![Russell King](/assets/img/avatar_default.png)
fuse does not work on ARM due to cache incoherency issues - fuse wants to use get_user_pages() to copy data from the current process into kernel space. However, since this accesses userspace via the kernel mapping, the kernel mapping can be out of date wrt data written to userspace. This can lead to unpredictable behaviour (in the case of fuse) or data corruption for direct-IO. This resolves debian bug #402876 Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
244 lines
6.4 KiB
C
244 lines
6.4 KiB
C
/*
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* linux/arch/arm/mm/flush.c
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*
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* Copyright (C) 1995-2002 Russell King
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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/module.h>
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#include <linux/mm.h>
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#include <linux/pagemap.h>
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#include <asm/cacheflush.h>
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#include <asm/system.h>
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#include <asm/tlbflush.h>
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#include "mm.h"
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#ifdef CONFIG_CPU_CACHE_VIPT
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#define ALIAS_FLUSH_START 0xffff4000
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static void flush_pfn_alias(unsigned long pfn, unsigned long vaddr)
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{
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unsigned long to = ALIAS_FLUSH_START + (CACHE_COLOUR(vaddr) << PAGE_SHIFT);
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const int zero = 0;
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set_pte_ext(TOP_PTE(to), pfn_pte(pfn, PAGE_KERNEL), 0);
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flush_tlb_kernel_page(to);
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asm( "mcrr p15, 0, %1, %0, c14\n"
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" mcr p15, 0, %2, c7, c10, 4\n"
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" mcr p15, 0, %2, c7, c5, 0\n"
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:
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: "r" (to), "r" (to + PAGE_SIZE - L1_CACHE_BYTES), "r" (zero)
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: "cc");
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}
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void flush_cache_mm(struct mm_struct *mm)
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{
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if (cache_is_vivt()) {
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if (cpu_isset(smp_processor_id(), mm->cpu_vm_mask))
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__cpuc_flush_user_all();
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return;
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}
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if (cache_is_vipt_aliasing()) {
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asm( "mcr p15, 0, %0, c7, c14, 0\n"
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" mcr p15, 0, %0, c7, c5, 0\n"
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" mcr p15, 0, %0, c7, c10, 4"
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:
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: "r" (0)
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: "cc");
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}
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}
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void flush_cache_range(struct vm_area_struct *vma, unsigned long start, unsigned long end)
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{
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if (cache_is_vivt()) {
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if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask))
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__cpuc_flush_user_range(start & PAGE_MASK, PAGE_ALIGN(end),
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vma->vm_flags);
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return;
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}
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if (cache_is_vipt_aliasing()) {
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asm( "mcr p15, 0, %0, c7, c14, 0\n"
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" mcr p15, 0, %0, c7, c5, 0\n"
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" mcr p15, 0, %0, c7, c10, 4"
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:
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: "r" (0)
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: "cc");
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}
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}
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void flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr, unsigned long pfn)
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{
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if (cache_is_vivt()) {
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if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask)) {
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unsigned long addr = user_addr & PAGE_MASK;
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__cpuc_flush_user_range(addr, addr + PAGE_SIZE, vma->vm_flags);
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}
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return;
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}
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if (cache_is_vipt_aliasing())
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flush_pfn_alias(pfn, user_addr);
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}
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void flush_ptrace_access(struct vm_area_struct *vma, struct page *page,
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unsigned long uaddr, void *kaddr,
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unsigned long len, int write)
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{
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if (cache_is_vivt()) {
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if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask)) {
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unsigned long addr = (unsigned long)kaddr;
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__cpuc_coherent_kern_range(addr, addr + len);
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}
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return;
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}
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if (cache_is_vipt_aliasing()) {
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flush_pfn_alias(page_to_pfn(page), uaddr);
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return;
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}
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/* VIPT non-aliasing cache */
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if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask) &&
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vma->vm_flags & VM_EXEC) {
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unsigned long addr = (unsigned long)kaddr;
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/* only flushing the kernel mapping on non-aliasing VIPT */
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__cpuc_coherent_kern_range(addr, addr + len);
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}
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}
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#else
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#define flush_pfn_alias(pfn,vaddr) do { } while (0)
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#endif
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void __flush_dcache_page(struct address_space *mapping, struct page *page)
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{
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/*
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* Writeback any data associated with the kernel mapping of this
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* page. This ensures that data in the physical page is mutually
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* coherent with the kernels mapping.
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*/
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__cpuc_flush_dcache_page(page_address(page));
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/*
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* If this is a page cache page, and we have an aliasing VIPT cache,
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* we only need to do one flush - which would be at the relevant
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* userspace colour, which is congruent with page->index.
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*/
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if (mapping && cache_is_vipt_aliasing())
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flush_pfn_alias(page_to_pfn(page),
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page->index << PAGE_CACHE_SHIFT);
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}
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static void __flush_dcache_aliases(struct address_space *mapping, struct page *page)
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{
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struct mm_struct *mm = current->active_mm;
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struct vm_area_struct *mpnt;
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struct prio_tree_iter iter;
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pgoff_t pgoff;
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/*
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* There are possible user space mappings of this page:
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* - VIVT cache: we need to also write back and invalidate all user
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* data in the current VM view associated with this page.
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* - aliasing VIPT: we only need to find one mapping of this page.
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*/
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pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
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flush_dcache_mmap_lock(mapping);
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vma_prio_tree_foreach(mpnt, &iter, &mapping->i_mmap, pgoff, pgoff) {
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unsigned long offset;
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/*
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* If this VMA is not in our MM, we can ignore it.
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*/
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if (mpnt->vm_mm != mm)
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continue;
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if (!(mpnt->vm_flags & VM_MAYSHARE))
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continue;
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offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
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flush_cache_page(mpnt, mpnt->vm_start + offset, page_to_pfn(page));
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}
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flush_dcache_mmap_unlock(mapping);
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}
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/*
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* Ensure cache coherency between kernel mapping and userspace mapping
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* of this page.
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*
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* We have three cases to consider:
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* - VIPT non-aliasing cache: fully coherent so nothing required.
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* - VIVT: fully aliasing, so we need to handle every alias in our
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* current VM view.
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* - VIPT aliasing: need to handle one alias in our current VM view.
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*
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* If we need to handle aliasing:
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* If the page only exists in the page cache and there are no user
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* space mappings, we can be lazy and remember that we may have dirty
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* kernel cache lines for later. Otherwise, we assume we have
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* aliasing mappings.
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*
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* Note that we disable the lazy flush for SMP.
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*/
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void flush_dcache_page(struct page *page)
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{
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struct address_space *mapping = page_mapping(page);
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#ifndef CONFIG_SMP
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if (mapping && !mapping_mapped(mapping))
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set_bit(PG_dcache_dirty, &page->flags);
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else
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#endif
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{
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__flush_dcache_page(mapping, page);
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if (mapping && cache_is_vivt())
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__flush_dcache_aliases(mapping, page);
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}
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}
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EXPORT_SYMBOL(flush_dcache_page);
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/*
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* Flush an anonymous page so that users of get_user_pages()
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* can safely access the data. The expected sequence is:
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*
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* get_user_pages()
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* -> flush_anon_page
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* memcpy() to/from page
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* if written to page, flush_dcache_page()
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*/
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void __flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
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{
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unsigned long pfn;
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/* VIPT non-aliasing caches need do nothing */
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if (cache_is_vipt_nonaliasing())
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return;
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/*
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* Write back and invalidate userspace mapping.
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*/
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pfn = page_to_pfn(page);
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if (cache_is_vivt()) {
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flush_cache_page(vma, vmaddr, pfn);
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} else {
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/*
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* For aliasing VIPT, we can flush an alias of the
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* userspace address only.
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*/
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flush_pfn_alias(pfn, vmaddr);
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}
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/*
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* Invalidate kernel mapping. No data should be contained
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* in this mapping of the page. FIXME: this is overkill
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* since we actually ask for a write-back and invalidate.
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*/
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__cpuc_flush_dcache_page(page_address(page));
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}
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