Reading from ISO9660 in U-Boot

[Simon Glass]

Hi Heinrich,

On Fri, 22 Sept 2023 at 19:02, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> On 9/23/23 00:13, Simon Glass wrote:
> > Hi Heinrick & Bin,
> >
> > I'd like to be able to figure out in U-Boot what OS is on a USB stick.
> > For example, with the Ubuntu installer, I can boot it (through grub),
> > but I cannot see how to read anything useful from the USB stick that
> > would indicate that it is Ubuntu, what version it is, etc.
> >
> > Does U-Boot need an ISO9660-filesystem driver for that? Is there any other way?
> >
> > With Debian I can see the actual files (linux and initrd) , so it is a
> > bit easier.
> >
> > Regards,
> > SImon
>
> The format of the Ubuntu images depends on the architecture. Let's
> assume that you relate to amd64
> (https://cdimage.ubuntu.com/daily-live/current/mantic-desktop-amd64.iso).
>
> This is a hybrid image, which can be either read as ISO 9660 or as a GPT
> partitioned image. This is the gdisk output:
>
> Number  Start (sector)    End (sector)  Size       Code  Name
>     1              64        10049451   4.8 GiB     0700  ISO9660
>     2        10049452        10059487   4.9 MiB     EF00  Appended2
>     3        10059488        10060087   300.0 KiB   0700  Gap1
>
> You can mount partition 2 as FAT file system in Linux:
>
> $ sudo kpartx mantic-desktop-amd64.iso -a -v
> [sudo] password for zfsdt:
> add map loop1p1 (252:4): 0 10049388 linear 7:1 64
> add map loop1p2 (252:5): 0 10036 linear 7:1 10049452
> add map loop1p3 (252:6): 0 600 linear 7:1 10059488
>
> $ sudo mount /dev/mapper/loop1p2 /mnt
>
> $ mount
> /dev/mapper/loop1p2 on /mnt type vfat
> (rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)
>
> The problem is upstream U-Boot is that the partition drivers are scanned
> alphabetically: a_efi, dos, iso
>
> If we change this to a_iso, b_efi, dos, we can read the ISO image:
>
> => host bind 0 /tmp/mantic-desktop-amd64.iso
> => part list host 0
>
> Partition Map for HOST device 0  --   Partition Type: ISO
>
> Part   Start     Sect x Size Type
>    1     3684        4    512 U-Boot
>    2 10049452    10036    512 U-Boot
>
> => ls host 0:2
>              EFI/
>
> => load host 0:2 $kernel_addr_r EFI/boot/bootx64.efi
> 960472 bytes read in 0 ms
>
> Unfortunately the sandbox crashes when executing the EFI binary.
>
> So let't try qemu-x86_64_defconfig:
>
> qemu-system-x86_64 -m 3G -nographic -bios u-boot.rom \
> -drive if=none,file=/tmp/mantic-desktop-amd64.iso,format=raw,id=VIRTIO1 \
> -device virtio-blk,drive=VIRTIO1
>
> And voilá your are in GRUB.
>
> As it does not find the /boot directory let's go to the GRUB console:

I'm not sure what is going on there, as for me 'bootflow scan -lb usb'
boots automaticaly.

>
> grub> root=(cd0,gpt1)
> grub> linux /casper/vmlinuz root=/dev/vda1 efi=debug console=/dev/ttyS0
> grub> initrd /casper/initrd
> grub> boot
> EFI stub: Loaded initrd from LINUX_EFI_INITRD_MEDIA_GUID device path
>
> I have no clue why it stops here.

That's the efi_gop graphics bug. I sent a v2 patch for it[1]

Regards,
Simon

[1] https://patchwork.ozlabs.org/project/uboot/patch/20230922153814.v2.1.I9f7f373d00947c704aeae0088dfedd8df07fab60@changeid/