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Message-ID: <7e69c7a6-54ad-4605-ba32-561b985e2aa4@lucifer.local>
Date: Wed, 3 Jul 2024 11:25:29 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
"Liam R . Howlett" <Liam.Howlett@...cle.com>,
Vlastimil Babka <vbabka@...e.cz>, Matthew Wilcox <willy@...radead.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
Eric Biederman <ebiederm@...ssion.com>, Kees Cook <kees@...nel.org>,
Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [RFC PATCH v2 0/7] Make core VMA operations internal and testable
On Fri, Jun 28, 2024 at 03:35:21PM GMT, Lorenzo Stoakes wrote:
> 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/cover.1719481836.git.lstoakes@gmail.com/
>
> 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
>
As this is stabilising and there seems to be no major objections, the next
re-spin will be sent un-RFC'd.
I have a few small fixes on the userland testing code I will include, in
addition to the stuff commented on here.
> 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
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