powerpc: Add missing error check to prom_find_boot_cpu()

[Michael Ellerman]

On Mon, 2017-01-23 at 19:42:54 UTC, Darren Stevens wrote:
> prom_init.c calls 'instance-to-package' twice, but the return
> is not checked during prom_find_boot_cpu(). The result is then
> passed to prom_getprop, which could be PROM_ERROR.
> Add a return check to prevent this.
> 
> This was found on a pasemi system, where CFE doesn't have a working
> 'instance-to package' prom call.
> Before Commit 5c0484e25ec0 ('powerpc: Endian safe trampoline') the
> area around addr 0 as mostly 0's and this doesn't cause a problem.
> Once the macro 'FIXUP_ENDIAN' has been added to head_64.S, the low
> memory area now has non-zero values, which cause the prom_getprop
> call to hang.
> 
> Signed-off-by: Darren Stevens <darren at stevens-zone.net>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/af2b7fa17eb92e52b65f96604448ff

cheers