linux-kernel - Re: [PATCH RFC 07/10] kfence, kmemleak: make KFENCE compatible with KMEMLEAK

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Date:   Tue, 8 Sep 2020 12:53:17 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Marco Elver <elver@...gle.com>
Cc:     glider@...gle.com, akpm@...ux-foundation.org, cl@...ux.com,
        rientjes@...gle.com, iamjoonsoo.kim@....com, mark.rutland@....com,
        penberg@...nel.org, hpa@...or.com, paulmck@...nel.org,
        andreyknvl@...gle.com, aryabinin@...tuozzo.com, luto@...nel.org,
        bp@...en8.de, dave.hansen@...ux.intel.com, dvyukov@...gle.com,
        edumazet@...gle.com, gregkh@...uxfoundation.org, mingo@...hat.com,
        jannh@...gle.com, corbet@....net, keescook@...omium.org,
        peterz@...radead.org, cai@....pw, tglx@...utronix.de,
        will@...nel.org, x86@...nel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org
Subject: Re: [PATCH RFC 07/10] kfence, kmemleak: make KFENCE compatible with
 KMEMLEAK

On Mon, Sep 07, 2020 at 03:40:52PM +0200, Marco Elver wrote:
> From: Alexander Potapenko <glider@...gle.com>
> 
> Add compatibility with KMEMLEAK, by making KMEMLEAK aware of the KFENCE
> memory pool. This allows building debug kernels with both enabled, which
> also helped in debugging KFENCE.
> 
> Co-developed-by: Marco Elver <elver@...gle.com>
> Signed-off-by: Marco Elver <elver@...gle.com>
> Signed-off-by: Alexander Potapenko <glider@...gle.com>
> ---
>  mm/kmemleak.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index 5e252d91eb14..2809c25c0a88 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -97,6 +97,7 @@
>  #include <linux/atomic.h>
>  
>  #include <linux/kasan.h>
> +#include <linux/kfence.h>
>  #include <linux/kmemleak.h>
>  #include <linux/memory_hotplug.h>
>  
> @@ -1946,8 +1947,18 @@ void __init kmemleak_init(void)
>  	/* register the data/bss sections */
>  	create_object((unsigned long)_sdata, _edata - _sdata,
>  		      KMEMLEAK_GREY, GFP_ATOMIC);
> +#if defined(CONFIG_KFENCE) && defined(CONFIG_HAVE_ARCH_KFENCE_STATIC_POOL)
> +	/* KFENCE objects are located in .bss, which may confuse kmemleak. Skip them. */
> +	create_object((unsigned long)__bss_start, __kfence_pool - __bss_start,
> +		      KMEMLEAK_GREY, GFP_ATOMIC);
> +	create_object((unsigned long)__kfence_pool + KFENCE_POOL_SIZE,
> +		      __bss_stop - (__kfence_pool + KFENCE_POOL_SIZE),
> +		      KMEMLEAK_GREY, GFP_ATOMIC);
> +#else
>  	create_object((unsigned long)__bss_start, __bss_stop - __bss_start,
>  		      KMEMLEAK_GREY, GFP_ATOMIC);
> +#endif

Could you instead do:

#if defined(CONFIG_KFENCE) && defined(CONFIG_HAVE_ARCH_KFENCE_STATIC_POOL)
	delete_object_part((unsigned long)__kfence_pool, KFENCE_POOL_SIZE);
#endif

-- 
Catalin