1 files changed, 20 insertions, 0 deletions

diff --git a/rsnix/src/vt.rs b/rsnix/src/vt.rs
index 53821b7..4578f6c 100644
--- a/rsnix/src/vt.rs
+++ b/rsnix/src/vt.rs
@@ -96,6 +96,26 @@ static mut CUR: usize = 0;
 /// Allocate the cell grid.  Call once after `gop::init()`.
 pub fn init() {
     let (cols, rows) = gop::dims();
+    if rows == 0 || cols == 0 {
+        // No usable framebuffer geometry: GOP is missing entirely or the
+        // active mode reports 0x0.  Without a display there is nothing
+        // the shell can do, so stop with a visible explanation instead
+        // of building an empty grid and panicking at the first cell
+        // write (a blank screen on real hardware, which has no serial
+        // console).
+        let lines = [
+            "FATAL: no framebuffer geometry",
+            "GOP missing or active mode is 0x0",
+            "see the 'gop:' boot marker / serial log",
+        ];
+        crate::gop::dump_lines(&lines);
+        crate::serial_println!("FATAL: no framebuffer geometry (GOP missing or 0x0 mode)");
+        loop {
+            unsafe {
+                core::arch::asm!("cli; hlt");
+            }
+        }
+    }
     unsafe {
         ROWS = rows;
         COLS = cols;