arch/arm/mm/fault-armv.c

   1 /*
   2  *  linux/arch/arm/mm/fault-armv.c
   3  *
   4  *  Copyright (C) 1995  Linus Torvalds
   5  *  Modifications for ARM processor (c) 1995-2002 Russell King
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11 #include <linux/module.h>
  12 #include <linux/sched.h>
  13 #include <linux/kernel.h>
  14 #include <linux/mm.h>
  15 #include <linux/bitops.h>
  16 #include <linux/vmalloc.h>
  17 #include <linux/init.h>
  18 #include <linux/pagemap.h>
  19
  20 #include <asm/cacheflush.h>
  21 #include <asm/pgtable.h>
  22 #include <asm/tlbflush.h>
  23
  24 static unsigned long shared_pte_mask = L_PTE_CACHEABLE;
  25
  26 /*
  27  * We take the easy way out of this problem - we make the
  28  * PTE uncacheable.  However, we leave the write buffer on.
  29  *
  30  * Note that the pte lock held when calling update_mmu_cache must also
  31  * guard the pte (somewhere else in the same mm) that we modify here.
  32  * Therefore those configurations which might call adjust_pte (those
  33  * without CONFIG_CPU_CACHE_VIPT) cannot support split page_table_lock.
  34  */
  35 static int adjust_pte(struct vm_area_struct *vma, unsigned long address)
  36 {
  37         pgd_t *pgd;
  38         pmd_t *pmd;
  39         pte_t *pte, entry;
  40         int ret = 0;
  41
  42         pgd = pgd_offset(vma->vm_mm, address);
  43         if (pgd_none(*pgd))
  44                 goto no_pgd;
  45         if (pgd_bad(*pgd))
  46                 goto bad_pgd;
  47
  48         pmd = pmd_offset(pgd, address);
  49         if (pmd_none(*pmd))
  50                 goto no_pmd;
  51         if (pmd_bad(*pmd))
  52                 goto bad_pmd;
  53
  54         pte = pte_offset_map(pmd, address);
  55         entry = *pte;
  56
  57         /*
  58          * If this page isn't present, or is already setup to
  59          * fault (ie, is old), we can safely ignore any issues.
  60          */
  61         if (pte_present(entry) && pte_val(entry) & shared_pte_mask) {
  62                 flush_cache_page(vma, address, pte_pfn(entry));
  63                 pte_val(entry) &= ~shared_pte_mask;
  64                 set_pte_at(vma->vm_mm, address, pte, entry);
  65                 flush_tlb_page(vma, address);
  66                 ret = 1;
  67         }
  68         pte_unmap(pte);
  69         return ret;
  70
  71 bad_pgd:
  72         pgd_ERROR(*pgd);
  73         pgd_clear(pgd);
  74 no_pgd:
  75         return 0;
  76
  77 bad_pmd:
  78         pmd_ERROR(*pmd);
  79         pmd_clear(pmd);
  80 no_pmd:
  81         return 0;
  82 }
  83
  84 static void
  85 make_coherent(struct address_space *mapping, struct vm_area_struct *vma, unsigned long addr, unsigned long pfn)
  86 {
  87         struct mm_struct *mm = vma->vm_mm;
  88         struct vm_area_struct *mpnt;
  89         struct prio_tree_iter iter;
  90         unsigned long offset;
  91         pgoff_t pgoff;
  92         int aliases = 0;
  93
  94         pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT);
  95
  96         /*
  97          * If we have any shared mappings that are in the same mm
  98          * space, then we need to handle them specially to maintain
  99          * cache coherency.
 100          */
 101         flush_dcache_mmap_lock(mapping);
 102         vma_prio_tree_foreach(mpnt, &iter, &mapping->i_mmap, pgoff, pgoff) {
 103                 /*
 104                  * If this VMA is not in our MM, we can ignore it.
 105                  * Note that we intentionally mask out the VMA
 106                  * that we are fixing up.
 107                  */
 108                 if (mpnt->vm_mm != mm || mpnt == vma)
 109                         continue;
 110                 if (!(mpnt->vm_flags & VM_MAYSHARE))
 111                         continue;
 112                 offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
 113                 aliases += adjust_pte(mpnt, mpnt->vm_start + offset);
 114         }
 115         flush_dcache_mmap_unlock(mapping);
 116         if (aliases)
 117                 adjust_pte(vma, addr);
 118         else
 119                 flush_cache_page(vma, addr, pfn);
 120 }
 121
 122 /*
 123  * Take care of architecture specific things when placing a new PTE into
 124  * a page table, or changing an existing PTE.  Basically, there are two
 125  * things that we need to take care of:
 126  *
 127  *  1. If PG_dcache_dirty is set for the page, we need to ensure
 128  *     that any cache entries for the kernels virtual memory
 129  *     range are written back to the page.
 130  *  2. If we have multiple shared mappings of the same space in
 131  *     an object, we need to deal with the cache aliasing issues.
 132  *
 133  * Note that the pte lock will be held.
 134  */
 135 void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
 136 {
 137         unsigned long pfn = pte_pfn(pte);
 138         struct address_space *mapping;
 139         struct page *page;
 140
 141         if (!pfn_valid(pfn))
 142                 return;
 143
 144         page = pfn_to_page(pfn);
 145         mapping = page_mapping(page);
 146         if (mapping) {
 147                 int dirty = test_and_clear_bit(PG_dcache_dirty, &page->flags);
 148
 149                 if (dirty)
 150                         __flush_dcache_page(mapping, page);
 151
 152                 if (cache_is_vivt())
 153                         make_coherent(mapping, vma, addr, pfn);
 154         }
 155 }
 156
 157 /*
 158  * Check whether the write buffer has physical address aliasing
 159  * issues.  If it has, we need to avoid them for the case where
 160  * we have several shared mappings of the same object in user
 161  * space.
 162  */
 163 static int __init check_writebuffer(unsigned long *p1, unsigned long *p2)
 164 {
 165         register unsigned long zero = 0, one = 1, val;
 166
 167         local_irq_disable();
 168         mb();
 169         *p1 = one;
 170         mb();
 171         *p2 = zero;
 172         mb();
 173         val = *p1;
 174         mb();
 175         local_irq_enable();
 176         return val != zero;
 177 }
 178
 179 void __init check_writebuffer_bugs(void)
 180 {
 181         struct page *page;
 182         const char *reason;
 183         unsigned long v = 1;
 184
 185         printk(KERN_INFO "CPU: Testing write buffer coherency: ");
 186
 187         page = alloc_page(GFP_KERNEL);
 188         if (page) {
 189                 unsigned long *p1, *p2;
 190                 pgprot_t prot = __pgprot(L_PTE_PRESENT|L_PTE_YOUNG|
 191                                          L_PTE_DIRTY|L_PTE_WRITE|
 192                                          L_PTE_BUFFERABLE);
 193
 194                 p1 = vmap(&page, 1, VM_IOREMAP, prot);
 195                 p2 = vmap(&page, 1, VM_IOREMAP, prot);
 196
 197                 if (p1 && p2) {
 198                         v = check_writebuffer(p1, p2);
 199                         reason = "enabling work-around";
 200                 } else {
 201                         reason = "unable to map memory\n";
 202                 }
 203
 204                 vunmap(p1);
 205                 vunmap(p2);
 206                 put_page(page);
 207         } else {
 208                 reason = "unable to grab page\n";
 209         }
 210
 211         if (v) {
 212                 printk("failed, %s\n", reason);
 213                 shared_pte_mask |= L_PTE_BUFFERABLE;
 214         } else {
 215                 printk("ok\n");
 216         }
 217 }