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annotate mysteryffs/README @ 404:ceb71478414d

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tfo: find-is-hdr program written
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 11 Mar 2023 18:16:22 +0000
parents d41c555d7f1d
children
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d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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1 MysteryFFS is my (Michael Spacefalcon's) arbitrarily-chosen nickname for the
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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2 flash file system found in at least two Calypso/Riviera-based GSM phone or
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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3 modem SW designs: Pirelli DP-L10 and Closedmoko GTA0x.
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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4
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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5 The FFS implementation which I have nicknamed MysteryFFS is identifiable by the
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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6 following magic at the beginning of every flash erase unit used by this FFS:
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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7
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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8 00000000: 46 66 73 23 10 02 FF FF AB FF FF FF FF FF FF FF Ffs#............
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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9
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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10 The byte at offset 8 into the erase unit (AB in the illustration above)
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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11 has been observed to be one of 3 possibilities:
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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12
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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13 AB: this erase unit appears to be the active index block
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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14 BD: regular data block
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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15 BF: last block of the flash "partition" used for the FFS
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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16
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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17 On the Pirelli this MysteryFFS takes up the first 4.5 MiB (18 erase units
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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18 of 256 KiB each) of the 2nd flash chip select (nCS3). On the Closedmoko
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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19 it lives in the second half of the last megabyte of the 4 MiB flash chip,
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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20 taking up 7 erase units of 64 KiB each, i.e., spanning absolute flash chip
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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21 offsets from 0x380000 through 0x3EFFFF.
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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22
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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23 (The 4 MiB NOR flash chip used by Closedmoko has an independent R/W bank
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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24 division between the first 3 MiB and the last 1 MiB. The first 3 MiB are used
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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25 to hold the field-flashable closed firmware images distributed as *.m0 files;
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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26 the independent last megabyte holds the FFS, and thus the FW could be
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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27 implemented to do FFS writes while running from flash in the main bank.
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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28 Less than half of that last megabyte appears to be used for the FFS though;
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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29 the rest appears to be unused - blank flash observed.)
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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30
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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31 I have nicknamed this flash file system MysteryFFS because I haven't been able
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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32 to identify it as any known FFS design. The FFS implemented in the liberated
d41c555d7f1d beginning to explore MysteryFFS
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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33 TSM30 code appears to be different, hence that source is not of much help.
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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34 Therefore, I am reverse-engineering this MysteryFFS in order to extract the
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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35 file system content from my Pirelli phones and from my GTA02.