Can't compile the bootloader

[Milk-Cool]

Hi!

The error is:

error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-lowos` target may not support the standard library
  = note: `std` is required by `ovmf_prebuilt` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

The kernel is pretty much blog_os which you are probably already familiar with.

/Cargo.toml:

[package]
name = "lowos-wrapper"
version = "0.1.0"

[build-dependencies]
bootloader = "0.11"
lowos = { path = "lowos", artifact = "bin", target = "./lowos/x86_64-lowos.json" }

[dependencies]
ovmf-prebuilt = "0.1.0-alpha.1"

[workspace]
members = ["lowos"]

/.cargo/config.toml

[unstable]
# enable the unstable artifact-dependencies feature, see
# https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#artifact-dependencies
bindeps = true
build-std-features = ["compiler-builtins-mem"]
build-std = ["core", "compiler_builtins"]

[build]
target = "lowos/x86_64-lowos.json"

[target.'cfg(target_os = "none")']
runner = "bootimage runner"

/lowos/.cargo/config.toml

[unstable]
build-std-features = ["compiler-builtins-mem"]
build-std = ["core", "compiler_builtins"]

[build]
target = "x86_64-lowos.json"

[target.'cfg(target_os = "none")']
runner = "bootimage runner"

Other files are just like in the template.

System: Ubuntu 23.10

[Freax13]

Try removing the target key from .cargo/config.toml. You only want to compile lowos using your target, you don't want lowos-wrapper and its dependencies (including ovmf_prebuilt) to use this target.

[Milk-Cool]

Yes, but here it says that a target is needed to recompile std.

error: -Zbuild-std requires --target

If I don't recompile std, then it won't install some required packages with this error:

error[E0463]: can't find crate for `core`
...
error[E0463]: can't find crate for `std`

[Freax13]

Try passing --target x86_64-unknown-linux-gnu. AFAICT, as of right now bindeps and custom targets (-> build-std), don't play very well together, so passing the target explicitly is required.

Depending on your use case, you might be able to use x86_64-unknown-none for lowos. x86_64-unknown-none doesn't need build-std.

[Milk-Cool]

I want to build an image to run something that I shamelessly copy-pasted on real hardware.

Also, if I add --target x86_64-unknown-linux-gnu (or --target x86_64-unknown-none, idk what you meant to put here) to either cargo run or cargo build, it prints the following error:

thread 'main' panicked at src/cargo/core/compiler/unit_dependencies.rs:178:34:
no entry found for key
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[Milk-Cool]

found this: rust-lang/cargo#10444

still open, is there maybe a workaround for this issue?

[Freax13]

found this: rust-lang/cargo#10444

Yup, I was about to say that as well.

still open, is there maybe a workaround for this issue?

No, there isn't, but you don't need this.

You seem to have mixed the files meant to be used with older versions of the bootloader with files meant for the current version. Try the following steps:

1. Delete /lowos/.cargo/config.toml.
2. Replace /.cargo/config.toml with just

[unstable]
# enable the unstable artifact-dependencies feature, see
# https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#artifact-dependencies
bindeps = true

3. Replace lowos = { path = "lowos", artifact = "bin", target = "./lowos/x86_64-lowos.json" } with lowos = { path = "lowos", artifact = "bin", target = "x86_64-unknown-none }

[Milk-Cool]

I followed your steps, and got the following error:

error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = note: `std` is required by `ovmf_prebuilt` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

So I added build-std = ["core", "compiler_builtins"] to /.cargo/config.toml. (I also tried cargo build -Zbuild-std=core,compiler_builtins.) Then I got

error: -Zbuild-std requires --target

So I added

[build]
target = "x86_64-unknown-none"

to config.toml, and I got the same error as before:

error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = note: `std` is required by `ovmf_prebuilt` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

A little confused here...

[Freax13]

Please undo

I followed your steps, and got the following error:

error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = note: `std` is required by `ovmf_prebuilt` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

So I added build-std = ["core", "compiler_builtins"] to /.cargo/config.toml. (I also tried cargo build -Zbuild-std=core,compiler_builtins.) Then I got

this

error: -Zbuild-std requires --target

So I added

[build]
target = "x86_64-unknown-none"

to config.toml, and I got the same error as before:

and this.

error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = note: `std` is required by `ovmf_prebuilt` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

A little confused here...

What command are you using to build/run the kernel?

[Milk-Cool]

What command are you using to build/run the kernel?

cargo build, though cargo run doesn't work either

[Freax13]

Is that the whole command or are you adding additional arguments (e.g. --target x86_64-unknown-none)?

[Milk-Cool]

Yep, that's the whole command, though I have tried cargo build -Zbuild-std=core,compiler_builtins --target=x86_64-unknown-none

[Freax13]

That's odd. Could you repeat the content of your files?

[Milk-Cool]

/Cargo.toml

[package]
name = "lowos-wrapper"
version = "0.1.0"

[build-dependencies]
bootloader = "0.11"
lowos = { path = "lowos", artifact = "bin", target = "x86_64-unknown-none" }

[dependencies]
ovmf-prebuilt = "0.1.0-alpha.1"

[workspace]
members = ["lowos"]

/lowos/Cargo.toml

[package]
name = "lowos"
version = "0.1.0"
edition = "2018"

[dependencies]
#bootloader = "0.9"
volatile = "0.2.6"
spin = "0.5.2"
x86_64 = "0.14.2"
pic8259 = "0.10.1"
pc-keyboard = "0.5.0"

[dependencies.lazy_static]
version = "1.0"
features = ["spin_no_std"]

(commented the bootloader = "0.9" here)
/.cargo/config.toml

[unstable]
# enable the unstable artifact-dependencies feature, see
# https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#artifact-dependencies
bindeps = true

main.rs and build.rs are unchanged.

[Freax13]

Have you installed the x86_64-unknown-none target (you can do so using rustup target add x86_64-unknown-none)? This doesn't fully explain the errors you sent (though they'd look almost identical), but installing the target is required in any case.

[Milk-Cool]

Yes, I have installed the target:

user@hostname:~/Documents/GitHub/lowos-wrapper$ rustup target add x86_64-unknown-none
info: component 'rust-std' for target 'x86_64-unknown-none' is up to date

[Freax13]

I'm very confused as to why cargo would want to build ovmf_prebuilt using x86_64-unknown-none. Could you run cargo +nightly -Z unstable-options config get --show-origin?

[Milk-Cool]

unstable.bindeps = true # /home/user/Documents/GitHub/lowos-wrapper/.cargo/config.toml
# The following environment variables may affect the loaded values.
# CARGO_HOME=/home/user/.cargo

[Milk-Cool]

also, it probably builds ovmf_prebuilt with x86_64-unknown-none because i build the whole project with that target. i'm new to rust but it's my best guess - i didn't see any config values telling that cargo should build it for linux

[Freax13]

also, it probably builds ovmf_prebuilt with x86_64-unknown-none because i build the whole project with that target. i'm new to rust but it's my best guess - i didn't see any config values telling that cargo should build it for linux

Ah, that's why I was asking you about the command you were using to build the project. Please use just cargo build (and don't use --target).

[Milk-Cool]

Hm, that outputs

   Compiling bitflags v2.5.0
error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = note: `std` is required by `bitflags` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

though when I use cargo build -Zbuild-std=core,compiler_builtins --target=x86_64-unknown-none it outputs more std-related errors:

error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = note: `std` is required by `ovmf_prebuilt` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

error[E0463]: can't find crate for `std`
 --> /home/milan/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ovmf-prebuilt-0.1.0-alpha.1/src/lib.rs:1:5
  |
1 | use std::path::{PathBuf, Path};
  |     ^^^ can't find crate
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = note: `std` is required by `bitflags` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

[Freax13]

Hm, that outputs

   Compiling bitflags v2.5.0
error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = note: `std` is required by `bitflags` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

That's progress though. Try adding edition = "2021" after version = "0.1.0" in /Cargo.toml or add resolver = "2" in the workspace section.

though when I use cargo build -Zbuild-std=core,compiler_builtins --target=x86_64-unknown-none it outputs more std-related errors:

error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = note: `std` is required by `ovmf_prebuilt` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

error[E0463]: can't find crate for `std`
 --> /home/milan/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ovmf-prebuilt-0.1.0-alpha.1/src/lib.rs:1:5
  |
1 | use std::path::{PathBuf, Path};
  |     ^^^ can't find crate
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = note: `std` is required by `bitflags` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

Nope, that's making things worse again.

[Milk-Cool]

Try adding edition = "2021"

That did work, though now a build script is causing issues:

error: failed to run custom build command for `lowos-wrapper v0.1.0 (/home/milan/Documents/GitHub/lowos-wrapper)`

Caused by:
  process didn't exit successfully: `/home/user/Documents/GitHub/lowos-wrapper/target/debug/build/lowos-wrapper-d1a379c54d8a204b/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at build.rs:8:81:
  called `Option::unwrap()` on a `None` value
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[Milk-Cool]

oh, could it be an issue with build.rs?

[Milk-Cool]

Yes, I forgot to replace CARGO_BIN_FILE_KERNEL_kernel with CARGO_BIN_FILE_LOWOS_lowos. Let me see if it works now.

[Milk-Cool]

Do I need to read the documentation? I didn't see any mention of this

[Freax13]

Do I need to read the documentation? I didn't see any mention of this

That's exactly what you need to do :) Here's the relevant section. You'll also need to add the bootloader_api dependency to /lowos/Cargo.toml.

[Milk-Cool]

It seems to be working! As far as I could tell, I need to re-implement printing to the screen, but for now I think I can close the issue. Thank you so much!