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1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * This file contains common routines for dealing with free of page tables
4 * Along with common page table handling code
6 * Derived from arch/powerpc/mm/tlb_64.c:
7 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
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
13 * Derived from "arch/i386/mm/init.c"
14 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
16 * Dave Engebretsen <engebret@us.ibm.com>
17 * Rework for PPC64 port.
20 #include <linux/kernel.h>
21 #include <linux/gfp.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>
29 #include <asm/hugetlb.h>
31 static inline int is_exec_fault(void)
33 return current
->thread
.regs
&& TRAP(current
->thread
.regs
) == 0x400;
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
41 static inline int pte_looks_normal(pte_t pte
)
44 if (pte_present(pte
) && !pte_special(pte
)) {
53 static struct page
*maybe_pte_to_page(pte_t pte
)
55 unsigned long pfn
= pte_pfn(pte
);
58 if (unlikely(!pfn_valid(pfn
)))
60 page
= pfn_to_page(pfn
);
61 if (PageReserved(page
))
66 #ifdef CONFIG_PPC_BOOK3S
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.
74 static pte_t
set_pte_filter_hash(pte_t pte
)
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
);
85 if (!test_bit(PG_arch_1
, &pg
->flags
)) {
86 flush_dcache_icache_page(pg
);
87 set_bit(PG_arch_1
, &pg
->flags
);
93 #else /* CONFIG_PPC_BOOK3S */
95 static pte_t
set_pte_filter_hash(pte_t pte
) { return pte
; }
97 #endif /* CONFIG_PPC_BOOK3S */
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.
103 static inline pte_t
set_pte_filter(pte_t pte
)
107 if (mmu_has_feature(MMU_FTR_HPTE_TABLE
))
108 return set_pte_filter_hash(pte
);
110 /* No exec permission in the first place, move on */
111 if (!pte_exec(pte
) || !pte_looks_normal(pte
))
114 /* If you set _PAGE_EXEC on weird pages you're on your own */
115 pg
= maybe_pte_to_page(pte
);
119 /* If the page clean, we move on */
120 if (test_bit(PG_arch_1
, &pg
->flags
))
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
);
130 /* Else, we filter out _PAGE_EXEC */
131 return pte_exprotect(pte
);
134 static pte_t
set_access_flags_filter(pte_t pte
, struct vm_area_struct
*vma
,
139 if (mmu_has_feature(MMU_FTR_HPTE_TABLE
))
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,
147 if (dirty
|| pte_exec(pte
) || !is_exec_fault())
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
155 if (WARN_ON(!(vma
->vm_flags
& VM_EXEC
)))
157 #endif /* CONFIG_DEBUG_VM */
159 /* If you set _PAGE_EXEC on weird pages you're on your own */
160 pg
= maybe_pte_to_page(pte
);
164 /* If the page is already clean, we move on */
165 if (test_bit(PG_arch_1
, &pg
->flags
))
168 /* Clean the page and set PG_arch_1 */
169 flush_dcache_icache_page(pg
);
170 set_bit(PG_arch_1
, &pg
->flags
);
173 return pte_mkexec(pte
);
177 * set_pte stores a linux PTE into the linux page table.
179 void set_pte_at(struct mm_struct
*mm
, unsigned long addr
, pte_t
*ptep
,
183 * Make sure hardware valid bit is not set. We don't do
184 * tlb flush for this update.
186 VM_WARN_ON(pte_hw_valid(*ptep
) && !pte_protnone(*ptep
));
188 /* Add the pte bit when trying to set a pte */
189 pte
= pte_mkpte(pte
);
191 /* Note: mm->context.id might not yet have been assigned as
192 * this context might not have been activated yet when this
195 pte
= set_pte_filter(pte
);
197 /* Perform the setting of the PTE */
198 __set_pte_at(mm
, addr
, ptep
, pte
, 0);
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
208 int ptep_set_access_flags(struct vm_area_struct
*vma
, unsigned long address
,
209 pte_t
*ptep
, pte_t entry
, int dirty
)
212 entry
= set_access_flags_filter(entry
, vma
, dirty
);
213 changed
= !pte_same(*(ptep
), entry
);
215 assert_pte_locked(vma
->vm_mm
, address
);
216 __ptep_set_access_flags(vma
, ptep
, entry
,
217 address
, mmu_virtual_psize
);
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
)
227 #ifdef HUGETLB_NEED_PRELOAD
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.
233 ptep_set_access_flags(vma
, addr
, ptep
, pte
, dirty
);
238 pte
= set_access_flags_filter(pte
, vma
, dirty
);
239 changed
= !pte_same(*(ptep
), pte
);
242 #ifdef CONFIG_PPC_BOOK3S_64
243 struct hstate
*h
= hstate_vma(vma
);
245 psize
= hstate_get_psize(h
);
246 #ifdef CONFIG_DEBUG_VM
247 assert_spin_locked(huge_pte_lockptr(h
, vma
->vm_mm
, ptep
));
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.
256 psize
= MMU_PAGE_COUNT
;
258 __ptep_set_access_flags(vma
, ptep
, pte
, addr
, psize
);
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
)
267 pmd_t
*pmd
= pmd_ptr(mm
, addr
);
269 pte_basic_t
*entry
= &ptep
->pte
;
270 int num
= is_hugepd(*((hugepd_t
*)pmd
)) ? 1 : SZ_512K
/ SZ_4K
;
274 * Make sure hardware valid bit is not set. We don't do
275 * tlb flush for this update.
277 VM_WARN_ON(pte_hw_valid(*ptep
) && !pte_protnone(*ptep
));
279 pte
= pte_mkpte(pte
);
281 pte
= set_pte_filter(pte
);
284 for (i
= 0; i
< num
; i
++, entry
++, val
+= SZ_4K
)
288 #endif /* CONFIG_HUGETLB_PAGE */
290 #ifdef CONFIG_DEBUG_VM
291 void assert_pte_locked(struct mm_struct
*mm
, unsigned long addr
)
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
);
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.
315 BUG_ON(!pmd_present(*pmd
));
316 assert_spin_locked(pte_lockptr(mm
, pmd
));
318 #endif /* CONFIG_DEBUG_VM */
320 unsigned long vmalloc_to_phys(void *va
)
322 unsigned long pfn
= vmalloc_to_pfn(va
);
325 return __pa(pfn_to_kaddr(pfn
)) + offset_in_page(va
);
327 EXPORT_SYMBOL_GPL(vmalloc_to_phys
);
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
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
341 pte_t
*__find_linux_pte(pgd_t
*pgdir
, unsigned long ea
,
342 bool *is_thp
, unsigned *hpage_shift
)
349 hugepd_t
*hpdp
= NULL
;
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.
365 pgdp
= pgdir
+ pgd_index(ea
);
366 p4dp
= p4d_offset(pgdp
, ea
);
367 p4d
= READ_ONCE(*p4dp
);
373 if (p4d_is_leaf(p4d
)) {
374 ret_pte
= (pte_t
*)p4dp
;
378 if (is_hugepd(__hugepd(p4d_val(p4d
)))) {
379 hpdp
= (hugepd_t
*)&p4d
;
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
389 pudp
= pud_offset(&p4d
, ea
);
390 pud
= READ_ONCE(*pudp
);
395 if (pud_is_leaf(pud
)) {
396 ret_pte
= (pte_t
*)pudp
;
400 if (is_hugepd(__hugepd(pud_val(pud
)))) {
401 hpdp
= (hugepd_t
*)&pud
;
406 pmdp
= pmd_offset(&pud
, ea
);
407 pmd
= READ_ONCE(*pmdp
);
410 * A hugepage collapse is captured by this condition, see
411 * pmdp_collapse_flush.
416 #ifdef CONFIG_PPC_BOOK3S_64
418 * A hugepage split is captured by this condition, see
421 * Huge page modification can be caught here too.
423 if (pmd_is_serializing(pmd
))
427 if (pmd_trans_huge(pmd
) || pmd_devmap(pmd
)) {
430 ret_pte
= (pte_t
*)pmdp
;
434 if (pmd_is_leaf(pmd
)) {
435 ret_pte
= (pte_t
*)pmdp
;
439 if (is_hugepd(__hugepd(pmd_val(pmd
)))) {
440 hpdp
= (hugepd_t
*)&pmd
;
444 return pte_offset_kernel(&pmd
, ea
);
450 ret_pte
= hugepte_offset(*hpdp
, ea
, pdshift
);
451 pdshift
= hugepd_shift(*hpdp
);
454 *hpage_shift
= pdshift
;
457 EXPORT_SYMBOL_GPL(__find_linux_pte
);