About

This module provides mechanism that allows to hook kernel functions using exception tables.

Usage

Given the kernel function X which has prototype typeof(X) let's see how to hook it:

1. Use DECLARE_KHOOK(X) macro to declare the hook
2. Write hook's body using khook_X function name and typeof(X) as a prototype
3. Use KHOOK_ORIGIN(X, args) macro as a wrapper around the X function call
4. Protect hook's body with KHOOK_USAGE_INC(X) and KHOOK_USAGE_DEC(X)

Example

#include <linux/fs.h> // inode_permission() prototype lives here

DECLARE_KHOOK(inode_permission);
int khook_inode_permission(struct inode * inode, int mode)
{
	int result;

	KHOOK_USAGE_INC(inode_permission);

	debug("%s(%pK,%08x) [%s]\n", __func__, inode, mode, current->comm);

	result = KHOOK_ORIGIN(inode_permission, inode, mode);

	debug("%s(%pK,%08x) [%s] = %d\n", __func__, inode, mode, current->comm, result);

	KHOOK_USAGE_DEC(inode_permission);

	return result;
}

Credits

Written by Ilya V. Matveychikov [email protected], distributed under GPL