linux-kernel - Re: [PATCH 2/2] ARM: decompressor: add option to ignore MEM ATAGs

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Date: Sat, 20 Jan 2024 17:57:09 +0100
From: Christian Marangi <ansuelsmth@...il.com>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Russell King <linux@...linux.org.uk>, Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Jonathan Corbet <corbet@....net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Randy Dunlap <rdunlap@...radead.org>,
	"Mike Rapoport (IBM)" <rppt@...nel.org>,
	Eric DeVolder <eric.devolder@...cle.com>,
	Nathan Chancellor <nathan@...nel.org>,
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	Kees Cook <keescook@...omium.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...ainline.org>,
	John Crispin <john@...ozen.org>
Subject: Re: [PATCH 2/2] ARM: decompressor: add option to ignore MEM ATAGs

On Sat, Jan 20, 2024 at 12:51:06PM +0100, Linus Walleij wrote:
> On Fri, Jan 19, 2024 at 9:14 PM Christian Marangi <ansuelsmth@...il.com> wrote:
> 
> > Some bootloaders can pass broken MEM ATAGs that provide hardcoded
> > information about mounted RAM size and physical location.
> > Example booloader provide RAM of size 1.7Gb but actual mounted RAM
> > size is 512Mb causing kernel panic.
> >
> > Add option CONFIG_ARM_ATAG_DTB_COMPAT_IGNORE_MEM to ignore these ATAG
> > and not augument appended DTB memory node.
> >
> > Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
> 
> So you cannot just ignore all the ATAGs I guess?
> If it's the command line you need, you can pass an identical one in
> chosen.

Ehhh it's not that trivial... Downstream we have a patch that takes just
the bootargs from ATAGs but reality is that only MEM is broken.

Also duplicating the bootargs from bootloader in chosen is problematic
as have tons of device that use cmdlinepart to declare partitions and we
are not aware of the partitions of every device.
And also there are some device that supports dual partition and the
value is provided by the bootloader bootargs so duplicating it would
result in not having a good way to support this.

> 
> But if you really need this, it should be there.
> Acked-by: Linus Walleij <linus.walleij@...aro.org>
> 

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