2005-04-16 16:20:36 -06:00
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Summary of boot_params layout (kernel point of view)
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( collected by Hans Lermen and Martin Mares )
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The contents of boot_params are used to pass parameters from the
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16-bit realmode code of the kernel to the 32-bit part. References/settings
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to it mainly are in:
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arch/i386/boot/setup.S
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arch/i386/boot/video.S
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arch/i386/kernel/head.S
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arch/i386/kernel/setup.c
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Offset Type Description
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------ ---- -----------
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0 32 bytes struct screen_info, SCREEN_INFO
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ATTENTION, overlaps the following !!!
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2 unsigned short EXT_MEM_K, extended memory size in Kb (from int 0x15)
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0x20 unsigned short CL_MAGIC, commandline magic number (=0xA33F)
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0x22 unsigned short CL_OFFSET, commandline offset
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Address of commandline is calculated:
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0x90000 + contents of CL_OFFSET
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(only taken, when CL_MAGIC = 0xA33F)
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0x40 20 bytes struct apm_bios_info, APM_BIOS_INFO
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0x60 16 bytes Intel SpeedStep (IST) BIOS support information
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0x80 16 bytes hd0-disk-parameter from intvector 0x41
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0x90 16 bytes hd1-disk-parameter from intvector 0x46
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0xa0 16 bytes System description table truncated to 16 bytes.
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( struct sys_desc_table_struct )
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0xb0 - 0x13f Free. Add more parameters here if you really need them.
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0x140- 0x1be EDID_INFO Video mode setup
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0x1c4 unsigned long EFI system table pointer
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0x1c8 unsigned long EFI memory descriptor size
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0x1cc unsigned long EFI memory descriptor version
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0x1d0 unsigned long EFI memory descriptor map pointer
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0x1d4 unsigned long EFI memory descriptor map size
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0x1e0 unsigned long ALT_MEM_K, alternative mem check, in Kb
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0x1e8 char number of entries in E820MAP (below)
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0x1e9 unsigned char number of entries in EDDBUF (below)
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0x1ea unsigned char number of entries in EDD_MBR_SIG_BUFFER (below)
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0x1f1 char size of setup.S, number of sectors
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0x1f2 unsigned short MOUNT_ROOT_RDONLY (if !=0)
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0x1f4 unsigned short size of compressed kernel-part in the
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(b)zImage-file (in 16 byte units, rounded up)
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0x1f6 unsigned short swap_dev (unused AFAIK)
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0x1f8 unsigned short RAMDISK_FLAGS
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0x1fa unsigned short VGA-Mode (old one)
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0x1fc unsigned short ORIG_ROOT_DEV (high=Major, low=minor)
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0x1ff char AUX_DEVICE_INFO
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0x200 short jump to start of setup code aka "reserved" field.
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0x202 4 bytes Signature for SETUP-header, ="HdrS"
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0x206 unsigned short Version number of header format
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Current version is 0x0201...
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0x208 8 bytes (used by setup.S for communication with boot loaders,
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look there)
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0x210 char LOADER_TYPE, = 0, old one
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else it is set by the loader:
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0xTV: T=0 for LILO
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1 for Loadlin
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2 for bootsect-loader
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3 for SYSLINUX
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4 for ETHERBOOT
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V = version
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0x211 char loadflags:
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bit0 = 1: kernel is loaded high (bzImage)
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bit7 = 1: Heap and pointer (see below) set by boot
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loader.
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0x212 unsigned short (setup.S)
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0x214 unsigned long KERNEL_START, where the loader started the kernel
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0x218 unsigned long INITRD_START, address of loaded ramdisk image
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0x21c unsigned long INITRD_SIZE, size in bytes of ramdisk image
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0x220 4 bytes (setup.S)
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0x224 unsigned short setup.S heap end pointer
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0x226 unsigned short zero_pad
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0x228 unsigned long cmd_line_ptr
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0x22c unsigned long ramdisk_max
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0x230 16 bytes trampoline
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0x290 - 0x2cf EDD_MBR_SIG_BUFFER (edd.S)
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2005-05-01 09:58:51 -06:00
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0x2d0 - 0xd00 E820MAP
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0xd00 - 0xeff EDDBUF (edd.S) for disk signature read sector
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0xd00 - 0xeeb EDDBUF (edd.S) for edd data
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