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authorShao Miller <shao.miller@yrdsb.edu.on.ca>2010-06-11 04:15:19 +0000
committerH. Peter Anvin <hpa@linux.intel.com>2010-06-17 11:44:37 -0700
commitaa1050f66db73be1f61eea0c2df8169430d32d8e (patch)
treecb97ed92bcc58fb004590ab81fcdc6f3577d0e27
parentab4a10a3b558f835486efc5dd9e4eeb47a863eb7 (diff)
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eltorito: Scan upwards instead of downwards
A developer for GRUB4DOS called tinybit has reported that some BIOSes crash when the DOS ElTorito.Sys driver scans drive number 0xFF. According to the El Torito specification, drive 0x7F means "terminate all," so a plausible explanation suggested by H. Peter Anvin is that the drive 0xFF is a shadow of drive 0x7F, thus contributing to a failure on these BIOSes. Now we scan from 0x80 through 0xFF, instead. [ hpa: dropped checkin of eltorito.sys ] Signed-off-by: Shao Miller <shao.miller@yrdsb.edu.on.ca> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
-rw-r--r--dosutil/eltorito.asm8
1 files changed, 4 insertions, 4 deletions
diff --git a/dosutil/eltorito.asm b/dosutil/eltorito.asm
index eabda126..96cfd9ba 100644
--- a/dosutil/eltorito.asm
+++ b/dosutil/eltorito.asm
@@ -1029,7 +1029,7 @@ SpecGo: mov si,SpecPkt
ScanDrives: push ax ; at df3 in 1.4
push si
- mov dl, 0ffh ;Start at Drive 0xff
+ mov dl, 80h ;Start at Drive 0x80
NextDrv: mov ax,4B01h ;Get Bootable CD-ROM Status
mov BYTE [SpecPkt],0 ;Clear 1st byte of SpecPkt
call SpecGo
@@ -1044,9 +1044,9 @@ NextDrv: mov ax,4B01h ;Get Bootable CD-ROM Status
ja FindFail ; in 1.4 at e16
jmp short SendFound ; in 1.4 at e26
-FindFail: dec dl ;Next drive
- cmp dl, 80h
- jb SendFail ; Check from ffh..80h
+FindFail: inc dl ;Next drive
+ cmp dl, 0ffh
+ jb SendFail ; Check from 80h..ffh
jmp short NextDrv
SendFail: xor dl,dl
stc