On 07/03/2017 02:30, herbierobinson wrote: > 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 <herbie.robin...@stratus.com> > --- > 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
Well, we are trashing %bh here, I think the push/pop %bx is needed. [comment says "all registers preserved except flags"] > call set_cursor_position > - popw %bx > popw %ds > ret > >
