linux-kernel - Re: [PATCH v3 0/3] ftrace: Introduce PERMANENT ftrace

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Date:   Wed, 16 Oct 2019 10:58:14 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     mingo@...hat.com, jpoimboe@...hat.com, jikos@...nel.org,
        pmladek@...e.com, joe.lawrence@...hat.com,
        linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
        shuah@...nel.org, kamalesh@...ux.vnet.ibm.com,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v3 0/3] ftrace: Introduce PERMANENT ftrace_ops flag

On Wed, 16 Oct 2019 13:33:12 +0200
Miroslav Benes <mbenes@...e.cz> wrote:

> Livepatch uses ftrace for redirection to new patched functions. It means
> that if ftrace is disabled, all live patched functions are disabled as
> well. Toggling global 'ftrace_enabled' sysctl thus affect it directly.
> It is not a problem per se, because only administrator can set sysctl
> values, but it still may be surprising.
> 
> Introduce PERMANENT ftrace_ops flag to amend this. If the
> FTRACE_OPS_FL_PERMANENT is set on any ftrace ops, the tracing cannot be
> disabled by disabling ftrace_enabled. Equally, a callback with the flag
> set cannot be registered if ftrace_enabled is disabled.
> 
> v2->v3:
> - ftrace_enabled explicitly set to true
> - selftest from Joe Lawrence (I just split it to two patches)
> - typo fix
> 
> v1->v2:
> - different logic, proposed by Joe Lawrence
> 
> Joe Lawrence (2):
>   selftests/livepatch: Make dynamic debug setup and restore generic
>   selftests/livepatch: Test interaction with ftrace_enabled
> 
> Miroslav Benes (1):
>   ftrace: Introduce PERMANENT ftrace_ops flag
> 

Would you like me to take all three patches through my tree?

-- Steve