[PATCH 0/4] mm/kasan: remove kasan_arch_is_ready()

[PATCH 0/4] mm/kasan: remove kasan_arch_is_ready()

[Baoquan He]

These are made on top of below patchset in which all functional functions
will be skipped if kasan is disabled by checking kasan_enabled(). With
the changes, kasan_arch_is_ready() can be easily cleaned up to simplify
code.

[PATCH v2 00/12] mm/kasan: make kasan=on|off work for all three modes
https://lore.kernel.org/all/20250812124941.69508-1-bhe@redhat.com/T/#u

The 1st three patches are from Sabyrzhan Tasbolatov's patchset. After
clean up the kasan_arch_is_ready() definition in loongarch, power and UM, 
we can simply remove kasan_arch_is_ready() checking in mm/kasan since
all the checking has been covered by kasan_enabled().

[PATCH v6 0/2] kasan: unify kasan_enabled() and remove arch-specific implementations
https://lore.kernel.org/all/20250810125746.1105476-1-snovitoll@gmail.com/T/#u

Test:
======
I have tested the effect of this patchset on loongarch, power and UM.
Will try to find machine to do testing.

Baoquan He (1):
  mm/kasan: remove kasan_arch_is_ready()

Sabyrzhan Tasbolatov (3):
  arch/loongarch: remove kasan_arch_is_ready()
  arch/powerpc: remove kasan_arch_is_ready()
  arch/um: remove kasan_arch_is_ready()

 arch/loongarch/include/asm/kasan.h     |  7 -------
 arch/loongarch/mm/kasan_init.c         | 10 +++-------
 arch/powerpc/include/asm/kasan.h       | 13 -------------
 arch/powerpc/mm/kasan/init_book3s_64.c |  4 ----
 arch/um/include/asm/kasan.h            |  5 ++---
 arch/um/kernel/mem.c                   |  6 +++++-
 mm/kasan/common.c                      |  9 +++------
 mm/kasan/generic.c                     |  9 ---------
 mm/kasan/kasan.h                       |  6 ------
 mm/kasan/shadow.c                      | 18 ------------------
 10 files changed, 13 insertions(+), 74 deletions(-)

-- 
2.41.0

[PATCH 1/4] arch/loongarch: remove kasan_arch_is_ready()

[Baoquan He]

From: Sabyrzhan Tasbolatov <snovitoll@gmail.com>

With the help of static key kasan_flag_enabled, kasan_arch_is_ready()
is not needed any more. So reomve the unneeded kasan_arch_is_ready() and
the relevant codes.

Here, move kasan_flag_enabled enabling before populating shadow of
liner mapping regions so that kasan_mem_to_shadow() can function well
just as the old variable 'kasan_early_stage' is located.

Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/loongarch/include/asm/kasan.h |  7 -------
 arch/loongarch/mm/kasan_init.c     | 10 +++-------
 2 files changed, 3 insertions(+), 14 deletions(-)

diff --git a/arch/loongarch/include/asm/kasan.h b/arch/loongarch/include/asm/kasan.h
index 62f139a9c87d..0e50e5b5e056 100644
--- a/arch/loongarch/include/asm/kasan.h
+++ b/arch/loongarch/include/asm/kasan.h
@@ -66,7 +66,6 @@
 #define XKPRANGE_WC_SHADOW_OFFSET	(KASAN_SHADOW_START + XKPRANGE_WC_KASAN_OFFSET)
 #define XKVRANGE_VC_SHADOW_OFFSET	(KASAN_SHADOW_START + XKVRANGE_VC_KASAN_OFFSET)
 
-extern bool kasan_early_stage;
 extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
 
 #define kasan_mem_to_shadow kasan_mem_to_shadow
@@ -75,12 +74,6 @@ void *kasan_mem_to_shadow(const void *addr);
 #define kasan_shadow_to_mem kasan_shadow_to_mem
 const void *kasan_shadow_to_mem(const void *shadow_addr);
 
-#define kasan_arch_is_ready kasan_arch_is_ready
-static __always_inline bool kasan_arch_is_ready(void)
-{
-	return !kasan_early_stage;
-}
-
 #define addr_has_metadata addr_has_metadata
 static __always_inline bool addr_has_metadata(const void *addr)
 {
diff --git a/arch/loongarch/mm/kasan_init.c b/arch/loongarch/mm/kasan_init.c
index 0c32eee6910f..f156cba818e6 100644
--- a/arch/loongarch/mm/kasan_init.c
+++ b/arch/loongarch/mm/kasan_init.c
@@ -40,11 +40,9 @@ static pgd_t kasan_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
 #define __pte_none(early, pte) (early ? pte_none(pte) : \
 ((pte_val(pte) & _PFN_MASK) == (unsigned long)__pa(kasan_early_shadow_page)))
 
-bool kasan_early_stage = true;
-
 void *kasan_mem_to_shadow(const void *addr)
 {
-	if (!kasan_arch_is_ready()) {
+	if (!kasan_enabled()) {
 		return (void *)(kasan_early_shadow_page);
 	} else {
 		unsigned long maddr = (unsigned long)addr;
@@ -300,7 +298,8 @@ void __init kasan_init(void)
 	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
 					kasan_mem_to_shadow((void *)KFENCE_AREA_END));
 
-	kasan_early_stage = false;
+	/* Enable KASAN here before kasan_mem_to_shadow(). */
+	static_branch_enable(&kasan_flag_enabled);
 
 	/* Populate the linear mapping */
 	for_each_mem_range(i, &pa_start, &pa_end) {
@@ -329,9 +328,6 @@ void __init kasan_init(void)
 	csr_write64(__pa_symbol(swapper_pg_dir), LOONGARCH_CSR_PGDH);
 	local_flush_tlb_all();
 
-	/* KASAN is now initialized, enable it. */
-	static_branch_enable(&kasan_flag_enabled);
-
 	/* At this point kasan is fully initialized. Enable error messages */
 	init_task.kasan_depth = 0;
 	pr_info("KernelAddressSanitizer initialized.\n");
-- 
2.41.0

[PATCH 2/4] arch/powerpc: remove kasan_arch_is_ready()

[Baoquan He]

From: Sabyrzhan Tasbolatov <snovitoll@gmail.com>

With the help of static key kasan_flag_enabled, kasan_arch_is_ready()
is not needed any more. So reomve the unneeded kasan_arch_is_ready() and
the relevant codes.

Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/powerpc/include/asm/kasan.h       | 13 -------------
 arch/powerpc/mm/kasan/init_book3s_64.c |  4 ----
 2 files changed, 17 deletions(-)

diff --git a/arch/powerpc/include/asm/kasan.h b/arch/powerpc/include/asm/kasan.h
index b5bbb94c51f6..73466d3ff302 100644
--- a/arch/powerpc/include/asm/kasan.h
+++ b/arch/powerpc/include/asm/kasan.h
@@ -53,19 +53,6 @@
 #endif
 
 #ifdef CONFIG_KASAN
-#ifdef CONFIG_PPC_BOOK3S_64
-DECLARE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
-
-static __always_inline bool kasan_arch_is_ready(void)
-{
-	if (static_branch_likely(&powerpc_kasan_enabled_key))
-		return true;
-	return false;
-}
-
-#define kasan_arch_is_ready kasan_arch_is_ready
-#endif
-
 void kasan_early_init(void);
 void kasan_mmu_init(void);
 void kasan_init(void);
diff --git a/arch/powerpc/mm/kasan/init_book3s_64.c b/arch/powerpc/mm/kasan/init_book3s_64.c
index 9c5cf2354c8b..c1b78a9cd0a9 100644
--- a/arch/powerpc/mm/kasan/init_book3s_64.c
+++ b/arch/powerpc/mm/kasan/init_book3s_64.c
@@ -19,8 +19,6 @@
 #include <linux/memblock.h>
 #include <asm/pgalloc.h>
 
-DEFINE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
-
 static void __init kasan_init_phys_region(void *start, void *end)
 {
 	unsigned long k_start, k_end, k_cur;
@@ -95,8 +93,6 @@ void __init kasan_init(void)
 	 */
 	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
 
-	static_branch_inc(&powerpc_kasan_enabled_key);
-
 	/* KASAN is now initialized, enable it. */
 	static_branch_enable(&kasan_flag_enabled);
 
-- 
2.41.0

[PATCH 3/4] arch/um: remove kasan_arch_is_ready()

[Baoquan He]

From: Sabyrzhan Tasbolatov <snovitoll@gmail.com>

With the help of static key kasan_flag_enabled, kasan_arch_is_ready()
is not needed any more. So reomve the unneeded kasan_arch_is_ready() and
the relevant codes.

And also error out if both CONFIG_STATIC_LINK and CONFIG_KASAN_INLINE
are set at the same time as UML supports each of them but done's support
both at the same time.

And also add code comment to explain why static key kasan_flag_enabled
need be deferred to arch_mm_preinit().

Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/um/include/asm/kasan.h | 5 ++---
 arch/um/kernel/mem.c        | 6 +++++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/um/include/asm/kasan.h b/arch/um/include/asm/kasan.h
index f97bb1f7b851..b54a4e937fd1 100644
--- a/arch/um/include/asm/kasan.h
+++ b/arch/um/include/asm/kasan.h
@@ -24,10 +24,9 @@
 
 #ifdef CONFIG_KASAN
 void kasan_init(void);
-extern int kasan_um_is_ready;
 
-#ifdef CONFIG_STATIC_LINK
-#define kasan_arch_is_ready() (kasan_um_is_ready)
+#if defined(CONFIG_STATIC_LINK) && defined(CONFIG_KASAN_INLINE)
+#error UML does not work in KASAN_INLINE mode with STATIC_LINK enabled!
 #endif
 #else
 static inline void kasan_init(void) { }
diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index 392a23d4ef96..d62f494e0808 100644
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c
@@ -35,7 +35,11 @@ void kasan_init(void)
 	 */
 	kasan_map_memory((void *)KASAN_SHADOW_START, KASAN_SHADOW_SIZE);
 	init_task.kasan_depth = 0;
-	kasan_um_is_ready = true;
+	/*
+	 * Since kasan_init() is called before main(),
+	 * KASAN is initialized but the enablement is deferred after
+	 * jump_label_init(). See arch_mm_preinit().
+	 */
 }
 
 static void (*kasan_init_ptr)(void)
-- 
2.41.0

[PATCH 4/4] mm/kasan: remove kasan_arch_is_ready()

[Baoquan He]

Now there's no any place where kasan_arch_is_ready() is needed, remove
all its invocations.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 mm/kasan/common.c  |  9 +++------
 mm/kasan/generic.c |  9 ---------
 mm/kasan/kasan.h   |  6 ------
 mm/kasan/shadow.c  | 18 ------------------
 4 files changed, 3 insertions(+), 39 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 69a848f2a8aa..e48c1fd60edf 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -271,7 +271,7 @@ static inline void poison_slab_object(struct kmem_cache *cache, void *object,
 bool __kasan_slab_pre_free(struct kmem_cache *cache, void *object,
 				unsigned long ip)
 {
-	if (!kasan_arch_is_ready() || is_kfence_address(object))
+	if (is_kfence_address(object))
 		return false;
 	return check_slab_allocation(cache, object, ip);
 }
@@ -279,7 +279,7 @@ bool __kasan_slab_pre_free(struct kmem_cache *cache, void *object,
 bool __kasan_slab_free(struct kmem_cache *cache, void *object, bool init,
 		       bool still_accessible)
 {
-	if (!kasan_arch_is_ready() || is_kfence_address(object))
+	if (is_kfence_address(object))
 		return false;
 
 	/*
@@ -318,9 +318,6 @@ bool __kasan_slab_free(struct kmem_cache *cache, void *object, bool init,
 
 static inline bool check_page_allocation(void *ptr, unsigned long ip)
 {
-	if (!kasan_arch_is_ready())
-		return false;
-
 	if (ptr != page_address(virt_to_head_page(ptr))) {
 		kasan_report_invalid_free(ptr, ip, KASAN_REPORT_INVALID_FREE);
 		return true;
@@ -547,7 +544,7 @@ bool __kasan_mempool_poison_object(void *ptr, unsigned long ip)
 		return true;
 	}
 
-	if (is_kfence_address(ptr) || !kasan_arch_is_ready())
+	if (is_kfence_address(ptr))
 		return true;
 
 	slab = folio_slab(folio);
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 8daea5892754..d513e3e2e136 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -168,9 +168,6 @@ static __always_inline bool check_region_inline(const void *addr,
 	if (!kasan_enabled())
 		return true;
 
-	if (!kasan_arch_is_ready())
-		return true;
-
 	if (unlikely(size == 0))
 		return true;
 
@@ -196,9 +193,6 @@ bool kasan_byte_accessible(const void *addr)
 {
 	s8 shadow_byte;
 
-	if (!kasan_arch_is_ready())
-		return true;
-
 	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));
 
 	return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE;
@@ -505,9 +499,6 @@ static void release_alloc_meta(struct kasan_alloc_meta *meta)
 
 static void release_free_meta(const void *object, struct kasan_free_meta *meta)
 {
-	if (!kasan_arch_is_ready())
-		return;
-
 	/* Check if free meta is valid. */
 	if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_SLAB_FREE_META)
 		return;
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 129178be5e64..e0ffc16495d7 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -544,12 +544,6 @@ static inline void kasan_poison_last_granule(const void *address, size_t size) {
 
 #endif /* CONFIG_KASAN_GENERIC */
 
-#ifndef kasan_arch_is_ready
-static inline bool kasan_arch_is_ready(void)	{ return true; }
-#elif !defined(CONFIG_KASAN_GENERIC) || !defined(CONFIG_KASAN_OUTLINE)
-#error kasan_arch_is_ready only works in KASAN generic outline mode!
-#endif
-
 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
 
 void kasan_kunit_test_suite_start(void);
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 637f2d02d2a3..d8b975282b22 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -128,9 +128,6 @@ void kasan_poison(const void *addr, size_t size, u8 value, bool init)
 	if (!kasan_enabled())
 		return;
 
-	if (!kasan_arch_is_ready())
-		return;
-
 	/*
 	 * Perform shadow offset calculation based on untagged address, as
 	 * some of the callers (e.g. kasan_poison_new_object) pass tagged
@@ -156,9 +153,6 @@ void kasan_poison_last_granule(const void *addr, size_t size)
 	if (!kasan_enabled())
 		return;
 
-	if (!kasan_arch_is_ready())
-		return;
-
 	if (size & KASAN_GRANULE_MASK) {
 		u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size);
 		*shadow = size & KASAN_GRANULE_MASK;
@@ -402,9 +396,6 @@ int kasan_populate_vmalloc(unsigned long addr, unsigned long size)
 	if (!kasan_enabled())
 		return 0;
 
-	if (!kasan_arch_is_ready())
-		return 0;
-
 	if (!is_vmalloc_or_module_addr((void *)addr))
 		return 0;
 
@@ -575,9 +566,6 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
 	if (!kasan_enabled())
 		return;
 
-	if (!kasan_arch_is_ready())
-		return;
-
 	region_start = ALIGN(start, KASAN_MEMORY_PER_SHADOW_PAGE);
 	region_end = ALIGN_DOWN(end, KASAN_MEMORY_PER_SHADOW_PAGE);
 
@@ -626,9 +614,6 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
 	 * with setting memory tags, so the KASAN_VMALLOC_INIT flag is ignored.
 	 */
 
-	if (!kasan_arch_is_ready())
-		return (void *)start;
-
 	if (!is_vmalloc_or_module_addr(start))
 		return (void *)start;
 
@@ -651,9 +636,6 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
  */
 void __kasan_poison_vmalloc(const void *start, unsigned long size)
 {
-	if (!kasan_arch_is_ready())
-		return;
-
 	if (!is_vmalloc_or_module_addr(start))
 		return;
 
-- 
2.41.0