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 /* 210 * This is called when relaxing access to a PTE. It's also called in the page 211 * fault path when we don't hit any of the major fault cases, ie, a minor 212 * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have 213 * handled those two for us, we additionally deal with missing execute 214 * permission here on some processors 215 */ 216 int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, 217 pte_t *ptep, pte_t entry, int dirty) 218 { 219 int changed; 220 entry = set_access_flags_filter(entry, vma, dirty); 221 changed = !pte_same(*(ptep), entry); 222 if (changed) { 223 assert_pte_locked(vma->vm_mm, address); 224 __ptep_set_access_flags(vma, ptep, entry, 225 address, mmu_virtual_psize); 226 } 227 return changed; 228 } 229 230 #ifdef CONFIG_HUGETLB_PAGE 231 int huge_ptep_set_access_flags(struct vm_area_struct *vma, 232 unsigned long addr, pte_t *ptep, 233 pte_t pte, int dirty) 234 { 235 #ifdef HUGETLB_NEED_PRELOAD 236 /* 237 * The "return 1" forces a call of update_mmu_cache, which will write a 238 * TLB entry. Without this, platforms that don't do a write of the TLB 239 * entry in the TLB miss handler asm will fault ad infinitum. 240 */ 241 ptep_set_access_flags(vma, addr, ptep, pte, dirty); 242 return 1; 243 #else 244 int changed, psize; 245 246 pte = set_access_flags_filter(pte, vma, dirty); 247 changed = !pte_same(*(ptep), pte); 248 if (changed) { 249 250 #ifdef CONFIG_PPC_BOOK3S_64 251 struct hstate *h = hstate_vma(vma); 252 253 psize = hstate_get_psize(h); 254 #ifdef CONFIG_DEBUG_VM 255 assert_spin_locked(huge_pte_lockptr(h, vma->vm_mm, ptep)); 256 #endif 257 258 #else 259 /* 260 * Not used on non book3s64 platforms. 261 * 8xx compares it with mmu_virtual_psize to 262 * know if it is a huge page or not. 263 */ 264 psize = MMU_PAGE_COUNT; 265 #endif 266 __ptep_set_access_flags(vma, ptep, pte, addr, psize); 267 } 268 return changed; 269 #endif 270 } 271 272 #if defined(CONFIG_PPC_8xx) 273 void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte) 274 { 275 pmd_t *pmd = pmd_off(mm, addr); 276 pte_basic_t val; 277 pte_basic_t *entry = (pte_basic_t *)ptep; 278 int num, i; 279 280 /* 281 * Make sure hardware valid bit is not set. We don't do 282 * tlb flush for this update. 283 */ 284 VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep)); 285 286 pte = set_pte_filter(pte); 287 288 val = pte_val(pte); 289 290 num = number_of_cells_per_pte(pmd, val, 1); 291 292 for (i = 0; i < num; i++, entry++, val += SZ_4K) 293 *entry = val; 294 } 295 #endif 296 #endif /* CONFIG_HUGETLB_PAGE */ 297 298 #ifdef CONFIG_DEBUG_VM 299 void assert_pte_locked(struct mm_struct *mm, unsigned long addr) 300 { 301 pgd_t *pgd; 302 p4d_t *p4d; 303 pud_t *pud; 304 pmd_t *pmd; 305 306 if (mm == &init_mm) 307 return; 308 pgd = mm->pgd + pgd_index(addr); 309 BUG_ON(pgd_none(*pgd)); 310 p4d = p4d_offset(pgd, addr); 311 BUG_ON(p4d_none(*p4d)); 312 pud = pud_offset(p4d, addr); 313 BUG_ON(pud_none(*pud)); 314 pmd = pmd_offset(pud, addr); 315 /* 316 * khugepaged to collapse normal pages to hugepage, first set 317 * pmd to none to force page fault/gup to take mmap_lock. After 318 * pmd is set to none, we do a pte_clear which does this assertion 319 * so if we find pmd none, return. 320 */ 321 if (pmd_none(*pmd)) 322 return; 323 BUG_ON(!pmd_present(*pmd)); 324 assert_spin_locked(pte_lockptr(mm, pmd)); 325 } 326 #endif /* CONFIG_DEBUG_VM */ 327 328 unsigned long vmalloc_to_phys(void *va) 329 { 330 unsigned long pfn = vmalloc_to_pfn(va); 331 332 BUG_ON(!pfn); 333 return __pa(pfn_to_kaddr(pfn)) + offset_in_page(va); 334 } 335 EXPORT_SYMBOL_GPL(vmalloc_to_phys); 336 337 /* 338 * We have 4 cases for pgds and pmds: 339 * (1) invalid (all zeroes) 340 * (2) pointer to next table, as normal; bottom 6 bits == 0 341 * (3) leaf pte for huge page _PAGE_PTE set 342 * (4) hugepd pointer, _PAGE_PTE = 0 and bits [2..6] indicate size of table 343 * 344 * So long as we atomically load page table pointers we are safe against teardown, 345 * we can follow the address down to the the page and take a ref on it. 346 * This function need to be called with interrupts disabled. We use this variant 347 * when we have MSR[EE] = 0 but the paca->irq_soft_mask = IRQS_ENABLED 348 */ 349 pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, 350 bool *is_thp, unsigned *hpage_shift) 351 { 352 pgd_t *pgdp; 353 p4d_t p4d, *p4dp; 354 pud_t pud, *pudp; 355 pmd_t pmd, *pmdp; 356 pte_t *ret_pte; 357 hugepd_t *hpdp = NULL; 358 unsigned pdshift; 359 360 if (hpage_shift) 361 *hpage_shift = 0; 362 363 if (is_thp) 364 *is_thp = false; 365 366 /* 367 * Always operate on the local stack value. This make sure the 368 * value don't get updated by a parallel THP split/collapse, 369 * page fault or a page unmap. The return pte_t * is still not 370 * stable. So should be checked there for above conditions. 371 * Top level is an exception because it is folded into p4d. 372 */ 373 pgdp = pgdir + pgd_index(ea); 374 p4dp = p4d_offset(pgdp, ea); 375 p4d = READ_ONCE(*p4dp); 376 pdshift = P4D_SHIFT; 377 378 if (p4d_none(p4d)) 379 return NULL; 380 381 if (p4d_is_leaf(p4d)) { 382 ret_pte = (pte_t *)p4dp; 383 goto out; 384 } 385 386 if (is_hugepd(__hugepd(p4d_val(p4d)))) { 387 hpdp = (hugepd_t *)&p4d; 388 goto out_huge; 389 } 390 391 /* 392 * Even if we end up with an unmap, the pgtable will not 393 * be freed, because we do an rcu free and here we are 394 * irq disabled 395 */ 396 pdshift = PUD_SHIFT; 397 pudp = pud_offset(&p4d, ea); 398 pud = READ_ONCE(*pudp); 399 400 if (pud_none(pud)) 401 return NULL; 402 403 if (pud_is_leaf(pud)) { 404 ret_pte = (pte_t *)pudp; 405 goto out; 406 } 407 408 if (is_hugepd(__hugepd(pud_val(pud)))) { 409 hpdp = (hugepd_t *)&pud; 410 goto out_huge; 411 } 412 413 pdshift = PMD_SHIFT; 414 pmdp = pmd_offset(&pud, ea); 415 pmd = READ_ONCE(*pmdp); 416 417 /* 418 * A hugepage collapse is captured by this condition, see 419 * pmdp_collapse_flush. 420 */ 421 if (pmd_none(pmd)) 422 return NULL; 423 424 #ifdef CONFIG_PPC_BOOK3S_64 425 /* 426 * A hugepage split is captured by this condition, see 427 * pmdp_invalidate. 428 * 429 * Huge page modification can be caught here too. 430 */ 431 if (pmd_is_serializing(pmd)) 432 return NULL; 433 #endif 434 435 if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) { 436 if (is_thp) 437 *is_thp = true; 438 ret_pte = (pte_t *)pmdp; 439 goto out; 440 } 441 442 if (pmd_is_leaf(pmd)) { 443 ret_pte = (pte_t *)pmdp; 444 goto out; 445 } 446 447 if (is_hugepd(__hugepd(pmd_val(pmd)))) { 448 hpdp = (hugepd_t *)&pmd; 449 goto out_huge; 450 } 451 452 return pte_offset_kernel(&pmd, ea); 453 454 out_huge: 455 if (!hpdp) 456 return NULL; 457 458 ret_pte = hugepte_offset(*hpdp, ea, pdshift); 459 pdshift = hugepd_shift(*hpdp); 460 out: 461 if (hpage_shift) 462 *hpage_shift = pdshift; 463 return ret_pte; 464 } 465 EXPORT_SYMBOL_GPL(__find_linux_pte); 466