[PATCH v4 14/39] kasan, arm64: only init shadow for software modes

[Andrey Konovalov]

This is a preparatory commit for the upcoming addition of a new hardware
tag-based (MTE-based) KASAN mode.

Hardware tag-based KASAN won't be using shadow memory. Only initialize
it when one of the software KASAN modes are enabled.

No functional changes for software modes.

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
---
Change-Id: I055e0651369b14d3e54cdaa8c48e6329b2e8952d
---
 arch/arm64/include/asm/kasan.h |  8 ++++++--
 arch/arm64/mm/kasan_init.c     | 15 ++++++++++++++-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kasan.h b/arch/arm64/include/asm/kasan.h
index b0dc4abc3589..f7ea70d02cab 100644
--- a/arch/arm64/include/asm/kasan.h
+++ b/arch/arm64/include/asm/kasan.h
@@ -13,6 +13,12 @@
 #define arch_kasan_get_tag(addr)	__tag_get(addr)
 
 #ifdef CONFIG_KASAN
+void kasan_init(void);
+#else
+static inline void kasan_init(void) { }
+#endif
+
+#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 
 /*
  * KASAN_SHADOW_START: beginning of the kernel virtual addresses.
@@ -33,12 +39,10 @@
 #define _KASAN_SHADOW_START(va)	(KASAN_SHADOW_END - (1UL << ((va) - KASAN_SHADOW_SCALE_SHIFT)))
 #define KASAN_SHADOW_START      _KASAN_SHADOW_START(vabits_actual)
 
-void kasan_init(void);
 void kasan_copy_shadow(pgd_t *pgdir);
 asmlinkage void kasan_early_init(void);
 
 #else
-static inline void kasan_init(void) { }
 static inline void kasan_copy_shadow(pgd_t *pgdir) { }
 #endif
 
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 7291b26ce788..4d35eaf3ec97 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -21,6 +21,8 @@
 #include <asm/sections.h>
 #include <asm/tlbflush.h>
 
+#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
+
 static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
 
 /*
@@ -208,7 +210,7 @@ static void __init clear_pgds(unsigned long start,
 		set_pgd(pgd_offset_k(start), __pgd(0));
 }
 
-void __init kasan_init(void)
+static void __init kasan_init_shadow(void)
 {
 	u64 kimg_shadow_start, kimg_shadow_end;
 	u64 mod_shadow_start, mod_shadow_end;
@@ -269,6 +271,17 @@ void __init kasan_init(void)
 
 	memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
 	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
+}
+
+#else /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS) */
+
+static inline void __init kasan_init_shadow(void) { }
+
+#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
+
+void __init kasan_init(void)
+{
+	kasan_init_shadow();
 
 	/* At this point kasan is fully initialized. Enable error messages */
 	init_task.kasan_depth = 0;
-- 
2.28.0.709.gb0816b6eb0-goog