diff options
| author | Lorenzo Stoakes (ARM) <ljs@kernel.org> | 2026-09-08 12:23:39 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-09-13 21:31:59 -0700 |
| commit | 11afc077ea3e754568ba953b7191f55d212c9e43 (patch) | |
| tree | c080d44af9d0acb9b4b4504142c77c32c73ef6c3 /tools | |
| parent | 6a2509521d2b309a7c7ca4f4b41bc0c5aaeb76cb (diff) | |
| download | linux-next-11afc077ea3e754568ba953b7191f55d212c9e43.tar.gz linux-next-11afc077ea3e754568ba953b7191f55d212c9e43.zip | |
mm: implement file_is_dev_zero() to uniquely identify /dev/zero
To lay the foundation for a future change that converts
MAP_PRIVATE-/dev/zero mappings to be truly anonymous, add the ability to
uniquely identify these mappings.
With the memory character device now part of mm/ this is trivially
achievable through a file_is_dev_zero() predicate that simply tests that
the file operation hooks are zero_fops.
Also update userland VMA tests to expose file_is_dev_zero() and provide a
stub zero_fops for testing.
Link: https://lore.kernel.org/20260908-map-private-dev-zero-v2-2-acc7b5625305@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/testing/vma/include/dup.h | 7 | ||||
| -rw-r--r-- | tools/testing/vma/shared.c | 9 |
2 files changed, 16 insertions, 0 deletions
diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h index 57046d8ac81d..0d1a2ac88922 100644 --- a/tools/testing/vma/include/dup.h +++ b/tools/testing/vma/include/dup.h @@ -1641,3 +1641,10 @@ static inline pgoff_t linear_anon_page_index(const struct vm_area_struct *vma, return pgoff; } + +extern const struct file_operations zero_fops; + +static inline bool file_is_dev_zero(const struct file *file) +{ + return file && file->f_op == &zero_fops; +} diff --git a/tools/testing/vma/shared.c b/tools/testing/vma/shared.c index 4a39c9d50489..8c4826499f40 100644 --- a/tools/testing/vma/shared.c +++ b/tools/testing/vma/shared.c @@ -12,6 +12,15 @@ const struct vm_operations_struct vma_dummy_vm_ops; struct anon_vma dummy_anon_vma; struct task_struct __current; +static int mmap_zero_prepare(struct vm_area_desc *desc) +{ + return 0; +} + +const struct file_operations zero_fops = { + .mmap_prepare = mmap_zero_prepare, +}; + struct vm_area_struct *alloc_vma(struct mm_struct *mm, unsigned long start, unsigned long end, pgoff_t pgoff, vma_flags_t vma_flags) |