Messages in this thread Patch in this message | | | Subject | [RFC -mm 2/2] i386/x86_64 boot: document for 32 bit boot protocol | From | "Huang, Ying" <> | Date | Mon, 17 Sep 2007 16:26:22 +0800 |
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This patch defines a 32-bit boot protocol and adds corresponding document.
Signed-off-by: Huang Ying <ying.huang@intel.com>
---
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 <hpa@zytor.com> - 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. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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