linux-hardening - Re: [RFC PATCH 0/6] Add basic Minidump kernel driver support

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Date:   Tue, 7 Mar 2023 12:27:56 -0500
From:   Brian Masney <bmasney@...hat.com>
To:     Mukesh Ojha <quic_mojha@...cinc.com>
Cc:     agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org,
        keescook@...omium.org, tony.luck@...el.com, gpiccoli@...lia.com,
        catalin.marinas@....com, will@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-remoteproc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 0/6] Add basic Minidump kernel driver support

On Mon, Feb 27, 2023 at 03:45:31PM +0530, Mukesh Ojha wrote:
> 
> 
> On 2/25/2023 12:36 AM, Brian Masney wrote:
> > Hi Mukesh,
> > 
> > On Fri, Feb 24, 2023 at 04:10:42PM +0530, Mukesh Ojha wrote:
> > > On 2/23/2023 6:07 PM, Brian Masney wrote:
> > > > I'd like to test this series plus your series that sets the multiple
> > > > download modes.
> > > 
> > > Sure, you are welcome, but for that you need a device running with Qualcomm
> > > SoC and if it has a upstream support.
> > 
> > I will be testing this series on a sa8540p (QDrive3 Automotive
> > Development Board), which has the sc8280xp SoC with good upstream
> > support. This is also the same board that I have a reliable way to
> > make the board crash due to a known firmware bug.
> > 
> 
> 
> Can you try below patch to just select minidump download mode and make the
> device crash ?
> 
> --------------------------------------->8-------------------------------
> diff --git a/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
> b/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
> index 0d02599..bd8e1a8 100644
> --- a/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
> @@ -280,6 +280,7 @@
>         firmware {
>                 scm: scm {
>                         compatible = "qcom,scm-sc8280xp", "qcom,scm";
> +                       qcom,dload-mode = <&tcsr 0x13000>;
>                 };
>         };
> 
> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> index cdbfe54..e1539a2 100644
> --- a/drivers/firmware/qcom_scm.c
> +++ b/drivers/firmware/qcom_scm.c
> @@ -20,7 +20,7 @@
> 
>  #include "qcom_scm.h"
> 
> -static bool download_mode =
> IS_ENABLED(CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT);
> +static bool download_mode = true;
>  module_param(download_mode, bool, 0);
> 
>  #define SCM_HAS_CORE_CLK       BIT(0)
> @@ -427,7 +427,7 @@ static void qcom_scm_set_download_mode(bool enable)
>                 ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
>         } else if (__scm->dload_mode_addr) {
>                 ret = qcom_scm_io_writel(__scm->dload_mode_addr,
> -                               enable ? QCOM_SCM_BOOT_SET_DLOAD_MODE : 0);
> +                               enable ? 0x20 : 0);
>         } else {
>                 dev_err(__scm->dev,
>                         "No available mechanism for setting download
> mode\n");

Hi Mukesh,

I tried to test this series but I don't know how to actually use the
minidump feature that's in this series. Some more documentation is
needed.

I added this series, plus your other series that adds the download modes
to the SCM driver to my tree, along with your changes above. I
downgraded the firmware on my sa8540p and I have my reproducible crash.
Linux immediately loses control and the board firmware takes over.

I assumed that I'd need to do a warm reboot so that DDR contents are
still present so Linux can grab the memory contents on next reboot.
However, 'fastboot devices' shows no devices so I can't reboot that
way. I can do a cold boot but the DDR contents will be lost.

Also this series needs to be rebased against 6.3rc1.

Brian