5. Linux Application Address layout

5. Linux Application Address layout

Program Composition:

When you learn Linux application development, you often experience the following concepts: Code snippets, data segments, BSS segments (Block Started by Symbol, AKA: Uninitialized data segments), heap (heap), and stack (stack). These parts are also an important part of the Linux application.

Memory layout:

When a Linux application runs in memory, the above components are laid out in memory:

1. From low address to high address are: Code snippet, data segment, BSS segment, heap, stack.
2. The heap grows to a high memory address.
3. The stack grows to a low memory address.

The following program is tested below:

To view the threads of a system:

Here we look at the address assignment for this code:

Address of data storage:

1. Code snippet: Code, global constant (const), string constant.
2. Data segments: Global variables (initialization and uninitialized), static variables (global and local, initialized, and uninitialized).
3. Heap: Dynamically allocated regions
4. Stacks: Local variables (initialization and uninitialized, but excluding static variables), local read-only variables (const).

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From the above: The starting address of the code snippet is 8048000. Data segment start Address 8049000, heap start address b77a5000, stack starting address bfb47000.

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Analysis Data Storage location:

Example code:

#include <stdio.h>

#include <stdlib.h>

int global_init_a=1; Global init variable

int global_uninit_a; Global UnInit variable

static int static_global_init_a=1;

static int static_global_uninit_a;

const int const_global_a=12;

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int global_init_b=2; Global init variable

int global_uninit_b; Global UnInit variable

static int static_global_init_b=12;

static int static_global_uninit_b;

const int const_global_b=12;

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int main ()

{

???? int local_init_a=1;

???? int local_uninit_a;

???? static int static_local_init_a=1;

???? static int static_local_uninit_a;

???? const int const_local_a=12;

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???? int local_init_b=1;

???? int local_uninit_b;

???? static int static_local_init_b=1;

???? static int static_local_uninit_b;

???? const int const_local_b=12;

???? int * MALLOC_P_A;

???? Malloc_p_a=malloc (sizeof (int)); //

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???? printf ("&global_init_a =%p\n", &global_init_a);

???? printf ("&global_uninit_a =%p\n", &global_uninit_a);

???? printf ("&static_global_init_a =%p\n", &static_global_init_a);

???? printf ("&static_global_uninit_a =%p\n", &static_global_uninit_a);

???? printf ("&const_global_a =%p\n", &const_global_a);

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???? printf ("&global_init_b =%p\n", &global_init_b);

???? printf ("&global_uninit_b =%p\n", &global_uninit_b);

???? printf ("&static_global_init_b =%p\n", &static_global_init_b);

???? printf ("&static_global_uninit_b =%p\n", &static_global_uninit_b);

???? printf ("&const_global_b =%p\n", &const_global_b);

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???? printf ("&local_init_a =%p\n", &local_init_a);

???? printf ("&local_uninit_a =%p\n", &local_uninit_a);

???? printf ("&static_local_init_a =%p\n", &static_local_init_a);

???? printf ("&static_local_uninit_a =%p\n", &static_local_uninit_a);

???? printf ("&const_local_a =%p\n", &const_local_a);

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???? printf ("&local_init_b =%p\n", &local_init_b);

???? printf ("&local_uninit_b =%p\n", &local_uninit_b);

???? printf ("&static_local_init_b =%p\n", &static_local_init_b);

???? printf ("&static_local_uninit_b =%p\n", &static_local_uninit_b);

???? printf ("&const_local_b =%p\n", &const_local_b);

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???? printf ("&malloc_p_a =%p\n", &malloc_p_a);

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???? return 0;

}

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Analyze BSS Segments:

A BSS segment is a sub-segment of a data segment.

5. Linux Application Address layout