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

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Message-ID: <86zfc68exk.wl-maz@kernel.org>
Date: Mon, 11 Aug 2025 09:01:43 +0100
From: Marc Zyngier <maz@...nel.org>
To: fanqincui  <fanqincui@....com>
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: [PATCH] arm64/module: Support for patching modules during runtime

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.