strange new system call problems

[kwl02r <kwl02r@ecs.soton.ac.uk>]

    Hiya,

    I am running the Redhat9 with kernel-2.4.20-8. I added four new 
system calls for my application program.
    At file /asm/unistd.h, I added my system calls definition as following.
   
    #define __NR_set_tid_address    258 /* last system call defined by 
system*/

   #define __NR_mysystemcall1  259  /* my first system call*/
   #define __NR_mysystemcall2  260  /* my second system call*/
   #define __NR_mysystemcall3  261  /* my third system call*/
   #define __NR_mysystemcall4  262  /* my forth system call*/

   After this , I changed the linux/arch/i386/entry.S as following.
  . long SYMBOL_NAME(sys_mysystemcall1)             /* 259 system call */
  .long SYMBOL_NAME(sys_mysystemcall2)              /* 260 system call */
  .long SYMBOL_NAME(sys_mysystemcall3)              /* 261 system call */
  .long SYMBOL_NAME(sys_mysystemcall4)              /* 262 system call */

   When I compilered a new kernel, there was no any error messages.
   But only the new system call 259 was working. The rest of three 
(260-262) did not response
   anything. If I changed the position of system calls (259->260 and 
260->259), still the 259 had
   response. Anyway, only the new system call at the 259 position was 
working. What is wrong?
   Other questions are:
   (1) Is it correct that I add my new definitions at 
/linux/asm/unistd.h? There is another file under
         /linux/asm-i386/unistd.h
   (2) At entry.S, do I need to change codes following for my new system 
calls? How to change ?
       
       .rept NR_syscalls-(.-sys_call_table)/4
               .long SYMBOL_NAME(sys_ni_syscall)
        .endr

Thanks