linux-kernel - Re: [PATCH 4.19 12/87] arm/ftrace: Fix BE text poking

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Date:   Thu, 5 Mar 2020 14:49:57 +0100
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Dmitry Osipenko <digetx@...il.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 12/87] arm/ftrace: Fix BE text poking

Hi!

> From: Peter Zijlstra <peterz@...radead.org>
> 
> [ Upstream commit be993e44badc448add6a18d6f12b20615692c4c3 ]
> 
> The __patch_text() function already applies __opcode_to_mem_*(), so
> when __opcode_to_mem_*() is not the identity (BE*), it is applied
> twice, wrecking the instruction.
> 
> Fixes: 42e51f187f86 ("arm/ftrace: Use __patch_text()")

I don't see 42e51f187f86 anywhere. Mainline contains

commit 5a735583b764750726621b0396d03e4782911b77
Author: Peter Zijlstra <peterz@...radead.org>
Date:   Tue Oct 15 21:07:35 2019 +0200

    arm/ftrace: Use __patch_text()

But that one is not present in 4.19, so perhaps we should not need
this?

Best regards,
								Pavel

> Reported-by: Dmitry Osipenko <digetx@...il.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Tested-by: Dmitry Osipenko <digetx@...il.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  arch/arm/kernel/ftrace.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
> index ee673c09aa6c0..dd0215fb6fe23 100644
> --- a/arch/arm/kernel/ftrace.c
> +++ b/arch/arm/kernel/ftrace.c
> @@ -106,13 +106,10 @@ static int ftrace_modify_code(unsigned long pc, unsigned long old,
>  {
>  	unsigned long replaced;
>  
> -	if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
> +	if (IS_ENABLED(CONFIG_THUMB2_KERNEL))
>  		old = __opcode_to_mem_thumb32(old);
> -		new = __opcode_to_mem_thumb32(new);
> -	} else {
> +	else
>  		old = __opcode_to_mem_arm(old);
> -		new = __opcode_to_mem_arm(new);
> -	}
>  
>  	if (validate) {
>  		if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
> -- 
> 2.20.1
> 
> 

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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