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 #include "mm.h"
  27
  28 static unsigned long shared_pte_mask = L_PTE_MT_BUFFERABLE;
  29
  30 /*
  31  * We take the easy way out of this problem - we make the
  32  * PTE uncacheable.  However, we leave the write buffer on.
  33  *
  34  * Note that the pte lock held when calling update_mmu_cache must also
  35  * guard the pte (somewhere else in the same mm) that we modify here.
  36  * Therefore those configurations which might call adjust_pte (those
  37  * without CONFIG_CPU_CACHE_VIPT) cannot support split page_table_lock.
  38  */
  39 static int adjust_pte(struct vm_area_struct *vma, unsigned long address)
  40 {
  41         pgd_t *pgd;
  42         pmd_t *pmd;
  43         pte_t *pte, entry;
  44         int ret;
  45
  46         pgd = pgd_offset(vma->vm_mm, address);
  47         if (pgd_none(*pgd))
  48                 goto no_pgd;
  49         if (pgd_bad(*pgd))
  50                 goto bad_pgd;
  51
  52         pmd = pmd_offset(pgd, address);
  53         if (pmd_none(*pmd))
  54                 goto no_pmd;
  55         if (pmd_bad(*pmd))
  56                 goto bad_pmd;
  57
  58         pte = pte_offset_map(pmd, address);
  59         entry = *pte;
  60
  61         /*
  62          * If this page is present, it's actually being shared.
  63          */
  64         ret = pte_present(entry);
  65
  66         /*
  67          * If this page isn't present, or is already setup to
  68          * fault (ie, is old), we can safely ignore any issues.
  69          */
  70         if (ret && (pte_val(entry) & L_PTE_MT_MASK) != shared_pte_mask) {
  71                 unsigned long pfn = pte_pfn(entry);
  72                 flush_cache_page(vma, address, pfn);
  73                 outer_flush_range((pfn << PAGE_SHIFT),
  74                                   (pfn << PAGE_SHIFT) + PAGE_SIZE);
  75                 pte_val(entry) &= ~L_PTE_MT_MASK;
  76                 pte_val(entry) |= shared_pte_mask;
  77                 set_pte_at(vma->vm_mm, address, pte, entry);
  78                 flush_tlb_page(vma, address);
  79         }
  80         pte_unmap(pte);
  81         return ret;
  82
  83 bad_pgd:
  84         pgd_ERROR(*pgd);
  85         pgd_clear(pgd);
  86 no_pgd:
  87         return 0;
  88
  89 bad_pmd:
  90         pmd_ERROR(*pmd);
  91         pmd_clear(pmd);
  92 no_pmd:
  93         return 0;
  94 }
  95
  96 static void
  97 make_coherent(struct address_space *mapping, struct vm_area_struct *vma, unsigned long addr, unsigned long pfn)
  98 {
  99         struct mm_struct *mm = vma->vm_mm;
 100         struct vm_area_struct *mpnt;
 101         struct prio_tree_iter iter;
 102         unsigned long offset;
 103         pgoff_t pgoff;
 104         int aliases = 0;
 105
 106         pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT);
 107
 108         /*
 109          * If we have any shared mappings that are in the same mm
 110          * space, then we need to handle them specially to maintain
 111          * cache coherency.
 112          */
 113         flush_dcache_mmap_lock(mapping);
 114         vma_prio_tree_foreach(mpnt, &iter, &mapping->i_mmap, pgoff, pgoff) {
 115                 /*
 116                  * If this VMA is not in our MM, we can ignore it.
 117                  * Note that we intentionally mask out the VMA
 118                  * that we are fixing up.
 119                  */
 120                 if (mpnt->vm_mm != mm || mpnt == vma)
 121                         continue;
 122                 if (!(mpnt->vm_flags & VM_MAYSHARE))
 123                         continue;
 124                 offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
 125                 aliases += adjust_pte(mpnt, mpnt->vm_start + offset);
 126         }
 127         flush_dcache_mmap_unlock(mapping);
 128         if (aliases)
 129                 adjust_pte(vma, addr);
 130         else
 131                 flush_cache_page(vma, addr, pfn);
 132 }
 133
 134 /*
 135  * Take care of architecture specific things when placing a new PTE into
 136  * a page table, or changing an existing PTE.  Basically, there are two
 137  * things that we need to take care of:
 138  *
 139  *  1. If PG_dcache_dirty is set for the page, we need to ensure
 140  *     that any cache entries for the kernels virtual memory
 141  *     range are written back to the page.
 142  *  2. If we have multiple shared mappings of the same space in
 143  *     an object, we need to deal with the cache aliasing issues.
 144  *
 145  * Note that the pte lock will be held.
 146  */
 147 void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
 148 {
 149         unsigned long pfn = pte_pfn(pte);
 150         struct address_space *mapping;
 151         struct page *page;
 152
 153         if (!pfn_valid(pfn))
 154                 return;
 155
 156         /*
 157          * The zero page is never written to, so never has any dirty
 158          * cache lines, and therefore never needs to be flushed.
 159          */
 160         page = pfn_to_page(pfn);
 161         if (page == ZERO_PAGE(0))
 162                 return;
 163
 164         mapping = page_mapping(page);
 165 #ifndef CONFIG_SMP
 166         if (test_and_clear_bit(PG_dcache_dirty, &page->flags))
 167                 __flush_dcache_page(mapping, page);
 168 #endif
 169         if (mapping) {
 170                 if (cache_is_vivt())
 171                         make_coherent(mapping, vma, addr, pfn);
 172                 else if (vma->vm_flags & VM_EXEC)
 173                         __flush_icache_all();
 174         }
 175 }
 176
 177 /*
 178  * Check whether the write buffer has physical address aliasing
 179  * issues.  If it has, we need to avoid them for the case where
 180  * we have several shared mappings of the same object in user
 181  * space.
 182  */
 183 static int __init check_writebuffer(unsigned long *p1, unsigned long *p2)
 184 {
 185         register unsigned long zero = 0, one = 1, val;
 186
 187         local_irq_disable();
 188         mb();
 189         *p1 = one;
 190         mb();
 191         *p2 = zero;
 192         mb();
 193         val = *p1;
 194         mb();
 195         local_irq_enable();
 196         return val != zero;
 197 }
 198
 199 void __init check_writebuffer_bugs(void)
 200 {
 201         struct page *page;
 202         const char *reason;
 203         unsigned long v = 1;
 204
 205         printk(KERN_INFO "CPU: Testing write buffer coherency: ");
 206
 207         page = alloc_page(GFP_KERNEL);
 208         if (page) {
 209                 unsigned long *p1, *p2;
 210                 pgprot_t prot = __pgprot(L_PTE_PRESENT|L_PTE_YOUNG|
 211                                          L_PTE_DIRTY|L_PTE_WRITE|
 212                                          L_PTE_MT_BUFFERABLE);
 213
 214                 p1 = vmap(&page, 1, VM_IOREMAP, prot);
 215                 p2 = vmap(&page, 1, VM_IOREMAP, prot);
 216
 217                 if (p1 && p2) {
 218                         v = check_writebuffer(p1, p2);
 219                         reason = "enabling work-around";
 220                 } else {
 221                         reason = "unable to map memory\n";
 222                 }
 223
 224                 vunmap(p1);
 225                 vunmap(p2);
 226                 put_page(page);
 227         } else {
 228                 reason = "unable to grab page\n";
 229         }
 230
 231         if (v) {
 232                 printk("failed, %s\n", reason);
 233                 shared_pte_mask = L_PTE_MT_UNCACHED;
 234         } else {
 235                 printk("ok\n");
 236         }
 237 }