linux-kernel - Re: [PATCH v12] ARM: uncompress: Validate start of physical memory against passed DTB

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Message-ID: <5f23561e-4099-8578-2c28-4ba39bbaa071@gmail.com>
Date:   Sat, 9 Jan 2021 20:27:54 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Russell King <linux@...linux.org.uk>,
        Ard Biesheuvel <ardb@...nel.org>,
        Nicolas Pitre <nico@...xnic.net>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     Arnd Bergmann <arnd@...db.de>, Eric Miao <eric.miao@...dia.com>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Lukasz Stelmach <l.stelmach@...sung.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Chris Brandt <chris.brandt@...esas.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12] ARM: uncompress: Validate start of physical memory
 against passed DTB

04.01.2021 16:01, Geert Uytterhoeven пишет:
> Currently, the start address of physical memory is obtained by masking
> the program counter with a fixed mask of 0xf8000000.  This mask value
> was chosen as a balance between the requirements of different platforms.
> However, this does require that the start address of physical memory is
> a multiple of 128 MiB, precluding booting Linux on platforms where this
> requirement is not fulfilled.
> 
> Fix this limitation by validating the masked address against the memory
> information in the passed DTB.  Only use the start address
> from DTB when masking would yield an out-of-range address, prefer the
> traditional method in all other cases.  Note that this applies only to the
> explicitly passed DTB on modern systems, and not to a DTB appended to
> the kernel, or to ATAGS.  The appended DTB may need to be augmented by
> information from ATAGS, which may need to rely on knowledge of the start
> address of physical memory itself.
> 
> This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM
> on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space),
> i.e. not at a multiple of 128 MiB.
> 
> Suggested-by: Nicolas Pitre <nico@...xnic.net>
> Suggested-by: Ard Biesheuvel <ardb@...nel.org>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> Reviewed-by: Ard Biesheuvel <ardb@...nel.org>
> Acked-by: Nicolas Pitre <nico@...xnic.net>
> ---
> Submitted to RMK's patch tracker.
> 
> v12:
>   - Drop unneeded initialization of r in get_val(),

I tested this patch on NVIDIA Tegra and haven't spotted any problems.

Tested-by: Dmitry Osipenko <digetx@...il.com>