What is kernel space process?
Kernel space is where the kernel (i.e., the core of the operating system) executes (i.e., runs) and provides its services. User space is that set of memory locations in which user processes (i.e., everything other than the kernel) run. A process is an executing instance of a program.
What does Access_ok return?
The first question comes from this description of access_ok’s return: The function returns non-zero if the region is likely accessible (though access may still result in -EFAULT). This function simply checks that the address is likely in user space, not in the kernel.
What is the difference between kernel process and user process?
1 Answer. User-space processes have its own virtual address space. Kernel processes or threads do not have their own address space, they operate within kernel address space only. And they may be started before the kernel has started any user process (e.g. init).
How to tell whether a process is in kernel or user space?
The user code will run in user space until it requires kernel services, i.e. a kernel system call. The program will then cause a trap which switches the CPU to protected mode where the kernel code executes the system call (e.g. to read or write a file).
Is the kernel memory shared with other processes?
As the physical memory is shared among all other tenants running on the same hardware, this may include the physical memory of other processes, the kernel, and in the case of paravirtualization, the memory of the hypervisor or other co-located instances.
How is the address space of a process determined?
The location of the split is determined by the value of PAGE_OFFSETwhich is at 0xC0000000on the x86. This means that 3GiB is available for the process to use while the remaining 1GiB is always mapped by the kernel. The linear virtual address space as the kernel sees it is illustrated in Figure ??. Figure 4.1: Kernel Address Space
What’s the fastest way to dump kernel memory?
While the performance heavily depends on the specific machine—for example, processor speed, TLB and cache sizes, and DRAM speed—we can dump arbitrary kernel and physical memory at a speed of 3.2KiB/s to 503KiB/s. Countermeasures.