[cs631apue] Question on user code and kernel code

Liang Luo lluo1 at stevens.edu
Tue Sep 9 10:01:03 EDT 2014

I am not sure if I understand your question correctly. But If you are
referring to user mode and kernel mode in the concept of operating system,
developers use system calls to complete the transition from user to kernel
mode. Kernel mode or "kernel code" operates with system critical data
structures, direct memory access, hardware manipulation and so on. In my
opinion, "user code" should be safer than "kernel code". So I'm just
guessing, defining the security issues(levels) of a system is how they draw
the line between kernel mode and user mode.


On Mon, Sep 8, 2014 at 10:49 PM, xxu15 at stevens.edu <xxu15 at stevens.edu>

>  Hi,
> How to defferentiate between user code and kernel code ?
> Is there a standard to defferentiate the boundry of the two ? Or just the
> Unix designers/engineers defined the boundry ?
> Thank you.
> ------------------------------
>    Sincerely,
> Xiang Xu (徐祥)
> Student ID: 10388813
> tel: +1 (201) 918-0570
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