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