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 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. But 8xx
253 * can possibly use tsize derived from hstate.
254 */
255 psize = 0;
256 #endif
257 __ptep_set_access_flags(vma, ptep, pte, addr, psize);
258 }
259 return changed;
260 #endif
261 }
262 #endif /* CONFIG_HUGETLB_PAGE */
263
264 #ifdef CONFIG_DEBUG_VM
265 void assert_pte_locked(struct mm_struct *mm, unsigned long addr)
266 {
267 pgd_t *pgd;
268 pud_t *pud;
269 pmd_t *pmd;
270
271 if (mm == &init_mm)
272 return;
273 pgd = mm->pgd + pgd_index(addr);
274 BUG_ON(pgd_none(*pgd));
275 pud = pud_offset(pgd, addr);
276 BUG_ON(pud_none(*pud));
277 pmd = pmd_offset(pud, addr);
278 /*
279 * khugepaged to collapse normal pages to hugepage, first set
280 * pmd to none to force page fault/gup to take mmap_sem. After
281 * pmd is set to none, we do a pte_clear which does this assertion
282 * so if we find pmd none, return.
283 */
284 if (pmd_none(*pmd))
285 return;
286 BUG_ON(!pmd_present(*pmd));
287 assert_spin_locked(pte_lockptr(mm, pmd));
288 }
289 #endif /* CONFIG_DEBUG_VM */
290
291 unsigned long vmalloc_to_phys(void *va)
292 {
293 unsigned long pfn = vmalloc_to_pfn(va);
294
295 BUG_ON(!pfn);
296 return __pa(pfn_to_kaddr(pfn)) + offset_in_page(va);
297 }
298 EXPORT_SYMBOL_GPL(vmalloc_to_phys);
299
300 /*
301 * We have 4 cases for pgds and pmds:
302 * (1) invalid (all zeroes)
303 * (2) pointer to next table, as normal; bottom 6 bits == 0
304 * (3) leaf pte for huge page _PAGE_PTE set
305 * (4) hugepd pointer, _PAGE_PTE = 0 and bits [2..6] indicate size of table
306 *
307 * So long as we atomically load page table pointers we are safe against teardown,
308 * we can follow the address down to the the page and take a ref on it.
309 * This function need to be called with interrupts disabled. We use this variant
310 * when we have MSR[EE] = 0 but the paca->irq_soft_mask = IRQS_ENABLED
311 */
312 pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea,
313 bool *is_thp, unsigned *hpage_shift)
314 {
315 pgd_t pgd, *pgdp;
316 pud_t pud, *pudp;
317 pmd_t pmd, *pmdp;
318 pte_t *ret_pte;
319 hugepd_t *hpdp = NULL;
320 unsigned pdshift = PGDIR_SHIFT;
321
322 if (hpage_shift)
323 *hpage_shift = 0;
324
325 if (is_thp)
326 *is_thp = false;
327
328 pgdp = pgdir + pgd_index(ea);
329 pgd = READ_ONCE(*pgdp);
330 /*
331 * Always operate on the local stack value. This make sure the
332 * value don't get updated by a parallel THP split/collapse,
333 * page fault or a page unmap. The return pte_t * is still not
334 * stable. So should be checked there for above conditions.
335 */
336 if (pgd_none(pgd))
337 return NULL;
338
339 if (pgd_is_leaf(pgd)) {
340 ret_pte = (pte_t *)pgdp;
341 goto out;
342 }
343
344 if (is_hugepd(__hugepd(pgd_val(pgd)))) {
345 hpdp = (hugepd_t *)&pgd;
346 goto out_huge;
347 }
348
349 /*
350 * Even if we end up with an unmap, the pgtable will not
351 * be freed, because we do an rcu free and here we are
352 * irq disabled
353 */
354 pdshift = PUD_SHIFT;
355 pudp = pud_offset(&pgd, ea);
356 pud = READ_ONCE(*pudp);
357
358 if (pud_none(pud))
359 return NULL;
360
361 if (pud_is_leaf(pud)) {
362 ret_pte = (pte_t *)pudp;
363 goto out;
364 }
365
366 if (is_hugepd(__hugepd(pud_val(pud)))) {
367 hpdp = (hugepd_t *)&pud;
368 goto out_huge;
369 }
370
371 pdshift = PMD_SHIFT;
372 pmdp = pmd_offset(&pud, ea);
373 pmd = READ_ONCE(*pmdp);
374
375 /*
376 * A hugepage collapse is captured by this condition, see
377 * pmdp_collapse_flush.
378 */
379 if (pmd_none(pmd))
380 return NULL;
381
382 #ifdef CONFIG_PPC_BOOK3S_64
383 /*
384 * A hugepage split is captured by this condition, see
385 * pmdp_invalidate.
386 *
387 * Huge page modification can be caught here too.
388 */
389 if (pmd_is_serializing(pmd))
390 return NULL;
391 #endif
392
393 if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) {
394 if (is_thp)
395 *is_thp = true;
396 ret_pte = (pte_t *)pmdp;
397 goto out;
398 }
399
400 if (pmd_is_leaf(pmd)) {
401 ret_pte = (pte_t *)pmdp;
402 goto out;
403 }
404
405 if (is_hugepd(__hugepd(pmd_val(pmd)))) {
406 hpdp = (hugepd_t *)&pmd;
407 goto out_huge;
408 }
409
410 return pte_offset_kernel(&pmd, ea);
411
412 out_huge:
413 if (!hpdp)
414 return NULL;
415
416 ret_pte = hugepte_offset(*hpdp, ea, pdshift);
417 pdshift = hugepd_shift(*hpdp);
418 out:
419 if (hpage_shift)
420 *hpage_shift = pdshift;
421 return ret_pte;
422 }
423 EXPORT_SYMBOL_GPL(__find_linux_pte);