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The stack is often used to store variables of fixed length local to the currently active functions. Programmers may further choose to explicitly use the stack to store local data of variable length. If a region of memory lies on the thread's stack, that memory is said to have been allocated on the stack, i.e. stack-based memory allocation (SBMA).
In computing, a stack trace (also called stack backtrace [1] or stack traceback [2]) is a report of the active stack frames at a certain point in time during the execution of a program. When a program is run, memory is often dynamically allocated in two places: the stack and the heap .
If a function-local allocation is found to be accessible to another function or thread, the allocation is said to "escape" and cannot be done on the stack. Otherwise, the object may be allocated directly on the stack and released when the function returns, bypassing the heap and associated memory management costs. [21]
This includes all sorts of active memory regions like code segment containing (mostly) program instructions (and occasionally constants), data segment (both initialized and uninitialized), [1] heap memory, call stack, plus memory required to hold any additional data structures, such as symbol tables, debugging data structures, open files ...
The GNU Compiler Collection (GCC) for C allocates memory for VLAs with automatic storage duration on the stack. [5] This is the faster and more straightforward option compared to heap-allocation, and is used by most compilers. VLAs can also be allocated on the heap and internally accessed using a pointer to this block.
A buffer overflow occurring in the heap data area is referred to as a heap overflow and is exploitable in a manner different from that of stack-based overflows. Memory on the heap is dynamically allocated by the application at run-time and typically contains program data.
Exploits often use specific bytes to spray the heap, as the data stored on the heap serves multiple roles. During exploitation of a security issue, the application code can often be made to read an address from an arbitrary location in memory. This address is then used by the code as the address of a function to execute.
This shows the typical layout of a simple computer's program memory with the text, various data, and stack and heap sections.. In computing, a code segment, also known as a text segment or simply as text, is a portion of an object file or the corresponding section of the program's virtual address space that contains executable instructions.