Thanks a lot Dace and Vladimir for your replies. First of all, I forgot to mention that I am talking for x86 architecture.
The CPU registers will contain the virtual addresses. Each and every time that the CPU tries to access a virtual memory location, then the address will be translated by the MMU into a physical address.
So, AFAIU the translation to physical memory takes place *only* when the ALU of the processor has to do some operation which has memory operands (in this case the CPU needs to deal with the *real* addresses) but not prior to that. Now if, for example, EIP has the value of 0xB71B13E8 and I know that on B70CC000-B71B7000 the libX11.so is linked, then the IP points to the 0xE53E8 (0xB71B13E8 - B70CC000) offset of libX11.so? Is that right? Thanks again for all the useful help. John K. -----Original Message----- From: Dave Hylands [mailto:dhylands@gmail.com] Sent: Wednesday, April 20, 2011 12:20 AM To: limp Cc: kernelnewbies@kernelnewbies.org Subject: Re: VMA of processes and CPU registers Hi John, On Tue, Apr 19, 2011 at 3:56 PM, limp <johnkyr83@hotmail.com> wrote:
Hi all,
I know that each user processes has a number of virtual memory areas (VMA) which consist its (virtual memory) address space. For example cat /proc/1426/maps will return the (virtual memory) address space of the process 1426.
What I don't know for sure is if the actual CPU registers contain the virtual address of a running process or the "translated" by MMU physical address.
I think that every access to a VA must be resolved to a corresponding PA so I guess the CPU registers will deal with the physical addresses rather than the virtual ones but I wanted to be sure about it.
The CPU registers will contain the virtual addresses. Each and every time that the CPU tries to access a virtual memory location, then the address will be translated by the MMU into a physical address. Generally speaking. the only time you actually deal with physical addresses is when you're setting up the MMU, and when programming hardware (like DMA) which accesses memory without going through the MMU. -- Dave Hylands Shuswap, BC, Canada http://www.davehylands.com