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| author | H. Peter Anvin <hpa@zytor.com> | 2009-05-26 20:29:31 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2009-05-26 20:29:31 -0700 |
| commit | f92916d7e556cdf4894333b515f4ce24ca9951ea (patch) | |
| tree | 08b4d785a46805dc3f7d33c75083c41c349d93cb /core/isolinux.asm | |
| parent | b8c15b400ad50af55678defe7c488262f21ac5fc (diff) | |
| download | syslinux-f92916d7e556cdf4894333b515f4ce24ca9951ea.tar.gz | |
isohybrid: make isolinux.bin and isohybrid two-way compatiblesyslinux-3.81-pre16syslinux-3.81
It turns out we *can* determine if we have the extra partition offset
information after all, by looking at the value of the stack pointer.
This depends on the internals of the old isohdpfx code, but that's
really all we need to worry about.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'core/isolinux.asm')
| -rw-r--r-- | core/isolinux.asm | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/core/isolinux.asm b/core/isolinux.asm index 104de14a..090999d2 100644 --- a/core/isolinux.asm +++ b/core/isolinux.asm @@ -108,14 +108,12 @@ GetlinsecPtr resw 1 ; The sector-read pointer BIOSName resw 1 ; Display string for BIOS type %define HAVE_BIOSNAME 1 BIOSType resw 1 +bsSecPerTrack resw 1 ; Used in hybrid mode +bsHeads resw 1 ; Used in hybrid mode DiskError resb 1 ; Error code for disk I/O DriveNumber resb 1 ; CD-ROM BIOS drive number ISOFlags resb 1 ; Flags for ISO directory search RetryCount resb 1 ; Used for disk access retries - alignb 8 -bsHidden resq 1 ; Used in hybrid mode -bsSecPerTrack resw 1 ; Used in hybrid mode -bsHeads resw 1 ; Used in hybrid mode _spec_start equ $ @@ -233,6 +231,9 @@ bi_end: ; - EBIOS flag ; (top of stack) ; + ; If we had an old isohybrid, the partition offset will + ; be missing; we can check for that with sp >= 0x7c00. + ; Serious hack alert. %ifndef DEBUG_MESSAGES _hybrid_signature: dd 0x7078c0fb ; An arbitrary number... @@ -244,8 +245,11 @@ _start_hybrid: pop dx pop di pop es + cmp sp,7C00h + jae .nooffset pop dword [cs:bsHidden] pop dword [cs:bsHidden+4] +.nooffset: mov si,bios_cbios jcxz _start_common @@ -1056,7 +1060,9 @@ bios_cbios_str db 'CHDD', 0 bios_ebios_str db 'EHDD' ,0 %endif - alignz 4 + alignz 8 +bsHidden dq 0 ; Used in hybrid mode + bios_cdrom: dw getlinsec_cdrom, bios_cdrom_str %ifndef DEBUG_MESSAGES bios_cbios: dw getlinsec_cbios, bios_cbios_str |