x86, boot: Define the 2.12 bzImage boot protocol

Define the 2.12 bzImage boot protocol: add xloadflags and additional
fields to allow the command line, initramfs and struct boot_params to
live above the 4 GiB mark.

The xloadflags now communicates if this is a 64-bit kernel with the
legacy 64-bit entry point and which of the EFI handover entry points
are supported.

Avoid adding new read flags to loadflags because of claimed
bootloaders testing the whole byte for == 1 to determine bzImageness
at least until the issue can be researched further.

This is based on patches by Yinghai Lu and David Woodhouse.

Originally-by: Yinghai Lu <[email protected]>
Originally-by: David Woodhouse <[email protected]>
Acked-by: Yinghai Lu <[email protected]>
Acked-by: David Woodhouse <[email protected]>
Acked-by: Matt Fleming <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Cc: Rob Landley <[email protected]>
Cc: Gokul Caushik <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Joe Millenbach <[email protected]>

Documentation/x86/boot.txt

@@ -57,6 +57,10 @@ Protocol 2.10:	(Kernel 2.6.31) Added a protocol for relaxed alignment
 Protocol 2.11:	(Kernel 3.6) Added a field for offset of EFI handover
 		protocol entry point.
 
+Protocol 2.12:	(Kernel 3.9) Added the xloadflags field and extension fields
+	 	to struct boot_params for for loading bzImage and ramdisk
+		above 4G in 64bit.
+
 **** MEMORY LAYOUT
 
 The traditional memory map for the kernel loader, used for Image or
@@ -182,7 +186,7 @@ Offset	Proto	Name		Meaning
 0230/4	2.05+	kernel_alignment Physical addr alignment required for kernel
 0234/1	2.05+	relocatable_kernel Whether kernel is relocatable or not
 0235/1	2.10+	min_alignment	Minimum alignment, as a power of two
-0236/2	N/A	pad3		Unused
+0236/2	2.12+	xloadflags	Boot protocol option flags
 0238/4	2.06+	cmdline_size	Maximum size of the kernel command line
 023C/4	2.07+	hardware_subarch Hardware subarchitecture
 0240/8	2.07+	hardware_subarch_data Subarchitecture-specific data
@@ -582,6 +586,27 @@ Protocol:	2.10+
   misaligned kernel.  Therefore, a loader should typically try each
   power-of-two alignment from kernel_alignment down to this alignment.
 
+Field name:     xloadflags
+Type:           read
+Offset/size:    0x236/2
+Protocol:       2.12+
+
+  This field is a bitmask.
+
+  Bit 0 (read):	XLF_KERNEL_64
+	- If 1, this kernel has the legacy 64-bit entry point at 0x200.
+
+  Bit 1 (read): XLF_CAN_BE_LOADED_ABOVE_4G
+        - If 1, kernel/boot_params/cmdline/ramdisk can be above 4G.
+
+  Bit 2 (read):	XLF_EFI_HANDOVER_32
+	- If 1, the kernel supports the 32-bit EFI handoff entry point
+          given at handover_offset.
+
+  Bit 3 (read): XLF_EFI_HANDOVER_64
+	- If 1, the kernel supports the 64-bit EFI handoff entry point
+          given at handover_offset + 0x200.
+
 Field name:	cmdline_size
 Type:		read
 Offset/size:	0x238/4

Documentation/x86/zero-page.txt

@@ -19,6 +19,9 @@ Offset	Proto	Name		Meaning
 090/010	ALL	hd1_info	hd1 disk parameter, OBSOLETE!!
 0A0/010	ALL	sys_desc_table	System description table (struct sys_desc_table)
 0B0/010	ALL	olpc_ofw_header	OLPC's OpenFirmware CIF and friends
+0C0/004	ALL	ext_ramdisk_image ramdisk_image high 32bits
+0C4/004	ALL	ext_ramdisk_size  ramdisk_size high 32bits
+0C8/004	ALL	ext_cmd_line_ptr  cmd_line_ptr high 32bits
 140/080	ALL	edid_info	Video mode setup (struct edid_info)
 1C0/020	ALL	efi_info	EFI 32 information (struct efi_info)
 1E0/004	ALL	alk_mem_k	Alternative mem check, in KB
@@ -27,6 +30,7 @@ Offset	Proto	Name		Meaning
 1E9/001	ALL	eddbuf_entries	Number of entries in eddbuf (below)
 1EA/001	ALL	edd_mbr_sig_buf_entries	Number of entries in edd_mbr_sig_buffer
 				(below)
+1EF/001	ALL	sentinel	Used to detect broken bootloaders
 290/040	ALL	edd_mbr_sig_buffer EDD MBR signatures
 2D0/A00	ALL	e820_map	E820 memory map table
 				(array of struct e820entry)