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/bugs.h>
  21 #include <asm/cacheflush.h>
  22 #include <asm/cachetype.h>
  23 #include <asm/pgtable.h>
  24 #include <asm/tlbflush.h>
  25
  26 static unsigned long shared_pte_mask = L_PTE_MT_BUFFERABLE;
  27
  28 /*
  29  * We take the easy way out of this problem - we make the
  30  * PTE uncacheable.  However, we leave the write buffer on.
  31  *
  32  * Note that the pte lock held when calling update_mmu_cache must also
  33  * guard the pte (somewhere else in the same mm) that we modify here.
  34  * Therefore those configurations which might call adjust_pte (those
  35  * without CONFIG_CPU_CACHE_VIPT) cannot support split page_table_lock.
  36  */
  37 static int adjust_pte(struct vm_area_struct *vma, unsigned long address)
  38 {
  39         pgd_t *pgd;
  40         pmd_t *pmd;
  41         pte_t *pte, entry;
  42         int ret;
  43
  44         pgd = pgd_offset(vma->vm_mm, address);
  45         if (pgd_none(*pgd))
  46                 goto no_pgd;
  47         if (pgd_bad(*pgd))
  48                 goto bad_pgd;
  49
  50         pmd = pmd_offset(pgd, address);
  51         if (pmd_none(*pmd))
  52                 goto no_pmd;
  53         if (pmd_bad(*pmd))
  54                 goto bad_pmd;
  55
  56         pte = pte_offset_map(pmd, address);
  57         entry = *pte;
  58
  59         /*
  60          * If this page is present, it's actually being shared.
  61          */
  62         ret = pte_present(entry);
  63
  64         /*
  65          * If this page isn't present, or is already setup to
  66          * fault (ie, is old), we can safely ignore any issues.
  67          */
  68         if (ret && (pte_val(entry) & L_PTE_MT_MASK) != shared_pte_mask) {
  69                 flush_cache_page(vma, address, pte_pfn(entry));
  70                 pte_val(entry) &= ~L_PTE_MT_MASK;
  71                 pte_val(entry) |= shared_pte_mask;
  72                 set_pte_at(vma->vm_mm, address, pte, entry);
  73                 flush_tlb_page(vma, address);
  74         }
  75         pte_unmap(pte);
  76         return ret;
  77
  78 bad_pgd:
  79         pgd_ERROR(*pgd);
  80         pgd_clear(pgd);
  81 no_pgd:
  82         return 0;
  83
  84 bad_pmd:
  85         pmd_ERROR(*pmd);
  86         pmd_clear(pmd);
  87 no_pmd:
  88         return 0;
  89 }
  90
  91 static void
  92 make_coherent(struct address_space *mapping, struct vm_area_struct *vma, unsigned long addr, unsigned long pfn)
  93 {
  94         struct mm_struct *mm = vma->vm_mm;
  95         struct vm_area_struct *mpnt;
  96         struct prio_tree_iter iter;
  97         unsigned long offset;
  98         pgoff_t pgoff;
  99         int aliases = 0;
 100
 101         pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT);
 102
 103         /*
 104          * If we have any shared mappings that are in the same mm
 105          * space, then we need to handle them specially to maintain
 106          * cache coherency.
 107          */
 108         flush_dcache_mmap_lock(mapping);
 109         vma_prio_tree_foreach(mpnt, &iter, &mapping->i_mmap, pgoff, pgoff) {
 110                 /*
 111                  * If this VMA is not in our MM, we can ignore it.
 112                  * Note that we intentionally mask out the VMA
 113                  * that we are fixing up.
 114                  */
 115                 if (mpnt->vm_mm != mm || mpnt == vma)
 116                         continue;
 117                 if (!(mpnt->vm_flags & VM_MAYSHARE))
 118                         continue;
 119                 offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
 120                 aliases += adjust_pte(mpnt, mpnt->vm_start + offset);
 121         }
 122         flush_dcache_mmap_unlock(mapping);
 123         if (aliases)
 124                 adjust_pte(vma, addr);
 125         else
 126                 flush_cache_page(vma, addr, pfn);
 127 }
 128
 129 /*
 130  * Take care of architecture specific things when placing a new PTE into
 131  * a page table, or changing an existing PTE.  Basically, there are two
 132  * things that we need to take care of:
 133  *
 134  *  1. If PG_dcache_dirty is set for the page, we need to ensure
 135  *     that any cache entries for the kernels virtual memory
 136  *     range are written back to the page.
 137  *  2. If we have multiple shared mappings of the same space in
 138  *     an object, we need to deal with the cache aliasing issues.
 139  *
 140  * Note that the pte lock will be held.
 141  */
 142 void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
 143 {
 144         unsigned long pfn = pte_pfn(pte);
 145         struct address_space *mapping;
 146         struct page *page;
 147
 148         if (!pfn_valid(pfn))
 149                 return;
 150
 151         page = pfn_to_page(pfn);
 152         mapping = page_mapping(page);
 153         if (mapping) {
 154 #ifndef CONFIG_SMP
 155                 int dirty = test_and_clear_bit(PG_dcache_dirty, &page->flags);
 156
 157                 if (dirty)
 158                         __flush_dcache_page(mapping, page);
 159 #endif
 160
 161                 if (cache_is_vivt())
 162                         make_coherent(mapping, vma, addr, pfn);
 163                 else if (vma->vm_flags & VM_EXEC)
 164                         __flush_icache_all();
 165         }
 166 }
 167
 168 /*
 169  * Check whether the write buffer has physical address aliasing
 170  * issues.  If it has, we need to avoid them for the case where
 171  * we have several shared mappings of the same object in user
 172  * space.
 173  */
 174 static int __init check_writebuffer(unsigned long *p1, unsigned long *p2)
 175 {
 176         register unsigned long zero = 0, one = 1, val;
 177
 178         local_irq_disable();
 179         mb();
 180         *p1 = one;
 181         mb();
 182         *p2 = zero;
 183         mb();
 184         val = *p1;
 185         mb();
 186         local_irq_enable();
 187         return val != zero;
 188 }
 189
 190 void __init check_writebuffer_bugs(void)
 191 {
 192         struct page *page;
 193         const char *reason;
 194         unsigned long v = 1;
 195
 196         printk(KERN_INFO "CPU: Testing write buffer coherency: ");
 197
 198         page = alloc_page(GFP_KERNEL);
 199         if (page) {
 200                 unsigned long *p1, *p2;
 201                 pgprot_t prot = __pgprot(L_PTE_PRESENT|L_PTE_YOUNG|
 202                                          L_PTE_DIRTY|L_PTE_WRITE|
 203                                          L_PTE_MT_BUFFERABLE);
 204
 205                 p1 = vmap(&page, 1, VM_IOREMAP, prot);
 206                 p2 = vmap(&page, 1, VM_IOREMAP, prot);
 207
 208                 if (p1 && p2) {
 209                         v = check_writebuffer(p1, p2);
 210                         reason = "enabling work-around";
 211                 } else {
 212                         reason = "unable to map memory\n";
 213                 }
 214
 215                 vunmap(p1);
 216                 vunmap(p2);
 217                 put_page(page);
 218         } else {
 219                 reason = "unable to grab page\n";
 220         }
 221
 222         if (v) {
 223                 printk("failed, %s\n", reason);
 224                 shared_pte_mask = L_PTE_MT_UNCACHED;
 225         } else {
 226                 printk("ok\n");
 227         }
 228 }