gup.c 46.1 KB
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#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/spinlock.h>

#include <linux/mm.h>
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#include <linux/memremap.h>
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#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/swapops.h>

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#include <linux/sched/signal.h>
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#include <linux/rwsem.h>
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#include <linux/hugetlb.h>
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#include <asm/mmu_context.h>
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#include <asm/pgtable.h>
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#include <asm/tlbflush.h>
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#include "internal.h"

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static struct page *no_page_table(struct vm_area_struct *vma,
		unsigned int flags)
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{
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	/*
	 * When core dumping an enormous anonymous area that nobody
	 * has touched so far, we don't want to allocate unnecessary pages or
	 * page tables.  Return error instead of NULL to skip handle_mm_fault,
	 * then get_dump_page() will return NULL to leave a hole in the dump.
	 * But we can only make this optimization where a hole would surely
	 * be zero-filled if handle_mm_fault() actually did handle it.
	 */
	if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault))
		return ERR_PTR(-EFAULT);
	return NULL;
}
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static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
		pte_t *pte, unsigned int flags)
{
	/* No page to get reference */
	if (flags & FOLL_GET)
		return -EFAULT;

	if (flags & FOLL_TOUCH) {
		pte_t entry = *pte;

		if (flags & FOLL_WRITE)
			entry = pte_mkdirty(entry);
		entry = pte_mkyoung(entry);

		if (!pte_same(*pte, entry)) {
			set_pte_at(vma->vm_mm, address, pte, entry);
			update_mmu_cache(vma, address, pte);
		}
	}

	/* Proper page table entry exists, but no corresponding struct page */
	return -EEXIST;
}

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/*
 * FOLL_FORCE can write to even unwritable pte's, but only
 * after we've gone through a COW cycle and they are dirty.
 */
static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
{
	return pte_write(pte) ||
		((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
}

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static struct page *follow_page_pte(struct vm_area_struct *vma,
		unsigned long address, pmd_t *pmd, unsigned int flags)
{
	struct mm_struct *mm = vma->vm_mm;
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	struct dev_pagemap *pgmap = NULL;
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	struct page *page;
	spinlock_t *ptl;
	pte_t *ptep, pte;
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retry:
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	if (unlikely(pmd_bad(*pmd)))
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		return no_page_table(vma, flags);
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	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
	pte = *ptep;
	if (!pte_present(pte)) {
		swp_entry_t entry;
		/*
		 * KSM's break_ksm() relies upon recognizing a ksm page
		 * even while it is being migrated, so for that case we
		 * need migration_entry_wait().
		 */
		if (likely(!(flags & FOLL_MIGRATION)))
			goto no_page;
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		if (pte_none(pte))
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			goto no_page;
		entry = pte_to_swp_entry(pte);
		if (!is_migration_entry(entry))
			goto no_page;
		pte_unmap_unlock(ptep, ptl);
		migration_entry_wait(mm, pmd, address);
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		goto retry;
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	}
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	if ((flags & FOLL_NUMA) && pte_protnone(pte))
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		goto no_page;
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	if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
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		pte_unmap_unlock(ptep, ptl);
		return NULL;
	}
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	page = vm_normal_page(vma, address, pte);
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	if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
		/*
		 * Only return device mapping pages in the FOLL_GET case since
		 * they are only valid while holding the pgmap reference.
		 */
		pgmap = get_dev_pagemap(pte_pfn(pte), NULL);
		if (pgmap)
			page = pte_page(pte);
		else
			goto no_page;
	} else if (unlikely(!page)) {
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		if (flags & FOLL_DUMP) {
			/* Avoid special (like zero) pages in core dumps */
			page = ERR_PTR(-EFAULT);
			goto out;
		}

		if (is_zero_pfn(pte_pfn(pte))) {
			page = pte_page(pte);
		} else {
			int ret;

			ret = follow_pfn_pte(vma, address, ptep, flags);
			page = ERR_PTR(ret);
			goto out;
		}
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	}

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	if (flags & FOLL_SPLIT && PageTransCompound(page)) {
		int ret;
		get_page(page);
		pte_unmap_unlock(ptep, ptl);
		lock_page(page);
		ret = split_huge_page(page);
		unlock_page(page);
		put_page(page);
		if (ret)
			return ERR_PTR(ret);
		goto retry;
	}

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	if (flags & FOLL_GET) {
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		get_page(page);
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		/* drop the pgmap reference now that we hold the page */
		if (pgmap) {
			put_dev_pagemap(pgmap);
			pgmap = NULL;
		}
	}
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	if (flags & FOLL_TOUCH) {
		if ((flags & FOLL_WRITE) &&
		    !pte_dirty(pte) && !PageDirty(page))
			set_page_dirty(page);
		/*
		 * pte_mkyoung() would be more correct here, but atomic care
		 * is needed to avoid losing the dirty bit: it is easier to use
		 * mark_page_accessed().
		 */
		mark_page_accessed(page);
	}
E
Eric B Munson 已提交
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	if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
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		/* Do not mlock pte-mapped THP */
		if (PageTransCompound(page))
			goto out;

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		/*
		 * The preliminary mapping check is mainly to avoid the
		 * pointless overhead of lock_page on the ZERO_PAGE
		 * which might bounce very badly if there is contention.
		 *
		 * If the page is already locked, we don't need to
		 * handle it now - vmscan will handle it later if and
		 * when it attempts to reclaim the page.
		 */
		if (page->mapping && trylock_page(page)) {
			lru_add_drain();  /* push cached pages to LRU */
			/*
			 * Because we lock page here, and migration is
			 * blocked by the pte's page reference, and we
			 * know the page is still mapped, we don't even
			 * need to check for file-cache page truncation.
			 */
			mlock_vma_page(page);
			unlock_page(page);
		}
	}
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out:
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	pte_unmap_unlock(ptep, ptl);
	return page;
no_page:
	pte_unmap_unlock(ptep, ptl);
	if (!pte_none(pte))
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		return NULL;
	return no_page_table(vma, flags);
}

/**
 * follow_page_mask - look up a page descriptor from a user-virtual address
 * @vma: vm_area_struct mapping @address
 * @address: virtual address to look up
 * @flags: flags modifying lookup behaviour
 * @page_mask: on output, *page_mask is set according to the size of the page
 *
 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
 *
 * Returns the mapped (struct page *), %NULL if no mapping exists, or
 * an error pointer if there is a mapping to something not represented
 * by a page descriptor (see also vm_normal_page()).
 */
struct page *follow_page_mask(struct vm_area_struct *vma,
			      unsigned long address, unsigned int flags,
			      unsigned int *page_mask)
{
	pgd_t *pgd;
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	p4d_t *p4d;
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	pud_t *pud;
	pmd_t *pmd;
	spinlock_t *ptl;
	struct page *page;
	struct mm_struct *mm = vma->vm_mm;

	*page_mask = 0;

	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
	if (!IS_ERR(page)) {
		BUG_ON(flags & FOLL_GET);
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		return page;
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	}
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	pgd = pgd_offset(mm, address);
	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
		return no_page_table(vma, flags);
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	p4d = p4d_offset(pgd, address);
	if (p4d_none(*p4d))
		return no_page_table(vma, flags);
	BUILD_BUG_ON(p4d_huge(*p4d));
	if (unlikely(p4d_bad(*p4d)))
		return no_page_table(vma, flags);
	pud = pud_offset(p4d, address);
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	if (pud_none(*pud))
		return no_page_table(vma, flags);
	if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
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		page = follow_huge_pud(mm, address, pud, flags);
		if (page)
			return page;
		return no_page_table(vma, flags);
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	}
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	if (pud_devmap(*pud)) {
		ptl = pud_lock(mm, pud);
		page = follow_devmap_pud(vma, address, pud, flags);
		spin_unlock(ptl);
		if (page)
			return page;
	}
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	if (unlikely(pud_bad(*pud)))
		return no_page_table(vma, flags);

	pmd = pmd_offset(pud, address);
	if (pmd_none(*pmd))
		return no_page_table(vma, flags);
	if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
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		page = follow_huge_pmd(mm, address, pmd, flags);
		if (page)
			return page;
		return no_page_table(vma, flags);
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	}
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	if (pmd_devmap(*pmd)) {
		ptl = pmd_lock(mm, pmd);
		page = follow_devmap_pmd(vma, address, pmd, flags);
		spin_unlock(ptl);
		if (page)
			return page;
	}
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	if (likely(!pmd_trans_huge(*pmd)))
		return follow_page_pte(vma, address, pmd, flags);

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	if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
		return no_page_table(vma, flags);

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	ptl = pmd_lock(mm, pmd);
	if (unlikely(!pmd_trans_huge(*pmd))) {
		spin_unlock(ptl);
		return follow_page_pte(vma, address, pmd, flags);
	}
	if (flags & FOLL_SPLIT) {
		int ret;
		page = pmd_page(*pmd);
		if (is_huge_zero_page(page)) {
			spin_unlock(ptl);
			ret = 0;
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			split_huge_pmd(vma, pmd, address);
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			if (pmd_trans_unstable(pmd))
				ret = -EBUSY;
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		} else {
			get_page(page);
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			spin_unlock(ptl);
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			lock_page(page);
			ret = split_huge_page(page);
			unlock_page(page);
			put_page(page);
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			if (pmd_none(*pmd))
				return no_page_table(vma, flags);
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		}

		return ret ? ERR_PTR(ret) :
			follow_page_pte(vma, address, pmd, flags);
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	}
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	page = follow_trans_huge_pmd(vma, address, pmd, flags);
	spin_unlock(ptl);
	*page_mask = HPAGE_PMD_NR - 1;
	return page;
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}

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static int get_gate_page(struct mm_struct *mm, unsigned long address,
		unsigned int gup_flags, struct vm_area_struct **vma,
		struct page **page)
{
	pgd_t *pgd;
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	p4d_t *p4d;
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	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	int ret = -EFAULT;

	/* user gate pages are read-only */
	if (gup_flags & FOLL_WRITE)
		return -EFAULT;
	if (address > TASK_SIZE)
		pgd = pgd_offset_k(address);
	else
		pgd = pgd_offset_gate(mm, address);
	BUG_ON(pgd_none(*pgd));
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	p4d = p4d_offset(pgd, address);
	BUG_ON(p4d_none(*p4d));
	pud = pud_offset(p4d, address);
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	BUG_ON(pud_none(*pud));
	pmd = pmd_offset(pud, address);
	if (pmd_none(*pmd))
		return -EFAULT;
	VM_BUG_ON(pmd_trans_huge(*pmd));
	pte = pte_offset_map(pmd, address);
	if (pte_none(*pte))
		goto unmap;
	*vma = get_gate_vma(mm);
	if (!page)
		goto out;
	*page = vm_normal_page(*vma, address, *pte);
	if (!*page) {
		if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
			goto unmap;
		*page = pte_page(*pte);
	}
	get_page(*page);
out:
	ret = 0;
unmap:
	pte_unmap(pte);
	return ret;
}

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/*
 * mmap_sem must be held on entry.  If @nonblocking != NULL and
 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
 */
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static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
		unsigned long address, unsigned int *flags, int *nonblocking)
{
	unsigned int fault_flags = 0;
	int ret;

E
Eric B Munson 已提交
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	/* mlock all present pages, but do not fault in new pages */
	if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
		return -ENOENT;
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	/* For mm_populate(), just skip the stack guard page. */
	if ((*flags & FOLL_POPULATE) &&
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			(stack_guard_page_start(vma, address) ||
			 stack_guard_page_end(vma, address + PAGE_SIZE)))
		return -ENOENT;
	if (*flags & FOLL_WRITE)
		fault_flags |= FAULT_FLAG_WRITE;
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	if (*flags & FOLL_REMOTE)
		fault_flags |= FAULT_FLAG_REMOTE;
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	if (nonblocking)
		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
	if (*flags & FOLL_NOWAIT)
		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
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	if (*flags & FOLL_TRIED) {
		VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
		fault_flags |= FAULT_FLAG_TRIED;
	}
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	ret = handle_mm_fault(vma, address, fault_flags);
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	if (ret & VM_FAULT_ERROR) {
		if (ret & VM_FAULT_OOM)
			return -ENOMEM;
		if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
			return *flags & FOLL_HWPOISON ? -EHWPOISON : -EFAULT;
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		if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
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			return -EFAULT;
		BUG();
	}

	if (tsk) {
		if (ret & VM_FAULT_MAJOR)
			tsk->maj_flt++;
		else
			tsk->min_flt++;
	}

	if (ret & VM_FAULT_RETRY) {
		if (nonblocking)
			*nonblocking = 0;
		return -EBUSY;
	}

	/*
	 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
	 * necessary, even if maybe_mkwrite decided not to set pte_write. We
	 * can thus safely do subsequent page lookups as if they were reads.
	 * But only do so when looping for pte_write is futile: in some cases
	 * userspace may also be wanting to write to the gotten user page,
	 * which a read fault here might prevent (a readonly page might get
	 * reCOWed by userspace write).
	 */
	if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
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	        *flags |= FOLL_COW;
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	return 0;
}

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static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
{
	vm_flags_t vm_flags = vma->vm_flags;
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	int write = (gup_flags & FOLL_WRITE);
	int foreign = (gup_flags & FOLL_REMOTE);
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	if (vm_flags & (VM_IO | VM_PFNMAP))
		return -EFAULT;

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	if (write) {
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		if (!(vm_flags & VM_WRITE)) {
			if (!(gup_flags & FOLL_FORCE))
				return -EFAULT;
			/*
			 * We used to let the write,force case do COW in a
			 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
			 * set a breakpoint in a read-only mapping of an
			 * executable, without corrupting the file (yet only
			 * when that file had been opened for writing!).
			 * Anon pages in shared mappings are surprising: now
			 * just reject it.
			 */
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			if (!is_cow_mapping(vm_flags))
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				return -EFAULT;
		}
	} else if (!(vm_flags & VM_READ)) {
		if (!(gup_flags & FOLL_FORCE))
			return -EFAULT;
		/*
		 * Is there actually any vma we can reach here which does not
		 * have VM_MAYREAD set?
		 */
		if (!(vm_flags & VM_MAYREAD))
			return -EFAULT;
	}
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	/*
	 * gups are always data accesses, not instruction
	 * fetches, so execute=false here
	 */
	if (!arch_vma_access_permitted(vma, write, false, foreign))
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		return -EFAULT;
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	return 0;
}

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/**
 * __get_user_pages() - pin user pages in memory
 * @tsk:	task_struct of target task
 * @mm:		mm_struct of target mm
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
 * @gup_flags:	flags modifying pin behaviour
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_pages long. Or NULL, if caller
 *		only intends to ensure the pages are faulted in.
 * @vmas:	array of pointers to vmas corresponding to each page.
 *		Or NULL if the caller does not require them.
 * @nonblocking: whether waiting for disk IO or mmap_sem contention
 *
 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno. Each page returned must be released
 * with a put_page() call when it is finished with. vmas will only
 * remain valid while mmap_sem is held.
 *
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 * Must be called with mmap_sem held.  It may be released.  See below.
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 *
 * __get_user_pages walks a process's page tables and takes a reference to
 * each struct page that each user address corresponds to at a given
 * instant. That is, it takes the page that would be accessed if a user
 * thread accesses the given user virtual address at that instant.
 *
 * This does not guarantee that the page exists in the user mappings when
 * __get_user_pages returns, and there may even be a completely different
 * page there in some cases (eg. if mmapped pagecache has been invalidated
 * and subsequently re faulted). However it does guarantee that the page
 * won't be freed completely. And mostly callers simply care that the page
 * contains data that was valid *at some point in time*. Typically, an IO
 * or similar operation cannot guarantee anything stronger anyway because
 * locks can't be held over the syscall boundary.
 *
 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
 * appropriate) must be called after the page is finished with, and
 * before put_page is called.
 *
 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
 * or mmap_sem contention, and if waiting is needed to pin all pages,
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 * *@nonblocking will be set to 0.  Further, if @gup_flags does not
 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
 * this case.
 *
 * A caller using such a combination of @nonblocking and @gup_flags
 * must therefore hold the mmap_sem for reading only, and recognize
 * when it's been released.  Otherwise, it must be held for either
 * reading or writing and will not be released.
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 *
 * In most cases, get_user_pages or get_user_pages_fast should be used
 * instead of __get_user_pages. __get_user_pages should be used only if
 * you need some special @gup_flags.
 */
L
Lorenzo Stoakes 已提交
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static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
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		unsigned long start, unsigned long nr_pages,
		unsigned int gup_flags, struct page **pages,
		struct vm_area_struct **vmas, int *nonblocking)
{
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	long i = 0;
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	unsigned int page_mask;
553
	struct vm_area_struct *vma = NULL;
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	if (!nr_pages)
		return 0;

	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));

	/*
	 * If FOLL_FORCE is set then do not force a full fault as the hinting
	 * fault information is unrelated to the reference behaviour of a task
	 * using the address space
	 */
	if (!(gup_flags & FOLL_FORCE))
		gup_flags |= FOLL_NUMA;

	do {
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		struct page *page;
		unsigned int foll_flags = gup_flags;
		unsigned int page_increm;

		/* first iteration or cross vma bound */
		if (!vma || start >= vma->vm_end) {
			vma = find_extend_vma(mm, start);
			if (!vma && in_gate_area(mm, start)) {
				int ret;
				ret = get_gate_page(mm, start & PAGE_MASK,
						gup_flags, &vma,
						pages ? &pages[i] : NULL);
				if (ret)
					return i ? : ret;
				page_mask = 0;
				goto next_page;
			}
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			if (!vma || check_vma_flags(vma, gup_flags))
				return i ? : -EFAULT;
			if (is_vm_hugetlb_page(vma)) {
				i = follow_hugetlb_page(mm, vma, pages, vmas,
						&start, &nr_pages, i,
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						gup_flags, nonblocking);
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				continue;
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			}
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		}
retry:
		/*
		 * If we have a pending SIGKILL, don't keep faulting pages and
		 * potentially allocating memory.
		 */
		if (unlikely(fatal_signal_pending(current)))
			return i ? i : -ERESTARTSYS;
		cond_resched();
		page = follow_page_mask(vma, start, foll_flags, &page_mask);
		if (!page) {
			int ret;
			ret = faultin_page(tsk, vma, start, &foll_flags,
					nonblocking);
			switch (ret) {
			case 0:
				goto retry;
			case -EFAULT:
			case -ENOMEM:
			case -EHWPOISON:
				return i ? i : ret;
			case -EBUSY:
				return i;
			case -ENOENT:
				goto next_page;
620
			}
621
			BUG();
622 623 624 625 626 627 628
		} else if (PTR_ERR(page) == -EEXIST) {
			/*
			 * Proper page table entry exists, but no corresponding
			 * struct page.
			 */
			goto next_page;
		} else if (IS_ERR(page)) {
629
			return i ? i : PTR_ERR(page);
630
		}
631 632 633 634 635
		if (pages) {
			pages[i] = page;
			flush_anon_page(vma, page, start);
			flush_dcache_page(page);
			page_mask = 0;
636 637
		}
next_page:
638 639 640 641 642 643 644 645 646 647
		if (vmas) {
			vmas[i] = vma;
			page_mask = 0;
		}
		page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
		if (page_increm > nr_pages)
			page_increm = nr_pages;
		i += page_increm;
		start += page_increm * PAGE_SIZE;
		nr_pages -= page_increm;
648 649 650 651
	} while (nr_pages);
	return i;
}

652 653
static bool vma_permits_fault(struct vm_area_struct *vma,
			      unsigned int fault_flags)
654
{
655 656
	bool write   = !!(fault_flags & FAULT_FLAG_WRITE);
	bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
657
	vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
658 659 660 661

	if (!(vm_flags & vma->vm_flags))
		return false;

662 663
	/*
	 * The architecture might have a hardware protection
664
	 * mechanism other than read/write that can deny access.
665 666 667
	 *
	 * gup always represents data access, not instruction
	 * fetches, so execute=false here:
668
	 */
669
	if (!arch_vma_access_permitted(vma, write, false, foreign))
670 671
		return false;

672 673 674
	return true;
}

675 676 677 678 679 680 681
/*
 * fixup_user_fault() - manually resolve a user page fault
 * @tsk:	the task_struct to use for page fault accounting, or
 *		NULL if faults are not to be recorded.
 * @mm:		mm_struct of target mm
 * @address:	user address
 * @fault_flags:flags to pass down to handle_mm_fault()
682 683
 * @unlocked:	did we unlock the mmap_sem while retrying, maybe NULL if caller
 *		does not allow retry
684 685 686 687 688 689 690 691 692 693 694
 *
 * This is meant to be called in the specific scenario where for locking reasons
 * we try to access user memory in atomic context (within a pagefault_disable()
 * section), this returns -EFAULT, and we want to resolve the user fault before
 * trying again.
 *
 * Typically this is meant to be used by the futex code.
 *
 * The main difference with get_user_pages() is that this function will
 * unconditionally call handle_mm_fault() which will in turn perform all the
 * necessary SW fixup of the dirty and young bits in the PTE, while
695
 * get_user_pages() only guarantees to update these in the struct page.
696 697 698 699 700 701
 *
 * This is important for some architectures where those bits also gate the
 * access permission to the page because they are maintained in software.  On
 * such architectures, gup() will not be enough to make a subsequent access
 * succeed.
 *
702 703
 * This function will not return with an unlocked mmap_sem. So it has not the
 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
704 705
 */
int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
706 707
		     unsigned long address, unsigned int fault_flags,
		     bool *unlocked)
708 709
{
	struct vm_area_struct *vma;
710 711 712 713
	int ret, major = 0;

	if (unlocked)
		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
714

715
retry:
716 717 718 719
	vma = find_extend_vma(mm, address);
	if (!vma || address < vma->vm_start)
		return -EFAULT;

720
	if (!vma_permits_fault(vma, fault_flags))
721 722
		return -EFAULT;

723
	ret = handle_mm_fault(vma, address, fault_flags);
724
	major |= ret & VM_FAULT_MAJOR;
725 726 727 728 729
	if (ret & VM_FAULT_ERROR) {
		if (ret & VM_FAULT_OOM)
			return -ENOMEM;
		if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
			return -EHWPOISON;
730
		if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
731 732 733
			return -EFAULT;
		BUG();
	}
734 735 736 737 738 739 740 741 742 743 744

	if (ret & VM_FAULT_RETRY) {
		down_read(&mm->mmap_sem);
		if (!(fault_flags & FAULT_FLAG_TRIED)) {
			*unlocked = true;
			fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
			fault_flags |= FAULT_FLAG_TRIED;
			goto retry;
		}
	}

745
	if (tsk) {
746
		if (major)
747 748 749 750 751 752
			tsk->maj_flt++;
		else
			tsk->min_flt++;
	}
	return 0;
}
753
EXPORT_SYMBOL_GPL(fixup_user_fault);
754

755 756 757 758 759 760
static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
						struct mm_struct *mm,
						unsigned long start,
						unsigned long nr_pages,
						struct page **pages,
						struct vm_area_struct **vmas,
761 762
						int *locked, bool notify_drop,
						unsigned int flags)
763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866
{
	long ret, pages_done;
	bool lock_dropped;

	if (locked) {
		/* if VM_FAULT_RETRY can be returned, vmas become invalid */
		BUG_ON(vmas);
		/* check caller initialized locked */
		BUG_ON(*locked != 1);
	}

	if (pages)
		flags |= FOLL_GET;

	pages_done = 0;
	lock_dropped = false;
	for (;;) {
		ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
				       vmas, locked);
		if (!locked)
			/* VM_FAULT_RETRY couldn't trigger, bypass */
			return ret;

		/* VM_FAULT_RETRY cannot return errors */
		if (!*locked) {
			BUG_ON(ret < 0);
			BUG_ON(ret >= nr_pages);
		}

		if (!pages)
			/* If it's a prefault don't insist harder */
			return ret;

		if (ret > 0) {
			nr_pages -= ret;
			pages_done += ret;
			if (!nr_pages)
				break;
		}
		if (*locked) {
			/* VM_FAULT_RETRY didn't trigger */
			if (!pages_done)
				pages_done = ret;
			break;
		}
		/* VM_FAULT_RETRY triggered, so seek to the faulting offset */
		pages += ret;
		start += ret << PAGE_SHIFT;

		/*
		 * Repeat on the address that fired VM_FAULT_RETRY
		 * without FAULT_FLAG_ALLOW_RETRY but with
		 * FAULT_FLAG_TRIED.
		 */
		*locked = 1;
		lock_dropped = true;
		down_read(&mm->mmap_sem);
		ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
				       pages, NULL, NULL);
		if (ret != 1) {
			BUG_ON(ret > 1);
			if (!pages_done)
				pages_done = ret;
			break;
		}
		nr_pages--;
		pages_done++;
		if (!nr_pages)
			break;
		pages++;
		start += PAGE_SIZE;
	}
	if (notify_drop && lock_dropped && *locked) {
		/*
		 * We must let the caller know we temporarily dropped the lock
		 * and so the critical section protected by it was lost.
		 */
		up_read(&mm->mmap_sem);
		*locked = 0;
	}
	return pages_done;
}

/*
 * We can leverage the VM_FAULT_RETRY functionality in the page fault
 * paths better by using either get_user_pages_locked() or
 * get_user_pages_unlocked().
 *
 * get_user_pages_locked() is suitable to replace the form:
 *
 *      down_read(&mm->mmap_sem);
 *      do_something()
 *      get_user_pages(tsk, mm, ..., pages, NULL);
 *      up_read(&mm->mmap_sem);
 *
 *  to:
 *
 *      int locked = 1;
 *      down_read(&mm->mmap_sem);
 *      do_something()
 *      get_user_pages_locked(tsk, mm, ..., pages, &locked);
 *      if (locked)
 *          up_read(&mm->mmap_sem);
 */
867
long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
868
			   unsigned int gup_flags, struct page **pages,
869 870
			   int *locked)
{
871
	return __get_user_pages_locked(current, current->mm, start, nr_pages,
872 873
				       pages, NULL, locked, true,
				       gup_flags | FOLL_TOUCH);
874
}
875
EXPORT_SYMBOL(get_user_pages_locked);
876

877
/*
878 879
 * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows for
 * tsk, mm to be specified.
880 881
 *
 * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
882 883
 * caller if required (just like with __get_user_pages). "FOLL_GET"
 * is set implicitly if "pages" is non-NULL.
884
 */
885 886 887 888
static __always_inline long __get_user_pages_unlocked(struct task_struct *tsk,
		struct mm_struct *mm, unsigned long start,
		unsigned long nr_pages, struct page **pages,
		unsigned int gup_flags)
889 890 891
{
	long ret;
	int locked = 1;
892

893
	down_read(&mm->mmap_sem);
894 895
	ret = __get_user_pages_locked(tsk, mm, start, nr_pages, pages, NULL,
				      &locked, false, gup_flags);
896 897 898 899 900
	if (locked)
		up_read(&mm->mmap_sem);
	return ret;
}

901 902 903 904 905 906 907 908 909 910 911 912
/*
 * get_user_pages_unlocked() is suitable to replace the form:
 *
 *      down_read(&mm->mmap_sem);
 *      get_user_pages(tsk, mm, ..., pages, NULL);
 *      up_read(&mm->mmap_sem);
 *
 *  with:
 *
 *      get_user_pages_unlocked(tsk, mm, ..., pages);
 *
 * It is functionally equivalent to get_user_pages_fast so
913 914
 * get_user_pages_fast should be used instead if specific gup_flags
 * (e.g. FOLL_FORCE) are not required.
915
 */
916
long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
917
			     struct page **pages, unsigned int gup_flags)
918
{
919
	return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
920
					 pages, gup_flags | FOLL_TOUCH);
921
}
922
EXPORT_SYMBOL(get_user_pages_unlocked);
923

924
/*
925
 * get_user_pages_remote() - pin user pages in memory
926 927 928 929 930
 * @tsk:	the task_struct to use for page fault accounting, or
 *		NULL if faults are not to be recorded.
 * @mm:		mm_struct of target mm
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
931
 * @gup_flags:	flags modifying lookup behaviour
932 933 934 935 936
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_pages long. Or NULL, if caller
 *		only intends to ensure the pages are faulted in.
 * @vmas:	array of pointers to vmas corresponding to each page.
 *		Or NULL if the caller does not require them.
937 938 939
 * @locked:	pointer to lock flag indicating whether lock is held and
 *		subsequently whether VM_FAULT_RETRY functionality can be
 *		utilised. Lock must initially be held.
940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962
 *
 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno. Each page returned must be released
 * with a put_page() call when it is finished with. vmas will only
 * remain valid while mmap_sem is held.
 *
 * Must be called with mmap_sem held for read or write.
 *
 * get_user_pages walks a process's page tables and takes a reference to
 * each struct page that each user address corresponds to at a given
 * instant. That is, it takes the page that would be accessed if a user
 * thread accesses the given user virtual address at that instant.
 *
 * This does not guarantee that the page exists in the user mappings when
 * get_user_pages returns, and there may even be a completely different
 * page there in some cases (eg. if mmapped pagecache has been invalidated
 * and subsequently re faulted). However it does guarantee that the page
 * won't be freed completely. And mostly callers simply care that the page
 * contains data that was valid *at some point in time*. Typically, an IO
 * or similar operation cannot guarantee anything stronger anyway because
 * locks can't be held over the syscall boundary.
 *
963 964 965
 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
 * be called after the page is finished with, and before put_page is called.
966 967 968 969 970 971 972 973
 *
 * get_user_pages is typically used for fewer-copy IO operations, to get a
 * handle on the memory by some means other than accesses via the user virtual
 * addresses. The pages may be submitted for DMA to devices or accessed via
 * their kernel linear mapping (via the kmap APIs). Care should be taken to
 * use the correct cache flushing APIs.
 *
 * See also get_user_pages_fast, for performance critical applications.
974 975 976 977 978
 *
 * get_user_pages should be phased out in favor of
 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
 * should use get_user_pages because it cannot pass
 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
979
 */
980 981
long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
		unsigned long start, unsigned long nr_pages,
982
		unsigned int gup_flags, struct page **pages,
983
		struct vm_area_struct **vmas, int *locked)
984
{
985
	return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
986
				       locked, true,
987
				       gup_flags | FOLL_TOUCH | FOLL_REMOTE);
988 989 990 991
}
EXPORT_SYMBOL(get_user_pages_remote);

/*
992 993
 * This is the same as get_user_pages_remote(), just with a
 * less-flexible calling convention where we assume that the task
994 995 996
 * and mm being operated on are the current task's and don't allow
 * passing of a locked parameter.  We also obviously don't pass
 * FOLL_REMOTE in here.
997
 */
998
long get_user_pages(unsigned long start, unsigned long nr_pages,
999
		unsigned int gup_flags, struct page **pages,
1000 1001
		struct vm_area_struct **vmas)
{
1002
	return __get_user_pages_locked(current, current->mm, start, nr_pages,
1003 1004
				       pages, vmas, NULL, false,
				       gup_flags | FOLL_TOUCH);
1005
}
1006
EXPORT_SYMBOL(get_user_pages);
1007

1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039
/**
 * populate_vma_page_range() -  populate a range of pages in the vma.
 * @vma:   target vma
 * @start: start address
 * @end:   end address
 * @nonblocking:
 *
 * This takes care of mlocking the pages too if VM_LOCKED is set.
 *
 * return 0 on success, negative error code on error.
 *
 * vma->vm_mm->mmap_sem must be held.
 *
 * If @nonblocking is NULL, it may be held for read or write and will
 * be unperturbed.
 *
 * If @nonblocking is non-NULL, it must held for read only and may be
 * released.  If it's released, *@nonblocking will be set to 0.
 */
long populate_vma_page_range(struct vm_area_struct *vma,
		unsigned long start, unsigned long end, int *nonblocking)
{
	struct mm_struct *mm = vma->vm_mm;
	unsigned long nr_pages = (end - start) / PAGE_SIZE;
	int gup_flags;

	VM_BUG_ON(start & ~PAGE_MASK);
	VM_BUG_ON(end   & ~PAGE_MASK);
	VM_BUG_ON_VMA(start < vma->vm_start, vma);
	VM_BUG_ON_VMA(end   > vma->vm_end, vma);
	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);

E
Eric B Munson 已提交
1040 1041 1042
	gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
	if (vma->vm_flags & VM_LOCKONFAULT)
		gup_flags &= ~FOLL_POPULATE;
1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127
	/*
	 * We want to touch writable mappings with a write fault in order
	 * to break COW, except for shared mappings because these don't COW
	 * and we would not want to dirty them for nothing.
	 */
	if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
		gup_flags |= FOLL_WRITE;

	/*
	 * We want mlock to succeed for regions that have any permissions
	 * other than PROT_NONE.
	 */
	if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
		gup_flags |= FOLL_FORCE;

	/*
	 * We made sure addr is within a VMA, so the following will
	 * not result in a stack expansion that recurses back here.
	 */
	return __get_user_pages(current, mm, start, nr_pages, gup_flags,
				NULL, NULL, nonblocking);
}

/*
 * __mm_populate - populate and/or mlock pages within a range of address space.
 *
 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
 * flags. VMAs must be already marked with the desired vm_flags, and
 * mmap_sem must not be held.
 */
int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
{
	struct mm_struct *mm = current->mm;
	unsigned long end, nstart, nend;
	struct vm_area_struct *vma = NULL;
	int locked = 0;
	long ret = 0;

	VM_BUG_ON(start & ~PAGE_MASK);
	VM_BUG_ON(len != PAGE_ALIGN(len));
	end = start + len;

	for (nstart = start; nstart < end; nstart = nend) {
		/*
		 * We want to fault in pages for [nstart; end) address range.
		 * Find first corresponding VMA.
		 */
		if (!locked) {
			locked = 1;
			down_read(&mm->mmap_sem);
			vma = find_vma(mm, nstart);
		} else if (nstart >= vma->vm_end)
			vma = vma->vm_next;
		if (!vma || vma->vm_start >= end)
			break;
		/*
		 * Set [nstart; nend) to intersection of desired address
		 * range with the first VMA. Also, skip undesirable VMA types.
		 */
		nend = min(end, vma->vm_end);
		if (vma->vm_flags & (VM_IO | VM_PFNMAP))
			continue;
		if (nstart < vma->vm_start)
			nstart = vma->vm_start;
		/*
		 * Now fault in a range of pages. populate_vma_page_range()
		 * double checks the vma flags, so that it won't mlock pages
		 * if the vma was already munlocked.
		 */
		ret = populate_vma_page_range(vma, nstart, nend, &locked);
		if (ret < 0) {
			if (ignore_errors) {
				ret = 0;
				continue;	/* continue at next VMA */
			}
			break;
		}
		nend = nstart + ret * PAGE_SIZE;
		ret = 0;
	}
	if (locked)
		up_read(&mm->mmap_sem);
	return ret;	/* 0 or negative error code */
}

1128 1129 1130 1131 1132
/**
 * get_dump_page() - pin user page in memory while writing it to core dump
 * @addr: user address
 *
 * Returns struct page pointer of user page pinned for dump,
1133
 * to be freed afterwards by put_page().
1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155
 *
 * Returns NULL on any kind of failure - a hole must then be inserted into
 * the corefile, to preserve alignment with its headers; and also returns
 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
 * allowing a hole to be left in the corefile to save diskspace.
 *
 * Called without mmap_sem, but after all other threads have been killed.
 */
#ifdef CONFIG_ELF_CORE
struct page *get_dump_page(unsigned long addr)
{
	struct vm_area_struct *vma;
	struct page *page;

	if (__get_user_pages(current, current->mm, addr, 1,
			     FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
			     NULL) < 1)
		return NULL;
	flush_cache_page(vma, addr, page_to_pfn(page));
	return page;
}
#endif /* CONFIG_ELF_CORE */
1156 1157

/*
1158
 * Generic RCU Fast GUP
1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178
 *
 * get_user_pages_fast attempts to pin user pages by walking the page
 * tables directly and avoids taking locks. Thus the walker needs to be
 * protected from page table pages being freed from under it, and should
 * block any THP splits.
 *
 * One way to achieve this is to have the walker disable interrupts, and
 * rely on IPIs from the TLB flushing code blocking before the page table
 * pages are freed. This is unsuitable for architectures that do not need
 * to broadcast an IPI when invalidating TLBs.
 *
 * Another way to achieve this is to batch up page table containing pages
 * belonging to more than one mm_user, then rcu_sched a callback to free those
 * pages. Disabling interrupts will allow the fast_gup walker to both block
 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
 * (which is a relatively rare event). The code below adopts this strategy.
 *
 * Before activating this code, please be aware that the following assumptions
 * are currently made:
 *
1179 1180
 *  *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
 *      pages containing page tables.
1181 1182 1183 1184 1185 1186 1187 1188 1189
 *
 *  *) ptes can be read atomically by the architecture.
 *
 *  *) access_ok is sufficient to validate userspace address ranges.
 *
 * The last two assumptions can be relaxed by the addition of helper functions.
 *
 * This code is based heavily on the PowerPC implementation by Nick Piggin.
 */
1190
#ifdef CONFIG_HAVE_GENERIC_RCU_GUP
1191

1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202
#ifndef gup_get_pte
/*
 * We assume that the PTE can be read atomically. If this is not the case for
 * your architecture, please provide the helper.
 */
static inline pte_t gup_get_pte(pte_t *ptep)
{
	return READ_ONCE(*ptep);
}
#endif

1203 1204 1205 1206 1207 1208 1209 1210 1211 1212
static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
{
	while ((*nr) - nr_start) {
		struct page *page = pages[--(*nr)];

		ClearPageReferenced(page);
		put_page(page);
	}
}

1213 1214 1215 1216
#ifdef __HAVE_ARCH_PTE_SPECIAL
static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
			 int write, struct page **pages, int *nr)
{
1217 1218
	struct dev_pagemap *pgmap = NULL;
	int nr_start = *nr, ret = 0;
1219 1220 1221 1222
	pte_t *ptep, *ptem;

	ptem = ptep = pte_offset_map(&pmd, addr);
	do {
1223
		pte_t pte = gup_get_pte(ptep);
1224
		struct page *head, *page;
1225 1226 1227

		/*
		 * Similar to the PMD case below, NUMA hinting must take slow
1228
		 * path using the pte_protnone check.
1229
		 */
1230 1231 1232 1233 1234 1235
		if (pte_protnone(pte))
			goto pte_unmap;

		if (!pte_access_permitted(pte, write))
			goto pte_unmap;

1236 1237 1238 1239 1240 1241 1242
		if (pte_devmap(pte)) {
			pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
			if (unlikely(!pgmap)) {
				undo_dev_pagemap(nr, nr_start, pages);
				goto pte_unmap;
			}
		} else if (pte_special(pte))
1243 1244 1245 1246
			goto pte_unmap;

		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
		page = pte_page(pte);
1247
		head = compound_head(page);
1248

1249
		if (!page_cache_get_speculative(head))
1250 1251 1252
			goto pte_unmap;

		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
1253
			put_page(head);
1254 1255 1256
			goto pte_unmap;
		}

1257
		VM_BUG_ON_PAGE(compound_head(page) != head, page);
1258

1259
		put_dev_pagemap(pgmap);
1260
		SetPageReferenced(page);
1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289
		pages[*nr] = page;
		(*nr)++;

	} while (ptep++, addr += PAGE_SIZE, addr != end);

	ret = 1;

pte_unmap:
	pte_unmap(ptem);
	return ret;
}
#else

/*
 * If we can't determine whether or not a pte is special, then fail immediately
 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
 * to be special.
 *
 * For a futex to be placed on a THP tail page, get_futex_key requires a
 * __get_user_pages_fast implementation that can pin pages. Thus it's still
 * useful to have gup_huge_pmd even if we can't operate on ptes.
 */
static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
			 int write, struct page **pages, int *nr)
{
	return 0;
}
#endif /* __HAVE_ARCH_PTE_SPECIAL */

1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347
#ifdef __HAVE_ARCH_PTE_DEVMAP
static int __gup_device_huge(unsigned long pfn, unsigned long addr,
		unsigned long end, struct page **pages, int *nr)
{
	int nr_start = *nr;
	struct dev_pagemap *pgmap = NULL;

	do {
		struct page *page = pfn_to_page(pfn);

		pgmap = get_dev_pagemap(pfn, pgmap);
		if (unlikely(!pgmap)) {
			undo_dev_pagemap(nr, nr_start, pages);
			return 0;
		}
		SetPageReferenced(page);
		pages[*nr] = page;
		get_page(page);
		put_dev_pagemap(pgmap);
		(*nr)++;
		pfn++;
	} while (addr += PAGE_SIZE, addr != end);
	return 1;
}

static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
		unsigned long end, struct page **pages, int *nr)
{
	unsigned long fault_pfn;

	fault_pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
	return __gup_device_huge(fault_pfn, addr, end, pages, nr);
}

static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
		unsigned long end, struct page **pages, int *nr)
{
	unsigned long fault_pfn;

	fault_pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
	return __gup_device_huge(fault_pfn, addr, end, pages, nr);
}
#else
static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
		unsigned long end, struct page **pages, int *nr)
{
	BUILD_BUG();
	return 0;
}

static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
		unsigned long end, struct page **pages, int *nr)
{
	BUILD_BUG();
	return 0;
}
#endif

1348 1349 1350
static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
		unsigned long end, int write, struct page **pages, int *nr)
{
1351
	struct page *head, *page;
1352 1353
	int refs;

1354
	if (!pmd_access_permitted(orig, write))
1355 1356
		return 0;

1357 1358 1359
	if (pmd_devmap(orig))
		return __gup_device_huge_pmd(orig, addr, end, pages, nr);

1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382
	refs = 0;
	head = pmd_page(orig);
	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
	do {
		VM_BUG_ON_PAGE(compound_head(page) != head, page);
		pages[*nr] = page;
		(*nr)++;
		page++;
		refs++;
	} while (addr += PAGE_SIZE, addr != end);

	if (!page_cache_add_speculative(head, refs)) {
		*nr -= refs;
		return 0;
	}

	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
		*nr -= refs;
		while (refs--)
			put_page(head);
		return 0;
	}

1383
	SetPageReferenced(head);
1384 1385 1386 1387 1388 1389
	return 1;
}

static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
		unsigned long end, int write, struct page **pages, int *nr)
{
1390
	struct page *head, *page;
1391 1392
	int refs;

1393
	if (!pud_access_permitted(orig, write))
1394 1395
		return 0;

1396 1397 1398
	if (pud_devmap(orig))
		return __gup_device_huge_pud(orig, addr, end, pages, nr);

1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421
	refs = 0;
	head = pud_page(orig);
	page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
	do {
		VM_BUG_ON_PAGE(compound_head(page) != head, page);
		pages[*nr] = page;
		(*nr)++;
		page++;
		refs++;
	} while (addr += PAGE_SIZE, addr != end);

	if (!page_cache_add_speculative(head, refs)) {
		*nr -= refs;
		return 0;
	}

	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
		*nr -= refs;
		while (refs--)
			put_page(head);
		return 0;
	}

1422
	SetPageReferenced(head);
1423 1424 1425
	return 1;
}

1426 1427 1428 1429 1430
static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
			unsigned long end, int write,
			struct page **pages, int *nr)
{
	int refs;
1431
	struct page *head, *page;
1432

1433
	if (!pgd_access_permitted(orig, write))
1434 1435
		return 0;

1436
	BUILD_BUG_ON(pgd_devmap(orig));
1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459
	refs = 0;
	head = pgd_page(orig);
	page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
	do {
		VM_BUG_ON_PAGE(compound_head(page) != head, page);
		pages[*nr] = page;
		(*nr)++;
		page++;
		refs++;
	} while (addr += PAGE_SIZE, addr != end);

	if (!page_cache_add_speculative(head, refs)) {
		*nr -= refs;
		return 0;
	}

	if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
		*nr -= refs;
		while (refs--)
			put_page(head);
		return 0;
	}

1460
	SetPageReferenced(head);
1461 1462 1463
	return 1;
}

1464 1465 1466 1467 1468 1469 1470 1471
static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
		int write, struct page **pages, int *nr)
{
	unsigned long next;
	pmd_t *pmdp;

	pmdp = pmd_offset(&pud, addr);
	do {
1472
		pmd_t pmd = READ_ONCE(*pmdp);
1473 1474

		next = pmd_addr_end(addr, end);
1475
		if (pmd_none(pmd))
1476 1477 1478 1479 1480 1481 1482 1483
			return 0;

		if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {
			/*
			 * NUMA hinting faults need to be handled in the GUP
			 * slowpath for accounting purposes and so that they
			 * can be serialised against THP migration.
			 */
1484
			if (pmd_protnone(pmd))
1485 1486 1487 1488 1489 1490
				return 0;

			if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
				pages, nr))
				return 0;

1491 1492 1493 1494 1495 1496 1497 1498
		} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
			/*
			 * architecture have different format for hugetlbfs
			 * pmd format and THP pmd format
			 */
			if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
					 PMD_SHIFT, next, write, pages, nr))
				return 0;
1499 1500 1501 1502 1503 1504 1505
		} else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
				return 0;
	} while (pmdp++, addr = next, addr != end);

	return 1;
}

1506
static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
1507
			 int write, struct page **pages, int *nr)
1508 1509 1510 1511
{
	unsigned long next;
	pud_t *pudp;

1512
	pudp = pud_offset(&p4d, addr);
1513
	do {
1514
		pud_t pud = READ_ONCE(*pudp);
1515 1516 1517 1518

		next = pud_addr_end(addr, end);
		if (pud_none(pud))
			return 0;
1519
		if (unlikely(pud_huge(pud))) {
1520
			if (!gup_huge_pud(pud, pudp, addr, next, write,
1521 1522 1523 1524 1525
					  pages, nr))
				return 0;
		} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
			if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
					 PUD_SHIFT, next, write, pages, nr))
1526 1527 1528 1529 1530 1531 1532 1533
				return 0;
		} else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
			return 0;
	} while (pudp++, addr = next, addr != end);

	return 1;
}

1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551
static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
			 int write, struct page **pages, int *nr)
{
	unsigned long next;
	p4d_t *p4dp;

	p4dp = p4d_offset(&pgd, addr);
	do {
		p4d_t p4d = READ_ONCE(*p4dp);

		next = p4d_addr_end(addr, end);
		if (p4d_none(p4d))
			return 0;
		BUILD_BUG_ON(p4d_huge(p4d));
		if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
			if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
					 P4D_SHIFT, next, write, pages, nr))
				return 0;
1552
		} else if (!gup_pud_range(p4d, addr, next, write, pages, nr))
1553 1554 1555 1556 1557 1558
			return 0;
	} while (p4dp++, addr = next, addr != end);

	return 1;
}

1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595
/*
 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
 * the regular GUP. It will only return non-negative values.
 */
int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
			  struct page **pages)
{
	struct mm_struct *mm = current->mm;
	unsigned long addr, len, end;
	unsigned long next, flags;
	pgd_t *pgdp;
	int nr = 0;

	start &= PAGE_MASK;
	addr = start;
	len = (unsigned long) nr_pages << PAGE_SHIFT;
	end = start + len;

	if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
					start, len)))
		return 0;

	/*
	 * Disable interrupts.  We use the nested form as we can already have
	 * interrupts disabled by get_futex_key.
	 *
	 * With interrupts disabled, we block page table pages from being
	 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h
	 * for more details.
	 *
	 * We do not adopt an rcu_read_lock(.) here as we also want to
	 * block IPIs that come from THPs splitting.
	 */

	local_irq_save(flags);
	pgdp = pgd_offset(mm, addr);
	do {
1596
		pgd_t pgd = READ_ONCE(*pgdp);
1597

1598
		next = pgd_addr_end(addr, end);
1599
		if (pgd_none(pgd))
1600
			break;
1601 1602 1603 1604 1605 1606 1607 1608
		if (unlikely(pgd_huge(pgd))) {
			if (!gup_huge_pgd(pgd, pgdp, addr, next, write,
					  pages, &nr))
				break;
		} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
			if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
					 PGDIR_SHIFT, next, write, pages, &nr))
				break;
1609
		} else if (!gup_p4d_range(pgd, addr, next, write, pages, &nr))
1610 1611 1612 1613 1614 1615 1616
			break;
	} while (pgdp++, addr = next, addr != end);
	local_irq_restore(flags);

	return nr;
}

1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631
#ifndef gup_fast_permitted
/*
 * Check if it's allowed to use __get_user_pages_fast() for the range, or
 * we need to fall back to the slow version:
 */
bool gup_fast_permitted(unsigned long start, int nr_pages, int write)
{
	unsigned long len, end;

	len = (unsigned long) nr_pages << PAGE_SHIFT;
	end = start + len;
	return end >= start;
}
#endif

1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650
/**
 * get_user_pages_fast() - pin user pages in memory
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
 * @write:	whether pages will be written to
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_pages long.
 *
 * Attempt to pin user pages in memory without taking mm->mmap_sem.
 * If not successful, it will fall back to taking the lock and
 * calling get_user_pages().
 *
 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno.
 */
int get_user_pages_fast(unsigned long start, int nr_pages, int write,
			struct page **pages)
{
1651
	int nr = 0, ret = 0;
1652 1653

	start &= PAGE_MASK;
1654 1655 1656 1657 1658

	if (gup_fast_permitted(start, nr_pages, write)) {
		nr = __get_user_pages_fast(start, nr_pages, write, pages);
		ret = nr;
	}
1659 1660 1661 1662 1663 1664

	if (nr < nr_pages) {
		/* Try to get the remaining pages with get_user_pages */
		start += nr << PAGE_SHIFT;
		pages += nr;

1665 1666
		ret = get_user_pages_unlocked(start, nr_pages - nr, pages,
				write ? FOLL_WRITE : 0);
1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679

		/* Have to be a bit careful with return values */
		if (nr > 0) {
			if (ret < 0)
				ret = nr;
			else
				ret += nr;
		}
	}

	return ret;
}

1680
#endif /* CONFIG_HAVE_GENERIC_RCU_GUP */