1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * This file contains common routines for dealing with free of page tables 4 * Along with common page table handling code 5 * 6 * Derived from arch/powerpc/mm/tlb_64.c: 7 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) 8 * 9 * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au) 10 * and Cort Dougan (PReP) (cort@cs.nmt.edu) 11 * Copyright (C) 1996 Paul Mackerras 12 * 13 * Derived from "arch/i386/mm/init.c" 14 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 15 * 16 * Dave Engebretsen <engebret@us.ibm.com> 17 * Rework for PPC64 port. 18 */ 19 20 #include <linux/kernel.h> 21 #include <linux/gfp.h> 22 #include <linux/mm.h> 23 #include <linux/percpu.h> 24 #include <linux/hardirq.h> 25 #include <linux/hugetlb.h> 26 #include <asm/tlbflush.h> 27 #include <asm/tlb.h> 28 #include <asm/hugetlb.h> 29 #include <asm/pte-walk.h> 30 31 #ifdef CONFIG_PPC64 32 #define PGD_ALIGN (sizeof(pgd_t) * MAX_PTRS_PER_PGD) 33 #else 34 #define PGD_ALIGN PAGE_SIZE 35 #endif 36 37 pgd_t swapper_pg_dir[MAX_PTRS_PER_PGD] __section(".bss..page_aligned") __aligned(PGD_ALIGN); 38 39 static inline int is_exec_fault(void) 40 { 41 return current->thread.regs && TRAP(current->thread.regs) == 0x400; 42 } 43 44 /* We only try to do i/d cache coherency on stuff that looks like 45 * reasonably "normal" PTEs. We currently require a PTE to be present 46 * and we avoid _PAGE_SPECIAL and cache inhibited pte. We also only do that 47 * on userspace PTEs 48 */ 49 static inline int pte_looks_normal(pte_t pte, unsigned long addr) 50 { 51 52 if (pte_present(pte) && !pte_special(pte)) { 53 if (pte_ci(pte)) 54 return 0; 55 if (!is_kernel_addr(addr)) 56 return 1; 57 } 58 return 0; 59 } 60 61 static struct folio *maybe_pte_to_folio(pte_t pte) 62 { 63 unsigned long pfn = pte_pfn(pte); 64 struct page *page; 65 66 if (unlikely(!pfn_valid(pfn))) 67 return NULL; 68 page = pfn_to_page(pfn); 69 if (PageReserved(page)) 70 return NULL; 71 return page_folio(page); 72 } 73 74 #ifdef CONFIG_PPC_BOOK3S 75 76 /* Server-style MMU handles coherency when hashing if HW exec permission 77 * is supposed per page (currently 64-bit only). If not, then, we always 78 * flush the cache for valid PTEs in set_pte. Embedded CPU without HW exec 79 * support falls into the same category. 80 */ 81 82 static pte_t set_pte_filter_hash(pte_t pte, unsigned long addr) 83 { 84 pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS); 85 if (pte_looks_normal(pte, addr) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) || 86 cpu_has_feature(CPU_FTR_NOEXECUTE))) { 87 struct folio *folio = maybe_pte_to_folio(pte); 88 if (!folio) 89 return pte; 90 if (!test_bit(PG_dcache_clean, &folio->flags)) { 91 flush_dcache_icache_folio(folio); 92 set_bit(PG_dcache_clean, &folio->flags); 93 } 94 } 95 return pte; 96 } 97 98 #else /* CONFIG_PPC_BOOK3S */ 99 100 static pte_t set_pte_filter_hash(pte_t pte, unsigned long addr) { return pte; } 101 102 #endif /* CONFIG_PPC_BOOK3S */ 103 104 /* Embedded type MMU with HW exec support. This is a bit more complicated 105 * as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so 106 * instead we "filter out" the exec permission for non clean pages. 107 * 108 * This is also called once for the folio. So only work with folio->flags here. 109 */ 110 static inline pte_t set_pte_filter(pte_t pte, unsigned long addr) 111 { 112 struct folio *folio; 113 114 if (radix_enabled()) 115 return pte; 116 117 if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) 118 return set_pte_filter_hash(pte, addr); 119 120 /* No exec permission in the first place, move on */ 121 if (!pte_exec(pte) || !pte_looks_normal(pte, addr)) 122 return pte; 123 124 /* If you set _PAGE_EXEC on weird pages you're on your own */ 125 folio = maybe_pte_to_folio(pte); 126 if (unlikely(!folio)) 127 return pte; 128 129 /* If the page clean, we move on */ 130 if (test_bit(PG_dcache_clean, &folio->flags)) 131 return pte; 132 133 /* If it's an exec fault, we flush the cache and make it clean */ 134 if (is_exec_fault()) { 135 flush_dcache_icache_folio(folio); 136 set_bit(PG_dcache_clean, &folio->flags); 137 return pte; 138 } 139 140 /* Else, we filter out _PAGE_EXEC */ 141 return pte_exprotect(pte); 142 } 143 144 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, 145 int dirty) 146 { 147 struct folio *folio; 148 149 if (IS_ENABLED(CONFIG_PPC_BOOK3S_64)) 150 return pte; 151 152 if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) 153 return pte; 154 155 /* So here, we only care about exec faults, as we use them 156 * to recover lost _PAGE_EXEC and perform I$/D$ coherency 157 * if necessary. Also if _PAGE_EXEC is already set, same deal, 158 * we just bail out 159 */ 160 if (dirty || pte_exec(pte) || !is_exec_fault()) 161 return pte; 162 163 #ifdef CONFIG_DEBUG_VM 164 /* So this is an exec fault, _PAGE_EXEC is not set. If it was 165 * an error we would have bailed out earlier in do_page_fault() 166 * but let's make sure of it 167 */ 168 if (WARN_ON(!(vma->vm_flags & VM_EXEC))) 169 return pte; 170 #endif /* CONFIG_DEBUG_VM */ 171 172 /* If you set _PAGE_EXEC on weird pages you're on your own */ 173 folio = maybe_pte_to_folio(pte); 174 if (unlikely(!folio)) 175 goto bail; 176 177 /* If the page is already clean, we move on */ 178 if (test_bit(PG_dcache_clean, &folio->flags)) 179 goto bail; 180 181 /* Clean the page and set PG_dcache_clean */ 182 flush_dcache_icache_folio(folio); 183 set_bit(PG_dcache_clean, &folio->flags); 184 185 bail: 186 return pte_mkexec(pte); 187 } 188 189 /* 190 * set_pte stores a linux PTE into the linux page table. 191 */ 192 void set_ptes(struct mm_struct *mm, unsigned long addr, pte_t *ptep, 193 pte_t pte, unsigned int nr) 194 { 195 196 /* Note: mm->context.id might not yet have been assigned as 197 * this context might not have been activated yet when this 198 * is called. Filter the pte value and use the filtered value 199 * to setup all the ptes in the range. 200 */ 201 pte = set_pte_filter(pte, addr); 202 203 /* 204 * We don't need to call arch_enter/leave_lazy_mmu_mode() 205 * because we expect set_ptes to be only be used on not present 206 * and not hw_valid ptes. Hence there is no translation cache flush 207 * involved that need to be batched. 208 */ 209 for (;;) { 210 211 /* 212 * Make sure hardware valid bit is not set. We don't do 213 * tlb flush for this update. 214 */ 215 VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep)); 216 217 /* Perform the setting of the PTE */ 218 __set_pte_at(mm, addr, ptep, pte, 0); 219 if (--nr == 0) 220 break; 221 ptep++; 222 addr += PAGE_SIZE; 223 pte = pte_next_pfn(pte); 224 } 225 } 226 227 void unmap_kernel_page(unsigned long va) 228 { 229 pmd_t *pmdp = pmd_off_k(va); 230 pte_t *ptep = pte_offset_kernel(pmdp, va); 231 232 pte_clear(&init_mm, va, ptep); 233 flush_tlb_kernel_range(va, va + PAGE_SIZE); 234 } 235 236 /* 237 * This is called when relaxing access to a PTE. It's also called in the page 238 * fault path when we don't hit any of the major fault cases, ie, a minor 239 * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have 240 * handled those two for us, we additionally deal with missing execute 241 * permission here on some processors 242 */ 243 int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, 244 pte_t *ptep, pte_t entry, int dirty) 245 { 246 int changed; 247 entry = set_access_flags_filter(entry, vma, dirty); 248 changed = !pte_same(*(ptep), entry); 249 if (changed) { 250 assert_pte_locked(vma->vm_mm, address); 251 __ptep_set_access_flags(vma, ptep, entry, 252 address, mmu_virtual_psize); 253 } 254 return changed; 255 } 256 257 #ifdef CONFIG_HUGETLB_PAGE 258 int huge_ptep_set_access_flags(struct vm_area_struct *vma, 259 unsigned long addr, pte_t *ptep, 260 pte_t pte, int dirty) 261 { 262 #ifdef HUGETLB_NEED_PRELOAD 263 /* 264 * The "return 1" forces a call of update_mmu_cache, which will write a 265 * TLB entry. Without this, platforms that don't do a write of the TLB 266 * entry in the TLB miss handler asm will fault ad infinitum. 267 */ 268 ptep_set_access_flags(vma, addr, ptep, pte, dirty); 269 return 1; 270 #else 271 int changed, psize; 272 273 pte = set_access_flags_filter(pte, vma, dirty); 274 changed = !pte_same(*(ptep), pte); 275 if (changed) { 276 277 #ifdef CONFIG_PPC_BOOK3S_64 278 struct hstate *h = hstate_vma(vma); 279 280 psize = hstate_get_psize(h); 281 #ifdef CONFIG_DEBUG_VM 282 assert_spin_locked(huge_pte_lockptr(h, vma->vm_mm, ptep)); 283 #endif 284 285 #else 286 /* 287 * Not used on non book3s64 platforms. 288 * 8xx compares it with mmu_virtual_psize to 289 * know if it is a huge page or not. 290 */ 291 psize = MMU_PAGE_COUNT; 292 #endif 293 __ptep_set_access_flags(vma, ptep, pte, addr, psize); 294 } 295 return changed; 296 #endif 297 } 298 299 #if defined(CONFIG_PPC_8xx) 300 void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, 301 pte_t pte, unsigned long sz) 302 { 303 pmd_t *pmd = pmd_off(mm, addr); 304 pte_basic_t val; 305 pte_basic_t *entry = (pte_basic_t *)ptep; 306 int num, i; 307 308 /* 309 * Make sure hardware valid bit is not set. We don't do 310 * tlb flush for this update. 311 */ 312 VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep)); 313 314 pte = set_pte_filter(pte, addr); 315 316 val = pte_val(pte); 317 318 num = number_of_cells_per_pte(pmd, val, 1); 319 320 for (i = 0; i < num; i++, entry++, val += SZ_4K) 321 *entry = val; 322 } 323 #endif 324 #endif /* CONFIG_HUGETLB_PAGE */ 325 326 #ifdef CONFIG_DEBUG_VM 327 void assert_pte_locked(struct mm_struct *mm, unsigned long addr) 328 { 329 pgd_t *pgd; 330 p4d_t *p4d; 331 pud_t *pud; 332 pmd_t *pmd; 333 pte_t *pte; 334 spinlock_t *ptl; 335 336 if (mm == &init_mm) 337 return; 338 pgd = mm->pgd + pgd_index(addr); 339 BUG_ON(pgd_none(*pgd)); 340 p4d = p4d_offset(pgd, addr); 341 BUG_ON(p4d_none(*p4d)); 342 pud = pud_offset(p4d, addr); 343 BUG_ON(pud_none(*pud)); 344 pmd = pmd_offset(pud, addr); 345 /* 346 * khugepaged to collapse normal pages to hugepage, first set 347 * pmd to none to force page fault/gup to take mmap_lock. After 348 * pmd is set to none, we do a pte_clear which does this assertion 349 * so if we find pmd none, return. 350 */ 351 if (pmd_none(*pmd)) 352 return; 353 pte = pte_offset_map_nolock(mm, pmd, addr, &ptl); 354 BUG_ON(!pte); 355 assert_spin_locked(ptl); 356 pte_unmap(pte); 357 } 358 #endif /* CONFIG_DEBUG_VM */ 359 360 unsigned long vmalloc_to_phys(void *va) 361 { 362 unsigned long pfn = vmalloc_to_pfn(va); 363 364 BUG_ON(!pfn); 365 return __pa(pfn_to_kaddr(pfn)) + offset_in_page(va); 366 } 367 EXPORT_SYMBOL_GPL(vmalloc_to_phys); 368 369 /* 370 * We have 4 cases for pgds and pmds: 371 * (1) invalid (all zeroes) 372 * (2) pointer to next table, as normal; bottom 6 bits == 0 373 * (3) leaf pte for huge page _PAGE_PTE set 374 * (4) hugepd pointer, _PAGE_PTE = 0 and bits [2..6] indicate size of table 375 * 376 * So long as we atomically load page table pointers we are safe against teardown, 377 * we can follow the address down to the page and take a ref on it. 378 * This function need to be called with interrupts disabled. We use this variant 379 * when we have MSR[EE] = 0 but the paca->irq_soft_mask = IRQS_ENABLED 380 */ 381 pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, 382 bool *is_thp, unsigned *hpage_shift) 383 { 384 pgd_t *pgdp; 385 p4d_t p4d, *p4dp; 386 pud_t pud, *pudp; 387 pmd_t pmd, *pmdp; 388 pte_t *ret_pte; 389 hugepd_t *hpdp = NULL; 390 unsigned pdshift; 391 392 if (hpage_shift) 393 *hpage_shift = 0; 394 395 if (is_thp) 396 *is_thp = false; 397 398 /* 399 * Always operate on the local stack value. This make sure the 400 * value don't get updated by a parallel THP split/collapse, 401 * page fault or a page unmap. The return pte_t * is still not 402 * stable. So should be checked there for above conditions. 403 * Top level is an exception because it is folded into p4d. 404 */ 405 pgdp = pgdir + pgd_index(ea); 406 p4dp = p4d_offset(pgdp, ea); 407 p4d = READ_ONCE(*p4dp); 408 pdshift = P4D_SHIFT; 409 410 if (p4d_none(p4d)) 411 return NULL; 412 413 if (p4d_leaf(p4d)) { 414 ret_pte = (pte_t *)p4dp; 415 goto out; 416 } 417 418 if (is_hugepd(__hugepd(p4d_val(p4d)))) { 419 hpdp = (hugepd_t *)&p4d; 420 goto out_huge; 421 } 422 423 /* 424 * Even if we end up with an unmap, the pgtable will not 425 * be freed, because we do an rcu free and here we are 426 * irq disabled 427 */ 428 pdshift = PUD_SHIFT; 429 pudp = pud_offset(&p4d, ea); 430 pud = READ_ONCE(*pudp); 431 432 if (pud_none(pud)) 433 return NULL; 434 435 if (pud_leaf(pud)) { 436 ret_pte = (pte_t *)pudp; 437 goto out; 438 } 439 440 if (is_hugepd(__hugepd(pud_val(pud)))) { 441 hpdp = (hugepd_t *)&pud; 442 goto out_huge; 443 } 444 445 pdshift = PMD_SHIFT; 446 pmdp = pmd_offset(&pud, ea); 447 pmd = READ_ONCE(*pmdp); 448 449 /* 450 * A hugepage collapse is captured by this condition, see 451 * pmdp_collapse_flush. 452 */ 453 if (pmd_none(pmd)) 454 return NULL; 455 456 #ifdef CONFIG_PPC_BOOK3S_64 457 /* 458 * A hugepage split is captured by this condition, see 459 * pmdp_invalidate. 460 * 461 * Huge page modification can be caught here too. 462 */ 463 if (pmd_is_serializing(pmd)) 464 return NULL; 465 #endif 466 467 if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) { 468 if (is_thp) 469 *is_thp = true; 470 ret_pte = (pte_t *)pmdp; 471 goto out; 472 } 473 474 if (pmd_leaf(pmd)) { 475 ret_pte = (pte_t *)pmdp; 476 goto out; 477 } 478 479 if (is_hugepd(__hugepd(pmd_val(pmd)))) { 480 hpdp = (hugepd_t *)&pmd; 481 goto out_huge; 482 } 483 484 return pte_offset_kernel(&pmd, ea); 485 486 out_huge: 487 if (!hpdp) 488 return NULL; 489 490 ret_pte = hugepte_offset(*hpdp, ea, pdshift); 491 pdshift = hugepd_shift(*hpdp); 492 out: 493 if (hpage_shift) 494 *hpage_shift = pdshift; 495 return ret_pte; 496 } 497 EXPORT_SYMBOL_GPL(__find_linux_pte); 498 499 /* Note due to the way vm flags are laid out, the bits are XWR */ 500 const pgprot_t protection_map[16] = { 501 [VM_NONE] = PAGE_NONE, 502 [VM_READ] = PAGE_READONLY, 503 [VM_WRITE] = PAGE_COPY, 504 [VM_WRITE | VM_READ] = PAGE_COPY, 505 [VM_EXEC] = PAGE_EXECONLY_X, 506 [VM_EXEC | VM_READ] = PAGE_READONLY_X, 507 [VM_EXEC | VM_WRITE] = PAGE_COPY_X, 508 [VM_EXEC | VM_WRITE | VM_READ] = PAGE_COPY_X, 509 [VM_SHARED] = PAGE_NONE, 510 [VM_SHARED | VM_READ] = PAGE_READONLY, 511 [VM_SHARED | VM_WRITE] = PAGE_SHARED, 512 [VM_SHARED | VM_WRITE | VM_READ] = PAGE_SHARED, 513 [VM_SHARED | VM_EXEC] = PAGE_EXECONLY_X, 514 [VM_SHARED | VM_EXEC | VM_READ] = PAGE_READONLY_X, 515 [VM_SHARED | VM_EXEC | VM_WRITE] = PAGE_SHARED_X, 516 [VM_SHARED | VM_EXEC | VM_WRITE | VM_READ] = PAGE_SHARED_X 517 }; 518 519 #ifndef CONFIG_PPC_BOOK3S_64 520 DECLARE_VM_GET_PAGE_PROT 521 #endif 522