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Date:   Wed, 23 Mar 2022 12:48:29 +0100
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Subject: Re: [PATCH v6 27/39] kasan, mm: only define ___GFP_SKIP_KASAN_POISON
 with HW_TAGS
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To:     andrey.konovalov@linux.dev,
        Andrew Morton <akpm@linux-foundation.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     Andrey Konovalov <andreyknvl@gmail.com>,
        Marco Elver <elver@google.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        kasan-dev@googlegroups.com, linux-mm@kvack.org,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        linux-arm-kernel@lists.infradead.org,
        Peter Collingbourne <pcc@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>
References: <cover.1643047180.git.andreyknvl@google.com>
 <44e5738a584c11801b2b8f1231898918efc8634a.1643047180.git.andreyknvl@google.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <44e5738a584c11801b2b8f1231898918efc8634a.1643047180.git.andreyknvl@google.com>
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On 1/24/22 19:05, andrey.konovalov@linux.dev wrote:
> From: Andrey Konovalov <andreyknvl@google.com>
> 
> Only define the ___GFP_SKIP_KASAN_POISON flag when CONFIG_KASAN_HW_TAGS
> is enabled.
> 
> This patch it not useful by itself, but it prepares the code for
> additions of new KASAN-specific GFP patches.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> 
> ---
> 
> Changes v3->v4:
> - This is a new patch.
> ---
>  include/linux/gfp.h            |  8 +++++++-
>  include/trace/events/mmflags.h | 12 +++++++++---
>  2 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 581a1f47b8a2..96f707931770 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -54,7 +54,11 @@ struct vm_area_struct;
>  #define ___GFP_THISNODE		0x200000u
>  #define ___GFP_ACCOUNT		0x400000u
>  #define ___GFP_ZEROTAGS		0x800000u
> +#ifdef CONFIG_KASAN_HW_TAGS
>  #define ___GFP_SKIP_KASAN_POISON	0x1000000u
> +#else
> +#define ___GFP_SKIP_KASAN_POISON	0
> +#endif
>  #ifdef CONFIG_LOCKDEP
>  #define ___GFP_NOLOCKDEP	0x2000000u
>  #else
> @@ -251,7 +255,9 @@ struct vm_area_struct;
>  #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
>  
>  /* Room for N __GFP_FOO bits */
> -#define __GFP_BITS_SHIFT (25 + IS_ENABLED(CONFIG_LOCKDEP))
> +#define __GFP_BITS_SHIFT (24 +					\
> +			  IS_ENABLED(CONFIG_KASAN_HW_TAGS) +	\
> +			  IS_ENABLED(CONFIG_LOCKDEP))

This breaks __GFP_NOLOCKDEP, see:
https://lore.kernel.org/all/YjoJ4CzB3yfWSV1F@linutronix.de/

>  #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
>  
>  /**
> diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
> index 116ed4d5d0f8..cb4520374e2c 100644
> --- a/include/trace/events/mmflags.h
> +++ b/include/trace/events/mmflags.h
> @@ -49,12 +49,18 @@
>  	{(unsigned long)__GFP_RECLAIM,		"__GFP_RECLAIM"},	\
>  	{(unsigned long)__GFP_DIRECT_RECLAIM,	"__GFP_DIRECT_RECLAIM"},\
>  	{(unsigned long)__GFP_KSWAPD_RECLAIM,	"__GFP_KSWAPD_RECLAIM"},\
> -	{(unsigned long)__GFP_ZEROTAGS,		"__GFP_ZEROTAGS"},	\
> -	{(unsigned long)__GFP_SKIP_KASAN_POISON,"__GFP_SKIP_KASAN_POISON"}\
> +	{(unsigned long)__GFP_ZEROTAGS,		"__GFP_ZEROTAGS"}	\
> +
> +#ifdef CONFIG_KASAN_HW_TAGS
> +#define __def_gfpflag_names_kasan					      \
> +	, {(unsigned long)__GFP_SKIP_KASAN_POISON, "__GFP_SKIP_KASAN_POISON"}
> +#else
> +#define __def_gfpflag_names_kasan
> +#endif
>  
>  #define show_gfp_flags(flags)						\
>  	(flags) ? __print_flags(flags, "|",				\
> -	__def_gfpflag_names						\
> +	__def_gfpflag_names __def_gfpflag_names_kasan			\
>  	) : "none"
>  
>  #ifdef CONFIG_MMU