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-rw-r--r--mm/mremap.c815
1 files changed, 815 insertions, 0 deletions
diff --git a/mm/mremap.c b/mm/mremap.c
new file mode 100644
index 000000000..3334c4022
--- /dev/null
+++ b/mm/mremap.c
@@ -0,0 +1,815 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * mm/mremap.c
+ *
+ * (C) Copyright 1996 Linus Torvalds
+ *
+ * Address space accounting code <alan@lxorguk.ukuu.org.uk>
+ * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
+ */
+
+#include <linux/mm.h>
+#include <linux/hugetlb.h>
+#include <linux/shm.h>
+#include <linux/ksm.h>
+#include <linux/mman.h>
+#include <linux/swap.h>
+#include <linux/capability.h>
+#include <linux/fs.h>
+#include <linux/swapops.h>
+#include <linux/highmem.h>
+#include <linux/security.h>
+#include <linux/syscalls.h>
+#include <linux/mmu_notifier.h>
+#include <linux/uaccess.h>
+#include <linux/mm-arch-hooks.h>
+#include <linux/userfaultfd_k.h>
+
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+
+#include "internal.h"
+
+static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
+{
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+
+ pgd = pgd_offset(mm, addr);
+ if (pgd_none_or_clear_bad(pgd))
+ return NULL;
+
+ p4d = p4d_offset(pgd, addr);
+ if (p4d_none_or_clear_bad(p4d))
+ return NULL;
+
+ pud = pud_offset(p4d, addr);
+ if (pud_none_or_clear_bad(pud))
+ return NULL;
+
+ pmd = pmd_offset(pud, addr);
+ if (pmd_none(*pmd))
+ return NULL;
+
+ return pmd;
+}
+
+static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long addr)
+{
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+
+ pgd = pgd_offset(mm, addr);
+ p4d = p4d_alloc(mm, pgd, addr);
+ if (!p4d)
+ return NULL;
+ pud = pud_alloc(mm, p4d, addr);
+ if (!pud)
+ return NULL;
+
+ pmd = pmd_alloc(mm, pud, addr);
+ if (!pmd)
+ return NULL;
+
+ VM_BUG_ON(pmd_trans_huge(*pmd));
+
+ return pmd;
+}
+
+static void take_rmap_locks(struct vm_area_struct *vma)
+{
+ if (vma->vm_file)
+ i_mmap_lock_write(vma->vm_file->f_mapping);
+ if (vma->anon_vma)
+ anon_vma_lock_write(vma->anon_vma);
+}
+
+static void drop_rmap_locks(struct vm_area_struct *vma)
+{
+ if (vma->anon_vma)
+ anon_vma_unlock_write(vma->anon_vma);
+ if (vma->vm_file)
+ i_mmap_unlock_write(vma->vm_file->f_mapping);
+}
+
+static pte_t move_soft_dirty_pte(pte_t pte)
+{
+ /*
+ * Set soft dirty bit so we can notice
+ * in userspace the ptes were moved.
+ */
+#ifdef CONFIG_MEM_SOFT_DIRTY
+ if (pte_present(pte))
+ pte = pte_mksoft_dirty(pte);
+ else if (is_swap_pte(pte))
+ pte = pte_swp_mksoft_dirty(pte);
+#endif
+ return pte;
+}
+
+static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
+ unsigned long old_addr, unsigned long old_end,
+ struct vm_area_struct *new_vma, pmd_t *new_pmd,
+ unsigned long new_addr, bool need_rmap_locks)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ pte_t *old_pte, *new_pte, pte;
+ spinlock_t *old_ptl, *new_ptl;
+ bool force_flush = false;
+ unsigned long len = old_end - old_addr;
+
+ /*
+ * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
+ * locks to ensure that rmap will always observe either the old or the
+ * new ptes. This is the easiest way to avoid races with
+ * truncate_pagecache(), page migration, etc...
+ *
+ * When need_rmap_locks is false, we use other ways to avoid
+ * such races:
+ *
+ * - During exec() shift_arg_pages(), we use a specially tagged vma
+ * which rmap call sites look for using vma_is_temporary_stack().
+ *
+ * - During mremap(), new_vma is often known to be placed after vma
+ * in rmap traversal order. This ensures rmap will always observe
+ * either the old pte, or the new pte, or both (the page table locks
+ * serialize access to individual ptes, but only rmap traversal
+ * order guarantees that we won't miss both the old and new ptes).
+ */
+ if (need_rmap_locks)
+ take_rmap_locks(vma);
+
+ /*
+ * We don't have to worry about the ordering of src and dst
+ * pte locks because exclusive mmap_lock prevents deadlock.
+ */
+ old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
+ new_pte = pte_offset_map(new_pmd, new_addr);
+ new_ptl = pte_lockptr(mm, new_pmd);
+ if (new_ptl != old_ptl)
+ spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
+ flush_tlb_batched_pending(vma->vm_mm);
+ arch_enter_lazy_mmu_mode();
+
+ for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
+ new_pte++, new_addr += PAGE_SIZE) {
+ if (pte_none(*old_pte))
+ continue;
+
+ pte = ptep_get_and_clear(mm, old_addr, old_pte);
+ /*
+ * If we are remapping a valid PTE, make sure
+ * to flush TLB before we drop the PTL for the
+ * PTE.
+ *
+ * NOTE! Both old and new PTL matter: the old one
+ * for racing with page_mkclean(), the new one to
+ * make sure the physical page stays valid until
+ * the TLB entry for the old mapping has been
+ * flushed.
+ */
+ if (pte_present(pte))
+ force_flush = true;
+ pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
+ pte = move_soft_dirty_pte(pte);
+ set_pte_at(mm, new_addr, new_pte, pte);
+ }
+
+ arch_leave_lazy_mmu_mode();
+ if (force_flush)
+ flush_tlb_range(vma, old_end - len, old_end);
+ if (new_ptl != old_ptl)
+ spin_unlock(new_ptl);
+ pte_unmap(new_pte - 1);
+ pte_unmap_unlock(old_pte - 1, old_ptl);
+ if (need_rmap_locks)
+ drop_rmap_locks(vma);
+}
+
+#ifdef CONFIG_HAVE_MOVE_PMD
+static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
+ unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
+{
+ spinlock_t *old_ptl, *new_ptl;
+ struct mm_struct *mm = vma->vm_mm;
+ pmd_t pmd;
+
+ /*
+ * The destination pmd shouldn't be established, free_pgtables()
+ * should have released it.
+ *
+ * However, there's a case during execve() where we use mremap
+ * to move the initial stack, and in that case the target area
+ * may overlap the source area (always moving down).
+ *
+ * If everything is PMD-aligned, that works fine, as moving
+ * each pmd down will clear the source pmd. But if we first
+ * have a few 4kB-only pages that get moved down, and then
+ * hit the "now the rest is PMD-aligned, let's do everything
+ * one pmd at a time", we will still have the old (now empty
+ * of any 4kB pages, but still there) PMD in the page table
+ * tree.
+ *
+ * Warn on it once - because we really should try to figure
+ * out how to do this better - but then say "I won't move
+ * this pmd".
+ *
+ * One alternative might be to just unmap the target pmd at
+ * this point, and verify that it really is empty. We'll see.
+ */
+ if (WARN_ON_ONCE(!pmd_none(*new_pmd)))
+ return false;
+
+ /*
+ * We don't have to worry about the ordering of src and dst
+ * ptlocks because exclusive mmap_lock prevents deadlock.
+ */
+ old_ptl = pmd_lock(vma->vm_mm, old_pmd);
+ new_ptl = pmd_lockptr(mm, new_pmd);
+ if (new_ptl != old_ptl)
+ spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
+
+ /* Clear the pmd */
+ pmd = *old_pmd;
+ pmd_clear(old_pmd);
+
+ VM_BUG_ON(!pmd_none(*new_pmd));
+
+ /* Set the new pmd */
+ set_pmd_at(mm, new_addr, new_pmd, pmd);
+ flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
+ if (new_ptl != old_ptl)
+ spin_unlock(new_ptl);
+ spin_unlock(old_ptl);
+
+ return true;
+}
+#endif
+
+unsigned long move_page_tables(struct vm_area_struct *vma,
+ unsigned long old_addr, struct vm_area_struct *new_vma,
+ unsigned long new_addr, unsigned long len,
+ bool need_rmap_locks)
+{
+ unsigned long extent, next, old_end;
+ struct mmu_notifier_range range;
+ pmd_t *old_pmd, *new_pmd;
+
+ if (!len)
+ return 0;
+
+ old_end = old_addr + len;
+ flush_cache_range(vma, old_addr, old_end);
+
+ mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, vma->vm_mm,
+ old_addr, old_end);
+ mmu_notifier_invalidate_range_start(&range);
+
+ for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
+ cond_resched();
+ next = (old_addr + PMD_SIZE) & PMD_MASK;
+ /* even if next overflowed, extent below will be ok */
+ extent = next - old_addr;
+ if (extent > old_end - old_addr)
+ extent = old_end - old_addr;
+ next = (new_addr + PMD_SIZE) & PMD_MASK;
+ if (extent > next - new_addr)
+ extent = next - new_addr;
+ old_pmd = get_old_pmd(vma->vm_mm, old_addr);
+ if (!old_pmd)
+ continue;
+ new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
+ if (!new_pmd)
+ break;
+ if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || pmd_devmap(*old_pmd)) {
+ if (extent == HPAGE_PMD_SIZE) {
+ bool moved;
+ /* See comment in move_ptes() */
+ if (need_rmap_locks)
+ take_rmap_locks(vma);
+ moved = move_huge_pmd(vma, old_addr, new_addr,
+ old_pmd, new_pmd);
+ if (need_rmap_locks)
+ drop_rmap_locks(vma);
+ if (moved)
+ continue;
+ }
+ split_huge_pmd(vma, old_pmd, old_addr);
+ if (pmd_trans_unstable(old_pmd))
+ continue;
+ } else if (extent == PMD_SIZE) {
+#ifdef CONFIG_HAVE_MOVE_PMD
+ /*
+ * If the extent is PMD-sized, try to speed the move by
+ * moving at the PMD level if possible.
+ */
+ bool moved;
+
+ take_rmap_locks(vma);
+ moved = move_normal_pmd(vma, old_addr, new_addr,
+ old_pmd, new_pmd);
+ drop_rmap_locks(vma);
+ if (moved)
+ continue;
+#endif
+ }
+
+ if (pte_alloc(new_vma->vm_mm, new_pmd))
+ break;
+ move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
+ new_pmd, new_addr, need_rmap_locks);
+ }
+
+ mmu_notifier_invalidate_range_end(&range);
+
+ return len + old_addr - old_end; /* how much done */
+}
+
+static unsigned long move_vma(struct vm_area_struct *vma,
+ unsigned long old_addr, unsigned long old_len,
+ unsigned long new_len, unsigned long new_addr,
+ bool *locked, unsigned long flags,
+ struct vm_userfaultfd_ctx *uf, struct list_head *uf_unmap)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ struct vm_area_struct *new_vma;
+ unsigned long vm_flags = vma->vm_flags;
+ unsigned long new_pgoff;
+ unsigned long moved_len;
+ unsigned long excess = 0;
+ unsigned long hiwater_vm;
+ int split = 0;
+ int err;
+ bool need_rmap_locks;
+
+ /*
+ * We'd prefer to avoid failure later on in do_munmap:
+ * which may split one vma into three before unmapping.
+ */
+ if (mm->map_count >= sysctl_max_map_count - 3)
+ return -ENOMEM;
+
+ /*
+ * Advise KSM to break any KSM pages in the area to be moved:
+ * it would be confusing if they were to turn up at the new
+ * location, where they happen to coincide with different KSM
+ * pages recently unmapped. But leave vma->vm_flags as it was,
+ * so KSM can come around to merge on vma and new_vma afterwards.
+ */
+ err = ksm_madvise(vma, old_addr, old_addr + old_len,
+ MADV_UNMERGEABLE, &vm_flags);
+ if (err)
+ return err;
+
+ new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
+ new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
+ &need_rmap_locks);
+ if (!new_vma)
+ return -ENOMEM;
+
+ moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
+ need_rmap_locks);
+ if (moved_len < old_len) {
+ err = -ENOMEM;
+ } else if (vma->vm_ops && vma->vm_ops->mremap) {
+ err = vma->vm_ops->mremap(new_vma);
+ }
+
+ if (unlikely(err)) {
+ /*
+ * On error, move entries back from new area to old,
+ * which will succeed since page tables still there,
+ * and then proceed to unmap new area instead of old.
+ */
+ move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
+ true);
+ vma = new_vma;
+ old_len = new_len;
+ old_addr = new_addr;
+ new_addr = err;
+ } else {
+ mremap_userfaultfd_prep(new_vma, uf);
+ arch_remap(mm, old_addr, old_addr + old_len,
+ new_addr, new_addr + new_len);
+ }
+
+ /* Conceal VM_ACCOUNT so old reservation is not undone */
+ if (vm_flags & VM_ACCOUNT) {
+ vma->vm_flags &= ~VM_ACCOUNT;
+ excess = vma->vm_end - vma->vm_start - old_len;
+ if (old_addr > vma->vm_start &&
+ old_addr + old_len < vma->vm_end)
+ split = 1;
+ }
+
+ /*
+ * If we failed to move page tables we still do total_vm increment
+ * since do_munmap() will decrement it by old_len == new_len.
+ *
+ * Since total_vm is about to be raised artificially high for a
+ * moment, we need to restore high watermark afterwards: if stats
+ * are taken meanwhile, total_vm and hiwater_vm appear too high.
+ * If this were a serious issue, we'd add a flag to do_munmap().
+ */
+ hiwater_vm = mm->hiwater_vm;
+ vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
+
+ /* Tell pfnmap has moved from this vma */
+ if (unlikely(vma->vm_flags & VM_PFNMAP))
+ untrack_pfn_moved(vma);
+
+ if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) {
+ if (vm_flags & VM_ACCOUNT) {
+ /* Always put back VM_ACCOUNT since we won't unmap */
+ vma->vm_flags |= VM_ACCOUNT;
+
+ vm_acct_memory(new_len >> PAGE_SHIFT);
+ }
+
+ /*
+ * VMAs can actually be merged back together in copy_vma
+ * calling merge_vma. This can happen with anonymous vmas
+ * which have not yet been faulted, so if we were to consider
+ * this VMA split we'll end up adding VM_ACCOUNT on the
+ * next VMA, which is completely unrelated if this VMA
+ * was re-merged.
+ */
+ if (split && new_vma == vma)
+ split = 0;
+
+ /* We always clear VM_LOCKED[ONFAULT] on the old vma */
+ vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
+
+ /* Because we won't unmap we don't need to touch locked_vm */
+ goto out;
+ }
+
+ if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
+ /* OOM: unable to split vma, just get accounts right */
+ vm_unacct_memory(excess >> PAGE_SHIFT);
+ excess = 0;
+ }
+
+ if (vm_flags & VM_LOCKED) {
+ mm->locked_vm += new_len >> PAGE_SHIFT;
+ *locked = true;
+ }
+out:
+ mm->hiwater_vm = hiwater_vm;
+
+ /* Restore VM_ACCOUNT if one or two pieces of vma left */
+ if (excess) {
+ vma->vm_flags |= VM_ACCOUNT;
+ if (split)
+ vma->vm_next->vm_flags |= VM_ACCOUNT;
+ }
+
+ return new_addr;
+}
+
+static struct vm_area_struct *vma_to_resize(unsigned long addr,
+ unsigned long old_len, unsigned long new_len, unsigned long flags,
+ unsigned long *p)
+{
+ struct mm_struct *mm = current->mm;
+ struct vm_area_struct *vma = find_vma(mm, addr);
+ unsigned long pgoff;
+
+ if (!vma || vma->vm_start > addr)
+ return ERR_PTR(-EFAULT);
+
+ /*
+ * !old_len is a special case where an attempt is made to 'duplicate'
+ * a mapping. This makes no sense for private mappings as it will
+ * instead create a fresh/new mapping unrelated to the original. This
+ * is contrary to the basic idea of mremap which creates new mappings
+ * based on the original. There are no known use cases for this
+ * behavior. As a result, fail such attempts.
+ */
+ if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
+ pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid);
+ return ERR_PTR(-EINVAL);
+ }
+
+ if (flags & MREMAP_DONTUNMAP && (!vma_is_anonymous(vma) ||
+ vma->vm_flags & VM_SHARED))
+ return ERR_PTR(-EINVAL);
+
+ if (is_vm_hugetlb_page(vma))
+ return ERR_PTR(-EINVAL);
+
+ /* We can't remap across vm area boundaries */
+ if (old_len > vma->vm_end - addr)
+ return ERR_PTR(-EFAULT);
+
+ if (new_len == old_len)
+ return vma;
+
+ /* Need to be careful about a growing mapping */
+ pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
+ pgoff += vma->vm_pgoff;
+ if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
+ return ERR_PTR(-EINVAL);
+
+ if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
+ return ERR_PTR(-EFAULT);
+
+ if (vma->vm_flags & VM_LOCKED) {
+ unsigned long locked, lock_limit;
+ locked = mm->locked_vm << PAGE_SHIFT;
+ lock_limit = rlimit(RLIMIT_MEMLOCK);
+ locked += new_len - old_len;
+ if (locked > lock_limit && !capable(CAP_IPC_LOCK))
+ return ERR_PTR(-EAGAIN);
+ }
+
+ if (!may_expand_vm(mm, vma->vm_flags,
+ (new_len - old_len) >> PAGE_SHIFT))
+ return ERR_PTR(-ENOMEM);
+
+ if (vma->vm_flags & VM_ACCOUNT) {
+ unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
+ if (security_vm_enough_memory_mm(mm, charged))
+ return ERR_PTR(-ENOMEM);
+ *p = charged;
+ }
+
+ return vma;
+}
+
+static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
+ unsigned long new_addr, unsigned long new_len, bool *locked,
+ unsigned long flags, struct vm_userfaultfd_ctx *uf,
+ struct list_head *uf_unmap_early,
+ struct list_head *uf_unmap)
+{
+ struct mm_struct *mm = current->mm;
+ struct vm_area_struct *vma;
+ unsigned long ret = -EINVAL;
+ unsigned long charged = 0;
+ unsigned long map_flags = 0;
+
+ if (offset_in_page(new_addr))
+ goto out;
+
+ if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
+ goto out;
+
+ /* Ensure the old/new locations do not overlap */
+ if (addr + old_len > new_addr && new_addr + new_len > addr)
+ goto out;
+
+ /*
+ * move_vma() need us to stay 4 maps below the threshold, otherwise
+ * it will bail out at the very beginning.
+ * That is a problem if we have already unmaped the regions here
+ * (new_addr, and old_addr), because userspace will not know the
+ * state of the vma's after it gets -ENOMEM.
+ * So, to avoid such scenario we can pre-compute if the whole
+ * operation has high chances to success map-wise.
+ * Worst-scenario case is when both vma's (new_addr and old_addr) get
+ * split in 3 before unmaping it.
+ * That means 2 more maps (1 for each) to the ones we already hold.
+ * Check whether current map count plus 2 still leads us to 4 maps below
+ * the threshold, otherwise return -ENOMEM here to be more safe.
+ */
+ if ((mm->map_count + 2) >= sysctl_max_map_count - 3)
+ return -ENOMEM;
+
+ if (flags & MREMAP_FIXED) {
+ ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
+ if (ret)
+ goto out;
+ }
+
+ if (old_len >= new_len) {
+ ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
+ if (ret && old_len != new_len)
+ goto out;
+ old_len = new_len;
+ }
+
+ vma = vma_to_resize(addr, old_len, new_len, flags, &charged);
+ if (IS_ERR(vma)) {
+ ret = PTR_ERR(vma);
+ goto out;
+ }
+
+ /* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */
+ if (flags & MREMAP_DONTUNMAP &&
+ !may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ if (flags & MREMAP_FIXED)
+ map_flags |= MAP_FIXED;
+
+ if (vma->vm_flags & VM_MAYSHARE)
+ map_flags |= MAP_SHARED;
+
+ ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
+ ((addr - vma->vm_start) >> PAGE_SHIFT),
+ map_flags);
+ if (IS_ERR_VALUE(ret))
+ goto out1;
+
+ /* We got a new mapping */
+ if (!(flags & MREMAP_FIXED))
+ new_addr = ret;
+
+ ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, flags, uf,
+ uf_unmap);
+
+ if (!(offset_in_page(ret)))
+ goto out;
+
+out1:
+ vm_unacct_memory(charged);
+
+out:
+ return ret;
+}
+
+static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
+{
+ unsigned long end = vma->vm_end + delta;
+ if (end < vma->vm_end) /* overflow */
+ return 0;
+ if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
+ return 0;
+ if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
+ 0, MAP_FIXED) & ~PAGE_MASK)
+ return 0;
+ return 1;
+}
+
+/*
+ * Expand (or shrink) an existing mapping, potentially moving it at the
+ * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
+ *
+ * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
+ * This option implies MREMAP_MAYMOVE.
+ */
+SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
+ unsigned long, new_len, unsigned long, flags,
+ unsigned long, new_addr)
+{
+ struct mm_struct *mm = current->mm;
+ struct vm_area_struct *vma;
+ unsigned long ret = -EINVAL;
+ unsigned long charged = 0;
+ bool locked = false;
+ bool downgraded = false;
+ struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
+ LIST_HEAD(uf_unmap_early);
+ LIST_HEAD(uf_unmap);
+
+ /*
+ * There is a deliberate asymmetry here: we strip the pointer tag
+ * from the old address but leave the new address alone. This is
+ * for consistency with mmap(), where we prevent the creation of
+ * aliasing mappings in userspace by leaving the tag bits of the
+ * mapping address intact. A non-zero tag will cause the subsequent
+ * range checks to reject the address as invalid.
+ *
+ * See Documentation/arm64/tagged-address-abi.rst for more information.
+ */
+ addr = untagged_addr(addr);
+
+ if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP))
+ return ret;
+
+ if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
+ return ret;
+
+ /*
+ * MREMAP_DONTUNMAP is always a move and it does not allow resizing
+ * in the process.
+ */
+ if (flags & MREMAP_DONTUNMAP &&
+ (!(flags & MREMAP_MAYMOVE) || old_len != new_len))
+ return ret;
+
+
+ if (offset_in_page(addr))
+ return ret;
+
+ old_len = PAGE_ALIGN(old_len);
+ new_len = PAGE_ALIGN(new_len);
+
+ /*
+ * We allow a zero old-len as a special case
+ * for DOS-emu "duplicate shm area" thing. But
+ * a zero new-len is nonsensical.
+ */
+ if (!new_len)
+ return ret;
+
+ if (mmap_write_lock_killable(current->mm))
+ return -EINTR;
+
+ if (flags & (MREMAP_FIXED | MREMAP_DONTUNMAP)) {
+ ret = mremap_to(addr, old_len, new_addr, new_len,
+ &locked, flags, &uf, &uf_unmap_early,
+ &uf_unmap);
+ goto out;
+ }
+
+ /*
+ * Always allow a shrinking remap: that just unmaps
+ * the unnecessary pages..
+ * __do_munmap does all the needed commit accounting, and
+ * downgrades mmap_lock to read if so directed.
+ */
+ if (old_len >= new_len) {
+ int retval;
+
+ retval = __do_munmap(mm, addr+new_len, old_len - new_len,
+ &uf_unmap, true);
+ if (retval < 0 && old_len != new_len) {
+ ret = retval;
+ goto out;
+ /* Returning 1 indicates mmap_lock is downgraded to read. */
+ } else if (retval == 1)
+ downgraded = true;
+ ret = addr;
+ goto out;
+ }
+
+ /*
+ * Ok, we need to grow..
+ */
+ vma = vma_to_resize(addr, old_len, new_len, flags, &charged);
+ if (IS_ERR(vma)) {
+ ret = PTR_ERR(vma);
+ goto out;
+ }
+
+ /* old_len exactly to the end of the area..
+ */
+ if (old_len == vma->vm_end - addr) {
+ /* can we just expand the current mapping? */
+ if (vma_expandable(vma, new_len - old_len)) {
+ int pages = (new_len - old_len) >> PAGE_SHIFT;
+
+ if (vma_adjust(vma, vma->vm_start, addr + new_len,
+ vma->vm_pgoff, NULL)) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ vm_stat_account(mm, vma->vm_flags, pages);
+ if (vma->vm_flags & VM_LOCKED) {
+ mm->locked_vm += pages;
+ locked = true;
+ new_addr = addr;
+ }
+ ret = addr;
+ goto out;
+ }
+ }
+
+ /*
+ * We weren't able to just expand or shrink the area,
+ * we need to create a new one and move it..
+ */
+ ret = -ENOMEM;
+ if (flags & MREMAP_MAYMOVE) {
+ unsigned long map_flags = 0;
+ if (vma->vm_flags & VM_MAYSHARE)
+ map_flags |= MAP_SHARED;
+
+ new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
+ vma->vm_pgoff +
+ ((addr - vma->vm_start) >> PAGE_SHIFT),
+ map_flags);
+ if (IS_ERR_VALUE(new_addr)) {
+ ret = new_addr;
+ goto out;
+ }
+
+ ret = move_vma(vma, addr, old_len, new_len, new_addr,
+ &locked, flags, &uf, &uf_unmap);
+ }
+out:
+ if (offset_in_page(ret)) {
+ vm_unacct_memory(charged);
+ locked = false;
+ }
+ if (downgraded)
+ mmap_read_unlock(current->mm);
+ else
+ mmap_write_unlock(current->mm);
+ if (locked && new_len > old_len)
+ mm_populate(new_addr + old_len, new_len - old_len);
+ userfaultfd_unmap_complete(mm, &uf_unmap_early);
+ mremap_userfaultfd_complete(&uf, addr, ret, old_len);
+ userfaultfd_unmap_complete(mm, &uf_unmap);
+ return ret;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-18 20:08:11 +0000