[PATCH] Reduce boot header size with 1 byte

From: xyproto
Date: Thu Sep 27 2018 - 09:41:28 EST


From: Alexander F. RÃdseth <xyproto@xxxxxxxxxxxxx>

Only ah needs to be set to 0 before calling interrupt 0x16 for waiting
for a keypress.

This patch changes the line that uses xor so that it only zeroes "ah" instead of "ax".
This saves a byte.

Signed-off-by: Alexander F. RÃdseth <xyproto@xxxxxxxxxxxxx>
---
arch/x86/boot/header.S | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 850b8762e889..905cb96f43d4 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -71,14 +71,15 @@ msg_loop:
jmp msg_loop

bs_die:
- # Allow the user to press a key, then reboot
- xorw %ax, %ax
+ # Allow the user to press a key
+ xorb %ah, %ah
int $0x16
+
+ # Boostrap by reading sector 1, head 0, track 0 from drive
int $0x19

- # int 0x19 should never return. In case it does anyway,
- # invoke the BIOS reset code...
- ljmp $0xf000,$0xfff0
+ # If boostrap somehow did not work, invoke the BIOS reset code
+ ljmp $0xf000, $0xfff0

#ifdef CONFIG_EFI_STUB
.org 0x3c
--
2.19.0