kernel: timers that fire, raw ping, and the sockets X needs

alarm() and setitimer() stored a countdown nothing counted down, so no
timer has ever fired; setitimer and getitimer were also registered with
no Linux number. alarmd now posts SIGALRM on the tick, while any process
has a timer armed. busybox's ping, /bin/ping on the Alpine root, sends
every request after the first from its SIGALRM handler.

It also opens SOCK_RAW, which was EPROTOTYPE. A raw ICMP socket is now a
ping socket whose reads start at the IP header. And a blocked socket
call gives up for a signal with a handler, not only for a kill: the
alarm woke recvfrom, and the wait put it straight back to sleep.

For Xorg: AF_UNIX abstract names, which read as the empty path and so as
EADDRINUSE ("server already running"); and getsockname and getpeername,
which did not exist, so libxcb sent no cookie and the server refused
every client.

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

kernel/sys/table.inc

@@ -184,8 +184,8 @@ SYSCALL(102,        157, prctl)
 SYSCALL(103,        234, tgkill)
 SYSCALL(104,        200, tkill)
 SYSCALL(105,         34, pause)
-SYSCALL(106,   NO_LINUX, getitimer)
-SYSCALL(107,   NO_LINUX, setitimer)
+SYSCALL(106,         36, getitimer)
+SYSCALL(107,         38, setitimer)
 SYSCALL(108,         98, getrusage)
 SYSCALL(109,        100, times)
 SYSCALL(110,         99, sysinfo)
@@ -296,6 +296,8 @@ SYSCALL(203,        281, epoll_pwait)
 SYSCALL(204,        282, signalfd)
 SYSCALL(205,        284, eventfd)
 SYSCALL(206,         73, flock)
+SYSCALL(207,         51, getsockname)
+SYSCALL(208,         52, getpeername)
 
 // --- mounts ---
 SYSCALL(185,        165, mount)