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 <yinghai@kernel.org>
Originally-by: David Woodhouse <dwmw2@infradead.org>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: David Woodhouse <dwmw2@infradead.org>
Acked-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1359058816-7615-26-git-send-email-yinghai@kernel.org
Cc: Rob Landley <rob@landley.net>
Cc: Gokul Caushik <caushik1@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joe Millenbach <jmillenbach@gmail.com>

2 files changed, 30 insertions, 11 deletions

diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 8c132a625b94..944ce595f767 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -21,6 +21,7 @@
 #include <asm/e820.h>
 #include <asm/page_types.h>
 #include <asm/setup.h>
+#include <asm/bootparam.h>
 #include "boot.h"
 #include "voffset.h"
 #include "zoffset.h"
@@ -255,6 +256,9 @@ section_table:
         # header, from the old boot sector.
 
         .section ".header", "a"
+        .globl  sentinel
+sentinel:       .byte 0xff, 0xff        /* Used to detect broken loaders */
+
         .globl  hdr
 hdr:
 setup_sects:    .byte 0                 /* Filled in by build.c */
@@ -279,7 +283,7 @@ _start:
         # Part 2 of the header, from the old setup.S
 
                 .ascii  "HdrS"          # header signature
-                .word   0x020b          # header version number (>= 0x0105)
+                .word   0x020c          # header version number (>= 0x0105)
                                         # or else old loadlin-1.5 will fail)
                 .globl realmode_swtch
 realmode_swtch: .word   0, 0            # default_switch, SETUPSEG
@@ -297,13 +301,7 @@ type_of_loader:	.byte	0		# 0 means ancient bootloader, newer
 
 # flags, unused bits must be zero (RFU) bit within loadflags
 loadflags:
-LOADED_HIGH     = 1                     # If set, the kernel is loaded high
-CAN_USE_HEAP    = 0x80                  # If set, the loader also has set
-                                        # heap_end_ptr to tell how much
-                                        # space behind setup.S can be used for
-                                        # heap purposes.
-                                        # Only the loader knows what is free
-                .byte   LOADED_HIGH
+                .byte   LOADED_HIGH     # The kernel is to be loaded high
 
 setup_move_size: .word  0x8000          # size to move, when setup is not
                                         # loaded at 0x90000. We will move setup
@@ -369,7 +367,23 @@ relocatable_kernel:    .byte 1
 relocatable_kernel:    .byte 0
 #endif
 min_alignment:          .byte MIN_KERNEL_ALIGN_LG2      # minimum alignment
-pad3:                   .word 0
+
+xloadflags:
+#ifdef CONFIG_X86_64
+# define XLF0 XLF_KERNEL_64                     /* 64-bit kernel */
+#else
+# define XLF0 0
+#endif
+#ifdef CONFIG_EFI_STUB
+# ifdef CONFIG_X86_64
+#  define XLF23 XLF_EFI_HANDOVER_64             /* 64-bit EFI handover ok */
+# else
+#  define XLF23 XLF_EFI_HANDOVER_32             /* 32-bit EFI handover ok */
+# endif
+#else
+# define XLF23 0
+#endif
+                        .word XLF0 | XLF23
 
 cmdline_size:   .long   COMMAND_LINE_SIZE-1     #length of the command line,
                                                 #added with boot protocol
@@ -397,8 +411,13 @@ pref_address:		.quad LOAD_PHYSICAL_ADDR	# preferred load addr
 #define INIT_SIZE VO_INIT_SIZE
 #endif
 init_size:              .long INIT_SIZE         # kernel initialization size
-handover_offset:        .long 0x30              # offset to the handover
+handover_offset:
+#ifdef CONFIG_EFI_STUB
+                        .long 0x30              # offset to the handover
                                                 # protocol entry point
+#else
+                        .long 0
+#endif
 
 # End of setup header #####################################################
 
diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld
index 03c0683636b6..96a6c7563538 100644
--- a/arch/x86/boot/setup.ld
+++ b/arch/x86/boot/setup.ld
@@ -13,7 +13,7 @@ SECTIONS
         .bstext         : { *(.bstext) }
         .bsdata         : { *(.bsdata) }
 
-        . = 497;
+        . = 495;
         .header         : { *(.header) }
         .entrytext      : { *(.entrytext) }
         .inittext       : { *(.inittext) }