This patch defines a 32-bit boot protocol and adds corresponding
document.
Signed-off-by: Huang Ying <[email protected]>
---
boot.txt | 105 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 104 insertions(+), 1 deletion(-)
Index: linux-2.6.23-rc4/Documentation/i386/boot.txt
===================================================================
--- linux-2.6.23-rc4.orig/Documentation/i386/boot.txt 2007-09-17 11:22:32.000000000 +0800
+++ linux-2.6.23-rc4/Documentation/i386/boot.txt 2007-09-17 11:34:10.000000000 +0800
@@ -2,7 +2,7 @@
----------------------------
H. Peter Anvin <[email protected]>
- Last update 2007-05-23
+ Last update 2007-09-14
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 +789,70 @@
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 fill the
+following additional fields of the zero page too.
+
+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)
+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
+
+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.
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