add DI support #35
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add DI support #35
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davibe
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The new `btf-maps` feature enables usage of BTF-defined BPF map definitions[0] instead of legacy ones. This is still work in progress and it needs modification of debug info with bpf-linker, which is being worked on in aya-rs/bpf-linker#35. This draft PR is a reference for the bpf-linker work for now. [0] https://lwn.net/Articles/790177/
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The new `btf-maps` feature enables usage of BTF-defined BPF map definitions[0] instead of legacy ones. This is still work in progress and it needs modification of debug info with bpf-linker, which is being worked on in aya-rs/bpf-linker#35. This draft PR is a reference for the bpf-linker work for now. [0] https://lwn.net/Articles/790177/
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The new `btf-maps` feature enables usage of BTF-defined BPF map definitions[0] instead of legacy ones. This is still work in progress and it needs modification of debug info with bpf-linker, which is being worked on in aya-rs/bpf-linker#35. This draft PR is a reference for the bpf-linker work for now. [0] https://lwn.net/Articles/790177/
vadorovsky
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The new `btf-maps` feature enables usage of BTF-defined BPF map definitions[0] instead of legacy ones. This is still work in progress and it needs modification of debug info with bpf-linker, which is being worked on in aya-rs/bpf-linker#35. This draft PR is a reference for the bpf-linker work for now. [0] https://lwn.net/Articles/790177/
vadorovsky
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The new `btf-maps` feature enables usage of BTF-defined BPF map definitions[0] instead of legacy ones. This is still work in progress and it needs modification of debug info with bpf-linker, which is being worked on in aya-rs/bpf-linker#35. This draft PR is a reference for the bpf-linker work for now. [0] https://lwn.net/Articles/790177/
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@davibe I just wanted to take the time to let you know how much we in the community appreciate the work you're putting in here, thank you very much for your time on this you're opening a lot of doors for the rest of us! 🍻 |
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This disables testing with rustc's LLVM until our changes have been cherry-picked to their LLVM fork, and disables installing LLVM from apt until those changes are included in an LLVM release.
The previous way of stripping (instead of sanitizing) generic names was not correct. When we define `MyStruct<T>`, then each implementation like `MyStruct<u32>` or `MyStruct<u64>` is in fact a separate type. So to differentiate them in BTF, we need to keep all of them with distinct names. However, Linux kernel doesn't accept BTF type names with the following characters: `<`, `>`, `::`, `,`, ` `. So we need to sanitize them.
First of all, change the name of `strip_generics` function to `sanitize_type_name`. The goal of it is more general - it makes sure that Rust type names are sanitized to be compatible with C. Then, instead of using `replace`, iterate over all characters once and replace characters unsupported by C with their hex representations.
The memory layout of a struct in Rust is undefined[0]; when struct fields are reordered by the compiler, we can end up with DI which has non-monotonic field offsets. The verifier does not like this[1]. Sort struct fields by offset in DI to please the verifier. [0] https://github.com/rust-lang/reference/blob/master/src/types/struct.md [1] torvalds/linux@6283fa3
Previously we were sanitizing only struct types (`DW_tag_structure_type`). Here it's done also for functions (`DW_tag_subprogram`). This change also fixes the `sanitize_type_name` function to accept the `_` character. It's a valid character in C types and converting it to `_5F_` is not great for readability.
Requires a compiletest-rs release containing Manishearth/compiletest-rs#278.
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This branch contains my efforts to enable DI support in bpf-linker and modify the LLVM IR output so that it can be loaded and potentially interoperable with C-based eBPF programs.
In short, I created an additional bpf-linker pass that visits and patches DI nodes generated by LLVM. This required two simple patches that I added to LLVM, which have been accepted and merged, but they have not been released yet. You can find the patches here:
While we wait for them to be released, I also rebased them on the rustc fork of LLVM, which you can find here:
In addition, the above requires a version of rust-llvm.sys that exposes such functions to Rust, which you can find here:
Looking forward, due to my limited time, I am unable to commit to anything specific. I welcome anyone to help out and contribute. What I have done so far works for some programs, but it’s unclear what is left to do to support the full Rust syntax. These are the next steps in my mind:
Feel free to reach out to me on Discord (dade). In the meantime, I will be slowly working on the above.