[PATCH] selftests/mm: refactor common code and improve test skipping in guard_region

[wang lian <lianux.mm@gmail.com>]

Move the generic `FORCE_READ` macro from `guard-regions.c` to the shared
`vm_util.h` header to promote code reuse.

In `guard-regions.c`, replace `ksft_exit_skip()` with the `SKIP()` macro
to ensure only the current test is skipped on permission failure, instead
of terminating the entire test binary.

Signed-off-by: wang lian <lianux.mm@gmail.com>
---
 tools/testing/selftests/mm/guard-regions.c | 9 +--------
 tools/testing/selftests/mm/vm_util.h       | 7 +++++++
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c
index 93af3d3760f9..b0d42eb04e3a 100644
--- a/tools/testing/selftests/mm/guard-regions.c
+++ b/tools/testing/selftests/mm/guard-regions.c
@@ -35,13 +35,6 @@
 static volatile sig_atomic_t signal_jump_set;
 static sigjmp_buf signal_jmp_buf;
 
-/*
- * Ignore the checkpatch warning, we must read from x but don't want to do
- * anything with it in order to trigger a read page fault. We therefore must use
- * volatile to stop the compiler from optimising this away.
- */
-#define FORCE_READ(x) (*(volatile typeof(x) *)x)
-
 /*
  * How is the test backing the mapping being tested?
  */
@@ -582,7 +575,7 @@ TEST_F(guard_regions, process_madvise)
 
 	/* OK we don't have permission to do this, skip. */
 	if (count == -1 && errno == EPERM)
-		ksft_exit_skip("No process_madvise() permissions, try running as root.\n");
+		SKIP(return, "No process_madvise() permissions, try running as root.\n");
 
 	/* Returns the number of bytes advised. */
 	ASSERT_EQ(count, 6 * page_size);
diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
index 2b154c287591..c20298ae98ea 100644
--- a/tools/testing/selftests/mm/vm_util.h
+++ b/tools/testing/selftests/mm/vm_util.h
@@ -18,6 +18,13 @@
 #define PM_SWAP                       BIT_ULL(62)
 #define PM_PRESENT                    BIT_ULL(63)
 
+/*
+ * Ignore the checkpatch warning, we must read from x but don't want to do
+ * anything with it in order to trigger a read page fault. We therefore must use
+ * volatile to stop the compiler from optimising this away.
+ */
+#define FORCE_READ(x) (*(volatile typeof(x) *)x)
+
 extern unsigned int __page_size;
 extern unsigned int __page_shift;
 
-- 
2.43.0