linux-hardening - Re: [RFC PATCH 6/6] pstore/ram: Register context with minidump

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Date:   Tue, 21 Mar 2023 21:43:31 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     Kees Cook <keescook@...omium.org>
CC:     <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.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 6/6] pstore/ram: Register context with minidump



On 2/24/2023 1:13 AM, Kees Cook wrote:
> On Tue, Feb 21, 2023 at 04:55:13PM +0530, Mukesh Ojha wrote:
>> There are system which does not uses pstore directly but
>> may have the interest in the context saved by pstore.
>> Register pstore regions with minidump so that it get
>> dumped on minidump collection.
> 
> Okay, so, this is a really interesting case -- it's a RAM backend that
> is already found on a system by pstore via device tree, but there is
> _another_ RAM overlay (minidump) that would like to know more about how
> the pstore ram backend carves up the memory regions so it can examine
> them itself too. (i.e. it's another "interface" like the pstorefs.)
> 
> So we need to provide the mapping back to the overlay. It feels to me
> like the logic for this needs to live in the minidump driver itself
> (rather than in the pstore RAM backend). Specifically, it wants to know
> about all the operational frontends (dmesg, console, ftrace, pmsg) with
> their virt & phys addresses and size.
> 
> The frontends are defined via enum pstore_type_id, and the other values
> are "normal" types, so it should be possible to move this logic into
> minidump instead, leaving a simpler callback. Perhaps something like:
> 
> void pstore_region_defined(enum pstore_type_id, void *virt,
> 			   phys_addr_t phys, size_t size);
> 
> How the pstore ram backend should know to call this, though, I'm
> struggling to find a sensible way. How can it determine if the device
> tree region is actually contained by a minidump overlay?


Do you think, if qcom_minidump_ready() can be used which checks minidump 
readiness ?

-Mukesh
>