[bzimage] Update setup_move_size only for protocol versions 2.00 and 2.01

The setup_move_size field is not defined in protocol versions earlier
than 2.00 (and is obsolete in versions later than 2.01).  In binaries
using versions earlier than 2.00, the relevant location is likely to
contain executable code.

Interestingly, this bug has been present since support for pre-2.00
protocol versions was added in 2009, and has been unexpectedly
modifying the memtest86+ code fragment:

	mov	$0x92, %dx
	inb	%dx, %al

Fortuitously, the modification exactly overwrote the value loaded into
%dx, and so the net effect was limited to causing Fast Gate A20
detection to always fail.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/arch/i386/image/bzimage.c b/src/arch/i386/image/bzimage.c
index cc7aecab44ce98601c31227a5c5a51ed969ea1ec..08eb4d34eaf51b5abda9fe9b09c2998d3a8badf1 100644 (file)
--- a/src/arch/i386/image/bzimage.c
+++ b/src/arch/i386/image/bzimage.c
@@ -214,7 +214,8 @@ static void bzimage_update_header ( struct image *image,
        } else {
                bzimg->cmdline_magic.magic = BZI_CMDLINE_MAGIC;
                bzimg->cmdline_magic.offset = bzimg->rm_cmdline;
-               bzimg->bzhdr.setup_move_size = bzimg->rm_memsz;
+               if ( bzimg->version >= 0x0200 )
+                       bzimg->bzhdr.setup_move_size = bzimg->rm_memsz;
        }
 
        /* Set video mode */