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"Kernel space" redirects here. For the mathematical definition, see Null space. A conventional computer operating system usually segregates virtual memory into kernel space and user space. Kernel space is strictly reserved for running the kernel, kernel extensions, and most device drivers. In contrast, user space is the memory area where all user mode applications work and this memory can be swapped out when necessary.
Similarly, the term userland refers to all application software that runs in user space.[1] Userland usually refers to the various programs and libraries that the operating system uses to interact with the kernel: software that performs input/output, manipulates file system objects, etc.
Each user space process normally runs in its own virtual memory space, and, unless explicitly requested, cannot access the memory of other processes. This is the basis for memory protection in today's mainstream operating systems, and a building block for privilege separation. A separate user mode can also be used to build efficient virtual machines -- see Popek and Goldberg virtualization requirements. Depending on the privileges, processes can request the kernel to map part of another process's memory space to its own, as is the case for debuggers. Programs can also request shared memory regions with other processes.
One approach to implementing a user mode separate from supervisor mode involves hardware protection rings (ring (computer security)).
Another approach taken in experimental operating systems is to have a single address space for all software, and rely on the programming language's virtual machine to make sure that arbitrary memory cannot be accessed — applications simply cannot acquire any references to the objects that they are not allowed to access.[2] This approach has been implemented in JXOS, Unununium as well as Microsoft's Singularity research project.
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External links [edit]
 SC Magazine UK |
SC Magazine UK
Fri, 17 May 2013 07:46:53 -0700
“I think that this technology will move down to the SMB market, to 50 users and below, and then to the 50-150 user space and the 150-1,000 also,” Scott said. “I don't see it in the 1,000+ user market as almost every application is moving to the cloud ...
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Forbes
Mon, 13 May 2013 08:04:49 -0700
Android is the opposite: only minimal changes to the kernel, but a user-space wholly unlike that of any other Unix system. In fact, Android's user-space is so different from stock Linux, you can easily say that Android is not in any way a Linux system ...
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Tell Me News
Mon, 20 May 2013 09:34:29 -0700
In BES 10 through a module BlackBerry Balance the user space and work space are clearly separated. Blackberry can't integrate Balance into the other phones because it's not part of the native OS. However, it's managing it by creating secure containers.
|  6abc.com |
6abc.com
Wed, 24 Apr 2013 08:39:48 -0700
... and that's not better or worse," he said. "So in that way, the subscription models are going to make more sense." But he doesn't count Apple out in that future: "It may be that Apple and iTunes are going to create the best user space to own that ...
|  TweakTown |
TweakTown
Mon, 20 May 2013 22:02:31 -0700
lexar_professional_128gb_compact_flash_memory_card_review. The back of the card gives the end-user space to record what data is on, or has been written to the card. lexar_professional_128gb_compact_flash_memory_card_review. The interface used ...
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Dark Reading
Tue, 14 May 2013 04:57:40 -0700
"Sandboxing just isolates the application user space code. [It] assumes that the bad stuff is executing as an application within the context of an application, when in fact, the bad stuff could be executing within the kernel anyway because the kernel ...
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ITworld.com
Thu, 16 May 2013 11:00:16 -0700
Additionally, you could do more fancy partitioning for user space and such, but this is way is simpler and it works just fine for how often you'll likely be using your Linux installation (i.e. a few times). Step 4: Install Mac OS. As I previously ...
|  McGill Reporter |
McGill Reporter
Tue, 07 May 2013 13:28:38 -0700
As far as other trends in libraries, there's an emphasis on embedded librarians, on the renovation of user space for informal learning spaces, and less reliance upon an open-stack library concept. Lots of books, lots of materials that are seldom used ...
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