/*
 * linux/kernel/seccomp.c
 *
 * Copyright 2004-2005  Andrea Arcangeli <andrea@cpushare.com>
 * Copyright (C) 2011 The Chromium OS Authors <chromium-os-dev@chromium.org>
 *
 * This defines a simple but solid secure-computing mode.
 */

#include <linux/seccomp.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/compat.h>
#include <linux/unistd.h>
#include <linux/ftrace_event.h>

#define SECCOMP_MAX_FILTER_LENGTH MAX_FILTER_STR_VAL
/* #define SECCOMP_DEBUG 1 */

/*
 * Secure computing mode 1 allows only read/write/exit/sigreturn.
 * To be fully secure this must be combined with rlimit
 * to limit the stack allocations too.
 */
static int mode1_syscalls[] = {
	__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
	0, /* null terminated */
};

#ifdef CONFIG_COMPAT
static int mode1_syscalls_32[] = {
	__NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
	0, /* null terminated */
};
#endif

void __secure_computing(int this_syscall)
{
	int * syscall;

	switch (current->seccomp.mode) {
	case 1:
		syscall = mode1_syscalls;
#ifdef CONFIG_COMPAT
		if (is_compat_task())
			syscall = mode1_syscalls_32;
#endif
		do {
			if (*syscall == this_syscall)
				return;
		} while (*++syscall);
		break;
#ifdef CONFIG_SECCOMP_FILTER
	case 13:
		if (this_syscall >= NR_syscalls || this_syscall < 0)
			break;

		if (!seccomp_test_filters(this_syscall))
			return;

		seccomp_filter_log_failure(this_syscall);
		break;
#endif
	default:
		BUG();
	}

#ifdef SECCOMP_DEBUG
	dump_stack();
#endif
	do_exit(SIGKILL);
}

long prctl_get_seccomp(void)
{
	return current->seccomp.mode;
}

long prctl_set_seccomp(unsigned long seccomp_mode)
{
	long ret;

	/* can set it only once to be even more secure */
	ret = -EPERM;
	if (unlikely(current->seccomp.mode))
		goto out;

	ret = 0;
	switch (seccomp_mode) {
	case 1:
#ifdef TIF_NOTSC
		disable_TSC();
#endif
#ifdef CONFIG_SECCOMP_FILTER
	case 13:
#endif
		current->seccomp.mode = seccomp_mode;
		set_thread_flag(TIF_SECCOMP);
		break;
	default:
		ret = -EINVAL;
	}

out:
	return ret;
}