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 <linux/sched/mm.h>
10 #include <linux/syscalls.h>
11 #include <linux/uaccess.h>
12 #include <asm/prctl.h> /* XXX This should get the constants from libc */
13 #include <os.h>
14
arch_prctl(struct task_struct * task,int option,unsigned long __user * arg2)15 long arch_prctl(struct task_struct *task, int option,
16 unsigned long __user *arg2)
17 {
18 unsigned long *ptr = arg2, tmp;
19 long ret;
20 int pid = task->mm->context.id.u.pid;
21
22 /*
23 * With ARCH_SET_FS (and ARCH_SET_GS is treated similarly to
24 * be safe), we need to call arch_prctl on the host because
25 * setting %fs may result in something else happening (like a
26 * GDT or thread.fs being set instead). So, we let the host
27 * fiddle the registers and thread struct and restore the
28 * registers afterwards.
29 *
30 * So, the saved registers are stored to the process (this
31 * needed because a stub may have been the last thing to run),
32 * arch_prctl is run on the host, then the registers are read
33 * back.
34 */
35 switch (option) {
36 case ARCH_SET_FS:
37 case ARCH_SET_GS:
38 ret = restore_registers(pid, ¤t->thread.regs.regs);
39 if (ret)
40 return ret;
41 break;
42 case ARCH_GET_FS:
43 case ARCH_GET_GS:
44 /*
45 * With these two, we read to a local pointer and
46 * put_user it to the userspace pointer that we were
47 * given. If addr isn't valid (because it hasn't been
48 * faulted in or is just bogus), we want put_user to
49 * fault it in (or return -EFAULT) instead of having
50 * the host return -EFAULT.
51 */
52 ptr = &tmp;
53 }
54
55 ret = os_arch_prctl(pid, option, ptr);
56 if (ret)
57 return ret;
58
59 switch (option) {
60 case ARCH_SET_FS:
61 current->thread.arch.fs = (unsigned long) ptr;
62 ret = save_registers(pid, ¤t->thread.regs.regs);
63 break;
64 case ARCH_SET_GS:
65 ret = save_registers(pid, ¤t->thread.regs.regs);
66 break;
67 case ARCH_GET_FS:
68 ret = put_user(tmp, arg2);
69 break;
70 case ARCH_GET_GS:
71 ret = put_user(tmp, arg2);
72 break;
73 }
74
75 return ret;
76 }
77
SYSCALL_DEFINE2(arch_prctl,int,option,unsigned long,arg2)78 SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
79 {
80 return arch_prctl(current, option, (unsigned long __user *) arg2);
81 }
82
arch_switch_to(struct task_struct * to)83 void arch_switch_to(struct task_struct *to)
84 {
85 if ((to->thread.arch.fs == 0) || (to->mm == NULL))
86 return;
87
88 arch_prctl(to, ARCH_SET_FS, (void __user *) to->thread.arch.fs);
89 }
90