On Mon, Jul 14, 2025 at 11:53:16AM -0700, Tiffany Yang wrote:
> Tests can allocate from virtual memory using kunit_vm_mmap(), which
> transparently creates and attaches an mm_struct to the test runner if
> one is not already attached. This is suitable for most cases, except for
> when the code under test must access a task's mm before performing an
> mmap. Expose kunit_attach_mm() as part of the interface for those
> cases. This does not change the existing behavior.
>
> Cc: David Gow <david...@google.com>
> Signed-off-by: Tiffany Yang <ynaf...@google.com>
> ---
> include/kunit/test.h | 12 ++++++++++++
> lib/kunit/user_alloc.c | 4 ++--
> 2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/include/kunit/test.h b/include/kunit/test.h
> index 39c768f87dc9..d958ee53050e 100644
> --- a/include/kunit/test.h
> +++ b/include/kunit/test.h
> @@ -531,6 +531,18 @@ static inline char *kunit_kstrdup(struct kunit *test,
> const char *str, gfp_t gfp
> */
> const char *kunit_kstrdup_const(struct kunit *test, const char *str, gfp_t
> gfp);
>
> +/**
> + * kunit_attach_mm() - Create and attach a new mm if it doesn't already
> exist.
> + *
> + * Allocates a &struct mm_struct and attaches it to @current. In most cases,
> call
> + * kunit_vm_mmap() without calling kunit_attach_mm() directly. Only
> necessary when
> + * code under test accesses the mm before executing the mmap (e.g., to
> perform
> + * additional initialization beforehand).
> + *
> + * Return: 0 on success, -errno on failure.
> + */
Yay kern-doc! :)
> +int kunit_attach_mm(void);
> +
> /**
> * kunit_vm_mmap() - Allocate KUnit-tracked vm_mmap() area
> * @test: The test context object.
> diff --git a/lib/kunit/user_alloc.c b/lib/kunit/user_alloc.c
> index 46951be018be..b8cac765e620 100644
> --- a/lib/kunit/user_alloc.c
> +++ b/lib/kunit/user_alloc.c
> @@ -22,8 +22,7 @@ struct kunit_vm_mmap_params {
> unsigned long offset;
> };
>
> -/* Create and attach a new mm if it doesn't already exist. */
> -static int kunit_attach_mm(void)
> +int kunit_attach_mm(void)
> {
> struct mm_struct *mm;
>
> @@ -49,6 +48,7 @@ static int kunit_attach_mm(void)
>
> return 0;
> }
> +EXPORT_SYMBOL_GPL(kunit_attach_mm);
>
> static int kunit_vm_mmap_init(struct kunit_resource *res, void *context)
> {
> --
> 2.50.0.727.gbf7dc18ff4-goog
Reviewed-by: Kees Cook <k...@kernel.org>
--
Kees Cook
