获取Linux 2.6.x sys_call_table

在linux中所有的syscall都是调用int 0x80, int 0x80的中断服务程序为system_call(arch/x86/kernel/traps_32.c:set_system_gate(SYSCALL_VECTOR,&system_call).  system_call (arch/x86/entry_32.S)最终call *sys_call_table(,%eax,4)来完成一个syscall调用. 
即 int 0x80 -> system_call -> sys_call_table, 这样我们只要首先获取int 0x80的中断服务地址system_call地址, 然后在system_call代码中直接搜索call指令即可找到sys_call_table地址了!
另一种方法就是直接修改
通过cat /boot/System.map-`uname -r` |grep sys_call_table  查看当前sys_call_table地址,并与通过以上方法取得的地址做比较!
内核版本: ubuntu 2.6.24-19-server
/*
 * Standard in kernel modules
 */
#include <linux/kernel.h>   /* We're doing kernel work */
#include <linux/module.h>   /* Specifically, a module, */
#include <linux/moduleparam.h>  /* which will have params */
#include <linux/unistd.h>   /* The list of system calls */
/*
 * For the current (process) structure, we need
 * this to know who the current user is.
 */
#include <linux/sched.h>
#include <asm/uaccess.h>
unsigned long *sys_call_table = 0;
//EXPORT_SYMBOL ( sys_call_table );
struct {
    unsigned short  limit;
    unsigned int    base;
} __attribute__ ( ( packed ) ) idtr;
struct {
    unsigned short  offset_low;
    unsigned short  segment_select;
    unsigned char   reserved,   flags;
    unsigned short  offset_high;
} __attribute__ ( ( packed ) ) * idt;
unsigned long* find_sys_call_table(void)
{
    unsigned long system_call = 0;          // x80中断处理程序system_call 地址
    char *call_hex = "\xff\x14\x85";    // call 指令
    char *code_ptr = NULL;