Implement BlSetConsoleMode() and forcibly set mode to 80x25 to avoid offscreen

xtldr2/console.c

@@ -179,6 +179,23 @@ BlSetConsoleAttributes(IN ULONGLONG Attributes)
     EfiSystemTable->ConOut->SetAttribute(EfiSystemTable->ConOut, Attributes);
 }
 
+/**
+ * Sets the output console device to the requested mode.
+ *
+ * @param Mode
+ *        Supplies a text mode number to set.
+ *
+ * @return This routine returns a status code.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+EFI_STATUS
+BlSetConsoleMode(IN ULONGLONG Mode)
+{
+    return EfiSystemTable->ConOut->SetMode(EfiSystemTable->ConOut, Mode);
+}
+
 /**
  * Sets new coordinates of the console cursor position.
  *
@@ -238,6 +255,14 @@ BlpInitializeConsole()
     EfiSystemTable->ConOut->Reset(EfiSystemTable->ConOut, TRUE);
     EfiSystemTable->StdErr->Reset(EfiSystemTable->StdErr, TRUE);
 
+    /* Make sure that current console mode is 80x25 characters, as some broken EFI implementations might
+     * set different mode that do not fit on the screen, causing a text to be displayed offscreen */
+    if(EfiSystemTable->ConOut->Mode->Mode != 0)
+    {
+        /* Set console mode to 0, which is standard, 80x25 text mode */
+        BlSetConsoleMode(0);
+    }
+
     /* Clear screen and enable cursor */
     BlClearConsoleScreen();
     BlEnableConsoleCursor();