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 #include <linux/gfp.h>
  20
  21 #include <asm/bugs.h>
  22 #include <asm/cacheflush.h>
  23 #include <asm/cachetype.h>
  24 #include <asm/pgtable.h>
  25 #include <asm/tlbflush.h>
  26
  27 #include "mm.h"
  28
  29 static pteval_t shared_pte_mask = L_PTE_MT_BUFFERABLE;
  30
  31 #if __LINUX_ARM_ARCH__ < 6
  32 /*
  33  * We take the easy way out of this problem - we make the
  34  * PTE uncacheable.  However, we leave the write buffer on.
  35  *
  36  * Note that the pte lock held when calling update_mmu_cache must also
  37  * guard the pte (somewhere else in the same mm) that we modify here.
  38  * Therefore those configurations which might call adjust_pte (those
  39  * without CONFIG_CPU_CACHE_VIPT) cannot support split page_table_lock.
  40  */
  41 static int do_adjust_pte(struct vm_area_struct *vma, unsigned long address,
  42         unsigned long pfn, pte_t *ptep)
  43 {
  44         pte_t entry = *ptep;
  45         int ret;
  46
  47         /*
  48          * If this page is present, it's actually being shared.
  49          */
  50         ret = pte_present(entry);
  51
  52         /*
  53          * If this page isn't present, or is already setup to
  54          * fault (ie, is old), we can safely ignore any issues.
  55          */
  56         if (ret && (pte_val(entry) & L_PTE_MT_MASK) != shared_pte_mask) {
  57                 flush_cache_page(vma, address, pfn);
  58                 outer_flush_range((pfn << PAGE_SHIFT),
  59                                   (pfn << PAGE_SHIFT) + PAGE_SIZE);
  60                 pte_val(entry) &= ~L_PTE_MT_MASK;
  61                 pte_val(entry) |= shared_pte_mask;
  62                 set_pte_at(vma->vm_mm, address, ptep, entry);
  63                 flush_tlb_page(vma, address);
  64         }
  65
  66         return ret;
  67 }
  68
  69 #if USE_SPLIT_PTLOCKS
  70 /*
  71  * If we are using split PTE locks, then we need to take the page
  72  * lock here.  Otherwise we are using shared mm->page_table_lock
  73  * which is already locked, thus cannot take it.
  74  */
  75 static inline void do_pte_lock(spinlock_t *ptl)
  76 {
  77         /*
  78          * Use nested version here to indicate that we are already
  79          * holding one similar spinlock.
  80          */
  81         spin_lock_nested(ptl, SINGLE_DEPTH_NESTING);
  82 }
  83
  84 static inline void do_pte_unlock(spinlock_t *ptl)
  85 {
  86         spin_unlock(ptl);
  87 }
  88 #else /* !USE_SPLIT_PTLOCKS */
  89 static inline void do_pte_lock(spinlock_t *ptl) {}
  90 static inline void do_pte_unlock(spinlock_t *ptl) {}
  91 #endif /* USE_SPLIT_PTLOCKS */
  92
  93 static int adjust_pte(struct vm_area_struct *vma, unsigned long address,
  94         unsigned long pfn)
  95 {
  96         spinlock_t *ptl;
  97         pgd_t *pgd;
  98         pmd_t *pmd;
  99         pte_t *pte;
 100         int ret;
 101
 102         pgd = pgd_offset(vma->vm_mm, address);
 103         if (pgd_none_or_clear_bad(pgd))
 104                 return 0;
 105
 106         pmd = pmd_offset(pgd, address);
 107         if (pmd_none_or_clear_bad(pmd))
 108                 return 0;
 109
 110         /*
 111          * This is called while another page table is mapped, so we
 112          * must use the nested version.  This also means we need to
 113          * open-code the spin-locking.
 114          */
 115         ptl = pte_lockptr(vma->vm_mm, pmd);
 116         pte = pte_offset_map(pmd, address);
 117         do_pte_lock(ptl);
 118
 119         ret = do_adjust_pte(vma, address, pfn, pte);
 120
 121         do_pte_unlock(ptl);
 122         pte_unmap(pte);
 123
 124         return ret;
 125 }
 126
 127 static void
 128 make_coherent(struct address_space *mapping, struct vm_area_struct *vma,
 129         unsigned long addr, pte_t *ptep, unsigned long pfn)
 130 {
 131         struct mm_struct *mm = vma->vm_mm;
 132         struct vm_area_struct *mpnt;
 133         struct prio_tree_iter iter;
 134         unsigned long offset;
 135         pgoff_t pgoff;
 136         int aliases = 0;
 137
 138         pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT);
 139
 140         /*
 141          * If we have any shared mappings that are in the same mm
 142          * space, then we need to handle them specially to maintain
 143          * cache coherency.
 144          */
 145         flush_dcache_mmap_lock(mapping);
 146         vma_prio_tree_foreach(mpnt, &iter, &mapping->i_mmap, pgoff, pgoff) {
 147                 /*
 148                  * If this VMA is not in our MM, we can ignore it.
 149                  * Note that we intentionally mask out the VMA
 150                  * that we are fixing up.
 151                  */
 152                 if (mpnt->vm_mm != mm || mpnt == vma)
 153                         continue;
 154                 if (!(mpnt->vm_flags & VM_MAYSHARE))
 155                         continue;
 156                 offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
 157                 aliases += adjust_pte(mpnt, mpnt->vm_start + offset, pfn);
 158         }
 159         flush_dcache_mmap_unlock(mapping);
 160         if (aliases)
 161                 do_adjust_pte(vma, addr, pfn, ptep);
 162 }
 163
 164 /*
 165  * Take care of architecture specific things when placing a new PTE into
 166  * a page table, or changing an existing PTE.  Basically, there are two
 167  * things that we need to take care of:
 168  *
 169  *  1. If PG_dcache_clean is not set for the page, we need to ensure
 170  *     that any cache entries for the kernels virtual memory
 171  *     range are written back to the page.
 172  *  2. If we have multiple shared mappings of the same space in
 173  *     an object, we need to deal with the cache aliasing issues.
 174  *
 175  * Note that the pte lock will be held.
 176  */
 177 void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr,
 178         pte_t *ptep)
 179 {
 180         unsigned long pfn = pte_pfn(*ptep);
 181         struct address_space *mapping;
 182         struct page *page;
 183
 184         if (!pfn_valid(pfn))
 185                 return;
 186
 187         /*
 188          * The zero page is never written to, so never has any dirty
 189          * cache lines, and therefore never needs to be flushed.
 190          */
 191         page = pfn_to_page(pfn);
 192         if (page == ZERO_PAGE(0))
 193                 return;
 194
 195         mapping = page_mapping(page);
 196         if (!test_and_set_bit(PG_dcache_clean, &page->flags))
 197                 __flush_dcache_page(mapping, page);
 198         if (mapping) {
 199                 if (cache_is_vivt())
 200                         make_coherent(mapping, vma, addr, ptep, pfn);
 201                 else if (vma->vm_flags & VM_EXEC)
 202                         __flush_icache_all();
 203         }
 204 }
 205 #endif  /* __LINUX_ARM_ARCH__ < 6 */
 206
 207 /*
 208  * Check whether the write buffer has physical address aliasing
 209  * issues.  If it has, we need to avoid them for the case where
 210  * we have several shared mappings of the same object in user
 211  * space.
 212  */
 213 static int __init check_writebuffer(unsigned long *p1, unsigned long *p2)
 214 {
 215         register unsigned long zero = 0, one = 1, val;
 216
 217         local_irq_disable();
 218         mb();
 219         *p1 = one;
 220         mb();
 221         *p2 = zero;
 222         mb();
 223         val = *p1;
 224         mb();
 225         local_irq_enable();
 226         return val != zero;
 227 }
 228
 229 void __init check_writebuffer_bugs(void)
 230 {
 231         struct page *page;
 232         const char *reason;
 233         unsigned long v = 1;
 234
 235         printk(KERN_INFO "CPU: Testing write buffer coherency: ");
 236
 237         page = alloc_page(GFP_KERNEL);
 238         if (page) {
 239                 unsigned long *p1, *p2;
 240                 pgprot_t prot = __pgprot_modify(PAGE_KERNEL,
 241                                         L_PTE_MT_MASK, L_PTE_MT_BUFFERABLE);
 242
 243                 p1 = vmap(&page, 1, VM_IOREMAP, prot);
 244                 p2 = vmap(&page, 1, VM_IOREMAP, prot);
 245
 246                 if (p1 && p2) {
 247                         v = check_writebuffer(p1, p2);
 248                         reason = "enabling work-around";
 249                 } else {
 250                         reason = "unable to map memory\n";
 251                 }
 252
 253                 vunmap(p1);
 254                 vunmap(p2);
 255                 put_page(page);
 256         } else {
 257                 reason = "unable to grab page\n";
 258         }
 259
 260         if (v) {
 261                 printk("failed, %s\n", reason);
 262                 shared_pte_mask = L_PTE_MT_UNCACHED;
 263         } else {
 264                 printk("ok\n");
 265         }
 266 }