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/sched.h> 12 #include <linux/kernel.h> 13 #include <linux/mm.h> 14 #include <linux/bitops.h> 15 #include <linux/vmalloc.h> 16 #include <linux/init.h> 17 #include <linux/pagemap.h> 18 #include <linux/gfp.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 pteval_t shared_pte_mask = L_PTE_MT_BUFFERABLE; 29 30 #if __LINUX_ARM_ARCH__ < 6 31 /* 32 * We take the easy way out of this problem - we make the 33 * PTE uncacheable. However, we leave the write buffer on. 34 * 35 * Note that the pte lock held when calling update_mmu_cache must also 36 * guard the pte (somewhere else in the same mm) that we modify here. 37 * Therefore those configurations which might call adjust_pte (those 38 * without CONFIG_CPU_CACHE_VIPT) cannot support split page_table_lock. 39 */ 40 static int do_adjust_pte(struct vm_area_struct *vma, unsigned long address, 41 unsigned long pfn, pte_t *ptep) 42 { 43 pte_t entry = *ptep; 44 int ret; 45 46 /* 47 * If this page is present, it's actually being shared. 48 */ 49 ret = pte_present(entry); 50 51 /* 52 * If this page isn't present, or is already setup to 53 * fault (ie, is old), we can safely ignore any issues. 54 */ 55 if (ret && (pte_val(entry) & L_PTE_MT_MASK) != shared_pte_mask) { 56 flush_cache_page(vma, address, pfn); 57 outer_flush_range((pfn << PAGE_SHIFT), 58 (pfn << PAGE_SHIFT) + PAGE_SIZE); 59 pte_val(entry) &= ~L_PTE_MT_MASK; 60 pte_val(entry) |= shared_pte_mask; 61 set_pte_at(vma->vm_mm, address, ptep, entry); 62 flush_tlb_page(vma, address); 63 } 64 65 return ret; 66 } 67 68 #if USE_SPLIT_PTE_PTLOCKS 69 /* 70 * If we are using split PTE locks, then we need to take the page 71 * lock here. Otherwise we are using shared mm->page_table_lock 72 * which is already locked, thus cannot take it. 73 */ 74 static inline void do_pte_lock(spinlock_t *ptl) 75 { 76 /* 77 * Use nested version here to indicate that we are already 78 * holding one similar spinlock. 79 */ 80 spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); 81 } 82 83 static inline void do_pte_unlock(spinlock_t *ptl) 84 { 85 spin_unlock(ptl); 86 } 87 #else /* !USE_SPLIT_PTE_PTLOCKS */ 88 static inline void do_pte_lock(spinlock_t *ptl) {} 89 static inline void do_pte_unlock(spinlock_t *ptl) {} 90 #endif /* USE_SPLIT_PTE_PTLOCKS */ 91 92 static int adjust_pte(struct vm_area_struct *vma, unsigned long address, 93 unsigned long pfn) 94 { 95 spinlock_t *ptl; 96 pgd_t *pgd; 97 pud_t *pud; 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 pud = pud_offset(pgd, address); 107 if (pud_none_or_clear_bad(pud)) 108 return 0; 109 110 pmd = pmd_offset(pud, address); 111 if (pmd_none_or_clear_bad(pmd)) 112 return 0; 113 114 /* 115 * This is called while another page table is mapped, so we 116 * must use the nested version. This also means we need to 117 * open-code the spin-locking. 118 */ 119 ptl = pte_lockptr(vma->vm_mm, pmd); 120 pte = pte_offset_map(pmd, address); 121 do_pte_lock(ptl); 122 123 ret = do_adjust_pte(vma, address, pfn, pte); 124 125 do_pte_unlock(ptl); 126 pte_unmap(pte); 127 128 return ret; 129 } 130 131 static void 132 make_coherent(struct address_space *mapping, struct vm_area_struct *vma, 133 unsigned long addr, pte_t *ptep, unsigned long pfn) 134 { 135 struct mm_struct *mm = vma->vm_mm; 136 struct vm_area_struct *mpnt; 137 unsigned long offset; 138 pgoff_t pgoff; 139 int aliases = 0; 140 141 pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT); 142 143 /* 144 * If we have any shared mappings that are in the same mm 145 * space, then we need to handle them specially to maintain 146 * cache coherency. 147 */ 148 flush_dcache_mmap_lock(mapping); 149 vma_interval_tree_foreach(mpnt, &mapping->i_mmap, pgoff, pgoff) { 150 /* 151 * If this VMA is not in our MM, we can ignore it. 152 * Note that we intentionally mask out the VMA 153 * that we are fixing up. 154 */ 155 if (mpnt->vm_mm != mm || mpnt == vma) 156 continue; 157 if (!(mpnt->vm_flags & VM_MAYSHARE)) 158 continue; 159 offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT; 160 aliases += adjust_pte(mpnt, mpnt->vm_start + offset, pfn); 161 } 162 flush_dcache_mmap_unlock(mapping); 163 if (aliases) 164 do_adjust_pte(vma, addr, pfn, ptep); 165 } 166 167 /* 168 * Take care of architecture specific things when placing a new PTE into 169 * a page table, or changing an existing PTE. Basically, there are two 170 * things that we need to take care of: 171 * 172 * 1. If PG_dcache_clean is not set for the page, we need to ensure 173 * that any cache entries for the kernels virtual memory 174 * range are written back to the page. 175 * 2. If we have multiple shared mappings of the same space in 176 * an object, we need to deal with the cache aliasing issues. 177 * 178 * Note that the pte lock will be held. 179 */ 180 void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr, 181 pte_t *ptep) 182 { 183 unsigned long pfn = pte_pfn(*ptep); 184 struct address_space *mapping; 185 struct page *page; 186 187 if (!pfn_valid(pfn)) 188 return; 189 190 /* 191 * The zero page is never written to, so never has any dirty 192 * cache lines, and therefore never needs to be flushed. 193 */ 194 page = pfn_to_page(pfn); 195 if (page == ZERO_PAGE(0)) 196 return; 197 198 mapping = page_mapping(page); 199 if (!test_and_set_bit(PG_dcache_clean, &page->flags)) 200 __flush_dcache_page(mapping, page); 201 if (mapping) { 202 if (cache_is_vivt()) 203 make_coherent(mapping, vma, addr, ptep, pfn); 204 else if (vma->vm_flags & VM_EXEC) 205 __flush_icache_all(); 206 } 207 } 208 #endif /* __LINUX_ARM_ARCH__ < 6 */ 209 210 /* 211 * Check whether the write buffer has physical address aliasing 212 * issues. If it has, we need to avoid them for the case where 213 * we have several shared mappings of the same object in user 214 * space. 215 */ 216 static int __init check_writebuffer(unsigned long *p1, unsigned long *p2) 217 { 218 register unsigned long zero = 0, one = 1, val; 219 220 local_irq_disable(); 221 mb(); 222 *p1 = one; 223 mb(); 224 *p2 = zero; 225 mb(); 226 val = *p1; 227 mb(); 228 local_irq_enable(); 229 return val != zero; 230 } 231 232 void __init check_writebuffer_bugs(void) 233 { 234 struct page *page; 235 const char *reason; 236 unsigned long v = 1; 237 238 pr_info("CPU: Testing write buffer coherency: "); 239 240 page = alloc_page(GFP_KERNEL); 241 if (page) { 242 unsigned long *p1, *p2; 243 pgprot_t prot = __pgprot_modify(PAGE_KERNEL, 244 L_PTE_MT_MASK, L_PTE_MT_BUFFERABLE); 245 246 p1 = vmap(&page, 1, VM_IOREMAP, prot); 247 p2 = vmap(&page, 1, VM_IOREMAP, prot); 248 249 if (p1 && p2) { 250 v = check_writebuffer(p1, p2); 251 reason = "enabling work-around"; 252 } else { 253 reason = "unable to map memory\n"; 254 } 255 256 vunmap(p1); 257 vunmap(p2); 258 put_page(page); 259 } else { 260 reason = "unable to grab page\n"; 261 } 262 263 if (v) { 264 pr_cont("failed, %s\n", reason); 265 shared_pte_mask = L_PTE_MT_UNCACHED; 266 } else { 267 pr_cont("ok\n"); 268 } 269 } 270