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
arch_prctl(struct task_struct * task,int code,unsigned long __user * addr)12 long 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, ¤t->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, ¤t->thread.regs.regs);
59 break;
60 case ARCH_SET_GS:
61 ret = save_registers(pid, ¤t->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
sys_arch_prctl(int code,unsigned long addr)74 long sys_arch_prctl(int code, unsigned long addr)
75 {
76 return arch_prctl(current, code, (unsigned long __user *) addr);
77 }
78
arch_switch_to(struct task_struct * to)79 void 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