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userfaultfd: non-cooperative: add event for memory unmaps

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When a non-cooperative userfaultfd monitor copies pages in the
background, it may encounter regions that were already unmapped.
Addition of UFFD_EVENT_UNMAP allows the uffd monitor to track precisely
changes in the virtual memory layout.

Since there might be different uffd contexts for the affected VMAs, we
first should create a temporary representation for the unmap event for
each uffd context and then notify them one by one to the appropriate
userfault file descriptors.

The event notification occurs after the mmap_sem has been released.

[[email protected]: fix nommu build]
  Link: http://lkml.kernel.org/r/[email protected]
[[email protected]: fix nommu build]
  Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport <[email protected]>
Signed-off-by: Michal Hocko <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Acked-by: Hillf Danton <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: "Dr. David Alan Gilbert" <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Mike Rapoport 2017-02-24 14:58:22 -08:00 • committed by Linus Torvalds
commit 897ab3e0c4
15 changed files with 160 additions and 45 deletions
Download patch file Download diff file Expand all files Collapse all files

46
mm/mmap.c
View file

@ -176,7 +176,7 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
return next;
}
static int do_brk(unsigned long addr, unsigned long len);
static int do_brk(unsigned long addr, unsigned long len, struct list_head *uf);
SYSCALL_DEFINE1(brk, unsigned long, brk)
{
@ -185,6 +185,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
struct mm_struct *mm = current->mm;
unsigned long min_brk;
bool populate;
LIST_HEAD(uf);
if (down_write_killable(&mm->mmap_sem))
return -EINTR;
@ -222,7 +223,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
/* Always allow shrinking brk. */
if (brk <= mm->brk) {
if (!do_munmap(mm, newbrk, oldbrk-newbrk))
if (!do_munmap(mm, newbrk, oldbrk-newbrk, &uf))
goto set_brk;
goto out;
}
@ -232,13 +233,14 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
goto out;
/* Ok, looks good - let it rip. */
if (do_brk(oldbrk, newbrk-oldbrk) < 0)
if (do_brk(oldbrk, newbrk-oldbrk, &uf) < 0)
goto out;
set_brk:
mm->brk = brk;
populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
up_write(&mm->mmap_sem);
userfaultfd_unmap_complete(mm, &uf);
if (populate)
mm_populate(oldbrk, newbrk - oldbrk);
return brk;
@ -1304,7 +1306,8 @@ static inline int mlock_future_check(struct mm_struct *mm,
unsigned long do_mmap(struct file *file, unsigned long addr,
unsigned long len, unsigned long prot,
unsigned long flags, vm_flags_t vm_flags,
unsigned long pgoff, unsigned long *populate)
unsigned long pgoff, unsigned long *populate,
struct list_head *uf)
{
struct mm_struct *mm = current->mm;
int pkey = 0;
@ -1447,7 +1450,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
vm_flags |= VM_NORESERVE;
}
addr = mmap_region(file, addr, len, vm_flags, pgoff);
addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
if (!IS_ERR_VALUE(addr) &&
((vm_flags & VM_LOCKED) ||
(flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
@ -1583,7 +1586,8 @@ static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
}
unsigned long mmap_region(struct file *file, unsigned long addr,
unsigned long len, vm_flags_t vm_flags, unsigned long pgoff)
unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
struct list_head *uf)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma, *prev;
@ -1609,7 +1613,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
/* Clear old maps */
while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
&rb_parent)) {
if (do_munmap(mm, addr, len))
if (do_munmap(mm, addr, len, uf))
return -ENOMEM;
}
@ -2579,7 +2583,8 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
* work. This now handles partial unmappings.
* Jeremy Fitzhardinge <jeremy@goop.org>
*/
int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
struct list_head *uf)
{
unsigned long end;
struct vm_area_struct *vma, *prev, *last;
@ -2603,6 +2608,13 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
if (vma->vm_start >= end)
return 0;
if (uf) {
int error = userfaultfd_unmap_prep(vma, start, end, uf);
if (error)
return error;
}
/*
* If we need to split any vma, do it now to save pain later.
*
@ -2668,12 +2680,14 @@ int vm_munmap(unsigned long start, size_t len)
{
int ret;
struct mm_struct *mm = current->mm;
LIST_HEAD(uf);
if (down_write_killable(&mm->mmap_sem))
return -EINTR;
ret = do_munmap(mm, start, len);
ret = do_munmap(mm, start, len, &uf);
up_write(&mm->mmap_sem);
userfaultfd_unmap_complete(mm, &uf);
return ret;
}
EXPORT_SYMBOL(vm_munmap);
@ -2773,7 +2787,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
file = get_file(vma->vm_file);
ret = do_mmap_pgoff(vma->vm_file, start, size,
prot, flags, pgoff, &populate);
prot, flags, pgoff, &populate, NULL);
fput(file);
out:
up_write(&mm->mmap_sem);
@ -2799,7 +2813,7 @@ static inline void verify_mm_writelocked(struct mm_struct *mm)
* anonymous maps. eventually we may be able to do some
* brk-specific accounting here.
*/
static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags, struct list_head *uf)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma, *prev;
@ -2838,7 +2852,7 @@ static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long
*/
while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
&rb_parent)) {
if (do_munmap(mm, addr, len))
if (do_munmap(mm, addr, len, uf))
return -ENOMEM;
}
@ -2885,9 +2899,9 @@ out:
return 0;
}
static int do_brk(unsigned long addr, unsigned long len)
static int do_brk(unsigned long addr, unsigned long len, struct list_head *uf)
{
return do_brk_flags(addr, len, 0);
return do_brk_flags(addr, len, 0, uf);
}
int vm_brk_flags(unsigned long addr, unsigned long len, unsigned long flags)
@ -2895,13 +2909,15 @@ int vm_brk_flags(unsigned long addr, unsigned long len, unsigned long flags)
struct mm_struct *mm = current->mm;
int ret;
bool populate;
LIST_HEAD(uf);
if (down_write_killable(&mm->mmap_sem))
return -EINTR;
ret = do_brk_flags(addr, len, flags);
ret = do_brk_flags(addr, len, flags, &uf);
populate = ((mm->def_flags & VM_LOCKED) != 0);
up_write(&mm->mmap_sem);
userfaultfd_unmap_complete(mm, &uf);
if (populate && !ret)
mm_populate(addr, len);
return ret;