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1--------------------------------------------------------------------------- 1The additional fields in struct boot_params as a part of 32-bit boot
2!!!!!!!!!!!!!!!WARNING!!!!!!!! 2protocol of kernel. These should be filled by bootloader or 16-bit
3The zero page is a kernel internal data structure, not a stable ABI. It might change 3real-mode setup code of the kernel. References/settings to it mainly
4without warning and the kernel has no way to detect old version of it. 4are in:
5If you're writing some external code like a boot loader you should only use
6the stable versioned real mode boot protocol described in boot.txt. Otherwise the kernel
7might break you at any time.
8!!!!!!!!!!!!!WARNING!!!!!!!!!!!
9----------------------------------------------------------------------------
10 5
11Summary of boot_params layout (kernel point of view) 6 include/asm-x86/bootparam.h
12 ( collected by Hans Lermen and Martin Mares )
13
14The contents of boot_params are used to pass parameters from the
1516-bit realmode code of the kernel to the 32-bit part. References/settings
16to it mainly are in:
17 7
18 arch/i386/boot/setup.S
19 arch/i386/boot/video.S
20 arch/i386/kernel/head.S
21 arch/i386/kernel/setup.c
22
23 8
24Offset Type Description 9Offset Proto Name Meaning
25------ ---- ----------- 10/Size
26 0 32 bytes struct screen_info, SCREEN_INFO
27 ATTENTION, overlaps the following !!!
28 2 unsigned short EXT_MEM_K, extended memory size in Kb (from int 0x15)
29 0x20 unsigned short CL_MAGIC, commandline magic number (=0xA33F)
30 0x22 unsigned short CL_OFFSET, commandline offset
31 Address of commandline is calculated:
32 0x90000 + contents of CL_OFFSET
33 (only taken, when CL_MAGIC = 0xA33F)
34 0x40 20 bytes struct apm_bios_info, APM_BIOS_INFO
35 0x60 16 bytes Intel SpeedStep (IST) BIOS support information
36 0x80 16 bytes hd0-disk-parameter from intvector 0x41
37 0x90 16 bytes hd1-disk-parameter from intvector 0x46
38 11
39 0xa0 16 bytes System description table truncated to 16 bytes. 12000/040 ALL screen_info Text mode or frame buffer information
40 ( struct sys_desc_table_struct ) 13 (struct screen_info)
41 0xb0 - 0x13f Free. Add more parameters here if you really need them. 14040/014 ALL apm_bios_info APM BIOS information (struct apm_bios_info)
42 0x140- 0x1be EDID_INFO Video mode setup 15060/010 ALL ist_info Intel SpeedStep (IST) BIOS support information
43 16 (struct ist_info)
440x1c4 unsigned long EFI system table pointer 17080/010 ALL hd0_info hd0 disk parameter, OBSOLETE!!
450x1c8 unsigned long EFI memory descriptor size 18090/010 ALL hd1_info hd1 disk parameter, OBSOLETE!!
460x1cc unsigned long EFI memory descriptor version 190A0/010 ALL sys_desc_table System description table (struct sys_desc_table)
470x1d0 unsigned long EFI memory descriptor map pointer 20140/080 ALL edid_info Video mode setup (struct edid_info)
480x1d4 unsigned long EFI memory descriptor map size 211C0/020 ALL efi_info EFI 32 information (struct efi_info)
490x1e0 unsigned long ALT_MEM_K, alternative mem check, in Kb 221E0/004 ALL alk_mem_k Alternative mem check, in KB
500x1e4 unsigned long Scratch field for the kernel setup code 231E4/004 ALL scratch Scratch field for the kernel setup code
510x1e8 char number of entries in E820MAP (below) 241E8/001 ALL e820_entries Number of entries in e820_map (below)
520x1e9 unsigned char number of entries in EDDBUF (below) 251E9/001 ALL eddbuf_entries Number of entries in eddbuf (below)
530x1ea unsigned char number of entries in EDD_MBR_SIG_BUFFER (below) 261EA/001 ALL edd_mbr_sig_buf_entries Number of entries in edd_mbr_sig_buffer
540x1f1 char size of setup.S, number of sectors 27 (below)
550x1f2 unsigned short MOUNT_ROOT_RDONLY (if !=0) 28290/040 ALL edd_mbr_sig_buffer EDD MBR signatures
560x1f4 unsigned short size of compressed kernel-part in the 292D0/A00 ALL e820_map E820 memory map table
57 (b)zImage-file (in 16 byte units, rounded up) 30 (array of struct e820entry)
580x1f6 unsigned short swap_dev (unused AFAIK) 31D00/1EC ALL eddbuf EDD data (array of struct edd_info)
590x1f8 unsigned short RAMDISK_FLAGS
600x1fa unsigned short VGA-Mode (old one)
610x1fc unsigned short ORIG_ROOT_DEV (high=Major, low=minor)
620x1ff char AUX_DEVICE_INFO
63
640x200 short jump to start of setup code aka "reserved" field.
650x202 4 bytes Signature for SETUP-header, ="HdrS"
660x206 unsigned short Version number of header format
67 Current version is 0x0201...
680x208 8 bytes (used by setup.S for communication with boot loaders,
69 look there)
700x210 char LOADER_TYPE, = 0, old one
71 else it is set by the loader:
72 0xTV: T=0 for LILO
73 1 for Loadlin
74 2 for bootsect-loader
75 3 for SYSLINUX
76 4 for ETHERBOOT
77 5 for ELILO
78 7 for GRuB
79 8 for U-BOOT
80 9 for Xen
81 V = version
820x211 char loadflags:
83 bit0 = 1: kernel is loaded high (bzImage)
84 bit7 = 1: Heap and pointer (see below) set by boot
85 loader.
860x212 unsigned short (setup.S)
870x214 unsigned long KERNEL_START, where the loader started the kernel
880x218 unsigned long INITRD_START, address of loaded ramdisk image
890x21c unsigned long INITRD_SIZE, size in bytes of ramdisk image
900x220 4 bytes (setup.S)
910x224 unsigned short setup.S heap end pointer
920x226 unsigned short zero_pad
930x228 unsigned long cmd_line_ptr
940x22c unsigned long ramdisk_max
950x230 16 bytes trampoline
960x290 - 0x2cf EDD_MBR_SIG_BUFFER (edd.S)
970x2d0 - 0xd00 E820MAP
980xd00 - 0xeff EDDBUF (edd.S) for disk signature read sector
990xd00 - 0xeeb EDDBUF (edd.S) for edd data