shadow_rs/host/syscall/
formatter.rs

use std::any::TypeId;
use std::fmt::Display;
use std::marker::PhantomData;

use shadow_shim_helper_rs::emulated_time::EmulatedTime;
use shadow_shim_helper_rs::syscall_types::SyscallReg;
use shadow_shim_helper_rs::util::time::TimeParts;

use crate::core::worker::Worker;
use crate::host::memory_manager::MemoryManager;
use crate::host::process::Process;
use crate::host::syscall::types::{SyscallError, SyscallResult};
use crate::host::thread::ThreadId;

#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum FmtOptions {
    Standard,
    Deterministic,
}

// this type is required until we no longer need to access the format options from C
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
#[repr(C)]
pub enum StraceFmtMode {
    Off,
    Standard,
    Deterministic,
}

impl From<StraceFmtMode> for Option<FmtOptions> {
    fn from(x: StraceFmtMode) -> Self {
        match x {
            StraceFmtMode::Off => None,
            StraceFmtMode::Standard => Some(FmtOptions::Standard),
            StraceFmtMode::Deterministic => Some(FmtOptions::Deterministic),
        }
    }
}

impl From<Option<FmtOptions>> for StraceFmtMode {
    fn from(x: Option<FmtOptions>) -> Self {
        match x {
            None => StraceFmtMode::Off,
            Some(FmtOptions::Standard) => StraceFmtMode::Standard,
            Some(FmtOptions::Deterministic) => StraceFmtMode::Deterministic,
        }
    }
}

pub trait SyscallDisplay {
    fn fmt(
        &self,
        f: &mut std::fmt::Formatter<'_>,
        options: FmtOptions,
        mem: &MemoryManager,
    ) -> std::fmt::Result;
}

/// A syscall argument or return value. It implements [`Display`], and only reads memory and
/// converts types when being formatted.
pub struct SyscallVal<'a, T> {
    pub reg: SyscallReg,
    pub args: [SyscallReg; 6],
    options: FmtOptions,
    mem: &'a MemoryManager,
    _phantom: PhantomData<T>,
}

impl<'a, T> SyscallVal<'a, T> {
    pub fn new(
        reg: SyscallReg,
        args: [SyscallReg; 6],
        options: FmtOptions,
        mem: &'a MemoryManager,
    ) -> Self {
        Self {
            reg,
            args,
            options,
            mem,
            _phantom: PhantomData,
        }
    }
}

impl<'a, T> Display for SyscallVal<'a, T>
where
    SyscallVal<'a, T>: SyscallDisplay,
{
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        SyscallDisplay::fmt(self, f, self.options, self.mem)
    }
}

/// A marker type for indicating there are no types left in the syscall arguments.
#[derive(Default)]
pub struct NoArg {}

impl SyscallDisplay for SyscallVal<'_, NoArg> {
    fn fmt(
        &self,
        _f: &mut std::fmt::Formatter<'_>,
        _options: FmtOptions,
        _mem: &MemoryManager,
    ) -> std::fmt::Result {
        panic!("We shouldn't ever try to format this.");
    }
}

/// A formatting wrapper for six syscall arguments.
pub struct SyscallArgsFmt<'a, A = NoArg, B = NoArg, C = NoArg, D = NoArg, E = NoArg, F = NoArg> {
    a: SyscallVal<'a, A>,
    b: SyscallVal<'a, B>,
    c: SyscallVal<'a, C>,
    d: SyscallVal<'a, D>,
    e: SyscallVal<'a, E>,
    f: SyscallVal<'a, F>,
}

impl<'a, A, B, C, D, E, F> SyscallArgsFmt<'a, A, B, C, D, E, F>
where
    SyscallVal<'a, A>: Display,
    SyscallVal<'a, B>: Display,
    SyscallVal<'a, C>: Display,
    SyscallVal<'a, D>: Display,
    SyscallVal<'a, E>: Display,
    SyscallVal<'a, F>: Display,
{
    pub fn new(args: [SyscallReg; 6], options: FmtOptions, mem: &'a MemoryManager) -> Self {
        Self {
            a: SyscallVal::new(args[0], args, options, mem),
            b: SyscallVal::new(args[1], args, options, mem),
            c: SyscallVal::new(args[2], args, options, mem),
            d: SyscallVal::new(args[3], args, options, mem),
            e: SyscallVal::new(args[4], args, options, mem),
            f: SyscallVal::new(args[5], args, options, mem),
        }
    }
}

impl<'a, A, B, C, D, E, F> Display for SyscallArgsFmt<'a, A, B, C, D, E, F>
where
    SyscallVal<'a, A>: Display,
    SyscallVal<'a, B>: Display,
    SyscallVal<'a, C>: Display,
    SyscallVal<'a, D>: Display,
    SyscallVal<'a, E>: Display,
    SyscallVal<'a, F>: Display,
    A: 'static,
    B: 'static,
    C: 'static,
    D: 'static,
    E: 'static,
    F: 'static,
{
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let args: [&dyn Display; 6] = [&self.a, &self.b, &self.c, &self.d, &self.e, &self.f];

        let types: [TypeId; 6] = [
            TypeId::of::<A>(),
            TypeId::of::<B>(),
            TypeId::of::<C>(),
            TypeId::of::<D>(),
            TypeId::of::<E>(),
            TypeId::of::<F>(),
        ];

        let mut first = true;
        for (arg, arg_type) in args.iter().zip(types) {
            if arg_type == TypeId::of::<NoArg>() {
                // the user didn't override this generic type, so it and any following types/args
                // should not be shown
                break;
            }

            if first {
                write!(f, "{arg}")?;
                first = false;
            } else {
                write!(f, ", {arg}")?;
            }
        }

        Ok(())
    }
}

/// A formatting wrapper for the syscall result.
pub struct SyscallResultFmt<'a, RV>
where
    SyscallVal<'a, RV>: Display,
    RV: std::fmt::Debug,
{
    rv: &'a SyscallResult,
    args: [SyscallReg; 6],
    options: FmtOptions,
    mem: &'a MemoryManager,
    _phantom: PhantomData<RV>,
}

impl<'a, RV> SyscallResultFmt<'a, RV>
where
    SyscallVal<'a, RV>: Display,
    RV: std::fmt::Debug,
{
    pub fn new(
        rv: &'a SyscallResult,
        args: [SyscallReg; 6],
        options: FmtOptions,
        mem: &'a MemoryManager,
    ) -> Self {
        Self {
            rv,
            args,
            options,
            mem,
            _phantom: PhantomData,
        }
    }
}

impl<'a, RV> Display for SyscallResultFmt<'a, RV>
where
    SyscallVal<'a, RV>: Display,
    RV: std::fmt::Debug,
{
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self.rv {
            SyscallResult::Ok(x) => {
                let rv = SyscallVal::<'_, RV>::new(*x, self.args, self.options, self.mem);
                write!(f, "{rv}")
            }
            SyscallResult::Err(SyscallError::Failed(failed)) => {
                let errno = failed.errno;
                let rv = SyscallReg::from(errno.to_negated_i64());
                let rv = SyscallVal::<'_, RV>::new(rv, self.args, self.options, self.mem);
                write!(f, "{rv} ({errno})")
            }
            SyscallResult::Err(SyscallError::Native) => {
                write!(f, "<native>")
            }
            SyscallResult::Err(SyscallError::Blocked(_)) => {
                write!(f, "<blocked>")
            }
        }
    }
}

/// Format and write the syscall.
pub fn write_syscall(
    mut writer: impl std::io::Write,
    sim_time: &EmulatedTime,
    tid: ThreadId,
    name: impl Display,
    args: impl Display,
    rv: impl Display,
) -> std::io::Result<()> {
    let sim_time = sim_time.duration_since(&EmulatedTime::SIMULATION_START);
    let sim_time = TimeParts::from_nanos(sim_time.as_nanos());
    let sim_time = sim_time.fmt_hr_min_sec_nano();

    writeln!(writer, "{sim_time} [tid {tid}] {name}({args}) = {rv}")
}

/// For logging unknown syscalls.
pub fn log_syscall_simple(
    proc: &Process,
    logging_mode: Option<FmtOptions>,
    tid: ThreadId,
    syscall_name: &str,
    args_str: &str,
    result: &SyscallResult,
) -> std::io::Result<()> {
    let Some(logging_mode) = logging_mode else {
        // logging was disabled
        return Ok(());
    };

    let args = [SyscallReg::from(0i64); 6];
    let mem = proc.memory_borrow();
    let rv = SyscallResultFmt::<libc::c_long>::new(result, args, logging_mode, &mem);

    proc.with_strace_file(|file| {
        let time = Worker::current_time();

        if let Some(time) = time {
            write_syscall(file, &time, tid, syscall_name, args_str, rv)
        } else {
            log::warn!("Could not log syscall {syscall_name} with time {time:?}");
            Ok(())
        }
    })
    .unwrap_or(Ok(()))?;

    Ok(())
}

#[cfg(test)]
mod test {
    use std::process::Command;

    use linux_api::posix_types::Pid;
    use shadow_shim_helper_rs::syscall_types::SyscallArgs;

    use super::*;

    #[test]
    // can't call foreign function: gnu_get_libc_version
    #[cfg_attr(miri, ignore)]
    fn test_no_args() {
        let args = SyscallArgs {
            number: 100,
            args: [0u32.into(); 6],
        };

        // 10 seconds should be long enough to keep the process alive while the following code runs
        let mut proc = Command::new("sleep").arg(10.to_string()).spawn().unwrap();
        let pid = Pid::from_raw(proc.id().try_into().unwrap()).unwrap();

        let mem = unsafe { MemoryManager::new(pid) };

        // make sure that we can construct a `SyscallArgsFmt` with no generic types
        let _syscall_args = <SyscallArgsFmt>::new(args.args, FmtOptions::Standard, &mem);

        proc.kill().unwrap();
        proc.wait().unwrap();
    }
}
shadow_rs/host/syscall/formatter.rs

shadow_rs/host/syscall/
formatter.rs
