3.12-rc5 and overwritten partition table

From: John Twideldum
Date: Tue Oct 29 2013 - 07:37:11 EST


I have a shiny new Haswell notebook (Lenovo T440s), where with 3.11 processor power
management didn't work, so I got 3.12-rc5 installed.
Worked fine for a few days, then today it no longer boots and inspection yields...

# dd if=/dev/sda count=1 |od -t c |tr -d " "
512 bytes (512 B) copied, 0.00115806 s, 442 kB/s
0000000 13.00000\nalsa:hw
0000020 C0D0\t99.00000\nal
0000040 sa:hwC0D3\t99.000
0000060 00\nbacklight:acp
0000100 i_video0\t73.0000
0000120 0\nbacklight:acpi
0000140 _video0-power\t10
0000160 0.00000\nbackligh
0000200 t:intel_backligh
0000220 t\t0.00000\nbackli
0000240 ght:intel_backli
0000260 ght-power\t0.0000
0000300 0\ncpu-consumptio
0000320 n\t0.00000\ncpu-wa
0000340 keups\t875.00000\n
0000360 disk-operations\t
0000400 0.00000\ndisk-ope
0000420 rations-hard\t0.0
0000440 0000\neth0-link-1
0000460 00\t0.00000\neth0-
0000500 link-1000\t0.0000
0000520 0\neth0-link-high
0000540 \t0.00000\neth0-pa
0000560 ckets\t0.00000\net
0000600 h0-powerunsave\t0
0000620 .00000\neth0-up\t0
0000640 .00000\ngpu-opera
0000660 tions\t134.00000\n


In order to figure out the reason for this, can you kernel guys maybe
a) tell me what is that datastructure?
b) can power management be buggy to cause this - I played with powertop tuneables
approximately while this happened?

...and point me to a recovery tool/doc for finding the partitions again,
"testdisk" tool only found 1 of 3, the least important one at the beginning of
disk but not the rest :-(

Thank you for any pointers/help!
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