| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | Summary of boot_params layout (kernel point of view) |
| 2 | ( collected by Hans Lermen and Martin Mares ) |
| 3 | |
| 4 | The contents of boot_params are used to pass parameters from the |
| 5 | 16-bit realmode code of the kernel to the 32-bit part. References/settings |
| 6 | to it mainly are in: |
| 7 | |
| 8 | arch/i386/boot/setup.S |
| 9 | arch/i386/boot/video.S |
| 10 | arch/i386/kernel/head.S |
| 11 | arch/i386/kernel/setup.c |
| 12 | |
| 13 | |
| 14 | Offset Type Description |
| 15 | ------ ---- ----------- |
| 16 | 0 32 bytes struct screen_info, SCREEN_INFO |
| 17 | ATTENTION, overlaps the following !!! |
| 18 | 2 unsigned short EXT_MEM_K, extended memory size in Kb (from int 0x15) |
| 19 | 0x20 unsigned short CL_MAGIC, commandline magic number (=0xA33F) |
| 20 | 0x22 unsigned short CL_OFFSET, commandline offset |
| 21 | Address of commandline is calculated: |
| 22 | 0x90000 + contents of CL_OFFSET |
| 23 | (only taken, when CL_MAGIC = 0xA33F) |
| 24 | 0x40 20 bytes struct apm_bios_info, APM_BIOS_INFO |
| 25 | 0x60 16 bytes Intel SpeedStep (IST) BIOS support information |
| 26 | 0x80 16 bytes hd0-disk-parameter from intvector 0x41 |
| 27 | 0x90 16 bytes hd1-disk-parameter from intvector 0x46 |
| 28 | |
| 29 | 0xa0 16 bytes System description table truncated to 16 bytes. |
| 30 | ( struct sys_desc_table_struct ) |
| 31 | 0xb0 - 0x13f Free. Add more parameters here if you really need them. |
| 32 | 0x140- 0x1be EDID_INFO Video mode setup |
| 33 | |
| 34 | 0x1c4 unsigned long EFI system table pointer |
| 35 | 0x1c8 unsigned long EFI memory descriptor size |
| 36 | 0x1cc unsigned long EFI memory descriptor version |
| 37 | 0x1d0 unsigned long EFI memory descriptor map pointer |
| 38 | 0x1d4 unsigned long EFI memory descriptor map size |
| 39 | 0x1e0 unsigned long ALT_MEM_K, alternative mem check, in Kb |
| H. Peter Anvin | 85414b6 | 2007-07-11 12:18:33 -0700 | [diff] [blame] | 40 | 0x1e4 unsigned long Scratch field for the kernel setup code |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 41 | 0x1e8 char number of entries in E820MAP (below) |
| 42 | 0x1e9 unsigned char number of entries in EDDBUF (below) |
| 43 | 0x1ea unsigned char number of entries in EDD_MBR_SIG_BUFFER (below) |
| 44 | 0x1f1 char size of setup.S, number of sectors |
| 45 | 0x1f2 unsigned short MOUNT_ROOT_RDONLY (if !=0) |
| 46 | 0x1f4 unsigned short size of compressed kernel-part in the |
| 47 | (b)zImage-file (in 16 byte units, rounded up) |
| 48 | 0x1f6 unsigned short swap_dev (unused AFAIK) |
| 49 | 0x1f8 unsigned short RAMDISK_FLAGS |
| 50 | 0x1fa unsigned short VGA-Mode (old one) |
| 51 | 0x1fc unsigned short ORIG_ROOT_DEV (high=Major, low=minor) |
| 52 | 0x1ff char AUX_DEVICE_INFO |
| 53 | |
| 54 | 0x200 short jump to start of setup code aka "reserved" field. |
| 55 | 0x202 4 bytes Signature for SETUP-header, ="HdrS" |
| 56 | 0x206 unsigned short Version number of header format |
| 57 | Current version is 0x0201... |
| 58 | 0x208 8 bytes (used by setup.S for communication with boot loaders, |
| 59 | look there) |
| 60 | 0x210 char LOADER_TYPE, = 0, old one |
| 61 | else it is set by the loader: |
| 62 | 0xTV: T=0 for LILO |
| 63 | 1 for Loadlin |
| 64 | 2 for bootsect-loader |
| 65 | 3 for SYSLINUX |
| 66 | 4 for ETHERBOOT |
| Jeremy Fitzhardinge | 354332e | 2006-09-12 20:35:57 -0700 | [diff] [blame] | 67 | 5 for ELILO |
| 68 | 7 for GRuB |
| 69 | 8 for U-BOOT |
| 70 | 9 for Xen |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 71 | V = version |
| 72 | 0x211 char loadflags: |
| 73 | bit0 = 1: kernel is loaded high (bzImage) |
| 74 | bit7 = 1: Heap and pointer (see below) set by boot |
| 75 | loader. |
| 76 | 0x212 unsigned short (setup.S) |
| 77 | 0x214 unsigned long KERNEL_START, where the loader started the kernel |
| 78 | 0x218 unsigned long INITRD_START, address of loaded ramdisk image |
| 79 | 0x21c unsigned long INITRD_SIZE, size in bytes of ramdisk image |
| 80 | 0x220 4 bytes (setup.S) |
| 81 | 0x224 unsigned short setup.S heap end pointer |
| 82 | 0x226 unsigned short zero_pad |
| 83 | 0x228 unsigned long cmd_line_ptr |
| 84 | 0x22c unsigned long ramdisk_max |
| 85 | 0x230 16 bytes trampoline |
| 86 | 0x290 - 0x2cf EDD_MBR_SIG_BUFFER (edd.S) |
| Venkatesh Pallipadi | f9ba705 | 2005-05-01 08:58:51 -0700 | [diff] [blame] | 87 | 0x2d0 - 0xd00 E820MAP |
| 88 | 0xd00 - 0xeff EDDBUF (edd.S) for disk signature read sector |
| 89 | 0xd00 - 0xeeb EDDBUF (edd.S) for edd data |