Code segment
Encyclopedia
In computing
, a code segment, also known as a text segment or simply as text, is one of the sections of a program in an object file
or in memory
, which contains executable
instructions.
It has a fixed size and is usually read-only
. If the text section is not read-only, then the particular architecture
allows self-modifying code
. Fixed-position or position independent code may be shared in memory by several processes in segmented or paged memory systems.
As a memory region, a code segment may be placed below the heap or stack in order to prevent heap
and stack overflow
s from overwriting it.
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
, a code segment, also known as a text segment or simply as text, is one of the sections of a program in an object file
Object file
An object file is a file containing relocatable format machine code that is usually not directly executable. Object files are produced by an assembler, compiler, or other language translator, and used as input to the linker....
or in memory
Computer memory
In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...
, which contains executable
Executable
In computing, an executable file causes a computer "to perform indicated tasks according to encoded instructions," as opposed to a data file that must be parsed by a program to be meaningful. These instructions are traditionally machine code instructions for a physical CPU...
instructions.
It has a fixed size and is usually read-only
Read-only
In computing, read-only can mean:* Read-only memory , a type of storage media* Read-only access to files or directories in file system permissions...
. If the text section is not read-only, then the particular architecture
Computer architecture
In computer science and engineering, computer architecture is the practical art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals and the formal modelling of those systems....
allows self-modifying code
Self-modifying code
In computer science, self-modifying code is code that alters its own instructions while it is executing - usually to reduce the instruction path length and improve performance or simply to reduce otherwise repetitively similar code, thus simplifying maintenance...
. Fixed-position or position independent code may be shared in memory by several processes in segmented or paged memory systems.
As a memory region, a code segment may be placed below the heap or stack in order to prevent heap
Heap overflow
A heap overflow is a type of buffer overflow that occurs in the heap data area. Heap overflows are exploitable in a different manner to that of stack-based overflows. Memory on the heap is dynamically allocated by the application at run-time and typically contains program data...
and stack overflow
Stack overflow
In software, a stack overflow occurs when too much memory is used on the call stack. The call stack contains a limited amount of memory, often determined at the start of the program. The size of the call stack depends on many factors, including the programming language, machine architecture,...
s from overwriting it.