000
+## After relocation:
+# CHECK-NEXT:     0000: 34120000 78560000 00000000
+# CHECK-NEXT: )
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_LOONGARCH
+Sections:
+  - Name:            .debug_str
+    Type:            SHT_PROGBITS
+  - Name:            .debug_info
+    Type:            SHT_PROGBITS
+    Content:         000000000000000000000000
+  - Name:            .rela.debug_info
+    Type:            SHT_RELA
+    Info:            .debug_info
+    Relocations:
+      - Offset:          0x0000000000000000
+        Symbol:          .debug_str
+        Type:            R_LARCH_32
+        Addend:          0x1234
+      - Offset:          0x0000000000000004
+        Symbol:          .debug_str
+        Type:            R_LARCH_64
+        Addend:          0x5678
+Symbols:
+  - Name:            .debug_str
+    Type:            STT_SECTION
+    Section:         .debug_str
+  - Name:            .debug_info
+    Type:            STT_SECTION
+    Section:         .debug_info
+...