1 /* 2 * This file contains common routines for dealing with free of page tables 3 * Along with common page table handling code 4 * 5 * Derived from arch/powerpc/mm/tlb_64.c: 6 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) 7 * 8 * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au) 9 * and Cort Dougan (PReP) (cort@cs.nmt.edu) 10 * Copyright (C) 1996 Paul Mackerras 11 * 12 * Derived from "arch/i386/mm/init.c" 13 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 14 * 15 * Dave Engebretsen <engebret@us.ibm.com> 16 * Rework for PPC64 port. 17 * 18 * This program is free software; you can redistribute it and/or 19 * modify it under the terms of the GNU General Public License 20 * as published by the Free Software Foundation; either version 21 * 2 of the License, or (at your option) any later version. 22 */ 23 24 #include <linux/kernel.h> 25 #include <linux/mm.h> 26 #include <linux/init.h> 27 #include <linux/percpu.h> 28 #include <linux/hardirq.h> 29 #include <asm/pgalloc.h> 30 #include <asm/tlbflush.h> 31 #include <asm/tlb.h> 32 33 #include "mmu_decl.h" 34 35 DEFINE_PER_CPU(struct mmu_gather, mmu_gathers); 36 37 #ifdef CONFIG_SMP 38 39 /* 40 * Handle batching of page table freeing on SMP. Page tables are 41 * queued up and send to be freed later by RCU in order to avoid 42 * freeing a page table page that is being walked without locks 43 */ 44 45 static DEFINE_PER_CPU(struct pte_freelist_batch *, pte_freelist_cur); 46 static unsigned long pte_freelist_forced_free; 47 48 struct pte_freelist_batch 49 { 50 struct rcu_head rcu; 51 unsigned int index; 52 unsigned long tables[0]; 53 }; 54 55 #define PTE_FREELIST_SIZE \ 56 ((PAGE_SIZE - sizeof(struct pte_freelist_batch)) \ 57 / sizeof(unsigned long)) 58 59 static void pte_free_smp_sync(void *arg) 60 { 61 /* Do nothing, just ensure we sync with all CPUs */ 62 } 63 64 /* This is only called when we are critically out of memory 65 * (and fail to get a page in pte_free_tlb). 66 */ 67 static void pgtable_free_now(void *table, unsigned shift) 68 { 69 pte_freelist_forced_free++; 70 71 smp_call_function(pte_free_smp_sync, NULL, 1); 72 73 pgtable_free(table, shift); 74 } 75 76 static void pte_free_rcu_callback(struct rcu_head *head) 77 { 78 struct pte_freelist_batch *batch = 79 container_of(head, struct pte_freelist_batch, rcu); 80 unsigned int i; 81 82 for (i = 0; i < batch->index; i++) { 83 void *table = (void *)(batch->tables[i] & ~MAX_PGTABLE_INDEX_SIZE); 84 unsigned shift = batch->tables[i] & MAX_PGTABLE_INDEX_SIZE; 85 86 pgtable_free(table, shift); 87 } 88 89 free_page((unsigned long)batch); 90 } 91 92 static void pte_free_submit(struct pte_freelist_batch *batch) 93 { 94 INIT_RCU_HEAD(&batch->rcu); 95 call_rcu(&batch->rcu, pte_free_rcu_callback); 96 } 97 98 void pgtable_free_tlb(struct mmu_gather *tlb, void *table, unsigned shift) 99 { 100 /* This is safe since tlb_gather_mmu has disabled preemption */ 101 struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur); 102 unsigned long pgf; 103 104 if (atomic_read(&tlb->mm->mm_users) < 2 || 105 cpumask_equal(mm_cpumask(tlb->mm), cpumask_of(smp_processor_id()))){ 106 pgtable_free(table, shift); 107 return; 108 } 109 110 if (*batchp == NULL) { 111 *batchp = (struct pte_freelist_batch *)__get_free_page(GFP_ATOMIC); 112 if (*batchp == NULL) { 113 pgtable_free_now(table, shift); 114 return; 115 } 116 (*batchp)->index = 0; 117 } 118 BUG_ON(shift > MAX_PGTABLE_INDEX_SIZE); 119 pgf = (unsigned long)table | shift; 120 (*batchp)->tables[(*batchp)->index++] = pgf; 121 if ((*batchp)->index == PTE_FREELIST_SIZE) { 122 pte_free_submit(*batchp); 123 *batchp = NULL; 124 } 125 } 126 127 void pte_free_finish(void) 128 { 129 /* This is safe since tlb_gather_mmu has disabled preemption */ 130 struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur); 131 132 if (*batchp == NULL) 133 return; 134 pte_free_submit(*batchp); 135 *batchp = NULL; 136 } 137 138 #endif /* CONFIG_SMP */ 139 140 static inline int is_exec_fault(void) 141 { 142 return current->thread.regs && TRAP(current->thread.regs) == 0x400; 143 } 144 145 /* We only try to do i/d cache coherency on stuff that looks like 146 * reasonably "normal" PTEs. We currently require a PTE to be present 147 * and we avoid _PAGE_SPECIAL and _PAGE_NO_CACHE. We also only do that 148 * on userspace PTEs 149 */ 150 static inline int pte_looks_normal(pte_t pte) 151 { 152 return (pte_val(pte) & 153 (_PAGE_PRESENT | _PAGE_SPECIAL | _PAGE_NO_CACHE | _PAGE_USER)) == 154 (_PAGE_PRESENT | _PAGE_USER); 155 } 156 157 struct page * maybe_pte_to_page(pte_t pte) 158 { 159 unsigned long pfn = pte_pfn(pte); 160 struct page *page; 161 162 if (unlikely(!pfn_valid(pfn))) 163 return NULL; 164 page = pfn_to_page(pfn); 165 if (PageReserved(page)) 166 return NULL; 167 return page; 168 } 169 170 #if defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 171 172 /* Server-style MMU handles coherency when hashing if HW exec permission 173 * is supposed per page (currently 64-bit only). If not, then, we always 174 * flush the cache for valid PTEs in set_pte. Embedded CPU without HW exec 175 * support falls into the same category. 176 */ 177 178 static pte_t set_pte_filter(pte_t pte, unsigned long addr) 179 { 180 pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS); 181 if (pte_looks_normal(pte) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) || 182 cpu_has_feature(CPU_FTR_NOEXECUTE))) { 183 struct page *pg = maybe_pte_to_page(pte); 184 if (!pg) 185 return pte; 186 if (!test_bit(PG_arch_1, &pg->flags)) { 187 #ifdef CONFIG_8xx 188 /* On 8xx, cache control instructions (particularly 189 * "dcbst" from flush_dcache_icache) fault as write 190 * operation if there is an unpopulated TLB entry 191 * for the address in question. To workaround that, 192 * we invalidate the TLB here, thus avoiding dcbst 193 * misbehaviour. 194 */ 195 /* 8xx doesn't care about PID, size or ind args */ 196 _tlbil_va(addr, 0, 0, 0); 197 #endif /* CONFIG_8xx */ 198 flush_dcache_icache_page(pg); 199 set_bit(PG_arch_1, &pg->flags); 200 } 201 } 202 return pte; 203 } 204 205 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, 206 int dirty) 207 { 208 return pte; 209 } 210 211 #else /* defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 */ 212 213 /* Embedded type MMU with HW exec support. This is a bit more complicated 214 * as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so 215 * instead we "filter out" the exec permission for non clean pages. 216 */ 217 static pte_t set_pte_filter(pte_t pte, unsigned long addr) 218 { 219 struct page *pg; 220 221 /* No exec permission in the first place, move on */ 222 if (!(pte_val(pte) & _PAGE_EXEC) || !pte_looks_normal(pte)) 223 return pte; 224 225 /* If you set _PAGE_EXEC on weird pages you're on your own */ 226 pg = maybe_pte_to_page(pte); 227 if (unlikely(!pg)) 228 return pte; 229 230 /* If the page clean, we move on */ 231 if (test_bit(PG_arch_1, &pg->flags)) 232 return pte; 233 234 /* If it's an exec fault, we flush the cache and make it clean */ 235 if (is_exec_fault()) { 236 flush_dcache_icache_page(pg); 237 set_bit(PG_arch_1, &pg->flags); 238 return pte; 239 } 240 241 /* Else, we filter out _PAGE_EXEC */ 242 return __pte(pte_val(pte) & ~_PAGE_EXEC); 243 } 244 245 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, 246 int dirty) 247 { 248 struct page *pg; 249 250 /* So here, we only care about exec faults, as we use them 251 * to recover lost _PAGE_EXEC and perform I$/D$ coherency 252 * if necessary. Also if _PAGE_EXEC is already set, same deal, 253 * we just bail out 254 */ 255 if (dirty || (pte_val(pte) & _PAGE_EXEC) || !is_exec_fault()) 256 return pte; 257 258 #ifdef CONFIG_DEBUG_VM 259 /* So this is an exec fault, _PAGE_EXEC is not set. If it was 260 * an error we would have bailed out earlier in do_page_fault() 261 * but let's make sure of it 262 */ 263 if (WARN_ON(!(vma->vm_flags & VM_EXEC))) 264 return pte; 265 #endif /* CONFIG_DEBUG_VM */ 266 267 /* If you set _PAGE_EXEC on weird pages you're on your own */ 268 pg = maybe_pte_to_page(pte); 269 if (unlikely(!pg)) 270 goto bail; 271 272 /* If the page is already clean, we move on */ 273 if (test_bit(PG_arch_1, &pg->flags)) 274 goto bail; 275 276 /* Clean the page and set PG_arch_1 */ 277 flush_dcache_icache_page(pg); 278 set_bit(PG_arch_1, &pg->flags); 279 280 bail: 281 return __pte(pte_val(pte) | _PAGE_EXEC); 282 } 283 284 #endif /* !(defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0) */ 285 286 /* 287 * set_pte stores a linux PTE into the linux page table. 288 */ 289 void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, 290 pte_t pte) 291 { 292 #ifdef CONFIG_DEBUG_VM 293 WARN_ON(pte_present(*ptep)); 294 #endif 295 /* Note: mm->context.id might not yet have been assigned as 296 * this context might not have been activated yet when this 297 * is called. 298 */ 299 pte = set_pte_filter(pte, addr); 300 301 /* Perform the setting of the PTE */ 302 __set_pte_at(mm, addr, ptep, pte, 0); 303 } 304 305 /* 306 * This is called when relaxing access to a PTE. It's also called in the page 307 * fault path when we don't hit any of the major fault cases, ie, a minor 308 * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have 309 * handled those two for us, we additionally deal with missing execute 310 * permission here on some processors 311 */ 312 int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, 313 pte_t *ptep, pte_t entry, int dirty) 314 { 315 int changed; 316 entry = set_access_flags_filter(entry, vma, dirty); 317 changed = !pte_same(*(ptep), entry); 318 if (changed) { 319 if (!(vma->vm_flags & VM_HUGETLB)) 320 assert_pte_locked(vma->vm_mm, address); 321 __ptep_set_access_flags(ptep, entry); 322 flush_tlb_page_nohash(vma, address); 323 } 324 return changed; 325 } 326 327 #ifdef CONFIG_DEBUG_VM 328 void assert_pte_locked(struct mm_struct *mm, unsigned long addr) 329 { 330 pgd_t *pgd; 331 pud_t *pud; 332 pmd_t *pmd; 333 334 if (mm == &init_mm) 335 return; 336 pgd = mm->pgd + pgd_index(addr); 337 BUG_ON(pgd_none(*pgd)); 338 pud = pud_offset(pgd, addr); 339 BUG_ON(pud_none(*pud)); 340 pmd = pmd_offset(pud, addr); 341 BUG_ON(!pmd_present(*pmd)); 342 assert_spin_locked(pte_lockptr(mm, pmd)); 343 } 344 #endif /* CONFIG_DEBUG_VM */ 345 346