linux-kernel - [PATCH 0/5] mm/vma: make more mmap logic userland testable

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Message-ID: <cover.1733248985.git.lorenzo.stoakes@oracle.com>
Date: Tue,  3 Dec 2024 18:05:07 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        Eric Biederman <ebiederm@...ssion.com>, Kees Cook <kees@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 0/5] mm/vma: make more mmap logic userland testable

This series carries on the work the work started in previous series and
continued in commit 52956b0d7fb9 ("mm: isolate mmap internal logic to
mm/vma.c"), moving the remainder of memory mapping implementation details
logic into mm/vma.c allowing the bulk of the mapping logic to be unit
tested.

It is highly useful to do so, as this means we can both fundamentally test
this core logic, and introduce regression tests to ensure any issues
previously resolved do not recur.

Vitally, this includes the do_brk_flags() function, meaning we have both
core means of userland mapping memory now testable.

Performance testing was performed after this change given the brk() system
call's sensitivity to change, and no performance regression was observed.

The stack expansion logic is also moved into mm/vma.c, which necessitates a
change in the API exposed to the exec code, removing the invocation of the
expand_downwards() function used in get_arg_page() and instead adding
mmap_read_lock_maybe_expand() to wrap this.

Lorenzo Stoakes (5):
  mm/vma: move brk() internals to mm/vma.c
  mm/vma: move unmapped_area() internals to mm/vma.c
  mm: abstract get_arg_page() stack expansion and mmap read lock
  mm/vma: move stack expansion logic to mm/vma.c
  mm/vma: move __vm_munmap() to mm/vma.c

 fs/exec.c                        |  14 +-
 include/linux/mm.h               |   5 +-
 mm/mmap.c                        | 469 ++++--------------------------
 mm/vma.c                         | 478 ++++++++++++++++++++++++++++---
 mm/vma.h                         |  20 +-
 tools/testing/vma/vma.c          |  11 +
 tools/testing/vma/vma_internal.h | 152 ++++++++++
 7 files changed, 681 insertions(+), 468 deletions(-)

--
2.47.1