linux-kernel - Re: [PATCH v2 bpf-next 0/5] ftrace: host klp and bpf trampoline together

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Message-ID: <20220711195552.22c3a4be@gandalf.local.home>
Date:   Mon, 11 Jul 2022 19:55:52 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Song Liu <song@...nel.org>
Cc:     <netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <ast@...nel.org>,
        <daniel@...earbox.net>, <andrii@...nel.org>, <kernel-team@...com>,
        <jolsa@...nel.org>, <mhiramat@...nel.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        live-patching@...r.kernel.org
Subject: Re: [PATCH v2 bpf-next 0/5] ftrace: host klp and bpf trampoline
 together

I just realized that none of the live kernel patching folks are Cc'd on
this thread. I think they will care much more about this than I do.

-- Steve


On Thu, 2 Jun 2022 12:37:01 -0700
Song Liu <song@...nel.org> wrote:

> Changes v1 => v2:
> 1. Fix build errors for different config. (kernel test robot)
> 
> Kernel Live Patch (livepatch, or klp) and bpf trampoline are important
> features for modern systems. This set allows the two to work on the same
> kernel function as the same time.
> 
> live patch uses ftrace with IPMODIFY, while bpf trampoline use direct
> ftrace. Existing policy does not allow the two to attach to the same kernel
> function. This is changed by fine tuning ftrace IPMODIFY policy, and allows
> one non-DIRECT IPMODIFY ftrace_ops and one non-IPMODIFY DIRECT ftrace_ops
> on the same kernel function at the same time. Please see 3/5 for more
> details on this.
> 
> Note that, one of the constraint here is to let bpf trampoline use direct
> call when it is not working on the same function as live patch. This is
> achieved by allowing ftrace code to ask bpf trampoline to make changes.
> 
> Jiri Olsa (1):
>   bpf, x64: Allow to use caller address from stack
> 
> Song Liu (4):
>   ftrace: allow customized flags for ftrace_direct_multi ftrace_ops
>   ftrace: add modify_ftrace_direct_multi_nolock
>   ftrace: introduce FTRACE_OPS_FL_SHARE_IPMODIFY
>   bpf: trampoline: support FTRACE_OPS_FL_SHARE_IPMODIFY
> 
>  arch/x86/net/bpf_jit_comp.c |  13 +-
>  include/linux/bpf.h         |   8 ++
>  include/linux/ftrace.h      |  79 +++++++++++
>  kernel/bpf/trampoline.c     | 109 +++++++++++++--
>  kernel/trace/ftrace.c       | 269 +++++++++++++++++++++++++++++++-----
>  5 files changed, 424 insertions(+), 54 deletions(-)
> 
> --
> 2.30.2