linux-kernel - [RFC PATCH v2 0/6] bpf: fprobe: rethook: Use ftrace_regs instead of pt

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Date:   Mon,  7 Aug 2023 15:48:24 +0900
From:   "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Florent Revest <revest@...omium.org>
Cc:     linux-trace-kernel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        bpf <bpf@...r.kernel.org>, Sven Schnelle <svens@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alan Maguire <alan.maguire@...cle.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [RFC PATCH v2 0/6] bpf: fprobe: rethook: Use ftrace_regs instead of pt_regs

Hi,

Here is the 2nd version of RFC series to use ftrace_regs instead of pt_regs.
But this includes the generic part and minimum modifications of arch
dependent code. (e.g. not including rethook for arm64.) This series is based
on the discussion at

https://lore.kernel.org/all/20230801112036.0d4ee60d@gandalf.local.home/

This version includes 1 patch to expose ftrace_regs. so

 - Simply replace pt_regs in fprobe_entry_handler with ftrace_regs.
 - Expose ftrace_regs even if CONFIG_FUNCTION_TRACER=n.
 - Replace pt_regs in rethook and fprobe_exit_handler with ftrace_regs. This
   introduce a new HAVE_PT_REGS_COMPAT_FTRACE_REGS which means ftrace_regs is
   just a wrapper of pt_regs (except for arm64, other architectures do this)
 - Update fprobe-events to use ftrace_regs natively.
 - Introduce ftrace_partial_regs(). (This changes ARM64 which needs a custom
   implementation)
 - Update bpf multi-kprobe handler use ftrace_partial_regs().

Florent, feel free to add your rethook for arm64, but please do not remove
kretprobe trampoline yet. It is another discussion point. We may be possible
to use ftrace_regs for kretprobe by ftrace_partial_regs() but kretprobe
allows nest probe. (maybe we can skip that case?)

This series can also be found below branch.

https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/log/?h=topic/fprobe-ftrace-regs

Thank you,

---

Masami Hiramatsu (Google) (6):
      fprobe: Use fprobe_regs in fprobe entry handler
      tracing: Expose ftrace_regs regardless of CONFIG_FUNCTION_TRACER
      fprobe: rethook: Use fprobe_regs in fprobe exit handler and rethook
      tracing/fprobe: Enable fprobe events with CONFIG_DYNAMIC_FTRACE_WITH_ARGS
      ftrace: Add ftrace_partial_regs() for converting ftrace_regs to pt_regs
      bpf: Enable kprobe_multi feature if CONFIG_FPROBE is enabled


 arch/Kconfig                    |    1 +
 arch/arm64/include/asm/ftrace.h |   11 ++++++
 arch/loongarch/Kconfig          |    1 +
 arch/s390/Kconfig               |    1 +
 arch/x86/Kconfig                |    1 +
 arch/x86/kernel/rethook.c       |    9 +++--
 include/linux/fprobe.h          |    4 +-
 include/linux/ftrace.h          |   56 ++++++++++++++++++-----------
 include/linux/rethook.h         |   11 +++---
 kernel/kprobes.c                |    9 ++++-
 kernel/trace/Kconfig            |    9 ++++-
 kernel/trace/bpf_trace.c        |   14 +++++--
 kernel/trace/fprobe.c           |    8 ++--
 kernel/trace/rethook.c          |   16 ++++----
 kernel/trace/trace_fprobe.c     |   76 ++++++++++++++++++++++++---------------
 kernel/trace/trace_probe_tmpl.h |    2 +
 lib/test_fprobe.c               |   10 +++--
 samples/fprobe/fprobe_example.c |    4 +-
 18 files changed, 154 insertions(+), 89 deletions(-)

--
Masami Hiramatsu (Google) <mhiramat@...nel.org>