linux-kernel - Re: [PATCH v4 02/10] x86/jump_label: Use text_poke

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Date:   Mon, 12 Nov 2018 20:12:42 +0000
From:   Nadav Amit <namit@...are.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v4 02/10] x86/jump_label: Use text_poke_early() during
 early init

Peter,

I have put you as a “Co-Developed-by”, since the patch ended up as being the
single line that you wrote in the correspondence of the previous version.

I would therefore need to ask for your signed-off-by.

Regards,
Nadav

From: Nadav Amit
Sent: November 10, 2018 at 11:17:24 PM GMT
> To: Ingo Molnar <mingo@...hat.com>
> Cc: linux-kernel@...r.kernel.org>, x86@...nel.org>, H. Peter Anvin <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, Nadav Amit <namit@...are.com>, Andy Lutomirski <luto@...nel.org>, Kees Cook <keescook@...omium.org>, Dave Hansen <dave.hansen@...el.com>, Masami Hiramatsu <mhiramat@...nel.org>
> Subject: [PATCH v4 02/10] x86/jump_label: Use text_poke_early() during early init
> 
> 
> There is no apparent reason not to use text_poke_early() while we are
> during early-init and we do not patch code that might be on the stack
> (i.e., we'll return to the middle of the patched code). This appears to
> be the case of jump-labels, so do so.
> 
> This is required for the next patches that would set a temporary mm for
> patching, which is initialized after some static-keys are
> enabled/disabled.
> 
> 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>
> Co-Developed-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Nadav Amit <namit@...are.com>
> ---
> arch/x86/kernel/jump_label.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
> index aac0c1f7e354..ed5fe274a7d8 100644
> --- a/arch/x86/kernel/jump_label.c
> +++ b/arch/x86/kernel/jump_label.c
> @@ -52,7 +52,12 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
> 	jmp.offset = jump_entry_target(entry) -
> 		     (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
> 
> -	if (early_boot_irqs_disabled)
> +	/*
> +	 * 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.
> +	 */
> +	if (system_state == SYSTEM_BOOTING)
> 		poker = text_poke_early;
> 
> 	if (type == JUMP_LABEL_JMP) {
> -- 
> 2.17.1