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OS X and iOS Kernel Programming by Douglas Clarke, Ole Henry Halvorsen

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Mapping Memory

Mapping memory refers to the function of making a range of memory from one task available to another. At the lowest level, mapping is handled by the Mach VM subsystem, as discussed in Chapter 2. Memory mapping provides a fast way for tasks to share resources without copying memory, as mapping makes the same memory available between tasks. Writable mappings can be shared until a modification is made, in which case the copy-on-write (COW) optimization is used to copy only the memory that was modified. Memory mappings can occur in a variety of different ways, between multiple tasks, or from the kernel to a user space task or vice versa.

Mapping Memory from a User Space Task into Kernel Space

Mapping memory from a user space task is ...

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