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

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Date:   Wed, 16 Oct 2019 17:01:11 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Steven Rostedt <rostedt@...dmis.org>
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, Steven Rostedt wrote:

> 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?

I think that would be the easiest, yes.

Thanks
Miroslav