Linux Kernel  3.7.1
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syscalls_64.c
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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 
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, &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 
74 long sys_arch_prctl(int code, unsigned long addr)
75 {
76  return arch_prctl(current, code, (unsigned long __user *) addr);
77 }
78 
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 }