linux-kernel - Re: [PATCH 06/11] x86/alternative: Simplify callthunk patching

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Message-ID: <20250207172357.ycl7rajhjqwdn544@jpoimboe>
Date: Fri, 7 Feb 2025 09:23:57 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, alyssa.milburn@...el.com,
	scott.d.constable@...el.com, joao@...rdrivepizza.com,
	andrew.cooper3@...rix.com, jose.marchesi@...cle.com,
	hjl.tools@...il.com, ndesaulniers@...gle.com,
	samitolvanen@...gle.com, nathan@...nel.org, ojeda@...nel.org,
	kees@...nel.org, alexei.starovoitov@...il.com, mhiramat@...nel.org
Subject: Re: [PATCH 06/11] x86/alternative: Simplify callthunk patching

On Fri, Feb 07, 2025 at 01:15:35PM +0100, Peter Zijlstra wrote:
> +++ b/arch/x86/kernel/alternative.c
> @@ -1697,14 +1697,14 @@ void __init alternative_instructions(voi
>  	apply_retpolines(__retpoline_sites, __retpoline_sites_end);
>  	apply_returns(__return_sites, __return_sites_end);
>  
> -	apply_alternatives(__alt_instructions, __alt_instructions_end);
> -
>  	/*
> -	 * Now all calls are established. Apply the call thunks if
> -	 * required.
> +	 * Adjust all CALL instructions to point to func()-10, including
> +	 * those in .altinstr_replacement.

Clarify 10 is hex: "func()-0x10" ?

-- 
Josh