"Invalid signature" issue on dev kernel launch

[Aruna Hewapathirane]

On Wed, Mar 24, 2021 at 1:26 AM Valdis Klētnieks <valdis.kletnieks at vt.edu>
wrote:

> On Tue, 23 Mar 2021 22:36:33 -0400, Aruna Hewapathirane said:
>
> > I also see:
> > CC      drivers/cpufreq/cpufreq_ondemand.o
> > drivers/cpufreq/cpufreq_ondemand.c: In function ‘od_set_powersave_bias’:
> > drivers/cpufreq/cpufreq_ondemand.c:446:1: warning: the frame size of 1032
> > bytes is larger than 1024 bytes [-Wframe-larger-than=]
> >   446 | }
> >       | ^
> > This is what causes the compile time errors with possible missing
> firmware
>
> No it's not. That's just a *warning* and doesn't stop the build.  The
> reason
> that we have that warning is because on most architectures, the entire
> kernel
> stack has to fit into 2 contiguous 4k pages.
>
> Oh dear that's right it does not stop the build what was I thinking ..


> And a perfectly legal stack can be something like TCP delivering an NFS
> packet
> which then goes to the NFS code, which then hands it off to the VFS layer,
> which checks the page cache, which hands it off to XFS, which schedules
> I/O to
> the filesystem, which gets handed to the block subsystem, which realizes
> that
> the target partition is an LVM partition, and LVM realizes that the
> "physical
> volume" is actually a dm-crypt, and then dm-crypt does some cryptography
> and
> calls the block subsystem to write to the physical disk. Feel free to
> check the code
> path yourself... :)
>
>
Oh my... and oh dear ( again! )


> And all of that has to fit in 8K of stack. That's why we warn when things
> have
> a large stack frame entry.
>

I still don't understand why the 8K barrier ? Why can't we make it say 16K
?

>
> Anyhow, "possible missing firmware" isn't even at compile time - it's
> during
> the build of the initramfs at *install* time.  And the most likely cause of
> that is that missing external firmware that's not GPL - it's all confined
> to 2
> graphics drivers - amdgpu and i915, so not at all related to a warning
> against
> cpufreq...
>
> Understood and my apologies :-)
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