arch/x86/um/syscalls_64.c

   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
  13 long 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
  75 long sys_arch_prctl(int code, unsigned long addr)
  76 {
  77         return arch_prctl(current, code, (unsigned long __user *) addr);
  78 }
  79
  80 void 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 }