Hi All,
You better ask this as,
What process can not do in ring 0???
Process can do anything, like God.
You can refer Intel's IA-32 architecutre manuals to get more info about this.
Tharindu
On 7/6/06, Gaurav Dhiman <gauravd.chd@xxxxxxxxx> wrote:
On 7/6/06, George Zhim <georgezhim@xxxxxxxxx> wrote:
> HI all,
>
> When a processor is in ring 0 (privilidged mode in x86),
> what can the program now do that it couldn't before ?
>
> which accesses are blocked by the processor if it is in ring 3 ?
> (I know that every interrupt has a minimum cpu priviledge needed,
> but I hardly assume programs are so "eager" to call interrupts, are they ?
> what other things aren't allowed ?)
in ring 0, processor can load IDT, GDT and CR3 registers, which can
chage the view of environment processor is working in.
These are
specific and important registers which should not be altered by any
process. Only in ring 0 mode these these loading instructions are
allowed. Moreover getting an entry through some gates in IDT is also
restriceded in ring 3 (in case of Linux).
Gaurav
>
> where can we see relevant code in the kernel ?
>
> thanks
> George
>
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