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

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Date:   Mon, 6 Mar 2023 20:58:04 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     <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>
CC:     <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

Friendly review reminder..

-Mukesh

On 2/21/2023 4:55 PM, Mukesh Ojha wrote:
> Minidump is a best effort mechanism to collect useful and predefined data
> for first level of debugging on end user devices running on Qualcomm SoCs.
> It is built on the premise that System on Chip (SoC) or subsystem part of
> SoC crashes, due to a range of hardware and software bugs. Hence, the
> ability to collect accurate data is only a best-effort. The data collected
> could be invalid or corrupted, data collection itself could fail, and so on.
> 
> Qualcomm devices in engineering mode provides a mechanism for generating
> full system ramdumps for post mortem debugging. But in some cases it's
> however not feasible to capture the entire content of RAM. The minidump
> mechanism provides the means for selecting which snippets should be
> included in the ramdump.
> 
> The core of minidump feature is part of Qualcomm's boot firmware code.
> It initializes shared memory (SMEM), which is a part of DDR and
> allocates a small section of SMEM to minidump table i.e also called
> global table of content (G-ToC). Each subsystem (APSS, ADSP, ...) has
> their own table of segments to be included in the minidump and all get
> their reference from G-ToC. Each segment/region has some details like
> name, physical address and it's size etc. and it could be anywhere
> scattered in the DDR.
> 
> Existing upstream Qualcomm remoteproc driver[1] already supports minidump
> feature for remoteproc instances like ADSP, MODEM, ... where predefined
> selective segments of subsystem region can be dumped as part of
> coredump collection which generates smaller size artifacts compared to
> complete coredump of subsystem on crash.
> 
> [1]
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/remoteproc/qcom_common.c#n142
> 
> In addition to managing and querying the APSS minidump description,
> the Linux driver maintains a ELF header in a segment. This segment
> gets updated with section/program header whenever a new entry gets
> registered.
> 
> Patch 1/6 is very trivial change.
> Patch 2/6 moves the minidump specific data structure and macro to
>   qcom_minidump.h so that (3/6) minidump driver can use.
> Patch 3/6 implements qualcomm minidump kernel driver and exports
>   symbol which other minidump kernel client can use.
> Patch 4/6 enables the qualcomm minidump driver.
> Patch 5/6 Use the exported symbol from minidump driver in qcom_common
>   for querying minidump descriptor for a subsystem.
> Patch 6/6 Register pstore region with minidump.
> 
> Testing of the patches has been done on sm8450 target with the help
> of out of tree patch which helps to set the download mode and storage
> type(on which dump will be saved) for which i will send separate series.
> 
> Mukesh Ojha (6):
>    remoteproc: qcom: Expand MD_* as MINIDUMP_*
>    remoteproc: qcom: Move minidump specific data to qcom_minidump.h
>    soc: qcom: Add Qualcomm minidump kernel driver
>    arm64: defconfig: Enable Qualcomm minidump driver
>    remoterproc: qcom: refactor to leverage exported minidump symbol
>    pstore/ram: Register context with minidump
> 
>   arch/arm64/configs/defconfig     |   1 +
>   drivers/remoteproc/qcom_common.c |  75 +-----
>   drivers/soc/qcom/Kconfig         |  14 ++
>   drivers/soc/qcom/Makefile        |   1 +
>   drivers/soc/qcom/qcom_minidump.c | 490 +++++++++++++++++++++++++++++++++++++++++
>   fs/pstore/ram.c                  |  77 ++++++
>   include/soc/qcom/minidump.h      |  40 ++++
>   include/soc/qcom/qcom_minidump.h |  88 +++++++
>   8 files changed, 717 insertions(+), 69 deletions(-)
>   create mode 100644 drivers/soc/qcom/qcom_minidump.c
>   create mode 100644 include/soc/qcom/minidump.h
>   create mode 100644 include/soc/qcom/qcom_minidump.h
>