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Date:   Wed, 04 Sep 2019 14:43:26 +0530
From:   "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Subject: Re: [PATCH -tip v2] kprobes: Prohibit probing on BUG() and WARN()
 address
To:     Masami Hiramatsu <mhiramat@kernel.org>,
        Ingo Molnar <mingo@kernel.org>
Cc:     Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
        "David S . Miller" <davem@davemloft.net>,
        linux-kernel@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>
References: <156750890133.19112.3393666300746167111.stgit@devnote2>
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Masami Hiramatsu wrote:
> Since BUG() and WARN() may use a trap (e.g. UD2 on x86) to
> get the address where the BUG() has occurred, kprobes can not
> do single-step out-of-line that instruction. So prohibit
> probing on such address.
> 
> Without this fix, if someone put a kprobe on WARN(), the
> kernel will crash with invalid opcode error instead of
> outputing warning message, because kernel can not find
> correct bug address.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>   Changes in v2:
>    - Add find_bug() stub function for !CONFIG_GENERIC_BUG
>    - Cast the p->addr to unsigned long.
> ---
>  include/linux/bug.h |    5 +++++
>  kernel/kprobes.c    |    3 ++-
>  2 files changed, 7 insertions(+), 1 deletion(-)

Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>

- Naveen