Hello,
I am writing small code that boots, jumps to 32bit protected mode (no-paging enabled) --> 64bit mode (pml4 paging) --> perform some 64bit test --> jump back to 32bit protected mode (no-paging enabled).
I got successful getting into 64bit mode and I'm trying to switch out of it to 32bit protected mode.
According to Intel document the first step is to "Switch to compatibility mode" which after several efforts, I'm not able to do successfully. Although I was successful in jumping in and out of compatibility mode from 32bit protected mode (no-paging enabled).
Only diff. betwn 64bit page-protected mode and compatibility mode is L and D bit in code segment. In other words, (according to my understanding) if I'm in 64bit mode and if I want to jump to compatibility mode, all I'm suppose to do is to make far jump to compatibility mode Code-Segment (please correct me if I'm wrong). The CPU freezes when I make the jump.
While making jump,
1) PML4 paging is still in place (hence, IA32_EFER.LMA = 1)
2) PAE and PE is still enabled
3) IA32_EFER.LME = 1
Can somebody please help me with this? Am I suppose to re-arrange paging or do something about gdt?
Thanks,
/tejas
NOTE: When I jump back to 32bit protected mode, I want to keep paging disabled.
