More info about shared libraries

Author: grendello

tools/apput/src/Native/NativeAotSharedLibrary.cs

@@ -18,9 +18,7 @@ class NativeAotSharedLibrary : SharedLibrary
 
 	protected NativeAotSharedLibrary (Stream stream, string libraryName)
 		: base (stream, libraryName)
-	{
-		// TODO: perhaps gather some more stats? Code size, data size, alignment, stuff like that
-	}
+	{}
 
 	public new static IAspect LoadAspect (Stream stream, IAspectState? state, string? description)
 	{

tools/apput/src/Native/SharedLibrary.cs

@@ -4,29 +4,45 @@
 
 using ELFSharp.ELF;
 using ELFSharp.ELF.Sections;
+using ELFSharp.ELF.Segments;
 
 namespace ApplicationUtility;
 
 class SharedLibrary : IAspect, IDisposable
 {
 	const uint ELF_MAGIC = 0x464c457f;
+	const string DebugLinkSectionName = ".gnu_debuglink";
+	const string PayloadSectionName = "payload";
 
+	readonly IELF elf;
+	readonly NativeArchitecture nativeArch = NativeArchitecture.Unknown;
+	readonly Stream libraryStream;
+	readonly bool hasDebugInfo;
+	readonly bool is64Bit;
+	readonly string libraryName;
+	readonly string? androidIdent;
+	readonly string? buildId;
+	readonly string? debugLink;
+	readonly ulong libraryAlignment;
 	readonly ulong payloadOffset;
 	readonly ulong payloadSize;
-	readonly string libraryName;
-	readonly bool is64Bit;
-	readonly Stream libraryStream;
 
-	IELF elf;
 	bool disposed;
-	NativeArchitecture nativeArch = NativeArchitecture.Unknown;
 
 	public static string AspectName { get; } = "Native shared library";
 
-	public bool HasAndroidPayload => payloadSize > 0;
-	public string Name => libraryName;
 	public NativeArchitecture TargetArchitecture => nativeArch;
+	public bool HasAndroidIdent => !String.IsNullOrEmpty (androidIdent);
+	public bool HasAndroidPayload => payloadSize > 0;
+	public bool HasBuildID => !String.IsNullOrEmpty (buildId);
+	public bool HasDebugInfo => hasDebugInfo;
+	public bool HasDebugLink => !String.IsNullOrEmpty (debugLink);
 	public bool Is64Bit => is64Bit;
+	public string Name => libraryName;
+	public string? AndroidIdent => androidIdent;
+	public string? BuildID => buildId;
+	public string? DebugLink => debugLink;
+	public ulong Alignment => libraryAlignment;
 
 	protected IELF ELF => elf;
 
@@ -36,6 +52,10 @@ protected SharedLibrary (Stream stream, string libraryName)
 		this.libraryName = libraryName;
 		(elf, is64Bit, nativeArch) = LoadELF (stream, libraryName);
 		(payloadOffset, payloadSize) = FindAndroidPayload (elf);
+		libraryAlignment = DetectAlignment (elf, is64Bit);
+		(hasDebugInfo, debugLink) = DetectDebugInfo (elf, libraryName);
+		buildId = GetBuildID (elf, is64Bit);
+		androidIdent = GetAndroidIdent (elf, is64Bit);
 	}
 
 	public static IAspect LoadAspect (Stream stream, IAspectState? state, string? description)
@@ -172,8 +192,8 @@ protected static bool IsSupportedELFSharedLibrary (Stream stream, string? descri
 
 	(ulong offset, ulong size) FindAndroidPayload (IELF elf)
 	{
-		if (!elf.TryGetSection ("payload", out ISection? payloadSection)) {
-			Log.Debug ($"SharedLibrary: shared library '{libraryName}' doesn't have the 'payload' section.");
+		if (!elf.TryGetSection (PayloadSectionName, out ISection? payloadSection)) {
+			Log.Debug ($"SharedLibrary: shared library '{libraryName}' doesn't have the '{PayloadSectionName}' section.");
 			return (0, 0);
 		}
 
@@ -200,6 +220,112 @@ protected static bool IsSupportedELFSharedLibrary (Stream stream, string? descri
 		}
 	}
 
+	static (bool hasDebugInfo, string? debugLink) DetectDebugInfo (IELF elf, string libraryName)
+	{
+		bool hasDebugInfo = HasSection (elf, libraryName, ".debug_info", SectionType.ProgBits);
+
+		if (!HasSection (elf, libraryName, DebugLinkSectionName, SectionType.ProgBits)) {
+			return (hasDebugInfo, null);
+		}
+
+		return (hasDebugInfo, ReadDebugLinkSection (elf, libraryName));
+	}
+
+	static string? ReadDebugLinkSection (IELF elf, string libraryName)
+	{
+		Log.Debug ($"Trying to load debug link section from {libraryName}");
+		if (!elf.TryGetSection (DebugLinkSectionName, out ISection? section)) {
+			Log.Debug ($"Debug link section '{DebugLinkSectionName}' could not be read");
+			return null;
+		}
+
+		// From https://sourceware.org/gdb/current/onlinedocs/gdb.html/Separate-Debug-Files.html
+		//
+		//  * A filename, with any leading directory components removed, followed by a zero byte,
+		//  * zero to three bytes of padding, as needed to reach the next four-byte boundary within the section, and
+		//  * a four-byte CRC checksum, stored in the same endianness used for the executable file itself. The checksum is computed on the debugging information file’s full
+		//    contents by the function given below, passing zero as the crc argument.
+
+		// TODO: At this point we ignore the CRC, perhaps it would be worth reading it?
+		byte[] contents = section.GetContents ();
+		if (contents.Length < 4) {
+			// there must at least be the 4-byte CRC, otherwise section content is invalid
+			return null;
+		}
+
+		int zeroIndex = 0;
+		for (int i = 0; i < contents.Length; i++) {
+			if (contents[i] != 0) {
+				continue;
+			}
+
+			zeroIndex = i;
+			break;
+		}
+
+		if (zeroIndex == 0) {
+			return null;
+		}
+
+		return Encoding.UTF8.GetString (contents, 0, zeroIndex);
+	}
+
+	static ulong DetectAlignment (IELF elf, bool is64Bit)
+	{
+		if (!elf.HasSegmentHeader) {
+			return 0;
+		}
+
+		foreach (ISegment segment in elf.Segments) {
+			if (segment.Type != SegmentType.Load) {
+				continue;
+			}
+
+			if (is64Bit) {
+				return ((Segment<ulong>)segment).Alignment;
+			}
+
+			return ((Segment<uint>)segment).Alignment;
+		}
+
+		return 0;
+	}
+
+	static string? GetBuildID (IELF elf, bool is64Bit)
+	{
+		byte[]? contents = GetNoteSectionContents (elf, is64Bit, ".note.gnu.build-id");
+		if (contents == null) {
+			return null;
+		}
+
+		// TODO: decode
+		return "decoding not implemented yet";
+	}
+
+	static string? GetAndroidIdent (IELF elf, bool is64Bit)
+	{
+		return GetNoteSectionContentsAsString (elf, is64Bit, ".note.android.ident");;
+	}
+
+	static string? GetNoteSectionContentsAsString (IELF elf, bool is64Bit, string sectionName)
+	{
+		byte[]? contents = GetNoteSectionContents (elf, is64Bit, sectionName);
+		if (contents == null) {
+			return null;
+		}
+
+		return Encoding.UTF8.GetString (contents);
+	}
+
+	static byte[]? GetNoteSectionContents (IELF elf, bool is64Bit, string sectionName)
+	{
+		if (!elf.TryGetSection (sectionName, out ISection? section) || section == null || section.Type != SectionType.Note) {
+			return null;
+		}
+
+		return ((INoteSection)section).Description;
+	}
+
 	public bool HasSection (string name, SectionType type = SectionType.Null)
 	{
 		return HasSection (elf, libraryName, name, type);

tools/apput/src/Reporters/BaseReporter.cs

@@ -4,8 +4,9 @@ namespace ApplicationUtility;
 
 abstract class BaseReporter : IReporter
 {
-	const ConsoleColor LabelColor = ConsoleColor.White;
-	const ConsoleColor ValueColor = ConsoleColor.Green;
+	protected const ConsoleColor LabelColor = ConsoleColor.White;
+	protected const ConsoleColor ValidValueColor = ConsoleColor.Green;
+	protected const ConsoleColor InvalidValueColor = ConsoleColor.Red;
 
 	public abstract void Report ();
 
@@ -19,10 +20,15 @@ protected void WriteNativeArch (NativeArchitecture arch)
 		WriteItem ("Native target architecture", arch.ToString ());
 	}
 
-	protected void WriteItem (string label, string value)
+	protected void WriteLabel (string label)
 	{
 		Write (LabelColor, $"{label}: ");
-		WriteLine (ValueColor, value);
+	}
+
+	protected void WriteItem (string label, string value)
+	{
+		WriteLabel (label);
+		WriteLine (ValidValueColor, value);
 	}
 
 	protected void WriteLine ()
@@ -35,6 +41,7 @@ protected void WriteLine (ConsoleColor color, string text)
 		Write (color, text);
 		WriteLine ();
 	}
+
 	protected void Write (ConsoleColor color, string text)
 	{
 		ConsoleColor oldFG = Console.ForegroundColor;
@@ -45,4 +52,6 @@ protected void Write (ConsoleColor color, string text)
 			Console.ForegroundColor = oldFG;
 		}
 	}
+
+	protected string YesNo (bool yes) => yes ? "yes" : "no";
 }

tools/apput/src/Reporters/NativeAotSharedLibraryReporter.cs

@@ -1,18 +1,20 @@
 namespace ApplicationUtility;
 
 [AspectReporter (typeof (NativeAotSharedLibrary))]
-class NativeAotSharedLibraryReporter : BaseReporter
+class NativeAotSharedLibraryReporter : SharedLibraryReporter
 {
 	readonly NativeAotSharedLibrary library;
 
+	protected override string LibraryKind => "NativeAOT shared library";
+
 	public NativeAotSharedLibraryReporter (NativeAotSharedLibrary library)
+		: base (library)
 	{
 		this.library = library;
 	}
 
 	public override void Report ()
 	{
-		WriteAspectDesc ("NativeAOT shared library");
-		WriteNativeArch (library.TargetArchitecture);
+		base.Report ();
 	}
 }

tools/apput/src/Reporters/SharedLibraryReporter.cs

@@ -0,0 +1,50 @@
+using System.Text;
+
+namespace ApplicationUtility;
+
+[AspectReporter (typeof (NativeAotSharedLibrary))]
+class SharedLibraryReporter : BaseReporter
+{
+	readonly SharedLibrary library;
+	protected virtual string LibraryKind => "Shared library";
+
+	public SharedLibraryReporter (SharedLibrary library)
+	{
+		this.library = library;
+	}
+
+	public override void Report ()
+	{
+		WriteAspectDesc (LibraryKind);
+		WriteNativeArch (library.TargetArchitecture);
+		WriteItem ("Build ID", library.HasBuildID ? library.BuildID! : "none");
+		WriteDebugInfoDesc ();
+
+		if (library.HasAndroidIdent) {
+			WriteItem ("Android ident", library.AndroidIdent!);
+		}
+	}
+
+	protected void WriteDebugInfoDesc ()
+	{
+		WriteItem ("Has debug info", YesNo (library.HasDebugInfo));
+
+		var sb = new StringBuilder (YesNo (library.HasDebugLink));
+		if (library.HasDebugLink) {
+			sb.Append (" ('");
+			sb.Append (library.DebugLink);
+			sb.Append ("')");
+		}
+		WriteItem ("Has debug link", sb.ToString ());
+
+		bool compatibleWith16k = library.Alignment >= 0x4000 && (library.Alignment % 0x4000 == 0);
+		sb.Clear ();
+		sb.Append ($"0x{library.Alignment:x} (");
+		if (!compatibleWith16k) {
+			sb.Append ("NOT ");
+		}
+		sb.Append ("compatible with Android 16k library alignment)");
+		WriteLabel ("Alignment");
+		WriteLine (compatibleWith16k ? ValidValueColor : InvalidValueColor, sb.ToString ());
+	}
+}