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

[Doug Anderson]

Hi,

On Thu, Jul 16, 2020 at 8:20 AM Daniel Thompson
<daniel.thompson@xxxxxxxxxx> 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@xxxxxxxxxxxxx>
> Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
> ---
>  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@xxxxxxxxxxxx>