[llvm-objcopy][COFF] Add support for extended relocation tables

Summary: This patch adds support for COFF objects with extended relocation tables to the llvm-objcopy tool.

Reviewers: jhenderson, MaskRay, mstorsjo, alexshap, rupprecht

Reviewed By: mstorsjo

Subscribers: jakehehrlich, abrachet, seiya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70205

2 files changed, 20 insertions, 6 deletions

diff --git a/llvm/tools/llvm-objcopy/COFF/Reader.cpp b/llvm/tools/llvm-objcopy/COFF/Reader.cpp
index 2fcec0057c0..7be9cce2be3 100644
--- a/llvm/tools/llvm-objcopy/COFF/Reader.cpp
+++ b/llvm/tools/llvm-objcopy/COFF/Reader.cpp
@@ -63,6 +63,7 @@ Error COFFReader::readSections(Object &Obj) const {
     Sections.push_back(Section());
     Section &S = Sections.back();
     S.Header = *Sec;
+    S.Header.Characteristics &= ~COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
     ArrayRef<uint8_t> Contents;
     if (Error E = COFFObj.getSectionContents(Sec, Contents))
       return E;
@@ -74,9 +75,6 @@ Error COFFReader::readSections(Object &Obj) const {
       S.Name = *NameOrErr;
     else
       return NameOrErr.takeError();
-    if (Sec->hasExtendedRelocations())
-      return createStringError(object_error::parse_failed,
-                               "extended relocations not supported yet");
   }
   Obj.addSections(Sections);
   return Error::success();
diff --git a/llvm/tools/llvm-objcopy/COFF/Writer.cpp b/llvm/tools/llvm-objcopy/COFF/Writer.cpp
index 6db37435fd9..e35e0474a36 100644
--- a/llvm/tools/llvm-objcopy/COFF/Writer.cpp
+++ b/llvm/tools/llvm-objcopy/COFF/Writer.cpp
@@ -97,9 +97,16 @@ void COFFWriter::layoutSections() {
       S.Header.PointerToRawData = FileSize;
     FileSize += S.Header.SizeOfRawData; // For executables, this is already
                                         // aligned to FileAlignment.
-    S.Header.NumberOfRelocations = S.Relocs.size();
-    S.Header.PointerToRelocations =
-        S.Header.NumberOfRelocations > 0 ? FileSize : 0;
+    if (S.Relocs.size() >= 0xffff) {
+      S.Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
+      S.Header.NumberOfRelocations = 0xffff;
+      S.Header.PointerToRelocations = FileSize;
+      FileSize += sizeof(coff_relocation);
+    } else {
+      S.Header.NumberOfRelocations = S.Relocs.size();
+      S.Header.PointerToRelocations = S.Relocs.size() ? FileSize : 0;
+    }
+
     FileSize += S.Relocs.size() * sizeof(coff_relocation);
     FileSize = alignTo(FileSize, FileAlignment);
 
@@ -307,6 +314,15 @@ void COFFWriter::writeSections() {
              S.Header.SizeOfRawData - Contents.size());
 
     Ptr += S.Header.SizeOfRawData;
+
+    if (S.Relocs.size() >= 0xffff) {
+      object::coff_relocation R;
+      R.VirtualAddress = S.Relocs.size() + 1;
+      R.SymbolTableIndex = 0;
+      R.Type = 0;
+      memcpy(Ptr, &R, sizeof(R));
+      Ptr += sizeof(R);
+    }
     for (const auto &R : S.Relocs) {
       memcpy(Ptr, &R.Reloc, sizeof(R.Reloc));
       Ptr += sizeof(R.Reloc);