[완료]mips에서 system call hooking 관련 문의 입니다.

#include <linux/kernel.h>
#include <linux/module.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
 
void **system_call_table_address = (void *)0x<system call table>;
 
asmlinkage int (*orig_read)(int fd, void *buf, size_t count);
asmlinkage int hook_read(int fd, void *buf, size_t count)
{
    printk("read........................\n");
    return orig_read(fd, buf, count);
}
 
static int __init stest_init(void)
{
 
    orig_read = (void *)system_call_table_address[__NR_read - __NR_Linux];
    system_call_table_address[__NR_read - __NR_Linux ] = hook_read;
 
    return 0;
 
}
 
static void __exit stest_cleanup(void)
{
 
    system_call_table_address[__NR_read - __NR_Linux] = orig_read;
    system_call_table_address[__NR_read - __NR_Linux ] = hook_read;
 
    return 0;
 
}
 
static void __exit stest_cleanup(void)
{
 
    system_call_table_address[__NR_read - __NR_Linux] = orig_read;
 
}
 
module_init(stest_init);
module_exit(stest_cleanup);
MODULE_LICENSE("GPL");

코드를 보시면 system call table의 read에 접근 하려면 
__NR_read - __NR_Linux

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1995, 96, 97, 98, 99, 2000 by Ralf Baechle
   7  * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
   8  *
   9  * Changed system calls macros _syscall5 - _syscall7 to push args 5 to 7 onto
  10  * the stack. Robin Farine for ACN S.A, Copyright (C) 1996 by ACN S.A
  11  */
  12 #ifndef _ASM_UNISTD_H
  13 #define _ASM_UNISTD_H
  14
  15 #include <asm/sgidefs.h>
  16
  17 #if _MIPS_SIM == _MIPS_SIM_ABI32
  18
  19 /*
  20  * Linux o32 style syscalls are in the range from 4000 to 4999.
  21  */
  22 #define __NR_Linux          4000
  23 #define __NR_syscall        (__NR_Linux +   0)
  24 #define __NR_exit           (__NR_Linux +   1)
  25 #define __NR_fork           (__NR_Linux +   2)
  26 #define __NR_read           (__NR_Linux +   3)
......