Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 6 Aug 2020 11:11:45 +0100
From:   Russell King - ARM Linux admin <linux@armlinux.org.uk>
To:     Norbert Lange <nolange79@gmail.com>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Petr Malat <oss@malat.biz>, Kees Cook <keescook@chromium.org>,
        Adam Borowski <kilobyte@angband.pl>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Nick Terrell <terrelln@fb.com>
Subject: Re: [PATCH] arm: Add support for ZSTD compressed kernel
Message-ID: <20200806101145.GC1551@shell.armlinux.org.uk>
References: <20200805230555.84214-1-nolange79@gmail.com>
 <20200806003042.GB1551@shell.armlinux.org.uk>
 <CADYdroPtiEfk9e3Loj-2qyyPqgx9GG-h3S2P2Uz49zrk4wVSTw@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CADYdroPtiEfk9e3Loj-2qyyPqgx9GG-h3S2P2Uz49zrk4wVSTw@mail.gmail.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Aug 06, 2020 at 10:45:42AM +0200, Norbert Lange wrote:
> Am Do., 6. Aug. 2020 um 02:30 Uhr schrieb Russell King - ARM Linux
> admin <linux@armlinux.org.uk>:
> >
> > On Thu, Aug 06, 2020 at 01:05:55AM +0200, Norbert Lange wrote:
> > > diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
> > > index 434a16982e34..1af01bfe6638 100644
> > > --- a/arch/arm/boot/compressed/head.S
> > > +++ b/arch/arm/boot/compressed/head.S
> > > @@ -614,7 +614,11 @@ not_relocated:   mov     r0, #0
> > >   */
> > >               mov     r0, r4
> > >               mov     r1, sp                  @ malloc space above stack
> > > +#if defined(CONFIG_KERNEL_ZSTD)
> > > +             add     r2, sp, #0x30000        @ Context needs ~160K
> >
> > That's going to mess up kexec:
> >
> >         /*
> >          * The zImage length does not include its stack (4k) or its
> >          * malloc space (64k).  Include this.
> >          */
> >         len += 0x11000;
> >
> > I guess we need to add this to the information provided to kexec.
> 
> Ouch, I guess it's rather impossible to load a new ZSTD kernel with a old
> kexec version in that case.
> 
> Some ideas to fix that would be:
> 
> -   Increase the padding to "192K + 4K is enough for everyone" in kexec
> -   Add the required/recommended stack+heap size to zImage so kexec can use it.

This is definitely preferred.  See patches - though this is only the
kernel side.  The first I've had for some time and isn't related to
this issue.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!