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

[Alexander E. Patrakov]

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.

> In any case, partition 1 can take the boot flag if it is clear to
> libisofs that a GRUB2 related MBR is present.
> libisofs may safely assume this if --protective-msdos-label or
> --grub2-mbr are present.
> In this case it actually needs no encouragement by
> --protective-msdos-bootflag.
>
> So the description would rather be
>
>   --protective-msdos-bootflag
>        Enforce an MBR partition with "bootable/active" flag if options
>        --protective-msdos-label or --grub2-mbr are given.
>        These options normally cause the bootable flag to be set if
>        there is an MBR partition of type other than 0xee or 0xef.
>        If no such partition exists, then no bootflag is set, unless
>        --protective-msdos-bootflag forces creation of a dummy partition
>        of type 0x00 which covers only the first block of the ISO image.

Looks good.

--
Alexander E. Patrakov