From: Linus Walleij <linus.walleij@linaro.org>
To: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: "Russell King" <linux@armlinux.org.uk>,
"Ard Biesheuvel" <ardb@kernel.org>,
"Nicolas Pitre" <nico@fluxnic.net>,
"Marek Szyprowski" <m.szyprowski@samsung.com>,
"Dmitry Osipenko" <digetx@gmail.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Eric Miao" <eric.miao@nvidia.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Lukasz Stelmach" <l.stelmach@samsung.com>,
"Stephen Boyd" <sboyd@kernel.org>,
"Chris Brandt" <chris.brandt@renesas.com>,
"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v12] ARM: uncompress: Validate start of physical memory against passed DTB
Date: Sat, 9 Jan 2021 00:57:24 +0100 [thread overview]
Message-ID: <CACRpkdZyV-tye0b6Pxf6s_SSEy1sq=Hqr_xXUopJrCkXsu9m9g@mail.gmail.com> (raw)
In-Reply-To: <20210104130111.1269694-1-geert+renesas@glider.be>
On Mon, Jan 4, 2021 at 2:01 PM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:
> 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@fluxnic.net>
> Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
> Acked-by: Nicolas Pitre <nico@fluxnic.net>
Sorry for the long delay in reading the patch :(
I really like the looks of this now, moreover it is very useful.
I suppose it is already in the patch tracker, but for the record:
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> + reg = fdt_getprop(fdt, offset, "linux,usable-memory", &len);
I suppose we already had a discussion of why this property
is undocumented? Or should we document it? Obviously
it is already in widespread use.
Yours,
Linus Walleij
next prev parent reply other threads:[~2021-01-08 23:58 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20210104130133eucas1p2d4e75b0dfd3afca7af8952ff09568070@eucas1p2.samsung.com>
2021-01-04 13:01 ` [PATCH v12] ARM: uncompress: Validate start of physical memory against passed DTB Geert Uytterhoeven
2021-01-07 10:36 ` Marek Szyprowski
2021-01-07 10:47 ` Geert Uytterhoeven
2021-01-08 23:57 ` Linus Walleij [this message]
2021-01-11 16:19 ` Geert Uytterhoeven
2021-01-18 13:09 ` Linus Walleij
2021-01-09 17:27 ` Dmitry Osipenko
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