kgraft_patcher.c

/*
 * kgraft_patcher -- just kick the kGraft infrastructure for test
 *
 * We patch two (arbitrarily chosen) functions at once...
 *
 *  Copyright (c) 2013-2014 SUSE
 *   Authors: Jiri Kosina
 *	      Vojtech Pavlik
 *	      Jiri Slaby
 */

/*
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/kgraft.h>
#include <linux/kallsyms.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/capability.h>
#include <linux/ptrace.h>

#include <asm/processor.h>

/*
 * This all should be autogenerated from the patched sources
 */

asmlinkage long kgr_new_sys_iopl(unsigned int level)
{
	struct pt_regs *regs = current_pt_regs();
	unsigned int old = (regs->flags >> 12) & 3;
	struct thread_struct *t = &current->thread;

	printk(KERN_DEBUG "kgr-patcher: this is a new sys_iopl()\n");

	if (level > 3)
		return -EINVAL;
	/* Trying to gain more privileges? */
	if (level > old) {
		if (!capable(CAP_SYS_RAWIO))
			return -EPERM;
	}
	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12);
	t->iopl = level << 12;
	set_iopl_mask(t->iopl);

	return 0;
}
KGR_PATCHED_FUNCTION(SyS_iopl, kgr_new_sys_iopl, true);

static bool new_capable(int cap)
{
	printk(KERN_DEBUG "kgr-patcher: this is a new capable()\n");

	return ns_capable(&init_user_ns, cap);
}
KGR_PATCHED_FUNCTION(capable, new_capable, true);

static void new_function(unsigned long data)
{
	pr_info("kgr-patcher: %s\n", __func__);
}
KGR_PATCHED_FUNCTION(unknown_function, new_function, false);

static struct kgr_patch patch = {
	.patches = {
		KGR_PATCH(SyS_iopl),
		KGR_PATCH(capable),
		KGR_PATCH(unknown_function),
		KGR_PATCH_END
	}
};

static int __init kgr_patcher_init(void)
{
	/* removing not supported */
	__module_get(THIS_MODULE);
	kgr_start_patching(&patch);
	return 0;
}

static void __exit kgr_patcher_cleanup(void)
{
	/* extra care needs to be taken when freeing ftrace_ops->private */
	pr_err("removing now buggy!\n");
}

module_init(kgr_patcher_init);
module_exit(kgr_patcher_cleanup);

MODULE_LICENSE("GPL");