Does the kernel use virtual addresses?
The virtual address space where kernel resides is known as kernel space and where the application program resides is called user space.
Does kernel use physical address?
Yes, kernel mode code uses virtual address space. The kernel manages physical address space but it doesn’t run in physical address space.
What is kernel virtual address?
The operating system supports a flat 32-bit virtual address space. The bottom 2 GB of the address space is for user processes, while the top 2 GB is for the kernel. The kernel address space is statically mapped into the address space.
What is physical address and virtual address?
Physical addresses refer to hardware addresses of physical memory. Virtual addresses refer to the virtual store viewed by the process. only a portion of the address space that processes do use is loaded into physical memory at a time.
Why virtual memory is used in Linux?
Linux supports virtual memory, that is, using a disk as an extension of RAM so that the effective size of usable memory grows correspondingly. Of course, reading and writing the hard disk is slower (on the order of a thousand times slower) than using real memory, so the programs don’t run as fast.
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”.
Which call we can use to get virtual address in Linux kernel?
kmap() creates a mapping in kernel for an arbitrary physical page (can be from highmem) and returns a virtual address that can be used to directly reference the page.
How do I find the physical address in Linux?
Linux
- Open a terminal and use the ifconfig command. The MAC address will be listed next to HWaddr.
- If your Linux OS does not have the ifconfig command, you may also use the ip addr command.
What is physical address Linux?
Every network interface has a MAC address (Media Access Controller) also known as the physical address. This is the actual hardware address that the lowest level of the network uses to communicate. The MAC address is used to assign the TCP/IP address by means of DHCP (Dynamic Host Configuration Protcol).
What is virtual address and physical address?
What is physical address example?
Physical address means the location of the building that houses a private security services business or training school or the location where the individual principals of a business reside. A post office box is not a physical address. Sample 1.
Where are the virtual addresses in the kernel?
Kernel Virtual Addresses are addresses in the region above the kernel logical address mapping. This is also called the area.
How are address spaces created in the Linux kernel?
Creating and modifying address spaces for kernel and processes is done using the same generic code which relies on macros and functions to translate these generic operations in code that runs on different architectures. Here is an example of how we can translate a virtual address to a physical address, using the Linux page table APIs:
Is the returned address usable as a virtual address?
The returned address is not guaranteed to be usable directly as a virtual address. Like user space, the kernel accesses memory through page tables; as a result, when kernel code needs to access memory-mapped I/O devices, it must first set up an appropriate kernel page-table mapping. The in-kernel tool for that job has long been ioremap ().
Is the physical address of the kernel dereferenced?
The in-kernel tool for that job has long been ioremap (). A successful call to ioremap () returns a kernel virtual address corresponding to start of the requested physical address range. This address is not normally meant to be dereferenced directly, though, for a number of (often architecture-specific) reasons.