Process Address Space
Whenever an executable file is executed, it becomes a process. An executable file contains binary code grouped into a number of blocks called segments. Each segment is used for storing a particular type of data. A few segment names of a typical ELF executable file are listed below.
- text — Segment containing executable code
- .bss — Segment containing data initialized to zero
- data — Segment containing initialized data
- symtab — Segment containing the program symbols (e.g., function name, variable names, etc.)
- interp — Segment containing the name of the interpreter to be used
The readelf command can provide further details of the ELF file. When such a file is loaded in the memory for execution, the segments are loaded in memory. It is not necessary for the entire executable to be loaded in contiguous memory locations. Memory is divided into equal sized partitions called pages (typically 4KB). Hence when the executable is loaded in the memory, different parts of the executable are placed in different pages (which might not be contiguous). Consider an ELF executable file of size 10K. If the page size supported by the OS is 4K, then the file will be split into three pieces (also called frames) of size 4K, 4K, and 2K respectively. These three frames will be accommodated in any three free pages in memory.
Read more about this topic: Fork (operating System)
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“Take a red book called TELEPHONE,
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“Through space the universe encompasses and swallows me up like an atom; through thought I comprehend the world.”
—Blaise Pascal (1623–1662)