The usual and common implementation of 'user-land' in today's kernels is(Maybe this is to- o x86 specific?):
- Create new page tables for the process.
- Load the process's memory(data, code, etc)
- Notify the CPU about the usage of these page tables.
- Change CPU ring, and jump to the entry point.
Page tables has regions that distinguish between 'supervisor' and 'user', i.e. you can't use 'supervisor' addresses in the page table,
if you're in a low-privileged ring. This whole concept is used for like what? 40 years?(
A new concept i'm proposing is based on Intel''s virtualization technology, and the world's progression regarding virtualization
and virtual machines. Intel introduced a brand new CPU modes, called:
- VMX-ROOT: which is basically the 'regular' CPU mode you're all familiar with. No changes.
- VMX-NON-ROOT: a new CPU mode, which has the exact same privileges VMX-ROOT has, i mean, it can do ANYTHING. But wheres the catch?
You can actually trap this CPU with a whole lots of methods(trap with specific instructions, trap with interrupts...). By 'trapping', i mean when a certain
event occurs, you're code will begin to run. Just like interrupts.
So, why the heck shouldn't we use this concept and improve the current 'user-land' known concept?
The kernel will be loaded into 'VMX-ROOT' mode, and switch to 'VMX-NON-ROOT' whenever it chooses to. But how is memory seen by a code that is running in
'VMX-NON-ROOT' mode you're asking? Before Intel's new EPT technology, managing the memory for Virtual Machines was a living nightmare(Shadow page tables, i won't extend)
Intel introduced 'Extended page tables', which is basically a page-table that maps every linear address that is used in 'VMX-NON-ROOT' to an actual linear address;
much like the usual virtual-address to linear-address page tables.
This is a very basic introduction to the concept. Any thoughts?(This won't work, This will work...)