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Mentioned GRUB2 Boot Info in boot_sectors.txt

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Thomas Schmitt 2013-11-18 12:58:50 +01:00
parent b987972660
commit 6baeae70e0
1 changed files with 30 additions and 5 deletions
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doc/boot_sectors.txt
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@ -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. 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 Master Boot Record (MBR), for PC-BIOS x86 from (pseudo-) hard disk
Apple Partition Map (APM), for more modern Mac Apple Partition Map (APM), for more modern Mac
@ -48,7 +50,6 @@ Sources:
El Torito, Bootable CD-ROM Format Specification, Version 1.0, 1995 El Torito, Bootable CD-ROM Format Specification, Version 1.0, 1995
which refers to ECMA-119, the standard for ISO 9660 filesystems. which refers to ECMA-119, the standard for ISO 9660 filesystems.
libisofs/eltorito.[ch] by Vreixo Formoso. 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 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." 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. 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 Nevertheless there is a tradition named "Boot Info Table" which prescribes
to write information into byte fields of the boot image file content. 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 There are no general means known how a producer of ISO 9660 images could
detect the need for Boot Info Table production. detect the need for Boot Info Table production.
It rather needs a hint from the user who has to know whether the boot image 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 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. | | This is the session start LBA + 16.
| | | |
12 - 15 | file_lba | Block address of the start of the boot image file 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. 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 20 - 23 | checksum | The sum of all 32-bit words of the file content
| | file content from byte 64 to file end. | | from byte 64 to file end.
| | | |
24 - 63 | 0 | Reserved 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.
---------- | ---------- | ----------------------------------------------------
------------------------------------------------------------------------------ ------------------------------------------------------------------------------