linux-kernel - Re: [RFC PATCH] mm/kfence: Introduce kernel parameter for selective usage of kfence.

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Message-ID: <6a899346-f9b1-dc3a-2da0-f3271c85327c@oracle.com>
Date:   Thu, 28 Jul 2022 10:51:59 +1000
From:   Imran Khan <imran.f.khan@...cle.com>
To:     Randy Dunlap <rdunlap@...radead.org>, glider@...gle.com,
        elver@...gle.com, dvyukov@...gle.com, cl@...ux.com,
        penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, vbabka@...e.cz,
        roman.gushchin@...ux.dev, 42.hyeyoo@...il.com, corbet@....net
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org
Subject: Re: [RFC PATCH] mm/kfence: Introduce kernel parameter for selective
 usage of kfence.

Hello Randy,
Thanks for your review.

On 28/7/22 10:00 am, Randy Dunlap wrote:
> Hi--
> 
> On 7/27/22 16:42, Imran Khan wrote:
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index 98e5cb91faab..d66f555df7ba 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -5553,6 +5553,11 @@
>>  			last alloc / free. For more information see
>>  			Documentation/mm/slub.rst.
>>  
>> +	slub_kfence[=slabs][,slabs]]...]	[MM, SLUB]
> 
> I suppose that 'slabs' are by name?
> How can the names be found?  via 'slabinfo -l' or 'ls /sys/kernel/slab/' ?
> 
> 
Yes 'slabs' are by name and names can be obtained from slabinfo or sysfs or
using kmem -s on a vmcore. As it is a boot time option user needs to be aware of
slab name just like when someone uses slub_debug.

> It seems to me that the boot option should be listed as s/slabs/slab/.
> I.e., one uses 'comma' to list multiple slabs.
> Or is there a way for multiple slabs to be entered without commas?
> 

Yes, 'slabs' is a typo above, it should be 'slab'. The name of the slabs will be
specified as a comma separated list for example:
slub_kfence=kmalloc-*,dentry,task_struct.

I will make s/slabs/slab change in next version once I have gathered some more
feedbacks.

thanks
-- Imran