From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f46.google.com (mail-ej1-f46.google.com [209.85.218.46]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 81CF6245000; Mon, 21 Jul 2025 23:00:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.46 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753138806; cv=none; b=Ny6XuS88auHlIGBlzEN6Xq1HBApf7wvucMj++VDmgRWuEK/+6nolC/zx+8XoGLu5uYUGBz7Hs+vNFe4niAxBemjLvNur/F4xiPXQ1w6Akr44l4mB1yR7Bt0SLhQPufi8UK0kTl/tg1eAgNuVGB2Vo4Qr2W4AVdsdcQcnL5aelDw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753138806; c=relaxed/simple; bh=Z4t0N4zJtY+ZALM0nLgOvZ3qBtBlLR+k/znNuxMGyCQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sVEWYNgY36xc+sXL/YNlOG49TlVynOKyBs/g9LxqE9m8JuJfamV+XcAlGchxNPIRk/yVYP6T3bYKgL53tAB2O/+O8qqeRz0KJhtWNjXAs2wuL6RMYhSP+O3R95AEJ5NRtqnRT4CVcVXilwwF/h/DowroAE7Y8cgvvp25XcNO11s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=H7vyvIla; arc=none smtp.client-ip=209.85.218.46 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="H7vyvIla" Received: by mail-ej1-f46.google.com with SMTP id a640c23a62f3a-ae0b98ccc57so84288866b.0; Mon, 21 Jul 2025 16:00:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1753138803; x=1753743603; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=/MErh+IJZfEbaFHl36LqhlLVHvlXTKmbu8riveWqw+Q=; b=H7vyvIlatHEOa2IsIDUmOmMg7Ofmbv5ogVouhIJ3cUjQchLUWkRHErTHVMuhGlCMEZ aZeZN6Kp6Ti2gUHsQqNqgLJPKjKB2lTdP6sieH7DA2ynKrL2oHSAM+7wCUcE5XgfRIDx VibQTHkGAmO1a1rRy6nU61Hfi7T0Xw29n/ViKLI2c7ElCgQ1w/ya3W1aPWiYlTeubn/B aPwQO7L6yxM9tVseQGJih1vpcKHpRkOO0c5uJS2rCdmAEb2+EvQFrKfDqlhBHGUz6RxK 1IBCXXpSvVSS/zx8tftcs5kz9rrS5vxpCLKfHn8mxWF2QA8ZZFjjZpfSGqkpgGdnLUJE 3FoA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1753138803; x=1753743603; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=/MErh+IJZfEbaFHl36LqhlLVHvlXTKmbu8riveWqw+Q=; b=kgSJAyn7zm6cN0CtCFtOqKlesHia+D1pa3eE2cwTjwKV1TNCq6EM+O0z4qctEjFp94 ajX5CfJsI7+xHGzIjeXwjgYKlQqilX0Wgk+kkO3Sr4YuF4xiPYGmKpFfR7sbHJ6fhuDn zo8K0Teu3l8cF6aGBVSs2IEYQFtivLC4V3EfPbxZNtkPbPlAjyt6llIqvqVnOe3Zdnc7 CB86Xotp5pdggCKrn598cRKa9jLd/yM38nQWTU5KlubVd67UgbKcjRsZHJIHG/Egyr7/ GTy1gbe3gmc5NB7eCh9cDUg7mUQHrViwV677Na/sdjwmyz2Y4d8Nb1mpuWs+PbIiO6zY zsXg== X-Forwarded-Encrypted: i=1; AJvYcCW4+2a82oJhj6xVFesxBzUSH3sDhcFvfWorip9eIwsjlz3LAUj+c7K5w9JP93HX9Fvgko0q+pw6oiyWxCI=@vger.kernel.org, AJvYcCX3IvNadThwU3X199Zxt7a/T+Yu32YpAPACaPQ1emMr0RCUQm9vcJtkyaHMG9RGggmBwFlMGobpgKNZGw==@vger.kernel.org X-Gm-Message-State: AOJu0Yw8a2+qX/PMDe9be9n7zSdne09dIyhwEo5FaS27gZSx8mLYD4Qz /CSLFaOYSGFk1FZlIaAV9dWlIaWzoVkMhbIrZz4cHOLK5IiThlZkkf6rZ1GyAy7P70k= X-Gm-Gg: ASbGnctpDxSAitGE3n7OBUih5QyAOwcphwxHrbpLUoi/WsO20ueco7/TeKcXpcjvnAc s7KlqW8z2GhOWllN9jsxrOJwC3Ec7gzTy0M1G4Shz1ttS5LFc0nGw2Zawlo0EHdaAaPT4C/vqMR zKEYil1HYwIwWopv9l+NnEP1Ehvhi6BniFRK2K1Kg4ZpU+ESnO8UZ4DXe9shUr5YJF8c5a/riyE YwDsUVPvP6hUK9OWbZM8jT4cE3Yj0gMAYjEkPevzeabEFjlVwmidoSAqMmzyfSXx+n1nV8uZQBc h4eQetSYLm5yFLGHkGRYGOH5RARqK2JCyOvTWlTWsCfFOBpPm7KIBlx2lyxTTH5R0Yy6C1KDwG8 9Vvh1TXAi7EDXWokHNs9yabBneubGQtudYDQecT1kvnvdXX1VDV3o41Mg1PfG2kGfm0lC X-Google-Smtp-Source: AGHT+IFhWRkAjq0kp3rYVJajv166B7T+5igJwYiG9mr5QC8ggMyhPPllogHKb3eusDQL2P7c9HNNmg== X-Received: by 2002:a05:6402:3582:b0:612:b0d9:3969 with SMTP id 4fb4d7f45d1cf-612b0d93f03mr5896945a12.8.1753138802656; Mon, 21 Jul 2025 16:00:02 -0700 (PDT) Received: from [192.168.0.18] (cable-94-189-142-142.dynamic.sbb.rs. [94.189.142.142]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-612c8f543ddsm5962670a12.30.2025.07.21.16.00.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Jul 2025 16:00:01 -0700 (PDT) Message-ID: <8f93322a-84c1-402b-b8d4-9c66a2b07b0b@gmail.com> Date: Tue, 22 Jul 2025 00:59:41 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 02/12] kasan: unify static kasan_flag_enabled across modes To: Sabyrzhan Tasbolatov , hca@linux.ibm.com, christophe.leroy@csgroup.eu, andreyknvl@gmail.com, agordeev@linux.ibm.com, akpm@linux-foundation.org Cc: glider@google.com, dvyukov@google.com, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-um@lists.infradead.org, linux-mm@kvack.org References: <20250717142732.292822-1-snovitoll@gmail.com> <20250717142732.292822-3-snovitoll@gmail.com> Content-Language: en-US From: Andrey Ryabinin In-Reply-To: <20250717142732.292822-3-snovitoll@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/17/25 4:27 PM, Sabyrzhan Tasbolatov wrote: > Historically, the runtime static key kasan_flag_enabled existed only for > CONFIG_KASAN_HW_TAGS mode. Generic and SW_TAGS modes either relied on > architecture-specific kasan_arch_is_ready() implementations or evaluated > KASAN checks unconditionally, leading to code duplication. > > This patch implements two-level approach: > > 1. kasan_enabled() - controls if KASAN is enabled at all (compile-time) > 2. kasan_shadow_initialized() - tracks shadow memory > initialization (runtime) > > For architectures that select ARCH_DEFER_KASAN: kasan_shadow_initialized() > uses a static key that gets enabled when shadow memory is ready. > > For architectures that don't: kasan_shadow_initialized() returns > IS_ENABLED(CONFIG_KASAN) since shadow is ready from the start. > > This provides: > - Consistent interface across all KASAN modes > - Runtime control only where actually needed > - Compile-time constants for optimal performance where possible > - Clear separation between "KASAN configured" vs "shadow ready" > > Also adds kasan_init_generic() function that enables the shadow flag and > handles initialization for Generic mode, and updates SW_TAGS and HW_TAGS > to use the unified kasan_shadow_enable() function. > > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217049 > Signed-off-by: Sabyrzhan Tasbolatov > --- > Changes in v3: > - Only architectures that need deferred KASAN get runtime overhead > - Added kasan_shadow_initialized() for shadow memory readiness tracking > - kasan_enabled() now provides compile-time check for KASAN configuration > --- > include/linux/kasan-enabled.h | 34 ++++++++++++++++++++++++++-------- > include/linux/kasan.h | 6 ++++++ > mm/kasan/common.c | 9 +++++++++ > mm/kasan/generic.c | 11 +++++++++++ > mm/kasan/hw_tags.c | 9 +-------- > mm/kasan/sw_tags.c | 2 ++ > 6 files changed, 55 insertions(+), 16 deletions(-) > > diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h > index 6f612d69ea0..fa99dc58f95 100644 > --- a/include/linux/kasan-enabled.h > +++ b/include/linux/kasan-enabled.h > @@ -4,32 +4,50 @@ > > #include > > -#ifdef CONFIG_KASAN_HW_TAGS > +/* Controls whether KASAN is enabled at all (compile-time check). */ > +static __always_inline bool kasan_enabled(void) > +{ > + return IS_ENABLED(CONFIG_KASAN); > +} > > +#ifdef CONFIG_ARCH_DEFER_KASAN > +/* > + * Global runtime flag for architectures that need deferred KASAN. > + * Switched to 'true' by the appropriate kasan_init_*() > + * once KASAN is fully initialized. > + */ > DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled); > > -static __always_inline bool kasan_enabled(void) > +static __always_inline bool kasan_shadow_initialized(void) > { > return static_branch_likely(&kasan_flag_enabled); > } > > -static inline bool kasan_hw_tags_enabled(void) > +static inline void kasan_enable(void) > +{ > + static_branch_enable(&kasan_flag_enabled); > +} > +#else > +/* For architectures that can enable KASAN early, use compile-time check. */ > +static __always_inline bool kasan_shadow_initialized(void) > { > return kasan_enabled(); > } > > -#else /* CONFIG_KASAN_HW_TAGS */ > +/* No-op for architectures that don't need deferred KASAN. */ > +static inline void kasan_enable(void) {} > +#endif /* CONFIG_ARCH_DEFER_KASAN */ > > -static inline bool kasan_enabled(void) > +#ifdef CONFIG_KASAN_HW_TAGS > +static inline bool kasan_hw_tags_enabled(void) > { > - return IS_ENABLED(CONFIG_KASAN); > + 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 890011071f2..51a8293d1af 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 > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index ed4873e18c7..c3a6446404d 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -32,6 +32,15 @@ > #include "kasan.h" > #include "../slab.h" > > +#ifdef CONFIG_ARCH_DEFER_KASAN > +/* > + * Definition of the unified static key declared in kasan-enabled.h. > + * This provides consistent runtime enable/disable across KASAN modes. > + */ > +DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled); > +EXPORT_SYMBOL(kasan_flag_enabled); > +#endif > + > struct slab *kasan_addr_to_slab(const void *addr) > { > if (virt_addr_valid(addr)) > diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c > index d54e89f8c3e..03b6d322ff6 100644 > --- a/mm/kasan/generic.c > +++ b/mm/kasan/generic.c > @@ -36,6 +36,17 @@ > #include "kasan.h" > #include "../slab.h" > > +/* > + * Initialize Generic KASAN and enable runtime checks. > + * This should be called from arch kasan_init() once shadow memory is ready. > + */ > +void __init kasan_init_generic(void) > +{ > + kasan_enable(); > + > + pr_info("KernelAddressSanitizer initialized (generic)\n"); > +} > + > /* > * All functions below always inlined so compiler could > * perform better optimizations in each of __asan_loadX/__assn_storeX > diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c > index 9a6927394b5..c8289a3feab 100644 > --- a/mm/kasan/hw_tags.c > +++ b/mm/kasan/hw_tags.c > @@ -45,13 +45,6 @@ static enum kasan_arg kasan_arg __ro_after_init; > static enum kasan_arg_mode kasan_arg_mode __ro_after_init; > static enum kasan_arg_vmalloc kasan_arg_vmalloc __initdata; > > -/* > - * Whether KASAN is enabled at all. > - * The value remains false until KASAN is initialized by kasan_init_hw_tags(). > - */ > -DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled); > -EXPORT_SYMBOL(kasan_flag_enabled); > - > /* > * Whether the selected mode is synchronous, asynchronous, or asymmetric. > * Defaults to KASAN_MODE_SYNC. > @@ -260,7 +253,7 @@ void __init kasan_init_hw_tags(void) > kasan_init_tags(); > > /* KASAN is now initialized, enable it. */ > - static_branch_enable(&kasan_flag_enabled); > + kasan_enable(); > This is obviously broken for the HW_TAGS case. kasan_enable() does nothing, and kasan_hw_tags_enabled() now always return true.