Message-ID: <4D2F99AD.9060906@dell.com>
Date: Thu, 13 Jan 2011 18:32:45 -0600
From: Mario Limonciello <mario_limonciello AT dell DOT com>
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To: cygwin AT cygwin DOT com
Subject: grub-setup failing on writing partition boot code, but dd working
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 Hi All:

I've been doing lots of experimentation with calling grub-setup from Window=
s to prepare the bootsector of a FAT32 volume.  I'm finding that for some r=
eason, the bootcode doesn't actually get written to the PBR even though gru=
b-setup thinks the write has succeeded.

To achieve this test i'm doing the following:
1) Create the FAT32 partition using diskpart
2) mkdir -p /boot/grub
3) Drop a boot.img and core.img in /boot/grub taken from a Linux build (the=
y're in ELF's then).
4) grub-setup.exe --verbose --force -d /cygdrive/e/boot/grub /dev/sdb1

If I dd the partition bootsector before starting and afterward to compare, =
it's not changing at all.
(dd if=3D/dev/sdb of=3Dbootsect bs=3D512 skip=3D128 count=3D1)

Now conversely if I use dd to try to place the contents of a 512 byte file =
in that place, it works fine.
(dd if=3Dbootsect of=3D/dev/sdb bs=3D512 seek=3D128 count=3D1)

I've tried to compare the code that dd and grub-setup both use, and even mo=
dified the open mode that grub-setup uses, but still get the same results.

If I run grub-setup under strace, a Windows error actually shows up, which =
makes me think this is actually a bug in cygwin1.dll.  Here's the relevant =
output from strace on grub-setup as it's opening the drive, seeking and att=
empting to write it:

  206 13511691 [main] grub-setup 2608 open: open (/dev/sdb, 0x10202)
   52 13511743 [main] grub-setup 2608 normalize_posix_path: src /dev/sdb
   52 13511795 [main] grub-setup 2608 normalize_posix_path: /dev/sdb =3D no=
rmalize_posix_path (/dev/sdb)
   53 13511848 [main] grub-setup 2608 mount_info::conv_to_win32_path: conv_=
to_win32_path (/dev/sdb)
   58 13511906 [main] grub-setup 2608 mount_info::conv_to_win32_path: src_p=
ath /dev/sdb, dst \Device\Harddisk1\Partition0, flags 0x2, rc 0
   58 13511964 [main] grub-setup 2608 build_fh_pc: fh 0x612424E4
   54 13512018 [main] grub-setup 2608 fhandler_base::open: (\Device\Harddis=
k1\Partition0, 0x10002)
   76 13512094 [main] grub-setup 2608 fhandler_base::set_flags: flags 0x100=
02, supplied_bin 0x10000
   58 13512152 [main] grub-setup 2608 fhandler_base::set_flags: O_TEXT/O_BI=
NARY set in flags 0x10000
   52 13512204 [main] grub-setup 2608 fhandler_base::set_flags: filemode se=
t to binary
   52 13512256 [main] grub-setup 2608 fhandler_base::open: 0 =3D NtCreateFi=
le (0x224, C0100000, \Device\Harddisk1\Partition0, io, NULL, 0, 7, 1, 4020,=
 NULL, 0)
   53 13512309 [main] grub-setup 2608 fhandler_base::open: 1 =3D fhandler_b=
ase::open (\Device\Harddisk1\Partition0, 0x10002)
  193 13512502 [main] grub-setup 2608 fhandler_dev_floppy::get_drive_info: =
disk geometry: (780 cyl)*(64 trk)*(63 sec)*(512 bps)
   58 13512560 [main] grub-setup 2608 fhandler_dev_floppy::get_drive_info: =
partition info: offset 0  length 1610612736
   53 13512613 [main] grub-setup 2608 fhandler_dev_floppy::get_drive_info: =
drive size: 1610612736
   52 13512665 [main] grub-setup 2608 open: 4 =3D open (/dev/sdb, 0x10202)
  106 13512771 [main] grub-setup 2608 lseek64: 65536 =3D lseek (4, 65536, 0)
   52 13512823 [main] grub-setup 2608 writev: writev (4, 0x22C784, 1)
   52 13512875 [main] grub-setup 2608 fhandler_base::write: binary write
  287 13513162 [main] grub-setup 2608 fhandler_dev_floppy::write_file: 1 (e=
rr 0) =3D WriteFile (548, 13541288, write 512, written 512, 0)
   67 13513229 [main] grub-setup 2608 writev: 512 =3D write (4, 0x22C784, 1=
), errno 2
   66 13513295 [main] grub-setup 2608 seterrno_from_win_error: /netrel/src/=
cygwin-snapshot-20101229-1/winsup/cygwin/fhandler.cc:1591 windows error 1
   60 13513355 [main] grub-setup 2608 geterrno_from_win_error: windows erro=
r 1 =3D=3D errno 54


If I compare that to what DD is doing:

 2131  391915 [main] dd 3400 open: 3 =3D open (/dev/sdb, 0x10202)
 1183  393098 [main] dd 3400 dtable::dup3: dup3 (3, 1, 0x0)
 1337  394435 [main] dd 3400 build_fh_pc: fh 0x61241884
 1187  395622 [main] dd 3400 fhandler_base::dup: in fhandler_base dup
 1174  396796 [main] dd 3400 dtable::dup_worker: duped '/dev/sdb' old 0x154=
, new 0x160
 1342  398138 [main] dd 3400 dtable::dup3: newfh->io_handle 0x160, oldfh->i=
o_handle 0x154, new win32_name 0x61242214, old win32_name 0x6124225C
 1682  399820 [main] dd 3400 close: close (1)
 1271  401091 [main] dd 3400 fhandler_base::close: closing '' handle 0x258
 1417  402508 [main] dd 3400 close: 0 =3D close (1)
 1157  403665 [main] dd 3400 dtable::dup3: 1 =3D dup3 (3, 1, 0x0)
 1073  404738 [main] dd 3400 close: close (3)
 1475  406213 [main] dd 3400 fhandler_base::close: closing '/dev/sdb' handl=
e 0x154
 1620  407833 [main] dd 3400 close: 0 =3D close (3)
 1291  409124 [main] dd 3400 __set_errno: virtual int fhandler_base::ftrunc=
ate(_off64_t, bool):1558 val 22
 2224  411348 [main] dd 3400 ftruncate64: -1 =3D ftruncate (1, 65536)
 1379  412727 [main] dd 3400 fhandler_dev_raw::fstat: here
 1214  413941 [main] dd 3400 fhandler_base::fstat: here
 1162  415103 [main] dd 3400 time: 1294954129 =3D time (0)
  945  416048 [main] dd 3400 fstat64: 0 =3D fstat (1, 0x22CC48)
  673  416721 [main] dd 3400 lseek64: 65536 =3D lseek (1, 65536, 1)
  944  417665 [main] dd 3400 readv: readv (0, 0x22CB94, 1) blocking, sigcat=
chers 2
 1801  419466 [main] dd 3400 fhandler_base::read: returning 512, binary mode
 1357  420823 [main] dd 3400 readv: 512 =3D readv (0, 0x22CB94, 1), errno 0
 1535  422358 [main] dd 3400 fhandler_base::write: binary write
 1468  423826 [main] dd 3400 fhandler_dev_floppy::write_file: 1 (err 0) =3D=
 WriteFile (352, 9437184, write 512, written 512, 0)

I'm not sure why internally cygwin decided to use writev() for grub-setup a=
nd write() for writing the data out.  In both cases, dd and grub-setup both=
 use write() in their code.

I've already tried the latest snapshot of cygwin1.dll (2011-12-29 at this t=
ime), and i'm getting the same results as with the current stable version.

Any ideas?
--=20
*Mario Limonciello*
Linux Engineer
*Dell* | OS Engineering


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