This patch defines a 32-bit boot protocol and adds corresponding
document. It is based on the proposal of Peter Anvin.


Known issues:

- The hd0_info and hd1_info are deleted from the zero page. Additional
  work should be done for this? Or this is unnecessary (because no new
  fields will be added to zero page)?

- The fields in zero page are fairly complex (such as struct
  edd_info). Is it necessary to document every field inside the first
  level fields, until the primary data type? Or is it sufficient to
  provide the C struct name only?


ChangeLog:

-- v2 --

- Revise zero page description according to the source code and move
  them to zero-page.txt.


Signed-off-by: Huang Ying <[EMAIL PROTECTED]>

---

 boot.txt      |   70 +++++++++++++++++++++++++++++++
 zero-page.txt |  127 ++++++++++++----------------------------------------------
 2 files changed, 97 insertions(+), 100 deletions(-)

Index: linux-2.6.23-rc6/Documentation/i386/boot.txt
===================================================================
--- linux-2.6.23-rc6.orig/Documentation/i386/boot.txt   2007-09-11 
10:50:29.000000000 +0800
+++ linux-2.6.23-rc6/Documentation/i386/boot.txt        2007-09-19 
10:00:18.000000000 +0800
@@ -2,7 +2,7 @@
                     ----------------------------
 
                    H. Peter Anvin <[EMAIL PROTECTED]>
-                       Last update 2007-05-23
+                       Last update 2007-09-18
 
 On the i386 platform, the Linux kernel uses a rather complicated boot
 convention.  This has evolved partially due to historical aspects, as
@@ -42,6 +42,9 @@
 Protocol 2.06: (Kernel 2.6.22) Added a field that contains the size of
                the boot command line
 
+Protocol 2.07: (kernel 2.6.23) Added a field of 64-bit physical
+               pointer to single linked list of struct setup_data.
+               Added 32-bit boot protocol.
 
 **** MEMORY LAYOUT
 
@@ -168,6 +171,9 @@
 0234/1 2.05+   relocatable_kernel Whether kernel is relocatable or not
 0235/3 N/A     pad2            Unused
 0238/4 2.06+   cmdline_size    Maximum size of the kernel command line
+023c/4 N/A     pad3            Unused
+0240/8 2.07+   setup_data      64-bit physical pointer to linked list
+                               of struct setup_data
 
 (1) For backwards compatibility, if the setup_sects field contains 0, the
     real value is 4.
@@ -480,6 +486,36 @@
   cmdline_size characters. With protocol version 2.05 and earlier, the
   maximum size was 255.
 
+Field name:    setup_data
+Type:          write (obligatory)
+Offset/size:   0x240/8
+Protocol:      2.07+
+
+  The 64-bit physical pointer to NULL terminated single linked list of
+  struct setup_data. This is used to define a more extensible boot
+  parameters passing mechanism. The definition of struct setup_data is
+  as follow:
+
+  struct setup_data {
+         u64 next;
+         u32 type;
+         u32 len;
+         u8  data[0];
+  } __attribute__((packed));
+
+  Where, the next is a 64-bit physical pointer to the next node of
+  linked list, the next field of the last node is 0; the type is used
+  to identify the contents of data; the len is the length of data
+  field; the data holds the real payload.
+
+  With this field, to add a new boot parameter written by bootloader,
+  it is not needed to add a new field to real mode header, just add a
+  new setup_data type is sufficient. But to add a new boot parameter
+  read by bootloader, it is still needed to add a new field.
+
+  TODO: Where is the safe place to place the linked list of struct
+       setup_data?
+
 
 **** THE KERNEL COMMAND LINE
 
@@ -753,3 +789,35 @@
        After completing your hook, you should jump to the address
        that was in this field before your boot loader overwrote it
        (relocated, if appropriate.)
+
+
+**** SETUP DATA TYPES
+
+
+**** 32-bit BOOT PROTOCOL
+
+For machine with some new BIOS other than legacy BIOS, such as EFI,
+LinuxBIOS, etc, and kexec, the 16-bit real mode setup code in kernel
+based on legacy BIOS can not be used, so a 32-bit boot protocol need
+to be defined.
+
+In 32-bit boot protocol, the first step in loading a Linux kernel
+should still be to load the real-mode code and then examine the kernel
+header at offset 0x01f1. But, it is not necessary to load all
+real-mode code, just first 4K bytes traditionally known as "zero page"
+is needed.
+
+In addition to read/modify/write kernel header of the zero page as
+that of 16-bit boot protocol, the boot loader should also fill the
+additional fields of the zero page as that described in zero-page.txt.
+
+After loading and setuping the zero page, the boot loader can load the
+32/64-bit kernel in the same way as that of 16-bit boot protocol.
+
+In 32-bit boot protocol, the kernel is started by jumping to the
+32-bit kernel entry point, which is the start address of loaded
+32/64-bit kernel.
+
+At entry, the CPU must be in 32-bit protected mode with paging
+disabled; the CS and DS must be 4G flat segments; %esi holds the base
+address of the "zero page"; %esp, %ebp, %edi should be zero.
Index: linux-2.6.23-rc6/Documentation/i386/zero-page.txt
===================================================================
--- linux-2.6.23-rc6.orig/Documentation/i386/zero-page.txt      2007-09-11 
10:50:29.000000000 +0800
+++ linux-2.6.23-rc6/Documentation/i386/zero-page.txt   2007-09-19 
10:00:18.000000000 +0800
@@ -1,99 +1,28 @@
----------------------------------------------------------------------------
-!!!!!!!!!!!!!!!WARNING!!!!!!!!
-The zero page is a kernel internal data structure, not a stable ABI.  It might 
change
-without warning and the kernel has no way to detect old version of it.
-If you're writing some external code like a boot loader you should only use
-the stable versioned real mode boot protocol described in boot.txt. Otherwise 
the kernel
-might break you at any time.
-!!!!!!!!!!!!!WARNING!!!!!!!!!!!
-----------------------------------------------------------------------------
-
-Summary of boot_params layout (kernel point of view)
-     ( collected by Hans Lermen and Martin Mares )
- 
-The contents of boot_params are used to pass parameters from the
-16-bit realmode code of the kernel to the 32-bit part. References/settings
-to it mainly are in:
-
-  arch/i386/boot/setup.S
-  arch/i386/boot/video.S
-  arch/i386/kernel/head.S
-  arch/i386/kernel/setup.c
- 
-
-Offset Type            Description
-------  ----           -----------
-    0  32 bytes        struct screen_info, SCREEN_INFO
-                       ATTENTION, overlaps the following !!!
-    2  unsigned short  EXT_MEM_K, extended memory size in Kb (from int 0x15)
- 0x20  unsigned short  CL_MAGIC, commandline magic number (=0xA33F)
- 0x22  unsigned short  CL_OFFSET, commandline offset
-                       Address of commandline is calculated:
-                         0x90000 + contents of CL_OFFSET
-                       (only taken, when CL_MAGIC = 0xA33F)
- 0x40  20 bytes        struct apm_bios_info, APM_BIOS_INFO
- 0x60  16 bytes        Intel SpeedStep (IST) BIOS support information
- 0x80  16 bytes        hd0-disk-parameter from intvector 0x41
- 0x90  16 bytes        hd1-disk-parameter from intvector 0x46
-
- 0xa0  16 bytes        System description table truncated to 16 bytes.
-                       ( struct sys_desc_table_struct )
- 0xb0 - 0x13f          Free. Add more parameters here if you really need them.
- 0x140- 0x1be          EDID_INFO Video mode setup
-
-0x1c4  unsigned long   EFI system table pointer
-0x1c8  unsigned long   EFI memory descriptor size
-0x1cc  unsigned long   EFI memory descriptor version
-0x1d0  unsigned long   EFI memory descriptor map pointer
-0x1d4  unsigned long   EFI memory descriptor map size
-0x1e0  unsigned long   ALT_MEM_K, alternative mem check, in Kb
-0x1e4  unsigned long   Scratch field for the kernel setup code
-0x1e8  char            number of entries in E820MAP (below)
-0x1e9  unsigned char   number of entries in EDDBUF (below)
-0x1ea  unsigned char   number of entries in EDD_MBR_SIG_BUFFER (below)
-0x1f1  char            size of setup.S, number of sectors
-0x1f2  unsigned short  MOUNT_ROOT_RDONLY (if !=0)
-0x1f4  unsigned short  size of compressed kernel-part in the
-                       (b)zImage-file (in 16 byte units, rounded up)
-0x1f6  unsigned short  swap_dev (unused AFAIK)
-0x1f8  unsigned short  RAMDISK_FLAGS
-0x1fa  unsigned short  VGA-Mode (old one)
-0x1fc  unsigned short  ORIG_ROOT_DEV (high=Major, low=minor)
-0x1ff  char            AUX_DEVICE_INFO
-
-0x200  short jump to start of setup code aka "reserved" field.
-0x202  4 bytes         Signature for SETUP-header, ="HdrS"
-0x206  unsigned short  Version number of header format
-                       Current version is 0x0201...
-0x208  8 bytes         (used by setup.S for communication with boot loaders,
-                        look there)
-0x210  char            LOADER_TYPE, = 0, old one
-                       else it is set by the loader:
-                       0xTV: T=0 for LILO
-                               1 for Loadlin
-                               2 for bootsect-loader
-                               3 for SYSLINUX
-                               4 for ETHERBOOT
-                               5 for ELILO
-                               7 for GRuB
-                               8 for U-BOOT
-                               9 for Xen
-                               V = version
-0x211  char            loadflags:
-                       bit0 = 1: kernel is loaded high (bzImage)
-                       bit7 = 1: Heap and pointer (see below) set by boot
-                                 loader.
-0x212  unsigned short  (setup.S)
-0x214  unsigned long   KERNEL_START, where the loader started the kernel
-0x218  unsigned long   INITRD_START, address of loaded ramdisk image
-0x21c  unsigned long   INITRD_SIZE, size in bytes of ramdisk image
-0x220  4 bytes         (setup.S)
-0x224  unsigned short  setup.S heap end pointer
-0x226   unsigned short zero_pad
-0x228   unsigned long  cmd_line_ptr
-0x22c   unsigned long  ramdisk_max
-0x230   16 bytes       trampoline
-0x290 - 0x2cf          EDD_MBR_SIG_BUFFER (edd.S)
-0x2d0 - 0xd00          E820MAP
-0xd00 - 0xeff          EDDBUF (edd.S) for disk signature read sector
-0xd00 - 0xeeb          EDDBUF (edd.S) for edd data
+The additional fields in zero page as a part of 32-bit boot protocol
+of kernel. These should be filled by bootloader or 16-bit real-mode
+code of the kernel. References/settings to it mainly are in:
+
+  include/asm-i386/bootparam.h
+
+
+Offset Proto   Name            Meaning
+/Size
+
+000/040        2.07+   screen_info     Text mode or frame buffer information
+                               (struct screen_info)
+040/014        2.07+   apm_bios_info   APM BIOS information (struct 
apm_bios_info)
+060/010        2.07+   ist_info        Intel SpeedStep (IST) BIOS support 
information
+                               (struct ist_info)
+0A0/010        2.07+   sys_desc_table  System description table (struct 
sys_desc_table)
+140/080        2.07+   edid_info       Video mode setup (struct edid_info)
+1C0/020        2.07+   efi_info        EFI 32 information (struct efi_info)
+1E0/004        2.07+   alk_mem_k       Alternative mem check, in KB
+1E4/004        2.07+   scratch         Scratch field for the kernel setup code
+1E8/001        2.07+   e820_entries    Number of entries in e820_map (below)
+1E9/001        2.07+   eddbuf_entries  Number of entries in eddbuf (below)
+1EA/001        2.07+   edd_mbr_sig_buf_entries Number of entries in 
edd_mbr_sig_buffer
+                               (below)
+290/040        2.07+   edd_mbr_sig_buffer EDD MBR signatures
+2D0/A00        2.07+   e820_map        E820 memory map table
+                               (array of struct e820entry)
+D00/1EC        2.07+   eddbuf          EDD data (array of struct edd_info)
-
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