[syslinux] [PATCH 1/3] v2: mbr: Ctrl-key press forces load from first hard disk
TJ
ubuntu at tjworld.net
Mon Mar 30 14:32:02 PDT 2009
---
mbr/mbr.S | 10 ++++++++++
1 files changed, 10 insertions(+), 0 deletions(-)
diff --git a/mbr/mbr.S b/mbr/mbr.S
index 722d90d..e8be09e 100644
--- a/mbr/mbr.S
+++ b/mbr/mbr.S
@@ -51,6 +51,7 @@ _start:
movw %ax, %ss
movw $stack, %sp
movw %sp, %si
+ movw %sp, %bp /* needed later if drive number is to be forced due to Ctrl key being pressed */
pushw %es /* es:di -> $PnP header */
pushw %di
pushw %dx /* dl -> drive number */
@@ -66,6 +67,15 @@ _start:
ljmpw $0, $next
next:
+ /* Provide a way for the user to force boot from first hard-disk by pressing a Ctrl key */
+get_shift_keys: /* Provide a way for the user to force CHS addressing mode by pressing either Shift key */
+ testb $0x04, 0x0417 /* I/O memory-mapped keyboard shift flags: control key pressed? */
+ jz detect_bios_type
+force_first_hard_disk:
+ movb $0x80, -6(%bp) /* offset from top-of-stack to drive number; force it to be first hard disk */
+ movb $0x80, %dl /* change the drive number about to be used in detect_bios_type */
+
+detect_bios_type:
/* Check to see if we have EBIOS */
pushw %dx /* drive number */
movb $0x41, %ah /* %al == 0 already */
--
1.6.0.4
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