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

[Oliver]

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...

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