From 1e338f4d99e6814ede16bad1db1cc463aad8032c Mon Sep 17 00:00:00 2001 From: Sabyrzhan Tasbolatov Date: Sun, 10 Aug 2025 17:57:45 +0500 Subject: 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: Sabyrzhan Tasbolatov Reviewed-by: Christophe Leroy Reviewed-by: Ritesh Harjani (IBM) #powerpc Cc: Alexander Gordeev Cc: Alexander Potapenko Cc: Alexandre Ghiti Cc: Alexandre Ghiti Cc: Andrey Konovalov Cc: Andrey Ryabinin Cc: Baoquan He Cc: David Gow Cc: Dmitriy Vyukov Cc: Heiko Carstens Cc: Huacai Chen Cc: Marco Elver Cc: Qing Zhang Cc: Sabyrzhan Tasbolatov Cc: Vincenzo Frascino Signed-off-by: Andrew Morton --- include/linux/kasan-enabled.h | 32 +++++++++++++++++++++++--------- include/linux/kasan.h | 6 ++++++ 2 files changed, 29 insertions(+), 9 deletions(-) (limited to 'include') diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h index 6f612d69ea0c..9eca967d8526 100644 --- a/include/linux/kasan-enabled.h +++ b/include/linux/kasan-enabled.h @@ -4,32 +4,46 @@ #include -#ifdef CONFIG_KASAN_HW_TAGS - +#if defined(CONFIG_ARCH_DEFER_KASAN) || defined(CONFIG_KASAN_HW_TAGS) +/* + * Global runtime flag for KASAN modes that need runtime control. + * Used by ARCH_DEFER_KASAN architectures and HW_TAGS mode. + */ DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled); +/* + * Runtime control for shadow memory initialization or HW_TAGS mode. + * Uses static key for architectures that need deferred KASAN or HW_TAGS. + */ static __always_inline bool kasan_enabled(void) { return static_branch_likely(&kasan_flag_enabled); } -static inline bool kasan_hw_tags_enabled(void) +static inline void kasan_enable(void) { - return kasan_enabled(); + static_branch_enable(&kasan_flag_enabled); } - -#else /* CONFIG_KASAN_HW_TAGS */ - -static inline bool kasan_enabled(void) +#else +/* For architectures that can enable KASAN early, use compile-time check. */ +static __always_inline bool kasan_enabled(void) { return IS_ENABLED(CONFIG_KASAN); } +static inline void kasan_enable(void) {} +#endif /* CONFIG_ARCH_DEFER_KASAN || CONFIG_KASAN_HW_TAGS */ + +#ifdef CONFIG_KASAN_HW_TAGS +static inline bool kasan_hw_tags_enabled(void) +{ + return kasan_enabled(); +} +#else static inline bool kasan_hw_tags_enabled(void) { return false; } - #endif /* CONFIG_KASAN_HW_TAGS */ #endif /* LINUX_KASAN_ENABLED_H */ diff --git a/include/linux/kasan.h b/include/linux/kasan.h index fe5ce9215821..b509a8d36949 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -543,6 +543,12 @@ void kasan_report_async(void); #endif /* CONFIG_KASAN_HW_TAGS */ +#ifdef CONFIG_KASAN_GENERIC +void __init kasan_init_generic(void); +#else +static inline void kasan_init_generic(void) { } +#endif + #ifdef CONFIG_KASAN_SW_TAGS void __init kasan_init_sw_tags(void); #else -- cgit v1.2.3