How physical to virtual translations works in Linux?

How physical to virtual translations works in Linux?

Linux divides the virtual address space into two: the lower portion is used for user processes, and there is a different virtual to physical mapping for each process. The upper portion is used for the kernel, and the mapping is the same even when switching between different user processes.

Is kernel memory virtual or physical?

Yes. Kernel stack of a process is physically contiguous. It is typically few pages worth of memory, usually about 4K -16K depending on the architecture.

Can kernel access physical memory?

Even the kernel has no direct access to physical memory in the way your are thinking. Basically the kind of memory you seem to imagine (linear memory with flat addressing) is something that is constructed by the kernel (from physical memory banks) and exported, it doesn’t “exist”.

What is kernel virtual address?

Each user-mode process has its own private virtual address space, but all code that runs in kernel mode shares a single virtual address space called system space. The virtual address space for a user-mode process is called user space.

Does Linux kernel use virtual memory?

3 Answers. Show activity on this post. When a system uses virtual memory, the kernel uses virtual memory as well.

Does kernel space use virtual memory?

The kernel virtual memory contains the code and data structures in the kernel. Some regions of the kernel virtual memory are mapped to physical pages that are shared by all processes. For example, each process shares the kernel’s code and global data structures.

How does Linux divide the kernel’s virtual address space?

Linux divides the kernel virtual address space to two parts – lowmem and vmalloc. Lowmem uses a 1-1 mapping between virtual and physical addresses. I.e. virtual address X is mapped to physical address X-C (where C is some constant, e.g. 3GB).

Are kernel virtual addresses just an offset from physical memory?

So each kernel virtual address is indeed just an offset from physical memory (DRAM). Also, it’s my understanding that as Linux is a modern virtual memory OS, (pretty much) all addresses are treated as virtual addresses and must “go” via hardware – the TLB/MMU – at runtime and then get translated by the TLB/MMU via kernel paging tables.

How are kernel virtual addresses treated in Linux?

Also, it’s my understanding that as Linux is a modern virtual memory OS, (pretty much) all addresses are treated as virtual addresses and must “go” via hardware – the TLB/MMU – at runtime and then get translated by the TLB/MMU via kernel paging tables. Again, easy to understand for user-mode processes. HOWEVER, what about kernel virtual addresses?

How do I create a physical disk image in Linux?

On the physical Linux Server, run the dd (data duplicator) utility for each physical disk ( /dev/sda, /dev/sdb etc.) and create the image of each disk. You can attach a USB hard disk drive to your physical Linux machine and store the images made with the dd utility on that USB HDD.