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 -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
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