// SPDX-License-Identifier: GPL-2.0/* *  mm/pgtable-generic.c * *  Generic pgtable methods declared in linux/pgtable.h * *  Copyright (C) 2010  Linus Torvalds */ #include <linux/pagemap.h>#include <linux/hugetlb.h>#include <linux/pgtable.h>#include <linux/swap.h>#include <linux/swapops.h>#include <linux/mm_inline.h>#include <linux/iommu.h>#include <linux/pgalloc.h> #include <asm/tlb.h> /* * If a p?d_bad entry is found while walking page tables, report * the error, before resetting entry to p?d_none.  Usually (but * very seldom) called out from the p?d_none_or_clear_bad macros. */ void pgd_clear_bad(pgd_t *pgd){	pgd_ERROR(*pgd);	pgd_clear(pgd);} #ifndef __PAGETABLE_P4D_FOLDEDvoid p4d_clear_bad(p4d_t *p4d){	p4d_ERROR(*p4d);	p4d_clear(p4d);}#endif #ifndef __PAGETABLE_PUD_FOLDEDvoid pud_clear_bad(pud_t *pud){	pud_ERROR(*pud);	pud_clear(pud);}#endif /* * Note that the pmd variant below can't be stub'ed out just as for p4d/pud * above. pmd folding is special and typically pmd_* macros refer to upper * level even when folded */void pmd_clear_bad(pmd_t *pmd){	pmd_ERROR(*pmd);	pmd_clear(pmd);} #ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS/* * Only sets the access flags (dirty, accessed), as well as write * permission. Furthermore, we know it always gets set to a "more * permissive" setting, which allows most architectures to optimize * this. We return whether the PTE actually changed, which in turn * instructs the caller to do things like update__mmu_cache.  This * used to be done in the caller, but sparc needs minor faults to * force that call on sun4c so we changed this macro slightly */int ptep_set_access_flags(struct vm_area_struct *vma,			  unsigned long address, pte_t *ptep,			  pte_t entry, int dirty){	int changed = !pte_same(ptep_get(ptep), entry);	if (changed) {		set_pte_at(vma->vm_mm, address, ptep, entry);		flush_tlb_fix_spurious_fault(vma, address, ptep);	}	return changed;}#endif #ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSHbool ptep_clear_flush_young(struct vm_area_struct *vma,		unsigned long address, pte_t *ptep){	bool young; 	young = ptep_test_and_clear_young(vma, address, ptep);	if (young)		flush_tlb_page(vma, address);	return young;}#endif #ifndef __HAVE_ARCH_PTEP_CLEAR_FLUSHpte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address,		       pte_t *ptep){	struct mm_struct *mm = (vma)->vm_mm;	pte_t pte;	pte = ptep_get_and_clear(mm, address, ptep);	if (pte_accessible(mm, pte))		flush_tlb_page(vma, address);	return pte;}#endif #ifdef CONFIG_TRANSPARENT_HUGEPAGE #ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGSint pmdp_set_access_flags(struct vm_area_struct *vma,			  unsigned long address, pmd_t *pmdp,			  pmd_t entry, int dirty){	int changed = !pmd_same(*pmdp, entry);	VM_BUG_ON(address & ~HPAGE_PMD_MASK);	if (changed) {		set_pmd_at(vma->vm_mm, address, pmdp, entry);		flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);	}	return changed;}#endif #ifndef __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSHbool pmdp_clear_flush_young(struct vm_area_struct *vma,		unsigned long address, pmd_t *pmdp){	bool young; 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);	young = pmdp_test_and_clear_young(vma, address, pmdp);	if (young)		flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);	return young;}#endif #ifndef __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSHpmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address,			    pmd_t *pmdp){	pmd_t pmd;	VM_BUG_ON(address & ~HPAGE_PMD_MASK);	VM_BUG_ON(pmd_present(*pmdp) && !pmd_trans_huge(*pmdp));	pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);	flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);	return pmd;} #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUDpud_t pudp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address,			    pud_t *pudp){	pud_t pud; 	VM_BUG_ON(address & ~HPAGE_PUD_MASK);	VM_BUG_ON(!pud_trans_huge(*pudp));	pud = pudp_huge_get_and_clear(vma->vm_mm, address, pudp);	flush_pud_tlb_range(vma, address, address + HPAGE_PUD_SIZE);	return pud;}#endif#endif #ifndef __HAVE_ARCH_PGTABLE_DEPOSITvoid pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,				pgtable_t pgtable){	assert_spin_locked(pmd_lockptr(mm, pmdp)); 	/* FIFO */	if (!pmd_huge_pte(mm, pmdp))		INIT_LIST_HEAD(&pgtable->lru);	else		list_add(&pgtable->lru, &pmd_huge_pte(mm, pmdp)->lru);	pmd_huge_pte(mm, pmdp) = pgtable;}#endif #ifndef __HAVE_ARCH_PGTABLE_WITHDRAW/* no "address" argument so destroys page coloring of some arch */pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp){	pgtable_t pgtable; 	assert_spin_locked(pmd_lockptr(mm, pmdp)); 	/* FIFO */	pgtable = pmd_huge_pte(mm, pmdp);	pmd_huge_pte(mm, pmdp) = list_first_entry_or_null(&pgtable->lru,							  struct page, lru);	if (pmd_huge_pte(mm, pmdp))		list_del(&pgtable->lru);	return pgtable;}#endif #ifndef __HAVE_ARCH_PMDP_INVALIDATEpmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,		     pmd_t *pmdp){	VM_WARN_ON_ONCE(!pmd_present(*pmdp));	pmd_t old = pmdp_establish(vma, address, pmdp, pmd_mkinvalid(*pmdp));	flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);	return old;}#endif #ifndef __HAVE_ARCH_PMDP_INVALIDATE_ADpmd_t pmdp_invalidate_ad(struct vm_area_struct *vma, unsigned long address,			 pmd_t *pmdp){	VM_WARN_ON_ONCE(!pmd_present(*pmdp));	return pmdp_invalidate(vma, address, pmdp);}#endif #ifndef pmdp_collapse_flushpmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,			  pmd_t *pmdp){	/*	 * pmd and hugepage pte format are same. So we could	 * use the same function.	 */	pmd_t pmd; 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);	VM_BUG_ON(pmd_trans_huge(*pmdp));	pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp); 	/* collapse entails shooting down ptes not pmd */	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);	return pmd;}#endif /* arch define pte_free_defer in asm/pgalloc.h for its own implementation */#ifndef pte_free_deferstatic void pte_free_now(struct rcu_head *head){	struct page *page; 	page = container_of(head, struct page, rcu_head);	pte_free(NULL /* mm not passed and not used */, (pgtable_t)page);} void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable){	struct page *page; 	page = pgtable;	call_rcu(&page->rcu_head, pte_free_now);}#endif /* pte_free_defer */#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #if defined(CONFIG_GUP_GET_PXX_LOW_HIGH) && \	(defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RCU))/* * See the comment above ptep_get_lockless() in include/linux/pgtable.h: * the barriers in pmdp_get_lockless() cannot guarantee that the value in * pmd_high actually belongs with the value in pmd_low; but holding interrupts * off blocks the TLB flush between present updates, which guarantees that a * successful __pte_offset_map() points to a page from matched halves. */static unsigned long pmdp_get_lockless_start(void){	unsigned long irqflags; 	local_irq_save(irqflags);	return irqflags;}static void pmdp_get_lockless_end(unsigned long irqflags){	local_irq_restore(irqflags);}#elsestatic unsigned long pmdp_get_lockless_start(void) { return 0; }static void pmdp_get_lockless_end(unsigned long irqflags) { }#endif pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp){	unsigned long irqflags;	pmd_t pmdval; 	rcu_read_lock();	irqflags = pmdp_get_lockless_start();	pmdval = pmdp_get_lockless(pmd);	pmdp_get_lockless_end(irqflags); 	if (pmdvalp)		*pmdvalp = pmdval;	if (unlikely(pmd_none(pmdval) || !pmd_present(pmdval)))		goto nomap;	if (unlikely(pmd_trans_huge(pmdval)))		goto nomap;	if (unlikely(pmd_bad(pmdval))) {		pmd_clear_bad(pmd);		goto nomap;	}	return __pte_map(&pmdval, addr);nomap:	rcu_read_unlock();	return NULL;} pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd,				unsigned long addr, spinlock_t **ptlp){	pmd_t pmdval;	pte_t *pte; 	pte = __pte_offset_map(pmd, addr, &pmdval);	if (likely(pte))		*ptlp = pte_lockptr(mm, &pmdval);	return pte;} pte_t *pte_offset_map_rw_nolock(struct mm_struct *mm, pmd_t *pmd,				unsigned long addr, pmd_t *pmdvalp,				spinlock_t **ptlp){	pte_t *pte; 	VM_WARN_ON_ONCE(!pmdvalp);	pte = __pte_offset_map(pmd, addr, pmdvalp);	if (likely(pte))		*ptlp = pte_lockptr(mm, pmdvalp);	return pte;} /* * pte_offset_map_lock(mm, pmd, addr, ptlp) is usually called with the pmd * pointer for addr, reached by walking down the mm's pgd, p4d, pud for addr: * either while holding mmap_lock or vma lock for read or for write; or in * truncate or rmap context, while holding file's i_mmap_lock or anon_vma lock * for read (or for write). In a few cases, it may be used with pmd pointing to * a pmd_t already copied to or constructed on the stack. * * When successful, it returns the pte pointer for addr, with its page table * kmapped if necessary (when CONFIG_HIGHPTE), and locked against concurrent * modification by software, with a pointer to that spinlock in ptlp (in some * configs mm->page_table_lock, in SPLIT_PTLOCK configs a spinlock in table's * struct page).  pte_unmap_unlock(pte, ptl) to unlock and unmap afterwards. * * But it is unsuccessful, returning NULL with *ptlp unchanged, if there is no * page table at *pmd: if, for example, the page table has just been removed, * or replaced by the huge pmd of a THP.  (When successful, *pmd is rechecked * after acquiring the ptlock, and retried internally if it changed: so that a * page table can be safely removed or replaced by THP while holding its lock.) * * pte_offset_map(pmd, addr), and its internal helper __pte_offset_map() above, * just returns the pte pointer for addr, its page table kmapped if necessary; * or NULL if there is no page table at *pmd.  It does not attempt to lock the * page table, so cannot normally be used when the page table is to be updated, * or when entries read must be stable.  But it does take rcu_read_lock(): so * that even when page table is racily removed, it remains a valid though empty * and disconnected table.  Until pte_unmap(pte) unmaps and rcu_read_unlock()s * afterwards. * * pte_offset_map_ro_nolock(mm, pmd, addr, ptlp), above, is like pte_offset_map(); * but when successful, it also outputs a pointer to the spinlock in ptlp - as * pte_offset_map_lock() does, but in this case without locking it.  This helps * the caller to avoid a later pte_lockptr(mm, *pmd), which might by that time * act on a changed *pmd: pte_offset_map_ro_nolock() provides the correct spinlock * pointer for the page table that it returns. Even after grabbing the spinlock, * we might be looking either at a page table that is still mapped or one that * was unmapped and is about to get freed. But for R/O access this is sufficient. * So it is only applicable for read-only cases where any modification operations * to the page table are not allowed even if the corresponding spinlock is held * afterwards. * * pte_offset_map_rw_nolock(mm, pmd, addr, pmdvalp, ptlp), above, is like * pte_offset_map_ro_nolock(); but when successful, it also outputs the pdmval. * It is applicable for may-write cases where any modification operations to the * page table may happen after the corresponding spinlock is held afterwards. * But the users should make sure the page table is stable like checking pte_same() * or checking pmd_same() by using the output pmdval before performing the write * operations. * * Note: "RO" / "RW" expresses the intended semantics, not that the *kmap* will * be read-only/read-write protected. * * Note that free_pgtables(), used after unmapping detached vmas, or when * exiting the whole mm, does not take page table lock before freeing a page * table, and may not use RCU at all: "outsiders" like khugepaged should avoid * pte_offset_map() and co once the vma is detached from mm or mm_users is zero. */pte_t *pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd,			   unsigned long addr, spinlock_t **ptlp){	spinlock_t *ptl;	pmd_t pmdval;	pte_t *pte;again:	pte = __pte_offset_map(pmd, addr, &pmdval);	if (unlikely(!pte))		return pte;	ptl = pte_lockptr(mm, &pmdval);	spin_lock(ptl);	if (likely(pmd_same(pmdval, pmdp_get_lockless(pmd)))) {		*ptlp = ptl;		return pte;	}	pte_unmap_unlock(pte, ptl);	goto again;} #ifdef CONFIG_ASYNC_KERNEL_PGTABLE_FREEstatic void kernel_pgtable_work_func(struct work_struct *work); static struct {	struct list_head list;	/* protect above ptdesc lists */	spinlock_t lock;	struct work_struct work;} kernel_pgtable_work = {	.list = LIST_HEAD_INIT(kernel_pgtable_work.list),	.lock = __SPIN_LOCK_UNLOCKED(kernel_pgtable_work.lock),	.work = __WORK_INITIALIZER(kernel_pgtable_work.work, kernel_pgtable_work_func),}; static void kernel_pgtable_work_func(struct work_struct *work){	struct ptdesc *pt, *next;	LIST_HEAD(page_list); 	spin_lock(&kernel_pgtable_work.lock);	list_splice_tail_init(&kernel_pgtable_work.list, &page_list);	spin_unlock(&kernel_pgtable_work.lock); 	iommu_sva_invalidate_kva_range(PAGE_OFFSET, TLB_FLUSH_ALL);	list_for_each_entry_safe(pt, next, &page_list, pt_list)		__pagetable_free(pt);} void pagetable_free_kernel(struct ptdesc *pt){	spin_lock(&kernel_pgtable_work.lock);	list_add(&pt->pt_list, &kernel_pgtable_work.list);	spin_unlock(&kernel_pgtable_work.lock); 	schedule_work(&kernel_pgtable_work.work);}#endif