base: fix round-8 deferred stubs in initfs, randd, ptyd

initfs/tools: buffer inode table writes in memory and flush with a
  single write_all_at instead of one syscall per inode header.

randd: build a proper entropy pool using SHA-256 that mixes hardware RNG
  (RDRAND/RNDRRS) with timing-derived entropy. The pool is re-seeded
  every 4096 reads and on every write. User-supplied entropy from writes
  is added to the pool rather than directly replacing the PRNG state.

ptyd: VLNEXT now properly quotes the next input byte — sets a flag that
  causes the next byte to bypass all control-character processing and be
  pushed directly to the line buffer. VDISCARD now flushes the cooked
  input buffer instead of being a silent no-op.

ptyd/src/pty.rs

@@ -14,6 +14,7 @@ pub struct Pty {
     pub mosi: VecDeque<Vec<u8>>,
     pub timeout_count: u64,
     pub timeout_character: Option<u64>,
+    pub lnext: bool,
 }
 
 impl Pty {
@@ -28,6 +29,7 @@ impl Pty {
             mosi: VecDeque::new(),
             timeout_count: 0,
             timeout_character: None,
+            lnext: false,
         }
     }
 
@@ -65,6 +67,18 @@ impl Pty {
         for &byte in buf.iter() {
             let mut b = byte;
 
+            if self.lnext {
+                self.lnext = false;
+                if b != 0 {
+                    if echo {
+                        self.output(&[b]);
+                    }
+                    self.timeout_character = Some(self.timeout_count);
+                    self.cooked.push(b);
+                }
+                continue;
+            }
+
             // Input translation
             if b == b'\n' {
                 if inlcr {
@@ -220,16 +234,15 @@ impl Pty {
             }
 
             if is_cc(b, VLNEXT) && iexten {
-                // VLNEXT quotes the next input byte so control characters
-                // can be entered literally. Real implementation requires
-                // reading the next byte outside of the current for loop;
-                // for now it is acknowledged but does not consume the
-                // following byte. Cross-referenced with POSIX termios(3).
+                self.lnext = true;
+                if echoe {
+                    self.output(&[b]);
+                }
                 b = 0;
             }
 
             if is_cc(b, VDISCARD) && iexten {
-                // Toggle output flushing; not fully implemented in this PTY.
+                self.cooked.clear();
                 b = 0;
             }