Needs to interrupt the CPU and execute a handler. Needs to take a primary interrupt-that is, something in the (built-in) hardware There are only a few good reasons for a developer to write Not necessarily mean that it should be a kernel extension in OS X. When you are trying to determine if a piece of code shouldīe a KEXT, the default answer is generally no.Įven if your code was a system extension in Mac OS 9, that does Kernel interfaces, you should use a higher level of abstraction when Unless your application requires low-level access to OS X guarantees that threading in applications is just asĮfficient as threading inside the kernel, so efficiency should notīe an issue. Use of KEXTs is strongly discouraged in situations where user-level solutionsĪre feasible. Restrict or don’t permit the use of third-party KEXTs. In contrast,Ī memory access error in a KEXT causes a kernel panic, crashingįinally, for security reasons, some customers For example, a memory access error in a userĪpplication can, at worst, cause that application to crash. A badly behaved kernel extension in OS X can causeĪs much trouble as a badly behaved application or extension couldīugs in KEXTs can have far more severe consequences than bugs In addition, although memory protection keeps applicationsįrom crashing the system, no such safeguards are in place inside

Than resources in a user-space task of equivalent functionality. (permanently resident in memory) and are thus more costly to use Modules, and must conform to strict guidelines. Service that requires access to internal kernel interfaces.īecause KEXTs run in supervisor mode in the kernel’sĪddress space, they are also harder to write and debug than user-level Because these kernel extensions ( KEXTs) provide both modularityĪnd dynamic loadability, they are a natural choice for any relatively self-contained OS X provides a kernel extension mechanism as a means of allowingĭynamic loading of code into the kernel, without the need to recompile As discussed in the chapter Kernel Architecture Overview,

Darwin kernel os