Merge branch 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jgarzi...

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

diff --git a/Documentation/i386/boot.txt b/Documentation/i386/boot.txt
index 35985b34d5a6cc194e48ce9281bac676a959dcba..fc49b79bc1ab3341b16fe19ea49402f9fd1955e2 100644 (file)
--- a/Documentation/i386/boot.txt
+++ b/Documentation/i386/boot.txt
@@ -168,6 +168,8 @@ Offset      Proto   Name            Meaning
 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
 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 2.07+   hardware_subarch Hardware subarchitecture
+0240/8 2.07+   hardware_subarch_data Subarchitecture-specific data

 
 (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.


@@ -204,7 +206,7 @@ boot loaders can ignore those fields.
 
 The byte order of all fields is littleendian (this is x86, after all.)
 
 
 The byte order of all fields is littleendian (this is x86, after all.)
 

-Field name:    setup_secs
+Field name:    setup_sects

 Type:          read
 Offset/size:   0x1f1/1
 Protocol:      ALL
 Type:          read
 Offset/size:   0x1f1/1
 Protocol:      ALL


@@ -356,6 +358,13 @@ Protocol:  2.00+
        - If 0, the protected-mode code is loaded at 0x10000.
        - If 1, the protected-mode code is loaded at 0x100000.
 
        - If 0, the protected-mode code is loaded at 0x10000.
        - If 1, the protected-mode code is loaded at 0x100000.
 

+  Bit 6 (write): KEEP_SEGMENTS
+       Protocol: 2.07+
+       - if 0, reload the segment registers in the 32bit entry point.
+       - if 1, do not reload the segment registers in the 32bit entry point.
+               Assume that %cs %ds %ss %es are all set to flat segments with
+               a base of 0 (or the equivalent for their environment).
+

   Bit 7 (write): CAN_USE_HEAP
        Set this bit to 1 to indicate that the value entered in the
        heap_end_ptr is valid.  If this field is clear, some setup code
   Bit 7 (write): CAN_USE_HEAP
        Set this bit to 1 to indicate that the value entered in the
        heap_end_ptr is valid.  If this field is clear, some setup code


@@ -480,6 +489,29 @@ Protocol:  2.06+
   cmdline_size characters. With protocol version 2.05 and earlier, the
   maximum size was 255.
 
   cmdline_size characters. With protocol version 2.05 and earlier, the
   maximum size was 255.
 

+Field name:    hardware_subarch
+Type:          write
+Offset/size:   0x23c/4
+Protocol:      2.07+
+
+  In a paravirtualized environment the hardware low level architectural
+  pieces such as interrupt handling, page table handling, and
+  accessing process control registers needs to be done differently.
+
+  This field allows the bootloader to inform the kernel we are in one
+  one of those environments.
+
+  0x00000000   The default x86/PC environment
+  0x00000001   lguest
+  0x00000002   Xen
+
+Field name:    hardware_subarch_data
+Type:          write
+Offset/size:   0x240/8
+Protocol:      2.07+
+
+  A pointer to data that is specific to hardware subarch
+

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


@@ -753,3 +785,41 @@ 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.