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Mentioned GRUB2 Boot Info in boot_sectors.txt

release-1.5.4.branch
Thomas Schmitt 8 years ago
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6baeae70e0
  1. 35
      doc/boot_sectors.txt

35
doc/boot_sectors.txt

@ -15,6 +15,8 @@ specifications, some is just rumor which happens to work (maybe not even that).
EL Torito CD booting, for PC-BIOS x86, PowerPC, (old) Mac, EFI.
Boot Info Table and GRUB2 Boot Info
Master Boot Record (MBR), for PC-BIOS x86 from (pseudo-) hard disk
Apple Partition Map (APM), for more modern Mac
@ -48,7 +50,6 @@ Sources:
El Torito, Bootable CD-ROM Format Specification, Version 1.0, 1995
which refers to ECMA-119, the standard for ISO 9660 filesystems.
libisofs/eltorito.[ch] by Vreixo Formoso.
man mkisofs by Joerg Schilling.
ECMA-119 prescribes that the first 32 kB of an ISO 9660 image are System Area
@ -237,10 +238,22 @@ Byte Range | Value | Meaning
12 - 31 | sel_crit | "Vendor unique selection criteria."
---------- | ---------- | ----------------------------------------------------
------------------------------------------------------------------------------
Boot Info Table and GRUB2 Boot Info
Sources:
man mkisofs by Joerg Schilling
Mail conversations with Vladimir Serbinenko.
The boot image file content is mostly opaque to the ISO 9660 image generator.
Nevertheless there is a tradition named "Boot Info Table" which prescribes
to write information into byte fields of the boot image file content.
Recent versions of GRUB2 expect a similar patching which has no name yet.
For now let's call it "GRUB2 Boot Info"
There are no general means known how a producer of ISO 9660 images could
detect the need for Boot Info Table production.
It rather needs a hint from the user who has to know whether the boot image
@ -249,19 +262,31 @@ The Boot Info Table begins at byte 8 of the boot image content.
Byte Range | Value | Meaning
---------- | ---------- | ----------------------------------------------------
8 - 11 | pvd_lba | Block address of the Primary Volume Descriptor
8 - 11 | pvd_lba | Block address of the Primary Volume Descriptor.
| | This is the session start LBA + 16.
| |
12 - 15 | file_lba | Block address of the start of the boot image file
| | content.
| | content. Block size is 2048.
| |
16 - 19 | file_len | Number of bytes in boot image file content.
| |
20 - 23 | checksum | Little-endian: The sum of all 32-bit words of the
| | file content from byte 64 to file end.
20 - 23 | checksum | The sum of all 32-bit words of the file content
| | from byte 64 to file end.
| |
24 - 63 | 0 | Reserved
---------- | ---------- | ----------------------------------------------------
All numbers are stored little-endian.
GRUB2 Boot Info represents a particular block address inside the boot image.
It may well be combined with Boot Info Table. See GRUB2 script grub-mkrescue
use of xorrisofs options -boot-info-table and --grub2-boot-info.
Byte Range | Value | Meaning
---------- | ---------- | ----------------------------------------------------
2548 -2555 | grub2_adr | Block address of the start of the boot image file
| | content plus 5. Block size is 512.
| | 64 bit Little-endian.
---------- | ---------- | ----------------------------------------------------
------------------------------------------------------------------------------

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