| ...)来做到。但要小心，访问完系统调用的参数后，一定要恢复FS。下面是一段例子：
filename内核空间；比如说我们刚创建了一个字串
unsigned long old_fs_value=get_fs();
set_fs(get_ds); /*完成之后就可以存取用户空间了*/
open(filename, O_CREAT|O_RDWR|O_EXCL, 0640);
set_fs(old_fs_value); /*恢复 fs ...*/
三．在module里实现sys_call_table地址查找的代码实现
主要代码如下：
/*实现系统调用*/
unsigned long errno;
#define __syscall_return(type, res) \
do { \
if ((unsigned long)(res) >= (unsigned long)(-125)) { \
errno = -(res); \
res = -1; \
} \
return (type) (res); \
} while (0)
#define _syscall1(type,name,type1,arg1) \
type name(type1 arg1) \
{ \
long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
: "0" (__NR_##name),"b" ((long)(arg1))); \
__syscall_return(type,__res); \
}
#define _syscall3(type,name,type1,arg1,type2,arg2,type3,arg3) \
type name(type1 arg1,type2 arg2,type3 arg3) \
{ \
long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
: "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \
"d" ((long)(arg3))); \
__syscall_return(type,__res); \
}
static inline _syscall3(int,write,int,fd,const char *,buf,off_t,count)
static inline _syscall3(int,read,int,fd,char *,buf,off_t,count)
static inline _syscall3(off_t,lseek,int,fd,off_t,offset,int,count)
static inline _syscall3(int,open,const char *,file,int,flag,int,mode)
static inline _syscall1(int,close,int,fd)
/*从这里以后就可以使用这几个系统调用了*/
struct {
unsigned short limit;
unsigned int base;
} __attribute__ ((packed)) idtr;
struct {
unsigned short off1;
unsigned short sel;
unsigned char none,flags;
unsigned short off2;
} __attribute__ ((packed)) idt;
int kmem;
void readkmem (void *m,unsigned off,int sz)
{
mm_segment_t old_fs_value=get_fs();
set_fs(get_ds());
if (lseek(kmem,off,0)!=off) {
printk("kmem lseek error in read\n"); return;
}
if (read(kmem,m,sz)!=sz) {
printk("kmem read error!\n"); return;
}
set_fs(old_fs_value);
}
#define CALLOFF 100 /* 我们将读出int $0x80的头100个字节 */
/*得到sys_call_table的地址*/
unsigned getscTable()
{
unsigned sct;
unsigned sys_call_off;
char sc_asm[CALLOFF],*p;
/* 获得IDTR寄存器的值 */
asm ("sidt %0" : "=m" (idtr));
mm_segment_t old_fs_value=get_fs();
const char *filename="/dev/kmem"; 上一页 [1] [2] [3] 下一页 | 
