Adding support to generate rust-project.json

[thepacketgeek]

Using the linux/scripts/generate_rust_analyzer.py script as inspiration to add a make rust-analyzer target for an out-of-tree module.

Process:

• Make the $KDIR rust-project by issuing make rust-analyzer
• Extend the crates config with the out-of-tree module
• Write to rust-project.json in the module directory

Here's an example of the added module crate config:

$ more rust-project.json| tail -n 20
        {
            "cfg": [],
            "deps": [
                {
                    "crate": 6,
                    "name": "kernel"
                }
            ],
            "display_name": "rust_out_of_tree",
            "edition": "2021",
            "env": {
                "RUST_MODFILE": "This is only for rust-analyzer"
            },
            "is_proc_macro": false,
            "is_workspace_member": false,
            "root_module": "rust_out_of_tree.rs"
        }
    ],
    "sysroot_src": "/home/mat/.rustup/toolchains/1.62.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library"
}

And the updated kernel crate config (pointing at my KDIR of ../rust_for_linux):

more rust-project.json| jq 'del(.crates[].cfg) | .crates[]| select(.display_name=="kernel") '
{
  "deps": [
    {
      "crate": 0,
      "name": "core"
    },
    {
      "crate": 2,
      "name": "alloc"
    },
    {
      "crate": 3,
      "name": "macros"
    },
    {
      "crate": 4,
      "name": "build_error"
    },
    {
      "crate": 5,
      "name": "bindings"
    }
  ],
  "display_name": "kernel",
  "edition": "2021",
  "env": {
    "RUST_MODFILE": "This is only for rust-analyzer"
  },
  "is_proc_macro": false,
  "is_workspace_member": true,
  "root_module": "../rust_for_linux/rust/kernel/lib.rs",
  "source": {
    "exclude_dirs": [],
    "include_dirs": [
      "rust/kernel",
      "rust"
    ]
  }
}

===

One janky thing I'm not currently a fan of is getting the root_module and rust source file name. This script currently only supports one file/module. I'd prefer to get it from the Kbuild file by reading obj-m but I'm not sure how to do that, any suggestions here are welcome.

[jordanisaacs]

I am using the script for out of tree modules and it works fantastic. However, I am encountering a proc-macro error for the module! macro:

proc macro `module` not expanded: Proc-macro dylib loading failed: No such file or directory (OS Error 2)

Curious if you have seen it before?

[thepacketgeek]

@jordanisaacs I haven't seen that before. Do you see that when running make rust-analyzer? Or is that a rust-analyzer error message?

[jordanisaacs]

It is a rust-analyzer diagnostic error. Everything else works great (docs, go to, completion, etc). Only difference from how this PR does it is rather than calling make -C (KDIR) every time, I built the kernel rust-project.json once and just reference it.

[thepacketgeek]

Ah, you found a bug (well two), thank you @jordanisaacs. Updated the script to not typo "include_dirs", and also actually updating the list with the new fully-qualified paths.

[jordanisaacs]

Can confirm that fixed it @thepacketgeek thanks, this script is fantastic!

[ojeda]

Related: Rust-for-Linux/linux#914

[thepacketgeek]

Related: Rust-for-Linux/linux#914

Even better, nicer that module writers don't need to duplicate this effort for every module. I'll close this PR, Thank you!

[ojeda]

Thanks to you, Mat, for sending the PR! :)

If you have time, please take a look at the other PR, and perhaps give a Tested-by: ... <...> tag there (or in the mailing list) if that one worked for you (not sure if you have done kernel work upstream; if not: the tags get added to the commit message so that people get credit!).

[ojeda]

(And of course you can review it too: Reviewed-by: ... <...>)