Demand paging, the RTL8168H, links that come up late, and Ctrl+Alt+F1..F12

- Anonymous memory can be reserved without being backed: large mappings,
  MAP_NORESERVE and PROT_NONE are recorded and each page appears, zeroed,
  on first touch -- from trap() for the program, from uva2ka() for the
  kernel on its behalf. WebKit reserves 4 GB at start and touches a sliver;
  backing it all failed with ENOMEM and Epiphany aborted.
- r8169: the 8168G generation and later (the laptop's 8168H, XID 541) are
  taken from the firmware's out-of-band mode, get their PLL powered, the
  receive gate opened, and their PHY reached through the OCP window. The
  PHY's power-down bit is cleared; the old code kept it while restarting
  autonegotiation. Untested on the hardware so far.
- The network thread follows each device's link into lwIP. The link was
  read once at attach, 0.02 s into boot; real autonegotiation takes
  seconds, so on hardware the interface stayed down for good.
- Twelve terminals, switched with Ctrl+Alt+F1..F12 by default: the keys X
  uses, so the console and the desktop agree. AltGr+F-key is gone from
  the defaults (chvt -c altgr+F brings it back).
- SO_PASSCRED on Unix sockets, with SCM_CREDENTIALS delivered by recvmsg.
  WebKit sets it on its IPC sockets and aborted when refused.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4

kernel/drivers/usb/hid/usb_hid.c

@@ -164,9 +164,10 @@ usb_kbd_getc(void)
 static int
 hid_special(uchar usage, uchar mods)
 {
-  // F1..F6 with Alt, AltGr or Ctrl+Alt: switch terminals, as on Linux.
+  // F1..F12 with left Alt or Ctrl+Alt: switch terminals, as on Linux and as
+  // the PS/2 path does. AltGr alone is a layout's third level, not this.
   if (usage >= 0x3A && usage < 0x3A + NVT && (mods & HID_MOD_ALT) &&
-      !(mods & HID_MOD_SHIFT))
+      !(mods & HID_MOD_SHIFT) && ((mods & 0x04) || (mods & HID_MOD_CTRL)))
     return KBD_VT_SWITCH + (usage - 0x3A);
   if (usage >= 0x3A && usage <= 0x45)
     return KBD_F1 + (usage - 0x3A);