287 lines
6.4 KiB
C
287 lines
6.4 KiB
C
/*
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* linux/arch/arm/lib/uaccess_with_memcpy.c
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*
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* Written by: Lennert Buytenhek and Nicolas Pitre
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* Copyright (C) 2009 Marvell Semiconductor
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/kernel.h>
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#include <linux/ctype.h>
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#include <linux/uaccess.h>
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#include <linux/rwsem.h>
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/hardirq.h> /* for in_atomic() */
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#include <linux/gfp.h>
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#include <linux/highmem.h>
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#include <linux/hugetlb.h>
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#include <asm/current.h>
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#include <asm/page.h>
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static int
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pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp)
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{
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unsigned long addr = (unsigned long)_addr;
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pgd_t *pgd;
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pmd_t *pmd;
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pte_t *pte;
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pud_t *pud;
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spinlock_t *ptl;
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pgd = pgd_offset(current->mm, addr);
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if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd)))
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return 0;
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pud = pud_offset(pgd, addr);
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if (unlikely(pud_none(*pud) || pud_bad(*pud)))
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return 0;
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pmd = pmd_offset(pud, addr);
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if (unlikely(pmd_none(*pmd)))
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return 0;
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/*
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* A pmd can be bad if it refers to a HugeTLB or THP page.
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*
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* Both THP and HugeTLB pages have the same pmd layout
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* and should not be manipulated by the pte functions.
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*
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* Lock the page table for the destination and check
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* to see that it's still huge and whether or not we will
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* need to fault on write.
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*/
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if (unlikely(pmd_thp_or_huge(*pmd))) {
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ptl = ¤t->mm->page_table_lock;
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spin_lock(ptl);
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if (unlikely(!pmd_thp_or_huge(*pmd)
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|| pmd_hugewillfault(*pmd))) {
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spin_unlock(ptl);
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return 0;
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}
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*ptep = NULL;
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*ptlp = ptl;
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return 1;
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}
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if (unlikely(pmd_bad(*pmd)))
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return 0;
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pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl);
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if (unlikely(!pte_present(*pte) || !pte_young(*pte) ||
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!pte_write(*pte) || !pte_dirty(*pte))) {
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pte_unmap_unlock(pte, ptl);
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return 0;
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}
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*ptep = pte;
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*ptlp = ptl;
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return 1;
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}
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static unsigned long noinline
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__copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
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{
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unsigned long ua_flags;
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int atomic;
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if (uaccess_kernel()) {
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memcpy((void *)to, from, n);
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return 0;
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}
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/* the mmap semaphore is taken only if not in an atomic context */
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atomic = faulthandler_disabled();
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if (!atomic)
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down_read(¤t->mm->mmap_sem);
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while (n) {
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pte_t *pte;
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spinlock_t *ptl;
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int tocopy;
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while (!pin_page_for_write(to, &pte, &ptl)) {
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if (!atomic)
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up_read(¤t->mm->mmap_sem);
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if (__put_user(0, (char __user *)to))
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goto out;
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if (!atomic)
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down_read(¤t->mm->mmap_sem);
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}
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tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1;
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if (tocopy > n)
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tocopy = n;
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ua_flags = uaccess_save_and_enable();
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memcpy((void *)to, from, tocopy);
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uaccess_restore(ua_flags);
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to += tocopy;
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from += tocopy;
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n -= tocopy;
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if (pte)
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pte_unmap_unlock(pte, ptl);
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else
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spin_unlock(ptl);
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}
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if (!atomic)
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up_read(¤t->mm->mmap_sem);
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out:
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return n;
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}
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unsigned long
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arm_copy_to_user(void __user *to, const void *from, unsigned long n)
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{
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/*
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* This test is stubbed out of the main function above to keep
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* the overhead for small copies low by avoiding a large
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* register dump on the stack just to reload them right away.
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* With frame pointer disabled, tail call optimization kicks in
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* as well making this test almost invisible.
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*/
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if (n < 64) {
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unsigned long ua_flags = uaccess_save_and_enable();
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n = __copy_to_user_std(to, from, n);
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uaccess_restore(ua_flags);
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} else {
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n = __copy_to_user_memcpy(to, from, n);
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}
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return n;
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}
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static unsigned long noinline
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__clear_user_memset(void __user *addr, unsigned long n)
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{
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unsigned long ua_flags;
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if (uaccess_kernel()) {
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memset((void *)addr, 0, n);
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return 0;
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}
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down_read(¤t->mm->mmap_sem);
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while (n) {
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pte_t *pte;
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spinlock_t *ptl;
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int tocopy;
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while (!pin_page_for_write(addr, &pte, &ptl)) {
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up_read(¤t->mm->mmap_sem);
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if (__put_user(0, (char __user *)addr))
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goto out;
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down_read(¤t->mm->mmap_sem);
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}
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tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1;
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if (tocopy > n)
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tocopy = n;
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ua_flags = uaccess_save_and_enable();
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memset((void *)addr, 0, tocopy);
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uaccess_restore(ua_flags);
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addr += tocopy;
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n -= tocopy;
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if (pte)
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pte_unmap_unlock(pte, ptl);
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else
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spin_unlock(ptl);
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}
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up_read(¤t->mm->mmap_sem);
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out:
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return n;
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}
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unsigned long arm_clear_user(void __user *addr, unsigned long n)
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{
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/* See rational for this in __copy_to_user() above. */
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if (n < 64) {
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unsigned long ua_flags = uaccess_save_and_enable();
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n = __clear_user_std(addr, n);
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uaccess_restore(ua_flags);
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} else {
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n = __clear_user_memset(addr, n);
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}
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return n;
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}
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#if 0
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/*
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* This code is disabled by default, but kept around in case the chosen
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* thresholds need to be revalidated. Some overhead (small but still)
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* would be implied by a runtime determined variable threshold, and
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* so far the measurement on concerned targets didn't show a worthwhile
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* variation.
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*
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* Note that a fairly precise sched_clock() implementation is needed
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* for results to make some sense.
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*/
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#include <linux/vmalloc.h>
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static int __init test_size_treshold(void)
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{
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struct page *src_page, *dst_page;
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void *user_ptr, *kernel_ptr;
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unsigned long long t0, t1, t2;
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int size, ret;
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ret = -ENOMEM;
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src_page = alloc_page(GFP_KERNEL);
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if (!src_page)
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goto no_src;
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dst_page = alloc_page(GFP_KERNEL);
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if (!dst_page)
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goto no_dst;
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kernel_ptr = page_address(src_page);
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user_ptr = vmap(&dst_page, 1, VM_IOREMAP, __pgprot(__P010));
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if (!user_ptr)
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goto no_vmap;
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/* warm up the src page dcache */
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ret = __copy_to_user_memcpy(user_ptr, kernel_ptr, PAGE_SIZE);
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for (size = PAGE_SIZE; size >= 4; size /= 2) {
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t0 = sched_clock();
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ret |= __copy_to_user_memcpy(user_ptr, kernel_ptr, size);
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t1 = sched_clock();
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ret |= __copy_to_user_std(user_ptr, kernel_ptr, size);
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t2 = sched_clock();
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printk("copy_to_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
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}
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for (size = PAGE_SIZE; size >= 4; size /= 2) {
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t0 = sched_clock();
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ret |= __clear_user_memset(user_ptr, size);
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t1 = sched_clock();
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ret |= __clear_user_std(user_ptr, size);
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t2 = sched_clock();
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printk("clear_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
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}
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if (ret)
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ret = -EFAULT;
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vunmap(user_ptr);
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no_vmap:
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put_page(dst_page);
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no_dst:
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put_page(src_page);
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no_src:
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return ret;
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}
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subsys_initcall(test_size_treshold);
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#endif
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