[PATCH] D70205: [llvm-objcopy][COFF] Add support for extended relocation tables

[Sergey Dmitriev via Phabricator via llvm-commits]

sdmitriev created this revision.
sdmitriev added reviewers: jhenderson, MaskRay, mstorsjo.
Herald added subscribers: llvm-commits, seiya, abrachet, jakehehrlich.
Herald added a reviewer: alexshap.
Herald added a reviewer: rupprecht.
Herald added a project: LLVM.

This patch adds support for COFF objects with extended relocation tables to the llvm-objcopy tool.
Object file with extended relocations for the LIT test was taken from D3139 <https://reviews.llvm.org/D3139>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70205

Files:
  llvm/test/tools/llvm-objcopy/COFF/Inputs/many-relocs.obj-i386
  llvm/test/tools/llvm-objcopy/COFF/add-section.test
  llvm/tools/llvm-objcopy/COFF/Reader.cpp
  llvm/tools/llvm-objcopy/COFF/Writer.cpp


Index: llvm/tools/llvm-objcopy/COFF/Writer.cpp
===================================================================
--- llvm/tools/llvm-objcopy/COFF/Writer.cpp
+++ llvm/tools/llvm-objcopy/COFF/Writer.cpp
@@ -97,9 +97,16 @@
       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 @@
              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);
Index: llvm/tools/llvm-objcopy/COFF/Reader.cpp
===================================================================
--- llvm/tools/llvm-objcopy/COFF/Reader.cpp
+++ llvm/tools/llvm-objcopy/COFF/Reader.cpp
@@ -63,6 +63,7 @@
     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 @@
       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();
Index: llvm/test/tools/llvm-objcopy/COFF/add-section.test
===================================================================
--- llvm/test/tools/llvm-objcopy/COFF/add-section.test
+++ llvm/test/tools/llvm-objcopy/COFF/add-section.test
@@ -32,6 +32,23 @@
 # CHECK-ADD-EMPTY-NAME-NEXT:  0000: {{.+}}|DEADBEEF{{.+}}|
 # CHECK-ADD-EMPTY-NAME-NEXT: )
 
+## Test that llvm-objcopy can add a section to an object with extended
+## relocations.
+# RUN: llvm-objcopy --add-section=.test.section=%t.sec %p/Inputs/many-relocs.obj-i386 %t1.extended.relocs
+# RUN: llvm-readobj --file-headers --sections --section-data %t1.extended.relocs | FileCheck %s --check-prefixes=CHECK-EXTENDED-RELOCS
+
+# CHECK-EXTENDED-RELOCS:      SectionCount: 2
+# CHECK-EXTENDED-RELOCS:      Name: .text
+# CHECK-EXTENDED-RELOCS:      RelocationCount: 10
+# CHECK-EXTENDED-RELOCS:      Name: .test.section
+# CHECK-EXTENDED-RELOCS:      Characteristics [
+# CHECK-EXTENDED-RELOCS-NEXT:   IMAGE_SCN_ALIGN_1BYTES
+# CHECK-EXTENDED-RELOCS-NEXT:   IMAGE_SCN_CNT_INITIALIZED_DATA
+# CHECK-EXTENDED-RELOCS-NEXT: ]
+# CHECK-EXTENDED-RELOCS:      SectionData (
+# CHECK-EXTENDED-RELOCS-NEXT:  0000: {{.+}}|DEADBEEF{{.+}}|
+# CHECK-EXTENDED-RELOCS-NEXT: )
+
 ## Test that llvm-objcopy produces an error if the file with section contents
 ## to be added does not exist.
 # RUN: not llvm-objcopy --add-section=.another.section=%t2 %t %t3 2>&1 | FileCheck -DFILE1=%t -DFILE2=%t2 %s --check-prefixes=ERR1


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