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sys_fstat / sys_stat returns meaningful st_mtime. Why it matters: make compares st_mtime of source and object files to decide what to rebuild; a zero or stale timestamp breaks incremental builds entirely. Focus on `sys_linux_fstat` and `make` in `kernel/src/arch/x86_64/syscall.rs` while you trace the snippet.

fn sys_linux_fstat(fd: u64, stat_ptr: u64) -> u64 {
    let fd_idx = fd as usize;
    if fd_idx >= MAX_FDS {
        return NEG_EBADF;
    }
    let entry = match current_fd_entry(fd_idx) {
        Some(e) => e,
        None => return NEG_EBADF,
    };
    // x86_64 stat struct layout (144 bytes):
    //  0: st_dev (u64)      8: st_ino (u64)    16: st_nlink (u64)
    // 24: st_mode (u32)    28: st_uid (u32)    32: st_gid (u32)
    // 36: __pad0 (u32)     40: st_rdev (u64)   48: st_size (i64)
    // 56: st_blksize (i64) 64: st_blocks (i64)
    let mut stat = [0u8; 144];
    let blksize: u64 = 4096;

    // Determine mode, uid, gid, size, rdev based on backend type.
    let (mode, uid, gid, size, rdev): (u32, u32, u32, u64, u64) = match &entry.backend {
        FdBackend::Dir { path } => {
            // Try to get metadata from tmpfs for dirs under /tmp
            let (u, g, m) = dir_metadata(path);
            (0x4000 | m as u32, u, g, 0, 0)
        }

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utimensat / utimensat_now wrappers in syscall-lib. Why it matters: C programs using musl's utime() / utimensat() interface must reach the kernel through these wrappers; without them touch cannot update timestamps. Focus on `utimensat` and `utime` in `userspace/syscall-lib/src/lib.rs` while you trace the snippet.

/// `utimensat(dirfd, path, times, flags)` — update file timestamps.
/// Sets atime to `atime_sec` and mtime to `mtime_sec` (seconds since epoch).
pub fn utimensat(path: &[u8], atime_sec: i64, mtime_sec: i64) -> isize {
    // struct timespec { tv_sec: i64, tv_nsec: i64 } × 2 = 32 bytes
    let times: [i64; 4] = [atime_sec, 0, mtime_sec, 0];
    unsafe {
        syscall4(
            SYS_UTIMENSAT,
            (-100_i64) as u64, // AT_FDCWD
            path.as_ptr() as u64,
            times.as_ptr() as u64,
            0,
        ) as isize
    }
}

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Evaluate pdpmake source. Why it matters: auditing pdpmake's libc dependencies before attempting to cross-compile prevents wasted iteration if a missing syscall would block the port. Focus on `build_pdpmake` and `stat` in `xtask/src/main.rs` while you trace the snippet.

/// Phase 32: Cross-compile pdpmake (POSIX make) for the OS.
///
/// Strategy: clone pdpmake from GitHub (or use cached clone in target/pdpmake-src/),
/// build with `musl-gcc -static -O2`, and place the resulting binary in
/// kernel/initrd/make.elf.
fn build_pdpmake() {
    let root = workspace_root();
    let initrd = root.join("kernel/initrd");
    let make_elf = initrd.join("make.elf");

    // Check cache.
    if make_elf.exists() && make_elf.metadata().map(|m| m.len() > 0).unwrap_or(false) {
        println!("pdpmake: using cached {}", make_elf.display());
        return;
    }

    // Clone pdpmake source.
    let pdpmake_src = root.join("target/pdpmake-src");
    if !pdpmake_src.join("main.c").exists() {
        println!("pdpmake: cloning from GitHub...");
        let _ = fs::remove_dir_all(&pdpmake_src);
        let status = Command::new("git")
            .args([
                "clone",

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