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This migrates the x86-64 application processor boot code from NASM to GNU assembly language. `boot.asm` is replaced by `boot.s`. Instead of NASM directives, their GNU assembler (`as`) equivalents are used. This assembly file is embedded in an LLVM assembly language file with only one module level (global) assembly statement. Rust bundles `llvm-as`, which we use to translate the LLVM assembly to LLVM bitcode. The resulting file is linked to binary using the bundled `rust-lld`. The final binary is exactly the same as before, bit for bit. This finally removes NASM as the last non-Rust toolchain dependency. Signed-off-by: Martin Kröning <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,87 @@ | ||
| use std::fs::File; | ||
| use std::io::Write; | ||
| use std::path::{Path, PathBuf}; | ||
| use std::process::Command; | ||
| use std::{env, fs}; | ||
|
|
||
| use anyhow::{anyhow, Context, Result}; | ||
| use llvm_tools::LlvmTools; | ||
|
|
||
| fn main() -> Result<()> { | ||
| if env::var("CARGO_CFG_TARGET_ARCH").unwrap() == "x86_64" | ||
| && env::var_os("CARGO_FEATURE_SMP").is_some() | ||
| { | ||
| assemble_x86_64_smp_boot()?; | ||
| } | ||
|
|
||
| Ok(()) | ||
| } | ||
|
|
||
| fn assemble_x86_64_smp_boot() -> Result<()> { | ||
| let out_dir = PathBuf::from(env::var_os("OUT_DIR").unwrap()); | ||
|
|
||
| let boot_s = Path::new("src/arch/x86_64/kernel/boot.s"); | ||
| let boot_ll = out_dir.join("boot.ll"); | ||
| let boot_bc = out_dir.join("boot.bc"); | ||
| let boot_bin = out_dir.join("boot.bin"); | ||
|
|
||
| let llvm_as = binutil("llvm-as")?; | ||
| let rust_lld = binutil("rust-lld")?; | ||
|
|
||
| let assembly = fs::read_to_string(boot_s)?; | ||
|
|
||
| let mut llvm_file = File::create(&boot_ll)?; | ||
| writeln!( | ||
| &mut llvm_file, | ||
| r#"target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" | ||
| target triple = "x86_64-unknown-none-elf" | ||
| module asm " | ||
| {assembly} | ||
| " | ||
| "# | ||
| )?; | ||
| llvm_file.flush()?; | ||
| drop(llvm_file); | ||
|
|
||
| let status = Command::new(&llvm_as) | ||
| .arg("-o") | ||
| .arg(&boot_bc) | ||
| .arg(boot_ll) | ||
| .status() | ||
| .with_context(|| format!("Failed to run llvm-as from {}", llvm_as.display()))?; | ||
| assert!(status.success()); | ||
|
|
||
| let status = Command::new(&rust_lld) | ||
| .arg("-flavor") | ||
| .arg("gnu") | ||
| .arg("--section-start=.text=0x8000") | ||
| .arg("--oformat=binary") | ||
| .arg("-o") | ||
| .arg(&boot_bin) | ||
| .arg(&boot_bc) | ||
| .status() | ||
| .with_context(|| format!("Failed to run rust-lld from {}", rust_lld.display()))?; | ||
| assert!(status.success()); | ||
|
|
||
| println!("cargo:rerun-if-changed={}", boot_s.display()); | ||
| Ok(()) | ||
| } | ||
|
|
||
| fn binutil(name: &str) -> Result<PathBuf> { | ||
| let exe = format!("{name}{}", env::consts::EXE_SUFFIX); | ||
|
|
||
| let path = LlvmTools::new() | ||
| .map_err(|err| match err { | ||
| llvm_tools::Error::NotFound => anyhow!( | ||
| "Could not find llvm-tools component\n\ | ||
| \n\ | ||
| Maybe the rustup component `llvm-tools` is missing? Install it through: `rustup component add llvm-tools`" | ||
| ), | ||
| err => anyhow!("{err:?}"), | ||
| })? | ||
| .tool(&exe) | ||
| .ok_or_else(|| anyhow!("could not find {exe}"))?; | ||
|
|
||
| Ok(path) | ||
| } |
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