system calls undefined! Compiling kernel module

Question

I am new to kernel module programming, and trying to create raw socket in my kernel module using 'sys_socket'. I am binding this socket to an interface using 'sys_bind' and 'sys_ioctl' (for fetching interface number).

While compiling my module, I get the following errors:

make -C /lib/modules/3.13.0-68-generic/build M=/root/Kernel_Module modules
make[1]: Entering directory `/usr/src/linux-headers-3.13.0-68-generic'
CC [M]  /root/Kernel_Module/kernel_module.o
Building modules, stage 2.
MODPOST 1 modules
WARNING: "sys_ioctl" [/root/Kernel_Module/kernel_module.ko] undefined!
WARNING: "sys_bind" [/root/Kernel_Module/kernel_module.ko] undefined!
WARNING: "sys_socket" [/root/Kernel_Module/kernel_module.ko] undefined!
CC      /root/Kernel_Module/kernel_module.mod.o
LD [M]  /root/Kernel_Module/kernel_module.ko
make[1]: Leaving directory `/usr/src/linux-headers-3.13.0-68-generic'

How can I resolve this issue?

The code is specified below:

struct sockaddr_ll socketBindAddr;
struct ifreq       ifreq;
int                socketFd = 0;

socketFd = sys_socket (AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
if (socketFd < 0)
{
    printk (KERN_CRIT "Failed to open data socket!!\r\n");
    return OFC_FAILURE;
}

memset (&ifreq, 0, sizeof(ifreq));
strcpy (ifreq.ifr_name, gOfcGlobals.aDataIfName);
if (sys_ioctl (socketFd, SIOCGIFINDEX, (unsigned long) &ifreq) < 0)
{
    printk (KERN_CRIT "Ioctl failed to get IfIndex!!\r\n");
    return OFC_FAILURE;
}

memset (&socketBindAddr, 0, sizeof(socketBindAddr));
socketBindAddr.sll_family = AF_PACKET;
socketBindAddr.sll_protocol = htons(ETH_P_ALL);
if (sys_bind (socketFd, (struct sockaddr *) &socketBindAddr,
    sizeof(socketBindAddr)) < 0)
{
    printk (KERN_CRIT "Failed to bind socket\r\n");
    return OFC_FAILURE;
}

In short: Syscalls are for user-space programs, not for kernel modules. Some syscalls have analogues for in-kernel use. I don't know about in-kernel analogues for ioctl, bind and socket. — Tsyvarev
– Tsyvarev, Commented Oct 3, 2016 at 17:11

Toby Speight · Accepted Answer · 2016-10-03 17:19:23Z

1

sys_bind() and sys_ioctl (and sys_socket) are the (low-level) user-space interface to the kernel. You haven't shown us the code you've written, but you'll need to use a more suitable kernel-internal interface for your net access.

answered Oct 3, 2016 at 17:19

Toby Speight

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3 Comments

user2522685 Over a year ago

Added code. Kindly suggest if a procedure to create sockets using kernel module.

Toby Speight Over a year ago

Sorry, I've never done high-level networking in a kernel module. I had a look at NFS to see how it opens connections, but got lost - perhaps NBD is a simpler starting point? Try reading /drivers/block/nbd.c, perhaps.

user2522685 Over a year ago

Sockets can be created in the kernel using the following functions: sock_create() /* Create Socket / sock->ops->bind () / Bind Socket / sock->ops->release () / Close Socket */ struct socket is the structure for sockets in kernel, instead of file descriptors in user space.

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