![Linus Torvalds](/assets/img/avatar_default.png)
This reverts commits5c9d2d5c26
,c7da82b894
, ande7fe7b5cae
. We'll probably need to revisit this, but basically we should not complicate the get_user_pages_fast() case, and checking the actual page table protection key bits will require more care anyway, since the protection keys depend on the exact state of the VM in question. Particularly when doing a "remote" page lookup (ie in somebody elses VM, not your own), you need to be much more careful than this was. Dave Hansen says: "So, the underlying bug here is that we now a get_user_pages_remote() and then go ahead and do the p*_access_permitted() checks against the current PKRU. This was introduced recently with the addition of the new p??_access_permitted() calls. We have checks in the VMA path for the "remote" gups and we avoid consulting PKRU for them. This got missed in the pkeys selftests because I did a ptrace read, but not a *write*. I also didn't explicitly test it against something where a COW needed to be done" It's also not entirely clear that it makes sense to check the protection key bits at this level at all. But one possible eventual solution is to make the get_user_pages_fast() case just abort if it sees protection key bits set, which makes us fall back to the regular get_user_pages() case, which then has a vma and can do the check there if we want to. We'll see. Somewhat related to this all: what we _do_ want to do some day is to check the PAGE_USER bit - it should obviously always be set for user pages, but it would be a good check to have back. Because we have no generic way to test for it, we lost it as part of moving over from the architecture-specific x86 GUP implementation to the generic one in commite585513b76
("x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation"). Cc: Peter Zijlstra <peterz@infradead.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: "Jérôme Glisse" <jglisse@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1851 lines
50 KiB
C
1851 lines
50 KiB
C
#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/err.h>
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#include <linux/spinlock.h>
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#include <linux/mm.h>
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#include <linux/memremap.h>
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#include <linux/pagemap.h>
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#include <linux/rmap.h>
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#include <linux/swap.h>
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#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,
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unsigned int flags)
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{
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/*
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* When core dumping an enormous anonymous area that nobody
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* has touched so far, we don't want to allocate unnecessary pages or
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* page tables. Return error instead of NULL to skip handle_mm_fault,
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* then get_dump_page() will return NULL to leave a hole in the dump.
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* But we can only make this optimization where a hole would surely
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* be zero-filled if handle_mm_fault() actually did handle it.
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*/
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if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault))
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return ERR_PTR(-EFAULT);
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return NULL;
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}
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static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
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pte_t *pte, unsigned int flags)
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{
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/* No page to get reference */
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if (flags & FOLL_GET)
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return -EFAULT;
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if (flags & FOLL_TOUCH) {
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pte_t entry = *pte;
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if (flags & FOLL_WRITE)
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entry = pte_mkdirty(entry);
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entry = pte_mkyoung(entry);
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if (!pte_same(*pte, entry)) {
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set_pte_at(vma->vm_mm, address, pte, entry);
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update_mmu_cache(vma, address, pte);
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}
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}
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/* Proper page table entry exists, but no corresponding struct page */
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return -EEXIST;
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}
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/*
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* FOLL_FORCE can write to even unwritable pte's, but only
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* after we've gone through a COW cycle and they are dirty.
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*/
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static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
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{
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return pte_write(pte) ||
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((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
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}
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static struct page *follow_page_pte(struct vm_area_struct *vma,
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unsigned long address, pmd_t *pmd, unsigned int flags)
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{
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struct mm_struct *mm = vma->vm_mm;
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struct dev_pagemap *pgmap = NULL;
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struct page *page;
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spinlock_t *ptl;
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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);
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pte = *ptep;
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if (!pte_present(pte)) {
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swp_entry_t entry;
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/*
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* KSM's break_ksm() relies upon recognizing a ksm page
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* even while it is being migrated, so for that case we
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* need migration_entry_wait().
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*/
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if (likely(!(flags & FOLL_MIGRATION)))
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goto no_page;
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if (pte_none(pte))
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goto no_page;
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entry = pte_to_swp_entry(pte);
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if (!is_migration_entry(entry))
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goto no_page;
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pte_unmap_unlock(ptep, ptl);
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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);
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return NULL;
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}
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page = vm_normal_page(vma, address, pte);
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if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
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/*
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* Only return device mapping pages in the FOLL_GET case since
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* they are only valid while holding the pgmap reference.
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*/
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pgmap = get_dev_pagemap(pte_pfn(pte), NULL);
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if (pgmap)
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page = pte_page(pte);
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else
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goto no_page;
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} else if (unlikely(!page)) {
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if (flags & FOLL_DUMP) {
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/* Avoid special (like zero) pages in core dumps */
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page = ERR_PTR(-EFAULT);
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goto out;
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}
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if (is_zero_pfn(pte_pfn(pte))) {
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page = pte_page(pte);
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} else {
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int ret;
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ret = follow_pfn_pte(vma, address, ptep, flags);
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page = ERR_PTR(ret);
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goto out;
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}
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}
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if (flags & FOLL_SPLIT && PageTransCompound(page)) {
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int ret;
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get_page(page);
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pte_unmap_unlock(ptep, ptl);
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lock_page(page);
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ret = split_huge_page(page);
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unlock_page(page);
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put_page(page);
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if (ret)
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return ERR_PTR(ret);
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goto retry;
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}
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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 */
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if (pgmap) {
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put_dev_pagemap(pgmap);
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pgmap = NULL;
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}
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}
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if (flags & FOLL_TOUCH) {
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if ((flags & FOLL_WRITE) &&
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!pte_dirty(pte) && !PageDirty(page))
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set_page_dirty(page);
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/*
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* pte_mkyoung() would be more correct here, but atomic care
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* is needed to avoid losing the dirty bit: it is easier to use
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* mark_page_accessed().
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*/
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mark_page_accessed(page);
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}
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if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
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/* Do not mlock pte-mapped THP */
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if (PageTransCompound(page))
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goto out;
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/*
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* The preliminary mapping check is mainly to avoid the
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* pointless overhead of lock_page on the ZERO_PAGE
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* which might bounce very badly if there is contention.
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*
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* If the page is already locked, we don't need to
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* handle it now - vmscan will handle it later if and
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* when it attempts to reclaim the page.
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*/
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if (page->mapping && trylock_page(page)) {
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lru_add_drain(); /* push cached pages to LRU */
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/*
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* Because we lock page here, and migration is
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* blocked by the pte's page reference, and we
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* know the page is still mapped, we don't even
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* need to check for file-cache page truncation.
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*/
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mlock_vma_page(page);
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unlock_page(page);
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}
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}
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out:
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pte_unmap_unlock(ptep, ptl);
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return page;
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no_page:
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pte_unmap_unlock(ptep, ptl);
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if (!pte_none(pte))
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return NULL;
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return no_page_table(vma, flags);
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}
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static struct page *follow_pmd_mask(struct vm_area_struct *vma,
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unsigned long address, pud_t *pudp,
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unsigned int flags, unsigned int *page_mask)
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{
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pmd_t *pmd;
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spinlock_t *ptl;
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struct page *page;
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struct mm_struct *mm = vma->vm_mm;
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pmd = pmd_offset(pudp, address);
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if (pmd_none(*pmd))
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return no_page_table(vma, flags);
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if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
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page = follow_huge_pmd(mm, address, pmd, flags);
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if (page)
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return page;
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return no_page_table(vma, flags);
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}
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if (is_hugepd(__hugepd(pmd_val(*pmd)))) {
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page = follow_huge_pd(vma, address,
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__hugepd(pmd_val(*pmd)), flags,
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PMD_SHIFT);
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if (page)
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return page;
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return no_page_table(vma, flags);
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}
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retry:
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if (!pmd_present(*pmd)) {
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if (likely(!(flags & FOLL_MIGRATION)))
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return no_page_table(vma, flags);
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VM_BUG_ON(thp_migration_supported() &&
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!is_pmd_migration_entry(*pmd));
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if (is_pmd_migration_entry(*pmd))
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pmd_migration_entry_wait(mm, pmd);
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goto retry;
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}
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if (pmd_devmap(*pmd)) {
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ptl = pmd_lock(mm, pmd);
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page = follow_devmap_pmd(vma, address, pmd, flags);
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spin_unlock(ptl);
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if (page)
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return page;
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}
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if (likely(!pmd_trans_huge(*pmd)))
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return follow_page_pte(vma, address, pmd, flags);
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if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
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return no_page_table(vma, flags);
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retry_locked:
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ptl = pmd_lock(mm, pmd);
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if (unlikely(!pmd_present(*pmd))) {
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spin_unlock(ptl);
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if (likely(!(flags & FOLL_MIGRATION)))
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return no_page_table(vma, flags);
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pmd_migration_entry_wait(mm, pmd);
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goto retry_locked;
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}
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if (unlikely(!pmd_trans_huge(*pmd))) {
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spin_unlock(ptl);
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return follow_page_pte(vma, address, pmd, flags);
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}
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if (flags & FOLL_SPLIT) {
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int ret;
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page = pmd_page(*pmd);
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if (is_huge_zero_page(page)) {
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spin_unlock(ptl);
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ret = 0;
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split_huge_pmd(vma, pmd, address);
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if (pmd_trans_unstable(pmd))
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ret = -EBUSY;
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} else {
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get_page(page);
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spin_unlock(ptl);
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lock_page(page);
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ret = split_huge_page(page);
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unlock_page(page);
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put_page(page);
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if (pmd_none(*pmd))
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return no_page_table(vma, flags);
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}
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return ret ? ERR_PTR(ret) :
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follow_page_pte(vma, address, pmd, flags);
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}
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page = follow_trans_huge_pmd(vma, address, pmd, flags);
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spin_unlock(ptl);
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*page_mask = HPAGE_PMD_NR - 1;
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return page;
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}
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static struct page *follow_pud_mask(struct vm_area_struct *vma,
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unsigned long address, p4d_t *p4dp,
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unsigned int flags, unsigned int *page_mask)
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{
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pud_t *pud;
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spinlock_t *ptl;
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struct page *page;
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struct mm_struct *mm = vma->vm_mm;
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pud = pud_offset(p4dp, address);
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if (pud_none(*pud))
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return no_page_table(vma, flags);
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if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
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page = follow_huge_pud(mm, address, pud, flags);
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if (page)
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return page;
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return no_page_table(vma, flags);
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}
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if (is_hugepd(__hugepd(pud_val(*pud)))) {
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page = follow_huge_pd(vma, address,
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__hugepd(pud_val(*pud)), flags,
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PUD_SHIFT);
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if (page)
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return page;
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return no_page_table(vma, flags);
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}
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if (pud_devmap(*pud)) {
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ptl = pud_lock(mm, pud);
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page = follow_devmap_pud(vma, address, pud, flags);
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spin_unlock(ptl);
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if (page)
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return page;
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}
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if (unlikely(pud_bad(*pud)))
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return no_page_table(vma, flags);
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return follow_pmd_mask(vma, address, pud, flags, page_mask);
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}
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static struct page *follow_p4d_mask(struct vm_area_struct *vma,
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unsigned long address, pgd_t *pgdp,
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unsigned int flags, unsigned int *page_mask)
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{
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p4d_t *p4d;
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struct page *page;
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p4d = p4d_offset(pgdp, address);
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if (p4d_none(*p4d))
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return no_page_table(vma, flags);
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BUILD_BUG_ON(p4d_huge(*p4d));
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if (unlikely(p4d_bad(*p4d)))
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return no_page_table(vma, flags);
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if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
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page = follow_huge_pd(vma, address,
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__hugepd(p4d_val(*p4d)), flags,
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P4D_SHIFT);
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if (page)
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return page;
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return no_page_table(vma, flags);
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}
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return follow_pud_mask(vma, address, p4d, flags, page_mask);
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}
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/**
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* follow_page_mask - look up a page descriptor from a user-virtual address
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* @vma: vm_area_struct mapping @address
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* @address: virtual address to look up
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* @flags: flags modifying lookup behaviour
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* @page_mask: on output, *page_mask is set according to the size of the page
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*
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* @flags can have FOLL_ flags set, defined in <linux/mm.h>
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*
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* Returns the mapped (struct page *), %NULL if no mapping exists, or
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* an error pointer if there is a mapping to something not represented
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* by a page descriptor (see also vm_normal_page()).
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*/
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struct page *follow_page_mask(struct vm_area_struct *vma,
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unsigned long address, unsigned int flags,
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unsigned int *page_mask)
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{
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pgd_t *pgd;
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struct page *page;
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struct mm_struct *mm = vma->vm_mm;
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*page_mask = 0;
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/* make this handle hugepd */
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page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
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if (!IS_ERR(page)) {
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BUG_ON(flags & FOLL_GET);
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return page;
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}
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pgd = pgd_offset(mm, address);
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if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
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return no_page_table(vma, flags);
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if (pgd_huge(*pgd)) {
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page = follow_huge_pgd(mm, address, pgd, flags);
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if (page)
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return page;
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return no_page_table(vma, flags);
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}
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if (is_hugepd(__hugepd(pgd_val(*pgd)))) {
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page = follow_huge_pd(vma, address,
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__hugepd(pgd_val(*pgd)), flags,
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PGDIR_SHIFT);
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if (page)
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return page;
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return no_page_table(vma, flags);
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}
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return follow_p4d_mask(vma, address, pgd, flags, page_mask);
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}
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|
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static int get_gate_page(struct mm_struct *mm, unsigned long address,
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unsigned int gup_flags, struct vm_area_struct **vma,
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struct page **page)
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{
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pgd_t *pgd;
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p4d_t *p4d;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte;
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int ret = -EFAULT;
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|
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/* user gate pages are read-only */
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if (gup_flags & FOLL_WRITE)
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return -EFAULT;
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if (address > TASK_SIZE)
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pgd = pgd_offset_k(address);
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else
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pgd = pgd_offset_gate(mm, address);
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BUG_ON(pgd_none(*pgd));
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p4d = p4d_offset(pgd, address);
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BUG_ON(p4d_none(*p4d));
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pud = pud_offset(p4d, address);
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BUG_ON(pud_none(*pud));
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pmd = pmd_offset(pud, address);
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if (!pmd_present(*pmd))
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return -EFAULT;
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VM_BUG_ON(pmd_trans_huge(*pmd));
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pte = pte_offset_map(pmd, address);
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if (pte_none(*pte))
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goto unmap;
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*vma = get_gate_vma(mm);
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if (!page)
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goto out;
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*page = vm_normal_page(*vma, address, *pte);
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if (!*page) {
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if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
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goto unmap;
|
|
*page = pte_page(*pte);
|
|
|
|
/*
|
|
* This should never happen (a device public page in the gate
|
|
* area).
|
|
*/
|
|
if (is_device_public_page(*page))
|
|
goto unmap;
|
|
}
|
|
get_page(*page);
|
|
out:
|
|
ret = 0;
|
|
unmap:
|
|
pte_unmap(pte);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
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;
|
|
|
|
/* mlock all present pages, but do not fault in new pages */
|
|
if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
|
|
return -ENOENT;
|
|
if (*flags & FOLL_WRITE)
|
|
fault_flags |= FAULT_FLAG_WRITE;
|
|
if (*flags & FOLL_REMOTE)
|
|
fault_flags |= FAULT_FLAG_REMOTE;
|
|
if (nonblocking)
|
|
fault_flags |= FAULT_FLAG_ALLOW_RETRY;
|
|
if (*flags & FOLL_NOWAIT)
|
|
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
|
|
if (*flags & FOLL_TRIED) {
|
|
VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
|
|
fault_flags |= FAULT_FLAG_TRIED;
|
|
}
|
|
|
|
ret = handle_mm_fault(vma, address, fault_flags);
|
|
if (ret & VM_FAULT_ERROR) {
|
|
int err = vm_fault_to_errno(ret, *flags);
|
|
|
|
if (err)
|
|
return err;
|
|
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))
|
|
*flags |= FOLL_COW;
|
|
return 0;
|
|
}
|
|
|
|
static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
|
|
{
|
|
vm_flags_t vm_flags = vma->vm_flags;
|
|
int write = (gup_flags & FOLL_WRITE);
|
|
int foreign = (gup_flags & FOLL_REMOTE);
|
|
|
|
if (vm_flags & (VM_IO | VM_PFNMAP))
|
|
return -EFAULT;
|
|
|
|
if (write) {
|
|
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.
|
|
*/
|
|
if (!is_cow_mapping(vm_flags))
|
|
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;
|
|
}
|
|
/*
|
|
* gups are always data accesses, not instruction
|
|
* fetches, so execute=false here
|
|
*/
|
|
if (!arch_vma_access_permitted(vma, write, false, foreign))
|
|
return -EFAULT;
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* __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. It may be released. See below.
|
|
*
|
|
* __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. 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.
|
|
*
|
|
* 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.
|
|
*/
|
|
static 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 = 0;
|
|
unsigned int page_mask;
|
|
struct vm_area_struct *vma = NULL;
|
|
|
|
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 {
|
|
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;
|
|
}
|
|
|
|
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,
|
|
gup_flags, nonblocking);
|
|
continue;
|
|
}
|
|
}
|
|
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;
|
|
}
|
|
BUG();
|
|
} else if (PTR_ERR(page) == -EEXIST) {
|
|
/*
|
|
* Proper page table entry exists, but no corresponding
|
|
* struct page.
|
|
*/
|
|
goto next_page;
|
|
} else 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);
|
|
return i;
|
|
}
|
|
|
|
static bool vma_permits_fault(struct vm_area_struct *vma,
|
|
unsigned int fault_flags)
|
|
{
|
|
bool write = !!(fault_flags & FAULT_FLAG_WRITE);
|
|
bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
|
|
vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
|
|
|
|
if (!(vm_flags & vma->vm_flags))
|
|
return false;
|
|
|
|
/*
|
|
* The architecture might have a hardware protection
|
|
* mechanism other than read/write that can deny access.
|
|
*
|
|
* gup always represents data access, not instruction
|
|
* fetches, so execute=false here:
|
|
*/
|
|
if (!arch_vma_access_permitted(vma, write, false, foreign))
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* 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()
|
|
* @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
|
|
* does not allow retry
|
|
*
|
|
* 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
|
|
* get_user_pages() 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 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().
|
|
*/
|
|
int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
|
|
unsigned long address, unsigned int fault_flags,
|
|
bool *unlocked)
|
|
{
|
|
struct vm_area_struct *vma;
|
|
int ret, major = 0;
|
|
|
|
if (unlocked)
|
|
fault_flags |= FAULT_FLAG_ALLOW_RETRY;
|
|
|
|
retry:
|
|
vma = find_extend_vma(mm, address);
|
|
if (!vma || address < vma->vm_start)
|
|
return -EFAULT;
|
|
|
|
if (!vma_permits_fault(vma, fault_flags))
|
|
return -EFAULT;
|
|
|
|
ret = handle_mm_fault(vma, address, fault_flags);
|
|
major |= ret & VM_FAULT_MAJOR;
|
|
if (ret & VM_FAULT_ERROR) {
|
|
int err = vm_fault_to_errno(ret, 0);
|
|
|
|
if (err)
|
|
return err;
|
|
BUG();
|
|
}
|
|
|
|
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;
|
|
}
|
|
}
|
|
|
|
if (tsk) {
|
|
if (major)
|
|
tsk->maj_flt++;
|
|
else
|
|
tsk->min_flt++;
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(fixup_user_fault);
|
|
|
|
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,
|
|
int *locked, bool notify_drop,
|
|
unsigned int flags)
|
|
{
|
|
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);
|
|
*/
|
|
long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
|
|
unsigned int gup_flags, struct page **pages,
|
|
int *locked)
|
|
{
|
|
return __get_user_pages_locked(current, current->mm, start, nr_pages,
|
|
pages, NULL, locked, true,
|
|
gup_flags | FOLL_TOUCH);
|
|
}
|
|
EXPORT_SYMBOL(get_user_pages_locked);
|
|
|
|
/*
|
|
* Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows for
|
|
* tsk, mm to be specified.
|
|
*
|
|
* NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
|
|
* caller if required (just like with __get_user_pages). "FOLL_GET"
|
|
* is set implicitly if "pages" is non-NULL.
|
|
*/
|
|
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)
|
|
{
|
|
long ret;
|
|
int locked = 1;
|
|
|
|
down_read(&mm->mmap_sem);
|
|
ret = __get_user_pages_locked(tsk, mm, start, nr_pages, pages, NULL,
|
|
&locked, false, gup_flags);
|
|
if (locked)
|
|
up_read(&mm->mmap_sem);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* 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
|
|
* get_user_pages_fast should be used instead if specific gup_flags
|
|
* (e.g. FOLL_FORCE) are not required.
|
|
*/
|
|
long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
|
|
struct page **pages, unsigned int gup_flags)
|
|
{
|
|
return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
|
|
pages, gup_flags | FOLL_TOUCH);
|
|
}
|
|
EXPORT_SYMBOL(get_user_pages_unlocked);
|
|
|
|
/*
|
|
* get_user_pages_remote() - 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
|
|
* @gup_flags: flags modifying lookup 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.
|
|
* @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.
|
|
*
|
|
* 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.
|
|
*
|
|
* 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.
|
|
*
|
|
* 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.
|
|
*/
|
|
long get_user_pages_remote(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 *locked)
|
|
{
|
|
return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
|
|
locked, true,
|
|
gup_flags | FOLL_TOUCH | FOLL_REMOTE);
|
|
}
|
|
EXPORT_SYMBOL(get_user_pages_remote);
|
|
|
|
/*
|
|
* This is the same as get_user_pages_remote(), just with a
|
|
* less-flexible calling convention where we assume that the task
|
|
* 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.
|
|
*/
|
|
long get_user_pages(unsigned long start, unsigned long nr_pages,
|
|
unsigned int gup_flags, struct page **pages,
|
|
struct vm_area_struct **vmas)
|
|
{
|
|
return __get_user_pages_locked(current, current->mm, start, nr_pages,
|
|
pages, vmas, NULL, false,
|
|
gup_flags | FOLL_TOUCH);
|
|
}
|
|
EXPORT_SYMBOL(get_user_pages);
|
|
|
|
#ifdef CONFIG_FS_DAX
|
|
/*
|
|
* This is the same as get_user_pages() in that it assumes we are
|
|
* operating on the current task's mm, but it goes further to validate
|
|
* that the vmas associated with the address range are suitable for
|
|
* longterm elevated page reference counts. For example, filesystem-dax
|
|
* mappings are subject to the lifetime enforced by the filesystem and
|
|
* we need guarantees that longterm users like RDMA and V4L2 only
|
|
* establish mappings that have a kernel enforced revocation mechanism.
|
|
*
|
|
* "longterm" == userspace controlled elevated page count lifetime.
|
|
* Contrast this to iov_iter_get_pages() usages which are transient.
|
|
*/
|
|
long get_user_pages_longterm(unsigned long start, unsigned long nr_pages,
|
|
unsigned int gup_flags, struct page **pages,
|
|
struct vm_area_struct **vmas_arg)
|
|
{
|
|
struct vm_area_struct **vmas = vmas_arg;
|
|
struct vm_area_struct *vma_prev = NULL;
|
|
long rc, i;
|
|
|
|
if (!pages)
|
|
return -EINVAL;
|
|
|
|
if (!vmas) {
|
|
vmas = kcalloc(nr_pages, sizeof(struct vm_area_struct *),
|
|
GFP_KERNEL);
|
|
if (!vmas)
|
|
return -ENOMEM;
|
|
}
|
|
|
|
rc = get_user_pages(start, nr_pages, gup_flags, pages, vmas);
|
|
|
|
for (i = 0; i < rc; i++) {
|
|
struct vm_area_struct *vma = vmas[i];
|
|
|
|
if (vma == vma_prev)
|
|
continue;
|
|
|
|
vma_prev = vma;
|
|
|
|
if (vma_is_fsdax(vma))
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Either get_user_pages() failed, or the vma validation
|
|
* succeeded, in either case we don't need to put_page() before
|
|
* returning.
|
|
*/
|
|
if (i >= rc)
|
|
goto out;
|
|
|
|
for (i = 0; i < rc; i++)
|
|
put_page(pages[i]);
|
|
rc = -EOPNOTSUPP;
|
|
out:
|
|
if (vmas != vmas_arg)
|
|
kfree(vmas);
|
|
return rc;
|
|
}
|
|
EXPORT_SYMBOL(get_user_pages_longterm);
|
|
#endif /* CONFIG_FS_DAX */
|
|
|
|
/**
|
|
* 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);
|
|
|
|
gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
|
|
if (vma->vm_flags & VM_LOCKONFAULT)
|
|
gup_flags &= ~FOLL_POPULATE;
|
|
/*
|
|
* 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 */
|
|
}
|
|
|
|
/**
|
|
* 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 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 */
|
|
|
|
/*
|
|
* Generic Fast GUP
|
|
*
|
|
* 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:
|
|
*
|
|
* *) Either HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
|
|
* free pages containing page tables or TLB flushing requires IPI broadcast.
|
|
*
|
|
* *) 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.
|
|
*/
|
|
#ifdef CONFIG_HAVE_GENERIC_GUP
|
|
|
|
#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
|
|
|
|
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);
|
|
}
|
|
}
|
|
|
|
#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)
|
|
{
|
|
struct dev_pagemap *pgmap = NULL;
|
|
int nr_start = *nr, ret = 0;
|
|
pte_t *ptep, *ptem;
|
|
|
|
ptem = ptep = pte_offset_map(&pmd, addr);
|
|
do {
|
|
pte_t pte = gup_get_pte(ptep);
|
|
struct page *head, *page;
|
|
|
|
/*
|
|
* Similar to the PMD case below, NUMA hinting must take slow
|
|
* path using the pte_protnone check.
|
|
*/
|
|
if (pte_protnone(pte))
|
|
goto pte_unmap;
|
|
|
|
if (!pte_access_permitted(pte, write))
|
|
goto pte_unmap;
|
|
|
|
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))
|
|
goto pte_unmap;
|
|
|
|
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
|
|
page = pte_page(pte);
|
|
head = compound_head(page);
|
|
|
|
if (!page_cache_get_speculative(head))
|
|
goto pte_unmap;
|
|
|
|
if (unlikely(pte_val(pte) != pte_val(*ptep))) {
|
|
put_page(head);
|
|
goto pte_unmap;
|
|
}
|
|
|
|
VM_BUG_ON_PAGE(compound_head(page) != head, page);
|
|
|
|
put_dev_pagemap(pgmap);
|
|
SetPageReferenced(page);
|
|
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 */
|
|
|
|
#if defined(__HAVE_ARCH_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
|
|
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
|
|
|
|
static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
|
|
unsigned long end, int write, struct page **pages, int *nr)
|
|
{
|
|
struct page *head, *page;
|
|
int refs;
|
|
|
|
if (!pmd_access_permitted(orig, write))
|
|
return 0;
|
|
|
|
if (pmd_devmap(orig))
|
|
return __gup_device_huge_pmd(orig, addr, end, pages, nr);
|
|
|
|
refs = 0;
|
|
page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
|
|
do {
|
|
pages[*nr] = page;
|
|
(*nr)++;
|
|
page++;
|
|
refs++;
|
|
} while (addr += PAGE_SIZE, addr != end);
|
|
|
|
head = compound_head(pmd_page(orig));
|
|
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;
|
|
}
|
|
|
|
SetPageReferenced(head);
|
|
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)
|
|
{
|
|
struct page *head, *page;
|
|
int refs;
|
|
|
|
if (!pud_access_permitted(orig, write))
|
|
return 0;
|
|
|
|
if (pud_devmap(orig))
|
|
return __gup_device_huge_pud(orig, addr, end, pages, nr);
|
|
|
|
refs = 0;
|
|
page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
|
|
do {
|
|
pages[*nr] = page;
|
|
(*nr)++;
|
|
page++;
|
|
refs++;
|
|
} while (addr += PAGE_SIZE, addr != end);
|
|
|
|
head = compound_head(pud_page(orig));
|
|
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;
|
|
}
|
|
|
|
SetPageReferenced(head);
|
|
return 1;
|
|
}
|
|
|
|
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;
|
|
struct page *head, *page;
|
|
|
|
if (!pgd_access_permitted(orig, write))
|
|
return 0;
|
|
|
|
BUILD_BUG_ON(pgd_devmap(orig));
|
|
refs = 0;
|
|
page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
|
|
do {
|
|
pages[*nr] = page;
|
|
(*nr)++;
|
|
page++;
|
|
refs++;
|
|
} while (addr += PAGE_SIZE, addr != end);
|
|
|
|
head = compound_head(pgd_page(orig));
|
|
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;
|
|
}
|
|
|
|
SetPageReferenced(head);
|
|
return 1;
|
|
}
|
|
|
|
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 {
|
|
pmd_t pmd = READ_ONCE(*pmdp);
|
|
|
|
next = pmd_addr_end(addr, end);
|
|
if (!pmd_present(pmd))
|
|
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.
|
|
*/
|
|
if (pmd_protnone(pmd))
|
|
return 0;
|
|
|
|
if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
|
|
pages, nr))
|
|
return 0;
|
|
|
|
} 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;
|
|
} else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
|
|
return 0;
|
|
} while (pmdp++, addr = next, addr != end);
|
|
|
|
return 1;
|
|
}
|
|
|
|
static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
|
|
int write, struct page **pages, int *nr)
|
|
{
|
|
unsigned long next;
|
|
pud_t *pudp;
|
|
|
|
pudp = pud_offset(&p4d, addr);
|
|
do {
|
|
pud_t pud = READ_ONCE(*pudp);
|
|
|
|
next = pud_addr_end(addr, end);
|
|
if (pud_none(pud))
|
|
return 0;
|
|
if (unlikely(pud_huge(pud))) {
|
|
if (!gup_huge_pud(pud, pudp, addr, next, write,
|
|
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))
|
|
return 0;
|
|
} else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
|
|
return 0;
|
|
} while (pudp++, addr = next, addr != end);
|
|
|
|
return 1;
|
|
}
|
|
|
|
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;
|
|
} else if (!gup_pud_range(p4d, addr, next, write, pages, nr))
|
|
return 0;
|
|
} while (p4dp++, addr = next, addr != end);
|
|
|
|
return 1;
|
|
}
|
|
|
|
static void gup_pgd_range(unsigned long addr, unsigned long end,
|
|
int write, struct page **pages, int *nr)
|
|
{
|
|
unsigned long next;
|
|
pgd_t *pgdp;
|
|
|
|
pgdp = pgd_offset(current->mm, addr);
|
|
do {
|
|
pgd_t pgd = READ_ONCE(*pgdp);
|
|
|
|
next = pgd_addr_end(addr, end);
|
|
if (pgd_none(pgd))
|
|
return;
|
|
if (unlikely(pgd_huge(pgd))) {
|
|
if (!gup_huge_pgd(pgd, pgdp, addr, next, write,
|
|
pages, nr))
|
|
return;
|
|
} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
|
|
if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
|
|
PGDIR_SHIFT, next, write, pages, nr))
|
|
return;
|
|
} else if (!gup_p4d_range(pgd, addr, next, write, pages, nr))
|
|
return;
|
|
} while (pgdp++, addr = next, addr != end);
|
|
}
|
|
|
|
#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
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
unsigned long addr, len, end;
|
|
unsigned long flags;
|
|
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,
|
|
(void __user *)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.
|
|
*/
|
|
|
|
if (gup_fast_permitted(start, nr_pages, write)) {
|
|
local_irq_save(flags);
|
|
gup_pgd_range(addr, end, write, pages, &nr);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
return nr;
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
unsigned long addr, len, end;
|
|
int nr = 0, ret = 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,
|
|
(void __user *)start, len)))
|
|
return 0;
|
|
|
|
if (gup_fast_permitted(start, nr_pages, write)) {
|
|
local_irq_disable();
|
|
gup_pgd_range(addr, end, write, pages, &nr);
|
|
local_irq_enable();
|
|
ret = nr;
|
|
}
|
|
|
|
if (nr < nr_pages) {
|
|
/* Try to get the remaining pages with get_user_pages */
|
|
start += nr << PAGE_SHIFT;
|
|
pages += nr;
|
|
|
|
ret = get_user_pages_unlocked(start, nr_pages - nr, pages,
|
|
write ? FOLL_WRITE : 0);
|
|
|
|
/* Have to be a bit careful with return values */
|
|
if (nr > 0) {
|
|
if (ret < 0)
|
|
ret = nr;
|
|
else
|
|
ret += nr;
|
|
}
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
#endif /* CONFIG_HAVE_GENERIC_GUP */
|