[RFC PATCH v3 11/15] mm: Map page tables with privileged pkey

[Kevin Brodsky]

If CONFIG_KPKEYS_HARDENED_PGTABLES is enabled, map allocated page
table pages using a privileged pkey (KPKEYS_PKEY_PGTABLES), so that
page tables can only be written under guard(kpkeys_hardened_pgtables).

This patch is a no-op if CONFIG_KPKEYS_HARDENED_PGTABLES is disabled
(default).

Signed-off-by: Kevin Brodsky <kevin.brod...@arm.com>
---
 include/linux/mm.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 721e779647f3..aa01f51fdc6f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -32,6 +32,7 @@
 #include <linux/memremap.h>
 #include <linux/slab.h>
 #include <linux/cacheinfo.h>
+#include <linux/kpkeys.h>
 
 struct mempolicy;
 struct anon_vma;
@@ -2998,6 +2999,8 @@ static inline bool __pagetable_ctor(struct ptdesc *ptdesc)
 
        __folio_set_pgtable(folio);
        lruvec_stat_add_folio(folio, NR_PAGETABLE);
+       if (kpkeys_protect_pgtable_memory(folio))
+               return false;
        return true;
 }
 
@@ -3008,6 +3011,7 @@ static inline void pagetable_dtor(struct ptdesc *ptdesc)
        ptlock_free(ptdesc);
        __folio_clear_pgtable(folio);
        lruvec_stat_sub_folio(folio, NR_PAGETABLE);
+       kpkeys_unprotect_pgtable_memory(folio);
 }
 
 static inline void pagetable_dtor_free(struct ptdesc *ptdesc)
-- 
2.47.0