Just to add more, CPL is used to protect the kernel memory from user land programs. e.g. kernel space memory is marked as accessible when CPL=0 thus while running in user mode (CPL=3) you cannot access kernel memory (address space).
There are other CPL i.e. 1, 2, which are less privileged then 0 but Linux uses only 0 and 3.
Thanks!
On Tue, Jan 6, 2009 at 8:29 AM, Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx> wrote:
Hi
On Tue, Jan 6, 2009 at 2:26 PM, battipatisainagendra Bhavaniprasad
<sainagendrabhavaniprasad@xxxxxxxxx> wrote:
> Hi Mr.Mulyadi Santosh,
> Thank you your your reply.I could not understand
> point No.2.Can you give me some tutorial on what is CPL...e.t.c.
>
> Please reply.
pls check Intel CPU documentation. For a brief explanation, CPL stands
for Current Privilege Level. It denotes the privilege the processor is
currently operating on. CPL=3 means user mode, while CPL=0 means
kernel mode.
regards,
Mulyadi.
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