Re: [PATCH] ARM: kexec: Fix panic after TLB are invalidated

From: Giancarlo Ferrari <giancarlo.ferrari89@gmail.com>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Mark Rutland <mark.rutland@arm.com>,
	linux-kernel@vger.kernel.org, penberg@kernel.org,
	geert@linux-m68k.org, rppt@kernel.org, akpm@linux-foundation.org,
	linux-arm-kernel@lists.infradead.org,
	giancarlo.ferrari@nokia.com
Subject: Re: [PATCH] ARM: kexec: Fix panic after TLB are invalidated
Date: Fri, 5 Feb 2021 14:36:48 +0000	[thread overview]
Message-ID: <20210205143647.GA7376@p4> (raw)
In-Reply-To: <20210205094458.GF1463@shell.armlinux.org.uk>

On Fri, Feb 05, 2021 at 09:44:59AM +0000, Russell King - ARM Linux admin wrote:
> On Fri, Feb 05, 2021 at 12:40:54AM +0000, Giancarlo Ferrari wrote:
> > Russell,
> > 
> > On Fri, Feb 05, 2021 at 12:18:33AM +0000, Russell King - ARM Linux admin wrote:
> > > On Thu, Feb 04, 2021 at 11:48:42PM +0000, Giancarlo Ferrari wrote:
> > > > Can I ask about having it integrated ?
> > > 
> > > Thanks for testing. Are you willing for me to add:
> > > 
> > > Tested-by: Giancarlo Ferrari <giancarlo.ferrari89@gmail.com>
> > > 
> > > to the commit log?
> > > 
> > 
> > Sure.
> > 
> > I have a question regarding the patch. I saw that the structure start at
> > the end of the relocation code:
> > 
> > data = reboot_code_buffer + relocate_new_kernel_size;
> > 
> > which means it overlap with the global symbol relocate_new_kernel_size.
> > I think is minor comment as the variable is only used in the fncpy()
> > then thrown away.
> 
> The same is true of the rest of the kernel image if that's how you'd
> like to look at it.
> 
> relocate_new_kernel_size is just there to tell the C code the size of
> the function, nothing more nothing less. It isn't there to be copied.
> The copied code doesn't use it.
> 

Yes, clear.

> > Something like:
> > 
> > data = reboot_code_buffer + relocate_new_kernel_size + sizeof(long);
> 
> No. That will place the structure after the size variable, which we
> don't want, and...
> 
> > and accordingly in the instruction (arch/arm/kernel/relocate_kernel.S):
> > 
> > adr	r7, relocate_new_kernel_end
> 
> ... we will then need to follow this with:
> 	add	r7, r7, #4
> 
> or replace it with:
> 	adr	r7, relocate_new_kernel_end + 4
> 
> so that r7 points at "data".
>

It was what I meant with "accordingly".

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

Regards,

GF

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