Linux Small Program Analysis

Environment CentOS 5.x

Program Example 1: #include <stdio.h> #include <stdlib.h>   void bug () {     system ("reboot");//re boot system    exit (0);//end process    }   int stack_test (INT&NBSP;A,INT&NBSP;B)//function stack   Press in   main function, a copy value, b in high address  {//the stack order is the parameter from right to left, then the stack frame, and the order of evaluation is undefined, determined by the compiler implementation.      printf ("before write: 0x%x\n", b);//output write before B value       int *p=&a;    //p Point to a     p++;     //p offset to b      *p=0xdddd;//*p value change  b changed       printf ("after write: 0x%x\n", b);     int c=0xcccc;      return c; } int main ()  {     int a=0xaaaa;      int b=0xbbbb;     int rEt=stack_test (A, b);      printf ("you shoule run here\n");      return ; }  //Program Example 2: #include <stdio.h> #include <stdlib.h>  void bug () {    system ("reboot");//reboot system     Exit (0);//end process   }   int stack_test (INT&NBSP;A,INT&NBSP;B)  {     int *p=&a;     p--;      *p=bug;     int c=0xcccc;     return c ;  }  int main ()  {     int a=0xaaaa;      int b=0xbbbb;     int ret=stack_test (A, b);      printf ("you shoule run here\n");      return ; }    //Output Result: BEFORE&Nbsp;write: 0xbbbb//          after write:  0xdddd//          you shoule run here//(GDB)  p &a  centos  gdb Debug Information/*  (GDB)  p&a$1 =  (int *)   0xbffff630 (GDB)  p&b$2 =  (int *)  0xbffff634 (GDB)  p&p$3 =  (int  **)  0xbffff620 (gdb)  p&c$4 =  (int *)  0xbffff624 (gdb)  n14p--;(gdb)  p p$5 =  (int *)  0xbffff630 (gdb)  n15*p=bug; (GDB)  p p$6 =   (int *)  0xbffff62c (gdb)  p *p$7 = 134513797 (GDB) &NBSP;N21INT&NBSP;C=0XCCCC ;(gdb)  p* p$8 = 134513684 (GDB)  p bug$9 = {void  ()} 0x8048414  <bug> (GDB)  p& bug$10 =  (void  (*) ())  0x8048414 <bug> GDB)  n22return  c; (GDB)  n23} (GDB)  nbug  ()  at process.c:55{(GDB)  nbreakpoint 2, bug   ()  at process.c:66system ("reboot");//re boot system by debugging   information and available: ESP moves first when a function is called   Press in   parameter b,a   return function pointer  return (a add-4)   then press ebp  to make EBP equal to ESP when EBP records the return information   When the ESP moves sequentially into the local variable  p c  ,p begins to point to a,p--, p points to ebp to point to space, and when P=bug   p logs the bug function stack frame, return c   called the bug  function   system restart */

Linux Small Program Analysis