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 /* Add the pte bit when trying to set a pte */ 188 pte = pte_mkpte(pte); 189 190 /* Note: mm->context.id might not yet have been assigned as 191 * this context might not have been activated yet when this 192 * is called. 193 */ 194 pte = set_pte_filter(pte); 195 196 /* Perform the setting of the PTE */ 197 __set_pte_at(mm, addr, ptep, pte, 0); 198 } 199 200 /* 201 * This is called when relaxing access to a PTE. It's also called in the page 202 * fault path when we don't hit any of the major fault cases, ie, a minor 203 * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have 204 * handled those two for us, we additionally deal with missing execute 205 * permission here on some processors 206 */ 207 int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, 208 pte_t *ptep, pte_t entry, int dirty) 209 { 210 int changed; 211 entry = set_access_flags_filter(entry, vma, dirty); 212 changed = !pte_same(*(ptep), entry); 213 if (changed) { 214 assert_pte_locked(vma->vm_mm, address); 215 __ptep_set_access_flags(vma, ptep, entry, 216 address, mmu_virtual_psize); 217 } 218 return changed; 219 } 220 221 #ifdef CONFIG_HUGETLB_PAGE 222 int huge_ptep_set_access_flags(struct vm_area_struct *vma, 223 unsigned long addr, pte_t *ptep, 224 pte_t pte, int dirty) 225 { 226 #ifdef HUGETLB_NEED_PRELOAD 227 /* 228 * The "return 1" forces a call of update_mmu_cache, which will write a 229 * TLB entry. Without this, platforms that don't do a write of the TLB 230 * entry in the TLB miss handler asm will fault ad infinitum. 231 */ 232 ptep_set_access_flags(vma, addr, ptep, pte, dirty); 233 return 1; 234 #else 235 int changed, psize; 236 237 pte = set_access_flags_filter(pte, vma, dirty); 238 changed = !pte_same(*(ptep), pte); 239 if (changed) { 240 241 #ifdef CONFIG_PPC_BOOK3S_64 242 struct hstate *h = hstate_vma(vma); 243 244 psize = hstate_get_psize(h); 245 #ifdef CONFIG_DEBUG_VM 246 assert_spin_locked(huge_pte_lockptr(h, vma->vm_mm, ptep)); 247 #endif 248 249 #else 250 /* 251 * Not used on non book3s64 platforms. 252 * 8xx compares it with mmu_virtual_psize to 253 * know if it is a huge page or not. 254 */ 255 psize = MMU_PAGE_COUNT; 256 #endif 257 __ptep_set_access_flags(vma, ptep, pte, addr, psize); 258 } 259 return changed; 260 #endif 261 } 262 263 #if defined(CONFIG_PPC_8xx) 264 void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte) 265 { 266 pmd_t *pmd = pmd_off(mm, addr); 267 pte_basic_t val; 268 pte_basic_t *entry = &ptep->pte; 269 int num = is_hugepd(*((hugepd_t *)pmd)) ? 1 : SZ_512K / SZ_4K; 270 int i; 271 272 /* 273 * Make sure hardware valid bit is not set. We don't do 274 * tlb flush for this update. 275 */ 276 VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep)); 277 278 pte = pte_mkpte(pte); 279 280 pte = set_pte_filter(pte); 281 282 val = pte_val(pte); 283 for (i = 0; i < num; i++, entry++, val += SZ_4K) 284 *entry = val; 285 } 286 #endif 287 #endif /* CONFIG_HUGETLB_PAGE */ 288 289 #ifdef CONFIG_DEBUG_VM 290 void assert_pte_locked(struct mm_struct *mm, unsigned long addr) 291 { 292 pgd_t *pgd; 293 p4d_t *p4d; 294 pud_t *pud; 295 pmd_t *pmd; 296 297 if (mm == &init_mm) 298 return; 299 pgd = mm->pgd + pgd_index(addr); 300 BUG_ON(pgd_none(*pgd)); 301 p4d = p4d_offset(pgd, addr); 302 BUG_ON(p4d_none(*p4d)); 303 pud = pud_offset(p4d, addr); 304 BUG_ON(pud_none(*pud)); 305 pmd = pmd_offset(pud, addr); 306 /* 307 * khugepaged to collapse normal pages to hugepage, first set 308 * pmd to none to force page fault/gup to take mmap_lock. After 309 * pmd is set to none, we do a pte_clear which does this assertion 310 * so if we find pmd none, return. 311 */ 312 if (pmd_none(*pmd)) 313 return; 314 BUG_ON(!pmd_present(*pmd)); 315 assert_spin_locked(pte_lockptr(mm, pmd)); 316 } 317 #endif /* CONFIG_DEBUG_VM */ 318 319 unsigned long vmalloc_to_phys(void *va) 320 { 321 unsigned long pfn = vmalloc_to_pfn(va); 322 323 BUG_ON(!pfn); 324 return __pa(pfn_to_kaddr(pfn)) + offset_in_page(va); 325 } 326 EXPORT_SYMBOL_GPL(vmalloc_to_phys); 327 328 /* 329 * We have 4 cases for pgds and pmds: 330 * (1) invalid (all zeroes) 331 * (2) pointer to next table, as normal; bottom 6 bits == 0 332 * (3) leaf pte for huge page _PAGE_PTE set 333 * (4) hugepd pointer, _PAGE_PTE = 0 and bits [2..6] indicate size of table 334 * 335 * So long as we atomically load page table pointers we are safe against teardown, 336 * we can follow the address down to the the page and take a ref on it. 337 * This function need to be called with interrupts disabled. We use this variant 338 * when we have MSR[EE] = 0 but the paca->irq_soft_mask = IRQS_ENABLED 339 */ 340 pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, 341 bool *is_thp, unsigned *hpage_shift) 342 { 343 pgd_t *pgdp; 344 p4d_t p4d, *p4dp; 345 pud_t pud, *pudp; 346 pmd_t pmd, *pmdp; 347 pte_t *ret_pte; 348 hugepd_t *hpdp = NULL; 349 unsigned pdshift; 350 351 if (hpage_shift) 352 *hpage_shift = 0; 353 354 if (is_thp) 355 *is_thp = false; 356 357 /* 358 * Always operate on the local stack value. This make sure the 359 * value don't get updated by a parallel THP split/collapse, 360 * page fault or a page unmap. The return pte_t * is still not 361 * stable. So should be checked there for above conditions. 362 * Top level is an exception because it is folded into p4d. 363 */ 364 pgdp = pgdir + pgd_index(ea); 365 p4dp = p4d_offset(pgdp, ea); 366 p4d = READ_ONCE(*p4dp); 367 pdshift = P4D_SHIFT; 368 369 if (p4d_none(p4d)) 370 return NULL; 371 372 if (p4d_is_leaf(p4d)) { 373 ret_pte = (pte_t *)p4dp; 374 goto out; 375 } 376 377 if (is_hugepd(__hugepd(p4d_val(p4d)))) { 378 hpdp = (hugepd_t *)&p4d; 379 goto out_huge; 380 } 381 382 /* 383 * Even if we end up with an unmap, the pgtable will not 384 * be freed, because we do an rcu free and here we are 385 * irq disabled 386 */ 387 pdshift = PUD_SHIFT; 388 pudp = pud_offset(&p4d, ea); 389 pud = READ_ONCE(*pudp); 390 391 if (pud_none(pud)) 392 return NULL; 393 394 if (pud_is_leaf(pud)) { 395 ret_pte = (pte_t *)pudp; 396 goto out; 397 } 398 399 if (is_hugepd(__hugepd(pud_val(pud)))) { 400 hpdp = (hugepd_t *)&pud; 401 goto out_huge; 402 } 403 404 pdshift = PMD_SHIFT; 405 pmdp = pmd_offset(&pud, ea); 406 pmd = READ_ONCE(*pmdp); 407 408 /* 409 * A hugepage collapse is captured by this condition, see 410 * pmdp_collapse_flush. 411 */ 412 if (pmd_none(pmd)) 413 return NULL; 414 415 #ifdef CONFIG_PPC_BOOK3S_64 416 /* 417 * A hugepage split is captured by this condition, see 418 * pmdp_invalidate. 419 * 420 * Huge page modification can be caught here too. 421 */ 422 if (pmd_is_serializing(pmd)) 423 return NULL; 424 #endif 425 426 if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) { 427 if (is_thp) 428 *is_thp = true; 429 ret_pte = (pte_t *)pmdp; 430 goto out; 431 } 432 433 if (pmd_is_leaf(pmd)) { 434 ret_pte = (pte_t *)pmdp; 435 goto out; 436 } 437 438 if (is_hugepd(__hugepd(pmd_val(pmd)))) { 439 hpdp = (hugepd_t *)&pmd; 440 goto out_huge; 441 } 442 443 return pte_offset_kernel(&pmd, ea); 444 445 out_huge: 446 if (!hpdp) 447 return NULL; 448 449 ret_pte = hugepte_offset(*hpdp, ea, pdshift); 450 pdshift = hugepd_shift(*hpdp); 451 out: 452 if (hpage_shift) 453 *hpage_shift = pdshift; 454 return ret_pte; 455 } 456 EXPORT_SYMBOL_GPL(__find_linux_pte); 457