Re: [Bug-xorriso] Test Proposal for [bug #46716] Protective MBR partition is not marked as bootable

[Alexander E. Patrakov]

[re-adding bug-grub to CC]
29.12.2015 23:39, Alexander E. Patrakov пишет:
> 29.12.2015 22:51, Thomas Schmitt пишет:
> > Hi,
> >
> > Alexander E. Patrakov wrote:
> > > > > 2B: prints "this is not a bootable disk" message
> >
> > i wrote:
> > > > You see a string from the EFI partition 0xef in your old BIOS ?
> >
> > > Yes! And it shows it despite the fact that there is no bootable
> > > partition!
> >
> > Is this string from the very start of /efi.img ?
> > In this case the BIOS possibly hopped on the only partition (0xef)
> > and tried to execute the x86 machine code of its Extended Boot Record.
>
> Yes, this is the string from the boot record of that partition.
>
> > > > (pseudo-)protective partition (program variant 2C with EFI
> > > >    partition as MBR partition 2)
> >
> > > Not sure if I understand this variant correctly, a report from
> > > xorriso would
> > > be welcome.
> >
> > The default "mjg" mode 2B appends the ESP as MBR partition 1.
> > In this case, no partition table entry for the ISO filesystem
> > is created.
> > So we end up with a single MBR partition 0xef (to which we do
> > not want to apply the boot flag).
> >
> > MKRESCUE_SED_PARTNO=2 in run 2C appends the ESP as partition 2
> > and leaves partition table entry 1 available for covering the ISO
> > filesystem.
> > Now it depends on --protective-msdos-label whether this partition 1
> > starts at block 1 (in case the option is present) or at block 0
> > (in case the option is missing).
> > If the start is at block 0, then the MBR partition 1 is mountable as
> > ISO 9660.
>
> OK, I see. I will test the case when it starts at block 0 tomorrow.

It works on DG965SS when booted from USB, and also works in KVM.

address@hidden:~/isos$ xorriso -indev minimal-mjg-p0.iso -report_system_area 
plain -report_el_torito plain
GNU xorriso 1.4.3 : RockRidge filesystem manipulator, libburnia project.

xorriso : NOTE : Loading ISO image tree from LBA 0
xorriso : UPDATE : 821 nodes read in 1 seconds
xorriso : NOTE : Detected El-Torito boot information which currently is 
set to be discarded
Drive current: -indev 'minimal-mjg-p0.iso'
Media current: stdio file, overwriteable
Media status : is written , is appendable
Boot record  : El Torito , MBR GPT APM
Media summary: 1 session, 6488 data blocks, 12.7m data, 2296m free
Volume id    : 'ISOIMAGE'
System area options: 0x00004200
System area summary: MBR GPT APM
ISO image size/512 : 25952
Partition offset   : 0
MBR heads per cyl  : 64
MBR secs per head  : 32
MBR partition table:   N Status  Type        Start       Blocks
MBR partition      :   1   0x80  0x83            0        25952
MBR partition      :   2   0x00  0xef        25952         5760
GPT                :   N  Info
GPT disk GUID      :      f8e95c1c1b3e76429c3027fb01725a1d
GPT entry array    :      16  192  separated
GPT lba range      :      64  31714  31763
GPT partition name :   1  490053004f004800790062007200690064003100
GPT partname local :   1  ISOHybrid1
GPT partition GUID :   1  f8e95c1c1b3e76429c3127fb01725a1d
GPT type GUID      :   1  a2a0d0ebe5b9334487c068b6b72699c7
GPT partition flags:   1  0x1000000000000001
GPT start and size :   1  19720  5760
GPT partition path :   1  /efi.img
APM                :   N  Info
APM block size     :      2048
APM gap fillers    :      0
APM partition name :   1  HFSPLUS_Hybrid
APM partition type :   1  Apple_HFS
APM start and size :   1  83  6405
APM partition name :   2  Appended2
APM partition type :   2  Data
APM start and size :   2  6488  1440
El Torito catalog  : 224  1
El Torito cat path : /boot.catalog
El Torito images   :   N  Pltf  B   Emul  Ld_seg  Hdpt  Ldsiz         LBA
El Torito boot img :   1  BIOS  y   none  0x0000  0x00      4        2620
El Torito boot img :   2  UEFI  y   none  0x0000  0x00   5760        4930
El Torito img path :   1  /boot/grub/i386-pc/eltorito.img
El Torito img opts :   1  boot-info-table grub2-boot-info
El Torito img path :   2  /efi.img

So, I can agree with making this (or the variant without efi.img 
duplication) the default layout for grub-mkrescue, but I would also like 
to see a wiki page describing the rationale for each element of this 
layout in one place. E.g.:

 - why is GPT present at all?
 - how do we know that it is used by at least one system, despite the 
absence of the 0xee MBR partition?

--
Alexander E. Patrakov