cloudfox-coreshift-core 2.31.0

// READ-ONLY research spike (Track A): empirically verify the CLONE_NEWPID
// signal-back-isolation hypothesis against the actual target device
// (kernel 5.10.264-android12, MT6789, bionic, root via KernelSU).
//
// Does NOT modify or depend on production spawn code. It re-implements the
// exact child-setup ORDER observed in `src/spawn/fork.rs::child_entry`
// (pty -> setsid -> TIOCSCTTY -> [seccomp]) and the exact session-containment
// BPF program, using raw syscalls only.
//
// Tests:
//   T0  privilege precondition + clone3(CLONE_NEWPID) feasibility
//   P1a baseline: child WITHOUT CLONE_NEWPID can getppid()/signal the parent
//   P1b namespaced: child cannot resolve or signal the parent's real pid
//   P2a pty/setsid/TIOCSCTTY still work inside the new pid namespace
//   P2b stdio drain crosses the namespace boundary byte-for-byte
//   P2c seccomp chaining still works in the child
//   P2d waitpid from the daemon namespace reaps the namespaced child
//   P3a parent kills the namespaced child by direct pid
//   P3b parent kills the namespaced session by kill(-pgid) (kill-totality)

use std::io::Write;
use std::os::unix::io::RawFd;
use std::time::{Duration, Instant};

const LOG: &str = "/data/local/tmp/newpid_probe.log";

const SYS_CLONE3: libc::c_long = 435; // aarch64
const SYS_CLONE: libc::c_long = 220; // aarch64 fallback
// CORRECTED (2026-08-18, Phase 0 evidence re-baseline): this was 0x0000_2000,
// which is CLONE_PTRACE (kernel include/uapi/linux/sched.h:16), NOT CLONE_NEWPID.
// All prior "kernel silently drops CLONE_NEWPID" observations were the inert
// CLONE_PTRACE flag. The real CLONE_NEWPID is 0x2000_0000 (sched.h:32). Kernels
// apply the flag or return -EPERM; they never silently drop it.
const CLONE_NEWPID: u64 = 0x2000_0000;
const CLONE_NEWUSER: u64 = 0x1000_0000;

const M_BASELINE: i32 = 0;
const M_NS_KILL: i32 = 1;
const M_PTY: i32 = 2;
const M_DRAIN: i32 = 3;
const M_SECCOMP: i32 = 4;
const M_REAP: i32 = 5;
const M_PG3A: i32 = 6;
const M_PG3B: i32 = 7;
const M_NSPROBE: i32 = 8;

#[repr(C)]
struct CloneArgs {
    flags: u64,
    pidfd: u64,
    child_tid: u64,
    parent_tid: u64,
    exit_signal: u64,
    stack: u64,
    stack_size: u64,
    tls: u64,
    set_tid: u64,
    set_tid_size: u64,
    cgroup: u64,
}

static mut CHILD_REPORT_FD: RawFd = -1;
static mut CHILD_PARENT_PID: i32 = 0;
static mut CHILD_ARG1: i32 = 0;
static mut CHILD_MODE: i32 = M_BASELINE;

fn say(s: impl AsRef<str>) {
    let s = s.as_ref();
    println!("{s}");
    if let Ok(mut f) = std::fs::OpenOptions::new()
        .create(true)
        .append(true)
        .open(LOG)
    {
        let _ = writeln!(f, "{s}");
    }
}

fn errno() -> i32 {
    std::io::Error::last_os_error().raw_os_error().unwrap_or(-1)
}

fn errstr() -> String {
    format!(" errno={}", errno())
}

fn clone3_newpid() -> Result<libc::pid_t, i32> {
    let args = CloneArgs {
        flags: CLONE_NEWPID,
        pidfd: 0,
        child_tid: 0,
        parent_tid: 0,
        exit_signal: libc::SIGCHLD as u64,
        stack: 0,
        stack_size: 0,
        tls: 0,
        set_tid: 0,
        set_tid_size: 0,
        cgroup: 0,
    };
    let pid = unsafe {
        libc::syscall(
            SYS_CLONE3,
            &args as *const CloneArgs as usize,
            std::mem::size_of::<CloneArgs>() as usize,
        )
    };
    if pid < 0 {
        Err(errno())
    } else {
        Ok(pid as libc::pid_t)
    }
}

fn clone_plain_newpid() -> Result<libc::pid_t, i32> {
    let flags = (CLONE_NEWPID | libc::SIGCHLD as u64) as usize;
    let pid = unsafe { libc::syscall(SYS_CLONE, flags, 0usize, 0usize, 0usize, 0usize) };
    if pid < 0 {
        Err(errno())
    } else {
        Ok(pid as libc::pid_t)
    }
}

fn clone_plain() -> Result<libc::pid_t, i32> {
    let pid = unsafe {
        libc::syscall(
            SYS_CLONE,
            libc::SIGCHLD as usize,
            0usize,
            0usize,
            0usize,
            0usize,
        )
    };
    if pid < 0 {
        Err(errno())
    } else {
        Ok(pid as libc::pid_t)
    }
}

fn spawn_child(
    mode: i32,
    parent_pid: i32,
    arg1: i32,
    newpid: bool,
) -> Result<(libc::pid_t, RawFd), String> {
    let mut fds = [0 as RawFd; 2];
    if unsafe { libc::pipe(fds.as_mut_ptr()) } != 0 {
        return Err(format!("report pipe: errno={}", errno()));
    }
    let (report_r, report_w) = (fds[0], fds[1]);
    unsafe {
        CHILD_MODE = mode;
        CHILD_PARENT_PID = parent_pid;
        CHILD_ARG1 = arg1;
        CHILD_REPORT_FD = report_w;
    }
    let pid = if newpid {
        match clone3_newpid() {
            Ok(p) => p,
            Err(e) if e == libc::ENOSYS => match clone_plain_newpid() {
                Ok(p) => p,
                Err(e2) => {
                    unsafe {
                        libc::close(report_r);
                        libc::close(report_w);
                    }
                    return Err(format!(
                        "clone3(CLONE_NEWPID) errno={e}, fallback clone errno={e2}"
                    ));
                }
            },
            Err(e) => {
                unsafe {
                    libc::close(report_r);
                    libc::close(report_w);
                }
                return Err(format!("clone3(CLONE_NEWPID) errno={e}"));
            }
        }
    } else {
        match clone_plain() {
            Ok(p) => p,
            Err(e) => {
                unsafe {
                    libc::close(report_r);
                    libc::close(report_w);
                }
                return Err(format!("clone errno={e}"));
            }
        }
    };
    if pid == 0 {
        unsafe { child_main() }
    }
    unsafe {
        libc::close(report_w);
    }
    Ok((pid, report_r))
}

unsafe fn cwl(fd: RawFd, s: &str) {
    // single write so concurrent writers (child+grandchild) cannot interleave mid-line
    let mut b = Vec::with_capacity(s.len() + 1);
    b.extend_from_slice(s.as_bytes());
    b.push(b'\n');
    let _ = libc::write(fd, b.as_ptr() as *const libc::c_void, b.len());
}
unsafe fn cwi(fd: RawFd, label: &str, v: i64, extra: &str) {
    let s = format!("{label}={v}{extra}");
    cwl(fd, &s);
}

unsafe fn child_main() -> ! {
    let fd = CHILD_REPORT_FD;
    let pp = CHILD_PARENT_PID;
    let a1 = CHILD_ARG1;
    match CHILD_MODE {
        M_BASELINE => child_baseline(fd, pp),
        M_NS_KILL => child_ns_kill(fd, pp),
        M_PTY => child_pty(fd, a1),
        M_DRAIN => child_drain(fd, a1),
        M_SECCOMP => child_seccomp(fd),
        M_REAP => child_reap(fd),
        M_PG3A => child_pg3(fd, "pg3a"),
        M_PG3B => child_pg3(fd, "pg3b"),
        M_NSPROBE => child_nsprobe(fd),
        _ => libc::_exit(2),
    }
}

unsafe fn child_baseline(fd: RawFd, pp: i32) -> ! {
    cwl(fd, "baseline-child-entered");
    let gp = libc::getppid();
    cwi(fd, "getppid", gp as i64, "");
    let r = libc::kill(pp, libc::SIGSTOP);
    cwi(fd, "kill_stop_ret", r as i64, &errstr());
    libc::usleep(800_000);
    let r2 = libc::kill(pp, libc::SIGCONT);
    cwi(fd, "kill_cont_ret", r2 as i64, &errstr());
    cwl(fd, "baseline-child-done");
    libc::_exit(0);
}

unsafe fn child_ns_kill(fd: RawFd, pp: i32) -> ! {
    cwl(fd, "nschild-entered");
    let me = libc::syscall(libc::SYS_getpid);
    cwi(fd, "getpid", me as i64, "");
    let gp = libc::syscall(libc::SYS_getppid);
    cwi(fd, "getppid", gp as i64, "");
    let parent_visible = proc_has_pid(pp);
    cwi(fd, "parent_pid_visible_in_proc", parent_visible as i64, "");
    let st = std::fs::read_to_string("/proc/self/status").unwrap_or_default();
    let nspid = st
        .lines()
        .find_map(|l| l.strip_prefix("NSpid:").map(|v| v.trim().to_string()))
        .unwrap_or_default();
    cwl(fd, &format!("nschild_NSpid={nspid}"));
    let pid_inode = std::fs::read_link("/proc/self/ns/pid")
        .map(|p| p.to_string_lossy().to_string())
        .unwrap_or_default();
    cwl(fd, &format!("nschild_pid_ns_inode={pid_inode}"));
    // Real new pid ns iff we have 2+ NSpid levels. The parent-visible-in-/proc
    // check is INVALID here: the child inherits the parent's /proc mount, so
    // the parent is always visible in /proc regardless of pidns membership.
    // (Fixed on-device: this was P1b's false "NOT HONORED" verdict bug.)
    let ns_is_real = nspid.split_whitespace().count() >= 2;
    cwi(fd, "nschild_ns_is_real", ns_is_real as i64, "");
    cwl(fd, "nschild-before-kill-attempt");
    libc::usleep(2_000_000);
    if ns_is_real {
        let r = libc::kill(pp, libc::SIGKILL);
        cwi(fd, "kill_parent_ret", r as i64, &errstr());
    } else {
        // CLONE_NEWPID was not honored: we share the parent's ns; actually killing
        // the parent here would destroy the harness, so skip and report the fact
        cwi(fd, "kill_parent_ret", -999, " KILL_SKIPPED_NS_NOT_REAL");
    }
    cwl(fd, "nschild-alive-after-kill-attempt");
    libc::usleep(200_000);
    cwl(fd, "nschild-exiting");
    libc::_exit(0);
}

fn proc_has_pid(pid: i32) -> bool {
    std::path::Path::new(&format!("/proc/{pid}")).exists()
}

unsafe fn child_pty(fd: RawFd, slave: i32) -> ! {
    cwl(fd, "pty-child-entered");
    let r0 = libc::dup2(slave, 0);
    cwi(fd, "dup2_0", r0 as i64, &errstr());
    let r1 = libc::dup2(slave, 1);
    cwi(fd, "dup2_1", r1 as i64, &errstr());
    let r2 = libc::dup2(slave, 2);
    cwi(fd, "dup2_2", r2 as i64, &errstr());
    let r3 = libc::setsid();
    cwi(fd, "setsid", r3 as i64, &errstr());
    let r4 = libc::ioctl(slave, libc::TIOCSCTTY as libc::Ioctl, 0);
    cwi(fd, "tiocsctty", r4 as i64, &errstr());
    let isa = libc::isatty(0);
    cwi(fd, "isatty0", isa as i64, "");
    let mut ws: libc::winsize = std::mem::zeroed();
    let r5 = libc::ioctl(0, libc::TIOCGWINSZ as libc::Ioctl, &mut ws);
    cwi(
        fd,
        "tiocgwinsz",
        r5 as i64,
        &format!(" rows={} cols={}", ws.ws_row, ws.ws_col),
    );
    let mut sid: libc::c_int = 0;
    let r6 = libc::ioctl(0, 0x5429 as libc::Ioctl, &mut sid); // TIOCGSID
    cwi(fd, "tiocgsid", r6 as i64, &format!(" sid={sid}"));
    let mut pgrp: libc::c_int = 0;
    let r7 = libc::ioctl(0, libc::TIOCGPGRP as libc::Ioctl, &mut pgrp);
    cwi(fd, "tiocgpgrp", r7 as i64, &format!(" pgrp={pgrp}"));
    let msg = b"PTY-ECHO:hello-from-namespaced-child\n";
    let w = libc::write(1, msg.as_ptr() as *const libc::c_void, msg.len());
    cwi(fd, "pty_stdout_write", w as i64, &errstr());
    cwl(fd, "pty-child-done");
    libc::_exit(0);
}

unsafe fn child_drain(fd: RawFd, sock: i32) -> ! {
    cwl(fd, "drain-child-entered");
    let mut buf = [0u8; 4096];
    let mut got = 0usize;
    while got < buf.len() {
        let n = libc::read(
            sock,
            buf[got..].as_mut_ptr() as *mut libc::c_void,
            buf.len() - got,
        );
        if n <= 0 {
            break;
        }
        got += n as usize;
    }
    cwi(fd, "child_read_bytes", got as i64, "");
    let mut off = 0usize;
    while off < got {
        let n = libc::write(sock, buf[off..].as_ptr() as *const libc::c_void, got - off);
        if n <= 0 {
            break;
        }
        off += n as usize;
    }
    cwi(fd, "child_echo_bytes", off as i64, "");
    cwl(fd, "drain-child-done");
    libc::_exit(0);
}

const BPF_LD: u16 = 0x00;
const BPF_W: u16 = 0x00;
const BPF_ABS: u16 = 0x20;
const BPF_JMP: u16 = 0x05;
const BPF_JEQ: u16 = 0x10;
const BPF_K: u16 = 0x00;
const BPF_RET: u16 = 0x06;
const SECCOMP_RET_KILL_PROCESS: u32 = 0x8000_0000;
const SECCOMP_RET_ERRNO: u32 = 0x0005_0000;
const SECCOMP_RET_ALLOW: u32 = 0x7fff_0000;
const EPERM: u32 = 1;
const AUDIT_ARCH_AARCH64: u32 = 0xC000_00B7;

const fn bpf_stmt(code: u16, k: u32) -> libc::sock_filter {
    libc::sock_filter {
        code,
        jt: 0,
        jf: 0,
        k,
    }
}
const fn bpf_jump(code: u16, k: u32, jt: u8, jf: u8) -> libc::sock_filter {
    libc::sock_filter { code, jt, jf, k }
}

static SESSION_CONTAINMENT_FILTER: [libc::sock_filter; 13] = [
    bpf_stmt(BPF_LD | BPF_W | BPF_ABS, 4),
    bpf_jump(BPF_JMP | BPF_JEQ | BPF_K, AUDIT_ARCH_AARCH64, 1, 0),
    bpf_stmt(BPF_RET | BPF_K, SECCOMP_RET_KILL_PROCESS),
    bpf_stmt(BPF_LD | BPF_W | BPF_ABS, 0),
    bpf_jump(BPF_JMP | BPF_JEQ | BPF_K, libc::SYS_setsid as u32, 0, 1),
    bpf_stmt(BPF_RET | BPF_K, SECCOMP_RET_ERRNO | EPERM),
    bpf_jump(BPF_JMP | BPF_JEQ | BPF_K, libc::SYS_setpgid as u32, 0, 1),
    bpf_stmt(BPF_RET | BPF_K, SECCOMP_RET_ERRNO | EPERM),
    bpf_jump(BPF_JMP | BPF_JEQ | BPF_K, libc::SYS_unshare as u32, 0, 1),
    bpf_stmt(BPF_RET | BPF_K, SECCOMP_RET_ERRNO | EPERM),
    bpf_jump(BPF_JMP | BPF_JEQ | BPF_K, libc::SYS_setns as u32, 0, 1),
    bpf_stmt(BPF_RET | BPF_K, SECCOMP_RET_ERRNO | EPERM),
    bpf_stmt(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
];

unsafe fn child_seccomp(fd: RawFd) -> ! {
    cwl(fd, "seccomp-child-entered");
    let r = libc::setsid();
    cwi(fd, "setsid_before_filter", r as i64, &errstr());
    let prog = libc::sock_fprog {
        len: SESSION_CONTAINMENT_FILTER.len() as u16,
        filter: SESSION_CONTAINMENT_FILTER.as_ptr().cast_mut(),
    };
    let p1 = libc::prctl(libc::PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
    cwi(fd, "no_new_privs", p1 as i64, &errstr());
    let p2 = libc::prctl(
        libc::PR_SET_SECCOMP,
        libc::SECCOMP_MODE_FILTER,
        &prog as *const libc::sock_fprog as libc::c_ulong,
        0,
        0,
    );
    cwi(fd, "seccomp_filter", p2 as i64, &errstr());
    cwl(fd, "filter-installed");
    let a = libc::setpgid(0, 0);
    cwi(fd, "setpgid", a as i64, &errstr());
    let b = libc::setsid();
    cwi(fd, "setsid_after_filter", b as i64, &errstr());
    let c = libc::syscall(libc::SYS_unshare, CLONE_NEWUSER);
    cwi(fd, "unshare", c as i64, &errstr());
    let d = libc::write(1, b"allowed-bytes\n".as_ptr() as *const libc::c_void, 14);
    cwi(fd, "write_allowed", d as i64, &errstr());
    cwl(fd, "seccomp-child-alive-after-denials");
    libc::_exit(0);
}

unsafe fn child_nsprobe(fd: RawFd) -> ! {
    // CHILD_ARG1: 0 = self in new ns (clone3/clone), 2 = unshare-then-fork
    if CHILD_ARG1 == 2 {
        let ur = libc::syscall(libc::SYS_unshare, CLONE_NEWPID);
        cwi(fd, "unshare_ret", ur as i64, &errstr());
        let g = libc::fork();
        cwi(fd, "fork_ret", g as i64, &errstr());
        if g != 0 {
            // parent side: wait for the grandchild, then hold
            cwl(fd, "nsprobe-unshare-parent-holding");
            loop {
                libc::pause();
            }
        }
        // grandchild: now in the new pid ns
        cwl(fd, "nsprobe-grandchild-entered");
    } else {
        cwl(fd, "nsprobe-entered");
    }
    let me = libc::syscall(libc::SYS_getpid);
    cwi(fd, "getpid_syscall", me as i64, "");
    let gp = libc::syscall(libc::SYS_getppid);
    cwi(fd, "getppid_syscall", gp as i64, "");
    let st = std::fs::read_to_string("/proc/self/status").unwrap_or_default();
    let nspid = st
        .lines()
        .find_map(|l| l.strip_prefix("NSpid:").map(|v| v.trim().to_string()))
        .unwrap_or_default();
    cwl(fd, &format!("NSpid={nspid}"));
    let inode = std::fs::read_link("/proc/self/ns/pid")
        .map(|p| p.to_string_lossy().to_string())
        .unwrap_or_default();
    cwl(fd, &format!("pid_ns_inode={inode}"));
    cwl(fd, "nsprobe-pausing");
    loop {
        libc::pause();
    }
}

unsafe fn child_reap(fd: RawFd) -> ! {
    cwl(fd, "reap-child-entered");
    libc::usleep(500_000);
    cwl(fd, "reap-child-exiting");
    libc::_exit(0);
}

unsafe fn child_pg3(fd: RawFd, tag: &str) -> ! {
    cwl(fd, &format!("{tag}-child-entered"));
    let r = libc::setsid();
    cwi(fd, "setsid", r as i64, &errstr());
    let g = libc::fork();
    cwi(fd, "fork_grandchild", g as i64, &errstr());
    if g == 0 {
        cwi(fd, "grandchild_getpid", libc::getpid() as i64, "");
        cwi(fd, "grandchild_getppid", libc::getppid() as i64, "");
        cwl(fd, &format!("{tag}-grandchild-pausing"));
        loop {
            libc::pause();
        }
    }
    cwl(fd, &format!("{tag}-child-waiting"));
    loop {
        libc::pause();
    }
}

struct Rdr {
    fd: RawFd,
    buf: Vec<u8>,
    seen: Vec<String>,
}

impl Rdr {
    fn new(fd: RawFd) -> Self {
        unsafe {
            let fl = libc::fcntl(fd, libc::F_GETFL);
            libc::fcntl(fd, libc::F_SETFL, fl | libc::O_NONBLOCK);
        }
        Rdr {
            fd,
            buf: Vec::new(),
            seen: Vec::new(),
        }
    }
    fn all_seen(&self) -> Vec<String> {
        self.seen.clone()
    }
    fn next_line(&mut self, timeout: Duration) -> Option<String> {
        let deadline = Instant::now() + timeout;
        loop {
            if let Some(pos) = self.buf.iter().position(|&b| b == b'\n') {
                let line: Vec<u8> = self.buf.drain(..=pos).collect();
                let s = String::from_utf8_lossy(&line[..line.len() - 1]).to_string();
                if !s.is_empty() {
                    self.seen.push(s.clone());
                    return Some(s);
                }
                continue;
            }
            let now = Instant::now();
            if now >= deadline {
                return None;
            }
            let rem = deadline.saturating_duration_since(now);
            let mut pfd = libc::pollfd {
                fd: self.fd,
                events: libc::POLLIN,
                revents: 0,
            };
            let pr =
                unsafe { libc::poll(&mut pfd, 1, rem.as_millis().min(i32::MAX as u128) as i32) };
            if pr <= 0 {
                continue;
            }
            let mut tmp = [0u8; 4096];
            let n =
                unsafe { libc::read(self.fd, tmp.as_mut_ptr() as *mut libc::c_void, tmp.len()) };
            if n <= 0 {
                continue;
            }
            self.buf.extend_from_slice(&tmp[..n as usize]);
        }
    }
    fn wait_for(&mut self, marker: &str, timeout: Duration) -> bool {
        let deadline = Instant::now() + timeout;
        while Instant::now() < deadline {
            let rem = deadline.saturating_duration_since(Instant::now());
            if let Some(l) = self.next_line(rem) {
                if l.contains(marker) {
                    return true;
                }
            }
        }
        false
    }
    fn drain_all(&mut self, timeout: Duration) -> Vec<String> {
        let mut v = Vec::new();
        let deadline = Instant::now() + timeout;
        while Instant::now() < deadline {
            let rem = deadline.saturating_duration_since(Instant::now());
            match self.next_line(rem) {
                Some(l) => v.push(l),
                None => break,
            }
        }
        v
    }
}

fn waitpid_poll(pid: libc::pid_t, timeout: Duration) -> Result<Option<libc::c_int>, i32> {
    let deadline = Instant::now() + timeout;
    loop {
        let mut st: libc::c_int = 0;
        let r = unsafe { libc::waitpid(pid, &mut st, libc::WNOHANG) };
        if r == pid {
            return Ok(Some(st));
        }
        if r < 0 {
            return Err(errno());
        }
        if Instant::now() >= deadline {
            return Ok(None);
        }
        std::thread::sleep(Duration::from_millis(20));
    }
}

fn status_desc(st: libc::c_int) -> String {
    if libc::WIFEXITED(st) {
        format!("exited({})", libc::WEXITSTATUS(st))
    } else if libc::WIFSIGNALED(st) {
        format!("signaled({})", libc::WTERMSIG(st))
    } else {
        format!("status=0x{st:x}")
    }
}

fn stat_fields(pid: i32) -> Option<Vec<String>> {
    let s = std::fs::read_to_string(format!("/proc/{pid}/stat")).ok()?;
    let rest = s.split_once(')').map(|(_, r)| r.to_string())?;
    Some(rest.split_whitespace().map(|s| s.to_string()).collect())
}

fn find_grandchild(ppid: i32) -> Option<i32> {
    let dir = std::fs::read_dir("/proc").ok()?;
    for e in dir.flatten() {
        let name = e.file_name().to_string_lossy().to_string();
        if let Ok(p) = name.parse::<i32>() {
            if let Some(f) = stat_fields(p) {
                if f.get(1).and_then(|s| s.parse::<i32>().ok()) == Some(ppid) {
                    return Some(p);
                }
            }
        }
    }
    None
}

fn make_pty() -> Result<(RawFd, RawFd), String> {
    let master = unsafe {
        libc::open(
            b"/dev/ptmx\0".as_ptr() as *const libc::c_char,
            libc::O_RDWR | libc::O_NOCTTY,
        )
    };
    if master < 0 {
        return Err(format!("open ptmx errno={}", errno()));
    }
    if unsafe { libc::grantpt(master) } != 0 {
        return Err(format!("grantpt errno={}", errno()));
    }
    if unsafe { libc::unlockpt(master) } != 0 {
        return Err(format!("unlockpt errno={}", errno()));
    }
    let mut name = [0u8; 64];
    let r = unsafe { libc::ptsname_r(master, name.as_mut_ptr() as *mut libc::c_char, name.len()) };
    if r != 0 {
        return Err(format!("ptsname_r errno={r}"));
    }
    let n = name.iter().position(|&b| b == 0).unwrap_or(name.len());
    let slave = unsafe {
        libc::open(
            name[..n].as_ptr() as *const libc::c_char,
            libc::O_RDWR | libc::O_NOCTTY,
        )
    };
    if slave < 0 {
        return Err(format!("open slave errno={}", errno()));
    }
    Ok((master, slave))
}

fn caps_from_status() -> (String, String, String) {
    let st = std::fs::read_to_string("/proc/self/status").unwrap_or_default();
    let mut cap = String::new();
    let mut nnp = String::new();
    let mut sec = String::new();
    for l in st.lines() {
        if let Some(v) = l.strip_prefix("CapEff:") {
            cap = v.trim().to_string();
        } else if let Some(v) = l.strip_prefix("NoNewPrivs:") {
            nnp = v.trim().to_string();
        } else if let Some(v) = l.strip_prefix("Seccomp:") {
            sec = v.trim().to_string();
        }
    }
    (cap, nnp, sec)
}

fn prctl_subreaper() -> i32 {
    unsafe { libc::prctl(36, 1, 0, 0, 0) }
}

fn t0() -> bool {
    say("=== T0: privilege precondition + clone3(CLONE_NEWPID) feasibility ===");
    let (cap, nnp, sec) = caps_from_status();
    say(format!(
        "T0 uid={} gid={} CapEff={cap} NoNewPrivs={nnp} Seccomp={sec}",
        unsafe { libc::geteuid() },
        unsafe { libc::getegid() }
    ));
    let sr = prctl_subreaper();
    say(format!(
        "T0 prctl(PR_SET_CHILD_SUBREAPER)= {sr} errno={}",
        errno()
    ));

    let args = CloneArgs {
        flags: CLONE_NEWPID,
        pidfd: 0,
        child_tid: 0,
        parent_tid: 0,
        exit_signal: libc::SIGCHLD as u64,
        stack: 0,
        stack_size: 0,
        tls: 0,
        set_tid: 0,
        set_tid_size: 0,
        cgroup: 0,
    };
    let pid = unsafe {
        libc::syscall(
            SYS_CLONE3,
            &args as *const CloneArgs as usize,
            std::mem::size_of::<CloneArgs>() as usize,
        )
    };
    if pid < 0 {
        say(format!(
            "T0 clone3(flags=CLONE_NEWPID(0x{:x}), exit_signal=SIGCHLD) = -1 errno={}",
            CLONE_NEWPID,
            errno()
        ));
        return false;
    }
    if pid == 0 {
        unsafe { libc::_exit(0) }
    }
    say(format!(
        "T0 clone3(CLONE_NEWPID) = pid {pid} (syscall accepted; ns-creation checked next in T0b)"
    ));
    let r = waitpid_poll(pid as libc::pid_t, Duration::from_secs(3));
    say(format!(
        "T0 waitpid probe child: {:?}",
        r.map(|st| st.map(status_desc))
    ));
    true
}

// spawn a probe child by method, collect its ns-identity report, kill it, reap.
// method: "clone3" | "clone" | "unshare+fork". Returns (reported_getpid_syscall, nspid_str, inode).
fn nsprobe_run(method: &str) -> (i64, String, String) {
    let mut child_fn: Option<Box<dyn Fn() -> Result<(libc::pid_t, RawFd), String>>> = None;
    let arg1 = if method == "unshare+fork" { 2 } else { 0 };
    let newpid = method != "unshare+fork"; // clone3/clone spawn with CLONE_NEWPID

    // we need a spawn that uses the specific low-level method, so re-implement here
    let mut fds = [0 as RawFd; 2];
    let _ = unsafe { libc::pipe(fds.as_mut_ptr()) };
    let (report_r, report_w) = (fds[0], fds[1]);
    unsafe {
        CHILD_MODE = M_NSPROBE;
        CHILD_PARENT_PID = 0;
        CHILD_ARG1 = arg1;
        CHILD_REPORT_FD = report_w;
    }
    let spawn_res = if newpid {
        if method == "clone3" {
            clone3_newpid()
        } else {
            clone_plain_newpid()
        }
    } else {
        // unshare+fork: plain clone, child does the unshare itself
        clone_plain()
    };
    let pid = match spawn_res {
        Ok(p) if p > 0 => p,
        Ok(_) => unsafe { child_main() },
        Err(e) => {
            unsafe {
                libc::close(report_r);
                libc::close(report_w);
            }
            say(format!("nsprobe[{method}] spawn errno={e}"));
            return (0, String::new(), String::new());
        }
    };
    unsafe {
        libc::close(report_w);
    }
    let _ = child_fn.take();

    let mut r = Rdr::new(report_r);
    let _ = r.wait_for("nsprobe-pausing", Duration::from_secs(3));
    let lines = r.all_seen();
    let mut gpid = 0i64;
    let mut nspid = String::new();
    let mut inode = String::new();
    for l in &lines {
        say(format!("nsprobe[{method}] child> {l}"));
        if let Some(v) = l.strip_prefix("getpid_syscall=") {
            gpid = v.parse().unwrap_or(0);
        } else if let Some(v) = l.strip_prefix("NSpid=") {
            nspid = v.to_string();
        } else if let Some(v) = l.strip_prefix("pid_ns_inode=") {
            inode = v.to_string();
        }
    }
    // kill the grandchild FIRST (while the child is still its parent, so it can be
    // located via ppid), then the holding child; otherwise the orphaned grandchild
    // keeps report_w open and the caller's shell hangs waiting for EOF
    let sib = if method == "unshare+fork" {
        std::thread::sleep(Duration::from_millis(30));
        find_grandchild(pid)
    } else {
        None
    };
    if let Some(sib) = sib {
        unsafe { libc::kill(sib, libc::SIGKILL) };
        let _ = waitpid_poll(sib, Duration::from_secs(2));
    }
    unsafe { libc::kill(pid, libc::SIGKILL) };
    let _ = waitpid_poll(pid, Duration::from_secs(2));
    unsafe { libc::close(report_r) };
    (gpid, nspid, inode)
}

fn t0b() {
    say("");
    say("=== T0b: which clone path actually creates a new PID namespace? ===");
    let parent_inode = std::fs::read_link("/proc/self/ns/pid")
        .map(|p| p.to_string_lossy().to_string())
        .unwrap_or_default();
    say(format!("T0b parent pid-ns inode: {parent_inode}"));

    for method in ["clone3", "clone", "unshare+fork"] {
        let (gpid, nspid, inode) = nsprobe_run(method);
        let two_levels = nspid.split_whitespace().count() >= 2;
        let is_new_ns = gpid == 1 && two_levels && inode != parent_inode;
        say(format!(
            "T0b {method}: getpid_syscall={gpid} NSpid=[{nspid}] pid-ns inode={inode} -> {}",
            if is_new_ns {
                "NEW PID NAMESPACE CREATED"
            } else {
                "SAME NAMESPACE (FAILED)"
            }
        ));
    }
}

fn p1a() -> bool {
    say("");
    say("=== P1a: baseline - child WITHOUT CLONE_NEWPID can resolve+signal parent ===");
    let pp = unsafe { libc::getpid() };
    let t0 = Instant::now();
    let (pid, rfd) = match spawn_child(M_BASELINE, pp, 0, false) {
        Ok(v) => v,
        Err(e) => {
            say(format!("P1a FAIL spawn: {e}"));
            return false;
        }
    };
    say(format!("P1a spawned child pid={pid} (no new pid ns)"));
    let mut r = Rdr::new(rfd);
    let lines = r.drain_all(Duration::from_secs(4));
    let elapsed = t0.elapsed();
    say(format!(
        "P1a parent elapsed since spawn = {elapsed:?} (>= ~700ms implies frozen by SIGSTOP)"
    ));
    for l in &lines {
        say(format!("P1a child> {l}"));
    }
    let r = waitpid_poll(pid, Duration::from_secs(3));
    say(format!(
        "P1a waitpid: {:?}",
        r.map(|st| st.map(status_desc))
    ));
    unsafe { libc::close(rfd) };

    let gp_ok = lines.iter().any(|l| l == &format!("getppid={pp}"));
    let stop_ok = lines.iter().any(|l| l.starts_with("kill_stop_ret=0 "));
    let frozen_ok = elapsed >= Duration::from_millis(700);
    let cont_ok = lines.iter().any(|l| l.starts_with("kill_cont_ret=0 "));
    let done_ok = lines.iter().any(|l| l == "baseline-child-done");
    let pass = gp_ok && stop_ok && frozen_ok && cont_ok && done_ok;
    say(format!(
        "P1a VERDICT: {} (getppid==parent:{gp_ok} child_sigstop_delivered:{stop_ok} parent_frozen:{frozen_ok} sigcont_delivered:{cont_ok} child_finished:{done_ok})",
        if pass { "PASS" } else { "FAIL" }
    ));
    pass
}

fn p1b() -> bool {
    say("");
    say("=== P1b: namespaced - child in CLONE_NEWPID cannot resolve/signal parent ===");
    let pp = unsafe { libc::getpid() };
    let (pid, rfd) = match spawn_child(M_NS_KILL, pp, 0, true) {
        Ok(v) => v,
        Err(e) => {
            say(format!("P1b FAIL spawn: {e}"));
            return false;
        }
    };
    say(format!("P1b spawned child pid={pid} (parent-ns pid)"));
    let mut r = Rdr::new(rfd);
    say("P1b parent-alive-after-spawn");
    let ns_confirmed = r.wait_for("nschild-before-kill-attempt", Duration::from_secs(4));
    say(format!("P1b child-reached-kill-gate={ns_confirmed}"));
    let pre: Vec<String> = r.all_seen();
    for l in &pre {
        say(format!("P1b child> {l}"));
    }
    // parent-side definitive check: NSpid shows "<parent-ns-pid> <ns-pid>" for a
    // child inside a nested pid namespace
    let pstat = std::fs::read_to_string(format!("/proc/{pid}/status")).unwrap_or_default();
    let p_nspid = pstat
        .lines()
        .find_map(|l| l.strip_prefix("NSpid:").map(|v| v.trim().to_string()))
        .unwrap_or_default();
    say(format!(
        "P1b parent-side /proc/{pid}/status NSpid={p_nspid} (two numbers => nested pid ns)"
    ));
    let getpid = pre
        .iter()
        .find_map(|l| l.strip_prefix("getpid="))
        .map(|v| v.to_string())
        .unwrap_or_default();
    let getppid = pre
        .iter()
        .find_map(|l| l.strip_prefix("getppid="))
        .map(|v| v.to_string())
        .unwrap_or_default();
    let not_visible = pre.iter().any(|l| l == "parent_pid_visible_in_proc=0");
    let ns_real_parent = p_nspid.split_whitespace().count() >= 2;
    let child_ns_is_real = pre.iter().any(|l| l == "nschild_ns_is_real=1");
    let ns_is_real = ns_real_parent && child_ns_is_real;
    say(format!(
        "P1b namespace-check: child getpid={getpid} getppid={getppid} parent_hidden_in_proc={not_visible} parent-side-NSpid-2level={ns_real_parent} child_ns_is_real={child_ns_is_real} -> namespace REAL={ns_is_real}"
    ));
    let w = waitpid_poll(pid, Duration::from_millis(100));
    say(format!(
        "P1b waitpid(WNOHANG) before kill gate: {w:?} (Ok(None)=still running)"
    ));
    say("P1b parent-alive-before-child-kill-attempt");
    let post: Vec<String> = r.drain_all(Duration::from_secs(5));
    for l in &post {
        say(format!("P1b child> {l}"));
    }
    let parent_survived = post.iter().any(|l| l == "nschild-alive-after-kill-attempt");
    say(format!(
        "P1b parent-alive-after-child-kill-attempt={parent_survived}"
    ));
    let rr = waitpid_poll(pid, Duration::from_secs(3));
    say(format!(
        "P1b waitpid reap: {:?}",
        rr.map(|st| st.map(status_desc))
    ));
    unsafe { libc::close(rfd) };

    let esrch = post
        .iter()
        .any(|l| l.starts_with(&format!("kill_parent_ret=-1 errno={}", libc::ESRCH)));
    let alive = post.iter().any(|l| l == "nschild-alive-after-kill-attempt");
    let exiting = post.iter().any(|l| l == "nschild-exiting");
    let skipped = post.iter().any(|l| l.contains("KILL_SKIPPED_NS_NOT_REAL"));
    let pass = ns_is_real && esrch && alive && exiting && ns_confirmed;
    say(format!(
        "P1b VERDICT: {} (namespace_REAL:{ns_is_real} parent_hidden_in_proc:{not_visible} kill(parent)->ESRCH:{esrch} child_survived_kill_attempt:{alive} child_exited_normally:{exiting} kill_skipped_same_ns:{skipped})",
        if pass { "PASS" } else { "FAIL" }
    ));
    if !ns_is_real {
        say(format!(
            "P1b note: CLONE_NEWPID NOT HONORED on this target -> child lives in parent's pid ns -> getppid()/kill(parent) signal-back vector stays OPEN (baseline P1a proves the same-ns kill lands)"
        ));
    }
    pass
}

fn p2a() -> bool {
    say("");
    say("=== P2a: pty + setsid + TIOCSCTTY inside the new pid namespace ===");
    let (master, slave) = match make_pty() {
        Ok(v) => v,
        Err(e) => {
            say(format!("P2a FAIL make_pty: {e}"));
            return false;
        }
    };
    let mut ws: libc::winsize = unsafe { std::mem::zeroed() };
    ws.ws_row = 24;
    ws.ws_col = 80;
    unsafe { libc::ioctl(master, libc::TIOCSWINSZ as libc::Ioctl, &ws) };
    let (pid, rfd) = match spawn_child(M_PTY, 0, slave, true) {
        Ok(v) => v,
        Err(e) => {
            say(format!("P2a FAIL spawn: {e}"));
            return false;
        }
    };
    say(format!("P2a spawned pty child pid={pid} (namespaced)"));
    let mut r = Rdr::new(rfd);
    let lines = r.drain_all(Duration::from_secs(3));
    for l in &lines {
        say(format!("P2a child> {l}"));
    }
    let mut pty_out = Vec::new();
    let mut pfd = libc::pollfd {
        fd: master,
        events: libc::POLLIN,
        revents: 0,
    };
    let pr = unsafe { libc::poll(&mut pfd, 1, 1000) };
    if pr > 0 {
        let mut tmp = [0u8; 256];
        let n = unsafe { libc::read(master, tmp.as_mut_ptr() as *mut libc::c_void, tmp.len()) };
        if n > 0 {
            pty_out.extend_from_slice(&tmp[..n as usize]);
        }
    }
    say(format!(
        "P2a pty master read: {:?}",
        String::from_utf8_lossy(&pty_out)
    ));
    let rr = waitpid_poll(pid, Duration::from_secs(3));
    say(format!(
        "P2a waitpid: {:?}",
        rr.map(|st| st.map(status_desc))
    ));
    unsafe {
        libc::close(master);
        libc::close(slave);
        libc::close(rfd);
    }

    let dup_ok = ["dup2_0=0 ", "dup2_1=1 ", "dup2_2=2 "]
        .iter()
        .all(|m| lines.iter().any(|l| l.starts_with(m)));
    let setsid_ok = lines
        .iter()
        .any(|l| l.starts_with(&format!("setsid={pid} ")));
    let ctty_ok = lines.iter().any(|l| l.starts_with("tiocsctty=0 "));
    let isatty_ok = lines.iter().any(|l| l == "isatty0=1");
    let winsz_ok = lines
        .iter()
        .any(|l| l.starts_with("tiocgwinsz=0") && l.contains("rows=24") && l.contains("cols=80"));
    let echo_ok =
        String::from_utf8_lossy(&pty_out).contains("PTY-ECHO:hello-from-namespaced-child");
    let pass = dup_ok && setsid_ok && ctty_ok && isatty_ok && winsz_ok && echo_ok;
    say(format!(
        "P2a VERDICT: {} (dup2_012:{dup_ok} setsid:{setsid_ok} TIOCSCTTY:{ctty_ok} isatty(0):{isatty_ok} winsize_24x80:{winsz_ok} pty_echo_crossed_ns:{echo_ok})",
        if pass { "PASS" } else { "FAIL" }
    ));
    pass
}

fn p2b() -> bool {
    say("");
    say("=== P2b: stdio drain byte-for-byte across the namespace boundary ===");
    let mut sv = [0 as RawFd; 2];
    if unsafe { libc::socketpair(libc::AF_UNIX, libc::SOCK_STREAM, 0, sv.as_mut_ptr()) } != 0 {
        say(format!("P2b FAIL socketpair errno={}", errno()));
        return false;
    }
    let (a, b) = (sv[0], sv[1]);
    let (pid, rfd) = match spawn_child(M_DRAIN, 0, a, true) {
        Ok(v) => v,
        Err(e) => {
            say(format!("P2b FAIL spawn: {e}"));
            return false;
        }
    };
    unsafe { libc::close(a) };
    say(format!("P2b spawned drain child pid={pid} (namespaced)"));

    let mut payload = [0u8; 4096];
    for i in 0..payload.len() {
        payload[i] = ((i.wrapping_mul(7) + (i >> 8)) & 0xff) as u8;
    }
    let mut off = 0usize;
    while off < payload.len() {
        let n = unsafe {
            libc::write(
                b,
                payload[off..].as_ptr() as *const libc::c_void,
                payload.len() - off,
            )
        };
        if n <= 0 {
            break;
        }
        off += n as usize;
    }
    let mut back = vec![0u8; payload.len()];
    let mut got = 0usize;
    let deadline = Instant::now() + Duration::from_secs(3);
    while got < back.len() && Instant::now() < deadline {
        let n = unsafe {
            libc::read(
                b,
                back[got..].as_mut_ptr() as *mut libc::c_void,
                back.len() - got,
            )
        };
        if n <= 0 {
            break;
        }
        got += n as usize;
    }
    unsafe { libc::close(b) };

    let mut r = Rdr::new(rfd);
    let lines = r.drain_all(Duration::from_secs(2));
    for l in &lines {
        say(format!("P2b child> {l}"));
    }
    let rr = waitpid_poll(pid, Duration::from_secs(3));
    say(format!(
        "P2b waitpid: {:?}",
        rr.map(|st| st.map(status_desc))
    ));
    unsafe { libc::close(rfd) };

    let equal = got == payload.len() && back == payload;
    say(format!(
        "P2b sent={off} received_back={got} byte_equal={equal}"
    ));
    let read_ok = lines.iter().any(|l| l == "child_read_bytes=4096");
    let echo_ok = lines.iter().any(|l| l == "child_echo_bytes=4096");
    let pass = equal && read_ok && echo_ok;
    say(format!(
        "P2b VERDICT: {} (child_read_4096:{read_ok} child_echo_4096:{echo_ok} parent_roundtrip_byte_equal:{equal})",
        if pass { "PASS" } else { "FAIL" }
    ));
    pass
}

fn p2c() -> bool {
    say("");
    say("=== P2c: seccomp chaining inside the new pid namespace ===");
    let (pid, rfd) = match spawn_child(M_SECCOMP, 0, 0, true) {
        Ok(v) => v,
        Err(e) => {
            say(format!("P2c FAIL spawn: {e}"));
            return false;
        }
    };
    say(format!("P2c spawned seccomp child pid={pid} (namespaced)"));
    let mut r = Rdr::new(rfd);
    let lines = r.drain_all(Duration::from_secs(3));
    for l in &lines {
        say(format!("P2c child> {l}"));
    }
    let rr = waitpid_poll(pid, Duration::from_secs(3));
    say(format!(
        "P2c waitpid: {:?}",
        rr.map(|st| st.map(status_desc))
    ));
    unsafe { libc::close(rfd) };

    let nnps_ok = lines.iter().any(|l| l.starts_with("no_new_privs=0 "));
    let filt_ok = lines.iter().any(|l| l.starts_with("seccomp_filter=0 "));
    let pre_ok = lines
        .iter()
        .any(|l| l.starts_with(&format!("setsid_before_filter={pid} ")));
    let setpgid_den = lines
        .iter()
        .any(|l| l == &format!("setpgid=-1 errno={}", libc::EPERM));
    let setsid_den = lines
        .iter()
        .any(|l| l == &format!("setsid_after_filter=-1 errno={}", libc::EPERM));
    let unshare_den = lines
        .iter()
        .any(|l| l == &format!("unshare=-1 errno={}", libc::EPERM));
    let write_ok = lines.iter().any(|l| l.starts_with("write_allowed=14"));
    let alive = lines
        .iter()
        .any(|l| l == "seccomp-child-alive-after-denials");
    let pass = nnps_ok
        && filt_ok
        && pre_ok
        && setpgid_den
        && setsid_den
        && unshare_den
        && write_ok
        && alive;
    say(format!(
        "P2c VERDICT: {} (no_new_privs:{nnps_ok} filter:{filt_ok} pre_filter_setsid:{pre_ok} setpgid->EPERM:{setpgid_den} setsid->EPERM:{setsid_den} unshare->EPERM:{unshare_den} allowed_write:{write_ok} alive:{alive})",
        if pass { "PASS" } else { "FAIL" }
    ));
    pass
}

fn p2d() -> bool {
    say("");
    say("=== P2d: waitpid from the daemon namespace reaps the namespaced child ===");
    let (pid, rfd) = match spawn_child(M_REAP, 0, 0, true) {
        Ok(v) => v,
        Err(e) => {
            say(format!("P2d FAIL spawn: {e}"));
            return false;
        }
    };
    say(format!("P2d spawned reap child pid={pid} (namespaced)"));
    let mut r = Rdr::new(rfd);
    let entered = r.wait_for("reap-child-entered", Duration::from_secs(3));
    say(format!("P2d child-entered={entered}"));
    let w = waitpid_poll(pid, Duration::from_millis(100));
    say(format!(
        "P2d waitpid(WNOHANG) while child sleeping (expect Ok(None)): {w:?}"
    ));
    std::thread::sleep(Duration::from_millis(900));
    let b = waitpid_poll(pid, Duration::from_secs(3));
    say(format!(
        "P2d waitpid blocking reap: {:?}",
        b.map(|st| st.map(status_desc))
    ));
    let proc_gone = !proc_has_pid(pid);
    say(format!("P2d /proc/{pid} gone after reap: {proc_gone}"));
    let second = waitpid_poll(pid, Duration::from_millis(200));
    say(format!(
        "P2d second waitpid (expect Err(ECHILD={})): {second:?}",
        libc::ECHILD
    ));
    let rest = r.drain_all(Duration::from_millis(500));
    for l in &rest {
        say(format!("P2d child> {l}"));
    }
    unsafe { libc::close(rfd) };

    let wnh = matches!(w, Ok(None));
    let reaped = matches!(b, Ok(Some(st)) if libc::WIFEXITED(st));
    let ech = matches!(second, Err(e) if e == libc::ECHILD);
    let pass = entered && wnh && reaped && proc_gone && ech;
    say(format!(
        "P2d VERDICT: {} (WNOHANG=still_running:{wnh} blocking_reap_wifexited:{reaped} /proc_pid_removed:{proc_gone} second_waitpid_ECHILD:{ech})",
        if pass { "PASS" } else { "FAIL" }
    ));
    pass
}

fn p3_common(tag: &str, mode: i32) -> bool {
    say("");
    say(format!(
        "=== P3{tag}: daemon retains kill rights across the boundary ==="
    ));
    let (pid, rfd) = match spawn_child(mode, 0, 0, true) {
        Ok(v) => v,
        Err(e) => {
            say(format!("P3{tag} FAIL spawn: {e}"));
            return false;
        }
    };
    say(format!(
        "P3{tag} spawned session-leader child pid={pid} (parent-ns pid)"
    ));
    let ctag = format!("pg3{tag}");
    let mut r = Rdr::new(rfd);
    let lines = r.drain_all(Duration::from_secs(4));
    for l in &lines {
        say(format!("P3{tag} child> {l}"));
    }
    let gc_ready = lines
        .iter()
        .any(|l| l == &format!("{ctag}-grandchild-pausing"));
    let c_ready = lines.iter().any(|l| l == &format!("{ctag}-child-waiting"));
    say(format!(
        "P3{tag} grandchild_ready={gc_ready} child_ready={c_ready}"
    ));

    let gc = find_grandchild(pid);
    say(format!("P3{tag} grandchild parent-ns pid: {:?}", gc));
    let child_f = stat_fields(pid);
    let gc_f = gc.and_then(|g| stat_fields(g));
    if let Some(f) = &child_f {
        // fields: [0]=state [1]=ppid [2]=pgrp [3]=session
        say(format!(
            "P3{tag} child  /proc stat: state={} ppid={} pgrp={} session={}",
            f.get(0).unwrap_or(&"?".into()),
            f.get(1).unwrap_or(&"?".into()),
            f.get(2).unwrap_or(&"?".into()),
            f.get(3).unwrap_or(&"?".into())
        ));
    }
    if let Some(f) = &gc_f {
        say(format!(
            "P3{tag} grandchild /proc stat: state={} ppid={} pgrp={} session={}",
            f.get(0).unwrap_or(&"?".into()),
            f.get(1).unwrap_or(&"?".into()),
            f.get(2).unwrap_or(&"?".into()),
            f.get(3).unwrap_or(&"?".into())
        ));
    }
    unsafe { libc::close(rfd) };
    let _ = r.drain_all(Duration::from_millis(100));

    let pgid = pid;
    let kr = unsafe { libc::kill(-pgid, libc::SIGKILL) };
    say(format!(
        "P3{tag} kill(-pgid={pgid}, SIGKILL) from parent ns = {kr} errno={}",
        errno()
    ));
    let c_reap = waitpid_poll(pid, Duration::from_secs(3));
    say(format!(
        "P3{tag} waitpid child: {:?}",
        c_reap.map(|st| st.map(status_desc))
    ));
    let g_reap = gc.and_then(|g| waitpid_poll(g, Duration::from_secs(3)).ok());
    say(format!(
        "P3{tag} waitpid grandchild: {:?}",
        g_reap.map(|st| st.map(status_desc))
    ));
    let c_gone = !proc_has_pid(pid);
    let g_gone = gc.map(|g| !proc_has_pid(g)).unwrap_or(false);
    say(format!(
        "P3{tag} /proc child gone: {c_gone}, grandchild gone: {g_gone}"
    ));

    let group_kill_ok = kr == 0;
    let both_reaped = matches!(c_reap, Ok(Some(_))) && matches!(g_reap, Some(Some(_)));
    let pass =
        gc_ready && c_ready && gc.is_some() && group_kill_ok && both_reaped && c_gone && g_gone;
    say(format!(
        "P3{tag} VERDICT: {} (both_visible_in_proc:{} same_pgrp/sid==child_pid:{} kill(-pgid)==0:{group_kill_ok} child_reaped:{both_reaped} grandchild_reaped:{} /proc_cleared:{c_gone}/{g_gone})",
        if pass { "PASS" } else { "FAIL" },
        gc.is_some(),
        {
            let same = child_f
                .as_ref()
                .zip(gc_f.as_ref())
                .map(|(cf, gf)| {
                    cf.get(2) == Some(&format!("{pgid}"))
                        && gf.get(2) == Some(&format!("{pgid}"))
                        && cf.get(3) == Some(&format!("{pgid}"))
                        && gf.get(3) == Some(&format!("{pgid}"))
                })
                .unwrap_or(false);
            same
        },
        matches!(g_reap, Some(Some(_)))
    ));
    pass
}

fn p3a() -> bool {
    p3_common("a", M_PG3A)
}

fn p3b() -> bool {
    p3_common("b", M_PG3B)
}

fn main() {
    let _ = std::fs::remove_file(LOG);
    say("=== newpid_probe start ===");
    let mut un = unsafe { std::mem::zeroed::<libc::utsname>() };
    if unsafe { libc::uname(&mut un) } == 0 {
        let c = |b: [libc::c_char; 65]| {
            unsafe { std::ffi::CStr::from_ptr(b.as_ptr()) }
                .to_string_lossy()
                .into_owned()
        };
        say(format!(
            "platform: sysname={} nodename={} release={} version={} machine={}",
            c(un.sysname),
            c(un.nodename),
            c(un.release),
            c(un.version),
            c(un.machine)
        ));
    }

    let newpid_ok = t0();
    t0b();
    if !newpid_ok {
        say("T0 FAIL: CLONE_NEWPID creation is blocked in this privilege context.");
        say("VERDICT: namespace approach FAILS on this target (EPERM/blocked).");
    }

    let mut results: Vec<(&str, bool)> = Vec::new();
    results.push(("T0", newpid_ok));
    results.push(("P1a", p1a()));

    if !newpid_ok {
        for (name, _) in [
            ("P1b", false),
            ("P2a", false),
            ("P2b", false),
            ("P2c", false),
            ("P2d", false),
            ("P3a", false),
            ("P3b", false),
        ] {
            results.push((name, false));
            say(format!("{name} SKIPPED (namespace blocked)"));
        }
    } else {
        results.push(("P1b", p1b()));
        results.push(("P2a", p2a()));
        results.push(("P2b", p2b()));
        results.push(("P2c", p2c()));
        results.push(("P2d", p2d()));
        results.push(("P3a", p3a()));
        results.push(("P3b", p3b()));
    }

    say("");
    say("=== SUMMARY ===");
    for (name, ok) in &results {
        say(format!("{name}: {}", if *ok { "PASS" } else { "FAIL" }));
    }
    let all = results.iter().all(|(_, ok)| *ok);
    say(format!(
        "OVERALL: {}",
        if all { "ALL PASS" } else { "SOME FAIL" }
    ));
}