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-rw-r--r--mm/mremap.c433
1 files changed, 433 insertions, 0 deletions
diff --git a/mm/mremap.c b/mm/mremap.c
new file mode 100644
index 0000000..4207055
--- /dev/null
+++ b/mm/mremap.c
@@ -0,0 +1,433 @@
+/*
+ * mm/mremap.c
+ *
+ * (C) Copyright 1996 Linus Torvalds
+ *
+ * Address space accounting code <alan@redhat.com>
+ * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
+ */
+
+#include <linux/mm.h>
+#include <linux/hugetlb.h>
+#include <linux/slab.h>
+#include <linux/shm.h>
+#include <linux/mman.h>
+#include <linux/swap.h>
+#include <linux/capability.h>
+#include <linux/fs.h>
+#include <linux/highmem.h>
+#include <linux/security.h>
+#include <linux/syscalls.h>
+#include <linux/mmu_notifier.h>
+
+#include <asm/uaccess.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;
+ pud_t *pud;
+ pmd_t *pmd;
+
+ pgd = pgd_offset(mm, addr);
+ if (pgd_none_or_clear_bad(pgd))
+ return NULL;
+
+ pud = pud_offset(pgd, addr);
+ if (pud_none_or_clear_bad(pud))
+ return NULL;
+
+ pmd = pmd_offset(pud, addr);
+ if (pmd_none_or_clear_bad(pmd))
+ return NULL;
+
+ return pmd;
+}
+
+static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
+{
+ pgd_t *pgd;
+ pud_t *pud;
+ pmd_t *pmd;
+
+ pgd = pgd_offset(mm, addr);
+ pud = pud_alloc(mm, pgd, addr);
+ if (!pud)
+ return NULL;
+
+ pmd = pmd_alloc(mm, pud, addr);
+ if (!pmd)
+ return NULL;
+
+ if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
+ return NULL;
+
+ return pmd;
+}
+
+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)
+{
+ struct address_space *mapping = NULL;
+ struct mm_struct *mm = vma->vm_mm;
+ pte_t *old_pte, *new_pte, pte;
+ spinlock_t *old_ptl, *new_ptl;
+ unsigned long old_start;
+
+ old_start = old_addr;
+ mmu_notifier_invalidate_range_start(vma->vm_mm,
+ old_start, old_end);
+ if (vma->vm_file) {
+ /*
+ * Subtle point from Rajesh Venkatasubramanian: before
+ * moving file-based ptes, we must lock vmtruncate out,
+ * since it might clean the dst vma before the src vma,
+ * and we propagate stale pages into the dst afterward.
+ */
+ mapping = vma->vm_file->f_mapping;
+ spin_lock(&mapping->i_mmap_lock);
+ if (new_vma->vm_truncate_count &&
+ new_vma->vm_truncate_count != vma->vm_truncate_count)
+ new_vma->vm_truncate_count = 0;
+ }
+
+ /*
+ * We don't have to worry about the ordering of src and dst
+ * pte locks because exclusive mmap_sem prevents deadlock.
+ */
+ old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
+ new_pte = pte_offset_map_nested(new_pmd, new_addr);
+ new_ptl = pte_lockptr(mm, new_pmd);
+ if (new_ptl != old_ptl)
+ spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
+ 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_clear_flush(vma, old_addr, old_pte);
+ pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
+ set_pte_at(mm, new_addr, new_pte, pte);
+ }
+
+ arch_leave_lazy_mmu_mode();
+ if (new_ptl != old_ptl)
+ spin_unlock(new_ptl);
+ pte_unmap_nested(new_pte - 1);
+ pte_unmap_unlock(old_pte - 1, old_ptl);
+ if (mapping)
+ spin_unlock(&mapping->i_mmap_lock);
+ mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end);
+}
+
+#define LATENCY_LIMIT (64 * PAGE_SIZE)
+
+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)
+{
+ unsigned long extent, next, old_end;
+ pmd_t *old_pmd, *new_pmd;
+
+ old_end = old_addr + len;
+ flush_cache_range(vma, old_addr, old_end);
+
+ for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
+ cond_resched();
+ next = (old_addr + PMD_SIZE) & PMD_MASK;
+ if (next - 1 > old_end)
+ next = old_end;
+ extent = next - old_addr;
+ old_pmd = get_old_pmd(vma->vm_mm, old_addr);
+ if (!old_pmd)
+ continue;
+ new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
+ if (!new_pmd)
+ break;
+ next = (new_addr + PMD_SIZE) & PMD_MASK;
+ if (extent > next - new_addr)
+ extent = next - new_addr;
+ if (extent > LATENCY_LIMIT)
+ extent = LATENCY_LIMIT;
+ move_ptes(vma, old_pmd, old_addr, old_addr + extent,
+ new_vma, new_pmd, new_addr);
+ }
+
+ 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)
+{
+ 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;
+
+ /*
+ * 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;
+
+ new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
+ new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
+ if (!new_vma)
+ return -ENOMEM;
+
+ moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
+ if (moved_len < old_len) {
+ /*
+ * 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);
+ vma = new_vma;
+ old_len = new_len;
+ old_addr = new_addr;
+ new_addr = -ENOMEM;
+ }
+
+ /* 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;
+ mm->total_vm += new_len >> PAGE_SHIFT;
+ vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
+
+ if (do_munmap(mm, old_addr, old_len) < 0) {
+ /* OOM: unable to split vma, just get accounts right */
+ vm_unacct_memory(excess >> PAGE_SHIFT);
+ excess = 0;
+ }
+ 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;
+ }
+
+ if (vm_flags & VM_LOCKED) {
+ mm->locked_vm += new_len >> PAGE_SHIFT;
+ if (new_len > old_len)
+ mlock_vma_pages_range(new_vma, new_addr + old_len,
+ new_addr + new_len);
+ }
+
+ return new_addr;
+}
+
+/*
+ * 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.
+ */
+unsigned long do_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;
+
+ if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
+ goto out;
+
+ if (addr & ~PAGE_MASK)
+ goto out;
+
+ 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)
+ goto out;
+
+ /* new_addr is only valid if MREMAP_FIXED is specified */
+ if (flags & MREMAP_FIXED) {
+ if (new_addr & ~PAGE_MASK)
+ goto out;
+ if (!(flags & MREMAP_MAYMOVE))
+ goto out;
+
+ if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
+ goto out;
+
+ /* Check if the location we're moving into overlaps the
+ * old location at all, and fail if it does.
+ */
+ if ((new_addr <= addr) && (new_addr+new_len) > addr)
+ goto out;
+
+ if ((addr <= new_addr) && (addr+old_len) > new_addr)
+ goto out;
+
+ ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
+ if (ret)
+ goto out;
+
+ ret = do_munmap(mm, new_addr, new_len);
+ if (ret)
+ goto out;
+ }
+
+ /*
+ * Always allow a shrinking remap: that just unmaps
+ * the unnecessary pages..
+ * do_munmap does all the needed commit accounting
+ */
+ if (old_len >= new_len) {
+ ret = do_munmap(mm, addr+new_len, old_len - new_len);
+ if (ret && old_len != new_len)
+ goto out;
+ ret = addr;
+ if (!(flags & MREMAP_FIXED) || (new_addr == addr))
+ goto out;
+ old_len = new_len;
+ }
+
+ /*
+ * Ok, we need to grow.. or relocate.
+ */
+ ret = -EFAULT;
+ vma = find_vma(mm, addr);
+ if (!vma || vma->vm_start > addr)
+ goto out;
+ if (is_vm_hugetlb_page(vma)) {
+ ret = -EINVAL;
+ goto out;
+ }
+ /* We can't remap across vm area boundaries */
+ if (old_len > vma->vm_end - addr)
+ goto out;
+ if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
+ if (new_len > old_len)
+ goto out;
+ }
+ if (vma->vm_flags & VM_LOCKED) {
+ unsigned long locked, lock_limit;
+ locked = mm->locked_vm << PAGE_SHIFT;
+ lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
+ locked += new_len - old_len;
+ ret = -EAGAIN;
+ if (locked > lock_limit && !capable(CAP_IPC_LOCK))
+ goto out;
+ }
+ if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ if (vma->vm_flags & VM_ACCOUNT) {
+ charged = (new_len - old_len) >> PAGE_SHIFT;
+ if (security_vm_enough_memory(charged))
+ goto out_nc;
+ }
+
+ /* old_len exactly to the end of the area..
+ * And we're not relocating the area.
+ */
+ if (old_len == vma->vm_end - addr &&
+ !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
+ (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
+ unsigned long max_addr = TASK_SIZE;
+ if (vma->vm_next)
+ max_addr = vma->vm_next->vm_start;
+ /* can we just expand the current mapping? */
+ if (max_addr - addr >= new_len) {
+ int pages = (new_len - old_len) >> PAGE_SHIFT;
+
+ vma_adjust(vma, vma->vm_start,
+ addr + new_len, vma->vm_pgoff, NULL);
+
+ mm->total_vm += pages;
+ vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
+ if (vma->vm_flags & VM_LOCKED) {
+ mm->locked_vm += pages;
+ mlock_vma_pages_range(vma, addr + old_len,
+ addr + new_len);
+ }
+ 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) {
+ if (!(flags & MREMAP_FIXED)) {
+ 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, map_flags);
+ if (new_addr & ~PAGE_MASK) {
+ ret = new_addr;
+ goto out;
+ }
+
+ ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
+ if (ret)
+ goto out;
+ }
+ ret = move_vma(vma, addr, old_len, new_len, new_addr);
+ }
+out:
+ if (ret & ~PAGE_MASK)
+ vm_unacct_memory(charged);
+out_nc:
+ return ret;
+}
+
+SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
+ unsigned long, new_len, unsigned long, flags,
+ unsigned long, new_addr)
+{
+ unsigned long ret;
+
+ down_write(&current->mm->mmap_sem);
+ ret = do_mremap(addr, old_len, new_len, flags, new_addr);
+ up_write(&current->mm->mmap_sem);
+ return ret;
+}
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