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| author | H. Peter Anvin <hpa@zytor.com> | 2007-10-11 15:01:32 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2007-10-11 15:01:32 -0700 |
| commit | d67eb079d2db06570e7ef299634c9b91cf807b3e (patch) | |
| tree | c2283def2941c4942c042b8bfb4f4e5f165276a0 | |
| parent | 51f53cd1b7d82bf5dc451b2a9d12fe873507699c (diff) | |
| download | syslinux-d67eb079d2db06570e7ef299634c9b91cf807b3e.tar.gz | |
Mark TSS unbusy before protected mode entry
The LTR instruction marks the TSS descriptor busy, and any subsequent
attempt to load it will #GP unless maked unbusy first. Sigh.
| -rw-r--r-- | bcopy32.inc | 3 | ||||
| -rw-r--r-- | com32.inc | 2 |
2 files changed, 5 insertions, 0 deletions
diff --git a/bcopy32.inc b/bcopy32.inc index 7e3ac0f9..330f2be6 100644 --- a/bcopy32.inc +++ b/bcopy32.inc @@ -54,6 +54,7 @@ bcopy_gdt: dw bcopy_gdt_size-1 ; Null descriptor - contains GDT ; TSS segment to keep Intel VT happy. Intel VT is ; unhappy about anything that doesn't smell like a ; full-blown 32-bit OS. +.tss: dw 104-1, DummyTSS ; 30h 32-bit task state segment dd 00008900h ; present, dpl 0, 104 bytes @DummyTSS bcopy_gdt_size: equ $-bcopy_gdt @@ -87,6 +88,8 @@ bcopy: push eax cli call enable_a20 + mov byte [bcopy_gdt.tss+5],89h ; Mark TSS unbusy + mov bx,ss ; Save the stack segment value! o32 lgdt [cs:bcopy_gdt] @@ -82,6 +82,8 @@ com32_enter_pm: call enable_a20 .a20ok: + mov byte [bcopy_gdt.tss+5],89h ; Mark TSS unbusy + lgdt [bcopy_gdt] ; We can use the same GDT just fine lidt [com32_pmidt] ; Set up the IDT mov eax,cr0 |