[RFC,v2,0/7] Make core VMA operations internal and testable

Message

Lorenzo Stoakes June 28, 2024, 2:35 p.m. UTC

There are a number of "core" VMA manipulation functions implemented in
mm/mmap.c, notably those concerning VMA merging, splitting, modifying,
expanding and shrinking, which logically don't belong there.

More importantly this functionality represents an internal implementation
detail of memory management and should not be exposed outside of mm/
itself.

This patch series isolates core VMA manipulation functionality into its own
file, mm/vma.c, and provides an API to the rest of the mm code in mm/vma.h.

Importantly, it also carefully implements mm/vma_internal.h, which
specifies which headers need to be imported by vma.c, leading to the very
useful property that vma.c depends only on mm/vma.h and mm/vma_internal.h.

This is useful, because we can then re-implement vma_internal.h in
userland, stubbing out and adding shims for kernel mechanisms as required,
and then can directly and very easily unit test internal VMA functionality.

This patch series takes advantage of existing shim logic and full userland
maple tree support contained in tools/testing/radix-tree/ and
tools/include/linux/, separating out shared components of the radix tree
implementation to provide this testing.

Kernel functionality is stubbed and shimmed as needed in tools/testing/vma/
which contains a fully functional userland vma_internal.h file and which
imports mm/vma.c and mm/vma.h to be directly tested from userland.

A simple, skeleton testing implementation is provided in
tools/testing/vma/vma.c as a proof-of-concept, asserting that simple VMA
merge, modify (testing split), expand and shrink functionality work
correctly.

v2:
* Reword commit messages.
* Replace vma_expand() / vma_shrink() wrappers with relocate_vma().
* Make move_page_tables() internal too.
* Have internal.h import vma.h.
* Use header guards to more cleanly implement userland testing code.
* Rename main.c to vma.c.
* Update mm/vma_internal.h to have fewer superfluous comments.
* Rework testing logic so we count test failures, and output test results.
* Correct some SPDX license prefixes.
* Make VM_xxx_ON() debug asserts forward to xxx_ON() macros.
* Update VMA tests to correctly free memory, and re-enable ASAN leak
  detection.

v1:
https://lore.kernel.org/all/[e-mail]/

Lorenzo Stoakes (7):
  userfaultfd: move core VMA manipulation logic to mm/userfaultfd.c
  mm: move vma_modify() and helpers to internal header
  mm: move vma_shrink(), vma_expand() to internal header
  mm: move internal core VMA manipulation functions to own file
  MAINTAINERS: Add entry for new VMA files
  tools: separate out shared radix-tree components
  tools: add skeleton code for userland testing of VMA logic

 MAINTAINERS                                   |   14 +
 fs/exec.c                                     |   68 +-
 fs/userfaultfd.c                              |  160 +-
 include/linux/atomic.h                        |    2 +-
 include/linux/mm.h                            |  112 +-
 include/linux/mmzone.h                        |    3 +-
 include/linux/userfaultfd_k.h                 |   19 +
 mm/Makefile                                   |    2 +-
 mm/internal.h                                 |  167 +-
 mm/mmap.c                                     | 2070 ++---------------
 mm/mmu_notifier.c                             |    2 +
 mm/userfaultfd.c                              |  168 ++
 mm/vma.c                                      | 1766 ++++++++++++++
 mm/vma.h                                      |  362 +++
 mm/vma_internal.h                             |   52 +
 tools/testing/radix-tree/Makefile             |   68 +-
 tools/testing/radix-tree/maple.c              |   14 +-
 tools/testing/radix-tree/xarray.c             |    9 +-
 tools/testing/shared/autoconf.h               |    2 +
 tools/testing/{radix-tree => shared}/bitmap.c |    0
 tools/testing/{radix-tree => shared}/linux.c  |    0
 .../{radix-tree => shared}/linux/bug.h        |    0
 .../{radix-tree => shared}/linux/cpu.h        |    0
 .../{radix-tree => shared}/linux/idr.h        |    0
 .../{radix-tree => shared}/linux/init.h       |    0
 .../{radix-tree => shared}/linux/kconfig.h    |    0
 .../{radix-tree => shared}/linux/kernel.h     |    0
 .../{radix-tree => shared}/linux/kmemleak.h   |    0
 .../{radix-tree => shared}/linux/local_lock.h |    0
 .../{radix-tree => shared}/linux/lockdep.h    |    0
 .../{radix-tree => shared}/linux/maple_tree.h |    0
 .../{radix-tree => shared}/linux/percpu.h     |    0
 .../{radix-tree => shared}/linux/preempt.h    |    0
 .../{radix-tree => shared}/linux/radix-tree.h |    0
 .../{radix-tree => shared}/linux/rcupdate.h   |    0
 .../{radix-tree => shared}/linux/xarray.h     |    0
 tools/testing/shared/maple-shared.h           |    9 +
 tools/testing/shared/maple-shim.c             |    7 +
 tools/testing/shared/shared.h                 |   34 +
 tools/testing/shared/shared.mk                |   68 +
 .../testing/shared/trace/events/maple_tree.h  |    5 +
 tools/testing/shared/xarray-shared.c          |    5 +
 tools/testing/shared/xarray-shared.h          |    4 +
 tools/testing/vma/.gitignore                  |    6 +
 tools/testing/vma/Makefile                    |   15 +
 tools/testing/vma/errors.txt                  |    0
 tools/testing/vma/generated/autoconf.h        |    2 +
 tools/testing/vma/linux/atomic.h              |   12 +
 tools/testing/vma/linux/mmzone.h              |   38 +
 tools/testing/vma/vma.c                       |  207 ++
 tools/testing/vma/vma_internal.h              |  882 +++++++
 51 files changed, 3910 insertions(+), 2444 deletions(-)
 create mode 100644 mm/vma.c
 create mode 100644 mm/vma.h
 create mode 100644 mm/vma_internal.h
 create mode 100644 tools/testing/shared/autoconf.h
 rename tools/testing/{radix-tree => shared}/bitmap.c (100%)
 rename tools/testing/{radix-tree => shared}/linux.c (100%)
 rename tools/testing/{radix-tree => shared}/linux/bug.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/cpu.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/idr.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/init.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/kconfig.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/kernel.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/kmemleak.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/local_lock.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/lockdep.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/maple_tree.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/percpu.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/preempt.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/radix-tree.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/rcupdate.h (100%)
 rename tools/testing/{radix-tree => shared}/linux/xarray.h (100%)
 create mode 100644 tools/testing/shared/maple-shared.h
 create mode 100644 tools/testing/shared/maple-shim.c
 create mode 100644 tools/testing/shared/shared.h
 create mode 100644 tools/testing/shared/shared.mk
 create mode 100644 tools/testing/shared/trace/events/maple_tree.h
 create mode 100644 tools/testing/shared/xarray-shared.c
 create mode 100644 tools/testing/shared/xarray-shared.h
 create mode 100644 tools/testing/vma/.gitignore
 create mode 100644 tools/testing/vma/Makefile
 create mode 100644 tools/testing/vma/errors.txt
 create mode 100644 tools/testing/vma/generated/autoconf.h
 create mode 100644 tools/testing/vma/linux/atomic.h
 create mode 100644 tools/testing/vma/linux/mmzone.h
 create mode 100644 tools/testing/vma/vma.c
 create mode 100644 tools/testing/vma/vma_internal.h

--
2.45.1