processkit 2.3.1

//! Platform job layer — one `imp::Job` per target, all exposing the same shape.
//!
//! A `Job` is the kernel object that contains a process tree so the whole tree
//! dies with its owner:
//!
//! - **Windows** — a [Job Object] with `JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE`.
//! - **Linux** — a [cgroup v2] killed via `cgroup.kill`, falling back to a POSIX
//!   process group when no writable cgroup is available.
//! - **macOS / the BSDs** — a POSIX process group (`killpg` the tree on drop);
//!   no cgroups or Job Objects exist there. See [`pgroup`].
//!
//! Only Unix and Windows are supported; other targets fail to compile (see the
//! `compile_error!` below).
//!
//! [Job Object]: https://learn.microsoft.com/windows/win32/procthread/job-objects
//! [cgroup v2]: https://docs.kernel.org/admin-guide/cgroup-v2.html

use std::io;
use std::time::Duration;

use tokio::process::{Child, Command};

use crate::Mechanism;
#[cfg(feature = "process-control")]
use crate::Signal;
#[cfg(feature = "limits")]
use crate::limits::ResourceLimits;
#[cfg(feature = "process-control")]
use crate::member::MemberInfo;
#[cfg(feature = "stats")]
use crate::stats::ProcessGroupStats;

/// The raw `SIGTERM` signal number — the default signal for the graceful
/// teardown tier (`graceful_shutdown` and the run-level graceful timeout).
/// Defined cross-platform; only *used* on unix (Windows' graceful tier ignores
/// the signal and kills the job atomically).
#[cfg(unix)]
pub(crate) const SIGTERM_RAW: i32 = libc::SIGTERM;
#[cfg(not(unix))]
pub(crate) const SIGTERM_RAW: i32 = 15;

// The generation-guarded "don't kill on Drop" latch. Split into its own module so
// the standalone loom harness (`loom/`) can `#[path]`-include just that pure core
// and model-check the spawn/shutdown re-arm race (T-079) — see `skip_drop_kill.rs`
// and `crate::sync`.
mod skip_drop_kill;
pub(crate) use skip_drop_kill::SkipDropKill;

/// Per-process resource metrics sampled from the OS.
#[cfg(feature = "stats")]
#[derive(Debug, Clone, Copy, Default)]
pub(crate) struct ProcMetrics {
    pub cpu_time: Option<Duration>,
    pub peak_memory_bytes: Option<u64>,
}

/// An opaque snapshot of a process's OS-reported **start identity** — a start
/// timestamp captured once so a later metrics read can prove a pid still names the
/// *same* process instance, not one that recycled the number after the original
/// was reaped. Only ever compared for equality, never interpreted: the units are
/// platform-specific — Windows uses the process-creation `FILETIME` (100 ns units)
/// and Linux uses `/proc/<pid>/stat` field 22 (`starttime`, clock ticks since
/// boot); the POSIX fallback (macOS/BSD) reports none. This is the per-process
/// analogue of the pgroup backend's start-time identity token (see
/// [`pgroup::read_identity`](crate::sys::pgroup)); it exists to keep a pid-reuse
/// race from folding an unrelated process's CPU/memory into a sample.
#[cfg(feature = "stats")]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) struct ProcIdentity(u64);

// Constructed and read only by the Linux (`/proc` starttime) and Windows
// (creation `FILETIME`) backends; the POSIX fallback (macOS/BSD, `unix.rs`)
// reports no identity and ignores the anchor, leaving both associated items
// unused there — allow it on exactly that target rather than deleting methods
// the other two backends need (mirrors the `SpawnOptions` field pattern above).
#[cfg(feature = "stats")]
#[cfg_attr(all(unix, not(target_os = "linux")), allow(dead_code))]
impl ProcIdentity {
    /// Wrap a platform-specific raw start-time token (constructed only by the
    /// platform backend that knows its units).
    pub(crate) fn from_raw(raw: u64) -> Self {
        Self(raw)
    }

    /// The raw token, for a platform backend's own read-time equality re-check.
    pub(crate) fn raw(self) -> u64 {
        self.0
    }
}

/// Sample CPU time and peak memory for a single process by pid, but only when its
/// current OS identity still matches `expected` (see [`ProcIdentity`]). If the pid
/// was recycled by an unrelated process — its start identity no longer matching —
/// the read yields defaults (all `None`) rather than that stranger's counters, so
/// a sample can never be misattributed after PID reuse. `expected == None` skips
/// the check (no identity was captured, or the platform can't report one),
/// preserving the number-only behavior with no weakening. Returns defaults if the
/// process is gone or the platform can't report.
#[cfg(feature = "stats")]
pub(crate) fn process_metrics(pid: u32, expected: Option<ProcIdentity>) -> ProcMetrics {
    imp::process_metrics(pid, expected)
}

/// Capture the OS start-time identity anchor of the *live* process at `pid`, or
/// `None` if the platform can't report one (macOS/BSD) or the process is already
/// gone. Captured once — at spawn for the per-process sampler, or when a cgroup
/// member is first read for a group-stats fold — and handed back to
/// [`process_metrics`] so a later reading taken against a recycled pid is
/// rejected rather than folded in.
#[cfg(feature = "stats")]
pub(crate) fn process_identity(pid: u32) -> Option<ProcIdentity> {
    imp::process_identity(pid)
}

// Shared POSIX process-group backend for both the Linux fallback and macOS/BSD.
#[cfg(unix)]
pub(crate) mod pgroup;

// Shared `/proc/<pid>/stat` parser for the Linux/Android backends. The pgroup
// liveness identity token (`pgroup::read_identity`) and the Linux per-process
// metrics sampler (`imp::process_metrics` / `process_identity`) all pull the same
// start-time field from the same file with the same "skip past the comm's last
// ')', then field 22 = whitespace index 19" convention; centralizing it here keeps
// that convention from drifting between them and silently weakening the
// anti-pid-reuse identity gate.
#[cfg(any(target_os = "linux", target_os = "android"))]
pub(crate) mod procfs;

// Shared graceful-shutdown escalation driver. The whole-tree
// signal → poll → escalate loop ([`graceful::run`]) and its [`GracefulTarget`]
// trait are cross-platform: both unix backends drive it (SIGTERM → grace →
// SIGKILL), and the Windows Job Object drives it too for the opt-in
// console-CTRL graceful path (CTRL_BREAK → grace → `TerminateJobObject`). The
// single-child kill-and-reap primitive ([`graceful::run_pid`]/[`PidTarget`]/
// [`UnixChild`]) stays unix-only — it leans on `PidGate`/`libc` and drives the
// shared-group streaming-timeout teardown from `crate::running`. `pub(crate)`
// so both are reachable from those callers.
pub(crate) mod graceful;

// The linearizable pid gate: serializes every raw direct-child kill a detached
// teardown watchdog issues against the reap that frees (and lets the OS recycle)
// the pid. Cross-platform (the state machine is platform-agnostic; only the kill
// syscall behind `force_kill` differs); driven by `crate::running`.
pub(crate) mod pid_gate;

/// Per-spawn knobs that must reach the platform backend (the
/// `tokio::process::Command` can't carry them: creation flags have no getter,
/// and the pgroup backend must know about `setsid` *before* it sets a process
/// group).
#[derive(Debug, Clone, Copy, Default)]
pub(crate) struct SpawnOptions {
    /// The command carries a `setsid()` pre-exec hook: the pgroup backend must
    /// skip its `process_group(0)` (std applies setpgid before pre-exec hooks,
    /// and `setsid` fails `EPERM` for a process that is already a group
    /// leader); the new session's group (pgid == pid) is tracked instead.
    /// Only unix backends consult it — non-unix launches reject `setsid`
    /// upstream before a `SpawnOptions` is ever built.
    #[cfg_attr(not(unix), allow(dead_code))]
    pub setsid: bool,
    /// Extra Windows creation flags (e.g. `CREATE_NO_WINDOW`), OR'd with the
    /// containment-required `CREATE_SUSPENDED` on the Windows backend. Only
    /// the Windows backend consults it — elsewhere the flag is a documented
    /// no-op.
    #[cfg_attr(not(windows), allow(dead_code))]
    pub creation_flags: u32,
    /// Spawn the direct child in its own console process group
    /// (`CREATE_NEW_PROCESS_GROUP`) so the opt-in graceful teardown can address
    /// it with `GenerateConsoleCtrlEvent(CTRL_BREAK_EVENT, pid)` before the
    /// grace window (see [`Command::windows_graceful_ctrl_break`](crate::Command::windows_graceful_ctrl_break)).
    /// Only the Windows backend consults it — elsewhere it is a documented
    /// no-op (Unix graceful teardown already has a real signal tier).
    #[cfg_attr(not(windows), allow(dead_code))]
    pub windows_new_process_group: bool,
    /// Arm `PR_SET_PDEATHSIG(SIGKILL)` on the direct child. Only the Linux
    /// backend consults it — Windows already kills the tree when the parent
    /// dies (job handle closes), macOS/BSD have no equivalent; both are
    /// documented on [`Command::kill_on_parent_death`](crate::Command::kill_on_parent_death).
    #[cfg_attr(not(target_os = "linux"), allow(dead_code))]
    pub kill_on_parent_death: bool,
}

// processkit supports only Unix and Windows: it relies on `tokio::process` and
// on OS job / process-group primitives (cgroups, setpgid, Job Objects) that have
// no equivalent on bare targets like wasm. Fail with a clear message rather than
// a cascade of missing-symbol errors from a containment-less fallback.
#[cfg(not(any(unix, windows)))]
compile_error!(
    "processkit supports only Unix and Windows targets — it requires tokio::process \
     and OS job/process-group primitives unavailable on this target."
);

// Exactly one platform module is compiled per target. Each defines an `imp::Job`
// with the same inherent methods plus a kill-on-close `Drop`.
#[cfg_attr(windows, path = "windows.rs")]
#[cfg_attr(target_os = "linux", path = "linux.rs")]
#[cfg_attr(all(unix, not(target_os = "linux")), path = "unix.rs")]
mod imp;

/// A handle to an OS job owning a tree of child processes.
///
/// Dropping the `Job` hard-kills every process still inside it, so an exiting or
/// panicking owner never leaks subprocesses.
pub(crate) struct Job(imp::Job);

impl Job {
    /// Create a fresh, empty job, applying any resource `limits`.
    ///
    /// Errors if `limits` requests a cap the target's mechanism can't enforce (no
    /// cgroup/Job Object, or a Linux cgroup whose controllers can't be enabled —
    /// see `ResourceLimits` for the cgroup-v2 real-root requirement).
    #[cfg(feature = "limits")]
    pub(crate) fn new(limits: &ResourceLimits) -> io::Result<Self> {
        imp::Job::new(limits).map(Job)
    }

    /// Create a fresh, empty job.
    #[cfg(not(feature = "limits"))]
    pub(crate) fn new() -> io::Result<Self> {
        imp::Job::new().map(Job)
    }

    /// Spawn `cmd` as a member of this job, honoring the per-spawn `opts`.
    ///
    /// The child — and any process it later spawns — belongs to the job and is
    /// reaped when the job is killed or dropped.
    pub(crate) fn spawn(&self, cmd: &mut Command, opts: &SpawnOptions) -> io::Result<Child> {
        self.0.spawn(cmd, opts)
    }

    /// Attach an already-started child to this job.
    ///
    /// Only the child itself is moved into the job; descendants it already
    /// spawned keep their original containment.
    #[cfg(feature = "process-control")]
    pub(crate) fn adopt(&self, child: &Child) -> io::Result<()> {
        self.0.adopt(child)
    }

    /// Immediately hard-kill every process in the job. Idempotent.
    pub(crate) fn kill_all(&self) -> io::Result<()> {
        self.0.kill_all()
    }

    /// Broadcast `sig` to every process in the job. On Windows only
    /// [`Signal::Kill`] is deliverable (job terminate); other signals yield
    /// `ErrorKind::Unsupported`.
    #[cfg(feature = "process-control")]
    pub(crate) fn signal(&self, sig: Signal) -> io::Result<()> {
        self.0.signal(sig)
    }

    /// Freeze the whole tree (cgroup.freeze / SIGSTOP / per-thread suspend).
    #[cfg(feature = "process-control")]
    pub(crate) fn suspend(&self) -> io::Result<()> {
        self.0.suspend()
    }

    /// Thaw a tree frozen by [`suspend`](Self::suspend).
    #[cfg(feature = "process-control")]
    pub(crate) fn resume(&self) -> io::Result<()> {
        self.0.resume()
    }

    /// Snapshot the live member pids (whole tree on Windows/cgroup; tracked
    /// group leaders on the POSIX fallback).
    #[cfg(feature = "process-control")]
    pub(crate) fn members(&self) -> io::Result<Vec<u32>> {
        self.0.members()
    }

    /// Snapshot the live members enriched with ppid / image name / start time
    /// (same member set as [`members`](Self::members); honest `Option` where a
    /// field is unavailable, vanished members skipped).
    #[cfg(feature = "process-control")]
    pub(crate) fn members_info(&self) -> io::Result<Vec<MemberInfo>> {
        self.0.members_info()
    }

    /// Ask the tree to exit, then escalate.
    ///
    /// On Unix: send `signal` (typically `SIGTERM`), wait up to `timeout` for the
    /// members to leave, then `SIGKILL` survivors when `escalate` is set.
    ///
    /// On Windows the default (no opt-in) job kill is atomic, so `signal` and
    /// `timeout` are **both ignored**: `escalate = true` kills the tree immediately
    /// (equivalent to [`kill_all`](Self::kill_all)), and `escalate = false` leaves
    /// survivors alive (`Drop` then closes the handle without `KILL_ON_JOB_CLOSE`).
    /// Without a soft signal there is no way to *trigger* a graceful exit, so it
    /// does not wait out the grace `timeout` as a drain window either — doing so
    /// would only delay the kill of a child that ignores the (absent) signal by the
    /// whole grace.
    ///
    /// **Opt-in Windows path.** When a direct child was spawned with
    /// [`SpawnOptions::windows_new_process_group`] (via
    /// [`Command::windows_graceful_ctrl_break`](crate::Command::windows_graceful_ctrl_break)),
    /// the Job records it as a console-CTRL leader and this drives the *same*
    /// shared [`graceful::run`](crate::sys::graceful::run) loop the unix backends
    /// use: `GenerateConsoleCtrlEvent(CTRL_BREAK_EVENT, pid)` to each leader, poll
    /// the job's active-process count up to `timeout`, then `TerminateJobObject`
    /// survivors when `escalate` is set (or spare them when not). `signal` is still
    /// ignored — Windows delivers CTRL_BREAK, not a POSIX signal. The console event
    /// only reaches children that share this process's console; a child spawned
    /// [`create_no_window`](crate::Command::create_no_window)/`DETACHED_PROCESS`
    /// cannot receive it and simply rides the grace to the `TerminateJobObject`
    /// fallback.
    ///
    /// `escalate = false` survivor-sparing is **best-effort on Windows**: `Drop`
    /// clears `KILL_ON_JOB_CLOSE` before closing the handle, but if that
    /// `SetInformationJobObject` call fails the handle close still kills the tree
    /// (a deliberate fail-safe — an unexpected kill is preferred over ambiguous
    /// orphaning). On Unix the spare is unconditional once the flag is set.
    pub(crate) async fn graceful_shutdown(
        &self,
        signal: i32,
        timeout: Duration,
        escalate: bool,
    ) -> io::Result<()> {
        self.0.graceful_shutdown(signal, timeout, escalate).await
    }

    /// Snapshot the group's resource usage.
    #[cfg(feature = "stats")]
    pub(crate) fn stats(&self) -> io::Result<ProcessGroupStats> {
        self.0.stats()
    }

    /// The containment mechanism actually in effect.
    pub(crate) fn mechanism(&self) -> Mechanism {
        self.0.mechanism()
    }
}