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Re: [Xen-devel] [PATCH] pygrub: look in every partition for something to boot
Good job. I've come across this problem before.
On 6 July 2010 11:45, Tim Deegan <Tim.Deegan@xxxxxxxxxx> wrote:
pygrub: look in every partition for something to boot, in case
the OS installer (SLES 10 sp1 in particular) forgets to mark the
boot partition as active.
Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
diff -r 78b2f1e04c73 tools/pygrub/src/pygrub
--- a/tools/pygrub/src/pygrub Tue Jul 06 11:09:36 2010 +0100
+++ b/tools/pygrub/src/pygrub Tue Jul 06 11:38:42 2010 +0100
@@ -50,21 +50,6 @@
return True
return False
-def get_active_partition(file):
- """Find the offset for the start of the first active partition "
- "in the disk image file."""
-
- fd = os.open(file, os.O_RDONLY)
- buf = os.read(fd, 512)
- for poff in (446, 462, 478, 494): # partition offsets
- # active partition has 0x80 as the first byte
- if struct.unpack("<c", buf[poff:poff+1]) == ('\x80',):
- return buf[poff:poff+16]
-
- # if there's not a partition marked as active, fall back to
- # the first partition
- return buf[446:446+16]
-
SECTOR_SIZE=512
DK_LABEL_LOC=1
DKL_MAGIC=0xdabe
@@ -101,25 +86,44 @@
FDISK_PART_SOLARIS_OLD=0x82
FDISK_PART_GPT=0xee
-def get_fs_offset(file):
+def get_partition_offsets(file):
if not is_disk_image(file):
- return 0
+ # No MBR: assume whole disk filesystem, which is like a
+ # single partition starting at 0
+ return [0]
- partbuf = get_active_partition(file)
- if len(partbuf) == 0:
- raise RuntimeError, "Unable to find active partition on disk"
+ part_offs = []
- offset = struct.unpack("<L", partbuf[8:12])[0] * SECTOR_SIZE
+ fd = os.open(file, os.O_RDONLY)
+ buf = os.read(fd, 512)
+ for poff in (446, 462, 478, 494): # partition offsets
- type = struct.unpack("<B", partbuf[4:5])[0]
+ # MBR contains a 16 byte descriptor per partition
+ partbuf = buf[poff:poff+16]
+ offset = struct.unpack("<L", partbuf[8:12])[0] * SECTOR_SIZE
+ type = struct.unpack("<B", partbuf[4:5])[0]
+
+ # offset == 0 implies this partition is not enabled
+ if offset == 0:
+ continue
- if type == FDISK_PART_SOLARIS or type == FDISK_PART_SOLARIS_OLD:
- offset += get_solaris_slice(file, offset)
+ if type == FDISK_PART_SOLARIS or type == FDISK_PART_SOLARIS_OLD:
+ try:
+ offset += get_solaris_slice(file, offset)
+ except RuntimeError:
+ continue # no solaris magic at that offset, ignore partition
- if type == FDISK_PART_GPT:
- offset = get_fs_offset_gpt(file)
-
- return offset
+ if type == FDISK_PART_GPT:
+ offset = get_fs_offset_gpt(file)
+
+ # Active partition has 0x80 as the first byte.
+ # If active, prepend to front of list, otherwise append to back.
+ if struct.unpack("<c", buf[poff:poff+1]) == ('\x80',):
+ part_offs.insert(0, offset)
+ else:
+ part_offs.append(offset)
+
+ return part_offs
class GrubLineEditor(curses.textpad.Textbox):
def __init__(self, screen, startx, starty, line = ""):
@@ -703,17 +711,40 @@
bootfsargs = '"%s"' % incfg["args"]
bootfsgroup = re.findall('zfs-bootfs=(.*?)[\s\,\"]', bootfsargs)
if bootfsgroup:
- fs = fsimage.open(file, get_fs_offset(file), bootfsgroup[0])
+ bootfsoptions = bootfsgroup[0]
else:
- fs = fsimage.open(file, get_fs_offset(file))
+ bootfsoptions = ""
- chosencfg = sniff_solaris(fs, incfg)
+ # get list of offsets into file which start partitions
+ part_offs = get_partition_offsets(file)
- if not chosencfg["kernel"]:
- chosencfg = sniff_netware(fs, incfg)
+ for offset in part_offs:
+ try:
+ fs = fsimage.open(file, offset, bootfsoptions)
- if not chosencfg["kernel"]:
- chosencfg = run_grub(file, entry, fs, incfg["args"])
+ chosencfg = sniff_solaris(fs, incfg)
+
+ if not chosencfg["kernel"]:
+ chosencfg = sniff_netware(fs, incfg)
+
+ if not chosencfg["kernel"]:
+ chosencfg = run_grub(file, entry, fs, incfg["args"])
+
+ # Break as soon as we've found the kernel so that we continue
+ # to use this fsimage object
+ if chosencfg["kernel"]:
+ break
+ fs = None
+
+ except:
+ # IOErrors raised by fsimage.open
+ # RuntimeErrors raised by run_grub if no menu.lst present
+ fs = None
+ continue
+
+ # Did looping through partitions find us a kernel?
+ if not fs:
+ raise RuntimeError, "Unable to find partition containing kernel"
if not_really:
bootcfg["kernel"] = "<kernel:%s>" % chosencfg["kernel"]
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