[Lldb-commits] [lldb] Allow lldb to load .dwp files with large .debug_info or .debug_types. (PR #73736)

[Greg Clayton via lldb-commits]

https://github.com/clayborg created https://github.com/llvm/llvm-project/pull/73736

A previous patch to llvm allowed the DWARFUnitIndex class to handle .debug_info.dwo and .debug_types.dwo sections to go over 4GB by checking for this case and fixing up the DWARFUnitIndex. LLDB's DWARF parser tries to use the llvm's DWARF parser when it can, and LLDB's DWARF parser uses the llvm::DWARFUnitIndex which should allow us to load large .dwp files, but there were a few things missing on the LLDB front:
- support for parsing DWARFUnit objects when the offset exceeds 4GB due to a 32 bit truncation issue
- not populating the required DWARF sections when we call DWARFContext::GetAsLLVM() which didn't allow the fixups to happen as the data was missing.

This patch fixes these issues and now allows LLDB to parse large .dwp files without issues. The issue was discovered when running the "target modules dump separate-debug-info" command on one of these binaries that used a large .dwp file.

This is unfortunately hard to test without creating a huge .dwp file, so there are currently no tests for this that I can think of adding that wouldn't cause disk space constraints or making testing times longer by producing a huge .dwp file.

>From 80f6d62d718c8cad6ce35a77d2e3e75b2fe92f17 Mon Sep 17 00:00:00 2001
From: Greg Clayton <clayborg at gmail.com>
Date: Tue, 28 Nov 2023 18:03:47 -0800
Subject: [PATCH] Allow lldb to load .dwp files with large .debug_info or
 .debug_types.

A previous patch to llvm allowed the DWARFUnitIndex class to handle .debug_info.dwo and .debug_types.dwo sections to go over 4GB by checking for this case and fixing up the DWARFUnitIndex. LLDB's DWARF parser tries to use the llvm's DWARF parser when it can, and LLDB's DWARF parser uses the llvm::DWARFUnitIndex which should allow us to load large .dwp files, but there were a few things missing on the LLDB front:
- support for parsing DWARFUnit objects when the offset exceeds 4GB due to a 32 bit truncation issue
- not populating the required DWARF sections when we call DWARFContext::GetAsLLVM() which didn't allow the fixups to happen as the data was missing.

This patch fixes these issues and now allows LLDB to parse large .dwp files without issues. The issue was discovered when running the "target modules dump separate-debug-info" command on one of these binaries that used a large .dwp file.

This is unfortunately hard to test without creating a huge .dwp file, so there are currently no tests for this that I can think of adding that wouldn't cause disk space constraints or making testing times longer by producing a huge .dwp file.
---
 lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.cpp | 5 ++++-
 lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h      | 4 ++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.cpp
index ee347036dbbc034..e3872dc626be038 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.cpp
@@ -142,7 +142,10 @@ llvm::DWARFContext &DWARFContext::GetAsLLVM() {
     AddSection("debug_line_str", getOrLoadLineStrData());
     AddSection("debug_cu_index", getOrLoadCuIndexData());
     AddSection("debug_tu_index", getOrLoadTuIndexData());
-
+    if (isDwo()) {
+      AddSection("debug_info.dwo", getOrLoadDebugInfoData());
+      AddSection("debug_types.dwo", getOrLoadDebugTypesData());
+    }
     m_llvm_context = llvm::DWARFContext::create(section_map, addr_size);
   }
   return *m_llvm_context;
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h
index 3aef03712d00dc8..3f528e913d8cfab 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h
@@ -76,7 +76,7 @@ class DWARFUnitHeader {
     return m_unit_type == llvm::dwarf::DW_UT_type ||
            m_unit_type == llvm::dwarf::DW_UT_split_type;
   }
-  uint32_t GetNextUnitOffset() const { return m_offset + m_length + 4; }
+  dw_offset_t GetNextUnitOffset() const { return m_offset + m_length + 4; }
 
   llvm::Error ApplyIndexEntry(const llvm::DWARFUnitIndex::Entry *index_entry);
 
@@ -157,7 +157,7 @@ class DWARFUnit : public UserID {
   // Size of the CU data (without initial length and without header).
   size_t GetDebugInfoSize() const;
   // Size of the CU data incl. header but without initial length.
-  uint32_t GetLength() const { return m_header.GetLength(); }
+  dw_offset_t GetLength() const { return m_header.GetLength(); }
   uint16_t GetVersion() const { return m_header.GetVersion(); }
   const llvm::DWARFAbbreviationDeclarationSet *GetAbbreviations() const;
   dw_offset_t GetAbbrevOffset() const;