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