powerpc/prom_init: Check display props exist before enabling btext
It's possible to enable CONFIG_PPC_EARLY_DEBUG_BOOTX for a pseries kernel (maybe it shouldn't be), which is then booted with qemu/slof. But if you do that the kernel crashes in draw_byte(), with a DAR pointing somewhere near INT_MAX. Adding some debug to prom_init we see that we're not able to read the "address" property from OF, so we're just using whatever junk value was on the stack. So check the properties can be read properly from OF, if not we bail out before initialising btext, which avoids the crash. Signed-off-by:Michael Ellerman <mpe@ellerman.id.au> Reviewed-by:
Alexey Kardashevskiy <aik@ozlabs.ru> Link: https://lore.kernel.org/r/20200821103407.3362149-1-mpe@ellerman.id.au
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