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 #include <asm/asm-prototypes.h>
  25
  26 int enter_vmx_usercopy(void)
  27 {
  28         if (in_interrupt())
  29                 return 0;
  30
  31         preempt_disable();
  32         /*
  33          * We need to disable page faults as they can call schedule and
  34          * thus make us lose the VMX context. So on page faults, we just
  35          * fail which will cause a fallback to the normal non-vmx copy.
  36          */
  37         pagefault_disable();
  38
  39         enable_kernel_altivec();
  40
  41         return 1;
  42 }
  43
  44 /*
  45  * This function must return 0 because we tail call optimise when calling
  46  * from __copy_tofrom_user_power7 which returns 0 on success.
  47  */
  48 int exit_vmx_usercopy(void)
  49 {
  50         disable_kernel_altivec();
  51         pagefault_enable();
  52         preempt_enable();
  53         return 0;
  54 }
  55
  56 int enter_vmx_copy(void)
  57 {
  58         if (in_interrupt())
  59                 return 0;
  60
  61         preempt_disable();
  62
  63         enable_kernel_altivec();
  64
  65         return 1;
  66 }
  67
  68 /*
  69  * All calls to this function will be optimised into tail calls. We are
  70  * passed a pointer to the destination which we return as required by a
  71  * memcpy implementation.
  72  */
  73 void *exit_vmx_copy(void *dest)
  74 {
  75         disable_kernel_altivec();
  76         preempt_enable();
  77         return dest;
  78 }