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