[PATCH v5 1/6] mm: add ARCH_SUPPORTS_NON_LEAF_PTDUMP

[Maxwell Bland <mbland@xxxxxxxxxxxx>]

Provide a Kconfig option indicating if note_page can be called for
intermediate page directories during ptdump.

Signed-off-by: Maxwell Bland <mbland@xxxxxxxxxxxx>
---
 mm/Kconfig.debug |  8 ++++++++
 mm/ptdump.c      | 26 ++++++++++++++++++--------
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index afc72fde0f03..41071539bf9e 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -201,6 +201,14 @@ config PTDUMP_DEBUGFS
 
 	  If in doubt, say N.
 
+config ARCH_SUPPORTS_NON_LEAF_PTDUMP
+	bool "Include intermediate directory entries in pagetable dumps"
+	help
+	  Enable the inclusion of intermediate page directory entries in calls
+	  to the ptdump API. Once an architecture defines correct ptdump
+	  behavior for PGD, PUD, P4D, and PMD entries, this config can be
+	  selected.
+
 config HAVE_DEBUG_KMEMLEAK
 	bool
 
diff --git a/mm/ptdump.c b/mm/ptdump.c
index 106e1d66e9f9..3c8eea232282 100644
--- a/mm/ptdump.c
+++ b/mm/ptdump.c
@@ -26,6 +26,11 @@ static inline int note_kasan_page_table(struct mm_walk *walk,
 }
 #endif
 
+static inline bool has_non_leaf_ptdump(void)
+{
+	return IS_ENABLED(CONFIG_ARCH_SUPPORTS_NON_LEAF_PTDUMP);
+}
+
 static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
 			    unsigned long next, struct mm_walk *walk)
 {
@@ -41,10 +46,11 @@ static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
 	if (st->effective_prot)
 		st->effective_prot(st, 0, pgd_val(val));
 
-	if (pgd_leaf(val)) {
+	if (has_non_leaf_ptdump() || pgd_leaf(val))
 		st->note_page(st, addr, 0, pgd_val(val));
+
+	if (pgd_leaf(val))
 		walk->action = ACTION_CONTINUE;
-	}
 
 	return 0;
 }
@@ -64,10 +70,11 @@ static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
 	if (st->effective_prot)
 		st->effective_prot(st, 1, p4d_val(val));
 
-	if (p4d_leaf(val)) {
+	if (has_non_leaf_ptdump() || p4d_leaf(val))
 		st->note_page(st, addr, 1, p4d_val(val));
+
+	if (p4d_leaf(val))
 		walk->action = ACTION_CONTINUE;
-	}
 
 	return 0;
 }
@@ -87,10 +94,11 @@ static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
 	if (st->effective_prot)
 		st->effective_prot(st, 2, pud_val(val));
 
-	if (pud_leaf(val)) {
+	if (has_non_leaf_ptdump() || pud_leaf(val))
 		st->note_page(st, addr, 2, pud_val(val));
+
+	if (pud_leaf(val))
 		walk->action = ACTION_CONTINUE;
-	}
 
 	return 0;
 }
@@ -108,10 +116,12 @@ static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
 
 	if (st->effective_prot)
 		st->effective_prot(st, 3, pmd_val(val));
-	if (pmd_leaf(val)) {
+
+	if (has_non_leaf_ptdump() || pmd_leaf(val))
 		st->note_page(st, addr, 3, pmd_val(val));
+
+	if (pmd_leaf(val))
 		walk->action = ACTION_CONTINUE;
-	}
 
 	return 0;
 }
-- 
2.43.0