LXR linux/arch/x86/um/syscalls

   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
  15long 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, &current->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, &current->thread.regs.regs);
  63                break;
  64        case ARCH_SET_GS:
  65                ret = save_registers(pid, &current->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
  78SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
  79{
  80        return arch_prctl(current, option, (unsigned long __user *) arg2);
  81}
  82
  83void 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