x86/boot: Introduce setup_indirect

  sure to consider the case where the linked list already contains

  entries.

  The setup_data is a bit awkward to use for extremely large data objects,

  both because the setup_data header has to be adjacent to the data object

  and because it has a 32-bit length field. However, it is important that

  intermediate stages of the boot process have a way to identify which

  chunks of memory are occupied by kernel data.

  Thus setup_indirect struct and SETUP_INDIRECT type were introduced in

  protocol 2.15.

  struct setup_indirect {

    __u32 type;

    __u32 reserved;  /* Reserved, must be set to zero. */

    __u64 len;

    __u64 addr;

  };

  The type member is a SETUP_INDIRECT | SETUP_* type. However, it cannot be

  SETUP_INDIRECT itself since making the setup_indirect a tree structure

  could require a lot of stack space in something that needs to parse it

  and stack space can be limited in boot contexts.

  Let's give an example how to point to SETUP_E820_EXT data using setup_indirect.

  In this case setup_data and setup_indirect will look like this:

  struct setup_data {

    __u64 next = 0 or <addr_of_next_setup_data_struct>;

    __u32 type = SETUP_INDIRECT;

    __u32 len = sizeof(setup_data);

    __u8 data[sizeof(setup_indirect)] = struct setup_indirect {

      __u32 type = SETUP_INDIRECT | SETUP_E820_EXT;

      __u32 reserved = 0;

      __u64 len = <len_of_SETUP_E820_EXT_data>;

      __u64 addr = <addr_of_SETUP_E820_EXT_data>;

    }

  }

.. note::

     SETUP_INDIRECT | SETUP_NONE objects cannot be properly distinguished

     from SETUP_INDIRECT itself. So, this kind of objects cannot be provided

     by the bootloaders.

============	============

Field name:	pref_address

Type:		read (reloc)

Offset/size:	0x000c/4

============	==============

  This field contains maximal allowed type for setup_data.

  This field contains maximal allowed type for setup_data and setup_indirect structs.

The Image Checksum

			is_overlapping = true;

		}

		if (ptr->type == SETUP_INDIRECT &&

		    ((struct setup_indirect *)ptr->data)->type != SETUP_INDIRECT) {

			avoid.start = ((struct setup_indirect *)ptr->data)->addr;

			avoid.size = ((struct setup_indirect *)ptr->data)->len;

			if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) {

				*overlap = avoid;

				earliest = overlap->start;

				is_overlapping = true;

			}

		}

		ptr = (struct setup_data *)(unsigned long)ptr->next;

	}

	/* Size total. */

	.long	kernel_info_end - kernel_info

	/* Maximal allowed type for setup_data. */

	/* Maximal allowed type for setup_data and setup_indirect structs. */

	.long	SETUP_TYPE_MAX

kernel_info_var_len_data:

	# Part 2 of the header, from the old setup.S

		.ascii	"HdrS"		# header signature

		.word	0x020d		# header version number (>= 0x0105)

		.word	0x020f		# header version number (>= 0x0105)

					# or else old loadlin-1.5 will fail)

		.globl realmode_swtch

realmode_swtch:	.word	0, 0		# default_switch, SETUPSEG

#ifndef _ASM_X86_BOOTPARAM_H

#define _ASM_X86_BOOTPARAM_H

/* setup_data types */

/* setup_data/setup_indirect types */

#define SETUP_NONE			0

#define SETUP_E820_EXT			1

#define SETUP_DTB			2

#define SETUP_APPLE_PROPERTIES		5

#define SETUP_JAILHOUSE			6

/* max(SETUP_*) */

#define SETUP_TYPE_MAX			SETUP_JAILHOUSE

#define SETUP_INDIRECT			(1<<31)

/* SETUP_INDIRECT | max(SETUP_*) */

#define SETUP_TYPE_MAX			(SETUP_INDIRECT | SETUP_JAILHOUSE)

/* ram_size flags */

#define RAMDISK_IMAGE_START_MASK	0x07FF

	__u8 data[0];

};

/* extensible setup indirect data node */

struct setup_indirect {

	__u32 type;

	__u32 reserved;  /* Reserved, must be set to zero. */

	__u64 len;

	__u64 addr;

};

struct setup_header {

	__u8	setup_sects;

	__u16	root_flags;