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

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Types of Memory

The kernel deals with multiple types of memory, so understanding the difference is key to implementing a successful driver or kernel extension.

The types of memory can be categorized as:

  • CPU physical address
  • bus physical address
  • user and kernel virtual addresses

In addition to the three types of memory addresses, the amount of addressable memory differs between architectures and can be from 32-bit to 64-bit. Memory may also be ordered differently depending on the architecture and can be of little or big endian.

The following sections will discuss the importance and usage of each type of memory as it applies to kernel programming.

CPU Physical Address

A physical address refers to the addressing system used by the CPU to access ...

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