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 30 static inline int is_exec_fault(void) 31 { 32 return current->thread.regs && TRAP(current->thread.regs) == 0x400; 33 } 34 35 /* We only try to do i/d cache coherency on stuff that looks like 36 * reasonably "normal" PTEs. We currently require a PTE to be present 37 * and we avoid _PAGE_SPECIAL and cache inhibited pte. We also only do that 38 * on userspace PTEs 39 */ 40 static inline int pte_looks_normal(pte_t pte) 41 { 42 43 if (pte_present(pte) && !pte_special(pte)) { 44 if (pte_ci(pte)) 45 return 0; 46 if (pte_user(pte)) 47 return 1; 48 } 49 return 0; 50 } 51 52 static struct page *maybe_pte_to_page(pte_t pte) 53 { 54 unsigned long pfn = pte_pfn(pte); 55 struct page *page; 56 57 if (unlikely(!pfn_valid(pfn))) 58 return NULL; 59 page = pfn_to_page(pfn); 60 if (PageReserved(page)) 61 return NULL; 62 return page; 63 } 64 65 #ifdef CONFIG_PPC_BOOK3S 66 67 /* Server-style MMU handles coherency when hashing if HW exec permission 68 * is supposed per page (currently 64-bit only). If not, then, we always 69 * flush the cache for valid PTEs in set_pte. Embedded CPU without HW exec 70 * support falls into the same category. 71 */ 72 73 static pte_t set_pte_filter_hash(pte_t pte) 74 { 75 if (radix_enabled()) 76 return pte; 77 78 pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS); 79 if (pte_looks_normal(pte) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) || 80 cpu_has_feature(CPU_FTR_NOEXECUTE))) { 81 struct page *pg = maybe_pte_to_page(pte); 82 if (!pg) 83 return pte; 84 if (!test_bit(PG_arch_1, &pg->flags)) { 85 flush_dcache_icache_page(pg); 86 set_bit(PG_arch_1, &pg->flags); 87 } 88 } 89 return pte; 90 } 91 92 #else /* CONFIG_PPC_BOOK3S */ 93 94 static pte_t set_pte_filter_hash(pte_t pte) { return pte; } 95 96 #endif /* CONFIG_PPC_BOOK3S */ 97 98 /* Embedded type MMU with HW exec support. This is a bit more complicated 99 * as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so 100 * instead we "filter out" the exec permission for non clean pages. 101 */ 102 static inline pte_t set_pte_filter(pte_t pte) 103 { 104 struct page *pg; 105 106 if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) 107 return set_pte_filter_hash(pte); 108 109 /* No exec permission in the first place, move on */ 110 if (!pte_exec(pte) || !pte_looks_normal(pte)) 111 return pte; 112 113 /* If you set _PAGE_EXEC on weird pages you're on your own */ 114 pg = maybe_pte_to_page(pte); 115 if (unlikely(!pg)) 116 return pte; 117 118 /* If the page clean, we move on */ 119 if (test_bit(PG_arch_1, &pg->flags)) 120 return pte; 121 122 /* If it's an exec fault, we flush the cache and make it clean */ 123 if (is_exec_fault()) { 124 flush_dcache_icache_page(pg); 125 set_bit(PG_arch_1, &pg->flags); 126 return pte; 127 } 128 129 /* Else, we filter out _PAGE_EXEC */ 130 return pte_exprotect(pte); 131 } 132 133 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, 134 int dirty) 135 { 136 struct page *pg; 137 138 if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) 139 return pte; 140 141 /* So here, we only care about exec faults, as we use them 142 * to recover lost _PAGE_EXEC and perform I$/D$ coherency 143 * if necessary. Also if _PAGE_EXEC is already set, same deal, 144 * we just bail out 145 */ 146 if (dirty || pte_exec(pte) || !is_exec_fault()) 147 return pte; 148 149 #ifdef CONFIG_DEBUG_VM 150 /* So this is an exec fault, _PAGE_EXEC is not set. If it was 151 * an error we would have bailed out earlier in do_page_fault() 152 * but let's make sure of it 153 */ 154 if (WARN_ON(!(vma->vm_flags & VM_EXEC))) 155 return pte; 156 #endif /* CONFIG_DEBUG_VM */ 157 158 /* If you set _PAGE_EXEC on weird pages you're on your own */ 159 pg = maybe_pte_to_page(pte); 160 if (unlikely(!pg)) 161 goto bail; 162 163 /* If the page is already clean, we move on */ 164 if (test_bit(PG_arch_1, &pg->flags)) 165 goto bail; 166 167 /* Clean the page and set PG_arch_1 */ 168 flush_dcache_icache_page(pg); 169 set_bit(PG_arch_1, &pg->flags); 170 171 bail: 172 return pte_mkexec(pte); 173 } 174 175 /* 176 * set_pte stores a linux PTE into the linux page table. 177 */ 178 void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, 179 pte_t pte) 180 { 181 /* 182 * Make sure hardware valid bit is not set. We don't do 183 * tlb flush for this update. 184 */ 185 VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep)); 186 187 /* Note: mm->context.id might not yet have been assigned as 188 * this context might not have been activated yet when this 189 * is called. 190 */ 191 pte = set_pte_filter(pte); 192 193 /* Perform the setting of the PTE */ 194 __set_pte_at(mm, addr, ptep, pte, 0); 195 } 196 197 /* 198 * This is called when relaxing access to a PTE. It's also called in the page 199 * fault path when we don't hit any of the major fault cases, ie, a minor 200 * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have 201 * handled those two for us, we additionally deal with missing execute 202 * permission here on some processors 203 */ 204 int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, 205 pte_t *ptep, pte_t entry, int dirty) 206 { 207 int changed; 208 entry = set_access_flags_filter(entry, vma, dirty); 209 changed = !pte_same(*(ptep), entry); 210 if (changed) { 211 assert_pte_locked(vma->vm_mm, address); 212 __ptep_set_access_flags(vma, ptep, entry, 213 address, mmu_virtual_psize); 214 } 215 return changed; 216 } 217 218 #ifdef CONFIG_HUGETLB_PAGE 219 int huge_ptep_set_access_flags(struct vm_area_struct *vma, 220 unsigned long addr, pte_t *ptep, 221 pte_t pte, int dirty) 222 { 223 #ifdef HUGETLB_NEED_PRELOAD 224 /* 225 * The "return 1" forces a call of update_mmu_cache, which will write a 226 * TLB entry. Without this, platforms that don't do a write of the TLB 227 * entry in the TLB miss handler asm will fault ad infinitum. 228 */ 229 ptep_set_access_flags(vma, addr, ptep, pte, dirty); 230 return 1; 231 #else 232 int changed, psize; 233 234 pte = set_access_flags_filter(pte, vma, dirty); 235 changed = !pte_same(*(ptep), pte); 236 if (changed) { 237 238 #ifdef CONFIG_PPC_BOOK3S_64 239 struct hstate *h = hstate_vma(vma); 240 241 psize = hstate_get_psize(h); 242 #ifdef CONFIG_DEBUG_VM 243 assert_spin_locked(huge_pte_lockptr(h, vma->vm_mm, ptep)); 244 #endif 245 246 #else 247 /* 248 * Not used on non book3s64 platforms. 249 * 8xx compares it with mmu_virtual_psize to 250 * know if it is a huge page or not. 251 */ 252 psize = MMU_PAGE_COUNT; 253 #endif 254 __ptep_set_access_flags(vma, ptep, pte, addr, psize); 255 } 256 return changed; 257 #endif 258 } 259 260 #if defined(CONFIG_PPC_8xx) 261 void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte) 262 { 263 pmd_t *pmd = pmd_off(mm, addr); 264 pte_basic_t val; 265 pte_basic_t *entry = &ptep->pte; 266 int num, i; 267 268 /* 269 * Make sure hardware valid bit is not set. We don't do 270 * tlb flush for this update. 271 */ 272 VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep)); 273 274 pte = set_pte_filter(pte); 275 276 val = pte_val(pte); 277 278 num = number_of_cells_per_pte(pmd, val, 1); 279 280 for (i = 0; i < num; i++, entry++, val += SZ_4K) 281 *entry = val; 282 } 283 #endif 284 #endif /* CONFIG_HUGETLB_PAGE */ 285 286 #ifdef CONFIG_DEBUG_VM 287 void assert_pte_locked(struct mm_struct *mm, unsigned long addr) 288 { 289 pgd_t *pgd; 290 p4d_t *p4d; 291 pud_t *pud; 292 pmd_t *pmd; 293 294 if (mm == &init_mm) 295 return; 296 pgd = mm->pgd + pgd_index(addr); 297 BUG_ON(pgd_none(*pgd)); 298 p4d = p4d_offset(pgd, addr); 299 BUG_ON(p4d_none(*p4d)); 300 pud = pud_offset(p4d, addr); 301 BUG_ON(pud_none(*pud)); 302 pmd = pmd_offset(pud, addr); 303 /* 304 * khugepaged to collapse normal pages to hugepage, first set 305 * pmd to none to force page fault/gup to take mmap_lock. After 306 * pmd is set to none, we do a pte_clear which does this assertion 307 * so if we find pmd none, return. 308 */ 309 if (pmd_none(*pmd)) 310 return; 311 BUG_ON(!pmd_present(*pmd)); 312 assert_spin_locked(pte_lockptr(mm, pmd)); 313 } 314 #endif /* CONFIG_DEBUG_VM */ 315 316 unsigned long vmalloc_to_phys(void *va) 317 { 318 unsigned long pfn = vmalloc_to_pfn(va); 319 320 BUG_ON(!pfn); 321 return __pa(pfn_to_kaddr(pfn)) + offset_in_page(va); 322 } 323 EXPORT_SYMBOL_GPL(vmalloc_to_phys); 324 325 /* 326 * We have 4 cases for pgds and pmds: 327 * (1) invalid (all zeroes) 328 * (2) pointer to next table, as normal; bottom 6 bits == 0 329 * (3) leaf pte for huge page _PAGE_PTE set 330 * (4) hugepd pointer, _PAGE_PTE = 0 and bits [2..6] indicate size of table 331 * 332 * So long as we atomically load page table pointers we are safe against teardown, 333 * we can follow the address down to the the page and take a ref on it. 334 * This function need to be called with interrupts disabled. We use this variant 335 * when we have MSR[EE] = 0 but the paca->irq_soft_mask = IRQS_ENABLED 336 */ 337 pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, 338 bool *is_thp, unsigned *hpage_shift) 339 { 340 pgd_t *pgdp; 341 p4d_t p4d, *p4dp; 342 pud_t pud, *pudp; 343 pmd_t pmd, *pmdp; 344 pte_t *ret_pte; 345 hugepd_t *hpdp = NULL; 346 unsigned pdshift; 347 348 if (hpage_shift) 349 *hpage_shift = 0; 350 351 if (is_thp) 352 *is_thp = false; 353 354 /* 355 * Always operate on the local stack value. This make sure the 356 * value don't get updated by a parallel THP split/collapse, 357 * page fault or a page unmap. The return pte_t * is still not 358 * stable. So should be checked there for above conditions. 359 * Top level is an exception because it is folded into p4d. 360 */ 361 pgdp = pgdir + pgd_index(ea); 362 p4dp = p4d_offset(pgdp, ea); 363 p4d = READ_ONCE(*p4dp); 364 pdshift = P4D_SHIFT; 365 366 if (p4d_none(p4d)) 367 return NULL; 368 369 if (p4d_is_leaf(p4d)) { 370 ret_pte = (pte_t *)p4dp; 371 goto out; 372 } 373 374 if (is_hugepd(__hugepd(p4d_val(p4d)))) { 375 hpdp = (hugepd_t *)&p4d; 376 goto out_huge; 377 } 378 379 /* 380 * Even if we end up with an unmap, the pgtable will not 381 * be freed, because we do an rcu free and here we are 382 * irq disabled 383 */ 384 pdshift = PUD_SHIFT; 385 pudp = pud_offset(&p4d, ea); 386 pud = READ_ONCE(*pudp); 387 388 if (pud_none(pud)) 389 return NULL; 390 391 if (pud_is_leaf(pud)) { 392 ret_pte = (pte_t *)pudp; 393 goto out; 394 } 395 396 if (is_hugepd(__hugepd(pud_val(pud)))) { 397 hpdp = (hugepd_t *)&pud; 398 goto out_huge; 399 } 400 401 pdshift = PMD_SHIFT; 402 pmdp = pmd_offset(&pud, ea); 403 pmd = READ_ONCE(*pmdp); 404 405 /* 406 * A hugepage collapse is captured by this condition, see 407 * pmdp_collapse_flush. 408 */ 409 if (pmd_none(pmd)) 410 return NULL; 411 412 #ifdef CONFIG_PPC_BOOK3S_64 413 /* 414 * A hugepage split is captured by this condition, see 415 * pmdp_invalidate. 416 * 417 * Huge page modification can be caught here too. 418 */ 419 if (pmd_is_serializing(pmd)) 420 return NULL; 421 #endif 422 423 if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) { 424 if (is_thp) 425 *is_thp = true; 426 ret_pte = (pte_t *)pmdp; 427 goto out; 428 } 429 430 if (pmd_is_leaf(pmd)) { 431 ret_pte = (pte_t *)pmdp; 432 goto out; 433 } 434 435 if (is_hugepd(__hugepd(pmd_val(pmd)))) { 436 hpdp = (hugepd_t *)&pmd; 437 goto out_huge; 438 } 439 440 return pte_offset_kernel(&pmd, ea); 441 442 out_huge: 443 if (!hpdp) 444 return NULL; 445 446 ret_pte = hugepte_offset(*hpdp, ea, pdshift); 447 pdshift = hugepd_shift(*hpdp); 448 out: 449 if (hpage_shift) 450 *hpage_shift = pdshift; 451 return ret_pte; 452 } 453 EXPORT_SYMBOL_GPL(__find_linux_pte); 454