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>

3 files changed, 76 insertions, 28 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) }
diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index 92862cd90201..c15ddaf90710 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -1,6 +1,31 @@
 #ifndef _ASM_X86_BOOTPARAM_H
 #define _ASM_X86_BOOTPARAM_H
 
+/* setup_data types */
+#define SETUP_NONE                      0
+#define SETUP_E820_EXT                  1
+#define SETUP_DTB                       2
+#define SETUP_PCI                       3
+
+/* ram_size flags */
+#define RAMDISK_IMAGE_START_MASK        0x07FF
+#define RAMDISK_PROMPT_FLAG             0x8000
+#define RAMDISK_LOAD_FLAG               0x4000
+
+/* loadflags */
+#define LOADED_HIGH     (1<<0)
+#define QUIET_FLAG      (1<<5)
+#define KEEP_SEGMENTS   (1<<6)
+#define CAN_USE_HEAP    (1<<7)
+
+/* xloadflags */
+#define XLF_KERNEL_64                   (1<<0)
+#define XLF_CAN_BE_LOADED_ABOVE_4G      (1<<1)
+#define XLF_EFI_HANDOVER_32             (1<<2)
+#define XLF_EFI_HANDOVER_64             (1<<3)
+
+#ifndef __ASSEMBLY__
+
 #include <linux/types.h>
 #include <linux/screen_info.h>
 #include <linux/apm_bios.h>
@@ -9,12 +34,6 @@
 #include <asm/ist.h>
 #include <video/edid.h>
 
-/* setup data types */
-#define SETUP_NONE                      0
-#define SETUP_E820_EXT                  1
-#define SETUP_DTB                       2
-#define SETUP_PCI                       3
-
 /* extensible setup data list node */
 struct setup_data {
         __u64 next;
@@ -28,9 +47,6 @@ struct setup_header {
         __u16   root_flags;
         __u32   syssize;
         __u16   ram_size;
-#define RAMDISK_IMAGE_START_MASK        0x07FF
-#define RAMDISK_PROMPT_FLAG             0x8000
-#define RAMDISK_LOAD_FLAG               0x4000
         __u16   vid_mode;
         __u16   root_dev;
         __u16   boot_flag;
@@ -42,10 +58,6 @@ struct setup_header {
         __u16   kernel_version;
         __u8    type_of_loader;
         __u8    loadflags;
-#define LOADED_HIGH     (1<<0)
-#define QUIET_FLAG      (1<<5)
-#define KEEP_SEGMENTS   (1<<6)
-#define CAN_USE_HEAP    (1<<7)
         __u16   setup_move_size;
         __u32   code32_start;
         __u32   ramdisk_image;
@@ -58,7 +70,8 @@ struct setup_header {
         __u32   initrd_addr_max;
         __u32   kernel_alignment;
         __u8    relocatable_kernel;
-        __u8    _pad2[3];
+        __u8    min_alignment;
+        __u16   xloadflags;
         __u32   cmdline_size;
         __u32   hardware_subarch;
         __u64   hardware_subarch_data;
@@ -106,7 +119,10 @@ struct boot_params {
         __u8  hd1_info[16];     /* obsolete! */         /* 0x090 */
         struct sys_desc_table sys_desc_table;           /* 0x0a0 */
         struct olpc_ofw_header olpc_ofw_header;         /* 0x0b0 */
-        __u8  _pad4[128];                               /* 0x0c0 */
+        __u32 ext_ramdisk_image;                        /* 0x0c0 */
+        __u32 ext_ramdisk_size;                         /* 0x0c4 */
+        __u32 ext_cmd_line_ptr;                         /* 0x0c8 */
+        __u8  _pad4[116];                               /* 0x0cc */
         struct edid_info edid_info;                     /* 0x140 */
         struct efi_info efi_info;                       /* 0x1c0 */
         __u32 alt_mem_k;                                /* 0x1e0 */
@@ -115,7 +131,20 @@ struct boot_params {
         __u8  eddbuf_entries;                           /* 0x1e9 */
         __u8  edd_mbr_sig_buf_entries;                  /* 0x1ea */
         __u8  kbd_status;                               /* 0x1eb */
-        __u8  _pad6[5];                                 /* 0x1ec */
+        __u8  _pad5[3];                                 /* 0x1ec */
+        /*
+         * The sentinel is set to a nonzero value (0xff) in header.S.
+         *
+         * A bootloader is supposed to only take setup_header and put
+         * it into a clean boot_params buffer. If it turns out that
+         * it is clumsy or too generous with the buffer, it most
+         * probably will pick up the sentinel variable too. The fact
+         * that this variable then is still 0xff will let kernel
+         * know that some variables in boot_params are invalid and
+         * kernel should zero out certain portions of boot_params.
+         */
+        __u8  sentinel;                                 /* 0x1ef */
+        __u8  _pad6[1];                                 /* 0x1f0 */
         struct setup_header hdr;    /* setup header */  /* 0x1f1 */
         __u8  _pad7[0x290-0x1f1-sizeof(struct setup_header)];
         __u32 edd_mbr_sig_buffer[EDD_MBR_SIG_MAX];      /* 0x290 */
@@ -134,6 +163,6 @@ enum {
         X86_NR_SUBARCHS,
 };
 
-
+#endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_X86_BOOTPARAM_H */