Changing Privilege Level

[pini]

I tried this :

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call USER_SEL:FUNC

in the kernel code (ring 0) to switch to a CPL 3 function FUNC, but I get this :

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call_protected: cs.rpl > CPL

How can I do to switch between CPLs ??

[pini]

Anyway, I found it : I can make a far call to go to a less CPL and make a return to go to a greater CPL

[pini]

Well, I have some problems to make it work...
I have to use a far return to switch from CPL 0 to CPL 3, so I'm using this code :

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push ss
push esp
push cs
push eip
retf

DS, ES, FS and GS are set to zero by the retf, because of the privilege switching, so I put this before my pushs :

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mov ax,USER_DATA_SELECTOR ; GDT Data CPL 3 entry
mov ds,ax
mov es,ax
mov fs,ax
mov gs,ax

But I get this with bochs :

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exception(): 3rd exception with no resolution

I guess I forgot something, but I can't figure out what...