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Diffstat (limited to 'Documentation/i386/zero-page.txt')
| -rw-r--r-- | Documentation/i386/zero-page.txt | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/Documentation/i386/zero-page.txt b/Documentation/i386/zero-page.txt new file mode 100644 index 000000000000..67c053a099ed --- /dev/null +++ b/Documentation/i386/zero-page.txt @@ -0,0 +1,84 @@ +Summary of boot_params layout (kernel point of view) + ( collected by Hans Lermen and Martin Mares ) + +The contents of boot_params are used to pass parameters from the +16-bit realmode code of the kernel to the 32-bit part. References/settings +to it mainly are in: + + arch/i386/boot/setup.S + arch/i386/boot/video.S + arch/i386/kernel/head.S + arch/i386/kernel/setup.c + + +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 +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) +0x1f1 char size of setup.S, number of sectors +0x1f2 unsigned short MOUNT_ROOT_RDONLY (if !=0) +0x1f4 unsigned short size of compressed kernel-part in the + (b)zImage-file (in 16 byte units, rounded up) +0x1f6 unsigned short swap_dev (unused AFAIK) +0x1f8 unsigned short RAMDISK_FLAGS +0x1fa unsigned short VGA-Mode (old one) +0x1fc unsigned short ORIG_ROOT_DEV (high=Major, low=minor) +0x1ff char AUX_DEVICE_INFO + +0x200 short jump to start of setup code aka "reserved" field. +0x202 4 bytes Signature for SETUP-header, ="HdrS" +0x206 unsigned short Version number of header format + Current version is 0x0201... +0x208 8 bytes (used by setup.S for communication with boot loaders, + look there) +0x210 char LOADER_TYPE, = 0, old one + else it is set by the loader: + 0xTV: T=0 for LILO + 1 for Loadlin + 2 for bootsect-loader + 3 for SYSLINUX + 4 for ETHERBOOT + V = version +0x211 char loadflags: + bit0 = 1: kernel is loaded high (bzImage) + bit7 = 1: Heap and pointer (see below) set by boot + loader. +0x212 unsigned short (setup.S) +0x214 unsigned long KERNEL_START, where the loader started the kernel +0x218 unsigned long INITRD_START, address of loaded ramdisk image +0x21c unsigned long INITRD_SIZE, size in bytes of ramdisk image +0x220 4 bytes (setup.S) +0x224 unsigned short setup.S heap end pointer +0x226 unsigned short zero_pad +0x228 unsigned long cmd_line_ptr +0x22c unsigned long ramdisk_max +0x230 16 bytes trampoline +0x290 - 0x2cf EDD_MBR_SIG_BUFFER (edd.S) +0x2d0 - 0x600 E820MAP +0x600 - 0x7ff EDDBUF (edd.S) for disk signature read sector +0x600 - 0x7eb EDDBUF (edd.S) for edd data |