1 /* 2 * IA-32 Huge TLB Page Support for Kernel. 3 * 4 * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com> 5 */ 6 7 #include <linux/init.h> 8 #include <linux/fs.h> 9 #include <linux/mm.h> 10 #include <linux/hugetlb.h> 11 #include <linux/pagemap.h> 12 #include <linux/slab.h> 13 #include <linux/err.h> 14 #include <linux/sysctl.h> 15 #include <asm/mman.h> 16 #include <asm/tlb.h> 17 #include <asm/tlbflush.h> 18 #include <asm/pgalloc.h> 19 20 static unsigned long page_table_shareable(struct vm_area_struct *svma, 21 struct vm_area_struct *vma, 22 unsigned long addr, pgoff_t idx) 23 { 24 unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) + 25 svma->vm_start; 26 unsigned long sbase = saddr & PUD_MASK; 27 unsigned long s_end = sbase + PUD_SIZE; 28 29 /* 30 * match the virtual addresses, permission and the alignment of the 31 * page table page. 32 */ 33 if (pmd_index(addr) != pmd_index(saddr) || 34 vma->vm_flags != svma->vm_flags || 35 sbase < svma->vm_start || svma->vm_end < s_end) 36 return 0; 37 38 return saddr; 39 } 40 41 static int vma_shareable(struct vm_area_struct *vma, unsigned long addr) 42 { 43 unsigned long base = addr & PUD_MASK; 44 unsigned long end = base + PUD_SIZE; 45 46 /* 47 * check on proper vm_flags and page table alignment 48 */ 49 if (vma->vm_flags & VM_MAYSHARE && 50 vma->vm_start <= base && end <= vma->vm_end) 51 return 1; 52 return 0; 53 } 54 55 /* 56 * search for a shareable pmd page for hugetlb. 57 */ 58 static void huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud) 59 { 60 struct vm_area_struct *vma = find_vma(mm, addr); 61 struct address_space *mapping = vma->vm_file->f_mapping; 62 pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + 63 vma->vm_pgoff; 64 struct prio_tree_iter iter; 65 struct vm_area_struct *svma; 66 unsigned long saddr; 67 pte_t *spte = NULL; 68 69 if (!vma_shareable(vma, addr)) 70 return; 71 72 spin_lock(&mapping->i_mmap_lock); 73 vma_prio_tree_foreach(svma, &iter, &mapping->i_mmap, idx, idx) { 74 if (svma == vma) 75 continue; 76 77 saddr = page_table_shareable(svma, vma, addr, idx); 78 if (saddr) { 79 spte = huge_pte_offset(svma->vm_mm, saddr); 80 if (spte) { 81 get_page(virt_to_page(spte)); 82 break; 83 } 84 } 85 } 86 87 if (!spte) 88 goto out; 89 90 spin_lock(&mm->page_table_lock); 91 if (pud_none(*pud)) 92 pud_populate(mm, pud, (pmd_t *)((unsigned long)spte & PAGE_MASK)); 93 else 94 put_page(virt_to_page(spte)); 95 spin_unlock(&mm->page_table_lock); 96 out: 97 spin_unlock(&mapping->i_mmap_lock); 98 } 99 100 /* 101 * unmap huge page backed by shared pte. 102 * 103 * Hugetlb pte page is ref counted at the time of mapping. If pte is shared 104 * indicated by page_count > 1, unmap is achieved by clearing pud and 105 * decrementing the ref count. If count == 1, the pte page is not shared. 106 * 107 * called with vma->vm_mm->page_table_lock held. 108 * 109 * returns: 1 successfully unmapped a shared pte page 110 * 0 the underlying pte page is not shared, or it is the last user 111 */ 112 int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep) 113 { 114 pgd_t *pgd = pgd_offset(mm, *addr); 115 pud_t *pud = pud_offset(pgd, *addr); 116 117 BUG_ON(page_count(virt_to_page(ptep)) == 0); 118 if (page_count(virt_to_page(ptep)) == 1) 119 return 0; 120 121 pud_clear(pud); 122 put_page(virt_to_page(ptep)); 123 *addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE; 124 return 1; 125 } 126 127 pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr) 128 { 129 pgd_t *pgd; 130 pud_t *pud; 131 pte_t *pte = NULL; 132 133 pgd = pgd_offset(mm, addr); 134 pud = pud_alloc(mm, pgd, addr); 135 if (pud) { 136 if (pud_none(*pud)) 137 huge_pmd_share(mm, addr, pud); 138 pte = (pte_t *) pmd_alloc(mm, pud, addr); 139 } 140 BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte)); 141 142 return pte; 143 } 144 145 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr) 146 { 147 pgd_t *pgd; 148 pud_t *pud; 149 pmd_t *pmd = NULL; 150 151 pgd = pgd_offset(mm, addr); 152 if (pgd_present(*pgd)) { 153 pud = pud_offset(pgd, addr); 154 if (pud_present(*pud)) 155 pmd = pmd_offset(pud, addr); 156 } 157 return (pte_t *) pmd; 158 } 159 160 #if 0 /* This is just for testing */ 161 struct page * 162 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write) 163 { 164 unsigned long start = address; 165 int length = 1; 166 int nr; 167 struct page *page; 168 struct vm_area_struct *vma; 169 170 vma = find_vma(mm, addr); 171 if (!vma || !is_vm_hugetlb_page(vma)) 172 return ERR_PTR(-EINVAL); 173 174 pte = huge_pte_offset(mm, address); 175 176 /* hugetlb should be locked, and hence, prefaulted */ 177 WARN_ON(!pte || pte_none(*pte)); 178 179 page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)]; 180 181 WARN_ON(!PageHead(page)); 182 183 return page; 184 } 185 186 int pmd_huge(pmd_t pmd) 187 { 188 return 0; 189 } 190 191 struct page * 192 follow_huge_pmd(struct mm_struct *mm, unsigned long address, 193 pmd_t *pmd, int write) 194 { 195 return NULL; 196 } 197 198 #else 199 200 struct page * 201 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write) 202 { 203 return ERR_PTR(-EINVAL); 204 } 205 206 int pmd_huge(pmd_t pmd) 207 { 208 return !!(pmd_val(pmd) & _PAGE_PSE); 209 } 210 211 struct page * 212 follow_huge_pmd(struct mm_struct *mm, unsigned long address, 213 pmd_t *pmd, int write) 214 { 215 struct page *page; 216 217 page = pte_page(*(pte_t *)pmd); 218 if (page) 219 page += ((address & ~HPAGE_MASK) >> PAGE_SHIFT); 220 return page; 221 } 222 #endif 223 224 /* x86_64 also uses this file */ 225 226 #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA 227 static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file, 228 unsigned long addr, unsigned long len, 229 unsigned long pgoff, unsigned long flags) 230 { 231 struct mm_struct *mm = current->mm; 232 struct vm_area_struct *vma; 233 unsigned long start_addr; 234 235 if (len > mm->cached_hole_size) { 236 start_addr = mm->free_area_cache; 237 } else { 238 start_addr = TASK_UNMAPPED_BASE; 239 mm->cached_hole_size = 0; 240 } 241 242 full_search: 243 addr = ALIGN(start_addr, HPAGE_SIZE); 244 245 for (vma = find_vma(mm, addr); ; vma = vma->vm_next) { 246 /* At this point: (!vma || addr < vma->vm_end). */ 247 if (TASK_SIZE - len < addr) { 248 /* 249 * Start a new search - just in case we missed 250 * some holes. 251 */ 252 if (start_addr != TASK_UNMAPPED_BASE) { 253 start_addr = TASK_UNMAPPED_BASE; 254 mm->cached_hole_size = 0; 255 goto full_search; 256 } 257 return -ENOMEM; 258 } 259 if (!vma || addr + len <= vma->vm_start) { 260 mm->free_area_cache = addr + len; 261 return addr; 262 } 263 if (addr + mm->cached_hole_size < vma->vm_start) 264 mm->cached_hole_size = vma->vm_start - addr; 265 addr = ALIGN(vma->vm_end, HPAGE_SIZE); 266 } 267 } 268 269 static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file, 270 unsigned long addr0, unsigned long len, 271 unsigned long pgoff, unsigned long flags) 272 { 273 struct mm_struct *mm = current->mm; 274 struct vm_area_struct *vma, *prev_vma; 275 unsigned long base = mm->mmap_base, addr = addr0; 276 unsigned long largest_hole = mm->cached_hole_size; 277 int first_time = 1; 278 279 /* don't allow allocations above current base */ 280 if (mm->free_area_cache > base) 281 mm->free_area_cache = base; 282 283 if (len <= largest_hole) { 284 largest_hole = 0; 285 mm->free_area_cache = base; 286 } 287 try_again: 288 /* make sure it can fit in the remaining address space */ 289 if (mm->free_area_cache < len) 290 goto fail; 291 292 /* either no address requested or cant fit in requested address hole */ 293 addr = (mm->free_area_cache - len) & HPAGE_MASK; 294 do { 295 /* 296 * Lookup failure means no vma is above this address, 297 * i.e. return with success: 298 */ 299 if (!(vma = find_vma_prev(mm, addr, &prev_vma))) 300 return addr; 301 302 /* 303 * new region fits between prev_vma->vm_end and 304 * vma->vm_start, use it: 305 */ 306 if (addr + len <= vma->vm_start && 307 (!prev_vma || (addr >= prev_vma->vm_end))) { 308 /* remember the address as a hint for next time */ 309 mm->cached_hole_size = largest_hole; 310 return (mm->free_area_cache = addr); 311 } else { 312 /* pull free_area_cache down to the first hole */ 313 if (mm->free_area_cache == vma->vm_end) { 314 mm->free_area_cache = vma->vm_start; 315 mm->cached_hole_size = largest_hole; 316 } 317 } 318 319 /* remember the largest hole we saw so far */ 320 if (addr + largest_hole < vma->vm_start) 321 largest_hole = vma->vm_start - addr; 322 323 /* try just below the current vma->vm_start */ 324 addr = (vma->vm_start - len) & HPAGE_MASK; 325 } while (len <= vma->vm_start); 326 327 fail: 328 /* 329 * if hint left us with no space for the requested 330 * mapping then try again: 331 */ 332 if (first_time) { 333 mm->free_area_cache = base; 334 largest_hole = 0; 335 first_time = 0; 336 goto try_again; 337 } 338 /* 339 * A failed mmap() very likely causes application failure, 340 * so fall back to the bottom-up function here. This scenario 341 * can happen with large stack limits and large mmap() 342 * allocations. 343 */ 344 mm->free_area_cache = TASK_UNMAPPED_BASE; 345 mm->cached_hole_size = ~0UL; 346 addr = hugetlb_get_unmapped_area_bottomup(file, addr0, 347 len, pgoff, flags); 348 349 /* 350 * Restore the topdown base: 351 */ 352 mm->free_area_cache = base; 353 mm->cached_hole_size = ~0UL; 354 355 return addr; 356 } 357 358 unsigned long 359 hugetlb_get_unmapped_area(struct file *file, unsigned long addr, 360 unsigned long len, unsigned long pgoff, unsigned long flags) 361 { 362 struct mm_struct *mm = current->mm; 363 struct vm_area_struct *vma; 364 365 if (len & ~HPAGE_MASK) 366 return -EINVAL; 367 if (len > TASK_SIZE) 368 return -ENOMEM; 369 370 if (flags & MAP_FIXED) { 371 if (prepare_hugepage_range(addr, len)) 372 return -EINVAL; 373 return addr; 374 } 375 376 if (addr) { 377 addr = ALIGN(addr, HPAGE_SIZE); 378 vma = find_vma(mm, addr); 379 if (TASK_SIZE - len >= addr && 380 (!vma || addr + len <= vma->vm_start)) 381 return addr; 382 } 383 if (mm->get_unmapped_area == arch_get_unmapped_area) 384 return hugetlb_get_unmapped_area_bottomup(file, addr, len, 385 pgoff, flags); 386 else 387 return hugetlb_get_unmapped_area_topdown(file, addr, len, 388 pgoff, flags); 389 } 390 391 #endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/ 392 393