mm: move get_user_pages()-related code to separate file
authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Wed, 4 Jun 2014 23:08:10 +0000 (16:08 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 4 Jun 2014 23:54:04 +0000 (16:54 -0700)
mm/memory.c is overloaded: over 4k lines. get_user_pages() code is
pretty much self-contained let's move it to separate file.

No other changes made.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/Makefile
mm/gup.c [new file with mode: 0644]
mm/internal.h
mm/memory.c

index 0173940..4064f3e 100644 (file)
@@ -3,7 +3,7 @@
 #
 
 mmu-y                  := nommu.o
-mmu-$(CONFIG_MMU)      := fremap.o highmem.o madvise.o memory.o mincore.o \
+mmu-$(CONFIG_MMU)      := fremap.o gup.o highmem.o madvise.o memory.o mincore.o \
                           mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
                           vmalloc.o pagewalk.o pgtable-generic.o
 
diff --git a/mm/gup.c b/mm/gup.c
new file mode 100644 (file)
index 0000000..ea88b65
--- /dev/null
+++ b/mm/gup.c
@@ -0,0 +1,649 @@
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/spinlock.h>
+
+#include <linux/hugetlb.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/rmap.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+
+#include "internal.h"
+
+/**
+ * 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;
+       pud_t *pud;
+       pmd_t *pmd;
+       pte_t *ptep, pte;
+       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);
+               goto out;
+       }
+
+       page = NULL;
+       pgd = pgd_offset(mm, address);
+       if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
+               goto no_page_table;
+
+       pud = pud_offset(pgd, address);
+       if (pud_none(*pud))
+               goto no_page_table;
+       if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
+               if (flags & FOLL_GET)
+                       goto out;
+               page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
+               goto out;
+       }
+       if (unlikely(pud_bad(*pud)))
+               goto no_page_table;
+
+       pmd = pmd_offset(pud, address);
+       if (pmd_none(*pmd))
+               goto no_page_table;
+       if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
+               page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
+               if (flags & FOLL_GET) {
+                       /*
+                        * Refcount on tail pages are not well-defined and
+                        * shouldn't be taken. The caller should handle a NULL
+                        * return when trying to follow tail pages.
+                        */
+                       if (PageHead(page))
+                               get_page(page);
+                       else {
+                               page = NULL;
+                               goto out;
+                       }
+               }
+               goto out;
+       }
+       if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
+               goto no_page_table;
+       if (pmd_trans_huge(*pmd)) {
+               if (flags & FOLL_SPLIT) {
+                       split_huge_page_pmd(vma, address, pmd);
+                       goto split_fallthrough;
+               }
+               ptl = pmd_lock(mm, pmd);
+               if (likely(pmd_trans_huge(*pmd))) {
+                       if (unlikely(pmd_trans_splitting(*pmd))) {
+                               spin_unlock(ptl);
+                               wait_split_huge_page(vma->anon_vma, pmd);
+                       } else {
+                               page = follow_trans_huge_pmd(vma, address,
+                                                            pmd, flags);
+                               spin_unlock(ptl);
+                               *page_mask = HPAGE_PMD_NR - 1;
+                               goto out;
+                       }
+               } else
+                       spin_unlock(ptl);
+               /* fall through */
+       }
+split_fallthrough:
+       if (unlikely(pmd_bad(*pmd)))
+               goto no_page_table;
+
+       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;
+               if (pte_none(pte) || pte_file(pte))
+                       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);
+               goto split_fallthrough;
+       }
+       if ((flags & FOLL_NUMA) && pte_numa(pte))
+               goto no_page;
+       if ((flags & FOLL_WRITE) && !pte_write(pte))
+               goto unlock;
+
+       page = vm_normal_page(vma, address, pte);
+       if (unlikely(!page)) {
+               if ((flags & FOLL_DUMP) ||
+                   !is_zero_pfn(pte_pfn(pte)))
+                       goto bad_page;
+               page = pte_page(pte);
+       }
+
+       if (flags & FOLL_GET)
+               get_page_foll(page);
+       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);
+       }
+       if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
+               /*
+                * 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);
+               }
+       }
+unlock:
+       pte_unmap_unlock(ptep, ptl);
+out:
+       return page;
+
+bad_page:
+       pte_unmap_unlock(ptep, ptl);
+       return ERR_PTR(-EFAULT);
+
+no_page:
+       pte_unmap_unlock(ptep, ptl);
+       if (!pte_none(pte))
+               return page;
+
+no_page_table:
+       /*
+        * 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 page;
+}
+
+static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
+{
+       return stack_guard_page_start(vma, addr) ||
+              stack_guard_page_end(vma, addr+PAGE_SIZE);
+}
+
+/**
+ * __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.
+ *
+ * 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.
+ *
+ * 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,
+ * *@nonblocking will be set to 0.
+ *
+ * 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.
+ */
+long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+               unsigned long start, unsigned long nr_pages,
+               unsigned int gup_flags, struct page **pages,
+               struct vm_area_struct **vmas, int *nonblocking)
+{
+       long i;
+       unsigned long vm_flags;
+       unsigned int page_mask;
+
+       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;
+
+       i = 0;
+
+       do {
+               struct vm_area_struct *vma;
+
+               vma = find_extend_vma(mm, start);
+               if (!vma && in_gate_area(mm, start)) {
+                       unsigned long pg = start & PAGE_MASK;
+                       pgd_t *pgd;
+                       pud_t *pud;
+                       pmd_t *pmd;
+                       pte_t *pte;
+
+                       /* user gate pages are read-only */
+                       if (gup_flags & FOLL_WRITE)
+                               goto efault;
+                       if (pg > TASK_SIZE)
+                               pgd = pgd_offset_k(pg);
+                       else
+                               pgd = pgd_offset_gate(mm, pg);
+                       BUG_ON(pgd_none(*pgd));
+                       pud = pud_offset(pgd, pg);
+                       BUG_ON(pud_none(*pud));
+                       pmd = pmd_offset(pud, pg);
+                       if (pmd_none(*pmd))
+                               goto efault;
+                       VM_BUG_ON(pmd_trans_huge(*pmd));
+                       pte = pte_offset_map(pmd, pg);
+                       if (pte_none(*pte)) {
+                               pte_unmap(pte);
+                               goto efault;
+                       }
+                       vma = get_gate_vma(mm);
+                       if (pages) {
+                               struct page *page;
+
+                               page = vm_normal_page(vma, start, *pte);
+                               if (!page) {
+                                       if (!(gup_flags & FOLL_DUMP) &&
+                                            is_zero_pfn(pte_pfn(*pte)))
+                                               page = pte_page(*pte);
+                                       else {
+                                               pte_unmap(pte);
+                                               goto efault;
+                                       }
+                               }
+                               pages[i] = page;
+                               get_page(page);
+                       }
+                       pte_unmap(pte);
+                       page_mask = 0;
+                       goto next_page;
+               }
+
+               if (!vma)
+                       goto efault;
+               vm_flags = vma->vm_flags;
+               if (vm_flags & (VM_IO | VM_PFNMAP))
+                       goto efault;
+
+               if (gup_flags & FOLL_WRITE) {
+                       if (!(vm_flags & VM_WRITE)) {
+                               if (!(gup_flags & FOLL_FORCE))
+                                       goto 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.
+                                */
+                               if (!is_cow_mapping(vm_flags)) {
+                                       WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
+                                       goto efault;
+                               }
+                       }
+               } else {
+                       if (!(vm_flags & VM_READ)) {
+                               if (!(gup_flags & FOLL_FORCE))
+                                       goto efault;
+                               /*
+                                * Is there actually any vma we can reach here
+                                * which does not have VM_MAYREAD set?
+                                */
+                               if (!(vm_flags & VM_MAYREAD))
+                                       goto efault;
+                       }
+               }
+
+               if (is_vm_hugetlb_page(vma)) {
+                       i = follow_hugetlb_page(mm, vma, pages, vmas,
+                                       &start, &nr_pages, i, gup_flags);
+                       continue;
+               }
+
+               do {
+                       struct page *page;
+                       unsigned int foll_flags = gup_flags;
+                       unsigned int page_increm;
+
+                       /*
+                        * 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();
+                       while (!(page = follow_page_mask(vma, start,
+                                               foll_flags, &page_mask))) {
+                               int ret;
+                               unsigned int fault_flags = 0;
+
+                               /* For mlock, just skip the stack guard page. */
+                               if (foll_flags & FOLL_MLOCK) {
+                                       if (stack_guard_page(vma, start))
+                                               goto next_page;
+                               }
+                               if (foll_flags & FOLL_WRITE)
+                                       fault_flags |= FAULT_FLAG_WRITE;
+                               if (nonblocking)
+                                       fault_flags |= FAULT_FLAG_ALLOW_RETRY;
+                               if (foll_flags & FOLL_NOWAIT)
+                                       fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
+
+                               ret = handle_mm_fault(mm, vma, start,
+                                                       fault_flags);
+
+                               if (ret & VM_FAULT_ERROR) {
+                                       if (ret & VM_FAULT_OOM)
+                                               return i ? i : -ENOMEM;
+                                       if (ret & (VM_FAULT_HWPOISON |
+                                                  VM_FAULT_HWPOISON_LARGE)) {
+                                               if (i)
+                                                       return i;
+                                               else if (gup_flags & FOLL_HWPOISON)
+                                                       return -EHWPOISON;
+                                               else
+                                                       return -EFAULT;
+                                       }
+                                       if (ret & VM_FAULT_SIGBUS)
+                                               goto 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 i;
+                               }
+
+                               /*
+                                * 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))
+                                       foll_flags &= ~FOLL_WRITE;
+
+                               cond_resched();
+                       }
+                       if (IS_ERR(page))
+                               return i ? i : PTR_ERR(page);
+                       if (pages) {
+                               pages[i] = page;
+
+                               flush_anon_page(vma, page, start);
+                               flush_dcache_page(page);
+                               page_mask = 0;
+                       }
+next_page:
+                       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;
+               } while (nr_pages && start < vma->vm_end);
+       } while (nr_pages);
+       return i;
+efault:
+       return i ? : -EFAULT;
+}
+EXPORT_SYMBOL(__get_user_pages);
+
+/*
+ * 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()
+ *
+ * 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
+ * handle_mm_fault() only guarantees to update these in the struct page.
+ *
+ * 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.
+ *
+ * This should be called with the mm_sem held for read.
+ */
+int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
+                    unsigned long address, unsigned int fault_flags)
+{
+       struct vm_area_struct *vma;
+       vm_flags_t vm_flags;
+       int ret;
+
+       vma = find_extend_vma(mm, address);
+       if (!vma || address < vma->vm_start)
+               return -EFAULT;
+
+       vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
+       if (!(vm_flags & vma->vm_flags))
+               return -EFAULT;
+
+       ret = handle_mm_fault(mm, vma, address, fault_flags);
+       if (ret & VM_FAULT_ERROR) {
+               if (ret & VM_FAULT_OOM)
+                       return -ENOMEM;
+               if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
+                       return -EHWPOISON;
+               if (ret & VM_FAULT_SIGBUS)
+                       return -EFAULT;
+               BUG();
+       }
+       if (tsk) {
+               if (ret & VM_FAULT_MAJOR)
+                       tsk->maj_flt++;
+               else
+                       tsk->min_flt++;
+       }
+       return 0;
+}
+
+/*
+ * get_user_pages() - pin user pages in memory
+ * @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
+ * @write:     whether pages will be written to by the caller
+ * @force:     whether to force access even when user mapping is currently
+ *             protected (but never forces write access to shared mapping).
+ * @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.
+ *
+ * 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.
+ *
+ * If 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.
+ *
+ * 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.
+ */
+long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+               unsigned long start, unsigned long nr_pages, int write,
+               int force, struct page **pages, struct vm_area_struct **vmas)
+{
+       int flags = FOLL_TOUCH;
+
+       if (pages)
+               flags |= FOLL_GET;
+       if (write)
+               flags |= FOLL_WRITE;
+       if (force)
+               flags |= FOLL_FORCE;
+
+       return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
+                               NULL);
+}
+EXPORT_SYMBOL(get_user_pages);
+
+/**
+ * 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,
+ * to be freed afterwards by page_cache_release() or put_page().
+ *
+ * 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 */
index 07b6736..6ee580d 100644 (file)
@@ -169,6 +169,11 @@ static inline unsigned long page_order(struct page *page)
        return page_private(page);
 }
 
+static inline bool is_cow_mapping(vm_flags_t flags)
+{
+       return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
+}
+
 /* mm/util.c */
 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
                struct vm_area_struct *prev, struct rb_node *rb_parent);
index 0897830..7049d39 100644 (file)
@@ -698,11 +698,6 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
        add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 }
 
-static inline bool is_cow_mapping(vm_flags_t flags)
-{
-       return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
-}
-
 /*
  * vm_normal_page -- This function gets the "struct page" associated with a pte.
  *
@@ -1458,642 +1453,6 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
 }
 EXPORT_SYMBOL_GPL(zap_vma_ptes);
 
-/**
- * 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;
-       pud_t *pud;
-       pmd_t *pmd;
-       pte_t *ptep, pte;
-       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);
-               goto out;
-       }
-
-       page = NULL;
-       pgd = pgd_offset(mm, address);
-       if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
-               goto no_page_table;
-
-       pud = pud_offset(pgd, address);
-       if (pud_none(*pud))
-               goto no_page_table;
-       if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
-               if (flags & FOLL_GET)
-                       goto out;
-               page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
-               goto out;
-       }
-       if (unlikely(pud_bad(*pud)))
-               goto no_page_table;
-
-       pmd = pmd_offset(pud, address);
-       if (pmd_none(*pmd))
-               goto no_page_table;
-       if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
-               page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
-               if (flags & FOLL_GET) {
-                       /*
-                        * Refcount on tail pages are not well-defined and
-                        * shouldn't be taken. The caller should handle a NULL
-                        * return when trying to follow tail pages.
-                        */
-                       if (PageHead(page))
-                               get_page(page);
-                       else {
-                               page = NULL;
-                               goto out;
-                       }
-               }
-               goto out;
-       }
-       if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
-               goto no_page_table;
-       if (pmd_trans_huge(*pmd)) {
-               if (flags & FOLL_SPLIT) {
-                       split_huge_page_pmd(vma, address, pmd);
-                       goto split_fallthrough;
-               }
-               ptl = pmd_lock(mm, pmd);
-               if (likely(pmd_trans_huge(*pmd))) {
-                       if (unlikely(pmd_trans_splitting(*pmd))) {
-                               spin_unlock(ptl);
-                               wait_split_huge_page(vma->anon_vma, pmd);
-                       } else {
-                               page = follow_trans_huge_pmd(vma, address,
-                                                            pmd, flags);
-                               spin_unlock(ptl);
-                               *page_mask = HPAGE_PMD_NR - 1;
-                               goto out;
-                       }
-               } else
-                       spin_unlock(ptl);
-               /* fall through */
-       }
-split_fallthrough:
-       if (unlikely(pmd_bad(*pmd)))
-               goto no_page_table;
-
-       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;
-               if (pte_none(pte) || pte_file(pte))
-                       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);
-               goto split_fallthrough;
-       }
-       if ((flags & FOLL_NUMA) && pte_numa(pte))
-               goto no_page;
-       if ((flags & FOLL_WRITE) && !pte_write(pte))
-               goto unlock;
-
-       page = vm_normal_page(vma, address, pte);
-       if (unlikely(!page)) {
-               if ((flags & FOLL_DUMP) ||
-                   !is_zero_pfn(pte_pfn(pte)))
-                       goto bad_page;
-               page = pte_page(pte);
-       }
-
-       if (flags & FOLL_GET)
-               get_page_foll(page);
-       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);
-       }
-       if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
-               /*
-                * 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);
-               }
-       }
-unlock:
-       pte_unmap_unlock(ptep, ptl);
-out:
-       return page;
-
-bad_page:
-       pte_unmap_unlock(ptep, ptl);
-       return ERR_PTR(-EFAULT);
-
-no_page:
-       pte_unmap_unlock(ptep, ptl);
-       if (!pte_none(pte))
-               return page;
-
-no_page_table:
-       /*
-        * 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 page;
-}
-
-static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
-{
-       return stack_guard_page_start(vma, addr) ||
-              stack_guard_page_end(vma, addr+PAGE_SIZE);
-}
-
-/**
- * __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.
- *
- * 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.
- *
- * 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,
- * *@nonblocking will be set to 0.
- *
- * 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.
- */
-long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
-               unsigned long start, unsigned long nr_pages,
-               unsigned int gup_flags, struct page **pages,
-               struct vm_area_struct **vmas, int *nonblocking)
-{
-       long i;
-       unsigned long vm_flags;
-       unsigned int page_mask;
-
-       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;
-
-       i = 0;
-
-       do {
-               struct vm_area_struct *vma;
-
-               vma = find_extend_vma(mm, start);
-               if (!vma && in_gate_area(mm, start)) {
-                       unsigned long pg = start & PAGE_MASK;
-                       pgd_t *pgd;
-                       pud_t *pud;
-                       pmd_t *pmd;
-                       pte_t *pte;
-
-                       /* user gate pages are read-only */
-                       if (gup_flags & FOLL_WRITE)
-                               goto efault;
-                       if (pg > TASK_SIZE)
-                               pgd = pgd_offset_k(pg);
-                       else
-                               pgd = pgd_offset_gate(mm, pg);
-                       BUG_ON(pgd_none(*pgd));
-                       pud = pud_offset(pgd, pg);
-                       BUG_ON(pud_none(*pud));
-                       pmd = pmd_offset(pud, pg);
-                       if (pmd_none(*pmd))
-                               goto efault;
-                       VM_BUG_ON(pmd_trans_huge(*pmd));
-                       pte = pte_offset_map(pmd, pg);
-                       if (pte_none(*pte)) {
-                               pte_unmap(pte);
-                               goto efault;
-                       }
-                       vma = get_gate_vma(mm);
-                       if (pages) {
-                               struct page *page;
-
-                               page = vm_normal_page(vma, start, *pte);
-                               if (!page) {
-                                       if (!(gup_flags & FOLL_DUMP) &&
-                                            is_zero_pfn(pte_pfn(*pte)))
-                                               page = pte_page(*pte);
-                                       else {
-                                               pte_unmap(pte);
-                                               goto efault;
-                                       }
-                               }
-                               pages[i] = page;
-                               get_page(page);
-                       }
-                       pte_unmap(pte);
-                       page_mask = 0;
-                       goto next_page;
-               }
-
-               if (!vma)
-                       goto efault;
-               vm_flags = vma->vm_flags;
-               if (vm_flags & (VM_IO | VM_PFNMAP))
-                       goto efault;
-
-               if (gup_flags & FOLL_WRITE) {
-                       if (!(vm_flags & VM_WRITE)) {
-                               if (!(gup_flags & FOLL_FORCE))
-                                       goto 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.
-                                */
-                               if (!is_cow_mapping(vm_flags)) {
-                                       WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
-                                       goto efault;
-                               }
-                       }
-               } else {
-                       if (!(vm_flags & VM_READ)) {
-                               if (!(gup_flags & FOLL_FORCE))
-                                       goto efault;
-                               /*
-                                * Is there actually any vma we can reach here
-                                * which does not have VM_MAYREAD set?
-                                */
-                               if (!(vm_flags & VM_MAYREAD))
-                                       goto efault;
-                       }
-               }
-
-               if (is_vm_hugetlb_page(vma)) {
-                       i = follow_hugetlb_page(mm, vma, pages, vmas,
-                                       &start, &nr_pages, i, gup_flags);
-                       continue;
-               }
-
-               do {
-                       struct page *page;
-                       unsigned int foll_flags = gup_flags;
-                       unsigned int page_increm;
-
-                       /*
-                        * 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();
-                       while (!(page = follow_page_mask(vma, start,
-                                               foll_flags, &page_mask))) {
-                               int ret;
-                               unsigned int fault_flags = 0;
-
-                               /* For mlock, just skip the stack guard page. */
-                               if (foll_flags & FOLL_MLOCK) {
-                                       if (stack_guard_page(vma, start))
-                                               goto next_page;
-                               }
-                               if (foll_flags & FOLL_WRITE)
-                                       fault_flags |= FAULT_FLAG_WRITE;
-                               if (nonblocking)
-                                       fault_flags |= FAULT_FLAG_ALLOW_RETRY;
-                               if (foll_flags & FOLL_NOWAIT)
-                                       fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
-
-                               ret = handle_mm_fault(mm, vma, start,
-                                                       fault_flags);
-
-                               if (ret & VM_FAULT_ERROR) {
-                                       if (ret & VM_FAULT_OOM)
-                                               return i ? i : -ENOMEM;
-                                       if (ret & (VM_FAULT_HWPOISON |
-                                                  VM_FAULT_HWPOISON_LARGE)) {
-                                               if (i)
-                                                       return i;
-                                               else if (gup_flags & FOLL_HWPOISON)
-                                                       return -EHWPOISON;
-                                               else
-                                                       return -EFAULT;
-                                       }
-                                       if (ret & VM_FAULT_SIGBUS)
-                                               goto 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 i;
-                               }
-
-                               /*
-                                * 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))
-                                       foll_flags &= ~FOLL_WRITE;
-
-                               cond_resched();
-                       }
-                       if (IS_ERR(page))
-                               return i ? i : PTR_ERR(page);
-                       if (pages) {
-                               pages[i] = page;
-
-                               flush_anon_page(vma, page, start);
-                               flush_dcache_page(page);
-                               page_mask = 0;
-                       }
-next_page:
-                       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;
-               } while (nr_pages && start < vma->vm_end);
-       } while (nr_pages);
-       return i;
-efault:
-       return i ? : -EFAULT;
-}
-EXPORT_SYMBOL(__get_user_pages);
-
-/*
- * 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()
- *
- * 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
- * handle_mm_fault() only guarantees to update these in the struct page.
- *
- * 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.
- *
- * This should be called with the mm_sem held for read.
- */
-int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
-                    unsigned long address, unsigned int fault_flags)
-{
-       struct vm_area_struct *vma;
-       vm_flags_t vm_flags;
-       int ret;
-
-       vma = find_extend_vma(mm, address);
-       if (!vma || address < vma->vm_start)
-               return -EFAULT;
-
-       vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
-       if (!(vm_flags & vma->vm_flags))
-               return -EFAULT;
-
-       ret = handle_mm_fault(mm, vma, address, fault_flags);
-       if (ret & VM_FAULT_ERROR) {
-               if (ret & VM_FAULT_OOM)
-                       return -ENOMEM;
-               if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
-                       return -EHWPOISON;
-               if (ret & VM_FAULT_SIGBUS)
-                       return -EFAULT;
-               BUG();
-       }
-       if (tsk) {
-               if (ret & VM_FAULT_MAJOR)
-                       tsk->maj_flt++;
-               else
-                       tsk->min_flt++;
-       }
-       return 0;
-}
-
-/*
- * get_user_pages() - pin user pages in memory
- * @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
- * @write:     whether pages will be written to by the caller
- * @force:     whether to force access even when user mapping is currently
- *             protected (but never forces write access to shared mapping).
- * @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.
- *
- * 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.
- *
- * If 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.
- *
- * 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.
- */
-long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
-               unsigned long start, unsigned long nr_pages, int write,
-               int force, struct page **pages, struct vm_area_struct **vmas)
-{
-       int flags = FOLL_TOUCH;
-
-       if (pages)
-               flags |= FOLL_GET;
-       if (write)
-               flags |= FOLL_WRITE;
-       if (force)
-               flags |= FOLL_FORCE;
-
-       return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
-                               NULL);
-}
-EXPORT_SYMBOL(get_user_pages);
-
-/**
- * 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,
- * to be freed afterwards by page_cache_release() or put_page().
- *
- * 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 */
-
 pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
                        spinlock_t **ptl)
 {