Generate `.comment` section for ELF executables #113218

MichalStrehovsky · 2025-03-06T15:05:16Z

This is the standard way to emit compiler version info on ELF. No standard way for other formats.

Cc @dotnet/ilc-contrib

This is the standard way to emit compiler version info on ELF. No standard way for other formats.

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PR Overview

This PR adds support for emitting a .comment section in ELF executables to provide compiler version information.

Adds a new using directive for System.Reflection.
Introduces a CommentSection static field and adds handling for it in CreateSection.
Implements writing of the .comment section using the assembly's informational version in EmitSectionsAndLayout.

Reviewed Changes

File	Description
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/ElfObjectWriter.cs	Adds .comment section handling to embed compiler version info for ELF executables

Copilot reviewed 1 out of 1 changed files in this pull request and generated no comments.

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src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/ElfObjectWriter.cs:578

Accessing InformationalVersion directly may throw a NullReferenceException if AssemblyInformationalVersionAttribute is missing. Consider adding a null-check or providing a default value.

commentSectionWriter.WriteUtf8String($".NET AOT {Assembly.GetExecutingAssembly().GetCustomAttribute<AssemblyInformationalVersionAttribute>().InformationalVersion}");

dotnet-policy-service · 2025-03-06T15:05:51Z

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MichalStrehovsky · 2025-03-06T15:07:19Z

D:\crosstest>wsl readelf -p .comment bin/Release/net10.0/linux-x64/publish/crosstest

String dump of section '.comment':
  [     0]  clang version 19.1.6
  [    16]  clang version 19.1.7 (https://github.com/ziglang/zig-bootstrap 1c3c59435891bc9caf8cd1d3783773369d191c5f)
  [    7f]  Linker: LLD 19.1.7 (https://github.com/ziglang/zig-bootstrap 1c3c59435891bc9caf8cd1d3783773369d191c5f)
  [    e6]  .NET AOT 10.0.0-dev

filipnavara · 2025-03-06T16:21:38Z

No standard way for other formats.

Mach-O actually has somewhat standard way, if we want to populate it. LC_BUILD_VERSION has option to specify tool versions. The tools are specified using numerical values (Clang = 1, Swift = 2, LD = 3, LLD = 4) and a corresponding version. Not sure whether it's worth it to hijack one of the existing entries.

The information is also present in the DWARF debugging info IIRC.

am11 · 2025-03-06T16:22:22Z

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/ElfObjectWriter.cs

@@ -567,6 +574,9 @@ private void EmitRelocationsRiscV64(int sectionIndex, List<SymbolicRelocation> r

        private protected override void EmitSectionsAndLayout()
        {
+            SectionWriter commentSectionWriter = GetOrCreateSection(CommentSection);
+            commentSectionWriter.WriteUtf8String($".NET AOT {Assembly.GetExecutingAssembly().GetCustomAttribute<AssemblyInformationalVersionAttribute>().InformationalVersion}");


Should it be .NET Native AOT, the proper brand name?

I think shorter string is better, we just need something reasonably unique.

Makes sense this is for technical use for crash investigations etc. BTW, with Native, it'll be 94 characters. These two will still be the longest (117 and 115 respectively):

[ 16] clang version 19.1.7 (https://github.com/ziglang/zig-bootstrap 1c3c59435891bc9caf8cd1d3783773369d191c5f) [ 7f] Linker: LLD 19.1.7 (https://github.com/ziglang/zig-bootstrap 1c3c59435891bc9caf8cd1d3783773369d191c5f)

If this is a concern for someone, they can drop the .comment section from the binary (using tools like objcopy).

.NET Native AOT, the proper brand name

.NET Native AOT is not a proper brand name since it is not its own product. The docs talk about native AOT without .NET prefix, same as how they talk about any other .NET feature. There should be zero hits for ".NET Native AOT" in docs and dotnet-api-docs

".NET AOT" is pushing it too.

My preference would be one of the following strings:
.NET 10.0.0-preview3...
.NET: ilc 10.0.0-preview3...
.NET: Native AOT 10.0.0-preview3...
.NET: PublishAot 10.0.0-preview3...

I don't have a preference; rolled a dice and went with one of these in #113255.

2 sounds good. ilc is, relatable, name of the tool.

agocke · 2025-03-06T17:39:56Z

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/ElfObjectWriter.cs

@@ -567,6 +574,9 @@ private void EmitRelocationsRiscV64(int sectionIndex, List<SymbolicRelocation> r

        private protected override void EmitSectionsAndLayout()
        {
+            SectionWriter commentSectionWriter = GetOrCreateSection(CommentSection);
+            commentSectionWriter.WriteUtf8String($".NET AOT {Assembly.GetExecutingAssembly().GetCustomAttribute<AssemblyInformationalVersionAttribute>().InformationalVersion}");


I assume the informational version is what we want here. I don’t know what else we would pick. It might be nice to include the git sha, but I’m not sure if we put that anywhere but the PDB. Jeremy do you know offhand?

InformationVersion is a good choice. It returns semver with 'semver metadata', like e.g. 10.0.0-preview.3.25152.4+088d199063dd1bf7fa00a445d23f93f915f84b31. That's what differenciates it from Environment.Version (which strips away the metadata).

runtime/src/libraries/System.Private.CoreLib/gen/ProductVersionInfoGenerator.cs

Line 11 in f6948fc

public partial class ProductVersionInfoGenerator : IIncrementalGenerator

cc @akoeplinger who worked on similar topic recently (related to servicing versions)

The informational version has the commit sha (as @am11 points out), so I think it's the right choice for the scenario.

MichalStrehovsky · 2025-03-06T21:17:31Z

Mach-O actually has somewhat standard way, if we want to populate it. LC_BUILD_VERSION has option to specify tool versions. The tools are specified using numerical values (Clang = 1, Swift = 2, LD = 3, LLD = 4) and a corresponding version. Not sure whether it's worth it to hijack one of the existing entries.

I'm not a fan of hijacking values. PE also has the Rich header that we might be able to get into but it has the same problems (need to assign a new number on every major release, which is really only possible for things that live in-tree with link.exe sources).

Generate .comment section for ELF executables

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This is the standard way to emit compiler version info on ELF. No standard way for other formats.

Copilot AI review requested due to automatic review settings March 6, 2025 15:05

dotnet-issue-labeler bot added the area-NativeAOT-coreclr label Mar 6, 2025

dotnet-policy-service bot assigned MichalStrehovsky Mar 6, 2025

Copilot AI reviewed Mar 6, 2025

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MichalStrehovsky merged commit 9e7b302 into dotnet:main Mar 6, 2025
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MichalStrehovsky deleted the commentsection branch March 6, 2025 21:18

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Generate `.comment` section for ELF executables #113218

Generate `.comment` section for ELF executables #113218

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MichalStrehovsky commented Mar 6, 2025

Generate .comment section for ELF executables #113218

Generate .comment section for ELF executables #113218

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PR Overview

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MichalStrehovsky commented Mar 6, 2025

Generate `.comment` section for ELF executables #113218

Generate `.comment` section for ELF executables #113218

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