linux-kernel - Re: [PATCH] livepatch: Add using attribute to klp

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Message-ID: <alpine.LSU.2.21.2407191402500.24282@pobox.suse.cz>
Date: Fri, 19 Jul 2024 14:09:12 +0200 (CEST)
From: Miroslav Benes <mbenes@...e.cz>
To: "zhangyongde.zyd" <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: Add using attribute to klp_func for using
 func show

Hi,

On Thu, 18 Jul 2024, zhangyongde.zyd wrote:

> From: Wardenjohn <zhangwarden@...il.com>
> 
> One system may contains more than one livepatch module. We can see
> which patch is enabled. If some patches applied to one system
> modifing the same function, livepatch will use the function enabled
> on top of the function stack. However, we can not excatly know
> which function of which patch is now enabling.
> 
> This patch introduce one sysfs attribute of "using" to klp_func.
> For example, if there are serval patches  make changes to function
> "meminfo_proc_show", the attribute "enabled" of all the patch is 1.
> With this attribute, we can easily know the version enabling belongs
> to which patch.
> 
> cat /sys/kernel/livepatch/<patch1>/<object1>/<function1,sympos>/using -> 0
> means that the function1 of patch1 is disabled.
> 
> cat /sys/kernel/livepatch/<patchN>/<object1>/<function1,sympos>/using -> 1
> means that the function1 of patchN is enabled.

is this always correct though? See the logic in klp_ftrace_handler(). If 
there is a transition running, it is a little bit more complicated.

Miroslav