linux/arch/powerpc/lib/vmx-helper.c
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   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
  25int 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 */
  47int exit_vmx_usercopy(void)
  48{
  49        pagefault_enable();
  50        return 0;
  51}
  52
  53int 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 */
  70void *exit_vmx_copy(void *dest)
  71{
  72        preempt_enable();
  73        return dest;
  74}
  75