[PATCH v7 09/29] mm/debug_vm_pgtable: test PMD swap-exclusive helpers

[Usama Arif <usama.arif@linux.dev>]

An architecture that picked a PMD exclusive bit overlapping the swap type
or offset field would otherwise only be caught by data corruption at
runtime. Mirror pte_swap_exclusive_tests() at PMD level.

Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Usama Arif <usama.arif@linux.dev>
---
 mm/debug_vm_pgtable.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 2875fd22d7bb0..863111c6d4eb3 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -802,6 +802,45 @@ static void __init pte_swap_exclusive_tests(struct pgtable_debug_args *args)
 	WARN_ON(memcmp(&entry, &softleaf, sizeof(entry)));
 }
 
+#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
+static void __init pmd_swap_exclusive_tests(struct pgtable_debug_args *args)
+{
+	swp_entry_t entry;
+	softleaf_t softleaf;
+	pmd_t pmd;
+
+	if (!has_transparent_hugepage())
+		return;
+
+	pr_debug("Validating PMD swap exclusive\n");
+	entry = args->swp_entry;
+
+	pmd = softleaf_to_pmd(entry);
+	softleaf = softleaf_from_pmd(pmd);
+
+	WARN_ON(pmd_swp_exclusive(pmd));
+	WARN_ON(!softleaf_is_swap(softleaf));
+	WARN_ON(memcmp(&entry, &softleaf, sizeof(entry)));
+
+	pmd = pmd_swp_mkexclusive(pmd);
+	softleaf = softleaf_from_pmd(pmd);
+
+	WARN_ON(!pmd_swp_exclusive(pmd));
+	WARN_ON(!softleaf_is_swap(softleaf));
+	WARN_ON(pmd_swp_soft_dirty(pmd));
+	WARN_ON(memcmp(&entry, &softleaf, sizeof(entry)));
+
+	pmd = pmd_swp_clear_exclusive(pmd);
+	softleaf = softleaf_from_pmd(pmd);
+
+	WARN_ON(pmd_swp_exclusive(pmd));
+	WARN_ON(!softleaf_is_swap(softleaf));
+	WARN_ON(memcmp(&entry, &softleaf, sizeof(entry)));
+}
+#else  /* !CONFIG_ARCH_HAS_PMD_SOFTLEAVES */
+static void __init pmd_swap_exclusive_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_ARCH_HAS_PMD_SOFTLEAVES */
+
 static void __init pte_swap_tests(struct pgtable_debug_args *args)
 {
 	swp_entry_t arch_entry;
@@ -1322,6 +1361,7 @@ static int __init debug_vm_pgtable(void)
 	pmd_leaf_soft_dirty_tests(&args);
 
 	pte_swap_exclusive_tests(&args);
+	pmd_swap_exclusive_tests(&args);
 
 	pte_swap_tests(&args);
 	pmd_softleaf_tests(&args);
-- 
2.53.0-Meta