linux-kernel - Re: [PATCH] livepatch: introduce klp

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Date: Mon, 20 May 2024 08:46:24 +0200 (CEST)
From: Miroslav Benes <mbenes@...e.cz>
To: Wardenjohn <zhangwarden@...il.com>
cc: jpoimboe@...nel.org, jikos@...nel.org, pmladek@...e.com, 
    joe.lawrence@...hat.com, live-patching@...r.kernel.org, 
    linux-kernel@...r.kernel.org
Subject: Re: [PATCH] livepatch: introduce klp_func called interface

Hi,

On Mon, 20 May 2024, Wardenjohn wrote:

> Livepatch module usually used to modify kernel functions.
> If the patched function have bug, it may cause serious result
> such as kernel crash.
> 
> This is a kobject attribute of klp_func. Sysfs interface named
>  "called" is introduced to livepatch which will be set as true
> if the patched function is called.
> 
> /sys/kernel/livepatch/<patch>/<object>/<function,sympos>/called
> 
> This value "called" is quite necessary for kernel stability
> assurance for livepatching module of a running system.
> Testing process is important before a livepatch module apply to
> a production system. With this interface, testing process can
> easily find out which function is successfully called.
> Any testing process can make sure they have successfully cover
> all the patched function that changed with the help of this interface.

Even easier is to use the existing tracing infrastructure in the kernel 
(ftrace for example) to track the new function. You can obtain much more 
information with that than the new attribute provides.

Regards,
Miroslav