diff options
| author | H. Peter Anvin <hpa@linux.intel.com> | 2009-03-30 17:38:44 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2009-03-30 17:38:44 -0700 |
| commit | 4f964b57c29db85515b68a3f59a791804aae8aae (patch) | |
| tree | dfd4ad63a74d7b11be71328b7f5fc4b2b80ca472 | |
| parent | 1cb06f94c9c1525975254ed41942098d7a741840 (diff) | |
| download | syslinux-4f964b57c29db85515b68a3f59a791804aae8aae.tar.gz | |
mbr/*.S: if Ctrl is pressed, force the drive number to 0x80
Impact: BIOS bug workaround, possible unexpected consequences?
Escape hatch for BIOSes which pass in garbage in DL: if the Ctrl key
is pressed during boot, force the drive number to 0x80.
Based on a patch by "TJ <ubuntu@tjworld.net>".
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
| -rw-r--r-- | mbr/gptmbr.S | 13 | ||||
| -rw-r--r-- | mbr/isohdpfx.S | 12 | ||||
| -rw-r--r-- | mbr/mbr.S | 12 |
3 files changed, 27 insertions, 10 deletions
diff --git a/mbr/gptmbr.S b/mbr/gptmbr.S index 385afe74..0a547b85 100644 --- a/mbr/gptmbr.S +++ b/mbr/gptmbr.S @@ -1,6 +1,6 @@ /* ----------------------------------------------------------------------- * - * Copyright 2007-2008 H. Peter Anvin - All Rights Reserved + * Copyright 2007-2009 H. Peter Anvin - All Rights Reserved * * Permission is hereby granted, free of charge, to any person * obtaining a copy of this software and associated documentation @@ -61,7 +61,6 @@ _start: movw %sp, %si pushw %es /* 4(%bp) es:di -> $PnP header */ pushw %di /* 2(%bp) */ - pushw %dx /* 0(%bp) = %dl -> drive number */ movw %ax, %es sti cld @@ -72,8 +71,14 @@ _start: rep; movsw ljmpw $0, $next - next: + /* Escape for the user: if Ctrl is pressed, assume drive hd0 */ + testb $0x04, 0x417 /* keyboard control flags: Ctrl pressed */ + jz 1f + movb $0x80, %dl +1: + pushw %dx /* 0(%bp) = %dl -> drive number */ + /* Check to see if we have EBIOS */ pushw %dx /* drive number */ movb $0x41, %ah /* %al == 0 already */ @@ -210,7 +215,7 @@ boot: missing_os: call error - .ascii "Operating system not bootable\r\n" + .ascii "OS not bootable\r\n" saturate_stosl: pushl %eax diff --git a/mbr/isohdpfx.S b/mbr/isohdpfx.S index 9e9d55c3..0e15b11a 100644 --- a/mbr/isohdpfx.S +++ b/mbr/isohdpfx.S @@ -1,6 +1,6 @@ /* ----------------------------------------------------------------------- * - * Copyright 2007-2008 H. Peter Anvin - All Rights Reserved + * Copyright 2007-2009 H. Peter Anvin - All Rights Reserved * * Permission is hereby granted, free of charge, to any person * obtaining a copy of this software and associated documentation @@ -69,7 +69,6 @@ _start: movw %sp, %si pushw %es /* es:di -> $PnP header */ pushw %di - pushw %dx /* dl -> drive number */ movw %ax, %es sti cld @@ -80,8 +79,15 @@ _start: rep; movsw ljmpw $0, $next - next: + + /* Escape for the user: if Ctrl is pressed, assume drive hd0 */ + testb $0x04, 0x417 /* keyboard control flags: Ctrl pressed */ + jz 1f + movb $0x80, %dl +1: + pushw %dx /* dl -> drive number */ + /* Check to see if we have EBIOS */ pushw %dx /* drive number */ movb $0x41, %ah /* %al == 0 already */ @@ -1,6 +1,6 @@ /* ----------------------------------------------------------------------- * - * Copyright 2007-2008 H. Peter Anvin - All Rights Reserved + * Copyright 2007-2009 H. Peter Anvin - All Rights Reserved * * Permission is hereby granted, free of charge, to any person * obtaining a copy of this software and associated documentation @@ -53,7 +53,6 @@ _start: movw %sp, %si pushw %es /* es:di -> $PnP header */ pushw %di - pushw %dx /* dl -> drive number */ movw %ax, %es sti cld @@ -64,8 +63,15 @@ _start: rep; movsw ljmpw $0, $next - next: + + /* Escape for the user: if Ctrl is pressed, assume drive hd0 */ + testb $0x04, 0x417 /* keyboard control flags: Ctrl pressed */ + jz 1f + movb $0x80, %dl +1: + pushw %dx /* dl -> drive number */ + /* Check to see if we have EBIOS */ pushw %dx /* drive number */ movb $0x41, %ah /* %al == 0 already */ |