sbpf-linker 0.1.1

use std::{
    env, fs,
    ffi::CString,
    path::PathBuf,
    str::FromStr,
};

#[cfg(any(
    feature = "rust-llvm-19",
    feature = "rust-llvm-20",
    feature = "rust-llvm-21"
))]
use aya_rustc_llvm_proxy as _;
use anyhow::Context;
use thiserror::Error;
use bpf_linker::{Cpu, Linker, LinkerOptions, OptLevel, OutputType};
use clap::{
    error::ErrorKind,
    Parser,
};
use sbpf_linker::link_program;

#[derive(Debug, Error)]
enum CliError {
    #[error("optimization level needs to be between 0-3, s or z (instead was `{0}`)")]
    InvalidOptimization(String),
//     #[error("unknown emission type: `{0}` - expected one of: `llvm-bc`, `asm`, `llvm-ir`, `obj`")]
//     InvalidOutputType(String),
}

#[derive(Copy, Clone, Debug)]
struct CliOptLevel(OptLevel);

impl FromStr for CliOptLevel {
    type Err = CliError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Ok(Self(match s {
            "0" => OptLevel::No,
            "1" => OptLevel::Less,
            "2" => OptLevel::Default,
            "3" => OptLevel::Aggressive,
            "s" => OptLevel::Size,
            "z" => OptLevel::SizeMin,
            _ => return Err(CliError::InvalidOptimization(s.to_string())),
        }))
    }
}

#[derive(Debug, Parser)]
#[command(version)]
struct CommandLine {
    /// Target BPF processor. Can be one of `generic`, `probe`, `v1`, `v2`, `v3`
    #[clap(long, default_value = "generic")]
    cpu: Cpu,
    
    /// Write output to <output>
    #[clap(short, long)]
    output: PathBuf,

    /// Emit BTF information
    #[clap(long)]
    btf: bool,

    /// Permit automatic insertion of __bpf_trap calls.
    /// See: https://github.com/llvm/llvm-project/commit/ab391beb11f733b526b86f9df23734a34657d876
    #[clap(long)]
    allow_bpf_trap: bool,

    /// Add a directory to the library search path
    #[clap(short = 'L', number_of_values = 1)]
    libs: Vec<PathBuf>,

    /// Optimization level. 0-3, s, or z
    #[clap(short = 'O', default_value = "2")]
    optimize: Vec<CliOptLevel>,

    /// Export the symbols specified in the file `path`. The symbols must be separated by new lines
    #[clap(long, value_name = "path")]
    export_symbols: Option<PathBuf>,

    /// Try hard to unroll loops. Useful when targeting kernels that don't support loops
    #[clap(long)]
    unroll_loops: bool,

    /// Ignore `noinline`/`#[inline(never)]`. Useful when targeting kernels that don't support function calls
    #[clap(long)]
    ignore_inline_never: bool,

    /// Dump the final IR module to the given `path` before generating the code
    #[clap(long, value_name = "path")]
    dump_module: Option<PathBuf>,

    /// Extra command line arguments to pass to LLVM
    #[clap(long, value_name = "args", use_value_delimiter = true, action = clap::ArgAction::Append)]
    llvm_args: Vec<CString>,

    /// Disable passing --bpf-expand-memcpy-in-order to LLVM.
    #[clap(long)]
    disable_expand_memcpy_in_order: bool,

    /// Disable exporting memcpy, memmove, memset, memcmp and bcmp. Exporting
    /// those is commonly needed when LLVM does not manage to expand memory
    /// intrinsics to a sequence of loads and stores.
    #[clap(long)]
    disable_memory_builtins: bool,

    /// Input files. Can be object files or static libraries
    #[clap(required = true)]
    inputs: Vec<PathBuf>,

    /// Comma separated list of symbols to export. See also `--export-symbols`
    #[clap(long, value_name = "symbols", use_value_delimiter = true, action = clap::ArgAction::Append)]
    export: Vec<String>,

    /// Whether to treat LLVM errors as fatal.
    #[clap(long, action = clap::ArgAction::Set, default_value_t = true)]
    fatal_errors: bool,

    // The options below are for wasm-ld compatibility
    #[clap(long = "debug", hide = true)]
    _debug: bool,
}

fn main() -> anyhow::Result<()> {
    let args = env::args().map(|arg| {
        if arg == "-flavor" {
            "--flavor".to_string()
        } else {
            arg
        }
    });

    let CommandLine {
        cpu,
        output,
        btf,
        allow_bpf_trap,
        libs,
        optimize,
        export_symbols,
        unroll_loops,
        ignore_inline_never,
        dump_module,
        llvm_args,
        disable_expand_memcpy_in_order,
        disable_memory_builtins,
        inputs,
        export,
        fatal_errors,
        _debug,
    } = match Parser::try_parse_from(args) {
        Ok(command_line) => command_line,
        Err(err) => match err.kind() {
            ErrorKind::DisplayHelp | ErrorKind::DisplayVersion => {
                print!("{err}");
                return Ok(());
            }
            _ => return Err(err.into()),
        },
    };

    let export_symbols = export_symbols.map(fs::read_to_string).transpose()?;

    // TODO: the data is owned by this call frame; we could make this zero-alloc.
    let export_symbols = export_symbols
        .as_deref()
        .into_iter()
        .flat_map(str::lines)
        .map(str::to_owned)
        .chain(export)
        .map(Into::into)
        .collect();
    
    let optimize = match *optimize.as_slice() {
        [] => unreachable!("emit has a default value"),
        [.., CliOptLevel(optimize)] => optimize,
    };
    
    let mut linker = Linker::new(LinkerOptions {
        target: Some("bpf".to_string()),
        cpu,
        cpu_features: "".to_string(),
        inputs,
        output: output.clone(),
        output_type: OutputType::Object,
        libs,
        optimize,
        export_symbols,
        unroll_loops,
        ignore_inline_never,
        dump_module,
        llvm_args: llvm_args.into_iter().map(|cstring| cstring.into_string().unwrap_or_default()).collect(),
        disable_expand_memcpy_in_order,
        disable_memory_builtins,
        btf,
        allow_bpf_trap,
    });

    linker.link()?;

    if fatal_errors && linker.has_errors() {
        return Err(anyhow::anyhow!(
            "LLVM issued diagnostic with error severity"
        ));
    }

    let program = std::fs::read(&output).context("Failed to read bytecode")?;
    let bytecode = link_program(&program)
        .map_err(|e| anyhow::anyhow!("Link error: {}", e))?;
    let src_name = std::path::Path::new(&output)
        .file_stem()
        .and_then(|s| s.to_str())
        .unwrap_or("main");
    let output_path = std::path::Path::new(&output)
        .parent()
        .unwrap_or_else(|| std::path::Path::new("."))
        .join(format!("{}.so", src_name));
    std::fs::write(output_path, bytecode)?;

    Ok(())
}