2.6.7 fbcon: set_con2fb on current console = crash

[Jakub Bogusz]

After upgrade from 2.6.4 to 2.6.7 I noticed that calling set_con2fb
(through FBIOPUT_CON2FBMAP ioctl) on current console (already attached
to fb using this ioctl) causes crash (oops and then recursive oops when
trying to printk on console) and makes console unusable.

That's because take_over_console() calls fbcon_deinit(vc_num)
(which calls fbcon_free_font() on that console display) and then
fbcon_init(vc_num, ...), which copies font data from current fb console.
If current console was just deinit()ed, its fontdata is NULL - and this
pointer is "copied" to the same place, leaving current console with
fontdata==NULL (which leads to oops on nearest putc/putcs).

Attached patch restores 2.6.4 behaviour on set_con2fb (to set font if
it's not set already) - but it's not perfect solution as user font is
still lost (unline on 2.4.x kernels).
Any idea how to preserve user font on set_con2fb() called on current
console?


-- 
Jakub Bogusz    http://cyber.cs.net.pl/~qboosh/
--- linux-2.6.7/drivers/video/console/fbcon.c.orig	2004-06-16 18:24:04.000000000 +0200
+++ linux-2.6.7/drivers/video/console/fbcon.c	2004-06-18 23:12:35.000000000 +0200
@@ -617,6 +617,15 @@
 	if (p->userfont) {
 		REFCOUNT(p->fontdata)++;
 		charcnt = FNTCHARCNT(p->fontdata);
+	} else if(!p->fontdata) {
+		struct font_desc *font = NULL;
+		if (!fontname[0] || !(font = find_font(fontname)))
+			font = get_default_font(info->var.xres,
+						   info->var.yres);
+		vc->vc_font.width = font->width;
+		vc->vc_font.height = font->height;
+		vc->vc_font.data = p->fontdata = font->data;
+		vc->vc_font.charcount = 256; /* FIXME  Need to support more fonts */
 	}
 	con_copy_unimap(vc->vc_num, display_fg);