kernel-mode

When we compile a C program, it just generates some machine-understandable code. This code can directly run on the hardware, telling from this question . So my questions are: If a C program can directly run on the hardware, how can the kernel handle the resource allocation for this program? If the executable generated from the compiler is in pure machine-understandable form, then how do the privileged and non-privileged modes work? How does the kernel manage the permission of hardware resources if a program can directly run on the hardware not through the kernel? If a C program can directly

I am trying to run following code, which was copied from here . I have made few changes to run it with older kernel versions. When I insert kernel module, nlmsg_multicast() fails and logs as nlmsg_multicast() error: -3 in /var/log/messages . While running user space program, socket() fails. What exactly I want to do is, kernel module creates a socket, regardless of any process in user space kernel module send some events to user space If any process in user space reply to an event, kernel module process on that reply Since, It may happen that no process in user space available to reply on

how can I obtain runtime information about which version of kernel is running from inside linux kernel module code (kernel mode)? By convention, Linux kernel module loading mechanism doesn't allow loading modules that were not compiled against the running kernel, so the "running kernel" you are referring to is most likely is already known at kernel module compilation time. For retrieving the version string constant, older versions require you to include <linux/version.h> , others <linux/utsrelease.h> , and newer ones <generated/utsrelease.h> . If you really want to get more information at run