arm64: enable ARM64_ERRATUM_843419
Quoting bug report:
Currently, the linux-image-arm64 kernel is built with CONFIG_ARM64_ERRATUM_843419 explicitly disabled, while it defaults to on in the Kconfig definition.
The GCC toolchain enables a link time workaround for this erratum, and so all fully linked binaries such as userland executables and shared libraries, as well as the core kernel (vmlinux), are built with mitigations that prevent this erratum from being triggered. However, kernel modules are not fully linked binaries (they are partially linked object files), and so without this CONFIG option enabled, the resulting modules may trigger the erratum and crash or corrupt data (or both).
Note that the Cortex-A53 used in the Raspberry Pi 3 is affected by this erratum.
So please enable CONFIG_ARM64_ERRATUM_843419.