[Skiboot] [PATCH 2/2] external/mambo: Error out if kernel is too large

[Russell Currey]

On Mon, 2019-03-25 at 15:49 +1100, Oliver wrote:
> On Mon, Mar 25, 2019 at 3:39 PM Russell Currey <ruscur at russell.cc>
> wrote:
> > If you're trying to boot a gigantic kernel in mambo (which you can
> > reproduce by building a kernel with CONFIG_MODULES=n) you'll get
> > misleading errors like:
> > 
> > WARNING: 0: (0): [0:0]: Invalid/unsupported instr
> > 0x00000000[INVALID]
> > WARNING: 0: (0):  PC(EA): 0x0000000030000010
> > PC(RA):0x0000000030000010 MSR: 0x9000000000000000 LR:
> > 0x0000000000000000
> > WARNING: 0: (0):  numInstructions = 0
> > WARNING: 1: (1): [0:0]: Invalid/unsupported instr
> > 0x00000000[INVALID]
> > WARNING: 1: (1):  PC(EA): 0x0000000000000E40
> > PC(RA):0x0000000000000E40 MSR: 0x9000000000000000 LR:
> > 0x0000000000000000
> > WARNING: 1: (1):  numInstructions = 1
> > WARNING: 1: (1): Interrupt to 0x0000000000000E40 from
> > 0x0000000000000E40
> > INFO: 1: (2): ** Execution stopped: Continuous Interrupt,
> > Instruction caused exception,  **
> > 
> > So add an error to skiboot.tcl to warn the user before this
> > happens.
> > Making PAYLOAD_ADDR further back is one way to do this but if
> > there's a
> > less gross way to generally work around this very niche problem, I
> > can
> > suggest that instead.
> > 
> > Signed-off-by: Russell Currey <ruscur at russell.cc>
> > ---
> >  external/mambo/skiboot.tcl | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/external/mambo/skiboot.tcl
> > b/external/mambo/skiboot.tcl
> > index 096f1c34..7a939bfb 100644
> > --- a/external/mambo/skiboot.tcl
> > +++ b/external/mambo/skiboot.tcl
> > @@ -552,6 +552,10 @@ mysim memory fread $mconf(boot_load)
> > $boot_size $mconf(boot_image)
> >  set payload_size [file size $mconf(payload)]
> >  mysim memory fread $mconf(payload_addr) $payload_size
> > $mconf(payload)
> > 
> > +if { $payload_size > [expr $mconf(boot_load) -
> > $mconf(payload_addr)] } {
> > +       error "vmlinux is too large, consider adjusting
> > PAYLOAD_ADDR"
> > +}
> 
> Can we just load the kernel at zero? 768MB really ought to be enough
> for anyone...

I didn't change the address since I don't know why it is the way it is
currently.  Even so we should keep the error just in case some mad lad
makes a gigabyte kernel.

> 
> > +
> >  # Flatten it
> >  epapr::of2dtb mysim $mconf(epapr_dt_addr)
> > 
> > --
> > 2.21.0
> > 
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