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gsm-fw/L1: fix for the DSP patch corruption bug The L1 code we got from the LoCosto fw contains a feature for DSP CPU load measurement. This feature is a LoCosto-ism, i.e., not applicable to earlier DBB chips (Calypso) with their respective earlier DSP ROMs. Most of the code dealing with that feature is conditionalized as #if (DSP >= 38), but one spot was missed, and the MCU code was writing into an API word dealing with this feature. In TCS211 this DSP API word happens to be used by the DSP code patch, hence that write was corrupting the patched DSP code.
author Mychaela Falconia <falcon@ivan.Harhan.ORG>
date Mon, 19 Oct 2015 17:13:56 +0000
parents 4eeab025b502
children
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4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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1 The description of TIFFS that follows was originally written in the summer of
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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2 SE52 (A.D. 2013), before the major TI source discoveries which happened later
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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3 that year. The text following the dividing line below has not been edited in
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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4 content since it was written; for a newer write-up based on the current source-
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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5 enabled understanding and reflecting the current FreeCalypso plans with respect
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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6 to this FFS, see TIFFS-Overview.
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7
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8 -------------------------------------------------------------------------------
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9
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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10 This is a description, based on reverse engineering, of the flash file system
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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11 (FFS) implemented in Pirelli's original firmware for the DP-L10 GSM/WiFi dual
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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12 mode mobile phone, and in the Closedmoko GTA0x modem firmware. Not knowing the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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13 "proper" name for this FFS, and needing _some_ identifier to refer to it, I
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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14 have named it Mokopir-FFS, from "Moko" and "Pirelli" - sometimes abbreviated
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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15 further to MPFFS.
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16
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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17 (I have previously called the FFS in question MysteryFFS; but now that I've
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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18 successfully reverse-engineered it, it isn't as much of a mystery any more :-)
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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19
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20 At a high functional level, Mokopir-FFS presents the following features:
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21
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22 * Has a directory tree structure like UNIX file systems;
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23
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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24 * The file system API that must be implemented inside the proprietary firmware
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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25 appears to use UNIX-style pathnames; doing strings on firmware images reveals
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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26 pathname strings like these:
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27
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28 /var/dbg/dar
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29 /gsm/l3/rr_white_list
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30 /gsm/l3/rr_medium_rxlev_thr
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31 /gsm/l3/rr_upper_rxlev_thr
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32 /gsm/l3/shield
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33
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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34 Parsing the corresponding FFS image with tools included in the present
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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35 package has confirmed that the directory structure implied by these pathnames
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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36 does indeed exist in the FFS.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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37
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38 * Absolutely no DOS-ish semantics seen anywhere: no 8.3 filenames and no
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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39 colon-separated device names (seen in the TSM30 file system source, for
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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40 example) are visible in the Closedmoko/Pirelli FFS.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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41
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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42 * File contents are stored uncompressed, but not necessarily contiguous: one
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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43 could probably store a file in FFS which is bigger than the flash sector
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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44 size, it which case it can never be contiguous in a writable FFS (see below),
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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45 and the firmware implementation seems to limit chunk sizes to a fairly small
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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46 number: on the Pirelli phones all largish files are divided into chunks of
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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47 8 KiB each, and on my GTA02 the largest observed chunk size is only 2 KiB.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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48
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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49 The smaller files, like the IMEI and the firmware ID strings in my GTA02 FFS,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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50 are contiguous.
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51
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52 * The FFS structure is such that the length of "user" payload data stored in
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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53 each chunk (and consequently, in each file) can be known exactly in bytes,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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54 with the files/chunks able to contain arbitrary binary data. (This property
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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55 may seem obvious or trivial, as all familiar UNIX and DOS file systems have
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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56 it, but contrast with RT-11 for example.)
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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57
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58 * The flash file system is a writable one: the running firmware can create,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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59 delete and overwrite files (and possibly directories too) in the live FFS;
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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60 thus the FFS design is such that allows these operations to be performed
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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61 within the physical constraints of NOR flash write operations.
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62
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63 I have reverse-engineered this Mokopir-FFS on a read-only level. What it means
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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64 is that I, or anyone else who can read this document and the accompanying
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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65 source for the listing/extraction utilities, can take a Mokopir-FFS image read
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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66 out of a device and see/extract its full content: the complete directory tree
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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67 and the exact binary byte content of all files contained therein.
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68
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69 However, the knowledge possessed by the present hacker (and conveyed in this
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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70 document and the accompanying source code) is NOT sufficient for constructing a
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71 valid Mokopir-FFS image "in vitro" given a tree of directories and files, or
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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72 for making modifications to the file or directory content of an existing image
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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73 and producing a content-modified image that is also valid; valid as in suitable
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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74 for the original proprietary firmware to make its normal read and write
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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75 operations without noticing anything amiss.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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76
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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77 Constructing "de novo" Mokopir-FFS images or modifying existing images in such
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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78 a way that they remain 100% valid for all read and write operations of the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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79 original proprietary firmware would, at the very minimum, require an
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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80 understanding of the meaning of *all* fields of the on-media FFS format. Some
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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81 of these fields are still left as "non-understood" for now though: a read-only
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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82 implementation can get away with simply ignoring them, but a writer/generator
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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83 would have to put *something* in those fields.
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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84
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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85 As you read the "read-only" description of the Mokopir-FFS on-media format in
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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86 the remainder of this document, it should become fairly obvious which pieces
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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87 are missing before our understanding of this FFS can be elevated to a
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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88 "writable" level.
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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89
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90 However, when it comes to writing new code to run on the two Calypso phones in
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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91 question (Closedmoko and Pirelli), it seems, at least to the present hacker,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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92 that a read-only understanding of Mokopir-FFS should be sufficient:
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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93
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94 * In the case of Closedmoko GTA0x modems, the FFS is seen to contain the IMEI
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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95 and the RF calibration data. The format of the former is obvious; the latter
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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96 not so much - but in any case, the information of interest is clearly of a
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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97 read-only nature. It's difficult to tell (or rather, I haven't bothered to
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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98 experiment enough) whether the Closedmoko firmware does any writes to FFS or
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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99 if the FFS is treated as read-only outside of the production line environment,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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100 but in any case, it seems to me that for any 3rd party replacement firmware,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
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101 the best strategy would be to treat the FFS as a read-only source of IMEI and
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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102 RF calibration data, and nothing more.
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103
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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104 * In the case of Pirelli phones, the FFS is used to store user data: sent and
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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105 received SMS (and MMS/email/whatever), call history, UI settings, pictures
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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106 taken with the camera, and whatever else. It also stores a ton of files
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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107 which I can only presume were meant to be immutable except at the time of
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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108 firmware updates: graphics for the UI, ringtones, i18n UI strings, and even
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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109 "helper" firmware images for the WiFi and VoIP processors. However, no IMEI
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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110 or RF calibration data are anywhere to be found in the FFS - instead this
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111 information appears to be stored in the "factory block" at the end of the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
112 flash (in its own sector) outside of the FFS.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
113
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
114 Being able to parse FFS images extracted out of Pirelli phones "in vitro"
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
115 allows us to steal some of these helper files (UI artwork, ringtones,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
116 WiFi/VoIP helpers), and some of these might even come useful to firmware
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
117 replacement projects, but it seems to me that a replacement firmware would
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
118 be better off using its own FFS design for storing user data, and as to
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
119 retrieving the original IMEI and RF calibration data, the original FFS isn't
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
120 of any use for that anyway.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
121
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
122 =======================
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
123 Moko/Pirelli FFS format
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
124 =======================
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
125
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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126 OK, now that I'm done with the introduction, we can get to the actual
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
127 Mokopir-FFS format.
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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128
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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129 * On the GTA0x modem (or at least on my GTA02; my sample size is 1) the FFS
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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130 occupies 7 flash sectors of 64 KiB each at offsets 0x380000 through 0x3E0000,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
131 inclusive.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
132
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
133 (The 4 MiB NOR flash chip used by Closedmoko has an independent R/W bank
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
134 division between the first 3 MiB and the last 1 MiB. The first 3 MiB are used
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
135 to hold the field-flashable closed firmware images distributed as *.m0 files;
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
136 the independent last megabyte holds the FFS, and thus the FW could be
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
137 implemented to do FFS writes while running from flash in the main bank.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
138 Less than half of that last megabyte appears to be used for the FFS though;
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
139 the rest appears to be unused - blank flash observed.)
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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140
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
141 * On the Pirelli the FFS occupies 18 sectors of 256 KiB each at offsets 0
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
142 through 0x440000 (inclusive) of the 2nd flash chip select, the one wired to
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
143 nCS3 on the Calypso.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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diff changeset
144
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
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145 Each flash sector allocated to FFS begins with the following signature:
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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diff changeset
146
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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diff changeset
147 00000000: 46 66 73 23 10 02 xx yy zz FF FF FF FF FF FF FF Ffs#............
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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diff changeset
148
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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diff changeset
149 The bytes shown as xx and yy above serve a non-understood purpose; as a guess,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
150 they may hold some info for the flash wear leveling algorithm: in a "virgin"
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
151 FFS image like that found in my GTA02 (which never had a SIM card in it and
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
152 never made or received a call) or read out of a "virgin" Pirelli phone that
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
153 hasn't seen any active use yet, both of these bytes are FFs, but when I look at
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
154 FFS images read out of the Pirelli which I currently use as my everyday-use
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
155 cellphone, I see other values in sectors which must have been erased and
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
156 rewritten. A read-only implementation can ignore these bytes, as mine does.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
157
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
158 The byte shown as zz is more important though, even to a read-only
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
159 implementation. The 3 values I've encountered in this byte so far are AB, BD
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
160 and BF. Per my current understanding, in a "healthy" FFS exactly one sector
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
161 will have AB in its header, exactly one will have BF, and the rest will have
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
162 BD. The meanings are (or appear to be):
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
163
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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164 AB: the sector holds a vital data structure which I have called the active
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
165 index block;
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
166 BD: the sector holds regular data;
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
167 BF: the sector is blank except for the header, can be turned into a new AB or
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
168 BD.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
169
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
170 (Note that a flash program operation, which can turn 1s into 0s but not the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
171 other way around, can turn BF into either AB or BD - but neither AB nor BD can
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
172 be turned into any other valid value.)
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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diff changeset
173
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
174 In a "virgin" FFS image (as explained above) the first FFS sector is AB, the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
175 last one is BF, and the ones in between are BDs.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
176
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
177 An FFS read operation (a search for a given pathname, or a listing of all
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
178 present directories and files) needs to start with locating the active index
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
179 block - the FFS sector with AB in the header. Following this header, which is
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
180 treated as being 16 bytes long (almost everything in Mokopir-FFS is aligned on
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
181 16-byte boundaries), the active index block contains a linear array of 16-byte
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
182 records, each record describing an FFS object: directory, file or file
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
183 continuation chunk.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
184
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
185 Here is my current understanding of the 16-byte index block record structure:
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
186
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
187 2 bytes: Length of the described chunk in bytes
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
188 1 byte: Purpose/meaning not understood, ignored by my current code
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
189 1 byte: Object type
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
190 2 bytes: Descendant pointer
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
191 2 bytes: Sibling pointer
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
192 4 bytes: Data pointer
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
193 4 bytes: Purpose/meaning not understood, ignored by my current code
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
194
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
195 (On the Calypso phones of interest, all multibyte fields are in the native
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
196 little-endian byte order of the ARM7TDMI processor.)
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
197
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
198 The active index block gets filled with these records as objects are created;
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
199 the first record goes right after the 'Ffs#'...AB header (padded to 16 bytes);
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
200 the last record (at any given moment) is followed by blank flash for the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
201 remainder of the sector. Records thus appear in the order in which they are
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
202 created, which bears no direct relation to the directory tree structure.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
203
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
204 The objects, each described by a record in the index block, are organized into
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
205 a tree structure by the descendant and sibling pointers, plus the object type
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
206 indicator byte. Let's start with the latter; the following objtype byte values
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
207 have been observed:
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
208
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
209 00: deleted object - a read-only implementation should ignore everything except
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
210 the descendant and sibling pointers. (A write-capable implementation would
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
211 need more care - it would need a way of reclaiming dirty flash space taken
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
212 up by deleted/overwritten files.)
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
213
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
214 E1: a special file - see the description of the /.journal file further down
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
215 F1: a regular file (head chunk thereof)
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
216 F2: a directory
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
217 F4: file continuation chunk (explained below)
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
218
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
219 Each record in the index block has an associated chunk in one of the data
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
220 sectors; the index record contains fields giving the address and length of this
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
221 chunk. The length of a chunk is always a nonzero multiple of 16 bytes, and is
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
222 stored (as a number in bytes) in the first 16-bit field of the 16-byte index
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
223 entry. The address of each chunk is given by the data pointer field of the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
224 index record, and it is reckoned in 16-byte units (thereby 16-byte alignment is
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
225 required) from the beginning of the FFS sector group in the flash address space.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
226
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
227 For objects of type F1 and F2 (regular files and directories) the just-described
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
228 chunk begins with the name of the file or subdirectory as a NUL-terminated ASCII
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
229 string. This name is just for the current level of the directory tree, just
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
230 like in UNIX directories, thus one will have chunk names like gsm, l3, eplmn
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
231 etc, rather than /gsm/l3/eplmn. One practical effect is that one can't readily
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
232 see pathnames or any of the directory structure by looking at an FFS image as a
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
233 raw hex dump; the structure is only revealed when one uses a parsing program
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
234 like those which accompany this document.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
235
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
236 In the case of directories, the "chunk" part of the object contains only the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
237 name of the directory itself, padded with FFs to a 16-byte boundary. For
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
238 example, an FFS directory named /gsm would be represented by an object
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
239 consisting of two flash writes: a 16-byte entry in the active index block, with
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
240 the object type byte set to F2, and a corresponding 16-byte chunk in one of the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
241 data sectors, with the 16 bytes containing "gsm", a terminating NUL byte, and
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
242 12 FF bytes to pad up to 16. In the case of files, this name may be followed
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
243 by the first chunk of file data content, as explained further down.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
244
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
245 In order to parse the FFS directory tree (whether the objective is to dump the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
246 whole thing recursively or to find a specific file given a pathname), one needs
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
247 to first (well, after finding the active AB block) find the root directory node.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
248 The root directory object is similar to other directory objects: it has a type
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
249 of F2, and an associated chunk of 16 bytes in one of the data sectors. The
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
250 latter contains the name of the root node: on the Pirelli it is "/", whereas on
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
251 my GTA02 it is "/ffs-root".
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
252
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
253 The astute reader should notice that it really makes no sense to store a name
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
254 for the root node, and indeed, this name plays no part in the traversal of the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
255 directory tree given an absolute pathname. But instead this name, or rather
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
256 its first character, appears to be used for the purpose of locating the root
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
257 node itself. At first I had assumed that the index record for the root node is
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
258 always the first record in the active index block right after the signature
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
259 header - that is how it is in "virgin" FFS images, and also in some quite non-
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
260 virgin ones I have pulled from my daily-use Pirelli. Naturally my first version
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
261 of the Mokopir-FFS (then called MysteryFFS) extraction utility expected the root
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
262 node to always be at index #1. But then I got some additional Pirelli phones,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
263 and discovered that in certain cases, index record #1 is a deleted object (the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
264 original root node which has been deleted), and the new active root node is
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
265 somewhere in the middle of the index!
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
266
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
267 Thus it appears that in order to find the active root node, one needs to scan
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
268 the active index block linearly from the beginning (disregarding the tree
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
269 structure pointers in this initial pass), looking for a non-deleted object of
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
270 type F2 (a directory) whose corresponding name chunk sports a name beginning
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
271 with the '/' character. (Anyone who's been raised in UNIX will immediately
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
272 know that the path separator character '/' is the only character other than NUL
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
273 that's absolutely forbidden in the individual filenames - so this special
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
274 "root node name" is the only case of a '/' character appearing in what would
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
275 otherwise be a regular filename.)
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
276
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
277 [What causes the root node to be somewhere other than at index #1? I assume it
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
278 has to do with the dirty space reclamation / data movement algorithm. In a
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
279 "virgin" FFS image the very first sector is the active index block, and the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
280 following sector is the first to hold chunks, beginning with the name chunk of
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
281 the root node. Now what happens if all data in that sector aside from the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
282 root node name and some other mostly-static directory names becomes dirty,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
283 i.e., belonging to deleted or overwritten files? How would that flash space
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
284 get reclaimed? I assume that the FFS firmware algorithm moves all still-active
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
285 chunks to a new flash sector, invalidating the old copies - turning the latter
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
286 into deleted objects. The root node will be among them. Then at some point
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
287 the active index block is going to fill up too, and will need to be rewritten
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
288 into a new sector - at which point the previously-deleted index entries are
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
289 omitted and the root node becomes #1 again...]
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
290
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
291 Tree structure
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
292
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
293 Once the root node has been found, the descendant and sibling pointers are used
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
294 to traverse the tree structure. For each directory object, including the root
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
295 node, the descendant pointer points to the first child object of this directory:
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
296 the first file or subdirectory contained therein. (Descendant and sibling
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
297 pointers take the form of index numbers in the active index block. A "nil"
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
298 pointer is indicated by all 1s (FFFF) - the usual all-0s NULL pointer convention
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
299 couldn't be used because it's flash, where the blank state is all 1s.) If the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
300 descendant pointer of a directory object is nil, that means an empty directory.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
301 The sibling pointer of each file or directory points to its next sibling, i.e.,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
302 the next member of the same parent directory. The sibling pointer of the root
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
303 node is nil.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
304
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
305 Data content of files
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
306
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
307 Objects of type F1 are the head chunks of files. Each file has a head chunk,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
308 and may or may not have continuation chunks. More precisely, the head chunk
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
309 may contain only the name (or viewed alternatively, 0 bytes of data), or it may
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
310 contain a nonzero number of payload bytes; orthogonally to this variability,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
311 there may or may not be continuation chunk(s) present.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
312
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
313 Continuation chunks
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
314
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
315 The descendant pointer of each file head object (the object of type F1, the one
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
316 reached by traversing the directory tree) indicates whether or not there are
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
317 any continuation chunks present. If this descendant pointer is nil, there are
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
318 no continuation chunks; otherwise it points to the first continuation chunk
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
319 object. File continuation objects have type F4, don't have any siblings (the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
320 sibling pointer is nil - but see below regarding relocated chunks), and the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
321 descendant pointer of each continuation object points to the next continuation
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
322 object, if there is one - nil otherwise.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
323
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
324 Payload data delineation
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
325
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
326 Each chunk, whether head or continuation, always has a length that is a nonzero
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
327 multiple of 16 bytes. The length of the chunk here means the amount of flash
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
328 space it occupies in its data sector - which is NOT equal to the payload data
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
329 length.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
330
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
331 The head chunk of each file begins with the filename, terminated by a NUL byte.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
332 If there are any payload data bytes present in this head chunk (I'll explain
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
333 momentarily how you would tell), the byte immediately after the NUL that
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
334 terminates the filename is the first byte of the payload. In the case of a
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
335 continuation chunk, there is no filename and the first byte of the chunk is the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
336 first byte of that chunk's portion of the user data payload.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
337
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
338 Each data-containing chunk (head or continuation) has the following termination
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
339 after the last byte of that chunk's payload data: one byte of 00, followed by
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
340 however many bytes are needed ([0,15] range) of FFs to pad to a 16-byte
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
341 boundary. A file head chunk that has no payload data has the same format as a
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
342 directory name chunk: filename followed by its terminating NUL followed by
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
343 [0,15] bytes of FFs to pad to the next 16-byte boundary.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
344
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
345 When working with a head chunk, find the beginning of possible payload data (1
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
346 byte after the filename terminating NUL) and find the end per the standard
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
347 termination logic: scanning from the end of the chunk, skip FFs until 00 is
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
348 found (encountering anything else is an error). If the head chunk has no data,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
349 the effective data length (end_pointer - start_pointer) will be 0 or -1. (The
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
350 latter possibility is the most likely, as there will normally be a "shared" 00
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
351 byte, serving as both the filename terminator and the 00 before the padding
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
352 FF bytes.)
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
353
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
354 Relocated chunks
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
355
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
356 Let's go back to the scenario in which a particular data sector is full (no more
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
357 usable free space left) and contains a mixture of active and dirty (deleted or
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
358 invalidated) data. How does the dirty flash space get reclaimed, so that the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
359 amount of available space (blank flash ready to hold new data) becomes equal to
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
360 the total FFS size minus the total size of active files and overhead? It can
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
361 only be done by relocating the still-active objects from the full sector to a
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
362 new one, invalidating the old copies, and once the old sector consists of
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
363 nothing but invalidated data, subjecting it to flash erasure.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
364
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
365 So how do the active FFS objects get relocated from a "condemned" sector to a
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
366 new one? If the object is a directory, a new index entry is created, pointing
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
367 to the newly relocated name chunk, but it is then made to fit into the old tree
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
368 structure without disrupting the latter: the new index entry is added at the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
369 tail of the sibling-chain of the parent directory's descendants, the old index
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
370 entry for the same directory is invalidated (as if the directory were rmdir'ed),
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
371 and the descendant pointer of the newly written index entry is set to a copy of
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
372 the descendant pointer from the old index entry for the same directory. The
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
373 same approach is used when the head chunk of a file needs to be relocated; in
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
374 both cases a read-only FFS implementation doesn't need to do anything special to
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
375 support reading file and directory objects that have been relocated in this
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
376 manner.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
377
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
378 However, if the relocated object is a file continuation chunk, then the manner
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
379 in which such objects get relocated does affect file reading code. What if a
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
380 chunk in the middle of a chain linked by "descend" pointers needs to be moved?
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
381 What happens in this case is that the old copy of the chunk gets invalidated
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
382 (the object type byte turned to 00) like in the other object relocating cases,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
383 and the sibling pointer of that old index entry (which was originally FFFF as
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
384 continuation objects have no siblings) is set to point to the new index entry
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
385 for the same chunk. The "descend" pointer in the new index entry is a copy of
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
386 that pointer from the old index entry.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
387
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
388 The manner of chunk relocation just described has been observed in the FFS
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
389 images read out of my most recent batch of Pirelli phones - the same ones in
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
390 which the root directory object is not at index #1. Thinking about it as I
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
391 write this, I've realized that the way in which continuation objects get
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
392 relocated is exactly the same as for other object types - thus the compaction
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
393 code in the firmware doesn't need to examine what object type it is moving.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
394 However, the case of continuation chunk relocation deserves special attention
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
395 because it affects a read-only implementation like ours - the utilities whose
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
396 source accompanies this document used to fail on these FFS images until I
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
397 implemented the following additional handling:
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
398
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
399 When following the chunk chain of a file, normally the only object type that's
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
400 expected is F4 - any other object type is an error. However, as a result of
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
401 chunk relocation, one can also encounter deleted objects, i.e., type == 00.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
402 If such a deleted object is encountered, follow its sibling pointer, which must
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
403 be non-nil.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
404
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
405 Journal file
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
406
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
407 Every Mokopir-FFS image I've seen so far contains a special file named
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
408 /.journal; this file is special in the following ways:
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
409
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
410 * The object type byte is E1 instead of F1;
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
411 * Unlike regular files, this special file is internally-writable.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
412
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
413 What I mean by the above is that regular files are mostly immutable: once a
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
414 file has been created with some data content in the head chunk, it can only be
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
415 either appended to (one or more continuation chunks added), or overwritten by
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
416 creating a new file with the same name at the same level in the tree hierarchy
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
417 and invalidating the old one. But the special /.journal file is different: I
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
418 have never observed it to consist of more than the head chunk, and this head
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
419 chunk is pre-allocated with some largish and apparently fixed length (4 KiB on
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
420 my GTA02, 16 KiB on the Pirelli). This pre-allocated chunk contains what look
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
421 like 16-byte records at the beginning (on the first 4-byte boundary after the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
422 NUL terminating the ".journal" name), followed by blank flash for the remainder
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
423 of the pre-allocated chunk - so it surely looks like new flash writes happen
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
424 within this chunk.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
425
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
426 I do not currently know the purpose of this /.journal file or the meaning of the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
427 records it seems to contain. This understanding would surely be needed if one
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
428 wanted to create FFS images from scratch or to implement FFS write operations,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
429 but I reason that a read-only implementation can get away with simply ignoring
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
430 this file. I reason that this file can't be necessary in order to parse an FFS
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
431 image for reading because one needs to parse the tree structure first in order
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
432 to locate this journal file itself.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
433
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
434 -------------------------------------------------------------------------------
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
435
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
436 That's all I can think of right now. If anything is unclear, see the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
437 accompanying source code for the listing/extraction utilities: with the general
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
438 explanation given by this document, it should be clear what my code does and
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
439 why. And if a given piece of knowledge is found neither in this document nor
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
440 in my source code, then I don't know it myself either, and my read-only
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
441 Mokopir-FFS implementation makes do without it.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
442
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
443 All knowledge contained herein has been recovered by reverse engineering.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
444 Believe it or not, I have figured it out by staring at the hex dump of FFS
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
445 sectors, reasoning about how one could possibly implement an FFS given the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
446 requirement of dynamic writability and the physical constraints of flash memory,
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
447 and writing listing/extraction test code iteratively until I got something that
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
448 appears to correctly parse all FFS images available to me - the result is the
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
449 code in this package.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
450
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
451 I never got as far as attempting to locate the FFS implementation routines
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
452 within the proprietary firmware binary code images, and I haven't found an
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
453 implementation of this particular FFS in any of the leaked sources yet either.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
454 The TSM30 code doesn't seem to be of any use as its FFS appears to be totally
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
455 different. As to the more recently found LoCosto code leak, I found that one a
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
456 few days *after* I got the Moko/Pirelli "MysteryFFS" reverse-engineered on my
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
457 own, and when I did look at the FFS in the LoCosto code later, I saw what seems
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
458 to be a different FFS as well.
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
459
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
460 Michael Spacefalcon
4eeab025b502 doc/TIFFS-old-description: the original description from SE 52 Mes 16
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
parents:
diff changeset
461 SE 52 Mes 16