Search results
Results from the WOW.Com Content Network
In computing, protected mode, also called protected virtual address mode, [1] is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as segmentation, virtual memory, paging and safe multi-tasking designed to increase an operating system's control over application software.
The processor executes the SMM code in a separate address space (SMRAM) that has to be made inaccessible to other operating modes of the CPU by the firmware. [7] System Management Mode can address up to 4 GB memory as huge real mode. In x86-64 processors, SMM can address >4 GB memory as real address mode. [8]
Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that has not been allocated to it.
A memory protection unit (MPU) is a computer hardware unit that provides memory protection. It is usually implemented as part of the central processing unit (CPU). [ 1 ] MPU is a trimmed down version of memory management unit (MMU) providing only memory protection support.
Computer operating systems provide different levels of access to resources. A protection ring is one of two or more hierarchical levels or layers of privilege within the architecture of a computer system. This is generally hardware-enforced by some CPU architectures that provide different CPU modes at the hardware or microcode level. Rings are ...
A Replay Protected Memory Block (RPMB) is provided as a means for a system to store data to the specific memory area in an authenticated and replay protected manner and can only be read and written via successfully authenticated read and write accesses. The data may be overwritten by the host but can never be erased.
Direct memory access (DMA) is a feature of computer systems that allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU). [ 1 ] Without DMA, when the CPU is using programmed input/output , it is typically fully occupied for the entire duration of the read or write operation, and is thus ...
Protection relies upon hardware memory protection and thus overhead is typically not substantial, although it can grow significantly if the program makes heavy use of allocation. [16] Randomization provides only probabilistic protection against memory errors, but can often be easily implemented in existing software by relinking the binary.