• Dave Martin's avatar
    ARM: 6999/1: head, zImage: Always Enter the kernel in ARM state · 540b5738
    Dave Martin authored
    Currently, the documented kernel entry requirements are not
    explicit about whether the kernel should be entered in ARM or
    Thumb, leading to an ambiguitity about how to enter Thumb-2
    kernels.  As a result, the kernel is reliant on the zImage
    decompressor to enter the kernel proper in the correct instruction
    set state.
    
    This patch changes the boot entry protocol for head.S and Image to
    be the same as for zImage: in all cases, the kernel is now entered
    in ARM.
    
    Documentation/arm/Booting is updated to reflect this new policy.
    
    A different rule will be needed for Cortex-M class CPUs as and when
    support for those lands in mainline, since these CPUs don't support
    the ARM instruction set at all: a note is added to the effect that
    the kernel must be entered in Thumb on such systems.
    Signed-off-by: default avatarDave Martin <dave.martin@linaro.org>
    Acked-by: default avatarNicolas Pitre <nicolas.pitre@linaro.org>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    540b5738
head.S 14.8 KB