linux-kernel - Re: [PATCH v2 0/3] kgdb: Honour the kprobe blacklist when setting breakpoints

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Date:   Fri, 17 Jul 2020 22:48:26 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     Jason Wessel <jason.wessel@...driver.com>,
        Douglas Anderson <dianders@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>, sumit.garg@...aro.org,
        pmladek@...e.com, sergey.senozhatsky@...il.com, will@...nel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        kgdb-bugreport@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        patches@...aro.org
Subject: Re: [PATCH v2 0/3] kgdb: Honour the kprobe blacklist when setting
 breakpoints

Hi Daniel,

On Thu, 16 Jul 2020 16:19:40 +0100
Daniel Thompson <daniel.thompson@...aro.org> wrote:

> kgdb has traditionally adopted a no safety rails approach to breakpoint
> placement. If the debugger is commanded to place a breakpoint at an
> address then it will do so even if that breakpoint results in kgdb
> becoming inoperable.
> 
> A stop-the-world debugger with memory peek/poke intrinsically provides
> its operator with the means to hose their system in all manner of
> exciting ways (not least because stopping-the-world is already a DoS
> attack ;-) ). Nevertheless the current no safety rail approach is
> difficult to defend, especially given kprobes can provide us with plenty
> of machinery to mark the parts of the kernel where breakpointing is
> discouraged.
> 
> This patchset introduces some safety rails by using the existing kprobes
> infrastructure and ensures this will be enabled by default on
> architectures that implement kprobes. At present it does not cover
> absolutely all locations where breakpoints can cause trouble but it will
> block off several avenues, including the architecture specific parts
> that are handled by arch_within_kprobe_blacklist().

This series looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

To fix the build error with ipw2x00 driver, please feel free to
include my fix patch.

Thank you,

> 
> 
> Daniel Thompson (3):
>   kgdb: Honour the kprobe blocklist when setting breakpoints
>   kgdb: Use the kprobe blocklist to limit single stepping
>   kgdb: Add NOKPROBE labels on the trap handler functions
> 
>  include/linux/kgdb.h        | 19 +++++++++++++++++++
>  kernel/debug/debug_core.c   | 25 +++++++++++++++++++++++++
>  kernel/debug/gdbstub.c      | 10 +++++++++-
>  kernel/debug/kdb/kdb_bp.c   | 17 +++++++++++------
>  kernel/debug/kdb/kdb_main.c | 10 ++++++++--
>  lib/Kconfig.kgdb            | 14 ++++++++++++++
>  6 files changed, 86 insertions(+), 9 deletions(-)
> 
> --
> 2.25.4
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>