[Object] Add the method for checking if a section is a debug section

Different file formats have different naming style for the debug
sections. The method is implemented for ELF, COFF and Mach-O formats.

Differential Revision: https://reviews.llvm.org/D76276

llvm/include/llvm/Object/COFF.h

@@ -912,6 +912,7 @@ protected:
   bool isSectionData(DataRefImpl Sec) const override;
   bool isSectionBSS(DataRefImpl Sec) const override;
   bool isSectionVirtual(DataRefImpl Sec) const override;
+  bool isDebugSection(StringRef SectionName) const override;
   relocation_iterator section_rel_begin(DataRefImpl Sec) const override;
   relocation_iterator section_rel_end(DataRefImpl Sec) const override;
 

llvm/include/llvm/Object/ELFObjectFile.h

@@ -285,6 +285,7 @@ protected:
   bool isSectionVirtual(DataRefImpl Sec) const override;
   bool isBerkeleyText(DataRefImpl Sec) const override;
   bool isBerkeleyData(DataRefImpl Sec) const override;
+  bool isDebugSection(StringRef SectionName) const override;
   relocation_iterator section_rel_begin(DataRefImpl Sec) const override;
   relocation_iterator section_rel_end(DataRefImpl Sec) const override;
   std::vector<SectionRef> dynamic_relocation_sections() const override;
@@ -813,6 +814,12 @@ bool ELFObjectFile<ELFT>::isBerkeleyData(DataRefImpl Sec) const {
          EShdr->sh_flags & ELF::SHF_ALLOC;
 }
 
+template <class ELFT>
+bool ELFObjectFile<ELFT>::isDebugSection(StringRef SectionName) const {
+  return SectionName.startswith(".debug") ||
+         SectionName.startswith(".zdebug") || SectionName == ".gdb_index";
+}
+
 template <class ELFT>
 relocation_iterator
 ELFObjectFile<ELFT>::section_rel_begin(DataRefImpl Sec) const {

llvm/include/llvm/Object/MachO.h

@@ -309,6 +309,7 @@ public:
   bool isSectionBSS(DataRefImpl Sec) const override;
   bool isSectionVirtual(DataRefImpl Sec) const override;
   bool isSectionBitcode(DataRefImpl Sec) const override;
+  bool isDebugSection(StringRef SectionName) const override;
 
   /// When dsymutil generates the companion file, it strips all unnecessary
   /// sections (e.g. everything in the _TEXT segment) by omitting their body

llvm/include/llvm/Object/ObjectFile.h

@@ -123,6 +123,9 @@ public:
   /// contains data (e.g. PROGBITS), but is not text.
   bool isBerkeleyData() const;
 
+  /// Whether this section is a debug section.
+  bool isDebugSection(StringRef SectionName) const;
+
   bool containsSymbol(SymbolRef S) const;
 
   relocation_iterator relocation_begin() const;
@@ -272,6 +275,7 @@ protected:
   virtual bool isSectionStripped(DataRefImpl Sec) const;
   virtual bool isBerkeleyText(DataRefImpl Sec) const;
   virtual bool isBerkeleyData(DataRefImpl Sec) const;
+  virtual bool isDebugSection(StringRef SectionName) const;
   virtual relocation_iterator section_rel_begin(DataRefImpl Sec) const = 0;
   virtual relocation_iterator section_rel_end(DataRefImpl Sec) const = 0;
   virtual Expected<section_iterator> getRelocatedSection(DataRefImpl Sec) const;
@@ -495,6 +499,10 @@ inline bool SectionRef::isBerkeleyData() const {
   return OwningObject->isBerkeleyData(SectionPimpl);
 }
 
+inline bool SectionRef::isDebugSection(StringRef SectionName) const {
+  return OwningObject->isDebugSection(SectionName);
+}
+
 inline relocation_iterator SectionRef::relocation_begin() const {
   return OwningObject->section_rel_begin(SectionPimpl);
 }

llvm/lib/Object/COFFObjectFile.cpp

@@ -328,6 +328,12 @@ bool COFFObjectFile::isSectionBSS(DataRefImpl Ref) const {
   return (Sec->Characteristics & BssFlags) == BssFlags;
 }
 
+// The .debug sections are the only debug sections for COFF
+// (\see MCObjectFileInfo.cpp).
+bool COFFObjectFile::isDebugSection(StringRef SectionName) const {
+  return SectionName.startswith(".debug");
+}
+
 unsigned COFFObjectFile::getSectionID(SectionRef Sec) const {
   uintptr_t Offset =
       uintptr_t(Sec.getRawDataRefImpl().p) - uintptr_t(SectionTable);

llvm/lib/Object/MachOObjectFile.cpp

@@ -2030,6 +2030,11 @@ bool MachOObjectFile::isSectionBSS(DataRefImpl Sec) const {
           SectionType == MachO::S_GB_ZEROFILL);
 }
 
+bool MachOObjectFile::isDebugSection(StringRef SectionName) const {
+  return SectionName.startswith("__debug") ||
+         SectionName.startswith("__zdebug") || SectionName == "__gdb_index";
+}
+
 unsigned MachOObjectFile::getSectionID(SectionRef Sec) const {
   return Sec.getRawDataRefImpl().d.a;
 }

llvm/lib/Object/ObjectFile.cpp

@@ -91,6 +91,10 @@ bool ObjectFile::isBerkeleyData(DataRefImpl Sec) const {
   return isSectionData(Sec);
 }
 
+bool ObjectFile::isDebugSection(StringRef SectionName) const {
+  return false;
+}
+
 Expected<section_iterator>
 ObjectFile::getRelocatedSection(DataRefImpl Sec) const {
   return section_iterator(SectionRef(Sec, this));