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44 lines
1.4 KiB
Markdown
44 lines
1.4 KiB
Markdown
# Tutorial 01 - Wait Forever
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## tl;dr
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Project skeleton is set up; Code just halts all CPU cores executing the kernel code.
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- Toolchain: `cargo xbuild` tools (`xrustc`, `xclippy`) and the
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`aarch64-unknown-none-softfloat` target are used for building `AArch64`
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bare-metal code.
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- `Makefile` targets:
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- `doc`: Generate documentation.
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- `qemu`: Run the `kernel` in QEMU
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- `clippy`
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- `clean`
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- `readelf`: Inspect the `ELF` output.
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- `objdump`: Inspect the assembly.
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- `nm`: Inspect the symbols.
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- Code is organized into `kernel`, `arch` and `BSP` (Board Support Package)
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parts.
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- Conditional compilation includes respective `arch` and `BSP` according to
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user-supplied arguments.
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- Custom `link.ld` linker script.
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- Load address at `0x80_000`
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- Only `.text` section.
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- `main.rs`: Important [inner attributes]:
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- `#![no_std]`, `#![no_main]`
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- Assembly `_start()` function that executes `wfe` (Wait For Event), halting all
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cores that are executing `_start()`.
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- We (have to) define a `#[panic_handler]` function.
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- Just waits infinitely for a cpu event.
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[inner attributes]: https://doc.rust-lang.org/reference/attributes.html
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### Test it
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In the project folder, invoke QEMU and observe the CPU core spinning on `wfe`:
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```console
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» make qemu
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[...]
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IN:
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0x00080000: d503205f wfe
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0x00080004: 17ffffff b #0x80000
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```
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