[Qemu-trivial] [PATCH] SGABIOS: fix wrong video attrs for int 10h, ah==13h

[herbierobinson]

Fix Bug #1670509: wrong video attrs for int 10h, ah==13h
The subroutine set_cursor_position is trashing %bx.
Unfortunately, %bl contains the video attribute for write_string.

The fix saves %bx in the function prolog and restores it in
the epilog.  Also, remove save and restore in set_current_cursor,
because set_cursor_position does it.

Signed-off-by: herbierobinson <address@hidden>
---
 sgabios.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sgabios.S b/sgabios.S
index 275d063..da5acc2 100644
--- a/sgabios.S
+++ b/sgabios.S
@@ -1728,6 +1728,7 @@ write_string_tail:
 
 set_cursor_position:
   pushw %ax
+  pushw %bx
   pushw %ds
   pushw $BDA_SEG
   popw %ds                             /* ds = 0x40 */
@@ -1738,6 +1739,7 @@ set_cursor_position:
   movw %ax, %bx                        /* bx = cursor save offset */
   movw %dx, (%bx)                      /* save new cursor value */
   popw %ds
+  popw %bx
   popw %ax
   ret
 
@@ -1752,12 +1754,10 @@ set_cursor_position:
 
 set_current_cursor:
   pushw %ds
-  pushw %bx
   pushw $BDA_SEG
   popw %ds                             /* ds = 0x40 */
   movb BDA_ACTIVE_PAGE, %bh
   call set_cursor_position
-  popw %bx
   popw %ds
   ret
 
-- 
1.8.3.1