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