Hi all,
I am trying to implement a protocol in linux kernel (2.6.14) for
experimental purposes and I am facing a weird problem.
I created a system call; in that code, the data read by copy_from user()
is correct.
rt is a pointer in kernel space and rt_u is a pointer in user space.
asmlinkage int sys_asimcast(struct routing_table *rt_u) {
rt = rt_u;
printk("Kernel has received pointer to routing table(%d);\n", (int)rt);
if (rt != NULL) {
struct routing_table local_rt;
int n = copy_from_user(&local_rt, rt, sizeof(struct routing_table));
printk("rt.session_list = %d; n = %d.\n", (int)local_rt.session_list, n);
}
return 2;
}
Now, I copied the same code in ip_rcv (/net/IPv4/ip_input.c) and the
data which is read is incorrect (the value of pointer rt remains the same);
struct routing_table local_rt;
if (rt != NULL) {
n = get_rt(&local_rt, rt);
printk("local_rt.session_list = %d; n = %d.\n",
(int)local_rt.session_list, n);
}
I am wondering if this problem has to do with the fact that
copy_from_user is user context only? If yes, should I change the context
and how?
Sorry if the question sounds stupid, but I've een struggling with that
issue for a while... :(
Best regards,
-- Laurent
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