arch/powerpc/lib/vmx-helper.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify
   3  * it under the terms of the GNU General Public License as published by
   4  * the Free Software Foundation; either version 2 of the License, or
   5  * (at your option) any later version.
   6  *
   7  * This program is distributed in the hope that it will be useful,
   8  * but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  * GNU General Public License for more details.
  11  *
  12  * You should have received a copy of the GNU General Public License
  13  * along with this program; if not, write to the Free Software
  14  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  15  *
  16  * Copyright (C) IBM Corporation, 2011
  17  *
  18  * Authors: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
  19  *          Anton Blanchard <anton@au.ibm.com>
  20  */
  21 #include <linux/uaccess.h>
  22 #include <linux/hardirq.h>
  23 #include <asm/switch_to.h>
  24
  25 int enter_vmx_usercopy(void)
  26 {
  27         if (in_interrupt())
  28                 return 0;
  29
  30         /* This acts as preempt_disable() as well and will make
  31          * enable_kernel_altivec(). We need to disable page faults
  32          * as they can call schedule and thus make us lose the VMX
  33          * context. So on page faults, we just fail which will cause
  34          * a fallback to the normal non-vmx copy.
  35          */
  36         pagefault_disable();
  37
  38         enable_kernel_altivec();
  39
  40         return 1;
  41 }
  42
  43 /*
  44  * This function must return 0 because we tail call optimise when calling
  45  * from __copy_tofrom_user_power7 which returns 0 on success.
  46  */
  47 int exit_vmx_usercopy(void)
  48 {
  49         pagefault_enable();
  50         return 0;
  51 }
  52
  53 int enter_vmx_copy(void)
  54 {
  55         if (in_interrupt())
  56                 return 0;
  57
  58         preempt_disable();
  59
  60         enable_kernel_altivec();
  61
  62         return 1;
  63 }
  64
  65 /*
  66  * All calls to this function will be optimised into tail calls. We are
  67  * passed a pointer to the destination which we return as required by a
  68  * memcpy implementation.
  69  */
  70 void *exit_vmx_copy(void *dest)
  71 {
  72         preempt_enable();
  73         return dest;
  74 }