[PATCH v1 3/4] arm64: mm: Introduce linear_map_needs_set() helper

[Vincent Donnefort]

can_set_direct_map() is intended as an external query function, but is
also being called internally by map_mem() to initialise
linear_map_requires_bbml3, duplicating the feature checks already
present in force_pte_mapping().

Factor the list of features that require modifying linear map attributes
into a shared helper linear_map_needs_set().

Signed-off-by: Vincent Donnefort <vdonnefort at google.com>
---
 arch/arm64/include/asm/mmu.h |  1 +
 arch/arm64/mm/mmu.c          | 22 ++++++++++++++++++++--
 arch/arm64/mm/pageattr.c     | 12 +-----------
 3 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 5e1211c540ab..12ed21e2d0d7 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -70,6 +70,7 @@ extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 			       pgprot_t prot, bool page_mappings_only);
 extern void *fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot);
 extern void mark_linear_text_alias_ro(void);
+extern bool linear_map_needs_set(void);
 extern int split_kernel_leaf_mapping(unsigned long start, unsigned long end);
 extern void linear_map_maybe_split_to_ptes(void);
 
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 79d90226fd5d..c18ed601f0a8 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -776,6 +776,24 @@ static int split_kernel_leaf_mapping_locked(unsigned long addr)
 	return ret;
 }
 
+/*
+ * True if the linear map needs to be modified for one of the following
+ * features:
+ *
+ * rodata_full and DEBUG_PAGEALLOC need to protect/unprotect pages in
+ * the linear map.
+ *
+ * KFENCE pool needs to protect/unprotect pages in the linear map if
+ * initialized late.
+ *
+ * Realms need to mark pages shared/protected in the linear map.
+ */
+bool linear_map_needs_set(void)
+{
+	return rodata_full || debug_pagealloc_enabled() ||
+	       arm64_kfence_can_set_direct_map() || is_realm_world();
+}
+
 static inline bool force_pte_mapping(void)
 {
 	const bool bbml3 = system_capabilities_finalized() ?
@@ -785,7 +803,7 @@ static inline bool force_pte_mapping(void)
 		return true;
 	if (bbml3)
 		return false;
-	return rodata_full || arm64_kfence_can_set_direct_map() || is_realm_world();
+	return linear_map_needs_set();
 }
 
 static DEFINE_MUTEX(pgtable_split_lock);
@@ -1203,7 +1221,7 @@ static void __init map_mem(void)
 
 	arm64_kfence_map_pool();
 
-	linear_map_requires_bbml3 = !force_pte_mapping() && can_set_direct_map();
+	linear_map_requires_bbml3 = !force_pte_mapping() && linear_map_needs_set();
 
 	if (force_pte_mapping())
 		flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index bbe98ac9ad8c..c1ba74eb602f 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -89,17 +89,7 @@ bool rodata_full __ro_after_init = true;
 
 bool can_set_direct_map(void)
 {
-	/*
-	 * rodata_full, DEBUG_PAGEALLOC and a Realm guest all require linear
-	 * map to be mapped at page granularity, so that it is possible to
-	 * protect/unprotect single pages.
-	 *
-	 * KFENCE pool requires page-granular mapping if initialized late.
-	 *
-	 * Realms need to make pages shared/protected at page granularity.
-	 */
-	return rodata_full || debug_pagealloc_enabled() ||
-		arm64_kfence_can_set_direct_map() || is_realm_world();
+	return linear_map_needs_set();
 }
 
 static int update_range_prot(unsigned long start, unsigned long size,
-- 
2.55.0.1082.g2b9226bbc0-goog