3.12-rc5 and overwritten partition table

[John Twideldum]

Hi...

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
0000700radio:hci0\t100.0
00007200000\nradio:phy0\t
0000740100.00000\nradio:
0000760tpacpi_bluetooth
0001000

:-(

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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