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

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Date:   Mon, 6 Jun 2022 22:57:02 +0000
From:   Song Liu <songliubraving@...com>
To:     Steven Rostedt <rostedt@...dmis.org>
CC:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Kernel Team <Kernel-team@...com>, Jiri Olsa <jolsa@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Song Liu <song@...nel.org>
Subject: Re: [PATCH v2 bpf-next 0/5] ftrace: host klp and bpf trampoline
 together

Hi Steven, 

> On Jun 2, 2022, at 12:37 PM, 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.

Could you please share your comments on this set? 

Thanks!
Song

> 
> 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