linux-kernel - Re: [PATCH v5 2/7] mm, kasan: SLAB support

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Message-ID: <CAG_fn=UFB3UYg0-uw4TUJvuvu9ZkqqTKG4enMFMXyWC-q65SeA@mail.gmail.com>
Date:	Fri, 11 Mar 2016 14:05:45 +0100
From:	Alexander Potapenko <glider@...gle.com>
To:	Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc:	Andrey Konovalov <adech.fo@...il.com>,
	Christoph Lameter <cl@...ux.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	JoonSoo Kim <js1304@...il.com>,
	Kostya Serebryany <kcc@...gle.com>,
	kasan-dev <kasan-dev@...glegroups.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v5 2/7] mm, kasan: SLAB support

On Fri, Mar 11, 2016 at 12:47 PM, Andrey Ryabinin
<ryabinin.a.a@...il.com> wrote:
> 2016-03-09 14:05 GMT+03:00 Alexander Potapenko <glider@...gle.com>:
>
>> +struct kasan_track {
>> +       u64 cpu : 6;                    /* for NR_CPUS = 64 */
>
> What about NR_CPUS > 64 ?
After a discussion with Dmitry we've decided to drop |cpu| and |when|
at all, as they do not actually help debugging.
This way we'll make kasan_track only 8 bytes (4 bytes for PID, 4 bytes
for stack handle).
Then the meta structures will be smaller and have nice alignment:

struct kasan_track {
        u32 pid;
        depot_stack_handle_t stack;
};

struct kasan_alloc_meta {
        struct kasan_track track;
        u32 state : 2;  /* enum kasan_state */
        u32 alloc_size : 30;
        u32 reserved;  /* we can use it to store an additional stack
handle, e.g. for debugging RCU */
};

struct kasan_free_meta {
        /* This field is used while the object is in the quarantine.
         * Otherwise it might be used for the allocator freelist.
         */
        void **quarantine_link;
        struct kasan_track track;
};


>> +       u64 pid : 16;                   /* 65536 processes */
>> +       u64 when : 42;                  /* ~140 years */
>> +};
>> +



-- 
Alexander Potapenko
Software Engineer

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