From: Petr Mladek <pmladek@suse.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org,
Masami Hiramatsu <mhiramat@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
live-patching@vger.kernel.org
Subject: Re: [PATCH 3/3 v7] livepatch: Use the default ftrace_ops instead of REGS when ARGS is available
Date: Thu, 19 Nov 2020 17:07:50 +0100 [thread overview]
Message-ID: <X7aYVgRa5uP8sAMM@alley> (raw)
In-Reply-To: <20201119091235.60be696e@gandalf.local.home>
On Thu 2020-11-19 09:12:35, Steven Rostedt wrote:
> On Thu, 19 Nov 2020 12:52:00 +0100
> Petr Mladek <pmladek@suse.com> wrote:
>
> > > #ifdef CONFIG_LIVEPATCH
> > > -static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
> > > +static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip)
> > > {
> > > + struct pt_regs *regs = ftrace_get_regs(fregs);
> >
> > Should we check for NULL pointer here?
>
> As mentioned in my last email. regs could have been NULL for the same
> reasons before this patch, and we didn't check it then. Why should we check
> it now?
>
> The ftrace_get_regs() only makes sure that a ftrace_ops that set
> FL_SAVE_REGS gets it, and those that did not, don't.
>
> But that's not entirely true either. If there's two callbacks to the same
> function, and one has FL_SAVE_REGS set, they both can have access to the
> regs (before and after this patch). It's just that the one that did not
> have FL_SAVE_REGS set, isn't guaranteed to have it.
Makes sense. Thanks for explanation. Feel free to use:
Acked-by: Petr Mladek <pmladek@suse.com>
I actually did review of all patches and they looked fine to me.
I just did not check all corner cases, assembly, and did not test
it, so I give it just my ack. I believe your testing ;-)
Best Regards,
Petr
prev parent reply other threads:[~2020-11-19 16:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20201113171811.288150055@goodmis.org>
2020-11-13 17:18 ` [PATCH 3/3 v7] livepatch: Use the default ftrace_ops instead of REGS when ARGS is available Steven Rostedt
2020-11-19 11:52 ` Petr Mladek
2020-11-19 14:12 ` Steven Rostedt
2020-11-19 16:07 ` Petr Mladek [this message]
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