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
is_exec_fault(void)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 */
pte_looks_normal(pte_t pte)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
maybe_pte_to_page(pte_t pte)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
set_pte_filter_hash(pte_t pte)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
set_pte_filter_hash(pte_t pte)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 */
set_pte_filter(pte_t pte)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
set_access_flags_filter(pte_t pte,struct vm_area_struct * vma,int dirty)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 */
set_pte_at(struct mm_struct * mm,unsigned long addr,pte_t * ptep,pte_t pte)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 */
ptep_set_access_flags(struct vm_area_struct * vma,unsigned long address,pte_t * ptep,pte_t entry,int dirty)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
huge_ptep_set_access_flags(struct vm_area_struct * vma,unsigned long addr,pte_t * ptep,pte_t pte,int dirty)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)
set_huge_pte_at(struct mm_struct * mm,unsigned long addr,pte_t * ptep,pte_t pte)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
assert_pte_locked(struct mm_struct * mm,unsigned long addr)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
vmalloc_to_phys(void * va)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 */
__find_linux_pte(pgd_t * pgdir,unsigned long ea,bool * is_thp,unsigned * hpage_shift)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
