[PATCH v10 14/18] powerpc/32s: map kasan zero shadow with PAGE_READONLY instead of PAGE_KERNEL_RO

[Christophe Leroy]

For hash32, the zero shadow page gets mapped with PAGE_READONLY instead
of PAGE_KERNEL_RO, because the PP bits don't provide a RO kernel, so
PAGE_KERNEL_RO is equivalent to PAGE_KERNEL. By using PAGE_READONLY,
the page is RO for both kernel and user, but this is not a security issue
as it contains only zeroes.

Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
---
 arch/powerpc/mm/kasan/kasan_init_32.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c
index ba8361487075..0d62be3cba47 100644
--- a/arch/powerpc/mm/kasan/kasan_init_32.c
+++ b/arch/powerpc/mm/kasan/kasan_init_32.c
@@ -39,7 +39,10 @@ static int kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_
 
 		if (!new)
 			return -ENOMEM;
-		kasan_populate_pte(new, PAGE_KERNEL_RO);
+		if (early_mmu_has_feature(MMU_FTR_HPTE_TABLE))
+			kasan_populate_pte(new, PAGE_READONLY);
+		else
+			kasan_populate_pte(new, PAGE_KERNEL_RO);
 		pmd_populate_kernel(&init_mm, pmd, new);
 	}
 	return 0;
@@ -84,7 +87,10 @@ static int __ref kasan_init_region(void *start, size_t size)
 
 static void __init kasan_remap_early_shadow_ro(void)
 {
-	kasan_populate_pte(kasan_early_shadow_pte, PAGE_KERNEL_RO);
+	if (early_mmu_has_feature(MMU_FTR_HPTE_TABLE))
+		kasan_populate_pte(kasan_early_shadow_pte, PAGE_READONLY);
+	else
+		kasan_populate_pte(kasan_early_shadow_pte, PAGE_KERNEL_RO);
 
 	flush_tlb_kernel_range(KASAN_SHADOW_START, KASAN_SHADOW_END);
 }
-- 
2.13.3