sbpf-linker 0.1.9

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

use bpf_linker::{
    Cpu, Linker, LinkerInput, LinkerOptions, OptLevel, OutputType,
};
use clap::{
    Parser,
    builder::{PathBufValueParser, TypedValueParser as _},
    error::ErrorKind,
};
use thiserror::Error;
use tracing::{Level, info};
use tracing_subscriber::{EnvFilter, fmt::MakeWriter, prelude::*};
use tracing_tree::HierarchicalLayer;

use sbpf_linker::{SbpfLinkerError, 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),

    #[error("SBPF Linker Error. Error detail: ({0}).")]
    SbpfLinkerError(#[from] SbpfLinkerError),
    #[error("Program Write Error. Error detail: ({msg}).")]
    ProgramWriteError { msg: 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(Copy, Clone, Debug)]
struct CliOutputType(OutputType);

impl FromStr for CliOutputType {
    type Err = CliError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Ok(Self(match s {
            "llvm-bc" => OutputType::Bitcode,
            "asm" => OutputType::Assembly,
            "llvm-ir" => OutputType::LlvmAssembly,
            "obj" => OutputType::Object,
            _ => return Err(CliError::InvalidOutputType(s.to_string())),
        }))
    }
}

fn parent_and_file_name(p: PathBuf) -> anyhow::Result<(PathBuf, PathBuf)> {
    let mut comps = p.components();
    let file_name = comps
        .next_back()
        .map(|p| match p {
            Component::Normal(p) => Ok(p),
            p => Err(anyhow::anyhow!("unexpected path component {:?}", p)),
        })
        .transpose()?
        .ok_or_else(|| anyhow::anyhow!("unexpected empty path"))?;
    let parent = comps.as_path();
    Ok((parent.to_path_buf(), Path::new(file_name).to_path_buf()))
}

#[derive(Debug, Parser)]
#[command(version)]
struct CommandLine {
    /// LLVM target triple. When not provided, the target is inferred from the inputs
    #[clap(long)]
    target: Option<CString>,

    /// Target BPF processor. Can be one of `generic`, `probe`, `v1`, `v2`, `v3`
    /// This will be ignored in sbpf linker since we want to default `cpu` to `v2` but with rustc always passing a `cpu` value
    /// We decide to add one more flag to override it
    #[clap(long, default_value = "generic")]
    cpu: Cpu,

    /// Override the target-cpu attribute to expose the desired CPU features to bpf-linker
    #[clap(long, default_value = "v2")]
    override_cpu_flag: Option<Cpu>,

    /// Enable or disable CPU features. The available features are: alu32, dummy, dwarfris.
    /// LLVM 22 builds also support allows-misaligned-mem-access. Use +feature to enable a
    /// feature, or -feature to disable it. For example
    /// --cpu-features=+allows-misaligned-mem-access,+alu32,-dwarfris
    #[clap(long, value_name = "features", default_value = "")]
    cpu_features: CString,

    /// Write output to <output>
    #[clap(short, long)]
    output: PathBuf,

    /// Output type. Can be one of `llvm-bc`, `asm`, `llvm-ir`, `obj`
    #[clap(long, default_value = "obj")]
    emit: Vec<CliOutputType>,

    /// Emit BTF information. Can get DWARF symbols only if BTF is enabled and if requested from `rustc` with `-C debuginfo=N`
    #[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>,

    /// Output logs to the given `path`
    #[clap(
        long,
        value_name = "path",
        value_parser = PathBufValueParser::new().try_map(parent_and_file_name),
    )]
    log_file: Option<(PathBuf, PathBuf)>,

    /// Set the log level. If not specified, no logging is used. Can be one of
    /// `error`, `warn`, `info`, `debug`, `trace`.
    #[clap(long, value_name = "level")]
    log_level: Option<Level>,

    /// 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, default_value_t = true, hide = true, action = clap::ArgAction::Set)]
    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,

    /// Strips the `lib` prefix from the output file and places it in the `target/deploy` directory for deployment
    #[clap(long, default_value_t = true, hide = true, action = clap::ArgAction::Set)]
    deploy: bool,
}

/// Returns a [`HierarchicalLayer`](tracing_tree::HierarchicalLayer) for the
/// given `writer`.
fn tracing_layer<W>(writer: W) -> HierarchicalLayer<W>
where
    W: for<'writer> MakeWriter<'writer> + 'static,
{
    const TRACING_IDENT: usize = 2;
    HierarchicalLayer::new(TRACING_IDENT)
        .with_indent_lines(true)
        .with_writer(writer)
}

fn process_cli_options<I>(args: I) -> anyhow::Result<CommandLine>
where
    I: Iterator<Item = String>,
{
    let cli: CommandLine = match Parser::try_parse_from(args) {
        Ok(cli) => cli,
        Err(err) => match err.kind() {
            ErrorKind::DisplayHelp | ErrorKind::DisplayVersion => {
                print!("{err}");
                return Err(err.into());
            }
            _ => return Err(err.into()),
        },
    };
    let mut cpu_features = cli.cpu_features;

    let misalignment_bytes = b"allows-misaligned-mem-access";
    if !cpu_features
        .as_bytes()
        .windows(misalignment_bytes.len())
        .any(|w| w == misalignment_bytes)
    {
        let mut bytes = cpu_features.into_bytes();
        if !bytes.is_empty() {
            bytes.push(b',');
        }

        bytes.extend_from_slice(b"+allows-misaligned-mem-access");
        cpu_features = CString::new(bytes).unwrap();
    }

    let mut llvm_args = cli.llvm_args;
    if !llvm_args
        .iter()
        .any(|arg| arg.as_bytes().starts_with(b"-bpf-stack-size"))
    {
        llvm_args.push(CString::new("-bpf-stack-size=4096").unwrap());
    }

    let cpu = cli.override_cpu_flag.unwrap();

    Ok(CommandLine {
        target: cli.target,
        override_cpu_flag: cli.override_cpu_flag,
        cpu,
        cpu_features,
        output: cli.output,
        emit: cli.emit,
        btf: cli.btf,
        allow_bpf_trap: cli.allow_bpf_trap,
        _libs: cli._libs,
        optimize: cli.optimize,
        export_symbols: cli.export_symbols,
        log_file: cli.log_file,
        log_level: cli.log_level,
        unroll_loops: cli.unroll_loops,
        ignore_inline_never: cli.ignore_inline_never,
        dump_module: cli.dump_module,
        llvm_args,
        disable_expand_memcpy_in_order: cli.disable_expand_memcpy_in_order,
        disable_memory_builtins: cli.disable_memory_builtins,
        inputs: cli.inputs,
        export: cli.export,
        fatal_errors: cli.fatal_errors,
        _debug: cli._debug,
        deploy: cli.deploy,
    })
}

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

    let cli = process_cli_options(args)?;

    let CommandLine {
        cpu,
        cpu_features,
        target,
        output,
        btf,
        allow_bpf_trap,
        export_symbols,
        log_file,
        log_level,
        llvm_args,
        unroll_loops,
        ignore_inline_never,
        dump_module,
        disable_expand_memcpy_in_order,
        disable_memory_builtins,
        inputs,
        export,
        fatal_errors,
        deploy,
        ..
    } = cli;

    let _guard = {
        let filter = EnvFilter::from_default_env();
        let filter = match log_level {
            None => filter,
            Some(log_level) => filter.add_directive(log_level.into()),
        };
        let subscriber_registry = tracing_subscriber::registry().with(filter);
        match log_file {
            Some((parent, file_name)) => {
                let file_appender =
                    tracing_appender::rolling::never(parent, file_name);
                let (non_blocking, guard) =
                    tracing_appender::non_blocking(file_appender);
                let subscriber = subscriber_registry
                    .with(tracing_layer(io::stdout))
                    .with(tracing_layer(non_blocking));
                tracing::subscriber::set_global_default(subscriber)?;
                Some(guard)
            }
            None => {
                let subscriber =
                    subscriber_registry.with(tracing_layer(io::stderr));
                tracing::subscriber::set_global_default(subscriber)?;
                None
            }
        }
    };

    info!("command line: {:?}", env::args().collect::<Vec<_>>().join(" "));

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

    let export_symbols = export_symbols
        .as_deref()
        .into_iter()
        .flat_map(str::lines)
        .chain(export.iter().map(String::as_str));

    let output_type = match *cli.emit.as_slice() {
        [] => unreachable!("emit has a default value"),
        [CliOutputType(output_type), ..] => output_type,
    };

    let optimize = match *cli.optimize.as_slice() {
        [] => unreachable!("optimize has a default value"),
        [.., CliOptLevel(optimize)] => optimize,
    };

    let mut linker = Linker::new(LinkerOptions {
        target,
        cpu,
        cpu_features,
        optimize,
        unroll_loops,
        ignore_inline_never,
        llvm_args,
        disable_expand_memcpy_in_order,
        disable_memory_builtins,
        btf,
        allow_bpf_trap,
    });

    if let Some(path) = dump_module {
        linker.set_dump_module_path(path);
    }

    let inputs =
        inputs.iter().map(|p| LinkerInput::new_from_file(p.as_path()));

    linker.link_to_file(inputs, &output, output_type, export_symbols)?;

    print!("{:?}", output);

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

    let program = std::fs::read(&output).unwrap();
    let bytecode = link_program(&program)?;

    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!("{src_name}.so"));
    std::fs::write(&output_path, &bytecode)
        .map_err(|e| CliError::ProgramWriteError { msg: e.to_string() })?;

    // Remove "lib" from the artifact and put it in target/deploy
    if deploy {
        let final_object = src_name.strip_prefix("lib").unwrap_or(src_name);
        let deploy_path = PathBuf::from("target").join("deploy");
        std::fs::create_dir_all(&deploy_path).map_err(|e| {
            CliError::ProgramWriteError {
                msg: format!("failed to create deploy directory: {e}"),
            }
        })?;
        let deploy_file = deploy_path.join(format!("{final_object}.so"));
        std::fs::write(&deploy_file, &bytecode).map_err(|e| {
            CliError::ProgramWriteError {
                msg: format!("failed to write deploy artifact: {e}"),
            }
        })?;
    }

    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_export_input_args() {
        let args = [
            "sbpf-linker",
            "--export",
            "foo",
            "--export",
            "bar",
            "symbols.o",
            "rcgu.o",
            "-L",
            "target/debug/deps",
            "-L",
            "target/debug",
            "-L",
            "/home/foo/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib",
            "-o",
            "/tmp/bin.s",
            "--target=bpf",
            "--emit=asm",
        ]
        .into_iter()
        .map(|s| s.to_string());
        let CommandLine {
            cpu,
            disable_expand_memcpy_in_order,
            deploy,
            cpu_features,
            llvm_args,
            ..
        } = process_cli_options(args).unwrap();
        assert!(matches!(cpu, Cpu::V2));
        assert!(disable_expand_memcpy_in_order);
        assert!(deploy);

        assert_eq!(cpu_features.to_bytes(), b"+allows-misaligned-mem-access");
        assert!(
            llvm_args
                .iter()
                .any(|a| a.to_str().unwrap() == "-bpf-stack-size=4096")
        );
    }

    #[test]
    fn test_explicit_overrides_of_default_flags() {
        let args = [
            "sbpf-linker",
            "input.o",
            "-o",
            "/tmp/bin.so",
            "--override-cpu-flag=v3",
            "--emit=llvm-ir",
            "--deploy=false",
            "--fatal-errors=false",
            "--disable-expand-memcpy-in-order=false",
        ]
        .into_iter()
        .map(|s| s.to_string());
        let CommandLine {
            cpu,
            emit,
            deploy,
            fatal_errors,
            disable_expand_memcpy_in_order,
            output,
            ..
        } = process_cli_options(args).unwrap();

        assert!(matches!(cpu, Cpu::V3));
        assert_eq!(emit.len(), 1);
        assert!(matches!(emit[0], CliOutputType(OutputType::LlvmAssembly)));
        assert!(!deploy);
        assert!(!fatal_errors);
        assert!(!disable_expand_memcpy_in_order);
        assert_eq!(output, PathBuf::from("/tmp/bin.so"));
    }

    #[test]
    fn test_boolean_and_optional_flags() {
        let args = [
            "sbpf-linker",
            "input.o",
            "-o",
            "/tmp/bin.o",
            "--target=bpfel-unknown-none",
            "--btf",
            "--allow-bpf-trap",
            "--unroll-loops",
            "--override-cpu-flag=v1",
            "--ignore-inline-never",
            "--disable-memory-builtins",
            "--log-level=debug",
            "--export-symbols=/tmp/exports.txt",
            "--dump-module=/tmp/module.ll",
        ]
        .into_iter()
        .map(|s| s.to_string());
        let CommandLine {
            cpu,
            target,
            btf,
            allow_bpf_trap,
            unroll_loops,
            ignore_inline_never,
            disable_memory_builtins,
            log_level,
            export_symbols,
            dump_module,
            inputs,
            ..
        } = process_cli_options(args).unwrap();

        assert_eq!(
            target.as_deref().map(|t| t.to_bytes()),
            Some(b"bpfel-unknown-none".as_slice())
        );
        assert!(btf);
        assert!(allow_bpf_trap);
        assert!(unroll_loops);
        assert!(matches!(cpu, Cpu::V1));
        assert!(ignore_inline_never);
        assert!(disable_memory_builtins);
        assert_eq!(log_level, Some(Level::DEBUG));
        assert_eq!(export_symbols, Some(PathBuf::from("/tmp/exports.txt")));
        assert_eq!(dump_module, Some(PathBuf::from("/tmp/module.ll")));
        assert_eq!(inputs, vec![PathBuf::from("input.o")]);
    }

    #[test]
    fn test_misalignment_feature_not_duplicated_when_already_present() {
        let args = [
            "sbpf-linker",
            "input.o",
            "-o",
            "/tmp/bin.o",
            "--cpu-features=-allows-misaligned-mem-access,+alu32",
        ]
        .into_iter()
        .map(|s| s.to_string());
        let CommandLine { cpu_features, .. } =
            process_cli_options(args).unwrap();

        assert_eq!(
            cpu_features.to_bytes(),
            b"-allows-misaligned-mem-access,+alu32"
        );
    }

    #[test]
    fn test_override_cpu() {
        let args = [
            "sbpf-linker",
            "input.o",
            "-o",
            "/tmp/bin.o",
            "--cpu=v1",
            "--override-cpu-flag=v3",
        ]
        .into_iter()
        .map(|s| s.to_string());
        let CommandLine { cpu, .. } = process_cli_options(args).unwrap();
        assert!(matches!(cpu, Cpu::V3));
    }

    #[test]
    fn test_cpu_flag_is_ignored_without_override() {
        let args = ["sbpf-linker", "input.o", "-o", "/tmp/bin.o", "--cpu=v3"]
            .into_iter()
            .map(|s| s.to_string());
        let CommandLine { cpu, .. } = process_cli_options(args).unwrap();
        assert!(matches!(cpu, Cpu::V2));
    }
}