1/*
2 * Copyright (C) 2003 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Copyright 2003 PathScale, Inc.
4 *
5 * Licensed under the GPL
6 */
7
8#include <linux/sched.h>
9#include <asm/prctl.h> /* XXX This should get the constants from libc */
10#include <os.h>
11
12long arch_prctl(struct task_struct *task, int code, unsigned long __user *addr)
13{
14	unsigned long *ptr = addr, tmp;
15	long ret;
16	int pid = task->mm->context.id.u.pid;
17
18	/*
19	 * With ARCH_SET_FS (and ARCH_SET_GS is treated similarly to
20	 * be safe), we need to call arch_prctl on the host because
21	 * setting %fs may result in something else happening (like a
22	 * GDT or thread.fs being set instead).  So, we let the host
23	 * fiddle the registers and thread struct and restore the
24	 * registers afterwards.
25	 *
26	 * So, the saved registers are stored to the process (this
27	 * needed because a stub may have been the last thing to run),
28	 * arch_prctl is run on the host, then the registers are read
29	 * back.
30	 */
31	switch (code) {
32	case ARCH_SET_FS:
33	case ARCH_SET_GS:
34		ret = restore_registers(pid, &current->thread.regs.regs);
35		if (ret)
36			return ret;
37		break;
38	case ARCH_GET_FS:
39	case ARCH_GET_GS:
40		/*
41		 * With these two, we read to a local pointer and
42		 * put_user it to the userspace pointer that we were
43		 * given.  If addr isn't valid (because it hasn't been
44		 * faulted in or is just bogus), we want put_user to
45		 * fault it in (or return -EFAULT) instead of having
46		 * the host return -EFAULT.
47		 */
48		ptr = &tmp;
49	}
50
51	ret = os_arch_prctl(pid, code, ptr);
52	if (ret)
53		return ret;
54
55	switch (code) {
56	case ARCH_SET_FS:
57		current->thread.arch.fs = (unsigned long) ptr;
58		ret = save_registers(pid, &current->thread.regs.regs);
59		break;
60	case ARCH_SET_GS:
61		ret = save_registers(pid, &current->thread.regs.regs);
62		break;
63	case ARCH_GET_FS:
64		ret = put_user(tmp, addr);
65		break;
66	case ARCH_GET_GS:
67		ret = put_user(tmp, addr);
68		break;
69	}
70
71	return ret;
72}
73
74long sys_arch_prctl(int code, unsigned long addr)
75{
76	return arch_prctl(current, code, (unsigned long __user *) addr);
77}
78
79void arch_switch_to(struct task_struct *to)
80{
81	if ((to->thread.arch.fs == 0) || (to->mm == NULL))
82		return;
83
84	arch_prctl(to, ARCH_SET_FS, (void __user *) to->thread.arch.fs);
85}
86