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Several computer systems introduced in the 1960s, such as the IBM System/360, DEC PDP-6/PDP-10, the GE-600/Honeywell 6000 series, and the Burroughs B5000 series and B6500 series, support two CPU modes; a mode that grants full privileges to code running in that mode, and a mode that prevents direct access to input/output devices and some other hardware facilities to code running in that mode.
The Linux kernel got the prerequisite for kernel-based mode setting by accepting Intel GEM in version 2.6.28, released in December 2008. [2] This will be [needs update] replaced by Tungstens Graphics TTM (Translation Table Maps) memory manager which supports the GEM API. [3]
Processor Control Region (PCR) is a Windows kernel mode data structure that contains information about the current processor. It can be accessed via the fs segment register on x86 versions, or the gs segment register on x64 versions respectively.
The upper part is accessible only from kernel mode, and with some exceptions, is instantiated just once, system-wide. ntoskrnl.exe is mapped into this region, as are several other kernel mode components. This region also contains data used by kernel mode code, such as the kernel mode heaps and the file system cache.
A modern computer operating system usually uses virtual memory to provide separate address spaces or separate regions of a single address space, called user space and kernel space. [ 1 ] [ a ] Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour.
The Windows 9x kernel is a 32-bit kernel with virtual memory. Drivers are provided by .VXD files or, since Windows 98, the newer WDM drivers can be used. [2] However, the MS-DOS kernel stays resident in memory. Windows will use the old MS-DOS 16-bit drivers if they are installed, except on Windows Me. In Windows Me, DOS is still running, but ...
Therefore, to use a TSS the following must be done by the operating system kernel: Create a TSS descriptor entry in the GDT; Load the TR with the segment selector for that segment; Add information to the TSS in memory as needed; For security purposes, the TSS should be placed in memory that is accessible only to the kernel.
The Session Manager Subsystem is the first user-mode process started by the kernel. Once started it creates additional paging files with configuration data from HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management, [1] the environment variables located at the registry entry HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment, and DOS device mappings (e.g. CON ...