/* file: segments.c
   original author: "The Linux Kernel Book", Card, Dumas & Mavel (Wiley)
   heavily adapted by: T.P. Baker
   purpose:

   Illustrate Linux process address space layout.

*/

#include <stdio.h>
#include <stdlib.h>

static int i[1000];       /* uninitialized static storage (BSS) */
static int j = 2;         /* initialized static storage (DATA) */
static int k = 3;         /* read-only initialized static storage  (RODATA) */
const char l[] = "linux"; 

extern int _end;          /* end of BSS segment */
extern int _etext;        /* end of code segment (text) */
extern int _start;        /* entry point */
extern int _edata;        /* end of initialized data segment */
extern int __bss_start;   /* start of bss segment */
extern int __data_start;  /* start of bss segment */


extern char **environ;    /* pointer to environment */

int main (int argc, const char *argv[]) {

  int *m; /* local pointer (on stack) */

  printf ("%09lx : environ[0]   \n", environ[0]);
  printf ("%09lx : argv[0]      \n", argv[0]);
  printf ("%09lx : &m           \n", &m);

  m = malloc (100);
  printf ("%09lx : m            \n", m);
  printf ("%09lx : &_end        \n", &_end);
  printf ("%09lx : i            \n", i);
  printf ("%09lx : &__bss_start \n", &__bss_start);
  printf ("%09lx : &_edata      \n", &_edata);
  printf ("%09lx : &k           \n", &k);
  printf ("%09lx : &j           \n", &j);
  printf ("%09lx : &__data_start\n", &__data_start);
  printf ("%09lx : &l           \n", &l);
  printf ("%09lx : &_etext      \n", &_etext);
  printf ("%09lx : main         \n", main);
  printf ("%09lx : &_start      \n", &_start);

  return 0;
}

/*

output with Red Hat 7.3 Linux distribution:

0bffffbdb : environ[0]   
0bffffbd3 : argv[0]      
0bffffa64 : &m           
00804a8e8 : m            
00804a8c0 : &_end        
008049920 : i            
0080498f8 : &__bss_start 
0080498f8 : &_edata      
0080497f4 : &k           
0080497f0 : &j           
0080497e0 : &__data_start
008048668 : &l           
00804865e : &_etext      
008048490 : main         
008048390 : &_start      

*/