arm64/cpufeature: Validate feature bits spacing in arm64_ftr_regs[]

static void __init sort_ftr_regs(void)

{

	int i;

	unsigned int i;

	for (i = 0; i < ARRAY_SIZE(arm64_ftr_regs); i++) {

		const struct arm64_ftr_reg *ftr_reg = arm64_ftr_regs[i].reg;

		const struct arm64_ftr_bits *ftr_bits = ftr_reg->ftr_bits;

		unsigned int j = 0;

		/*

		 * Features here must be sorted in descending order with respect

		 * to their shift values and should not overlap with each other.

		 */

		for (; ftr_bits->width != 0; ftr_bits++, j++) {

			unsigned int width = ftr_reg->ftr_bits[j].width;

			unsigned int shift = ftr_reg->ftr_bits[j].shift;

			unsigned int prev_shift;

			WARN((shift  + width) > 64,

				"%s has invalid feature at shift %d\n",

				ftr_reg->name, shift);

			/*

			 * Skip the first feature. There is nothing to

			 * compare against for now.

			 */

			if (j == 0)

				continue;

			prev_shift = ftr_reg->ftr_bits[j - 1].shift;

			WARN((shift + width) > prev_shift,

				"%s has feature overlap at shift %d\n",

				ftr_reg->name, shift);

		}

	/* Check that the array is sorted so that we can do the binary search */

	for (i = 1; i < ARRAY_SIZE(arm64_ftr_regs); i++)

		/*

		 * Skip the first register. There is nothing to

		 * compare against for now.

		 */

		if (i == 0)

			continue;

		/*

		 * Registers here must be sorted in ascending order with respect

		 * to sys_id for subsequent binary search in get_arm64_ftr_reg()

		 * to work correctly.

		 */

		BUG_ON(arm64_ftr_regs[i].sys_id < arm64_ftr_regs[i - 1].sys_id);

	}

}

/*

 * Initialise the CPU feature register from Boot CPU values.