Windows - How does this memory addressing work?

Question

Assuming x86, I'm starting to learn that addresses 0x0 thru 0x7FFFFFFF are for the process; whereas anything higher is reserved for the kernel.

I have three curiosities:

1) Does a process EVER call an address higher than 0x7FFFFFFF? I assume it will always result in some sort of access denied? How is that access denied enforced?

2) Does "shared memory" IPC work by mapping two processes virtual addresses to the same physical address range?

3) The amount of RAM in your machine can vary. You may have 2GB, or much more like 16GB. How does this affect the addressing of RAM? Does the kernel ever leave a bunch of RAM unused because it was reserved for itself, but doesn't need it? How can I see this?

Answer 1

I am not very sure but you will find the maximum in this MSDN doc about how it works:-

The range of virtual addresses that is available to a process is called the virtual address space for the process. Each user-mode process has its own private virtual address space. For a 32-bit process, the virtual address space is usually the 2-gigabyte range 0x00000000 through 0x7FFFFFFF. For a 64-bit process, the virtual address space is the 8-terabyte range 0x000'00000000 through 0x7FF'FFFFFFFF. A range of virtual addresses is sometimes called a range of virtual memory.

The diagram shows the virtual address spaces for two 64-bit processes: Notepad.exe and MyApp.exe. Each process has its own virtual address space that goes from 0x000'0000000 through 0x7FF'FFFFFFFF. Each shaded block represents one page (4 kilobytes in size) of virtual or physical memory. Notice that the Notepad process uses three contiguous pages of virtual addresses, starting at 0x7F7'93950000. But those three contiguous pages of virtual addresses are mapped to noncontiguous pages in physical memory. Also notice that both processes use a page of virtual memory beginning at 0x7F7'93950000, but those virtual pages are mapped to different pages of physical memory.