loader: loader can pick too large font

While calculating font size based on EDID data, we can end up
selecting too large font and too small terminal. Add check to
prevent it.

Tested by:	bz, ziaee
Reviewed by:	adrian
Differential Revision:	https://reviews.freebsd.org/D50258

stand/common/gfx_fb.c

@@ -2054,7 +2054,8 @@ gfx_get_ppi(void)
  * not smaller than calculated size value.
  */
 static vt_font_bitmap_data_t *
-gfx_get_font(void)
+gfx_get_font(teken_unit_t rows, teken_unit_t cols, teken_unit_t height,
+    teken_unit_t width)
 {
 	unsigned ppi, size;
 	vt_font_bitmap_data_t *font = NULL;
@@ -2077,6 +2078,14 @@ gfx_get_font(void)
 	size = roundup(size * 2, 10) / 10;
 
 	STAILQ_FOREACH(fl, &fonts, font_next) {
+		/*
+		 * Skip too large fonts.
+		 */
+		font = fl->font_data;
+		if (height / font->vfbd_height < rows &&
+		    width / font->vfbd_width < cols)
+			continue;
+
 		next = STAILQ_NEXT(fl, font_next);
 
 		/*
@@ -2084,7 +2093,6 @@ gfx_get_font(void)
 		 * we have our font. Make sure, it actually is loaded.
 		 */
 		if (next == NULL || next->font_data->vfbd_height < size) {
-			font = fl->font_data;
 			if (font->vfbd_font == NULL ||
 			    fl->font_flags == FONT_RELOAD) {
 				if (fl->font_load != NULL &&
@@ -2093,6 +2101,7 @@ gfx_get_font(void)
 			}
 			break;
 		}
+		font = NULL;
 	}
 
 	return (font);
@@ -2123,7 +2132,7 @@ set_font(teken_unit_t *rows, teken_unit_t *cols, teken_unit_t h, teken_unit_t w)
 	}
 
 	if (font == NULL)
-		font = gfx_get_font();
+		font = gfx_get_font(*rows, *cols, h, w);
 
 	if (font != NULL) {
 		*rows = height / font->vfbd_height;