1 files changed, 13 insertions, 0 deletions

diff --git a/shell/src/lib.rs b/shell/src/lib.rs
index e1d54c8..3090776 100644
--- a/shell/src/lib.rs
+++ b/shell/src/lib.rs
@@ -721,6 +721,7 @@ write `{} <path> TIL <marker>`",
         "sleep" => cmd_sleep(&parsed),
         "kill" => cmd_kill(&parsed),
         "demo" => cmd_demo(&parsed),
+        "fault" => cmd_fault(),
         _ => term_err(&alloc::format!("unknown command: {}", cmd)),
     }
 }
@@ -806,6 +807,18 @@ fn cmd_hello(p: &Parsed) {
     pipe.end();
 }
 
+/// Deliberately fault on an unmapped address — test hook that verifies
+/// the fault-dump path (screen + serial) halts cleanly instead of
+/// triple-faulting.  The system stops; the log must show the dump.
+/// Canonical-but-unmapped address (below 2^47, above any RAM/MMIO): the
+/// page walk terminates at a not-present entry → #PF with CR2 = address.
+fn cmd_fault() {
+    term_println("fault: writing to 0x0000_4000_0000_0000...");
+    unsafe {
+        core::ptr::write_volatile(0x0000_4000_0000_0000usize as *mut u32, 0x1234u32);
+    }
+}
+
 fn cmd_clear() {
     rsnix::gop::clear_screen();
 }