1 #ifndef _LINUX_MMU_NOTIFIER_H 2 #define _LINUX_MMU_NOTIFIER_H 3 4 #include <linux/list.h> 5 #include <linux/spinlock.h> 6 #include <linux/mm_types.h> 7 8 struct mmu_notifier; 9 struct mmu_notifier_ops; 10 11 #ifdef CONFIG_MMU_NOTIFIER 12 13 /* 14 * The mmu notifier_mm structure is allocated and installed in 15 * mm->mmu_notifier_mm inside the mm_take_all_locks() protected 16 * critical section and it's released only when mm_count reaches zero 17 * in mmdrop(). 18 */ 19 struct mmu_notifier_mm { 20 /* all mmu notifiers registerd in this mm are queued in this list */ 21 struct hlist_head list; 22 /* to serialize the list modifications and hlist_unhashed */ 23 spinlock_t lock; 24 }; 25 26 struct mmu_notifier_ops { 27 /* 28 * Called either by mmu_notifier_unregister or when the mm is 29 * being destroyed by exit_mmap, always before all pages are 30 * freed. This can run concurrently with other mmu notifier 31 * methods (the ones invoked outside the mm context) and it 32 * should tear down all secondary mmu mappings and freeze the 33 * secondary mmu. If this method isn't implemented you've to 34 * be sure that nothing could possibly write to the pages 35 * through the secondary mmu by the time the last thread with 36 * tsk->mm == mm exits. 37 * 38 * As side note: the pages freed after ->release returns could 39 * be immediately reallocated by the gart at an alias physical 40 * address with a different cache model, so if ->release isn't 41 * implemented because all _software_ driven memory accesses 42 * through the secondary mmu are terminated by the time the 43 * last thread of this mm quits, you've also to be sure that 44 * speculative _hardware_ operations can't allocate dirty 45 * cachelines in the cpu that could not be snooped and made 46 * coherent with the other read and write operations happening 47 * through the gart alias address, so leading to memory 48 * corruption. 49 */ 50 void (*release)(struct mmu_notifier *mn, 51 struct mm_struct *mm); 52 53 /* 54 * clear_flush_young is called after the VM is 55 * test-and-clearing the young/accessed bitflag in the 56 * pte. This way the VM will provide proper aging to the 57 * accesses to the page through the secondary MMUs and not 58 * only to the ones through the Linux pte. 59 */ 60 int (*clear_flush_young)(struct mmu_notifier *mn, 61 struct mm_struct *mm, 62 unsigned long address); 63 64 /* 65 * change_pte is called in cases that pte mapping to page is changed: 66 * for example, when ksm remaps pte to point to a new shared page. 67 */ 68 void (*change_pte)(struct mmu_notifier *mn, 69 struct mm_struct *mm, 70 unsigned long address, 71 pte_t pte); 72 73 /* 74 * Before this is invoked any secondary MMU is still ok to 75 * read/write to the page previously pointed to by the Linux 76 * pte because the page hasn't been freed yet and it won't be 77 * freed until this returns. If required set_page_dirty has to 78 * be called internally to this method. 79 */ 80 void (*invalidate_page)(struct mmu_notifier *mn, 81 struct mm_struct *mm, 82 unsigned long address); 83 84 /* 85 * invalidate_range_start() and invalidate_range_end() must be 86 * paired and are called only when the mmap_sem and/or the 87 * locks protecting the reverse maps are held. The subsystem 88 * must guarantee that no additional references are taken to 89 * the pages in the range established between the call to 90 * invalidate_range_start() and the matching call to 91 * invalidate_range_end(). 92 * 93 * Invalidation of multiple concurrent ranges may be 94 * optionally permitted by the driver. Either way the 95 * establishment of sptes is forbidden in the range passed to 96 * invalidate_range_begin/end for the whole duration of the 97 * invalidate_range_begin/end critical section. 98 * 99 * invalidate_range_start() is called when all pages in the 100 * range are still mapped and have at least a refcount of one. 101 * 102 * invalidate_range_end() is called when all pages in the 103 * range have been unmapped and the pages have been freed by 104 * the VM. 105 * 106 * The VM will remove the page table entries and potentially 107 * the page between invalidate_range_start() and 108 * invalidate_range_end(). If the page must not be freed 109 * because of pending I/O or other circumstances then the 110 * invalidate_range_start() callback (or the initial mapping 111 * by the driver) must make sure that the refcount is kept 112 * elevated. 113 * 114 * If the driver increases the refcount when the pages are 115 * initially mapped into an address space then either 116 * invalidate_range_start() or invalidate_range_end() may 117 * decrease the refcount. If the refcount is decreased on 118 * invalidate_range_start() then the VM can free pages as page 119 * table entries are removed. If the refcount is only 120 * droppped on invalidate_range_end() then the driver itself 121 * will drop the last refcount but it must take care to flush 122 * any secondary tlb before doing the final free on the 123 * page. Pages will no longer be referenced by the linux 124 * address space but may still be referenced by sptes until 125 * the last refcount is dropped. 126 */ 127 void (*invalidate_range_start)(struct mmu_notifier *mn, 128 struct mm_struct *mm, 129 unsigned long start, unsigned long end); 130 void (*invalidate_range_end)(struct mmu_notifier *mn, 131 struct mm_struct *mm, 132 unsigned long start, unsigned long end); 133 }; 134 135 /* 136 * The notifier chains are protected by mmap_sem and/or the reverse map 137 * semaphores. Notifier chains are only changed when all reverse maps and 138 * the mmap_sem locks are taken. 139 * 140 * Therefore notifier chains can only be traversed when either 141 * 142 * 1. mmap_sem is held. 143 * 2. One of the reverse map locks is held (i_mmap_lock or anon_vma->lock). 144 * 3. No other concurrent thread can access the list (release) 145 */ 146 struct mmu_notifier { 147 struct hlist_node hlist; 148 const struct mmu_notifier_ops *ops; 149 }; 150 151 static inline int mm_has_notifiers(struct mm_struct *mm) 152 { 153 return unlikely(mm->mmu_notifier_mm); 154 } 155 156 extern int mmu_notifier_register(struct mmu_notifier *mn, 157 struct mm_struct *mm); 158 extern int __mmu_notifier_register(struct mmu_notifier *mn, 159 struct mm_struct *mm); 160 extern void mmu_notifier_unregister(struct mmu_notifier *mn, 161 struct mm_struct *mm); 162 extern void __mmu_notifier_mm_destroy(struct mm_struct *mm); 163 extern void __mmu_notifier_release(struct mm_struct *mm); 164 extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm, 165 unsigned long address); 166 extern void __mmu_notifier_change_pte(struct mm_struct *mm, 167 unsigned long address, pte_t pte); 168 extern void __mmu_notifier_invalidate_page(struct mm_struct *mm, 169 unsigned long address); 170 extern void __mmu_notifier_invalidate_range_start(struct mm_struct *mm, 171 unsigned long start, unsigned long end); 172 extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm, 173 unsigned long start, unsigned long end); 174 175 static inline void mmu_notifier_release(struct mm_struct *mm) 176 { 177 if (mm_has_notifiers(mm)) 178 __mmu_notifier_release(mm); 179 } 180 181 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm, 182 unsigned long address) 183 { 184 if (mm_has_notifiers(mm)) 185 return __mmu_notifier_clear_flush_young(mm, address); 186 return 0; 187 } 188 189 static inline void mmu_notifier_change_pte(struct mm_struct *mm, 190 unsigned long address, pte_t pte) 191 { 192 if (mm_has_notifiers(mm)) 193 __mmu_notifier_change_pte(mm, address, pte); 194 } 195 196 static inline void mmu_notifier_invalidate_page(struct mm_struct *mm, 197 unsigned long address) 198 { 199 if (mm_has_notifiers(mm)) 200 __mmu_notifier_invalidate_page(mm, address); 201 } 202 203 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm, 204 unsigned long start, unsigned long end) 205 { 206 if (mm_has_notifiers(mm)) 207 __mmu_notifier_invalidate_range_start(mm, start, end); 208 } 209 210 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm, 211 unsigned long start, unsigned long end) 212 { 213 if (mm_has_notifiers(mm)) 214 __mmu_notifier_invalidate_range_end(mm, start, end); 215 } 216 217 static inline void mmu_notifier_mm_init(struct mm_struct *mm) 218 { 219 mm->mmu_notifier_mm = NULL; 220 } 221 222 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm) 223 { 224 if (mm_has_notifiers(mm)) 225 __mmu_notifier_mm_destroy(mm); 226 } 227 228 /* 229 * These two macros will sometime replace ptep_clear_flush. 230 * ptep_clear_flush is impleemnted as macro itself, so this also is 231 * implemented as a macro until ptep_clear_flush will converted to an 232 * inline function, to diminish the risk of compilation failure. The 233 * invalidate_page method over time can be moved outside the PT lock 234 * and these two macros can be later removed. 235 */ 236 #define ptep_clear_flush_notify(__vma, __address, __ptep) \ 237 ({ \ 238 pte_t __pte; \ 239 struct vm_area_struct *___vma = __vma; \ 240 unsigned long ___address = __address; \ 241 __pte = ptep_clear_flush(___vma, ___address, __ptep); \ 242 mmu_notifier_invalidate_page(___vma->vm_mm, ___address); \ 243 __pte; \ 244 }) 245 246 #define ptep_clear_flush_young_notify(__vma, __address, __ptep) \ 247 ({ \ 248 int __young; \ 249 struct vm_area_struct *___vma = __vma; \ 250 unsigned long ___address = __address; \ 251 __young = ptep_clear_flush_young(___vma, ___address, __ptep); \ 252 __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \ 253 ___address); \ 254 __young; \ 255 }) 256 257 #define set_pte_at_notify(__mm, __address, __ptep, __pte) \ 258 ({ \ 259 struct mm_struct *___mm = __mm; \ 260 unsigned long ___address = __address; \ 261 pte_t ___pte = __pte; \ 262 \ 263 set_pte_at(___mm, ___address, __ptep, ___pte); \ 264 mmu_notifier_change_pte(___mm, ___address, ___pte); \ 265 }) 266 267 #else /* CONFIG_MMU_NOTIFIER */ 268 269 static inline void mmu_notifier_release(struct mm_struct *mm) 270 { 271 } 272 273 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm, 274 unsigned long address) 275 { 276 return 0; 277 } 278 279 static inline void mmu_notifier_change_pte(struct mm_struct *mm, 280 unsigned long address, pte_t pte) 281 { 282 } 283 284 static inline void mmu_notifier_invalidate_page(struct mm_struct *mm, 285 unsigned long address) 286 { 287 } 288 289 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm, 290 unsigned long start, unsigned long end) 291 { 292 } 293 294 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm, 295 unsigned long start, unsigned long end) 296 { 297 } 298 299 static inline void mmu_notifier_mm_init(struct mm_struct *mm) 300 { 301 } 302 303 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm) 304 { 305 } 306 307 #define ptep_clear_flush_young_notify ptep_clear_flush_young 308 #define ptep_clear_flush_notify ptep_clear_flush 309 #define set_pte_at_notify set_pte_at 310 311 #endif /* CONFIG_MMU_NOTIFIER */ 312 313 #endif /* _LINUX_MMU_NOTIFIER_H */ 314