[lldb][AIX] Support for XCOFF Sections

[DhruvSrivastavaX]

This PR is in reference to porting LLDB on AIX.

Link to discussions on llvm discourse and github:

1. https://discourse.llvm.org/t/port-lldb-to-ibm-aix/80640
2. Extending LLDB to work on AIX #101657
   The complete changes for porting are present in this draft PR:
   Extending LLDB to work on AIX #102601

Incremental PR on ObjectFileXCOFF.cpp
This PR is intended to handle XCOFF sections.

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Dhruv Srivastava (DhruvSrivastavaX)

Changes

This PR is in reference to porting LLDB on AIX.

Link to discussions on llvm discourse and github:

1. https://discourse.llvm.org/t/port-lldb-to-ibm-aix/80640
2. Extending LLDB to work on AIX #101657
   The complete changes for porting are present in this draft PR:
   Extending LLDB to work on AIX #102601

Incremental PR on ObjectFileXCOFF.cpp
This PR is intended to handle XCOFF sections.

---

Full diff: https://github.com/llvm/llvm-project/pull/131304.diff

1 Files Affected:

• (modified) lldb/source/Plugins/ObjectFile/XCOFF/ObjectFileXCOFF.cpp (+114-39)

diff --git a/lldb/source/Plugins/ObjectFile/XCOFF/ObjectFileXCOFF.cpp b/lldb/source/Plugins/ObjectFile/XCOFF/ObjectFileXCOFF.cpp
index b54d43c5dd737..0dd9126468923 100644
--- a/lldb/source/Plugins/ObjectFile/XCOFF/ObjectFileXCOFF.cpp
+++ b/lldb/source/Plugins/ObjectFile/XCOFF/ObjectFileXCOFF.cpp
@@ -190,50 +190,125 @@ void ObjectFileXCOFF::ParseSymtab(Symtab &lldb_symtab) {}
 
 bool ObjectFileXCOFF::IsStripped() { return false; }
 
-void ObjectFileXCOFF::CreateSections(SectionList &unified_section_list) {}
-
-void ObjectFileXCOFF::Dump(Stream *s) {}
-
-ArchSpec ObjectFileXCOFF::GetArchitecture() {
-  ArchSpec arch_spec =
-      ArchSpec(eArchTypeXCOFF, XCOFF::TCPU_PPC64, LLDB_INVALID_CPUTYPE);
-  return arch_spec;
+void ObjectFileXCOFF::CreateSections(SectionList &unified_section_list) {
+
+  if (m_sections_up)
+    return;
+  m_sections_up = std::make_unique<SectionList>();
+  ModuleSP module_sp(GetModule());
+  if (module_sp) {
+    std::lock_guard<std::recursive_mutex> guard(module_sp->GetMutex());
+
+    ModuleSP module_sp(GetModule());
+    for (auto sIdx = m_binary->section_begin(); sIdx != m_binary->section_end();
+         ++sIdx) {
+      llvm::Expected<llvm::StringRef> name =
+          m_binary->getSectionName(sIdx->getRawDataRefImpl());
+      if (!name) {
+        llvm::Error err = name.takeError();
+      }
+      llvm::StringRef sect_name = *name;
+      ConstString const_sect_name(sect_name);
+      int sect_index = sIdx->getIndex(), idx = 1;
+      llvm::Expected<llvm::object::DataRefImpl> section =
+          m_binary->getSectionByNum(sect_index);
+      if (!section) {
+        llvm::Error err = section.takeError();
+      }
+      llvm::object::DataRefImpl dataref = section.get();
+      const llvm::object::XCOFFSectionHeader64 *sectionPtr =
+          reinterpret_cast<const llvm::object::XCOFFSectionHeader64 *>(
+              dataref.p);
+
+      SectionType section_type = lldb::eSectionTypeOther;
+      if (sectionPtr->Flags & XCOFF::STYP_TEXT)
+        section_type = eSectionTypeCode;
+      if (sectionPtr->Flags & XCOFF::STYP_DATA)
+        section_type = eSectionTypeData;
+      if (sectionPtr->Flags & XCOFF::STYP_BSS)
+        section_type = eSectionTypeZeroFill;
+      if (sectionPtr->Flags & XCOFF::STYP_DWARF) {
+        SectionType section_type =
+            llvm::StringSwitch<SectionType>(sect_name)
+                .Case(".dwinfo", eSectionTypeDWARFDebugInfo)
+                .Case(".dwline", eSectionTypeDWARFDebugLine)
+                .Case(".dwabrev", eSectionTypeDWARFDebugAbbrev)
+                .Default(eSectionTypeInvalid);
+
+        if (section_type == eSectionTypeInvalid)
+          section_type = lldb::eSectionTypeOther;
+      }
+      SectionSP section_sp(new Section(
+          module_sp,       // Module to which this section belongs
+          this,            // Object file to which this section belongs
+          idx++,           // Section ID is the 1 based section index.
+          const_sect_name, // Name of this section
+          section_type,
+          sectionPtr->VirtualAddress,      // File VM address == addresses as
+                                           // they are found in the object file
+          sectionPtr->SectionSize,         // VM size in bytes of this section
+          sectionPtr->FileOffsetToRawData, // Offset to the data for this
+                                           // section in the file
+          sectionPtr->SectionSize, // Size in bytes of this section as found in
+                                   // the file
+          0,                       // FIXME: alignment
+          sectionPtr->Flags));     // Flags for this section
+
+      uint32_t permissions = 0;
+      permissions |= ePermissionsReadable;
+      if (sectionPtr->Flags & (XCOFF::STYP_DATA | XCOFF::STYP_BSS))
+        permissions |= ePermissionsWritable;
+      if (sectionPtr->Flags & XCOFF::STYP_TEXT)
+        permissions |= ePermissionsExecutable;
+      section_sp->SetPermissions(permissions);
+
+      m_sections_up->AddSection(section_sp);
+      unified_section_list.AddSection(section_sp);
+    }
+  }
 }
+  void ObjectFileXCOFF::Dump(Stream * s) {}
 
-UUID ObjectFileXCOFF::GetUUID() { return UUID(); }
+  ArchSpec ObjectFileXCOFF::GetArchitecture() {
+    ArchSpec arch_spec =
+        ArchSpec(eArchTypeXCOFF, XCOFF::TCPU_PPC64, LLDB_INVALID_CPUTYPE);
+    return arch_spec;
+  }
 
-uint32_t ObjectFileXCOFF::GetDependentModules(FileSpecList &files) { return 0; }
+  UUID ObjectFileXCOFF::GetUUID() { return UUID(); }
 
-ObjectFile::Type ObjectFileXCOFF::CalculateType() {
-  if (m_binary->fileHeader64()->Flags & XCOFF::F_EXEC)
-    return eTypeExecutable;
-  else if (m_binary->fileHeader64()->Flags & XCOFF::F_SHROBJ)
-    return eTypeSharedLibrary;
-  return eTypeUnknown;
-}
+  uint32_t ObjectFileXCOFF::GetDependentModules(FileSpecList & files) {
+    return 0;
+  }
 
-ObjectFile::Strata ObjectFileXCOFF::CalculateStrata() { return eStrataUnknown; }
+  ObjectFile::Type ObjectFileXCOFF::CalculateType() {
+    if (m_binary->fileHeader64()->Flags & XCOFF::F_EXEC)
+      return eTypeExecutable;
+    else if (m_binary->fileHeader64()->Flags & XCOFF::F_SHROBJ)
+      return eTypeSharedLibrary;
+    return eTypeUnknown;
+  }
 
-lldb::WritableDataBufferSP
-ObjectFileXCOFF::MapFileDataWritable(const FileSpec &file, uint64_t Size,
-                                     uint64_t Offset) {
-  return FileSystem::Instance().CreateWritableDataBuffer(file.GetPath(), Size,
-                                                         Offset);
-}
+  ObjectFile::Strata ObjectFileXCOFF::CalculateStrata() {
+    return eStrataUnknown;
+  }
 
-ObjectFileXCOFF::ObjectFileXCOFF(const lldb::ModuleSP &module_sp,
-                                 DataBufferSP data_sp,
-                                 lldb::offset_t data_offset,
-                                 const FileSpec *file,
-                                 lldb::offset_t file_offset,
-                                 lldb::offset_t length)
-    : ObjectFile(module_sp, file, file_offset, length, data_sp, data_offset) {
-  if (file)
-    m_file = *file;
-}
+  lldb::WritableDataBufferSP ObjectFileXCOFF::MapFileDataWritable(
+      const FileSpec &file, uint64_t Size, uint64_t Offset) {
+    return FileSystem::Instance().CreateWritableDataBuffer(file.GetPath(), Size,
+                                                           Offset);
+  }
+
+  ObjectFileXCOFF::ObjectFileXCOFF(
+      const lldb::ModuleSP &module_sp, DataBufferSP data_sp,
+      lldb::offset_t data_offset, const FileSpec *file,
+      lldb::offset_t file_offset, lldb::offset_t length)
+      : ObjectFile(module_sp, file, file_offset, length, data_sp, data_offset) {
+    if (file)
+      m_file = *file;
+  }
 
-ObjectFileXCOFF::ObjectFileXCOFF(const lldb::ModuleSP &module_sp,
-                                 DataBufferSP header_data_sp,
-                                 const lldb::ProcessSP &process_sp,
-                                 addr_t header_addr)
-    : ObjectFile(module_sp, process_sp, header_addr, header_data_sp) {}
+  ObjectFileXCOFF::ObjectFileXCOFF(
+      const lldb::ModuleSP &module_sp, DataBufferSP header_data_sp,
+      const lldb::ProcessSP &process_sp, addr_t header_addr)
+      : ObjectFile(module_sp, process_sp, header_addr, header_data_sp) {}

[DhruvSrivastavaX]

Hi, @labath @DavidSpickett,
Resuming the conversation on XCOFF support. I have added support for reading XCOFF sections using existing LLVM interfaces. I know there are gaps, so please let me know your thoughts.

I'll modify my test files accordingly as well

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[DhruvSrivastavaX]

Hi @labath @DavidSpickett,
So please let me know if I should add more apis in this PR or this much granularity is enough.
Also, we are working on an overall 32-bit implementation as well for AIX, so I am thinking of extending the xcoff for the 32 bit as well as it should not take much additional effort.
What are your thoughts?

[labath]

I think the granularity is fine. You should add/modify a test to check that the sections are being parsed correctly. (if there's something missing for that to work, feel free to add it).

I don't have an issue with adding support for 32-bit. I think it's up to you and whether you want to support it. Since llvm::XCOFFObjectFile has separate APIs for accessing 32- and 64-bit versions of the file, probably the easiest way to achieve that is to make any code which depends on that be a template function, which can them be instantiated for the right bitness.

[DhruvSrivastavaX]

Sure, Thanks.
I have modified my test case for this one.
Please provide your review @labath