Commit 1e338f4d authored by Sabyrzhan Tasbolatov's avatar Sabyrzhan Tasbolatov Committed by Andrew Morton
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kasan: introduce ARCH_DEFER_KASAN and unify static key across modes 

Patch series "kasan: unify kasan_enabled() and remove arch-specific
implementations", v6.

This patch series addresses the fragmentation in KASAN initialization
across architectures by introducing a unified approach that eliminates
duplicate static keys and arch-specific kasan_arch_is_ready()
implementations.

The core issue is that different architectures have inconsistent approaches
to KASAN readiness tracking:
- PowerPC, LoongArch, and UML arch, each implement own kasan_arch_is_ready()
- Only HW_TAGS mode had a unified static key (kasan_flag_enabled)
- Generic and SW_TAGS modes relied on arch-specific solutions
  or always-on behavior


This patch (of 2):

Introduce CONFIG_ARCH_DEFER_KASAN to identify architectures [1] that need
to defer KASAN initialization until shadow memory is properly set up, and
unify the static key infrastructure across all KASAN modes.

[1] PowerPC, UML, LoongArch selects ARCH_DEFER_KASAN.

The core issue is that different architectures haveinconsistent approaches
to KASAN readiness tracking:
- PowerPC, LoongArch, and UML arch, each implement own
  kasan_arch_is_ready()
- Only HW_TAGS mode had a unified static key (kasan_flag_enabled)
- Generic and SW_TAGS modes relied on arch-specific solutions or always-on
    behavior

This patch addresses the fragmentation in KASAN initialization across
architectures by introducing a unified approach that eliminates duplicate
static keys and arch-specific kasan_arch_is_ready() implementations.

Let's replace kasan_arch_is_ready() with existing kasan_enabled() check,
which examines the static key being enabled if arch selects
ARCH_DEFER_KASAN or has HW_TAGS mode support.  For other arch,
kasan_enabled() checks the enablement during compile time.

Now KASAN users can use a single kasan_enabled() check everywhere.

Link: https://lkml.kernel.org/r/20250810125746.1105476-1-snovitoll@gmail.com
Link: https://lkml.kernel.org/r/20250810125746.1105476-2-snovitoll@gmail.com
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217049


Signed-off-by: default avatarSabyrzhan Tasbolatov <snovitoll@gmail.com>
Reviewed-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> #powerpc
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: David Gow <davidgow@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Marco Elver <elver@google.com>
Cc: Qing Zhang <zhangqing@loongson.cn>
Cc: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent bc9950b5

arch/loongarch/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ config LOONGARCH 
	select ACPI_PPTT if ACPI

	select ACPI_SYSTEM_POWER_STATES_SUPPORT	if ACPI

	select ARCH_BINFMT_ELF_STATE

	select ARCH_NEEDS_DEFER_KASAN

	select ARCH_DISABLE_KASAN_INLINE

	select ARCH_ENABLE_MEMORY_HOTPLUG

	select ARCH_ENABLE_MEMORY_HOTREMOVE

arch/loongarch/include/asm/kasan.h

+0 −7
Original line number Diff line number Diff line
@@ -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)

{

arch/loongarch/mm/kasan_init.c

+3 −5
Original line number Diff line number Diff line
@@ -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;
@@ -298,7 +296,8 @@ 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(). */

	kasan_init_generic();



	/* Populate the linear mapping */

	for_each_mem_range(i, &pa_start, &pa_end) {
@@ -329,5 +328,4 @@ void __init kasan_init(void) 


	/* At this point kasan is fully initialized. Enable error messages */

	init_task.kasan_depth = 0;

	pr_info("KernelAddressSanitizer initialized.\n");

}

arch/powerpc/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -122,6 +122,7 @@ config PPC 
	# Please keep this list sorted alphabetically.

	#

	select ARCH_32BIT_OFF_T if PPC32

	select ARCH_NEEDS_DEFER_KASAN		if PPC_RADIX_MMU

	select ARCH_DISABLE_KASAN_INLINE	if PPC_RADIX_MMU

	select ARCH_DMA_DEFAULT_COHERENT	if !NOT_COHERENT_CACHE

	select ARCH_ENABLE_MEMORY_HOTPLUG

arch/powerpc/include/asm/kasan.h

+0 −12
Original line number Diff line number Diff line
@@ -53,18 +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);