linux-kernel - Re: [PATCH 2/2] arm/mm : Report actual image regions in /proc/iomem

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Date:   Mon, 6 Mar 2023 14:00:36 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Jungseung Lee <js07.lee@...sung.com>, linus.walleij@...aro.org,
        amit.kachhap@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, keescook@...omium.org,
        js07.lee@...il.com
Subject: Re: [PATCH 2/2] arm/mm : Report actual image regions in /proc/iomem

On Mon, 6 Mar 2023 at 13:28, Russell King (Oracle)
<linux@...linux.org.uk> wrote:
>
> On Mon, Mar 06, 2023 at 09:14:23PM +0900, Jungseung Lee wrote:
> > Hi, Russell
> >
> > > -----Original Message-----
> > > From: Russell King (Oracle) <linux@...linux.org.uk>
> > > Sent: Monday, March 6, 2023 8:10 PM
> > > To: Jungseung Lee <js07.lee@...sung.com>
> > > Cc: linus.walleij@...aro.org; amit.kachhap@....com; ardb@...nel.org;
> > > linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> > > keescook@...omium.org; js07.lee@...il.com
> > > Subject: Re: [PATCH 2/2] arm/mm : Report actual image regions in
> > > /proc/iomem
> > >
> > > On Mon, Mar 06, 2023 at 02:51:55PM +0900, Jungseung Lee wrote:
> > > >  The resource reservations in /proc/iomem made for the kernel image
> > > > did  not reflect the gaps between text, rodata, and data.
> > > >  Add the "rodata" resource and update the start/end calculations.
> > > >
> > > >  Before :
> > > > 04000000-2f7fffff : System RAM
> > > >   04100000-04cfffff : Kernel code
> > > >   04e00000-05369a27 : Kernel data
> > > >
> > > >  After :
> > > > 04000000-2f7fffff : System RAM
> > > >   04100000-049fffff : Kernel code
> > > >   04a00000-04cb2fff : Kernel rodata
> > > >   04e00000-05369a27 : Kernel data
> > >
> > > NAK. This is API, and programs do read and parse this file. It is
> > > important that this file reports these parameters in a similar way to
> > > other architectures. Other architectures do not split up the
> > > individual regions.
> > >
> >
> > Sounds like an important point, but I failed to find which programs use it
> > as an API. Could you tell me which program uses it as an API?
> >
> > In fact, x86 architecture also split up the individual regions in this way.
> > In addition, most architectures separate the "Kernel bss" area, but arm does
> > not.
>
> Take a look at kexec-tools - that certainly does parse /proc/iomem
> looking for entries such as "Kernel code" and "Kernel data".
>
> It's fine for an architecture to decide to do something else if it
> started to do it early on, but not when something has been established
> for decades.
>

Agree with Russell here.

It would be helpful if you could explain why you think this needs to be changed.