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 #include <registers.h>
15
arch_prctl(struct task_struct * task,int option,unsigned long __user * arg2)16 long arch_prctl(struct task_struct *task, int option,
17 unsigned long __user *arg2)
18 {
19 unsigned long *ptr = arg2, tmp;
20 long ret;
21 int pid = task->mm->context.id.u.pid;
22
23 /*
24 * With ARCH_SET_FS (and ARCH_SET_GS is treated similarly to
25 * be safe), we need to call arch_prctl on the host because
26 * setting %fs may result in something else happening (like a
27 * GDT or thread.fs being set instead). So, we let the host
28 * fiddle the registers and thread struct and restore the
29 * registers afterwards.
30 *
31 * So, the saved registers are stored to the process (this
32 * needed because a stub may have been the last thing to run),
33 * arch_prctl is run on the host, then the registers are read
34 * back.
35 */
36 switch (option) {
37 case ARCH_SET_FS:
38 case ARCH_SET_GS:
39 ret = restore_pid_registers(pid, ¤t->thread.regs.regs);
40 if (ret)
41 return ret;
42 break;
43 case ARCH_GET_FS:
44 case ARCH_GET_GS:
45 /*
46 * With these two, we read to a local pointer and
47 * put_user it to the userspace pointer that we were
48 * given. If addr isn't valid (because it hasn't been
49 * faulted in or is just bogus), we want put_user to
50 * fault it in (or return -EFAULT) instead of having
51 * the host return -EFAULT.
52 */
53 ptr = &tmp;
54 }
55
56 ret = os_arch_prctl(pid, option, ptr);
57 if (ret)
58 return ret;
59
60 switch (option) {
61 case ARCH_SET_FS:
62 current->thread.arch.fs = (unsigned long) ptr;
63 ret = save_registers(pid, ¤t->thread.regs.regs);
64 break;
65 case ARCH_SET_GS:
66 ret = save_registers(pid, ¤t->thread.regs.regs);
67 break;
68 case ARCH_GET_FS:
69 ret = put_user(tmp, arg2);
70 break;
71 case ARCH_GET_GS:
72 ret = put_user(tmp, arg2);
73 break;
74 }
75
76 return ret;
77 }
78
SYSCALL_DEFINE2(arch_prctl,int,option,unsigned long,arg2)79 SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
80 {
81 return arch_prctl(current, option, (unsigned long __user *) arg2);
82 }
83
arch_switch_to(struct task_struct * to)84 void arch_switch_to(struct task_struct *to)
85 {
86 if ((to->thread.arch.fs == 0) || (to->mm == NULL))
87 return;
88
89 arch_prctl(to, ARCH_SET_FS, (void __user *) to->thread.arch.fs);
90 }
91