[yaml2obj][COFF] Add support for extended relocation tables

[sdmitriev]

Summary

The tool does not correctly handle COFF sections with extended relocation tables (with IMAGE_SCN_LNK_NRELOC_OVFL bit set), this patch fixes this problem.

But I have cheated a bit in the test (to make it smaller) because extended relocation table is supposed to be used when the number of relocations exceeds 65534. Otherwise the test size would be pretty big.

[MaskRay]

llvm/lib/ObjectYAML/COFFEmitter.cpp

515

Be consistent: /*Type=*/

llvm/test/tools/yaml2obj/coff-xrelocs.yaml

2

A file-level comment about the purpose of the test. The mapping xrelocs -> extended relocation table is not very obvious.

Maybe it is time to place binary format specific tests in their own directories, and for this one, COFF/?

[sdmitriev]

Addressed review comments.

llvm/test/tools/yaml2obj/coff-xrelocs.yaml

2

A file-level comment about the purpose of the test. The mapping xrelocs -> extended relocation table is not very obvious.

Done.

Maybe it is time to place binary format specific tests in their own directories, and for this one, COFF/?

This should probably be done in separate commit.

[mstorsjo]

LGTM

[MaskRay]

llvm/test/tools/yaml2obj/coff-xrelocs.yaml

2

I have created https://reviews.llvm.org/D70264 to reorganize the tests.

llvm/lib/ObjectYAML/COFFEmitter.cpp

if (S.SectionData.binary_size() > 0) {
       S.Header.SizeOfRawData = S.SectionData.binary_size();
       if (CP.isPE())
         S.Header.SizeOfRawData =
             alignTo(S.Header.SizeOfRawData, CP.getFileAlignment());
       S.Header.PointerToRawData = CurrentSectionDataOffset;
       CurrentSectionDataOffset += S.Header.SizeOfRawData;
       if (!S.Relocations.empty()) {
         S.Header.PointerToRelocations = CurrentSectionDataOffset;
+        if (S.Header.Characteristics & COFF::IMAGE_SCN_LNK_NRELOC_OVFL) {
+          S.Header.NumberOfRelocations = 0xffff;
+          CurrentSectionDataOffset += COFF::RelocationSize;
+        } else
           S.Header.NumberOfRelocations = S.Relocations.size();
-        CurrentSectionDataOffset +=
-            S.Header.NumberOfRelocations * COFF::RelocationSize;
+        CurrentSectionDataOffset += S.Relocations.size() * COFF::RelocationSize;
       }
     } else {
       // Leave SizeOfRawData unaltered. For .bss sections in object files, it
       // carries the section size.
       S.Header.PointerToRawData = 0;
     }
   }
 
static bool writeCOFF(COFFParser &CP, raw_ostream &OS) {
   for (const COFFYAML::Section &S : CP.Obj.Sections) {
     if (S.Header.SizeOfRawData == 0 || S.Header.PointerToRawData == 0)
       continue;
     assert(S.Header.PointerToRawData >= OS.tell());
     OS.write_zeros(S.Header.PointerToRawData - OS.tell());
     S.SectionData.writeAsBinary(OS);
     assert(S.Header.SizeOfRawData >= S.SectionData.binary_size());
     OS.write_zeros(S.Header.SizeOfRawData - S.SectionData.binary_size());
+    if (S.Header.Characteristics & COFF::IMAGE_SCN_LNK_NRELOC_OVFL)
+      OS << binary_le<uint32_t>(/*VirtualAddress=*/ S.Relocations.size() + 1)
+         << binary_le<uint32_t>(/*SymbolTableIndex=*/ 0)
+         << binary_le<uint16_t>(/*Type=*/ 0);
     for (const COFFYAML::Relocation &R : S.Relocations) {
       uint32_t SymbolTableIndex;
       if (R.SymbolTableIndex) {
         if (!R.SymbolName.empty())
           WithColor::error()
               << "Both SymbolName and SymbolTableIndex specified\n";
         SymbolTableIndex = *R.SymbolTableIndex;
       } else {

llvm/test/tools/yaml2obj/coff-xrelocs.yaml

+## This test checks that yaml2obj correctly handles COFF sections with
+## extended relocation tables (IMAGE_SCN_LNK_NRELOC_OVFL).
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-readobj --sections --relocations %t | FileCheck %s --check-prefix=CHECK-OBJ
+# RUN: obj2yaml %t | FileCheck %s --check-prefix=CHECK-YAML
+
+# CHECK-OBJ:      Sections [
+# CHECK-OBJ-NEXT:   Section {
+# CHECK-OBJ-NEXT:     Number: 1
+# CHECK-OBJ-NEXT:     Name: .data
+# CHECK-OBJ:          RawDataSize: 16
+# CHECK-OBJ:          RelocationCount: 65535
+# CHECK-OBJ:          Characteristics [
+# CHECK-OBJ-NEXT:       IMAGE_SCN_ALIGN_16BYTES
+# CHECK-OBJ-NEXT:       IMAGE_SCN_CNT_INITIALIZED_DATA
+# CHECK-OBJ-NEXT:       IMAGE_SCN_LNK_NRELOC_OVFL
+# CHECK-OBJ-NEXT:       IMAGE_SCN_MEM_READ
+# CHECK-OBJ-NEXT:     ]
+# CHECK-OBJ-NEXT:   }
+# CHECK-OBJ-NEXT: ]
+# CHECK-OBJ-NEXT: Relocations [
+# CHECK-OBJ-NEXT:   Section (1) .data {
+# CHECK-OBJ-NEXT:     0x0 IMAGE_REL_AMD64_ADDR64 foo (0)
+# CHECK-OBJ-NEXT:     0x8 IMAGE_REL_AMD64_ADDR64 bar (1)
+# CHECK-OBJ-NEXT:   }
+# CHECK-OBJ-NEXT: ]
+
+# CHECK-YAML:      sections:
+# CHECK-YAML-NEXT:   - Name:            .data
+# CHECK-YAML-NEXT:     Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_LNK_NRELOC_OVFL, IMAGE_SCN_MEM_READ ]
+# CHECK-YAML-NEXT:     Alignment:       16
+# CHECK-YAML-NEXT:     SectionData:     '00000000000000000000000000000000'
+# CHECK-YAML-NEXT:     Relocations:
+# CHECK-YAML-NEXT:       - VirtualAddress:  0
+# CHECK-YAML-NEXT:         SymbolName:      foo
+# CHECK-YAML-NEXT:         Type:            IMAGE_REL_AMD64_ADDR64
+# CHECK-YAML-NEXT:       - VirtualAddress:  8
+# CHECK-YAML-NEXT:         SymbolName:      bar
+# CHECK-YAML-NEXT:         Type:            IMAGE_REL_AMD64_ADDR64
+# CHECK-YAML-NEXT: symbols:
+
+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_AMD64
+  Characteristics: [  ]
+sections:
+  - Name:            .data
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_LNK_NRELOC_OVFL, IMAGE_SCN_MEM_READ ]
+    Alignment:       16
+    SectionData:     '00000000000000000000000000000000'
+    Relocations:
+      - VirtualAddress:  0
+        SymbolName:      foo
+        Type:            IMAGE_REL_AMD64_ADDR64
+      - VirtualAddress:  8
+        SymbolName:      bar
+        Type:            IMAGE_REL_AMD64_ADDR64
+symbols:
+  - Name:            foo
+    Value:           0
+    SectionNumber:   0
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            bar
+    Value:           0
+    SectionNumber:   0
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...