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/pgalloc.h> 27 #include <asm/tlbflush.h> 28 #include <asm/tlb.h> 29 #include <asm/hugetlb.h> 30 31 static inline int is_exec_fault(void) 32 { 33 return current->thread.regs && TRAP(current->thread.regs) == 0x400; 34 } 35 36 /* We only try to do i/d cache coherency on stuff that looks like 37 * reasonably "normal" PTEs. We currently require a PTE to be present 38 * and we avoid _PAGE_SPECIAL and cache inhibited pte. We also only do that 39 * on userspace PTEs 40 */ 41 static inline int pte_looks_normal(pte_t pte) 42 { 43 44 if (pte_present(pte) && !pte_special(pte)) { 45 if (pte_ci(pte)) 46 return 0; 47 if (pte_user(pte)) 48 return 1; 49 } 50 return 0; 51 } 52 53 static struct page *maybe_pte_to_page(pte_t pte) 54 { 55 unsigned long pfn = pte_pfn(pte); 56 struct page *page; 57 58 if (unlikely(!pfn_valid(pfn))) 59 return NULL; 60 page = pfn_to_page(pfn); 61 if (PageReserved(page)) 62 return NULL; 63 return page; 64 } 65 66 #ifdef CONFIG_PPC_BOOK3S 67 68 /* Server-style MMU handles coherency when hashing if HW exec permission 69 * is supposed per page (currently 64-bit only). If not, then, we always 70 * flush the cache for valid PTEs in set_pte. Embedded CPU without HW exec 71 * support falls into the same category. 72 */ 73 74 static pte_t set_pte_filter_hash(pte_t pte) 75 { 76 if (radix_enabled()) 77 return pte; 78 79 pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS); 80 if (pte_looks_normal(pte) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) || 81 cpu_has_feature(CPU_FTR_NOEXECUTE))) { 82 struct page *pg = maybe_pte_to_page(pte); 83 if (!pg) 84 return pte; 85 if (!test_bit(PG_arch_1, &pg->flags)) { 86 flush_dcache_icache_page(pg); 87 set_bit(PG_arch_1, &pg->flags); 88 } 89 } 90 return pte; 91 } 92 93 #else /* CONFIG_PPC_BOOK3S */ 94 95 static pte_t set_pte_filter_hash(pte_t pte) { return pte; } 96 97 #endif /* CONFIG_PPC_BOOK3S */ 98 99 /* Embedded type MMU with HW exec support. This is a bit more complicated 100 * as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so 101 * instead we "filter out" the exec permission for non clean pages. 102 */ 103 static inline pte_t set_pte_filter(pte_t pte) 104 { 105 struct page *pg; 106 107 if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) 108 return set_pte_filter_hash(pte); 109 110 /* No exec permission in the first place, move on */ 111 if (!pte_exec(pte) || !pte_looks_normal(pte)) 112 return pte; 113 114 /* If you set _PAGE_EXEC on weird pages you're on your own */ 115 pg = maybe_pte_to_page(pte); 116 if (unlikely(!pg)) 117 return pte; 118 119 /* If the page clean, we move on */ 120 if (test_bit(PG_arch_1, &pg->flags)) 121 return pte; 122 123 /* If it's an exec fault, we flush the cache and make it clean */ 124 if (is_exec_fault()) { 125 flush_dcache_icache_page(pg); 126 set_bit(PG_arch_1, &pg->flags); 127 return pte; 128 } 129 130 /* Else, we filter out _PAGE_EXEC */ 131 return pte_exprotect(pte); 132 } 133 134 static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, 135 int dirty) 136 { 137 struct page *pg; 138 139 if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) 140 return pte; 141 142 /* So here, we only care about exec faults, as we use them 143 * to recover lost _PAGE_EXEC and perform I$/D$ coherency 144 * if necessary. Also if _PAGE_EXEC is already set, same deal, 145 * we just bail out 146 */ 147 if (dirty || pte_exec(pte) || !is_exec_fault()) 148 return pte; 149 150 #ifdef CONFIG_DEBUG_VM 151 /* So this is an exec fault, _PAGE_EXEC is not set. If it was 152 * an error we would have bailed out earlier in do_page_fault() 153 * but let's make sure of it 154 */ 155 if (WARN_ON(!(vma->vm_flags & VM_EXEC))) 156 return pte; 157 #endif /* CONFIG_DEBUG_VM */ 158 159 /* If you set _PAGE_EXEC on weird pages you're on your own */ 160 pg = maybe_pte_to_page(pte); 161 if (unlikely(!pg)) 162 goto bail; 163 164 /* If the page is already clean, we move on */ 165 if (test_bit(PG_arch_1, &pg->flags)) 166 goto bail; 167 168 /* Clean the page and set PG_arch_1 */ 169 flush_dcache_icache_page(pg); 170 set_bit(PG_arch_1, &pg->flags); 171 172 bail: 173 return pte_mkexec(pte); 174 } 175 176 /* 177 * set_pte stores a linux PTE into the linux page table. 178 */ 179 void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, 180 pte_t pte) 181 { 182 /* 183 * Make sure hardware valid bit is not set. We don't do 184 * tlb flush for this update. 185 */ 186 VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep)); 187 188 /* Add the pte bit when trying to set a pte */ 189 pte = pte_mkpte(pte); 190 191 /* Note: mm->context.id might not yet have been assigned as 192 * this context might not have been activated yet when this 193 * is called. 194 */ 195 pte = set_pte_filter(pte); 196 197 /* Perform the setting of the PTE */ 198 __set_pte_at(mm, addr, ptep, pte, 0); 199 } 200 201 /* 202 * This is called when relaxing access to a PTE. It's also called in the page 203 * fault path when we don't hit any of the major fault cases, ie, a minor 204 * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have 205 * handled those two for us, we additionally deal with missing execute 206 * permission here on some processors 207 */ 208 int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, 209 pte_t *ptep, pte_t entry, int dirty) 210 { 211 int changed; 212 entry = set_access_flags_filter(entry, vma, dirty); 213 changed = !pte_same(*(ptep), entry); 214 if (changed) { 215 assert_pte_locked(vma->vm_mm, address); 216 __ptep_set_access_flags(vma, ptep, entry, 217 address, mmu_virtual_psize); 218 } 219 return changed; 220 } 221 222 #ifdef CONFIG_HUGETLB_PAGE 223 int huge_ptep_set_access_flags(struct vm_area_struct *vma, 224 unsigned long addr, pte_t *ptep, 225 pte_t pte, int dirty) 226 { 227 #ifdef HUGETLB_NEED_PRELOAD 228 /* 229 * The "return 1" forces a call of update_mmu_cache, which will write a 230 * TLB entry. Without this, platforms that don't do a write of the TLB 231 * entry in the TLB miss handler asm will fault ad infinitum. 232 */ 233 ptep_set_access_flags(vma, addr, ptep, pte, dirty); 234 return 1; 235 #else 236 int changed, psize; 237 238 pte = set_access_flags_filter(pte, vma, dirty); 239 changed = !pte_same(*(ptep), pte); 240 if (changed) { 241 242 #ifdef CONFIG_PPC_BOOK3S_64 243 struct hstate *h = hstate_vma(vma); 244 245 psize = hstate_get_psize(h); 246 #ifdef CONFIG_DEBUG_VM 247 assert_spin_locked(huge_pte_lockptr(h, vma->vm_mm, ptep)); 248 #endif 249 250 #else 251 /* 252 * Not used on non book3s64 platforms. 253 * 8xx compares it with mmu_virtual_psize to 254 * know if it is a huge page or not. 255 */ 256 psize = MMU_PAGE_COUNT; 257 #endif 258 __ptep_set_access_flags(vma, ptep, pte, addr, psize); 259 } 260 return changed; 261 #endif 262 } 263 264 #if defined(CONFIG_PPC_8xx) 265 void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte) 266 { 267 pmd_t *pmd = pmd_off(mm, addr); 268 pte_basic_t val; 269 pte_basic_t *entry = &ptep->pte; 270 int num = is_hugepd(*((hugepd_t *)pmd)) ? 1 : SZ_512K / SZ_4K; 271 int i; 272 273 /* 274 * Make sure hardware valid bit is not set. We don't do 275 * tlb flush for this update. 276 */ 277 VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep)); 278 279 pte = pte_mkpte(pte); 280 281 pte = set_pte_filter(pte); 282 283 val = pte_val(pte); 284 for (i = 0; i < num; i++, entry++, val += SZ_4K) 285 *entry = val; 286 } 287 #endif 288 #endif /* CONFIG_HUGETLB_PAGE */ 289 290 #ifdef CONFIG_DEBUG_VM 291 void assert_pte_locked(struct mm_struct *mm, unsigned long addr) 292 { 293 pgd_t *pgd; 294 p4d_t *p4d; 295 pud_t *pud; 296 pmd_t *pmd; 297 298 if (mm == &init_mm) 299 return; 300 pgd = mm->pgd + pgd_index(addr); 301 BUG_ON(pgd_none(*pgd)); 302 p4d = p4d_offset(pgd, addr); 303 BUG_ON(p4d_none(*p4d)); 304 pud = pud_offset(p4d, addr); 305 BUG_ON(pud_none(*pud)); 306 pmd = pmd_offset(pud, addr); 307 /* 308 * khugepaged to collapse normal pages to hugepage, first set 309 * pmd to none to force page fault/gup to take mmap_lock. After 310 * pmd is set to none, we do a pte_clear which does this assertion 311 * so if we find pmd none, return. 312 */ 313 if (pmd_none(*pmd)) 314 return; 315 BUG_ON(!pmd_present(*pmd)); 316 assert_spin_locked(pte_lockptr(mm, pmd)); 317 } 318 #endif /* CONFIG_DEBUG_VM */ 319 320 unsigned long vmalloc_to_phys(void *va) 321 { 322 unsigned long pfn = vmalloc_to_pfn(va); 323 324 BUG_ON(!pfn); 325 return __pa(pfn_to_kaddr(pfn)) + offset_in_page(va); 326 } 327 EXPORT_SYMBOL_GPL(vmalloc_to_phys); 328 329 /* 330 * We have 4 cases for pgds and pmds: 331 * (1) invalid (all zeroes) 332 * (2) pointer to next table, as normal; bottom 6 bits == 0 333 * (3) leaf pte for huge page _PAGE_PTE set 334 * (4) hugepd pointer, _PAGE_PTE = 0 and bits [2..6] indicate size of table 335 * 336 * So long as we atomically load page table pointers we are safe against teardown, 337 * we can follow the address down to the the page and take a ref on it. 338 * This function need to be called with interrupts disabled. We use this variant 339 * when we have MSR[EE] = 0 but the paca->irq_soft_mask = IRQS_ENABLED 340 */ 341 pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, 342 bool *is_thp, unsigned *hpage_shift) 343 { 344 pgd_t *pgdp; 345 p4d_t p4d, *p4dp; 346 pud_t pud, *pudp; 347 pmd_t pmd, *pmdp; 348 pte_t *ret_pte; 349 hugepd_t *hpdp = NULL; 350 unsigned pdshift; 351 352 if (hpage_shift) 353 *hpage_shift = 0; 354 355 if (is_thp) 356 *is_thp = false; 357 358 /* 359 * Always operate on the local stack value. This make sure the 360 * value don't get updated by a parallel THP split/collapse, 361 * page fault or a page unmap. The return pte_t * is still not 362 * stable. So should be checked there for above conditions. 363 * Top level is an exception because it is folded into p4d. 364 */ 365 pgdp = pgdir + pgd_index(ea); 366 p4dp = p4d_offset(pgdp, ea); 367 p4d = READ_ONCE(*p4dp); 368 pdshift = P4D_SHIFT; 369 370 if (p4d_none(p4d)) 371 return NULL; 372 373 if (p4d_is_leaf(p4d)) { 374 ret_pte = (pte_t *)p4dp; 375 goto out; 376 } 377 378 if (is_hugepd(__hugepd(p4d_val(p4d)))) { 379 hpdp = (hugepd_t *)&p4d; 380 goto out_huge; 381 } 382 383 /* 384 * Even if we end up with an unmap, the pgtable will not 385 * be freed, because we do an rcu free and here we are 386 * irq disabled 387 */ 388 pdshift = PUD_SHIFT; 389 pudp = pud_offset(&p4d, ea); 390 pud = READ_ONCE(*pudp); 391 392 if (pud_none(pud)) 393 return NULL; 394 395 if (pud_is_leaf(pud)) { 396 ret_pte = (pte_t *)pudp; 397 goto out; 398 } 399 400 if (is_hugepd(__hugepd(pud_val(pud)))) { 401 hpdp = (hugepd_t *)&pud; 402 goto out_huge; 403 } 404 405 pdshift = PMD_SHIFT; 406 pmdp = pmd_offset(&pud, ea); 407 pmd = READ_ONCE(*pmdp); 408 409 /* 410 * A hugepage collapse is captured by this condition, see 411 * pmdp_collapse_flush. 412 */ 413 if (pmd_none(pmd)) 414 return NULL; 415 416 #ifdef CONFIG_PPC_BOOK3S_64 417 /* 418 * A hugepage split is captured by this condition, see 419 * pmdp_invalidate. 420 * 421 * Huge page modification can be caught here too. 422 */ 423 if (pmd_is_serializing(pmd)) 424 return NULL; 425 #endif 426 427 if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) { 428 if (is_thp) 429 *is_thp = true; 430 ret_pte = (pte_t *)pmdp; 431 goto out; 432 } 433 434 if (pmd_is_leaf(pmd)) { 435 ret_pte = (pte_t *)pmdp; 436 goto out; 437 } 438 439 if (is_hugepd(__hugepd(pmd_val(pmd)))) { 440 hpdp = (hugepd_t *)&pmd; 441 goto out_huge; 442 } 443 444 return pte_offset_kernel(&pmd, ea); 445 446 out_huge: 447 if (!hpdp) 448 return NULL; 449 450 ret_pte = hugepte_offset(*hpdp, ea, pdshift); 451 pdshift = hugepd_shift(*hpdp); 452 out: 453 if (hpage_shift) 454 *hpage_shift = pdshift; 455 return ret_pte; 456 } 457 EXPORT_SYMBOL_GPL(__find_linux_pte); 458