linux-kernel - Re: [PATCH v2 11/20] x86/jump-label: remove support for custom poker

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Message-ID: <20190211183749.GO19618@zn.tnic>
Date:   Mon, 11 Feb 2019 19:37:50 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc:     Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org, hpa@...or.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Nadav Amit <nadav.amit@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>, linux_dti@...oud.com,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, akpm@...ux-foundation.org,
        kernel-hardening@...ts.openwall.com, linux-mm@...ck.org,
        will.deacon@....com, ard.biesheuvel@...aro.org,
        kristen@...ux.intel.com, deneen.t.dock@...el.com,
        Nadav Amit <namit@...are.com>,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH v2 11/20] x86/jump-label: remove support for custom poker

On Mon, Jan 28, 2019 at 04:34:13PM -0800, Rick Edgecombe wrote:
> From: Nadav Amit <namit@...are.com>
> 
> There are only two types of poking: early and breakpoint based. The use
> of a function pointer to perform poking complicates the code and is
> probably inefficient due to the use of indirect branches.
> 
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Nadav Amit <namit@...are.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
> ---
>  arch/x86/kernel/jump_label.c | 24 ++++++++----------------
>  1 file changed, 8 insertions(+), 16 deletions(-)

...

> @@ -80,16 +71,17 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
>  		bug_at((void *)jump_entry_code(entry), line);
>  
>  	/*
> -	 * Make text_poke_bp() a default fallback poker.
> +	 * As long as we're UP and not yet marked RO, we can use
> +	 * text_poke_early; SYSTEM_BOOTING guarantees both, as we switch to
> +	 * SYSTEM_SCHEDULING before going either.

s/going/doing/ ?

-- 
Regards/Gruss,
    Boris.

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