[PATCHv3 3/4] arm64: Update the Image header

Will Deacon will.deacon at arm.com
Fri Jun 20 01:55:43 PDT 2014

On Thu, Jun 19, 2014 at 11:49:22AM +0100, Mark Rutland wrote:
> Currently the kernel Image is stripped of everything past the initial
> stack, and at runtime the memory is initialised and used by the kernel.
> This makes the effective minimum memory footprint of the kernel larger
> than the size of the loaded binary, though bootloaders have no mechanism
> to identify how large this minimum memory footprint is. This makes it
> difficult to choose safe locations to place both the kernel and other
> binaries required at boot (DTB, initrd, etc), such that the kernel won't
> clobber said binaries or other reserved memory during initialisation.


> +/*
> + * There aren't any ELF relocations we can use to endian-swap values known only
> + * at link time (e.g. the subtraction of two symbol addresses), so we must get
> + * the linker to endian-swap certain values before emitting them.
> + */
> +#define DATA_LE64(data)					\
> +	((((data) & 0x00000000000000ff) << 56) |	\
> +	 (((data) & 0x000000000000ff00) << 40) |	\

Are you sure that these shifts are valid without a UL prefix on the first
constant operand? I don't think the leading zeroes promote the mask to a
64-bit type, so you end up shifting greater than the width of the type.

I guess the compiler doesn't allocate (data & 0xff) into a w register?


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