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From: Steven Rostedt <rostedt@goodmis.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	davem@davemloft.net, daniel@iogearbox.net, peterz@infradead.org,
	x86@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org,
	kernel-team@fb.com, Thomas Gleixner <tglx@linutronix.de>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH bpf-next 0/7] Introduce BPF trampoline
Date: Tue, 5 Nov 2019 12:26:29 -0500	[thread overview]
Message-ID: <20191105122629.29aecc69@grimm.local.home> (raw)
In-Reply-To: <20191105162801.sffoqe2yedrrplnn@ast-mbp.dhcp.thefacebook.com>

On Tue, 5 Nov 2019 08:28:02 -0800
Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:

> On Tue, Nov 05, 2019 at 11:00:28AM -0500, Steven Rostedt wrote:
> > On Tue, 5 Nov 2019 07:47:11 -0800
> > Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
> >   
> > > > If you have to wait you may need to wait. The Linux kernel isn't
> > > > something that is suppose to put in temporary hacks, just to satisfy
> > > > someone's deadline.    
> > > 
> > > Ok. I will switch to text_poke and will make it hack free.
> > > ftrace mechanisms are being replaced by text_poke anyway.  
> > 
> > I see that Facebook now owns Linux.  
> 
> huh?

Sorry, I'm a bit grumpy. I've been non stop for over a week (7 days of
conferences), and I'm still not done traveling yet. :-p


> 
> > Peter's text poke patches most likely not be ready for the next
> > merge window either. Don't you require them?  
> 
> nope.
> But I strongly support them. ftrace->text_poke + static_call + nop2
> are all great improvements.
> I'd really like to see them landing in this merge window.
> 
> > The database of function nops are part of the ftrace mechanisms which
> > are not part of text poke, and there's strong accounting associated to
> > them which allows the user to see how their kernel is modified.   
> 
> I guess the part that wasn't obvious from commit log of bpf trampoline patches
> is that they don't care about nops and ftrace recording of nops. bpf trampoline
> will work even if there are no nops in front of the function. It will work when
> CONFIG_HAVE_FENTRY is off.

I'm guessing it will use kprobes (or optimized probes). I haven't had a
chance to look at your patches.

I still think using the register_ftrace_direct() will be cleaner (as it
is built on top of code that's been in the kernel for a decade).
Perhaps we can make it work even without the full ftrace code.

-- Steve

  reply	other threads:[~2019-11-05 17:26 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-02 22:00 [PATCH bpf-next 0/7] Introduce BPF trampoline Alexei Starovoitov
2019-11-02 22:00 ` [PATCH bpf-next 1/7] bpf, ftrace: temporary workaround Alexei Starovoitov
2019-11-02 22:00 ` [PATCH bpf-next 2/7] bpf: refactor x86 JIT into helpers Alexei Starovoitov
2019-11-02 22:00 ` [PATCH bpf-next 3/7] bpf: Introduce BPF trampoline Alexei Starovoitov
2019-11-05 19:51   ` Andrii Nakryiko
2019-11-02 22:00 ` [PATCH bpf-next 4/7] libbpf: Add support to attach to fentry/fexit tracing progs Alexei Starovoitov
2019-11-05 21:17   ` Andrii Nakryiko
2019-11-05 23:17     ` Alexei Starovoitov
2019-11-02 22:00 ` [PATCH bpf-next 5/7] selftest/bpf: Simple test for fentry/fexit Alexei Starovoitov
2019-11-05 21:37   ` Andrii Nakryiko
2019-11-02 22:00 ` [PATCH bpf-next 6/7] bpf: Add kernel test functions for fentry testing Alexei Starovoitov
2019-11-02 22:00 ` [PATCH bpf-next 7/7] selftests/bpf: Add test for BPF trampoline Alexei Starovoitov
2019-11-05 21:50   ` Andrii Nakryiko
2019-11-05 14:31 ` [PATCH bpf-next 0/7] Introduce " Alexei Starovoitov
2019-11-05 15:40   ` Steven Rostedt
2019-11-05 15:47     ` Alexei Starovoitov
2019-11-05 16:00       ` Steven Rostedt
2019-11-05 16:28         ` Alexei Starovoitov
2019-11-05 17:26           ` Steven Rostedt [this message]
2019-11-05 17:59             ` Alexei Starovoitov

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