DWZ 01/07: Support reading section ".gnu_debugaltlink"

[jankratochvil]

Summary

All DWZ patches are also applied in: git clone -b dwz git://git.jankratochvil.net/lldb

[clayborg]

Just move the eSectionTypeDWARFGNUDebugAltLink enumerator to the end of the enum and this is good to go.

include/lldb/lldb-enumerations.h

647

Since this enumeration is in the public API, it should be added to the end of the enum. Anyone that builds a new liblldb.so and then uses it with an binary compiled before could run into issues. But I noticed eSectionTypeDWARFDebugCuIndex was added in the middle in August, but we need to avoid these kinds of API issues, so lets add this to the end just to be safe.

[jankratochvil]

It is now reworked without FileOffset and the remapping to unique DIE offsets for each DW_TAG_partial_unit inclusion by DW_TAG_imported_unit, as discussed in: https://lists.llvm.org/pipermail/lldb-commits/Week-of-Mon-20180409/040324.html

[labath]

Could you add a "section type" line in the dumpModules in lldb-test.cpp. Then we can write a test for this. (not that this is a extremely dangerous change, but it seems a shame not to test it when it is so easy).

[jankratochvil]

Implemented that section type line in the dumpModules in lldb-test.cpp.

[labath]

Thanks, that's great, but I don't see you using that functionality to test the debug-alt-link classification (I guess I wasn't clear about that, but that is the reason why I asked you to add it). Could you add a test with the new section as well?

[jankratochvil]

Added lit/Modules/dwarf-gnu-debugaltlink.yaml. I do not see its test success anywhere but when I make it fail I see its failure in make check-lldb stdout/stderr. Curiously its simulated failure does not appear in make check-lit.

[labath]

Awesome, thanks. I think we can get this one out of the way.

In D40468#1080136, @jankratochvil wrote:

Added lit/Modules/dwarf-gnu-debugaltlink.yaml. I do not see its test success anywhere but when I make it fail I see its failure in make check-lldb stdout/stderr.

That's supposed to happen. To see passing tests you need to run lit in the verbose mode.

Curiously its simulated failure does not appear in make check-lit.

check-lit is a lit-selftest. This test should not be run as a part of that. Did you perhaps mean check-lldb-lit (which should probably be removed because it's now practically an alias for check-lldb)?

[jankratochvil]

In D40468#1080751, @labath wrote:

Awesome, thanks. I think we can get this one out of the way.

Thanks, I will check it in next days.

check-lit is a lit-selftest. This test should not be run as a part of that. Did you perhaps mean check-lldb-lit (which should probably be removed because it's now practically an alias for check-lldb)?

Yes, I was wrongly running check-lit instead of check-lldb-lit, thanks for the correction.

include/lldb/lldb-enumerations.h

enum SectionType {
   eSectionTypeDWARFDebugPubTypes,
   eSectionTypeDWARFDebugRanges,
   eSectionTypeDWARFDebugStr,
   eSectionTypeDWARFDebugStrOffsets,
   eSectionTypeDWARFAppleNames,
   eSectionTypeDWARFAppleTypes,
   eSectionTypeDWARFAppleNamespaces,
   eSectionTypeDWARFAppleObjC,
+  eSectionTypeDWARFGNUDebugAltLink,
   eSectionTypeELFSymbolTable,       // Elf SHT_SYMTAB section
   eSectionTypeELFDynamicSymbols,    // Elf SHT_DYNSYM section
   eSectionTypeELFRelocationEntries, // Elf SHT_REL or SHT_REL section
   eSectionTypeELFDynamicLinkInfo,   // Elf SHT_DYNAMIC section
   eSectionTypeEHFrame,
   eSectionTypeARMexidx,
   eSectionTypeARMextab,
   eSectionTypeCompactUnwind, // compact unwind section in Mach-O,

source/Core/Section.cpp

static const char *GetSectionTypeAsCString(lldb::SectionType sect_type) {
   case eSectionTypeDWARFAppleNames:
     return "apple-names";
   case eSectionTypeDWARFAppleTypes:
     return "apple-types";
   case eSectionTypeDWARFAppleNamespaces:
     return "apple-namespaces";
   case eSectionTypeDWARFAppleObjC:
     return "apple-objc";
+  case eSectionTypeDWARFGNUDebugAltLink:
+    return "dwarf-gnu-debugaltlink";
   case eSectionTypeEHFrame:
     return "eh-frame";
   case eSectionTypeARMexidx:
     return "ARM.exidx";
   case eSectionTypeARMextab:
     return "ARM.extab";
   case eSectionTypeCompactUnwind:
     return "compact-unwind";

source/Expression/IRExecutionUnit.cpp

bool IRExecutionUnit::CommitOneAllocation(lldb::ProcessSP &process_sp,
   case lldb::eSectionTypeDWARFDebugPubTypes:
   case lldb::eSectionTypeDWARFDebugRanges:
   case lldb::eSectionTypeDWARFDebugStr:
   case lldb::eSectionTypeDWARFDebugStrOffsets:
   case lldb::eSectionTypeDWARFAppleNames:
   case lldb::eSectionTypeDWARFAppleTypes:
   case lldb::eSectionTypeDWARFAppleNamespaces:
   case lldb::eSectionTypeDWARFAppleObjC:
+  case lldb::eSectionTypeDWARFGNUDebugAltLink:
     error.Clear();
     break;
   default:
     const bool zero_memory = false;
     record.m_process_address =
         Malloc(record.m_size, record.m_alignment, record.m_permissions,
                eAllocationPolicyProcessOnly, zero_memory, error);
     break;

source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

for (SectionHeaderCollIter I = m_section_headers.begin();
       static ConstString g_sect_name_dwarf_debug_loc_dwo(".debug_loc.dwo");
       static ConstString g_sect_name_dwarf_debug_str_dwo(".debug_str.dwo");
       static ConstString g_sect_name_dwarf_debug_str_offsets_dwo(
           ".debug_str_offsets.dwo");
       static ConstString g_sect_name_eh_frame(".eh_frame");
       static ConstString g_sect_name_arm_exidx(".ARM.exidx");
       static ConstString g_sect_name_arm_extab(".ARM.extab");
       static ConstString g_sect_name_go_symtab(".gosymtab");
+      static ConstString g_sect_name_dwarf_gnu_debugaltlink(".gnu_debugaltlink");
 
       SectionType sect_type = eSectionTypeOther;
 
       bool is_thread_specific = false;
 
       if (name == g_sect_name_text)
         sect_type = eSectionTypeCode;
       else if (name == g_sect_name_data)
for (SectionHeaderCollIter I = m_section_headers.begin();
       else if (name == g_sect_name_eh_frame)
         sect_type = eSectionTypeEHFrame;
       else if (name == g_sect_name_arm_exidx)
         sect_type = eSectionTypeARMexidx;
       else if (name == g_sect_name_arm_extab)
         sect_type = eSectionTypeARMextab;
       else if (name == g_sect_name_go_symtab)
         sect_type = eSectionTypeGoSymtab;
+      else if (name == g_sect_name_dwarf_gnu_debugaltlink)
+        sect_type = eSectionTypeDWARFGNUDebugAltLink;
 
       const uint32_t permissions =
           ((header.sh_flags & SHF_ALLOC) ? ePermissionsReadable : 0u) |
           ((header.sh_flags & SHF_WRITE) ? ePermissionsWritable : 0u) |
           ((header.sh_flags & SHF_EXECINSTR) ? ePermissionsExecutable : 0u);
       switch (header.sh_type) {
       case SHT_SYMTAB:
         assert(sect_type == eSectionTypeOther);

source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp

if (symbol) {
           case eSectionTypeDWARFDebugPubTypes:
           case eSectionTypeDWARFDebugRanges:
           case eSectionTypeDWARFDebugStr:
           case eSectionTypeDWARFDebugStrOffsets:
           case eSectionTypeDWARFAppleNames:
           case eSectionTypeDWARFAppleTypes:
           case eSectionTypeDWARFAppleNamespaces:
           case eSectionTypeDWARFAppleObjC:
+          case eSectionTypeDWARFGNUDebugAltLink:
             return eAddressClassDebug;
 
           case eSectionTypeEHFrame:
           case eSectionTypeARMexidx:
           case eSectionTypeARMextab:
           case eSectionTypeCompactUnwind:
             return eAddressClassRuntime;
 

source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h

public:
   const lldb_private::DWARFDataExtractor &get_debug_loc_data();
   const lldb_private::DWARFDataExtractor &get_debug_ranges_data();
   const lldb_private::DWARFDataExtractor &get_debug_str_data();
   const lldb_private::DWARFDataExtractor &get_debug_str_offsets_data();
   const lldb_private::DWARFDataExtractor &get_apple_names_data();
   const lldb_private::DWARFDataExtractor &get_apple_types_data();
   const lldb_private::DWARFDataExtractor &get_apple_namespaces_data();
   const lldb_private::DWARFDataExtractor &get_apple_objc_data();
+  const lldb_private::DWARFDataExtractor &get_gnu_debugaltlink();
 
   DWARFDebugAbbrev *DebugAbbrev();
 
   const DWARFDebugAbbrev *DebugAbbrev() const;
 
   DWARFDebugInfo *DebugInfo();
 
   const DWARFDebugInfo *DebugInfo() const;
protected:
   DWARFDataSegment m_data_debug_loc;
   DWARFDataSegment m_data_debug_ranges;
   DWARFDataSegment m_data_debug_str;
   DWARFDataSegment m_data_debug_str_offsets;
   DWARFDataSegment m_data_apple_names;
   DWARFDataSegment m_data_apple_types;
   DWARFDataSegment m_data_apple_namespaces;
   DWARFDataSegment m_data_apple_objc;
+  DWARFDataSegment m_data_gnu_debugaltlink;
 
   // The unique pointer items below are generated on demand if and when someone
   // accesses
   // them through a non const version of this class.
   std::unique_ptr<DWARFDebugAbbrev> m_abbr;
   std::unique_ptr<DWARFDebugInfo> m_info;
   std::unique_ptr<DWARFDebugLine> m_line;
   std::unique_ptr<DWARFMappedHash::MemoryTable> m_apple_names_ap;

source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

const DWARFDataExtractor &SymbolFileDWARF::get_apple_namespaces_data() {
   return GetCachedSectionData(eSectionTypeDWARFAppleNamespaces,
                               m_data_apple_namespaces);
 }
 
 const DWARFDataExtractor &SymbolFileDWARF::get_apple_objc_data() {
   return GetCachedSectionData(eSectionTypeDWARFAppleObjC, m_data_apple_objc);
 }
 
+const DWARFDataExtractor &SymbolFileDWARF::get_gnu_debugaltlink() {
+  return GetCachedSectionData(eSectionTypeDWARFGNUDebugAltLink,
+                              m_data_gnu_debugaltlink);
+}
+
 DWARFDebugAbbrev *SymbolFileDWARF::DebugAbbrev() {
   if (m_abbr.get() == NULL) {
     const DWARFDataExtractor &debug_abbrev_data = get_debug_abbrev_data();
     if (debug_abbrev_data.GetByteSize() > 0) {
       m_abbr.reset(new DWARFDebugAbbrev());
       if (m_abbr.get())
         m_abbr->Parse(debug_abbrev_data);
     }

source/Plugins/SymbolVendor/ELF/SymbolVendorELF.cpp

if (dsym_fspec) {
           static const SectionType g_sections[] = {
               eSectionTypeDWARFDebugAbbrev,   eSectionTypeDWARFDebugAddr,
               eSectionTypeDWARFDebugAranges,  eSectionTypeDWARFDebugCuIndex,
               eSectionTypeDWARFDebugFrame,    eSectionTypeDWARFDebugInfo,
               eSectionTypeDWARFDebugLine,     eSectionTypeDWARFDebugLoc,
               eSectionTypeDWARFDebugMacInfo,  eSectionTypeDWARFDebugPubNames,
               eSectionTypeDWARFDebugPubTypes, eSectionTypeDWARFDebugRanges,
               eSectionTypeDWARFDebugStr,      eSectionTypeDWARFDebugStrOffsets,
-              eSectionTypeELFSymbolTable,
+              eSectionTypeELFSymbolTable,     eSectionTypeDWARFGNUDebugAltLink,
           };
           for (size_t idx = 0; idx < sizeof(g_sections) / sizeof(g_sections[0]);
                ++idx) {
             SectionType section_type = g_sections[idx];
             SectionSP section_sp(
                 objfile_section_list->FindSectionByType(section_type, true));
             if (section_sp) {
               SectionSP module_section_sp(

source/Symbol/ObjectFile.cpp

if (symbol) {
           case eSectionTypeDWARFDebugPubTypes:
           case eSectionTypeDWARFDebugRanges:
           case eSectionTypeDWARFDebugStr:
           case eSectionTypeDWARFDebugStrOffsets:
           case eSectionTypeDWARFAppleNames:
           case eSectionTypeDWARFAppleTypes:
           case eSectionTypeDWARFAppleNamespaces:
           case eSectionTypeDWARFAppleObjC:
+          case eSectionTypeDWARFGNUDebugAltLink:
             return eAddressClassDebug;
           case eSectionTypeEHFrame:
           case eSectionTypeARMexidx:
           case eSectionTypeARMextab:
           case eSectionTypeCompactUnwind:
             return eAddressClassRuntime;
           case eSectionTypeELFSymbolTable:
           case eSectionTypeELFDynamicSymbols: