From 6b4448b62301fcb1faf47ccd34c94b162c05981d Mon Sep 17 00:00:00 2001
From: Gunnar Beutner <gbeutner@serenityos.org>
Date: Wed, 28 Apr 2021 22:13:58 +0200
Subject: [PATCH] LibDebug: Implement support for DWARF 5 compilation unit
 headers

---
 .../LibDebug/Dwarf/CompilationUnit.cpp        |  5 +-
 .../LibDebug/Dwarf/CompilationUnit.h          |  2 +-
 .../Libraries/LibDebug/Dwarf/DwarfInfo.cpp    |  8 ++--
 .../Libraries/LibDebug/Dwarf/DwarfTypes.h     | 47 ++++++++++++++++++-
 4 files changed, 54 insertions(+), 8 deletions(-)

diff --git a/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.cpp b/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.cpp
index 2b6062639f..9f6e163d87 100644
--- a/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.cpp
+++ b/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.cpp
@@ -12,13 +12,14 @@ CompilationUnit::CompilationUnit(const DwarfInfo& dwarf_info, u32 offset, const
     : m_dwarf_info(dwarf_info)
     , m_offset(offset)
     , m_header(header)
-    , m_abbreviations(dwarf_info, header.abbrev_offset)
+    , m_abbreviations(dwarf_info, header.abbrev_offset())
 {
+    VERIFY(header.version() < 5 || header.unit_type() == CompilationUnitType::Full);
 }
 
 DIE CompilationUnit::root_die() const
 {
-    return DIE(*this, m_offset + sizeof(CompilationUnitHeader));
+    return DIE(*this, m_offset + m_header.header_size());
 }
 
 }
diff --git a/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.h b/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.h
index 7a74c4eac5..d48c781b67 100644
--- a/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.h
+++ b/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.h
@@ -19,7 +19,7 @@ public:
     CompilationUnit(const DwarfInfo& dwarf_info, u32 offset, const CompilationUnitHeader&);
 
     u32 offset() const { return m_offset; }
-    u32 size() const { return m_header.length + sizeof(u32); }
+    u32 size() const { return m_header.length() + sizeof(u32); }
 
     DIE root_die() const;
 
diff --git a/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.cpp b/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.cpp
index 19d1793099..0ecc613596 100644
--- a/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.cpp
+++ b/Userland/Libraries/LibDebug/Dwarf/DwarfInfo.cpp
@@ -38,11 +38,11 @@ void DwarfInfo::populate_compilation_units()
         auto unit_offset = stream.offset();
         CompilationUnitHeader compilation_unit_header {};
 
-        stream >> Bytes { &compilation_unit_header, sizeof(compilation_unit_header) };
-        VERIFY(compilation_unit_header.address_size == sizeof(u32));
-        VERIFY(compilation_unit_header.version <= 4);
+        stream >> compilation_unit_header;
+        VERIFY(compilation_unit_header.common.version <= 5);
+        VERIFY(compilation_unit_header.address_size() == sizeof(u32));
 
-        u32 length_after_header = compilation_unit_header.length - (sizeof(CompilationUnitHeader) - offsetof(CompilationUnitHeader, version));
+        u32 length_after_header = compilation_unit_header.length() - (compilation_unit_header.header_size() - offsetof(CompilationUnitHeader, common.version));
         m_compilation_units.empend(*this, unit_offset, compilation_unit_header);
         stream.discard_or_error(length_after_header);
     }
diff --git a/Userland/Libraries/LibDebug/Dwarf/DwarfTypes.h b/Userland/Libraries/LibDebug/Dwarf/DwarfTypes.h
index c11827e40d..19de2ea809 100644
--- a/Userland/Libraries/LibDebug/Dwarf/DwarfTypes.h
+++ b/Userland/Libraries/LibDebug/Dwarf/DwarfTypes.h
@@ -6,17 +6,62 @@
 
 #pragma once
 
+#include <AK/Stream.h>
 #include <AK/Types.h>
 
 namespace Debug::Dwarf {
 
-struct [[gnu::packed]] CompilationUnitHeader {
+enum class CompilationUnitType {
+    Full = 1,
+    Partial = 3
+};
+
+struct [[gnu::packed]] CompilationUnitHeaderCommon {
     u32 length;
     u16 version;
+};
+
+struct [[gnu::packed]] CompilationUnitHeaderV4Ext {
     u32 abbrev_offset;
     u8 address_size;
 };
 
+struct [[gnu::packed]] CompilationUnitHeaderV5Ext {
+    u8 unit_type;
+    u8 address_size;
+    u32 abbrev_offset;
+};
+
+struct [[gnu::packed]] CompilationUnitHeader {
+    CompilationUnitHeaderCommon common;
+
+    union {
+        CompilationUnitHeaderV4Ext v4;
+        CompilationUnitHeaderV5Ext v5;
+    };
+
+    size_t header_size() const
+    {
+        return sizeof(common) + ((common.version <= 4) ? sizeof(v4) : sizeof(v5));
+    }
+
+    u32 length() const { return common.length; }
+    u16 version() const { return common.version; }
+    CompilationUnitType unit_type() const { return (common.version <= 4) ? CompilationUnitType::Full : (CompilationUnitType)v5.unit_type; }
+    u32 abbrev_offset() const { return (common.version <= 4) ? v4.abbrev_offset : v5.abbrev_offset; }
+    u8 address_size() const { return (common.version <= 4) ? v4.address_size : v5.address_size; }
+};
+
+inline InputStream& operator>>(InputStream& stream, CompilationUnitHeader& header)
+{
+    stream.read_or_error(Bytes { &header.common, sizeof(header.common) });
+    if (header.common.version <= 4)
+        stream.read_or_error(Bytes { &header.v4, sizeof(header.v4) });
+    else
+        stream.read_or_error(Bytes { &header.v5, sizeof(header.v5) });
+    return stream;
+}
+
 enum class EntryTag : u16 {
     None = 0,
     ArrayType = 0x1,