ARM: dts: bcm283x: Reserve first page for firmware

[ Upstream commit b0804ed0cadd7e38d94d2f15cdcc0d9695818856 ]

The Raspberry Pi startup stub files for multi-core BCM283X processors
make the secondary CPUs spin until the corresponding mailbox is
written. These stubs are loaded at physical address 0x00000xxx (as seen
by the ARMs), but this page will be reused by the kernel unless it is
explicitly reserved, causing the waiting cores to execute random code.

Use the /memreserve/ Device Tree directive to mark the first page as
off-limits to the kernel.

See: raspberrypi/linux#1989
Signed-off-by: Phil Elwell <phil@raspberrypi.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/arm/boot/dts/bcm283x.dtsi

@@ -3,6 +3,11 @@
 #include <dt-bindings/clock/bcm2835-aux.h>
 #include <dt-bindings/gpio/gpio.h>
 
+/* firmware-provided startup stubs live here, where the secondary CPUs are
+ * spinning.
+ */
+/memreserve/ 0x00000000 0x00001000;
+
 /* This include file covers the common peripherals and configuration between
  * bcm2835 and bcm2836 implementations, leaving the CPU configuration to
  * bcm2835.dtsi and bcm2836.dtsi.