Job control, function keys, and real sleeps

- SIGSTOP/SIGTSTP/SIGTTIN/SIGTTOU stop, SIGCONT resumes; the parent gets
  SIGCHLD and wait4 reports WUNTRACED/WCONTINUED; ps shows T. Ctrl-Z works,
  and mc no longer hangs waiting for its subshell to stop.
- Blocking reads (console, pty, pipe) and sleeps take a pending stop and
  carry on after SIGCONT; a caught signal without SA_RESTART ends them
  with EINTR.
- nanosleep reads tv_nsec (sleep 0.5 used to return at once), writes the
  remainder, and clock_nanosleep understands TIMER_ABSTIME.
- rt_sigaction uses the k_sigaction layout for Linux-ABI processes: the old
  action's restorer was written 112 bytes past the caller's struct. Flags
  are kept; SIGKILL and SIGSTOP cannot be caught.
- F1..F12 reach programs, as the Linux console sends them (PS/2, USB, I2C).
- TIOCLINUX subcode 6 answers "no modifiers" instead of echoing the 6 back.

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

kernel/dev/keymap.c

@@ -24,6 +24,12 @@
   [0xCB] = KBD_LF,    [0xCD] = KBD_RT,               \
   [0x97] = KBD_HOME,  [0xCF] = KBD_END,              \
   [0xD2] = KBD_INS,   [0xD3] = KBD_DEL,              \
+  [0x3B] = KBD_F1,     [0x3C] = KBD_F1 + 1,          \
+  [0x3D] = KBD_F1 + 2, [0x3E] = KBD_F1 + 3,          \
+  [0x3F] = KBD_F1 + 4, [0x40] = KBD_F1 + 5,          \
+  [0x41] = KBD_F1 + 6, [0x42] = KBD_F1 + 7,          \
+  [0x43] = KBD_F1 + 8, [0x44] = KBD_F1 + 9,          \
+  [0x57] = KBD_F1 + 10, [0x58] = KBD_F12,            \
   [0x9C] = '\n',      /* KP_Enter */                 \
   [0xB5] = '/'        /* KP_Div   */
 

kernel/dev/pty.c

@@ -458,6 +458,16 @@ pts_read(struct inode *ip, uint64 off, char *dst, int n)
         ilock(ip);
         return got ? got : -EINTR;
       }
+      if (sig_attention(myproc())) {
+        release(&ptylock);
+        int e = sig_blocking_check();
+        if (e) {
+          ilock(ip);
+          return got ? got : e;
+        }
+        acquire(&ptylock);
+        continue;
+      }
       sleep(&p->ir, &ptylock);
     }
     c = p->in[p->ir++ % PTY_BUF];