Hello,
I tryed figure out how to read a file from a LKM, i
done like this:
At init_module
int init_module(void){
or_open=sys_call_table[__NR_open];
or_read=sys_call_table[__NR_read];
or_close=sys_call_table[__NR_close];
return(0);
}
So the code in a function that need to read a file:
char tmp[512];
char buff[1024];
int ret, size;
mm_segment_t old_fs;
memset(tmp, 0, sizeof(tmp));
strcpy(tmp, "/tmp/myfile.txt");
//old_fs = get_fs();
//set_fs(get_ds());
ret = (*or_open) (tmp, O_RDONLY|O_LARGEFILE, 0640);
//set_fs(old_fs);
if ( ret < 0){
printk("\nFailed to open");
return (0);
}
memset(buff, 0, sizeof(buff));
size = (*or_read)(ret, buff, sizeof(buff));
printk("\nContents is %s", buff);
(*or_close)(ret);
Well, the problem is if i don't use get_fs() and
set_fs() i always get value ZERO from open! :(
If i use get_fs() and set_fs() then my kernel crash.
What i'm doing wrong ? Can someone give me a example ?
Someone can say that i shouldn't use the read, open,
etc from syscall_table... but i only found this
example in internet, if someone present-me a better
way i will use.
Regards,
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