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References: <20200716151943.2167652-1-daniel.thompson@linaro.org> <20200716151943.2167652-2-daniel.thompson@linaro.org>
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From:   Doug Anderson <dianders@chromium.org>
Date:   Fri, 17 Jul 2020 15:39:36 -0700
Message-ID: <CAD=FV=XUxWoWr2VZJ0Ng6orxDJmEt8VRYeiFC11mT8L=NwpKig@mail.gmail.com>
Subject: Re: [PATCH v2 1/3] kgdb: Honour the kprobe blocklist when setting breakpoints
To:     Daniel Thompson <daniel.thompson@linaro.org>
Cc:     Jason Wessel <jason.wessel@windriver.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Sumit Garg <sumit.garg@linaro.org>,
        Petr Mladek <pmladek@suse.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Will Deacon <will@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        kgdb-bugreport@lists.sourceforge.net,
        LKML <linux-kernel@vger.kernel.org>,
        Patch Tracking <patches@linaro.org>
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Hi,

On Thu, Jul 16, 2020 at 8:20 AM Daniel Thompson
<daniel.thompson@linaro.org> wrote:
>
> Currently kgdb has absolutely no safety rails in place to discourage or
> prevent a user from placing a breakpoint in dangerous places such as
> the debugger's own trap entry/exit and other places where it is not safe
> to take synchronous traps.
>
> Introduce a new config symbol KGDB_HONOUR_BLOCKLIST and modify the
> default implementation of kgdb_validate_break_address() so that we use
> the kprobe blocklist to prohibit instrumentation of critical functions
> if the config symbol is set. The config symbol dependencies are set to
> ensure that the blocklist will be enabled by default if we enable KGDB
> and are compiling for an architecture where we HAVE_KPROBES.
>
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
> ---
>  include/linux/kgdb.h      | 18 ++++++++++++++++++
>  kernel/debug/debug_core.c |  4 ++++
>  kernel/debug/kdb/kdb_bp.c |  9 +++++++++
>  lib/Kconfig.kgdb          | 14 ++++++++++++++
>  4 files changed, 45 insertions(+)

Seems reasonable to me.

Reviewed-by: Douglas Anderson <dianders@chromium.org>