Bug#820567: kexec on mipsel partially broken between ckt20 and ckt25
On Sun, Apr 10, 2016 at 10:09:38AM +0100, Ben Hutchings wrote:
> On Sat, 2016-04-09 at 18:31 -0700, Elliott Mitchell wrote:
> > Between 3.16.7-ctk20 and 3.16.7-ctk25 the kexec functionality of the
> > Linux kernel was damaged.????The system I'm looking at uses a 3.3 kernel
> > to load the "real" kernel off a filesystem and kexec into that.????The 3.3
> > kernel was able to successfully kexec into a 3.16.7-ctk20 kernel, but
> > is unable to kexec into a 3.16.7-ctk25 kernel.????However I found the
> > 3.16.7-ctk20 IS able to successfully kexec the 3.16.7-ctk25 kernel.
>
> Surely this is a bug in the built-in (3.3) kernel, not the new one? ??If
> there's something simple that can be done in the Debian kernel to work
> around this, we should do that, but otherwise you're stuck with this.
This is certainly a reasonable theory. Alas, I cannot speak to which of
these theories is correct. All I can say for certain is that something
changed between ctk20 and ctk25 which made the 3.3 kernel unable to kexec
ctk25. I'm under the impression as of 3.3 the kexec functionality was
supposed to be stable on MIPS, but that could be incorrect.
I should also note, during the failed kexecs I would see the messages
from the 3.3 kernel saying the kexec was starting, but never see any
messages from the ctk25 kernel. Unless someone wants to send me a JTAG
decoder that is all I can say.
> > Doing a double-kexec does work around the issue, but it means I need to
> > hold onto that one magic kernel for the moment...
> >
> > In other news, it appears sometime between 3.3 and 3.10 there started
> > being a requirement for GCC 4.8 on mipsel.
>
> Packages in jessie must be buildable using compiler versions in jessie.
> That means either gcc-4.8 or gcc-4.9.
linux-source-3.16 is available as a backport to wheezy, which does not
feature gcc-4.8.
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