Re: [PATCH v4 17/26] x86/boot: Reduce size of the DOS stub

[Evgeniy Baskov]

On 2023-03-10 17:59, Ard Biesheuvel wrote:
> On Thu, 15 Dec 2022 at 13:40, Evgeniy Baskov <baskov@xxxxxxxxx> wrote:
> > This is required to fit more sections in PE section tables,
> > since its size is restricted by zero page located at specific offset
> > after the PE header.
> >
> > Tested-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > Tested-by: Peter Jones <pjones@xxxxxxxxxx>
> > Signed-off-by: Evgeniy Baskov <baskov@xxxxxxxxx>
>
> I'd prefer to rip this out altogether.
>
> https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/commit/?id=9510f6f04f579b9a3f54ad762c75ab2d905e37d8

Sounds great! Can I replace this patch with yours in v5?

> (and refer to the other thread in linux-efi@)

Which thread exactly? The one about the removal of
real-mode code?

> > ---
> >  arch/x86/boot/header.S | 14 ++++++--------
> >  1 file changed, 6 insertions(+), 8 deletions(-)
> >
> > diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
> > index 9338c68e7413..9fec80bc504b 100644
> > --- a/arch/x86/boot/header.S
> > +++ b/arch/x86/boot/header.S
> > @@ -59,17 +59,16 @@ start2:
> >         cld
> >
> >         movw    $bugger_off_msg, %si
> > +       movw    $bugger_off_msg_size, %cx
> >
> >  msg_loop:
> >         lodsb
> > -       andb    %al, %al
> > -       jz      bs_die
> >         movb    $0xe, %ah
> >         movw    $7, %bx
> >         int     $0x10
> > -       jmp     msg_loop
> > +       decw    %cx
> > +       jnz     msg_loop
> >
> > -bs_die:
> >         # Allow the user to press a key, then reboot
> >         xorw    %ax, %ax
> >         int     $0x16
> > @@ -90,10 +89,9 @@ bs_die:
> >
> >         .section ".bsdata", "a"
> >  bugger_off_msg:
> > -       .ascii  "Use a boot loader.\r\n"
> > -       .ascii  "\n"
> > -       .ascii  "Remove disk and press any key to reboot...\r\n"
> > -       .byte   0
> > +       .ascii  "Use a boot loader. "
> > +       .ascii  "Press a key to reboot"
> > +       .set    bugger_off_msg_size, . - bugger_off_msg
> >
> >  #ifdef CONFIG_EFI_STUB
> >  pe_header:
> > --
> > 2.37.4