and KEEP_SEGMENTS flag in load_flags.
Protocol 2.08: (Kernel 2.6.26) Added crc32 checksum and ELF format
- payload. Introduced payload_offset and payload length
+ payload. Introduced payload_offset and payload_length
fields to aid in locating the payload.
Protocol 2.09: (Kernel 2.6.26) Added a field of 64-bit physical
pointer to single linked list of struct setup_data.
+Protocol 2.10: (Kernel 2.6.31) Added a protocol for relaxed alignment
+ beyond the kernel_alignment added, new init_size and
+ pref_address fields. Added extended boot loader IDs.
+
**** MEMORY LAYOUT
The traditional memory map for the kernel loader, used for Image or
0202/4 2.00+ header Magic signature "HdrS"
0206/2 2.00+ version Boot protocol version supported
0208/4 2.00+ realmode_swtch Boot loader hook (see below)
-020C/2 2.00+ start_sys The load-low segment (0x1000) (obsolete)
+020C/2 2.00+ start_sys_seg The load-low segment (0x1000) (obsolete)
020E/2 2.00+ kernel_version Pointer to kernel version string
0210/1 2.00+ type_of_loader Boot loader identifier
0211/1 2.00+ loadflags Boot protocol option flags
021C/4 2.00+ ramdisk_size initrd size (set by boot loader)
0220/4 2.00+ bootsect_kludge DO NOT USE - for bootsect.S use only
0224/2 2.01+ heap_end_ptr Free memory after setup end
-0226/2 N/A pad1 Unused
+0226/1 2.02+(3 ext_loader_ver Extended boot loader version
+0227/1 2.02+(3 ext_loader_type Extended boot loader ID
0228/4 2.02+ cmd_line_ptr 32-bit pointer to the kernel command line
-022C/4 2.03+ initrd_addr_max Highest legal initrd address
+022C/4 2.03+ ramdisk_max Highest legal initrd address
0230/4 2.05+ kernel_alignment Physical addr alignment required for kernel
0234/1 2.05+ relocatable_kernel Whether kernel is relocatable or not
-0235/3 N/A pad2 Unused
+0235/1 2.10+ min_alignment Minimum alignment, as a power of two
+0236/2 N/A pad3 Unused
0238/4 2.06+ cmdline_size Maximum size of the kernel command line
023C/4 2.07+ hardware_subarch Hardware subarchitecture
0240/8 2.07+ hardware_subarch_data Subarchitecture-specific data
024C/4 2.08+ payload_length Length of kernel payload
0250/8 2.09+ setup_data 64-bit physical pointer to linked list
of struct setup_data
+0258/8 2.10+ pref_address Preferred loading address
+0260/4 2.10+ init_size Linear memory required during initialization
(1) For backwards compatibility, if the setup_sects field contains 0, the
real value is 4.
field are unusable, which means the size of a bzImage kernel
cannot be determined.
+(3) Ignored, but safe to set, for boot protocols 2.02-2.09.
+
If the "HdrS" (0x53726448) magic number is not found at offset 0x202,
the boot protocol version is "old". Loading an old kernel, the
following parameters should be assumed:
e.g. 0x0204 for version 2.04, and 0x0a11 for a hypothetical version
10.17.
-Field name: readmode_swtch
+Field name: realmode_swtch
Type: modify (optional)
Offset/size: 0x208/4
Protocol: 2.00+
Boot loader hook (see ADVANCED BOOT LOADER HOOKS below.)
-Field name: start_sys
+Field name: start_sys_seg
Type: read
-Offset/size: 0x20c/4
+Offset/size: 0x20c/2
Protocol: 2.00+
The load low segment (0x1000). Obsolete.
0xTV here, where T is an identifier for the boot loader and V is
a version number. Otherwise, enter 0xFF here.
+ For boot loader IDs above T = 0xD, write T = 0xE to this field and
+ write the extended ID minus 0x10 to the ext_loader_type field.
+ Similarly, the ext_loader_ver field can be used to provide more than
+ four bits for the bootloader version.
+
+ For example, for T = 0x15, V = 0x234, write:
+
+ type_of_loader <- 0xE4
+ ext_loader_type <- 0x05
+ ext_loader_ver <- 0x23
+
Assigned boot loader ids:
0 LILO (0x00 reserved for pre-2.00 bootloader)
1 Loadlin
2 bootsect-loader (0x20, all other values reserved)
- 3 SYSLINUX
- 4 EtherBoot
+ 3 Syslinux
+ 4 Etherboot/gPXE
5 ELILO
- 7 GRuB
- 8 U-BOOT
+ 7 GRUB
+ 8 U-Boot
9 Xen
A Gujin
B Qemu
+ C Arcturus Networks uCbootloader
+ E Extended (see ext_loader_type)
+ F Special (0xFF = undefined)
Please contact <hpa@zytor.com> if you need a bootloader ID
value assigned.
Set this field to the offset (from the beginning of the real-mode
code) of the end of the setup stack/heap, minus 0x0200.
+Field name: ext_loader_ver
+Type: write (optional)
+Offset/size: 0x226/1
+Protocol: 2.02+
+
+ This field is used as an extension of the version number in the
+ type_of_loader field. The total version number is considered to be
+ (type_of_loader & 0x0f) + (ext_loader_ver << 4).
+
+ The use of this field is boot loader specific. If not written, it
+ is zero.
+
+ Kernels prior to 2.6.31 did not recognize this field, but it is safe
+ to write for protocol version 2.02 or higher.
+
+Field name: ext_loader_type
+Type: write (obligatory if (type_of_loader & 0xf0) == 0xe0)
+Offset/size: 0x227/1
+Protocol: 2.02+
+
+ This field is used as an extension of the type number in
+ type_of_loader field. If the type in type_of_loader is 0xE, then
+ the actual type is (ext_loader_type + 0x10).
+
+ This field is ignored if the type in type_of_loader is not 0xE.
+
+ Kernels prior to 2.6.31 did not recognize this field, but it is safe
+ to write for protocol version 2.02 or higher.
+
Field name: cmd_line_ptr
Type: write (obligatory)
Offset/size: 0x228/4
zero, the kernel will assume that your boot loader does not support
the 2.02+ protocol.
-Field name: initrd_addr_max
+Field name: ramdisk_max
Type: read
Offset/size: 0x22c/4
Protocol: 2.03+
0x37FFFFFF, you can start your ramdisk at 0x37FE0000.)
Field name: kernel_alignment
-Type: read (reloc)
+Type: read/modify (reloc)
Offset/size: 0x230/4
-Protocol: 2.05+
+Protocol: 2.05+ (read), 2.10+ (modify)
+
+ Alignment unit required by the kernel (if relocatable_kernel is
+ true.) A relocatable kernel that is loaded at an alignment
+ incompatible with the value in this field will be realigned during
+ kernel initialization.
- Alignment unit required by the kernel (if relocatable_kernel is true.)
+ Starting with protocol version 2.10, this reflects the kernel
+ alignment preferred for optimal performance; it is possible for the
+ loader to modify this field to permit a lesser alignment. See the
+ min_alignment and pref_address field below.
Field name: relocatable_kernel
Type: read (reloc)
After loading, the boot loader must set the code32_start field to
point to the loaded code, or to a boot loader hook.
+Field name: min_alignment
+Type: read (reloc)
+Offset/size: 0x235/1
+Protocol: 2.10+
+
+ This field, if nonzero, indicates as a power of two the minimum
+ alignment required, as opposed to preferred, by the kernel to boot.
+ If a boot loader makes use of this field, it should update the
+ kernel_alignment field with the alignment unit desired; typically:
+
+ kernel_alignment = 1 << min_alignment
+
+ There may be a considerable performance cost with an excessively
+ misaligned kernel. Therefore, a loader should typically try each
+ power-of-two alignment from kernel_alignment down to this alignment.
+
Field name: cmdline_size
Type: read
Offset/size: 0x238/4
0x00000000 The default x86/PC environment
0x00000001 lguest
0x00000002 Xen
+ 0x00000003 Moorestown MID
Field name: hardware_subarch_data
Type: write (subarch-dependent)
Offset/size: 0x248/4
Protocol: 2.08+
- If non-zero then this field contains the offset from the end of the
- real-mode code to the payload.
+ If non-zero then this field contains the offset from the beginning
+ of the protected-mode code to the payload.
The payload may be compressed. The format of both the compressed and
uncompressed data should be determined using the standard magic
- numbers. Currently only gzip compressed ELF is used.
+ numbers. The currently supported compression formats are gzip
+ (magic numbers 1F 8B or 1F 9E), bzip2 (magic number 42 5A) and LZMA
+ (magic number 5D 00). The uncompressed payload is currently always ELF
+ (magic number 7F 45 4C 46).
Field name: payload_length
Type: read
sure to consider the case where the linked list already contains
entries.
+Field name: pref_address
+Type: read (reloc)
+Offset/size: 0x258/8
+Protocol: 2.10+
+
+ This field, if nonzero, represents a preferred load address for the
+ kernel. A relocating bootloader should attempt to load at this
+ address if possible.
+
+ A non-relocatable kernel will unconditionally move itself and to run
+ at this address.
+
+Field name: init_size
+Type: read
+Offset/size: 0x25c/4
+
+ This field indicates the amount of linear contiguous memory starting
+ at the kernel runtime start address that the kernel needs before it
+ is capable of examining its memory map. This is not the same thing
+ as the total amount of memory the kernel needs to boot, but it can
+ be used by a relocating boot loader to help select a safe load
+ address for the kernel.
+
+ The kernel runtime start address is determined by the following algorithm:
+
+ if (relocatable_kernel)
+ runtime_start = align_up(load_address, kernel_alignment)
+ else
+ runtime_start = pref_address
+
**** THE IMAGE CHECKSUM
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff