Hi All, I have Implemented sample system call on tree 3.4.6 Following are the steps i did - - >I created directory hello in kernel sources base directory i.e /usr/src/kernels/linux3.4.6/hello -> I have created hello.c file in which i added system call definition #include <linux/kernel.h> asmlinkage long sys_helloworld() { printk(KERN_NOTICE "\n hello system call "); return 0; } In makefile obj-y:= hello.c -> In syscall tabel arch/x86/syscalls/syscall_32.tbl added - 349 i386 helloworld sys_helloworld Then compiled the kernel and installed it. However when i run application strace ouput shows enosys(function not implemneted) application as below int main() { syscall(349) return 0; } strace shows SYS_349(0x1000,0x804843b,..,..,0)=-1 ENOSYS(function not implemneted) I checked /proc/kallsyms it shows the sys_helloworld symbol I also tried adding entry in syscall_64.tbl as common though i am running 32 bit kernel. gdb syscall 349 doesnot give anything Can anyone tell what is wrong here ? Thanks, -Ulka -- Director L2IT -Learn & Leverage Information Technology Leading Professional Training Institute in Pune www.l2it.com