How can I get address in physical addressing area by pointer in virtual addressing area?

Question

If I have an address (pointer) in virtual addressing area of current process to the pinned (page-locked) memory, then how can I get an address (pointer) in physical addressing area, of this memory region, by using POSIX?

• CPU: x86
• OS: Linux 2.6 and Windows 7/8(Server 2008R2)

Answer 1

You cannot access physical addresses in user space. Everything you do goes through the MMU and the page tables. Even if you pin a page, the kernel may still move it around in physical memory.

Even if you got it, what would it do for you? A userspace process cannot access memory directly by physical access. Only kernel mode can.

If you really need the functionality (although I still can't image any way of using the information), you have to write a kernel mode driver.