[kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Tycho Andersen <tycho@docker.com>]

From: Juerg Haefliger <juerg.haefliger@hpe.com>

XPFO (eXclusive Page Frame Ownership) doesn't support section mappings
yet, so disable it if XPFO is turned on.

Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Tested-by: Tycho Andersen <tycho@docker.com>
---
 arch/arm64/mm/mmu.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index f1eb15e0e864..38026b3ccb46 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -176,6 +176,18 @@ static void alloc_init_cont_pte(pmd_t *pmd, unsigned long addr,
 	} while (addr = next, addr != end);
 }
 
+static inline bool use_section_mapping(unsigned long addr, unsigned long next,
+				unsigned long phys)
+{
+	if (IS_ENABLED(CONFIG_XPFO))
+		return false;
+
+	if (((addr | next | phys) & ~SECTION_MASK) != 0)
+		return false;
+
+	return true;
+}
+
 static void init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
 		     phys_addr_t phys, pgprot_t prot,
 		     phys_addr_t (*pgtable_alloc)(void), int flags)
@@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
 		next = pmd_addr_end(addr, end);
 
 		/* try section mapping first */
-		if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
+		if (use_section_mapping(addr, next, phys) &&
 		    (flags & NO_BLOCK_MAPPINGS) == 0) {
 			pmd_set_huge(pmd, phys, prot);
 
-- 
2.11.0