[PATCH v4 3/6] kunit: test: Export kunit_attach_mm()

[Tiffany Yang]

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>
Reviewed-by: Carlos Llamas <cmlla...@google.com>
Reviewed-by: Kees Cook <k...@kernel.org>
Signed-off-by: Tiffany Yang <ynaf...@google.com>
---
v4:
* Collected tags
---
 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.
+ */
+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