Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394...

[linux-2.6] / Documentation / i386 / boot.txt

diff --git a/Documentation/i386/boot.txt b/Documentation/i386/boot.txt
index 2f75e750e4f5c650a89df593ead1a1ff320eee62..2eb16100bb3fef7658799f5f7f4d259be644b537 100644 (file)
--- a/Documentation/i386/boot.txt
+++ b/Documentation/i386/boot.txt
@@ -170,6 +170,8 @@ Offset      Proto   Name            Meaning
 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
 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

+0248/4 2.08+   payload_offset  Offset of kernel payload
+024C/4 2.08+   payload_length  Length of kernel payload

 
 (1) For backwards compatibility, if the setup_sects field contains 0, the
     real value is 4.
 
 (1) For backwards compatibility, if the setup_sects field contains 0, the
     real value is 4.


@@ -512,6 +514,32 @@ Protocol:  2.07+
 
   A pointer to data that is specific to hardware subarch
 
 
   A pointer to data that is specific to hardware subarch
 

+Field name:    payload_offset
+Type:          read
+Offset/size:   0x248/4
+Protocol:      2.08+
+
+  If non-zero then this field contains the offset from the end of the
+  real-mode code to the payload.
+
+  The payload may be compressed. The format of both the compressed and
+  uncompressed data should be determined using the standard magic
+  numbers. Currently only gzip compressed ELF is used.
+  
+Field name:    payload_length
+Type:          read
+Offset/size:   0x24c/4
+Protocol:      2.08+
+
+  The length of the payload.
+
+**** THE IMAGE CHECKSUM
+
+From boot protocol version 2.08 onwards the CRC-32 is calculated over
+the entire file using the characteristic polynomial 0x04C11DB7 and an
+initial remainder of 0xffffffff.  The checksum is appended to the
+file; therefore the CRC of the file up to the limit specified in the
+syssize field of the header is always 0.

 
 **** THE KERNEL COMMAND LINE
 
 
 **** THE KERNEL COMMAND LINE
 


@@ -785,3 +813,41 @@ IMPORTANT: All the hooks are required to preserve %esp, %ebp, %esi and
        After completing your hook, you should jump to the address
        that was in this field before your boot loader overwrote it
        (relocated, if appropriate.)
        After completing your hook, you should jump to the address
        that was in this field before your boot loader overwrote it
        (relocated, if appropriate.)

+
+
+**** 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 needs
+to be defined.
+
+In 32-bit boot protocol, the first step in loading a Linux kernel
+should be to setup the boot parameters (struct boot_params,
+traditionally known as "zero page"). The memory for struct boot_params
+should be allocated and initialized to all zero. Then the setup header
+from offset 0x01f1 of kernel image on should be loaded into struct
+boot_params and examined. The end of setup header can be calculated as
+follow:
+
+       0x0202 + byte value at offset 0x0201
+
+In addition to read/modify/write the setup header of the struct
+boot_params as that of 16-bit boot protocol, the boot loader should
+also fill the additional fields of the struct boot_params as that
+described in zero-page.txt.
+
+After setupping the struct boot_params, 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; a GDT must be loaded with the descriptors for selectors
+__BOOT_CS(0x10) and __BOOT_DS(0x18); both descriptors must be 4G flat
+segment; __BOOS_CS must have execute/read permission, and __BOOT_DS
+must have read/write permission; CS must be __BOOT_CS and DS, ES, SS
+must be __BOOT_DS; interrupt must be disabled; %esi must hold the base
+address of the struct boot_params; %ebp, %edi and %ebx must be zero.