[plug] Query related to kernel mode and UML
Leon Brooks
leon at brooks.fdns.net
Tue Apr 20 15:27:21 WST 2004
On Tue, 20 Apr 2004 15:13, Parag Nemade wrote:
> when i run a simple C program i am in kernel mode or
> in user mode?
User.
> when system call is called in a C program in which
> mode i am ?
The short answer is, you are in kernel mode. To answer this one fully
takes a long time.
> Also what is User Mode Linux(UML). what is difference
> between UML and Simple LINUX KERNEL?
UML runs more or less as a program under a standard Linux kernel.
Programs run from it are clients of a client.
> When i modify kernel and add some functions in kernel
> and boot it? my functions runs in kernel mode or user
> mode?
Short answer is kernel mode. Long answer is as before, very long.
> Is there any connection of modification of kernel to
> UML?
UML is good for modifying the kernel and trying out your modifications
without such a great risk of doing something irreversible to your
uptime (or filesystems). It's also useful as a "poor man's SElinux" or
"super-chroot", for putting each user or service into its own separate
virtual cage.
Cheers; Leon
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