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I want to implementing my own system call. (See below link)
http://www.tldp.org/HOWTO/html_single/Implement-Sys-Call-Linux-2.6-i386/
But adding new system call requires kernel compilation.
How to implement my own system call without recompiling the Linux kernel?
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You can't. Without recompiling the kernel, all you can do is build and load kernel modules, and kernel modules cannot add new system calls.
The original definition of a system call is/was a system support (OS) function that is called by a trap of some kind rather than a "normal" function call. So by that definition, every system call requires a switch to kernel mode, as if it didn't it wouldn't be a system call (just a normal system library call).
For All Practical Purposes. In nearly all cases, you won't ever have to make direct system calls in your C programs. If you use assembly language, however, the need may arise.
Sure, you can.
In short, you'll need to patch the running kernel.
There are at least 2 ways to add a new syscall:
sys_call_table and ia32_sys_call_table) and patch system call limit check instruction (usally cmp on x86) at any of the system call entries (system_call, ia32_system_all etc...)call on x86) to point to table's copy and patch system call limit check instruction at any of the system call entries.See this anwers for details:
Implementing Linux System Call using LKM
How do 32-bit applications make system calls on 64-bit Linux?
:)
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