linux-kernel - Re:Re: [PATCH] arm64/module: Support for patching modules during runtime

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Message-ID: <587b3c08.7e85.19898424fdb.Coremail.fanqincui@163.com>
Date: Mon, 11 Aug 2025 16:32:19 +0800 (CST)
From: fanqincui  <fanqincui@....com>
To: "Marc Zyngier" <maz@...nel.org>
Cc: "Will Deacon" <will@...nel.org>, catalin.marinas@....com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	"Fanqin Cui" <cuifq1@...natelecom.cn>, hanht2@...natelecom.cn
Subject: Re:Re: [PATCH] arm64/module: Support for patching modules during
 runtime


Hi marc,
The callback function is designed by the developer. Developers need
to use the callback function to patch their own module code. Under
this premise, developers are responsible for providing the correct
callback function.
A correct callback function implementation does not require further
patching. Furthermore, the callback itself must be executable. If the
callback function has problems, the module's functionality will be affected.

Fanqin












At 2025-08-11 16:01:43, "Marc Zyngier" <maz@...nel.org> wrote:
>On Mon, 11 Aug 2025 08:37:32 +0100,
>fanqincui <fanqincui@....com> wrote:
>> 
>> Hi will,
>> Yes, you are right. The alternative callback function lives inside the module.
>> This callback function is actually similar to kvm_update_va_mask in KVM;
>> 
>> The module's callback function calculates some values based on
>> the current CPU features and then performs the replacement.
>> 
>> The .text.alternative_cb section is actually marked as SHF_EXECINSTR | SHF_ALLOC
>> during compilation, so intersections() includes this section and sets it as executable later.
>
>I'm worried there is a chicken-and-egg problem here. What if the
>callback itself requires patching via some other alternative? Is there
>a guarantee that this always performed in the correct order?
>
>	M.
>
>-- 
>Without deviation from the norm, progress is not possible.