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) 50 { 51 52 if (pte_present(pte) && !pte_special(pte)) { 53 if (pte_ci(pte)) 54 return 0; 55 if (pte_user(pte)) 56 return 1; 57 } 58 return 0; 59 } 60 61 static struct page *maybe_pte_to_page(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; 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) 83 { 84 pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS); 85 if (pte_looks_normal(pte) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) || 86 cpu_has_feature(CPU_FTR_NOEXECUTE))) { 87 struct page *pg = maybe_pte_to_page(pte); 88 if (!pg) 89 return pte; 90 if (!test_bit(PG_dcache_clean, &pg->flags)) { 91 flush_dcache_icache_page(pg); 92 set_bit(PG_dcache_clean, &pg->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) { 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 static inline pte_t set_pte_filter(pte_t pte) 109 { 110 struct page *pg; 111 112 if (radix_enabled()) 113 return pte; 114 115 if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) 116 return set_pte_filter_hash(pte); 117 118 /* No exec permission in the first place, move on */ 119 if (!pte_exec(pte) || !pte_looks_normal(pte)) 120 return pte; 121 122 /* If you set _PAGE_EXEC on weird pages you're on your own */ 123 pg = maybe_pte_to_page(pte); 124 if (unlikely(!pg)) 125 return pte; 126 127 /* If the page clean, we move on */ 128 if (test_bit(PG_dcache_clean, &pg->flags)) 129 return pte; 130 131 /* If it's an exec fault, we flush the cache and make it clean */ 132 if (is_exec_fault()) { 133 flush_dcache_icache_page(pg); 134 set_bit(PG_dcache_clean, &pg->flags); 135 return pte; 136 } 137 138 /* Else, we filter out _PAGE_EXEC */ 139 return pte_exprotect(pte); 140 } 141 142 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, 143 int dirty) 144 { 145 struct page *pg; 146 147 if (IS_ENABLED(CONFIG_PPC_BOOK3S_64)) 148 return pte; 149 150 if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) 151 return pte; 152 153 /* So here, we only care about exec faults, as we use them 154 * to recover lost _PAGE_EXEC and perform I$/D$ coherency 155 * if necessary. Also if _PAGE_EXEC is already set, same deal, 156 * we just bail out 157 */ 158 if (dirty || pte_exec(pte) || !is_exec_fault()) 159 return pte; 160 161 #ifdef CONFIG_DEBUG_VM 162 /* So this is an exec fault, _PAGE_EXEC is not set. If it was 163 * an error we would have bailed out earlier in do_page_fault() 164 * but let's make sure of it 165 */ 166 if (WARN_ON(!(vma->vm_flags & VM_EXEC))) 167 return pte; 168 #endif /* CONFIG_DEBUG_VM */ 169 170 /* If you set _PAGE_EXEC on weird pages you're on your own */ 171 pg = maybe_pte_to_page(pte); 172 if (unlikely(!pg)) 173 goto bail; 174 175 /* If the page is already clean, we move on */ 176 if (test_bit(PG_dcache_clean, &pg->flags)) 177 goto bail; 178 179 /* Clean the page and set PG_dcache_clean */ 180 flush_dcache_icache_page(pg); 181 set_bit(PG_dcache_clean, &pg->flags); 182 183 bail: 184 return pte_mkexec(pte); 185 } 186 187 /* 188 * set_pte stores a linux PTE into the linux page table. 189 */ 190 void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, 191 pte_t pte) 192 { 193 /* 194 * Make sure hardware valid bit is not set. We don't do 195 * tlb flush for this update. 196 */ 197 VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep)); 198 199 /* Note: mm->context.id might not yet have been assigned as 200 * this context might not have been activated yet when this 201 * is called. 202 */ 203 pte = set_pte_filter(pte); 204 205 /* Perform the setting of the PTE */ 206 __set_pte_at(mm, addr, ptep, pte, 0); 207 } 208 209 void unmap_kernel_page(unsigned long va) 210 { 211 pmd_t *pmdp = pmd_off_k(va); 212 pte_t *ptep = pte_offset_kernel(pmdp, va); 213 214 pte_clear(&init_mm, va, ptep); 215 flush_tlb_kernel_range(va, va + PAGE_SIZE); 216 } 217 218 /* 219 * This is called when relaxing access to a PTE. It's also called in the page 220 * fault path when we don't hit any of the major fault cases, ie, a minor 221 * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have 222 * handled those two for us, we additionally deal with missing execute 223 * permission here on some processors 224 */ 225 int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, 226 pte_t *ptep, pte_t entry, int dirty) 227 { 228 int changed; 229 entry = set_access_flags_filter(entry, vma, dirty); 230 changed = !pte_same(*(ptep), entry); 231 if (changed) { 232 assert_pte_locked(vma->vm_mm, address); 233 __ptep_set_access_flags(vma, ptep, entry, 234 address, mmu_virtual_psize); 235 } 236 return changed; 237 } 238 239 #ifdef CONFIG_HUGETLB_PAGE 240 int huge_ptep_set_access_flags(struct vm_area_struct *vma, 241 unsigned long addr, pte_t *ptep, 242 pte_t pte, int dirty) 243 { 244 #ifdef HUGETLB_NEED_PRELOAD 245 /* 246 * The "return 1" forces a call of update_mmu_cache, which will write a 247 * TLB entry. Without this, platforms that don't do a write of the TLB 248 * entry in the TLB miss handler asm will fault ad infinitum. 249 */ 250 ptep_set_access_flags(vma, addr, ptep, pte, dirty); 251 return 1; 252 #else 253 int changed, psize; 254 255 pte = set_access_flags_filter(pte, vma, dirty); 256 changed = !pte_same(*(ptep), pte); 257 if (changed) { 258 259 #ifdef CONFIG_PPC_BOOK3S_64 260 struct hstate *h = hstate_vma(vma); 261 262 psize = hstate_get_psize(h); 263 #ifdef CONFIG_DEBUG_VM 264 assert_spin_locked(huge_pte_lockptr(h, vma->vm_mm, ptep)); 265 #endif 266 267 #else 268 /* 269 * Not used on non book3s64 platforms. 270 * 8xx compares it with mmu_virtual_psize to 271 * know if it is a huge page or not. 272 */ 273 psize = MMU_PAGE_COUNT; 274 #endif 275 __ptep_set_access_flags(vma, ptep, pte, addr, psize); 276 } 277 return changed; 278 #endif 279 } 280 281 #if defined(CONFIG_PPC_8xx) 282 void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte) 283 { 284 pmd_t *pmd = pmd_off(mm, addr); 285 pte_basic_t val; 286 pte_basic_t *entry = (pte_basic_t *)ptep; 287 int num, i; 288 289 /* 290 * Make sure hardware valid bit is not set. We don't do 291 * tlb flush for this update. 292 */ 293 VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep)); 294 295 pte = set_pte_filter(pte); 296 297 val = pte_val(pte); 298 299 num = number_of_cells_per_pte(pmd, val, 1); 300 301 for (i = 0; i < num; i++, entry++, val += SZ_4K) 302 *entry = val; 303 } 304 #endif 305 #endif /* CONFIG_HUGETLB_PAGE */ 306 307 #ifdef CONFIG_DEBUG_VM 308 void assert_pte_locked(struct mm_struct *mm, unsigned long addr) 309 { 310 pgd_t *pgd; 311 p4d_t *p4d; 312 pud_t *pud; 313 pmd_t *pmd; 314 315 if (mm == &init_mm) 316 return; 317 pgd = mm->pgd + pgd_index(addr); 318 BUG_ON(pgd_none(*pgd)); 319 p4d = p4d_offset(pgd, addr); 320 BUG_ON(p4d_none(*p4d)); 321 pud = pud_offset(p4d, addr); 322 BUG_ON(pud_none(*pud)); 323 pmd = pmd_offset(pud, addr); 324 /* 325 * khugepaged to collapse normal pages to hugepage, first set 326 * pmd to none to force page fault/gup to take mmap_lock. After 327 * pmd is set to none, we do a pte_clear which does this assertion 328 * so if we find pmd none, return. 329 */ 330 if (pmd_none(*pmd)) 331 return; 332 BUG_ON(!pmd_present(*pmd)); 333 assert_spin_locked(pte_lockptr(mm, pmd)); 334 } 335 #endif /* CONFIG_DEBUG_VM */ 336 337 unsigned long vmalloc_to_phys(void *va) 338 { 339 unsigned long pfn = vmalloc_to_pfn(va); 340 341 BUG_ON(!pfn); 342 return __pa(pfn_to_kaddr(pfn)) + offset_in_page(va); 343 } 344 EXPORT_SYMBOL_GPL(vmalloc_to_phys); 345 346 /* 347 * We have 4 cases for pgds and pmds: 348 * (1) invalid (all zeroes) 349 * (2) pointer to next table, as normal; bottom 6 bits == 0 350 * (3) leaf pte for huge page _PAGE_PTE set 351 * (4) hugepd pointer, _PAGE_PTE = 0 and bits [2..6] indicate size of table 352 * 353 * So long as we atomically load page table pointers we are safe against teardown, 354 * we can follow the address down to the the page and take a ref on it. 355 * This function need to be called with interrupts disabled. We use this variant 356 * when we have MSR[EE] = 0 but the paca->irq_soft_mask = IRQS_ENABLED 357 */ 358 pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, 359 bool *is_thp, unsigned *hpage_shift) 360 { 361 pgd_t *pgdp; 362 p4d_t p4d, *p4dp; 363 pud_t pud, *pudp; 364 pmd_t pmd, *pmdp; 365 pte_t *ret_pte; 366 hugepd_t *hpdp = NULL; 367 unsigned pdshift; 368 369 if (hpage_shift) 370 *hpage_shift = 0; 371 372 if (is_thp) 373 *is_thp = false; 374 375 /* 376 * Always operate on the local stack value. This make sure the 377 * value don't get updated by a parallel THP split/collapse, 378 * page fault or a page unmap. The return pte_t * is still not 379 * stable. So should be checked there for above conditions. 380 * Top level is an exception because it is folded into p4d. 381 */ 382 pgdp = pgdir + pgd_index(ea); 383 p4dp = p4d_offset(pgdp, ea); 384 p4d = READ_ONCE(*p4dp); 385 pdshift = P4D_SHIFT; 386 387 if (p4d_none(p4d)) 388 return NULL; 389 390 if (p4d_is_leaf(p4d)) { 391 ret_pte = (pte_t *)p4dp; 392 goto out; 393 } 394 395 if (is_hugepd(__hugepd(p4d_val(p4d)))) { 396 hpdp = (hugepd_t *)&p4d; 397 goto out_huge; 398 } 399 400 /* 401 * Even if we end up with an unmap, the pgtable will not 402 * be freed, because we do an rcu free and here we are 403 * irq disabled 404 */ 405 pdshift = PUD_SHIFT; 406 pudp = pud_offset(&p4d, ea); 407 pud = READ_ONCE(*pudp); 408 409 if (pud_none(pud)) 410 return NULL; 411 412 if (pud_is_leaf(pud)) { 413 ret_pte = (pte_t *)pudp; 414 goto out; 415 } 416 417 if (is_hugepd(__hugepd(pud_val(pud)))) { 418 hpdp = (hugepd_t *)&pud; 419 goto out_huge; 420 } 421 422 pdshift = PMD_SHIFT; 423 pmdp = pmd_offset(&pud, ea); 424 pmd = READ_ONCE(*pmdp); 425 426 /* 427 * A hugepage collapse is captured by this condition, see 428 * pmdp_collapse_flush. 429 */ 430 if (pmd_none(pmd)) 431 return NULL; 432 433 #ifdef CONFIG_PPC_BOOK3S_64 434 /* 435 * A hugepage split is captured by this condition, see 436 * pmdp_invalidate. 437 * 438 * Huge page modification can be caught here too. 439 */ 440 if (pmd_is_serializing(pmd)) 441 return NULL; 442 #endif 443 444 if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) { 445 if (is_thp) 446 *is_thp = true; 447 ret_pte = (pte_t *)pmdp; 448 goto out; 449 } 450 451 if (pmd_is_leaf(pmd)) { 452 ret_pte = (pte_t *)pmdp; 453 goto out; 454 } 455 456 if (is_hugepd(__hugepd(pmd_val(pmd)))) { 457 hpdp = (hugepd_t *)&pmd; 458 goto out_huge; 459 } 460 461 return pte_offset_kernel(&pmd, ea); 462 463 out_huge: 464 if (!hpdp) 465 return NULL; 466 467 ret_pte = hugepte_offset(*hpdp, ea, pdshift); 468 pdshift = hugepd_shift(*hpdp); 469 out: 470 if (hpage_shift) 471 *hpage_shift = pdshift; 472 return ret_pte; 473 } 474 EXPORT_SYMBOL_GPL(__find_linux_pte); 475