bug pass: whole console lines, a quiet SCI, an honest reserve warning

- schinit, schinitd and vgpud build every message from pieces, one
  write() each, so a job starting on another CPU landed mid-line:
  "schinitd: starting vgpud: os.schos.resolvconfno virtio-gpu on this
  machine". They now collect a line and write it at the newline;
  resolvconf's verbose line is one write with its prefix.
- The ACPI SCI registers IRQ_QUIET. A desktop's SCI never fires, and the
  poller took two seconds of silence for a misrouted line ("irq 9:
  nothing has arrived on it") and called the handler every tick. A line
  is only exempt while every handler on it is quiet.
- The loader claims each segment from where the last one's claim ended,
  so two segments sharing a page no longer ask for it twice. When a
  claim is still refused, it names the memory-map entries in the way.
- Stale divesymlink() declaration gone; the kernel.md struct table
  re-measured (inode, buf and file pools grow from slabs now).

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

cmd/schinitd/main.c

@@ -83,10 +83,40 @@ ends_with(const char *s, const char *suffix)
     return seq(s + ls - lf, suffix);
 }
 
+// Whole lines, in one write() each.
+//
+// Every message here is assembled from pieces -- a prefix, a job's label, a
+// number -- and each piece used to be its own write(). The console keeps one
+// write() together, but nothing keeps two of them together, so a job starting
+// on another CPU landed in the middle of the line: "schinitd: starting vgpud:
+// os.schos.resolvconfno virtio-gpu on this machine" was this process and
+// vgpud taking turns a word at a time. The pieces now collect here and go out
+// at the newline.
+static char lbuf[512];
+static int  lbn;
+
+static void
+lflush(void)
+{
+    if (lbn)
+        write(1, lbuf, lbn);
+    lbn = 0;
+}
+
+static void
+emit(const char *s, int n)
+{
+    for (int i = 0; i < n; i++) {
+        lbuf[lbn++] = s[i];
+        if (s[i] == '\n' || lbn == (int)sizeof lbuf)
+            lflush();
+    }
+}
+
 static void
 out(const char *s)
 {
-    write(1, (void *)s, slen(s));
+    emit(s, slen(s));
 }
 
 // How the machine was booted, read once.
@@ -139,7 +169,7 @@ static void
 vout(const char *s)
 {
     if (verbose_boot)
-        write(1, (void *)s, slen(s));
+        emit(s, slen(s));
 }
 
 static void
@@ -626,14 +656,17 @@ main(void)
     h.reserved = 0;
     if (write(sock, &h, sizeof(h)) != sizeof(h)) {
         out("schinitd: no channel to pid 1\n");
+        lflush();
         exit();
     }
     if (read(sock, &h, sizeof(h)) != sizeof(h) || h.op != SCHINIT_WELCOME) {
         out("schinitd: pid 1 did not answer\n");
+        lflush();
         exit();
     }
     if (h.proto != SCHINIT_PROTO) {
         out("schinitd: protocol mismatch with pid 1\n");
+        lflush();
         exit();
     }
 
@@ -742,7 +775,8 @@ main(void)
         // pinging -- which it has, because it is no longer talking to us.
         if (pr > 0 && (pf.revents & (POLLHUP | POLLERR | POLLNVAL))) {
             out("schinitd: channel closed; this supervisor has been replaced\n");
-            exit();
+            lflush();
+        exit();
         }
 
         if (pr > 0 && (pf.revents & POLLIN)) {
@@ -752,7 +786,8 @@ main(void)
                 // PID 1 closed the channel. It is the one process that cannot
                 // have gone away, so this means we are being replaced.
                 out("schinitd: channel closed\n");
-                exit();
+                lflush();
+        exit();
             }
             if (m.op == SCHINIT_PING) {
                 struct schinit_hello p;