2 * Copyright (C) 2003 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Copyright 2003 PathScale, Inc.
5 * Licensed under the GPL
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 */
15 long arch_prctl(struct task_struct *task, int option,
16 unsigned long __user *arg2)
18 unsigned long *ptr = arg2, tmp;
20 int pid = task->mm->context.id.u.pid;
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.
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
38 ret = restore_registers(pid, ¤t->thread.regs.regs);
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.
55 ret = os_arch_prctl(pid, option, ptr);
61 current->thread.arch.fs = (unsigned long) ptr;
62 ret = save_registers(pid, ¤t->thread.regs.regs);
65 ret = save_registers(pid, ¤t->thread.regs.regs);
68 ret = put_user(tmp, arg2);
71 ret = put_user(tmp, arg2);
78 SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
80 return arch_prctl(current, option, (unsigned long __user *) arg2);
83 void arch_switch_to(struct task_struct *to)
85 if ((to->thread.arch.fs == 0) || (to->mm == NULL))
88 arch_prctl(to, ARCH_SET_FS, (void __user *) to->thread.arch.fs);