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| author | H. Peter Anvin <hpa@zytor.com> | 2010-08-11 10:42:51 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2010-08-11 10:42:51 -0700 |
| commit | 5b1f5189081f677e4a578e2a6d52c60a7c082e1d (patch) | |
| tree | acf19d265b290c8b07268700cef25e6a0113367e /core | |
| parent | 17cdc1e604dbed3c7a5aefc37a3fb303c539225e (diff) | |
| download | syslinux-5b1f5189081f677e4a578e2a6d52c60a7c082e1d.tar.gz | |
core: look for invalid MBR handover information address
The Win7 MBR doesn't provide proper handover information. Instead, it
leaves DS:SI = 0:0x7e00, so reject that information as invalid on
grounds that it is pointed into the bootloader area.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'core')
| -rw-r--r-- | core/diskstart.inc | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/core/diskstart.inc b/core/diskstart.inc index c0ba52a0..c0301d4b 100644 --- a/core/diskstart.inc +++ b/core/diskstart.inc @@ -31,9 +31,10 @@ PartInfo equ StackBuf .gpt equ PartInfo+20 FloppyTable equ PartInfo+76 ; Total size of PartInfo + FloppyTable == 76+16 = 92 bytes -Hidden equ StackBuf-20 ; Partition offset -OrigFDCTabPtr equ StackBuf-12 ; The 2nd high dword on the stack -OrigESDI equ StackBuf-8 ; The high dword on the stack +Hidden equ StackBuf-24 ; Partition offset (qword) +OrigFDCTabPtr equ StackBuf-16 ; Original FDC table +OrigDSSI equ StackBuf-12 ; DS:SI -> partinfo +OrigESDI equ StackBuf-8 ; ES:DI -> $PnP structure DriveNumber equ StackBuf-4 ; Drive number StackHome equ Hidden ; The start of the canonical stack @@ -116,6 +117,8 @@ start: push dx ; Save drive number (in DL) push es ; Save initial ES:DI -> $PnP pointer push di + push ds ; Save original DS:SI -> partinfo + push si mov es,cx ; @@ -174,6 +177,12 @@ floppy: ; Note: di points to beyond the end of PartInfo ; harddisk: + mov dx,[di-76-10] ; Original DS + mov si,[di-76-12] ; Original SI + shr si,4 + add dx,si + cmp dx,PartInfo >> 4 + jae .no_partition test byte [di-76],7Fh ; Sanity check: "active flag" should jnz .no_partition ; be 00 or 80 cmp [di-76+4],cl ; Sanity check: partition type != 0 |