Currently VMA allocation, freeing and duplication exist in kernel/fork.c,
which is a violation of separation of concerns, and leaves these functions
exposed to the rest of the kernel when they are in fact internal
implementation details.

Resolve this by moving this logic to mm, and making it internal to vma.c,
vma.h.

This also allows us, in future, to provide userland testing around this
functionality.

We additionally abstract dup_mmap() to mm, being careful to ensure
kernel/fork.c acceses thi via the mm internal header so it is not exposed
elsewhere in the kernel.

As part of this change, also abstract initial stack allocation performed in
__bprm_mm_init() out of fs code into mm via the create_init_stack_vma(), as
this code uses vm_area_alloc() and vm_area_free().

Lorenzo Stoakes (4):
  mm: abstract initial stack setup to mm subsystem
  mm: perform VMA allocation, freeing, duplication in mm
  mm: move dup_mmap() to mm
  mm: move vm_area_alloc,dup,free() functions to vma.c

 fs/exec.c                        |  51 +-----
 include/linux/mm.h               |  15 +-
 kernel/fork.c                    | 277 +------------------------------
 mm/debug_vm_pgtable.c            |   2 +
 mm/internal.h                    |   2 +
 mm/mmap.c                        | 254 +++++++++++++++++++++++++++-
 mm/nommu.c                       |  75 +++++++++
 mm/vma.c                         |  89 ++++++++++
 mm/vma.h                         |   8 +
 tools/testing/vma/vma.c          |   1 +
 tools/testing/vma/vma_internal.h | 151 +++++++++++++----
 11 files changed, 550 insertions(+), 375 deletions(-)

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2.49.0