fix: stacks at top of user VA in own 1 MiB band (guard, heap kept below), 8/16 pages default; kernel fault msg names pid, kind, flags stack overflow; flaky OVERFLOW + spawntest/test-qemu check it

scripts/test-qemu.sh

@@ -57,6 +57,11 @@ echo "test-qemu: second boot: wrong passcode refused, right one signs in, sealed
 rm -f "${KEYS}" "${MON}"
 
 grep -a "smptest:\|spawntest:\|Hello\|SMPTEST" "${LOG}"
+# The kernel names a stack overflow (flaky's, asked for) as one.
+overflow_ok=1
+if ! grep -aq "(stack overflow" "${LOG}"; then
+    echo "test-qemu: a stack overflow was not reported as one"; overflow_ok=0
+fi
 # What k-os wrote must be ext4 that the real tools accept.
 disk_ok=1
 if command -v e2fsck >/dev/null && command -v debugfs >/dev/null; then
@@ -81,7 +86,7 @@ if command -v e2fsck >/dev/null && command -v debugfs >/dev/null; then
     fi
     rm -f "${LOG}.fsck"
 fi
-if [ "${disk_ok}" -eq 1 ] && [ ${first_ok} -eq 1 ] && [ ${second_ok} -eq 1 ] && grep -aq "SMPTEST PASS" "${LOG}"; then
+if [ "${disk_ok}" -eq 1 ] && [ ${overflow_ok} -eq 1 ] && [ ${first_ok} -eq 1 ] && [ ${second_ok} -eq 1 ] && grep -aq "SMPTEST PASS" "${LOG}"; then
     echo "test-qemu: pass (${SMP} harts)"
     rm -f "${LOG}"
     exit 0