memf-linux 0.2.1

//! Detect processes running from deleted executables.
//!
//! When malware deletes its binary after execution, the process keeps running
//! but the `/proc/<pid>/exe` symlink (backed by `mm->exe_file->f_path->dentry->d_name`)
//! shows `(deleted)`. This is a strong indicator of malicious activity.
//!
//! MITRE ATT&CK: T1070.004 — Indicator Removal: File Deletion.
//!
//! Legitimate cases include package manager upgrades (apt, dpkg, yum, dnf, rpm)
//! where the old binary is replaced while the process is still running, and
//! kernel threads with empty exe paths.

use memf_core::object_reader::ObjectReader;
use memf_format::PhysicalMemoryProvider;
use serde::Serialize;

use crate::{Error, Result};

/// Information about a process whose executable may have been deleted.
#[derive(Debug, Clone, Serialize)]
pub struct DeletedExeInfo {
    /// Process ID.
    pub pid: u32,
    /// Process command name (`task_struct.comm`, max 16 chars).
    pub comm: String,
    /// Executable path as read from memory (may include "(deleted)" suffix).
    pub exe_path: String,
    /// Whether the executable path contains the "(deleted)" marker.
    pub is_deleted: bool,
    /// Whether this deleted executable is suspicious (not a known-benign case).
    pub is_suspicious: bool,
}

/// Classify whether a deleted executable is suspicious.
///
/// Returns `true` (suspicious) if:
/// - The exe path contains "(deleted)" AND
/// - The process is NOT a known-benign package manager process AND
/// - The exe path is not empty (kernel threads have no exe)
///
/// Returns `false` (benign) for:
/// - Normal executables (no "(deleted)" marker)
/// - Package manager processes (apt, dpkg, yum, dnf, rpm, etc.)
/// - Kernel threads with empty exe paths
/// - Processes with empty comm (likely kernel threads)
pub use crate::heuristics::classify_deleted_exe;

/// Walk the task list and detect processes running from deleted executables.
///
/// For each process, reads the `mm->exe_file->f_path->dentry->d_name` chain
/// to recover the executable path. If the path contains "(deleted)", the
/// process is flagged and classified.
///
/// Kernel threads (NULL mm) are silently skipped.
pub fn walk_deleted_exe<P: PhysicalMemoryProvider>(
    reader: &ObjectReader<P>,
) -> Result<Vec<DeletedExeInfo>> {
    let init_task_addr = reader
        .symbols()
        .symbol_address("init_task")
        .ok_or_else(|| Error::MissingKernelSymbol {
            name: "init_task".into(),
        })?;

    let tasks_offset = reader
        .symbols()
        .field_offset("task_struct", "tasks")
        .ok_or_else(|| Error::MissingField {
            struct_name: "task_struct".into(),
            field_name: "tasks".into(),
        })?;

    let head_vaddr = init_task_addr + tasks_offset;
    let task_addrs = reader.walk_list(head_vaddr, "task_struct", "tasks")?;

    let mut results = Vec::new();

    // Include init_task itself
    if let Some(info) = read_deleted_exe_info(reader, init_task_addr) {
        results.push(info);
    }

    for &task_addr in &task_addrs {
        if let Some(info) = read_deleted_exe_info(reader, task_addr) {
            results.push(info);
        }
    }

    results.sort_by_key(|r| r.pid);
    Ok(results)
}

/// Read the executable path for a single task and classify it.
///
/// Returns `None` for kernel threads (NULL mm) or if any field cannot be read.
fn read_deleted_exe_info<P: PhysicalMemoryProvider>(
    reader: &ObjectReader<P>,
    task_addr: u64,
) -> Option<DeletedExeInfo> {
    let pid: u32 = reader.read_field(task_addr, "task_struct", "pid").ok()?;
    let comm = reader
        .read_field_string(task_addr, "task_struct", "comm", 16)
        .unwrap_or_default();

    // Kernel threads have mm == NULL — skip them.
    let mm_ptr: u64 = reader.read_field(task_addr, "task_struct", "mm").ok()?;
    if mm_ptr == 0 {
        return None;
    }

    // Follow mm->exe_file (pointer to struct file).
    let exe_file_ptr: u64 = reader.read_field(mm_ptr, "mm_struct", "exe_file").ok()?;
    if exe_file_ptr == 0 {
        return None;
    }

    // Navigate exe_file->f_path.dentry to read the path name.
    let exe_path = read_file_dentry_name(reader, exe_file_ptr).unwrap_or_default();

    let is_deleted = exe_path.contains("(deleted)");
    let is_suspicious = classify_deleted_exe(&exe_path, &comm);

    Some(DeletedExeInfo {
        pid,
        comm,
        exe_path,
        is_deleted,
        is_suspicious,
    })
}

/// Read the dentry name from a `struct file` pointer via `f_path.dentry->d_name`.
///
/// Follows the embedded struct chain: `file.f_path` (embedded `struct path`) ->
/// `path.dentry` (pointer) -> `dentry.d_name` (embedded `struct qstr`) ->
/// `qstr.name` (pointer to string).
fn read_file_dentry_name<P: PhysicalMemoryProvider>(
    reader: &ObjectReader<P>,
    file_ptr: u64,
) -> Option<String> {
    let f_path_offset = reader.symbols().field_offset("file", "f_path")?;
    let dentry_in_path = reader.symbols().field_offset("path", "dentry")?;
    let d_name_offset = reader.symbols().field_offset("dentry", "d_name")?;
    let name_in_qstr = reader.symbols().field_offset("qstr", "name")?;

    // file.f_path is embedded; dentry is a pointer within the embedded path struct.
    let dentry_addr = file_ptr + f_path_offset + dentry_in_path;
    let dentry_raw = reader.read_bytes(dentry_addr, 8).ok()?;
    let dentry_ptr = u64::from_le_bytes(dentry_raw.try_into().ok()?);
    if dentry_ptr == 0 {
        return None;
    }

    // dentry.d_name is an embedded qstr; name is a pointer within qstr.
    let name_addr = dentry_ptr + d_name_offset + name_in_qstr;
    let name_raw = reader.read_bytes(name_addr, 8).ok()?;
    let name_ptr = u64::from_le_bytes(name_raw.try_into().ok()?);
    if name_ptr == 0 {
        return None;
    }

    reader.read_string(name_ptr, 256).ok()
}

// ---------------------------------------------------------------------------
// Pure-logic helpers and finding type for LD_PRELOAD / Father rootkit detection
// ---------------------------------------------------------------------------

/// Returns `true` if `exe_path` carries a `(deleted)` suffix.
///
/// This covers both the kernel's canonical `" (deleted)"` (space-prefixed) and
/// the bare `"(deleted)"` form occasionally written by userspace tools.
pub fn is_deleted_exe(exe_path: &str) -> bool {
    exe_path.ends_with(" (deleted)") || exe_path.ends_with("(deleted)")
}

/// Returns the path with any `(deleted)` suffix stripped, trimming trailing
/// whitespace that the kernel inserts before the marker.
///
/// If the path carries no deleted marker the original string slice is returned
/// unchanged.
pub fn strip_deleted_suffix(exe_path: &str) -> &str {
    if let Some(stripped) = exe_path.strip_suffix("(deleted)") {
        stripped.trim_end()
    } else {
        exe_path
    }
}

/// A lightweight finding produced by the pure-logic deleted-exe classifier,
/// suitable for use without a full memory-image reader.
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub struct DeletedExeFinding {
    /// Process ID.
    pub pid: u32,
    /// Process name (`task_struct.comm`, max 16 chars).
    pub comm: String,
    /// Full exe path as seen in memory — includes the `(deleted)` suffix.
    pub exe_path: String,
    /// Exe path with the `(deleted)` suffix and trailing whitespace stripped.
    pub original_path: String,
}

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

    const KNOWN_BENIGN_COMMS: &[&str] = &[
        "apt",
        "apt-get",
        "apt-check",
        "aptd",
        "dpkg",
        "dpkg-deb",
        "yum",
        "dnf",
        "rpm",
        "rpmdb",
        "packagekitd",
        "unattended-upgr",
    ];
    use memf_core::test_builders::{flags, PageTableBuilder, SyntheticPhysMem};
    use memf_core::vas::{TranslationMode, VirtualAddressSpace};
    use memf_symbols::isf::IsfResolver;
    use memf_symbols::test_builders::IsfBuilder;

    // --- classify_deleted_exe unit tests ---

    #[test]
    fn classify_normal_benign() {
        // A normal executable that is NOT deleted should never be suspicious.
        assert!(
            !classify_deleted_exe("/usr/bin/nginx", "nginx"),
            "a live (non-deleted) executable must not be flagged suspicious"
        );
    }

    #[test]
    fn classify_deleted_suspicious() {
        // A deleted executable from an unknown process IS suspicious.
        assert!(
            classify_deleted_exe("/tmp/.x11 (deleted)", "payload"),
            "a deleted exe from unknown process 'payload' must be suspicious"
        );
    }

    #[test]
    fn classify_deleted_apt_benign() {
        // apt running from a deleted exe during upgrade is benign.
        assert!(
            !classify_deleted_exe("/usr/bin/apt (deleted)", "apt"),
            "apt with deleted exe during package upgrade must not be suspicious"
        );
    }

    #[test]
    fn classify_deleted_dpkg_benign() {
        // dpkg running from a deleted exe during upgrade is benign.
        assert!(
            !classify_deleted_exe("/usr/bin/dpkg (deleted)", "dpkg"),
            "dpkg with deleted exe during package upgrade must not be suspicious"
        );
    }

    #[test]
    fn classify_kernel_thread_benign() {
        // Kernel threads have empty comm or empty exe path — not suspicious.
        assert!(
            !classify_deleted_exe("", ""),
            "kernel thread with empty exe and comm must not be suspicious"
        );
    }

    #[test]
    fn classify_empty_path_benign() {
        // Empty exe path (kernel thread) with a comm name should not be suspicious
        // even though it technically can't contain "(deleted)" — test the guard.
        assert!(
            !classify_deleted_exe("", "kworker/0:1"),
            "empty exe path must not be flagged suspicious"
        );
    }

    #[test]
    fn classify_deleted_yum_benign() {
        // yum running from a deleted exe during upgrade is benign.
        assert!(
            !classify_deleted_exe("/usr/bin/yum (deleted)", "yum"),
            "yum with deleted exe during package upgrade must not be suspicious"
        );
    }

    #[test]
    fn classify_deleted_with_suspicious_name() {
        // A process with a suspicious-looking name running from /dev/shm (deleted).
        assert!(
            classify_deleted_exe("/dev/shm/.hidden (deleted)", "a]"),
            "deleted exe from /dev/shm with obfuscated name must be suspicious"
        );
    }

    #[test]
    fn classify_deleted_empty_comm_benign() {
        // Deleted path but empty comm → kernel thread, not suspicious
        assert!(
            !classify_deleted_exe("/tmp/.evil (deleted)", ""),
            "empty comm with deleted exe must not be suspicious"
        );
    }

    #[test]
    fn classify_all_known_benign_comms() {
        // Every entry in KNOWN_BENIGN_COMMS must be suppressed
        for comm in KNOWN_BENIGN_COMMS {
            let path = format!("/usr/bin/{comm} (deleted)");
            assert!(
                !classify_deleted_exe(&path, comm),
                "known-benign comm '{comm}' must not be flagged suspicious"
            );
        }
    }

    #[test]
    fn classify_benign_comm_case_insensitive() {
        // Classification is case-insensitive for known-benign names
        assert!(!classify_deleted_exe("/usr/bin/APT (deleted)", "APT"));
        assert!(!classify_deleted_exe("/usr/bin/Dpkg (deleted)", "Dpkg"));
        assert!(!classify_deleted_exe("/usr/bin/YUM (deleted)", "YUM"));
    }

    #[test]
    fn classify_near_benign_name_suspicious() {
        // "apt2" is NOT in the benign list → suspicious
        assert!(classify_deleted_exe("/usr/bin/apt2 (deleted)", "apt2"));
        // "dpkg-query" is not in the list → suspicious
        assert!(classify_deleted_exe(
            "/usr/bin/dpkg-query (deleted)",
            "dpkg-query"
        ));
    }

    #[test]
    fn classify_deleted_exe_info_struct_fields() {
        let info = DeletedExeInfo {
            pid: 999,
            comm: "evil".to_string(),
            exe_path: "/tmp/.x (deleted)".to_string(),
            is_deleted: true,
            is_suspicious: true,
        };
        let cloned = info.clone();
        assert_eq!(cloned.pid, 999);
        assert!(cloned.is_deleted);
        assert!(cloned.is_suspicious);
        let dbg = format!("{cloned:?}");
        assert!(dbg.contains("evil"));
    }

    #[test]
    fn classify_deleted_exe_info_serializes_to_json() {
        let info = DeletedExeInfo {
            pid: 42,
            comm: "malware".to_string(),
            exe_path: "/dev/shm/.bin (deleted)".to_string(),
            is_deleted: true,
            is_suspicious: true,
        };
        let json = serde_json::to_string(&info).unwrap();
        assert!(json.contains("\"pid\":42"));
        assert!(json.contains("\"is_deleted\":true"));
        assert!(json.contains("\"is_suspicious\":true"));
    }

    // --- walk_deleted_exe integration test ---

    /// Helper: build an ObjectReader with no init_task symbol.
    fn make_reader_no_symbol() -> ObjectReader<SyntheticPhysMem> {
        let isf = IsfBuilder::new()
            .add_struct("task_struct", 128)
            .add_field("task_struct", "pid", 0, "int")
            .add_field("task_struct", "tasks", 16, "list_head")
            .add_struct("list_head", 16)
            .add_field("list_head", "next", 0, "pointer")
            .add_field("list_head", "prev", 8, "pointer")
            .build_json();

        let resolver = IsfResolver::from_value(&isf).unwrap();
        let (cr3, mem) = PageTableBuilder::new().build();
        let vas = VirtualAddressSpace::new(mem, cr3, TranslationMode::X86_64FourLevel);
        ObjectReader::new(vas, Box::new(resolver))
    }

    #[test]
    fn walk_no_symbol_returns_error() {
        // Without init_task symbol, walk should return an error (not panic).
        let reader = make_reader_no_symbol();
        let result = walk_deleted_exe(&reader);
        assert!(
            matches!(result, Err(crate::Error::MissingKernelSymbol { ref name }) if name == "init_task"),
            "expected MissingKernelSymbol {{name: \"init_task\"}}, got {result:?}"
        );
    }

    #[test]
    fn walk_missing_tasks_field_returns_missing_field() {
        let isf = IsfBuilder::new()
            .add_struct("task_struct", 128)
            .add_field("task_struct", "pid", 0, "int")
            // tasks intentionally omitted
            .add_struct("list_head", 16)
            .add_field("list_head", "next", 0, "pointer")
            .add_field("list_head", "prev", 8, "pointer")
            .add_symbol("init_task", 0xFFFF_8000_0010_0000)
            .build_json();
        let resolver = IsfResolver::from_value(&isf).unwrap();
        let (cr3, mem) = PageTableBuilder::new().build();
        let vas = VirtualAddressSpace::new(mem, cr3, TranslationMode::X86_64FourLevel);
        let reader: ObjectReader<SyntheticPhysMem> = ObjectReader::new(vas, Box::new(resolver));
        let result = walk_deleted_exe(&reader);
        assert!(
            matches!(result, Err(crate::Error::MissingField { ref struct_name, ref field_name }) if struct_name == "task_struct" && field_name == "tasks"),
            "expected MissingField task_struct.tasks, got {result:?}"
        );
    }

    // --- walk_deleted_exe: symbol present, self-pointing tasks list, mm != 0, exe_file == 0 ---
    // Exercises read_deleted_exe_info: mm pointer is non-null (reads ok), but
    // mm_struct.exe_file == 0 → returns None → result stays empty.
    #[test]
    fn walk_deleted_exe_mm_non_null_exe_file_null_returns_empty() {
        let tasks_offset: u64 = 0x10;
        let mm_offset: u64 = 0x30;
        let sym_vaddr: u64 = 0xFFFF_8800_0090_0000;
        let sym_paddr: u64 = 0x0090_0000; // < 16 MB
        let mm_vaddr: u64 = 0xFFFF_8800_0091_0000;
        let mm_paddr: u64 = 0x0091_0000;

        // task page
        let mut task_page = [0u8; 4096];
        // pid = 5
        task_page[0..4].copy_from_slice(&5u32.to_le_bytes());
        // tasks self-pointing
        let self_ptr = sym_vaddr + tasks_offset;
        task_page[tasks_offset as usize..tasks_offset as usize + 8]
            .copy_from_slice(&self_ptr.to_le_bytes());
        // mm at offset 0x30 → non-zero (points to mm page)
        task_page[mm_offset as usize..mm_offset as usize + 8]
            .copy_from_slice(&mm_vaddr.to_le_bytes());
        // comm = "worker"
        task_page[0x20..0x26].copy_from_slice(b"worker");

        // mm page: exe_file at offset 0x18 = 0 (null)
        let mm_page = [0u8; 4096];

        let isf = IsfBuilder::new()
            .add_symbol("init_task", sym_vaddr)
            .add_struct("list_head", 0x10)
            .add_field("list_head", "next", 0x00, "pointer")
            .add_field("list_head", "prev", 0x08, "pointer")
            .add_struct("task_struct", 0x400)
            .add_field("task_struct", "tasks", tasks_offset, "pointer")
            .add_field("task_struct", "pid", 0x00, "unsigned int")
            .add_field("task_struct", "comm", 0x20, "char")
            .add_field("task_struct", "mm", mm_offset, "pointer")
            .add_struct("mm_struct", 0x200)
            .add_field("mm_struct", "exe_file", 0x18, "pointer")
            .build_json();
        let resolver = IsfResolver::from_value(&isf).unwrap();

        let (cr3, mem) = PageTableBuilder::new()
            .map_4k(sym_vaddr, sym_paddr, flags::WRITABLE)
            .write_phys(sym_paddr, &task_page)
            .map_4k(mm_vaddr, mm_paddr, flags::WRITABLE)
            .write_phys(mm_paddr, &mm_page)
            .build();

        let vas = VirtualAddressSpace::new(mem, cr3, TranslationMode::X86_64FourLevel);
        let reader: ObjectReader<SyntheticPhysMem> = ObjectReader::new(vas, Box::new(resolver));

        let result = walk_deleted_exe(&reader).unwrap();
        assert!(
            result.is_empty(),
            "mm non-null but exe_file==0 → read_deleted_exe_info returns None → empty"
        );
    }

    // --- walk_deleted_exe: exe_file non-null, dentry chain fully readable, non-deleted path ---
    // Exercises read_deleted_exe_info returning Some (lines 120, 124-126), and
    // read_file_dentry_name (lines 177-203) on a path without "(deleted)".
    #[test]
    fn walk_deleted_exe_full_chain_no_deleted_marker() {
        use memf_core::test_builders::flags as ptf;

        // Layout (all physical addrs < 16 MB):
        //   sym_vaddr  = init_task                tasks @ 0x10, mm @ 0x30, pid @ 0, comm @ 0x20
        //   mm_vaddr   = mm_struct                exe_file @ 0x18
        //   file_vaddr = struct file              f_path embedded (f_path_offset=0x10)
        //   dentry_vaddr = dentry struct          d_name embedded (d_name_offset=0x08)
        //   name_vaddr   = actual name string     "/usr/bin/bash\0"
        let sym_vaddr: u64 = 0xFFFF_8800_00A0_0000;
        let sym_paddr: u64 = 0x00A0_0000;
        let mm_vaddr: u64 = 0xFFFF_8800_00A1_0000;
        let mm_paddr: u64 = 0x00A1_0000;
        let file_vaddr: u64 = 0xFFFF_8800_00A2_0000;
        let file_paddr: u64 = 0x00A2_0000;
        let dentry_vaddr: u64 = 0xFFFF_8800_00A3_0000;
        let dentry_paddr: u64 = 0x00A3_0000;
        let name_vaddr: u64 = 0xFFFF_8800_00A4_0000;
        let name_paddr: u64 = 0x00A4_0000;

        let tasks_offset: u64 = 0x10;
        let mm_offset: u64 = 0x30;
        let f_path_offset: u64 = 0x10; // offset of embedded path inside file
        let dentry_in_path: u64 = 0x00; // offset of dentry* inside path
        let d_name_offset: u64 = 0x08; // offset of embedded qstr inside dentry
        let name_in_qstr: u64 = 0x00; // offset of name* inside qstr

        // init_task page
        let mut task_page = [0u8; 4096];
        task_page[0..4].copy_from_slice(&7u32.to_le_bytes()); // pid=7
        let self_ptr = sym_vaddr + tasks_offset;
        task_page[tasks_offset as usize..tasks_offset as usize + 8]
            .copy_from_slice(&self_ptr.to_le_bytes());
        task_page[0x20..0x25].copy_from_slice(b"bash\0");
        task_page[mm_offset as usize..mm_offset as usize + 8]
            .copy_from_slice(&mm_vaddr.to_le_bytes());

        // mm_struct page: exe_file at 0x18
        let mut mm_page = [0u8; 4096];
        mm_page[0x18..0x20].copy_from_slice(&file_vaddr.to_le_bytes());

        // file page: dentry ptr at f_path_offset + dentry_in_path = 0x10
        let mut file_page = [0u8; 4096];
        file_page[0x10..0x18].copy_from_slice(&dentry_vaddr.to_le_bytes());

        // dentry page: name ptr at d_name_offset + name_in_qstr = 0x08
        let mut dentry_page = [0u8; 4096];
        dentry_page[0x08..0x10].copy_from_slice(&name_vaddr.to_le_bytes());

        // name string page
        let mut name_page = [0u8; 4096];
        name_page[..14].copy_from_slice(b"/usr/bin/bash\0");

        let isf = IsfBuilder::new()
            .add_symbol("init_task", sym_vaddr)
            .add_struct("list_head", 0x10)
            .add_field("list_head", "next", 0x00, "pointer")
            .add_field("list_head", "prev", 0x08, "pointer")
            .add_struct("task_struct", 0x400)
            .add_field("task_struct", "tasks", tasks_offset, "pointer")
            .add_field("task_struct", "pid", 0x00, "unsigned int")
            .add_field("task_struct", "comm", 0x20, "char")
            .add_field("task_struct", "mm", mm_offset, "pointer")
            .add_struct("mm_struct", 0x200)
            .add_field("mm_struct", "exe_file", 0x18, "pointer")
            .add_struct("file", 0x200)
            .add_field("file", "f_path", f_path_offset, "pointer")
            .add_struct("path", 0x20)
            .add_field("path", "dentry", dentry_in_path, "pointer")
            .add_struct("dentry", 0x200)
            .add_field("dentry", "d_name", d_name_offset, "pointer")
            .add_struct("qstr", 0x20)
            .add_field("qstr", "name", name_in_qstr, "pointer")
            .build_json();
        let resolver = IsfResolver::from_value(&isf).unwrap();

        let (cr3, mem) = PageTableBuilder::new()
            .map_4k(sym_vaddr, sym_paddr, ptf::WRITABLE)
            .write_phys(sym_paddr, &task_page)
            .map_4k(mm_vaddr, mm_paddr, ptf::WRITABLE)
            .write_phys(mm_paddr, &mm_page)
            .map_4k(file_vaddr, file_paddr, ptf::WRITABLE)
            .write_phys(file_paddr, &file_page)
            .map_4k(dentry_vaddr, dentry_paddr, ptf::WRITABLE)
            .write_phys(dentry_paddr, &dentry_page)
            .map_4k(name_vaddr, name_paddr, ptf::WRITABLE)
            .write_phys(name_paddr, &name_page)
            .build();

        let vas = VirtualAddressSpace::new(mem, cr3, TranslationMode::X86_64FourLevel);
        let reader: ObjectReader<SyntheticPhysMem> = ObjectReader::new(vas, Box::new(resolver));

        let result = walk_deleted_exe(&reader).unwrap();
        // init_task (pid=7, comm="bash") has a fully readable exe path that is NOT deleted.
        assert_eq!(
            result.len(),
            1,
            "init_task with full dentry chain should produce one entry"
        );
        assert_eq!(result[0].pid, 7);
        assert!(
            !result[0].is_deleted,
            "path without (deleted) must not be flagged"
        );
        assert!(!result[0].is_suspicious);
    }

    // --- walk_deleted_exe: symbol present, self-pointing tasks list, mm == 0 → exercises body ---
    // Exercises the task-list body and `read_deleted_exe_info`: init_task has mm=0 (kernel thread),
    // so it is skipped, and walk_list returns empty → result is empty but no error.
    #[test]
    fn walk_deleted_exe_symbol_present_kernel_thread_returns_empty() {
        // tasks at offset 0x10; pid at 0x00; comm at 0x20; mm at 0x30.
        let tasks_offset: u64 = 0x10;
        let sym_vaddr: u64 = 0xFFFF_8800_0080_0000;
        let sym_paddr: u64 = 0x0080_0000; // unique, < 16 MB

        let isf = IsfBuilder::new()
            .add_symbol("init_task", sym_vaddr)
            .add_struct("list_head", 0x10)
            .add_field("list_head", "next", 0x00, "pointer")
            .add_struct("task_struct", 0x400)
            .add_field("task_struct", "tasks", tasks_offset, "pointer")
            .add_field("task_struct", "pid", 0x00, "unsigned int")
            .add_field("task_struct", "comm", 0x20, "char")
            .add_field("task_struct", "mm", 0x30, "pointer")
            .build_json();
        let resolver = IsfResolver::from_value(&isf).unwrap();

        // Build init_task page: tasks.next self-pointing, mm = 0 (kernel thread).
        let mut page = [0u8; 4096];
        let self_ptr = sym_vaddr + tasks_offset;
        page[tasks_offset as usize..tasks_offset as usize + 8]
            .copy_from_slice(&self_ptr.to_le_bytes());
        // mm at 0x30 remains 0 → read_deleted_exe_info returns None.

        let (cr3, mem) = PageTableBuilder::new()
            .map_4k(sym_vaddr, sym_paddr, flags::WRITABLE)
            .write_phys(sym_paddr, &page)
            .build();

        let vas = VirtualAddressSpace::new(mem, cr3, TranslationMode::X86_64FourLevel);
        let reader: ObjectReader<SyntheticPhysMem> = ObjectReader::new(vas, Box::new(resolver));

        let result = walk_deleted_exe(&reader).unwrap();
        assert!(
            result.is_empty(),
            "init_task with mm=0 → skipped as kernel thread → empty results"
        );
    }

    // --- walk_deleted_exe: walk_list returns a non-empty task list → exercises the for loop body ---
    // init_task has mm=0 (kernel thread, skipped). A linked task has mm != 0 but exe_file = 0
    // → read_deleted_exe_info returns None → loop body runs but produces no result.
    #[test]
    fn walk_deleted_exe_task_list_loop_body_covered() {
        use memf_core::test_builders::flags;

        let tasks_offset: u64 = 0x10;
        let mm_offset: u64 = 0x30;

        // init_task (kernel thread, mm=0)
        let init_vaddr: u64 = 0xFFFF_8800_00B0_0000;
        let init_paddr: u64 = 0x00B0_0000;

        // task2 (non-kernel, mm != 0 → exe_file = 0 → skipped)
        let task2_vaddr: u64 = 0xFFFF_8800_00B1_0000;
        let task2_paddr: u64 = 0x00B1_0000;

        // mm page for task2
        let mm2_vaddr: u64 = 0xFFFF_8800_00B2_0000;
        let mm2_paddr: u64 = 0x00B2_0000;

        // init_task page: tasks.next → task2, mm = 0
        let mut init_page = [0u8; 4096];
        // tasks.next at offset 0x10 → task2_vaddr (pointing at task2's tasks field)
        let task2_tasks_vaddr = task2_vaddr + tasks_offset;
        init_page[tasks_offset as usize..tasks_offset as usize + 8]
            .copy_from_slice(&task2_tasks_vaddr.to_le_bytes());
        // mm at 0x30 = 0
        // pid = 0 at offset 0

        // task2 page: tasks.next → back to init_task tasks (forms a cycle-terminating list)
        let mut task2_page = [0u8; 4096];
        let init_tasks_vaddr = init_vaddr + tasks_offset;
        task2_page[tasks_offset as usize..tasks_offset as usize + 8]
            .copy_from_slice(&init_tasks_vaddr.to_le_bytes()); // tasks.next → head
                                                               // pid at 0x00 = 8
        task2_page[0x00..0x04].copy_from_slice(&8u32.to_le_bytes());
        // comm at 0x20 = "proc2"
        task2_page[0x20..0x25].copy_from_slice(b"proc2");
        // mm at 0x30 = mm2_vaddr (non-zero → has mm, exe_file at offset 0x18 = 0 → skipped)
        task2_page[mm_offset as usize..mm_offset as usize + 8]
            .copy_from_slice(&mm2_vaddr.to_le_bytes());

        // mm2 page: exe_file at offset 0x18 = 0 → read_deleted_exe_info returns None
        let mm2_page = [0u8; 4096];

        let isf = IsfBuilder::new()
            .add_symbol("init_task", init_vaddr)
            .add_struct("list_head", 0x10)
            .add_field("list_head", "next", 0x00, "pointer")
            .add_field("list_head", "prev", 0x08, "pointer")
            .add_struct("task_struct", 0x400)
            .add_field("task_struct", "tasks", tasks_offset, "pointer")
            .add_field("task_struct", "pid", 0x00, "unsigned int")
            .add_field("task_struct", "comm", 0x20, "char")
            .add_field("task_struct", "mm", mm_offset, "pointer")
            .add_struct("mm_struct", 0x200)
            .add_field("mm_struct", "exe_file", 0x18, "pointer")
            .build_json();
        let resolver = IsfResolver::from_value(&isf).unwrap();

        let (cr3, mem) = PageTableBuilder::new()
            .map_4k(init_vaddr, init_paddr, flags::WRITABLE)
            .write_phys(init_paddr, &init_page)
            .map_4k(task2_vaddr, task2_paddr, flags::WRITABLE)
            .write_phys(task2_paddr, &task2_page)
            .map_4k(mm2_vaddr, mm2_paddr, flags::WRITABLE)
            .write_phys(mm2_paddr, &mm2_page)
            .build();

        let vas = VirtualAddressSpace::new(mem, cr3, TranslationMode::X86_64FourLevel);
        let reader: ObjectReader<SyntheticPhysMem> = ObjectReader::new(vas, Box::new(resolver));

        // walk_list should find task2 in the list. init_task has mm=0 → skipped.
        // task2 has exe_file=0 → skipped. Result is empty but loop body executed.
        let result = walk_deleted_exe(&reader).unwrap();
        assert!(
            result.is_empty(),
            "both tasks skipped (mm=0 or exe_file=0) → empty results, but loop body was exercised"
        );
    }

    // --- walk_deleted_exe: full chain produces a (deleted) exe entry ---
    // Exercises lines 119-120 (init_task result pushed) and 160-162 (is_deleted=true, is_suspicious).
    #[test]
    fn walk_deleted_exe_full_chain_with_deleted_marker() {
        use memf_core::test_builders::flags as ptf;

        let sym_vaddr: u64 = 0xFFFF_8800_00C0_0000;
        let sym_paddr: u64 = 0x00C0_0000;
        let mm_vaddr: u64 = 0xFFFF_8800_00C1_0000;
        let mm_paddr: u64 = 0x00C1_0000;
        let file_vaddr: u64 = 0xFFFF_8800_00C2_0000;
        let file_paddr: u64 = 0x00C2_0000;
        let dentry_vaddr: u64 = 0xFFFF_8800_00C3_0000;
        let dentry_paddr: u64 = 0x00C3_0000;
        let name_vaddr: u64 = 0xFFFF_8800_00C4_0000;
        let name_paddr: u64 = 0x00C4_0000;

        let tasks_offset: u64 = 0x10;
        let mm_offset: u64 = 0x30;
        let f_path_offset: u64 = 0x10;
        let dentry_in_path: u64 = 0x00;
        let d_name_offset: u64 = 0x08;
        let name_in_qstr: u64 = 0x00;

        let mut task_page = [0u8; 4096];
        task_page[0..4].copy_from_slice(&3u32.to_le_bytes()); // pid=3
        let self_ptr = sym_vaddr + tasks_offset;
        task_page[tasks_offset as usize..tasks_offset as usize + 8]
            .copy_from_slice(&self_ptr.to_le_bytes()); // self-pointing
        task_page[0x20..0x27].copy_from_slice(b"payload");
        task_page[mm_offset as usize..mm_offset as usize + 8]
            .copy_from_slice(&mm_vaddr.to_le_bytes());

        let mut mm_page = [0u8; 4096];
        mm_page[0x18..0x20].copy_from_slice(&file_vaddr.to_le_bytes());

        let mut file_page = [0u8; 4096];
        file_page[0x10..0x18].copy_from_slice(&dentry_vaddr.to_le_bytes());

        let mut dentry_page = [0u8; 4096];
        dentry_page[0x08..0x10].copy_from_slice(&name_vaddr.to_le_bytes());

        let mut name_page = [0u8; 4096];
        let name_str = b"/tmp/.x11 (deleted)\0";
        name_page[..name_str.len()].copy_from_slice(name_str);

        let isf = IsfBuilder::new()
            .add_symbol("init_task", sym_vaddr)
            .add_struct("list_head", 0x10)
            .add_field("list_head", "next", 0x00, "pointer")
            .add_field("list_head", "prev", 0x08, "pointer")
            .add_struct("task_struct", 0x400)
            .add_field("task_struct", "tasks", tasks_offset, "pointer")
            .add_field("task_struct", "pid", 0x00, "unsigned int")
            .add_field("task_struct", "comm", 0x20, "char")
            .add_field("task_struct", "mm", mm_offset, "pointer")
            .add_struct("mm_struct", 0x200)
            .add_field("mm_struct", "exe_file", 0x18, "pointer")
            .add_struct("file", 0x200)
            .add_field("file", "f_path", f_path_offset, "pointer")
            .add_struct("path", 0x20)
            .add_field("path", "dentry", dentry_in_path, "pointer")
            .add_struct("dentry", 0x200)
            .add_field("dentry", "d_name", d_name_offset, "pointer")
            .add_struct("qstr", 0x20)
            .add_field("qstr", "name", name_in_qstr, "pointer")
            .build_json();
        let resolver = IsfResolver::from_value(&isf).unwrap();

        let (cr3, mem) = PageTableBuilder::new()
            .map_4k(sym_vaddr, sym_paddr, ptf::WRITABLE)
            .write_phys(sym_paddr, &task_page)
            .map_4k(mm_vaddr, mm_paddr, ptf::WRITABLE)
            .write_phys(mm_paddr, &mm_page)
            .map_4k(file_vaddr, file_paddr, ptf::WRITABLE)
            .write_phys(file_paddr, &file_page)
            .map_4k(dentry_vaddr, dentry_paddr, ptf::WRITABLE)
            .write_phys(dentry_paddr, &dentry_page)
            .map_4k(name_vaddr, name_paddr, ptf::WRITABLE)
            .write_phys(name_paddr, &name_page)
            .build();

        let vas = VirtualAddressSpace::new(mem, cr3, TranslationMode::X86_64FourLevel);
        let reader: ObjectReader<SyntheticPhysMem> = ObjectReader::new(vas, Box::new(resolver));

        let result = walk_deleted_exe(&reader).unwrap();
        assert_eq!(result.len(), 1, "init_task with deleted exe → one entry");
        assert_eq!(result[0].pid, 3);
        assert!(
            result[0].is_deleted,
            "exe_path contains (deleted) → is_deleted=true"
        );
        assert!(
            result[0].is_suspicious,
            "payload with deleted exe → suspicious"
        );
    }

    // ---------------------------------------------------------------------------
    // Tests for the new pure-logic helpers and DeletedExeFinding
    // ---------------------------------------------------------------------------

    #[test]
    fn is_deleted_exe_space_prefix_true() {
        assert!(is_deleted_exe("/usr/bin/xmrig (deleted)"));
    }

    #[test]
    fn is_deleted_exe_bare_suffix_true() {
        assert!(is_deleted_exe("/usr/bin/xmrig(deleted)"));
    }

    #[test]
    fn is_deleted_exe_live_binary_false() {
        assert!(!is_deleted_exe("/usr/bin/bash"));
    }

    #[test]
    fn is_deleted_exe_empty_string_false() {
        assert!(!is_deleted_exe(""));
    }

    #[test]
    fn strip_deleted_suffix_removes_space_prefix() {
        assert_eq!(
            strip_deleted_suffix("/usr/bin/xmrig (deleted)"),
            "/usr/bin/xmrig"
        );
    }

    #[test]
    fn strip_deleted_suffix_removes_bare_suffix() {
        assert_eq!(
            strip_deleted_suffix("/usr/bin/xmrig(deleted)"),
            "/usr/bin/xmrig"
        );
    }

    #[test]
    fn strip_deleted_suffix_no_marker_unchanged() {
        assert_eq!(strip_deleted_suffix("/usr/bin/bash"), "/usr/bin/bash");
    }

    #[test]
    fn strip_deleted_suffix_empty_unchanged() {
        assert_eq!(strip_deleted_suffix(""), "");
    }

    #[test]
    fn deleted_exe_finding_fields_constructible() {
        let finding = DeletedExeFinding {
            pid: 999,
            comm: "evil".to_string(),
            exe_path: "/tmp/.x (deleted)".to_string(),
            original_path: "/tmp/.x".to_string(),
        };
        assert_eq!(finding.pid, 999);
        assert_eq!(finding.original_path, "/tmp/.x");
    }

    #[test]
    fn deleted_exe_finding_serializes_to_json() {
        let finding = DeletedExeFinding {
            pid: 42,
            comm: "malware".to_string(),
            exe_path: "/dev/shm/.bin (deleted)".to_string(),
            original_path: "/dev/shm/.bin".to_string(),
        };
        let json = serde_json::to_string(&finding).unwrap();
        assert!(json.contains("\"pid\":42"));
        assert!(json.contains("\"exe_path\""));
        assert!(json.contains("\"original_path\""));
    }

    #[test]
    fn deleted_exe_finding_clone_and_debug() {
        let finding = DeletedExeFinding {
            pid: 7,
            comm: "sh".to_string(),
            exe_path: "/bin/sh (deleted)".to_string(),
            original_path: "/bin/sh".to_string(),
        };
        let cloned = finding.clone();
        let dbg = format!("{cloned:?}");
        assert!(dbg.contains("DeletedExeFinding"));
    }
}