[PATCH] VGA to fbcon fix.

Currently when going from vgacon to fbcon the VT screenbuffer are often
different sizes.  In the case when they are different sizes a new VT
screenbuffer is allocated and the contents are copied into the new buffer.

Currently the amount copied from VGA text memory to the new screenbuf is
the size of the framebuffer console.  If the framebuffer console new VT
screen buffer is greater than the VGA text memory size then we get some of
the VGA BIOS contents as well.

This patch will only allow you to copy up to the size of VGA text memory
now.  The rest is filled with erase characters.

Initial patch by Jordan Crouse <jordan.crouse@amd.com>
Signed-off-by: James Simmons <jsimmons@www.infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/video/console/vgacon.c

@@ -95,6 +95,7 @@ static unsigned long vgacon_uni_pagedir[2];
 /* Description of the hardware situation */
 static unsigned long	vga_vram_base;		/* Base of video memory */
 static unsigned long	vga_vram_end;		/* End of video memory */
+static int		vga_vram_size;		/* Size of video memory */
 static u16		vga_video_port_reg;	/* Video register select port */
 static u16		vga_video_port_val;	/* Video register value port */
 static unsigned int	vga_video_num_columns;	/* Number of text columns */
@@ -288,6 +289,7 @@ static const char __init *vgacon_startup(void)
 
 	vga_vram_base = VGA_MAP_MEM(vga_vram_base);
 	vga_vram_end = VGA_MAP_MEM(vga_vram_end);
+	vga_vram_size = vga_vram_end - vga_vram_base;
 
 	/*
 	 *      Find out if there is a graphics card present.
@@ -504,9 +506,13 @@ static int vgacon_switch(struct vc_data *c)
 	 */
 	vga_video_num_columns = c->vc_cols;
 	vga_video_num_lines = c->vc_rows;
+
+	/* We can only copy out the size of the video buffer here,
+	 * otherwise we get into VGA BIOS */
+
 	if (!vga_is_gfx)
 		scr_memcpyw((u16 *) c->vc_origin, (u16 *) c->vc_screenbuf,
-			    c->vc_screenbuf_size);
+			    c->vc_screenbuf_size > vga_vram_size ? vga_vram_size : c->vc_screenbuf_size);
 	return 0;		/* Redrawing not needed */
 }
 
@@ -961,7 +967,6 @@ static int vgacon_scrolldelta(struct vc_data *c, int lines)
 	if (!lines)		/* Turn scrollback off */
 		c->vc_visible_origin = c->vc_origin;
 	else {
-		int vram_size = vga_vram_end - vga_vram_base;
 		int margin = c->vc_size_row * 4;
 		int ul, we, p, st;
 
@@ -971,7 +976,7 @@ static int vgacon_scrolldelta(struct vc_data *c, int lines)
 			we = vga_rolled_over + c->vc_size_row;
 		} else {
 			ul = 0;
-			we = vram_size;
+			we = vga_vram_size;
 		}
 		p = (c->vc_visible_origin - vga_vram_base - ul + we) % we +
 		    lines * c->vc_size_row;
@@ -1012,9 +1017,13 @@ static void vgacon_save_screen(struct vc_data *c)
 		c->vc_x = ORIG_X;
 		c->vc_y = ORIG_Y;
 	}
+
+	/* We can't copy in more then the size of the video buffer,
+	 * or we'll be copying in VGA BIOS */
+
 	if (!vga_is_gfx)
 		scr_memcpyw((u16 *) c->vc_screenbuf, (u16 *) c->vc_origin,
-			    c->vc_screenbuf_size);
+			    c->vc_screenbuf_size > vga_vram_size ? vga_vram_size : c->vc_screenbuf_size);
 }
 
 static int vgacon_scroll(struct vc_data *c, int t, int b, int dir,