Colin Watson <[EMAIL PROTECTED]> wrote:
...
> Please consider the following patch, which does basically the same
> thing. I think it's sufficiently trivial (and obvious based on other
> implementations) to be non-copyrightable, but I can do assignment
> paperwork if you feel you need it.
>
> With this patch, the supplied boot sector prints as follows:
>
> $ LD_LIBRARY_PATH=`pwd`/libparted/.libs parted/.libs/parted ~/parted-test
> WARNING: You are not superuser. Watch out for permissions.
> GNU Parted 1.8.8.1.30-c31f
> Using /home/cjwatson/parted-test
> Welcome to GNU Parted! Type 'help' to view a list of commands.
> (parted) print
> Model: (file)
> Disk /home/cjwatson/parted-test: 1573MB
> Sector size (logical/physical): 512B/512B
> Partition Table: msdos
>
> Number Start End Size Type File system Flags
> 1 16.4kB 751MB 751MB primary boot
> 2 751MB 1027MB 276MB primary
>
> Signed-off-by: Colin Watson <[EMAIL PROTECTED]>
>
> ---
> dos.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/libparted/labels/dos.c b/libparted/labels/dos.c
> index e513a05..81d8600 100644
> --- a/libparted/labels/dos.c
> +++ b/libparted/labels/dos.c
> @@ -192,14 +192,16 @@ msdos_probe (const PedDevice *dev)
> if (PED_LE16_TO_CPU (part_table->magic) != MSDOS_MAGIC)
> goto probe_fail;
>
> - /* if this is a FAT fs, fail here. Note that the Smart Boot Manager
> - * Loader (SBML) signature indicates a partition table, not a file
> - * system.
> + /* If this is a FAT fs, fail here. Checking for the FAT signature
> + * has some false positives; instead, do what the Linux kernel does
> + * and ensure that each partition has a boot indicator that is
> + * either 0 or 0x80.
> */
> - if ((!strncmp (part_table->boot_code + 0x36, "FAT", 3)
> - && strncmp (part_table->boot_code + 0x40, "SBML", 4) != 0)
> - || !strncmp (part_table->boot_code + 0x52, "FAT", 3))
> - goto probe_fail;
> + for (i = 0; i < 4; i++) {
> + if (part_table->partitions[i].boot_ind != 0
> + && part_table->partitions[i].boot_ind != 0x80)
> + goto probe_fail;
> + }
>
> /* If this is a GPT disk, fail here */
> for (i = 0; i < 4; i++) {
Thanks for all the analysis and the bug fix.
I confirmed that following code in msdos.c was improperly rejecting
the partition table due to the presence of the string "FAT" at a
"well-known" offset:
- if ((!strncmp (part_table->boot_code + 0x36, "FAT", 3)
- && strncmp (part_table->boot_code + 0x40, "SBML", 4) != 0)
- || !strncmp (part_table->boot_code + 0x52, "FAT", 3))
- goto probe_fail;
[checking the MBR at offset 0x52, you do see "FAT":
$ od -taz -An --skip=82 --read=5 /tmp/sdb-2KB
F A T 3 2 >FAT32<
and that your patch works.
I agree on the copyright front.
I'm debating how to test for this.
I'll probably push your patch tomorrow.
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