On Fri, 2011-10-28 at 08:46 +0100, Philipp Hahn wrote:
> Hello Ian,
>
> On Thursday 27 October 2011 12:21:05 Ian Campbell wrote:
> > On Tue, 2011-10-25 at 11:33 +0100, Philipp Hahn wrote:
> > [...snip explanations...]
> >
> > Thanks Philipp, that all seems to make sense.
> >
> > Tim had some suggestions on how/where this functionality could be better
> > implemented though.
>
> v2: For HybrisISOs use offset 0 in addition instead of replacement.
>
> Signed-off-by: Philipp Hahn <hahn@xxxxxxxxxxxxx>
> ---
> grub-mkrescue internally uses xorriso, which generates a so-called "Hybrid
> ISO": The ISO images also contains a DOS partition table, which allows the
> identical ISO file to be stored on an USB stick for booting from it. This
> breaks PyGrub, since it (wrongly) detects only the DOS partition table and
> uses the first partition instead of the complete ISO file.
>
> Add a check to detect HybridISO files and use offset 0 in addition to
> partition table parsing.
> --- a/tools/pygrub/src/pygrub
> +++ b/tools/pygrub/src/pygrub
> @@ -40,15 +40,20 @@ def enable_cursor(ison):
> except _curses.error:
> pass
>
> -def is_disk_image(file):
> +DISK_TYPE_RAW, DISK_TYPE_HYBRIDISO, DISK_TYPE_DOS = range(3)
> +def identify_disk_image(file):
> + """Detect DOS partition table or HybridISO format."""
> fd = os.open(file, os.O_RDONLY)
> - buf = os.read(fd, 512)
> + buf = os.read(fd, 0x8006)
Can we avoid reading all that just for the 7 bytes we are interested in.
What about (just pseudo python, I didn't actually lookup seek etc):
buf = os.read(fd, 512)
if len(buf) >= 512 and \
not struct.unpack("H", buf[0x1fe: 0x200]) == (0xaa55,):
return ...RAW
os.seek(0x8000)
buf = os.read(fd, 6)
if len... and buf[0x8001...] == 'CD001':
return ...HYBRID
else:
return ...DOS
on the other hand I suppose it's only 8k...
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Thanks.
Ian
.
> os.close(fd)
>
> if len(buf) >= 512 and \
> struct.unpack("H", buf[0x1fe: 0x200]) == (0xaa55,):
> - return True
> - return False
> + # HybridISO contains a DOS partition table for booting from USB
> devices, but really is an ISO image
> + if len(buf) >= 0x8006 and buf[0x8001:0x8006] == 'CD001':
> + return DISK_TYPE_HYBRIDISO
> + return DISK_TYPE_DOS
> + return DISK_TYPE_RAW
>
> SECTOR_SIZE=512
> DK_LABEL_LOC=1
> @@ -87,12 +92,19 @@ FDISK_PART_SOLARIS_OLD=0x82
> FDISK_PART_GPT=0xee
>
> def get_partition_offsets(file):
> - if not is_disk_image(file):
> + image_type = identify_disk_image(file)
> + if image_type == DISK_TYPE_RAW:
> # No MBR: assume whole disk filesystem, which is like a
> # single partition starting at 0
> return [0]
> -
> - part_offs = []
> + elif image_type == DISK_TYPE_HYBRIDISO:
> + # A HybridISO contains an ISO filesystem at 0 in addition
> + # to the DOS partition table
> + part_offs = [0]
> + elif image_type == DISK_TYPE_DOS:
> + part_offs = []
> + else:
> + raise ValueError('Unhandled image type returnd by
> identify_disk_image(): %d' % (image_type,))
>
> fd = os.open(file, os.O_RDONLY)
> buf = os.read(fd, 512)
>
> Sincerely
> Philipp
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