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Date:   Thu, 10 Jan 2019 11:54:01 +0900
From:   Masami Hiramatsu <>
To:     Ingo Molnar <>
Cc:     Masami Hiramatsu <>,,
        Mathieu Desnoyers <>,
        linux-kernel <>,
        Andrea Righi <>,
        Steven Rostedt <>,
Subject: [PATCH 0/9] kprobes: Fix and improve blacklist symbols


Here is a series of kprobes blacklist bugfix and improvements mainly
on x86 (since I started testing on qemu-x86).

This has been started from discussion about KPROBE_ENENTS_ON_NOTRACE
configuration. I tried to find notrace functions which can cause kernel
crash with kprobes using following script.


cat notrace_functions | while read f ; do
  if echo p:event$i $f >> /sys/kernel/debug/tracing/kprobe_events; then
     echo "Probing on $f"
     echo 1 > /sys/kernel/debug/tracing/events/kprobes/event$i/enable 

And I found several functions which must be blacklisted.
 - optprobe template code, which is just a template code and
   never be executed. Moreover, since it can be copied and
   reused, if we probe it, it modifies the template code and
   can cause a crash. ([1/9][2/9])
 - functions which is called before kprobe_int3_handler()
   handles kprobes. This can cause a breakpoint recursion. ([3/9])
 - IRQ entry text, which should not be probed since register/pagetable
   status has not been stable at that point. ([4/9])
 - Suffixed symbols, like .constprop, .part etc. Those suffixed
   symbols never be blacklisted even if the non-suffixed version
   has been blacklisted. ([5/9])
 - hardirq tracer also works before int3 handling. ([6/9])
 - preempt_check debug function also is involved in int3 handling.
 - RCU debug routine is also called before kprobe_int3_handler().
 - Some lockdep functions are also involved in int3 handling.

Of course there still may be some functions which can be called
by configuration change, I'll continue to test it.

Thank you,


Masami Hiramatsu (9):
      x86/kprobes: Prohibit probing on optprobe template code
      x86/kprobes: Move trampoline code into RODATA
      x86/kprobes: Prohibit probing on functions before kprobe_int3_handler()
      x86/kprobes: Prohibit probing on IRQ handlers directly
      kprobes: Search non-suffixed symbol in blacklist
      kprobes: Prohibit probing on hardirq tracers
      kprobes: Prohibit probing on preempt_check debug functions
      kprobes: Prohibit probing on RCU debug routine
      kprobes: Prohibit probing on lockdep functions

 arch/x86/kernel/alternative.c   |    3 ++-
 arch/x86/kernel/ftrace.c        |    3 ++-
 arch/x86/kernel/kprobes/core.c  |    7 +++++++
 arch/x86/kernel/kprobes/opt.c   |    4 ++--
 arch/x86/kernel/traps.c         |    1 +
 kernel/kprobes.c                |   21 ++++++++++++++++++++-
 kernel/locking/lockdep.c        |    7 ++++++-
 kernel/rcu/tree.c               |    2 ++
 kernel/rcu/update.c             |    2 ++
 kernel/trace/trace_irqsoff.c    |    9 +++++++--
 kernel/trace/trace_preemptirq.c |    5 +++++
 lib/smp_processor_id.c          |    7 +++++--
 12 files changed, 61 insertions(+), 10 deletions(-)

Masami Hiramatsu (Linaro) <>

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