linux-kernel - Re: [PATCH v2 1/3] kgdb: Honour the kprobe blocklist when setting breakpoints

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Date:   Fri, 17 Jul 2020 15:39:36 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     Jason Wessel <jason.wessel@...driver.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Will Deacon <will@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        kgdb-bugreport@...ts.sourceforge.net,
        LKML <linux-kernel@...r.kernel.org>,
        Patch Tracking <patches@...aro.org>
Subject: Re: [PATCH v2 1/3] kgdb: Honour the kprobe blocklist when setting breakpoints

Hi,

On Thu, Jul 16, 2020 at 8:20 AM Daniel Thompson
<daniel.thompson@...aro.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@...radead.org>
> Signed-off-by: Daniel Thompson <daniel.thompson@...aro.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@...omium.org>