linux-kernel - Re: [PATCH v1 5/5] powerpc/ftrace: Add support for livepatch to PPC32

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Date:   Mon, 8 Nov 2021 11:01:32 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Naveen N . Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        live-patching@...r.kernel.org
Subject: Re: [PATCH v1 5/5] powerpc/ftrace: Add support for livepatch to PPC32

On Thu 2021-10-28 14:24:05, Christophe Leroy wrote:
> This is heavily copied from PPC64. Not much to say about it.
> 
> Livepatch sample modules all work.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
> diff --git a/arch/powerpc/include/asm/livepatch.h b/arch/powerpc/include/asm/livepatch.h
> index 4fe018cc207b..daf24d837241 100644
> --- a/arch/powerpc/include/asm/livepatch.h
> +++ b/arch/powerpc/include/asm/livepatch.h
> @@ -23,8 +23,8 @@ static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip)
>  static inline unsigned long klp_get_ftrace_location(unsigned long faddr)
>  {
>  	/*
> -	 * Live patch works only with -mprofile-kernel on PPC. In this case,
> -	 * the ftrace location is always within the first 16 bytes.
> +	 * Live patch works on PPC32 and only with -mprofile-kernel on PPC64. In
> +	 * both cases, the ftrace location is always within the first 16 bytes.

Nit: I had some problems to parse it. I wonder if the following is
better:

	 * Live patch works on PPC32 out of box and on PPC64 only with
	 * -mprofile-kernel. In both cases, the ftrace location is always
	 * within the first 16 bytes.


>  	 */
>  	return ftrace_location_range(faddr, faddr + 16);
>  }

Best Regards,
Petr