linux-kernel - Re: [DRAFT] mm/kprobes: Add generic kprobe_fault

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Message-ID: <8a5eb5d5-32f0-01cd-b2fe-890ebb98395b@roeck-us.net>
Date:   Wed, 3 Jul 2019 05:59:01 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     akpm@...ux-foundation.org
Subject: Re: [DRAFT] mm/kprobes: Add generic kprobe_fault_handler() fallback
 definition

On 7/2/19 10:35 PM, Anshuman Khandual wrote:
> 
> 
> On 07/01/2019 06:58 PM, Guenter Roeck wrote:
>> On 7/1/19 2:35 AM, Anshuman Khandual wrote:
>>> Architectures like parisc enable CONFIG_KROBES without having a definition
>>> for kprobe_fault_handler() which results in a build failure. Arch needs to
>>> provide kprobe_fault_handler() as it is platform specific and cannot have
>>> a generic working alternative. But in the event when platform lacks such a
>>> definition there needs to be a fallback.
>>>
>>> This adds a stub kprobe_fault_handler() definition which not only prevents
>>> a build failure but also makes sure that kprobe_page_fault() if called will
>>> always return negative in absence of a sane platform specific alternative.
>>>
>>> While here wrap kprobe_page_fault() in CONFIG_KPROBES. This enables stud
>>> definitions for generic kporbe_fault_handler() and kprobes_built_in() can
>>> just be dropped. Only on x86 it needs to be added back locally as it gets
>>> used in a !CONFIG_KPROBES function do_general_protection().
>>>
>>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>>> ---
>>> I am planning to go with approach unless we just want to implement a stub
>>> definition for parisc to get around the build problem for now.
>>>
>>> Hello Guenter,
>>>
>>> Could you please test this in your parisc setup. Thank you.
>>>
>>
>> With this patch applied on top of next-20190628, parisc:allmodconfig builds
>> correctly. I scheduled a full build for tonight for all architectures.
> 
> How did that come along ? Did this pass all build tests ?
> 

Let's say it didn't find any failures related to this patch. I built on top of
next-20190701 which was quite badly broken for other reasons. Unfortunately,
next-20190702 is much worse, so retesting would not add any value at this time.
I'd say go for it.

Guenter