The Linux Programming Interface

49MEMORY MAPPINGS

This chapter discusses the use of the mmap() system call to create memory mappings. Memory mappings can be used for IPC, as well as a range of other purposes. We begin with an overview of some fundamental concepts before considering mmap() in depth.

49.1 Overview

The mmap() system call creates a new memory mapping in the calling process’s virtual address space. A mapping can be of two types:

• File mapping: A file mapping maps a region of a file directly into the calling process’s virtual memory. Once a file is mapped, its contents can be accessed by operations on the bytes in the corresponding memory region. The pages of the mapping are (automatically) loaded from the file as required. This type of mapping is also known as ...