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From:   Tong Zhang <ztong0001@gmail.com>
Date:   Wed, 16 Feb 2022 08:43:34 -0800
Message-ID: <CAA5qM4DaAHc2XyMwej7V3VzzoGa8uW+Rrg29C39tkeLrYnYhmQ@mail.gmail.com>
Subject: Re: [PATCH] platform/chrome: cros_ec: honor acpi=off
To:     Guenter Roeck <groeck@google.com>
Cc:     Benson Leung <bleung@chromium.org>,
        Guenter Roeck <groeck@chromium.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Wed, Feb 16, 2022 at 8:12 AM Guenter Roeck <groeck@google.com> wrote:
>
> On Tue, Feb 15, 2022 at 10:26 PM Tong Zhang <ztong0001@gmail.com> wrote:
> >
> > when acpi=off is provided in bootarg, kernel crash with
> >
> >  BUG: kernel NULL pointer dereference, address: 0000000000000018
> >  RIP: 0010:acpi_ns_walk_namespace+0x57/0x280
> >   <TASK>
> >  ? acpi_get_devices+0x140/0x140
> >  cros_ec_lpc_init+0x25/0x100
> >
> > Driver should check if ACPI is disabled before calling acpi_get_devices(),
> > otherwise acpi_walk_namespace() will dereference null pointer since the
> > acpi_gbl_root_node is not initialized.
> > This is a common pattern and should be fixed in ACPI framework to prevent
> > such crash in the future, but since many drivers are already doing explicit
> > check(acpi_disable) we do the same thing here.
> >
Thanks for the comment. This is no longer an issue since the ACPI
patch I mentioned is staged in ACPICA tree.
https://github.com/acpica/acpica/commit/b1c3656ef4950098e530be68d4b589584f06cddc