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flush.c

/*
 *  linux/arch/arm/mm/flush.c
 *
 *  Copyright (C) 1995-2002 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/pagemap.h>

#include <asm/cacheflush.h>
#include <asm/system.h>
#include <asm/tlbflush.h>

#include "mm.h"

#ifdef CONFIG_CPU_CACHE_VIPT

#define ALIAS_FLUSH_START     0xffff4000

static void flush_pfn_alias(unsigned long pfn, unsigned long vaddr)
{
      unsigned long to = ALIAS_FLUSH_START + (CACHE_COLOUR(vaddr) << PAGE_SHIFT);
      const int zero = 0;

      set_pte_ext(TOP_PTE(to), pfn_pte(pfn, PAGE_KERNEL), 0);
      flush_tlb_kernel_page(to);

      asm(  "mcrr p15, 0, %1, %0, c14\n"
      "     mcr   p15, 0, %2, c7, c10, 4\n"
      "     mcr   p15, 0, %2, c7, c5, 0\n"
          :
          : "r" (to), "r" (to + PAGE_SIZE - L1_CACHE_BYTES), "r" (zero)
          : "cc");
}

void flush_cache_mm(struct mm_struct *mm)
{
      if (cache_is_vivt()) {
            if (cpu_isset(smp_processor_id(), mm->cpu_vm_mask))
                  __cpuc_flush_user_all();
            return;
      }

      if (cache_is_vipt_aliasing()) {
            asm(  "mcr  p15, 0, %0, c7, c14, 0\n"
            "     mcr   p15, 0, %0, c7, c5, 0\n"
            "     mcr   p15, 0, %0, c7, c10, 4"
                :
                : "r" (0)
                : "cc");
      }
}

void flush_cache_range(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
      if (cache_is_vivt()) {
            if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask))
                  __cpuc_flush_user_range(start & PAGE_MASK, PAGE_ALIGN(end),
                                    vma->vm_flags);
            return;
      }

      if (cache_is_vipt_aliasing()) {
            asm(  "mcr  p15, 0, %0, c7, c14, 0\n"
            "     mcr   p15, 0, %0, c7, c5, 0\n"
            "     mcr   p15, 0, %0, c7, c10, 4"
                :
                : "r" (0)
                : "cc");
      }
}

void flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr, unsigned long pfn)
{
      if (cache_is_vivt()) {
            if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask)) {
                  unsigned long addr = user_addr & PAGE_MASK;
                  __cpuc_flush_user_range(addr, addr + PAGE_SIZE, vma->vm_flags);
            }
            return;
      }

      if (cache_is_vipt_aliasing())
            flush_pfn_alias(pfn, user_addr);
}

void flush_ptrace_access(struct vm_area_struct *vma, struct page *page,
                   unsigned long uaddr, void *kaddr,
                   unsigned long len, int write)
{
      if (cache_is_vivt()) {
            if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask)) {
                  unsigned long addr = (unsigned long)kaddr;
                  __cpuc_coherent_kern_range(addr, addr + len);
            }
            return;
      }

      if (cache_is_vipt_aliasing()) {
            flush_pfn_alias(page_to_pfn(page), uaddr);
            return;
      }

      /* VIPT non-aliasing cache */
      if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask) &&
          vma->vm_flags & VM_EXEC) {
            unsigned long addr = (unsigned long)kaddr;
            /* only flushing the kernel mapping on non-aliasing VIPT */
            __cpuc_coherent_kern_range(addr, addr + len);
      }
}
#else
#define flush_pfn_alias(pfn,vaddr)  do { } while (0)
#endif

void __flush_dcache_page(struct address_space *mapping, struct page *page)
{
      /*
       * Writeback any data associated with the kernel mapping of this
       * page.  This ensures that data in the physical page is mutually
       * coherent with the kernels mapping.
       */
      __cpuc_flush_dcache_page(page_address(page));

      /*
       * If this is a page cache page, and we have an aliasing VIPT cache,
       * we only need to do one flush - which would be at the relevant
       * userspace colour, which is congruent with page->index.
       */
      if (mapping && cache_is_vipt_aliasing())
            flush_pfn_alias(page_to_pfn(page),
                        page->index << PAGE_CACHE_SHIFT);
}

static void __flush_dcache_aliases(struct address_space *mapping, struct page *page)
{
      struct mm_struct *mm = current->active_mm;
      struct vm_area_struct *mpnt;
      struct prio_tree_iter iter;
      pgoff_t pgoff;

      /*
       * There are possible user space mappings of this page:
       * - VIVT cache: we need to also write back and invalidate all user
       *   data in the current VM view associated with this page.
       * - aliasing VIPT: we only need to find one mapping of this page.
       */
      pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);

      flush_dcache_mmap_lock(mapping);
      vma_prio_tree_foreach(mpnt, &iter, &mapping->i_mmap, pgoff, pgoff) {
            unsigned long offset;

            /*
             * If this VMA is not in our MM, we can ignore it.
             */
            if (mpnt->vm_mm != mm)
                  continue;
            if (!(mpnt->vm_flags & VM_MAYSHARE))
                  continue;
            offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
            flush_cache_page(mpnt, mpnt->vm_start + offset, page_to_pfn(page));
      }
      flush_dcache_mmap_unlock(mapping);
}

/*
 * Ensure cache coherency between kernel mapping and userspace mapping
 * of this page.
 *
 * We have three cases to consider:
 *  - VIPT non-aliasing cache: fully coherent so nothing required.
 *  - VIVT: fully aliasing, so we need to handle every alias in our
 *          current VM view.
 *  - VIPT aliasing: need to handle one alias in our current VM view.
 *
 * If we need to handle aliasing:
 *  If the page only exists in the page cache and there are no user
 *  space mappings, we can be lazy and remember that we may have dirty
 *  kernel cache lines for later.  Otherwise, we assume we have
 *  aliasing mappings.
 *
 * Note that we disable the lazy flush for SMP.
 */
void flush_dcache_page(struct page *page)
{
      struct address_space *mapping = page_mapping(page);

#ifndef CONFIG_SMP
      if (mapping && !mapping_mapped(mapping))
            set_bit(PG_dcache_dirty, &page->flags);
      else
#endif
      {
            __flush_dcache_page(mapping, page);
            if (mapping && cache_is_vivt())
                  __flush_dcache_aliases(mapping, page);
            else if (mapping)
                  __flush_icache_all();
      }
}
EXPORT_SYMBOL(flush_dcache_page);

/*
 * Flush an anonymous page so that users of get_user_pages()
 * can safely access the data.  The expected sequence is:
 *
 *  get_user_pages()
 *    -> flush_anon_page
 *  memcpy() to/from page
 *  if written to page, flush_dcache_page()
 */
void __flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
{
      unsigned long pfn;

      /* VIPT non-aliasing caches need do nothing */
      if (cache_is_vipt_nonaliasing())
            return;

      /*
       * Write back and invalidate userspace mapping.
       */
      pfn = page_to_pfn(page);
      if (cache_is_vivt()) {
            flush_cache_page(vma, vmaddr, pfn);
      } else {
            /*
             * For aliasing VIPT, we can flush an alias of the
             * userspace address only.
             */
            flush_pfn_alias(pfn, vmaddr);
      }

      /*
       * Invalidate kernel mapping.  No data should be contained
       * in this mapping of the page.  FIXME: this is overkill
       * since we actually ask for a write-back and invalidate.
       */
      __cpuc_flush_dcache_page(page_address(page));
}

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