Booting Our Binary [OS] - The LearnixOS Book<

[giscus[bot]]

ch01-02-booting-our-binary

https://www.learnix-os.com/ch01-02-booting-our-binary.html

[superboum]

In the spec JSON, you defines pointer width as strings but my cargo/rust expects an int.

// ...

// The default int is 32-bit
"target-c-int-width": 32, // instead of "32"

// The default pointer is 32-bit
"target-pointer-width": 32,  // instead of "32"

// ...

[sagi21805]

Oh yes, forgot to change it here, in git target it uses int's, this was changed in some recent rust version

Thanks for pointing that out!

[michuhu]

One minor correction. I the section 1.1 you use linker.ld and now you use linker_script.ld, which should be the same file (I suppose). This is confusing. Thanks for the great work and I'm reading on ;)

[fkessel]

Section "Building Our Target":
I don't know if I made everything the right way (I'm new to all of this), but I get the following error message on macOS:

user@Mac learnixos % cargo build --release --target 16bit_target.json
   Compiling learnixos v0.1.0 (/Users/user/projects/rust/learnixos)
error[E0463]: can't find crate for `core`
  |
  = note: the `16bit_target` target may not be installed
  = help: consider downloading the target with `rustup target add 16bit_target`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

For more information about this error, try `rustc --explain E0463`.
error: could not compile `learnixos` (bin "learnixos") due to 1 previous error

My main.rs

#![no_std]
#![no_main]

#[panic_handler]
fn panic_handler(_info: &core::panic::PanicInfo) -> ! {
    loop {}
}

#[unsafe(no_mangle)]
fn main() {}

[sagi21805]

Did you create the local target json that was explained above? This is the target that is used.
Also did you add the .cargo configuration from the last chapter?

[fkessel]

Yes I did everything as you describe and I tried some things. In the end I saw your solution to this problem that you provided in the comments of 1.1 Making a Stand Alone Binary.

Thank you for your help!

# With this arguments I got it working
cargo build --release --target 16bit_target.json -Zbuild-std=core

user@macbook learnixos % hexdump target/16bit_target/release/learnixos
0000000 0000 0000 0000 0000 0000 0000 0000 0000
*
00001f0 0000 0000 0000 0000 0000 0000 0000 aa55
0000200 1b01 3b03 0008 0000 0000 0000 0014 0000
0000210 0000 0000 7a01 0052 7c01 0108 0c1b 0404
0000220 0188 0000 0000 0000 0000 0000 0000 0000
0000230 c366
0000232