linux-kernel - Re: [PATCH] arm: ftrace: fix dynamic ftrace with DEBUG_RODATA and !FRAME

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Message-ID: <20170318183323.5hmqt6yx6ja63kaa@debian>
Date:   Sat, 18 Mar 2017 19:33:23 +0100
From:   Rabin Vincent <rabin@....in>
To:     Abel Vesa <abelvesa@...ux.com>
Cc:     nicstange@...il.com, keescook@...omium.org,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Russell King <linux@...linux.org.uk>,
        Ingo Molnar <mingo@...hat.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm: ftrace: fix dynamic ftrace with DEBUG_RODATA and
 !FRAME_POINTER

On Wed, Mar 15, 2017 at 06:07:39PM +0000, Abel Vesa wrote:
> The support for dynamic ftrace with CONFIG_DEBUG_RODATA involves
> overriding the weak arch_ftrace_update_code() with a variant which makes
> the kernel text writable around the patching.
> 
> This override was however added under the CONFIG_OLD_MCOUNT ifdef, and
> CONFIG_OLD_MCOUNT is only enabled if frame pointers are enabled.
> 
> This leads to non-functional dynamic ftrace (ftrace triggers a
> WARN_ON()) when CONFIG_DEBUG_RODATA is enabled and CONFIG_FRAME_POINTER
> is not.
> 
> Move the override out of that ifdef and into the CONFIG_DYNAMIC_FTRACE
> ifdef where it belongs.
> 
> Fixes: 80d6b0c2eed2a ("ARM: mm: allow text and rodata sections to be read-only")
> 
> Suggested-by: Nicolai Stange <nicstange@...il.com>
> Suggested-by: Rabin Vincent <rabin@....in>
> Signed-off-by: Abel Vesa <abelvesa@...ux.com>

Acked-by: Rabin Vincent <rabin@....in>