FreeCalypso > hg > freecalypso-tools
annotate doc/TIFFS-old-description @ 619:f82551c77e58
libserial-newlnx: ASYNC_LOW_LATENCY patch reverted
Reports from Das Signal indicate that loadtools performance on Debian
is about the same as on Slackware, and that including or omitting the
ASYNC_LOW_LATENCY patch from Serg makes no difference. Because the
patch in question does not appear to be necessary, it is being reverted
until and unless someone other than Serg reports an actual real-world
system on which loadtools operation times are slowed compared to the
Mother's Slackware reference and on which Slackware-like performance
can be restored by setting the ASYNC_LOW_LATENCY flag.
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Thu, 27 Feb 2020 01:09:48 +0000 |
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1 The description of TIFFS that follows was originally written in the summer of |
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2 SE52 (A.D. 2013), before the major TI source discoveries which happened later |
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3 that year. The text following the dividing line below has not been edited in |
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4 content since it was written; for a newer write-up based on the current source- |
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5 enabled understanding and reflecting the current FreeCalypso plans with respect |
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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 |
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10 This is a description, based on reverse engineering, of the flash file system |
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11 (FFS) implemented in Pirelli's original firmware for the DP-L10 GSM/WiFi dual |
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12 mode mobile phone, and in the Closedmoko GTA0x modem firmware. Not knowing the |
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13 "proper" name for this FFS, and needing _some_ identifier to refer to it, I |
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14 have named it Mokopir-FFS, from "Moko" and "Pirelli" - sometimes abbreviated |
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15 further to MPFFS. |
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16 |
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17 (I have previously called the FFS in question MysteryFFS; but now that I've |
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18 successfully reverse-engineered it, it isn't as much of a mystery any more :-) |
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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 |
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24 * The file system API that must be implemented inside the proprietary firmware |
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25 appears to use UNIX-style pathnames; doing strings on firmware images reveals |
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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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34 Parsing the corresponding FFS image with tools included in the present |
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35 package has confirmed that the directory structure implied by these pathnames |
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36 does indeed exist in the FFS. |
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37 |
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38 * Absolutely no DOS-ish semantics seen anywhere: no 8.3 filenames and no |
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39 colon-separated device names (seen in the TSM30 file system source, for |
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40 example) are visible in the Closedmoko/Pirelli FFS. |
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41 |
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42 * File contents are stored uncompressed, but not necessarily contiguous: one |
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43 could probably store a file in FFS which is bigger than the flash sector |
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44 size, it which case it can never be contiguous in a writable FFS (see below), |
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45 and the firmware implementation seems to limit chunk sizes to a fairly small |
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46 number: on the Pirelli phones all largish files are divided into chunks of |
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47 8 KiB each, and on my GTA02 the largest observed chunk size is only 2 KiB. |
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48 |
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49 The smaller files, like the IMEI and the firmware ID strings in my GTA02 FFS, |
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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 |
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53 each chunk (and consequently, in each file) can be known exactly in bytes, |
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54 with the files/chunks able to contain arbitrary binary data. (This property |
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55 may seem obvious or trivial, as all familiar UNIX and DOS file systems have |
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56 it, but contrast with RT-11 for example.) |
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57 |
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58 * The flash file system is a writable one: the running firmware can create, |
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59 delete and overwrite files (and possibly directories too) in the live FFS; |
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60 thus the FFS design is such that allows these operations to be performed |
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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 |
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64 is that I, or anyone else who can read this document and the accompanying |
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65 source for the listing/extraction utilities, can take a Mokopir-FFS image read |
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66 out of a device and see/extract its full content: the complete directory tree |
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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 |
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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 |
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72 for making modifications to the file or directory content of an existing image |
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73 and producing a content-modified image that is also valid; valid as in suitable |
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74 for the original proprietary firmware to make its normal read and write |
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75 operations without noticing anything amiss. |
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76 |
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77 Constructing "de novo" Mokopir-FFS images or modifying existing images in such |
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78 a way that they remain 100% valid for all read and write operations of the |
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79 original proprietary firmware would, at the very minimum, require an |
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80 understanding of the meaning of *all* fields of the on-media FFS format. Some |
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81 of these fields are still left as "non-understood" for now though: a read-only |
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82 implementation can get away with simply ignoring them, but a writer/generator |
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83 would have to put *something* in those fields. |
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84 |
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85 As you read the "read-only" description of the Mokopir-FFS on-media format in |
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86 the remainder of this document, it should become fairly obvious which pieces |
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87 are missing before our understanding of this FFS can be elevated to a |
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88 "writable" level. |
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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 |
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91 question (Closedmoko and Pirelli), it seems, at least to the present hacker, |
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92 that a read-only understanding of Mokopir-FFS should be sufficient: |
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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 |
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95 and the RF calibration data. The format of the former is obvious; the latter |
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96 not so much - but in any case, the information of interest is clearly of a |
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97 read-only nature. It's difficult to tell (or rather, I haven't bothered to |
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98 experiment enough) whether the Closedmoko firmware does any writes to FFS or |
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99 if the FFS is treated as read-only outside of the production line environment, |
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100 but in any case, it seems to me that for any 3rd party replacement firmware, |
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101 the best strategy would be to treat the FFS as a read-only source of IMEI and |
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102 RF calibration data, and nothing more. |
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103 |
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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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105 received SMS (and MMS/email/whatever), call history, UI settings, pictures |
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106 taken with the camera, and whatever else. It also stores a ton of files |
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107 which I can only presume were meant to be immutable except at the time of |
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108 firmware updates: graphics for the UI, ringtones, i18n UI strings, and even |
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109 "helper" firmware images for the WiFi and VoIP processors. However, no IMEI |
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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 |
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112 flash (in its own sector) outside of the FFS. |
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113 |
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114 Being able to parse FFS images extracted out of Pirelli phones "in vitro" |
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115 allows us to steal some of these helper files (UI artwork, ringtones, |
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116 WiFi/VoIP helpers), and some of these might even come useful to firmware |
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117 replacement projects, but it seems to me that a replacement firmware would |
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118 be better off using its own FFS design for storing user data, and as to |
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119 retrieving the original IMEI and RF calibration data, the original FFS isn't |
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120 of any use for that anyway. |
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121 |
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122 ======================= |
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123 Moko/Pirelli FFS format |
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124 ======================= |
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125 |
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126 OK, now that I'm done with the introduction, we can get to the actual |
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127 Mokopir-FFS format. |
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128 |
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129 * On the GTA0x modem (or at least on my GTA02; my sample size is 1) the FFS |
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130 occupies 7 flash sectors of 64 KiB each at offsets 0x380000 through 0x3E0000, |
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131 inclusive. |
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132 |
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133 (The 4 MiB NOR flash chip used by Closedmoko has an independent R/W bank |
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134 division between the first 3 MiB and the last 1 MiB. The first 3 MiB are used |
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135 to hold the field-flashable closed firmware images distributed as *.m0 files; |
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136 the independent last megabyte holds the FFS, and thus the FW could be |
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137 implemented to do FFS writes while running from flash in the main bank. |
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138 Less than half of that last megabyte appears to be used for the FFS though; |
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139 the rest appears to be unused - blank flash observed.) |
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140 |
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141 * On the Pirelli the FFS occupies 18 sectors of 256 KiB each at offsets 0 |
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142 through 0x440000 (inclusive) of the 2nd flash chip select, the one wired to |
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143 nCS3 on the Calypso. |
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144 |
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145 Each flash sector allocated to FFS begins with the following signature: |
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146 |
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147 00000000: 46 66 73 23 10 02 xx yy zz FF FF FF FF FF FF FF Ffs#............ |
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148 |
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149 The bytes shown as xx and yy above serve a non-understood purpose; as a guess, |
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150 they may hold some info for the flash wear leveling algorithm: in a "virgin" |
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151 FFS image like that found in my GTA02 (which never had a SIM card in it and |
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152 never made or received a call) or read out of a "virgin" Pirelli phone that |
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153 hasn't seen any active use yet, both of these bytes are FFs, but when I look at |
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154 FFS images read out of the Pirelli which I currently use as my everyday-use |
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155 cellphone, I see other values in sectors which must have been erased and |
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156 rewritten. A read-only implementation can ignore these bytes, as mine does. |
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157 |
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158 The byte shown as zz is more important though, even to a read-only |
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159 implementation. The 3 values I've encountered in this byte so far are AB, BD |
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160 and BF. Per my current understanding, in a "healthy" FFS exactly one sector |
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161 will have AB in its header, exactly one will have BF, and the rest will have |
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parents:
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162 BD. The meanings are (or appear to be): |
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163 |
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164 AB: the sector holds a vital data structure which I have called the active |
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parents:
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165 index block; |
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166 BD: the sector holds regular data; |
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167 BF: the sector is blank except for the header, can be turned into a new AB or |
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168 BD. |
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169 |
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170 (Note that a flash program operation, which can turn 1s into 0s but not the |
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parents:
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171 other way around, can turn BF into either AB or BD - but neither AB nor BD can |
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parents:
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172 be turned into any other valid value.) |
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173 |
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174 In a "virgin" FFS image (as explained above) the first FFS sector is AB, the |
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175 last one is BF, and the ones in between are BDs. |
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176 |
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177 An FFS read operation (a search for a given pathname, or a listing of all |
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178 present directories and files) needs to start with locating the active index |
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parents:
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179 block - the FFS sector with AB in the header. Following this header, which is |
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parents:
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180 treated as being 16 bytes long (almost everything in Mokopir-FFS is aligned on |
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parents:
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181 16-byte boundaries), the active index block contains a linear array of 16-byte |
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parents:
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182 records, each record describing an FFS object: directory, file or file |
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parents:
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183 continuation chunk. |
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parents:
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184 |
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185 Here is my current understanding of the 16-byte index block record structure: |
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186 |
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187 2 bytes: Length of the described chunk in bytes |
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188 1 byte: Purpose/meaning not understood, ignored by my current code |
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189 1 byte: Object type |
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parents:
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190 2 bytes: Descendant pointer |
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parents:
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191 2 bytes: Sibling pointer |
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Mychaela Falconia <falcon@freecalypso.org>
parents:
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192 4 bytes: Data pointer |
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parents:
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193 4 bytes: Purpose/meaning not understood, ignored by my current code |
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parents:
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194 |
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195 (On the Calypso phones of interest, all multibyte fields are in the native |
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parents:
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196 little-endian byte order of the ARM7TDMI processor.) |
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parents:
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197 |
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198 The active index block gets filled with these records as objects are created; |
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199 the first record goes right after the 'Ffs#'...AB header (padded to 16 bytes); |
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200 the last record (at any given moment) is followed by blank flash for the |
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201 remainder of the sector. Records thus appear in the order in which they are |
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202 created, which bears no direct relation to the directory tree structure. |
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203 |
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204 The objects, each described by a record in the index block, are organized into |
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205 a tree structure by the descendant and sibling pointers, plus the object type |
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206 indicator byte. Let's start with the latter; the following objtype byte values |
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207 have been observed: |
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208 |
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209 00: deleted object - a read-only implementation should ignore everything except |
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210 the descendant and sibling pointers. (A write-capable implementation would |
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211 need more care - it would need a way of reclaiming dirty flash space taken |
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212 up by deleted/overwritten files.) |
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213 |
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214 E1: a special file - see the description of the /.journal file further down |
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215 F1: a regular file (head chunk thereof) |
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216 F2: a directory |
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217 F4: file continuation chunk (explained below) |
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218 |
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219 Each record in the index block has an associated chunk in one of the data |
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220 sectors; the index record contains fields giving the address and length of this |
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221 chunk. The length of a chunk is always a nonzero multiple of 16 bytes, and is |
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222 stored (as a number in bytes) in the first 16-bit field of the 16-byte index |
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223 entry. The address of each chunk is given by the data pointer field of the |
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224 index record, and it is reckoned in 16-byte units (thereby 16-byte alignment is |
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225 required) from the beginning of the FFS sector group in the flash address space. |
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226 |
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227 For objects of type F1 and F2 (regular files and directories) the just-described |
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228 chunk begins with the name of the file or subdirectory as a NUL-terminated ASCII |
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229 string. This name is just for the current level of the directory tree, just |
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230 like in UNIX directories, thus one will have chunk names like gsm, l3, eplmn |
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231 etc, rather than /gsm/l3/eplmn. One practical effect is that one can't readily |
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232 see pathnames or any of the directory structure by looking at an FFS image as a |
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233 raw hex dump; the structure is only revealed when one uses a parsing program |
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234 like those which accompany this document. |
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235 |
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236 In the case of directories, the "chunk" part of the object contains only the |
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237 name of the directory itself, padded with FFs to a 16-byte boundary. For |
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238 example, an FFS directory named /gsm would be represented by an object |
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239 consisting of two flash writes: a 16-byte entry in the active index block, with |
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240 the object type byte set to F2, and a corresponding 16-byte chunk in one of the |
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241 data sectors, with the 16 bytes containing "gsm", a terminating NUL byte, and |
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242 12 FF bytes to pad up to 16. In the case of files, this name may be followed |
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243 by the first chunk of file data content, as explained further down. |
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244 |
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245 In order to parse the FFS directory tree (whether the objective is to dump the |
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246 whole thing recursively or to find a specific file given a pathname), one needs |
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247 to first (well, after finding the active AB block) find the root directory node. |
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248 The root directory object is similar to other directory objects: it has a type |
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249 of F2, and an associated chunk of 16 bytes in one of the data sectors. The |
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250 latter contains the name of the root node: on the Pirelli it is "/", whereas on |
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251 my GTA02 it is "/ffs-root". |
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252 |
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253 The astute reader should notice that it really makes no sense to store a name |
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254 for the root node, and indeed, this name plays no part in the traversal of the |
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255 directory tree given an absolute pathname. But instead this name, or rather |
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256 its first character, appears to be used for the purpose of locating the root |
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257 node itself. At first I had assumed that the index record for the root node is |
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258 always the first record in the active index block right after the signature |
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259 header - that is how it is in "virgin" FFS images, and also in some quite non- |
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260 virgin ones I have pulled from my daily-use Pirelli. Naturally my first version |
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261 of the Mokopir-FFS (then called MysteryFFS) extraction utility expected the root |
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262 node to always be at index #1. But then I got some additional Pirelli phones, |
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263 and discovered that in certain cases, index record #1 is a deleted object (the |
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264 original root node which has been deleted), and the new active root node is |
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265 somewhere in the middle of the index! |
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266 |
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267 Thus it appears that in order to find the active root node, one needs to scan |
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268 the active index block linearly from the beginning (disregarding the tree |
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269 structure pointers in this initial pass), looking for a non-deleted object of |
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270 type F2 (a directory) whose corresponding name chunk sports a name beginning |
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271 with the '/' character. (Anyone who's been raised in UNIX will immediately |
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272 know that the path separator character '/' is the only character other than NUL |
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273 that's absolutely forbidden in the individual filenames - so this special |
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274 "root node name" is the only case of a '/' character appearing in what would |
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275 otherwise be a regular filename.) |
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276 |
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277 [What causes the root node to be somewhere other than at index #1? I assume it |
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278 has to do with the dirty space reclamation / data movement algorithm. In a |
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279 "virgin" FFS image the very first sector is the active index block, and the |
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280 following sector is the first to hold chunks, beginning with the name chunk of |
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281 the root node. Now what happens if all data in that sector aside from the |
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282 root node name and some other mostly-static directory names becomes dirty, |
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283 i.e., belonging to deleted or overwritten files? How would that flash space |
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284 get reclaimed? I assume that the FFS firmware algorithm moves all still-active |
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285 chunks to a new flash sector, invalidating the old copies - turning the latter |
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286 into deleted objects. The root node will be among them. Then at some point |
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287 the active index block is going to fill up too, and will need to be rewritten |
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288 into a new sector - at which point the previously-deleted index entries are |
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289 omitted and the root node becomes #1 again...] |
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290 |
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291 Tree structure |
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292 |
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293 Once the root node has been found, the descendant and sibling pointers are used |
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294 to traverse the tree structure. For each directory object, including the root |
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295 node, the descendant pointer points to the first child object of this directory: |
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296 the first file or subdirectory contained therein. (Descendant and sibling |
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297 pointers take the form of index numbers in the active index block. A "nil" |
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298 pointer is indicated by all 1s (FFFF) - the usual all-0s NULL pointer convention |
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299 couldn't be used because it's flash, where the blank state is all 1s.) If the |
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300 descendant pointer of a directory object is nil, that means an empty directory. |
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301 The sibling pointer of each file or directory points to its next sibling, i.e., |
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302 the next member of the same parent directory. The sibling pointer of the root |
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303 node is nil. |
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304 |
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305 Data content of files |
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306 |
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307 Objects of type F1 are the head chunks of files. Each file has a head chunk, |
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308 and may or may not have continuation chunks. More precisely, the head chunk |
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309 may contain only the name (or viewed alternatively, 0 bytes of data), or it may |
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310 contain a nonzero number of payload bytes; orthogonally to this variability, |
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311 there may or may not be continuation chunk(s) present. |
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312 |
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313 Continuation chunks |
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314 |
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315 The descendant pointer of each file head object (the object of type F1, the one |
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316 reached by traversing the directory tree) indicates whether or not there are |
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317 any continuation chunks present. If this descendant pointer is nil, there are |
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318 no continuation chunks; otherwise it points to the first continuation chunk |
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319 object. File continuation objects have type F4, don't have any siblings (the |
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320 sibling pointer is nil - but see below regarding relocated chunks), and the |
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321 descendant pointer of each continuation object points to the next continuation |
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322 object, if there is one - nil otherwise. |
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323 |
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324 Payload data delineation |
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325 |
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326 Each chunk, whether head or continuation, always has a length that is a nonzero |
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327 multiple of 16 bytes. The length of the chunk here means the amount of flash |
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328 space it occupies in its data sector - which is NOT equal to the payload data |
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329 length. |
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330 |
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331 The head chunk of each file begins with the filename, terminated by a NUL byte. |
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332 If there are any payload data bytes present in this head chunk (I'll explain |
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333 momentarily how you would tell), the byte immediately after the NUL that |
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334 terminates the filename is the first byte of the payload. In the case of a |
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335 continuation chunk, there is no filename and the first byte of the chunk is the |
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336 first byte of that chunk's portion of the user data payload. |
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337 |
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338 Each data-containing chunk (head or continuation) has the following termination |
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339 after the last byte of that chunk's payload data: one byte of 00, followed by |
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340 however many bytes are needed ([0,15] range) of FFs to pad to a 16-byte |
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341 boundary. A file head chunk that has no payload data has the same format as a |
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342 directory name chunk: filename followed by its terminating NUL followed by |
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343 [0,15] bytes of FFs to pad to the next 16-byte boundary. |
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344 |
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345 When working with a head chunk, find the beginning of possible payload data (1 |
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346 byte after the filename terminating NUL) and find the end per the standard |
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347 termination logic: scanning from the end of the chunk, skip FFs until 00 is |
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348 found (encountering anything else is an error). If the head chunk has no data, |
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349 the effective data length (end_pointer - start_pointer) will be 0 or -1. (The |
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350 latter possibility is the most likely, as there will normally be a "shared" 00 |
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351 byte, serving as both the filename terminator and the 00 before the padding |
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352 FF bytes.) |
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353 |
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354 Relocated chunks |
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355 |
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356 Let's go back to the scenario in which a particular data sector is full (no more |
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357 usable free space left) and contains a mixture of active and dirty (deleted or |
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358 invalidated) data. How does the dirty flash space get reclaimed, so that the |
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359 amount of available space (blank flash ready to hold new data) becomes equal to |
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360 the total FFS size minus the total size of active files and overhead? It can |
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361 only be done by relocating the still-active objects from the full sector to a |
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362 new one, invalidating the old copies, and once the old sector consists of |
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363 nothing but invalidated data, subjecting it to flash erasure. |
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364 |
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365 So how do the active FFS objects get relocated from a "condemned" sector to a |
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366 new one? If the object is a directory, a new index entry is created, pointing |
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367 to the newly relocated name chunk, but it is then made to fit into the old tree |
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368 structure without disrupting the latter: the new index entry is added at the |
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369 tail of the sibling-chain of the parent directory's descendants, the old index |
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370 entry for the same directory is invalidated (as if the directory were rmdir'ed), |
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371 and the descendant pointer of the newly written index entry is set to a copy of |
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372 the descendant pointer from the old index entry for the same directory. The |
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373 same approach is used when the head chunk of a file needs to be relocated; in |
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374 both cases a read-only FFS implementation doesn't need to do anything special to |
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|
375 support reading file and directory objects that have been relocated in this |
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376 manner. |
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|
377 |
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378 However, if the relocated object is a file continuation chunk, then the manner |
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379 in which such objects get relocated does affect file reading code. What if a |
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380 chunk in the middle of a chain linked by "descend" pointers needs to be moved? |
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381 What happens in this case is that the old copy of the chunk gets invalidated |
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382 (the object type byte turned to 00) like in the other object relocating cases, |
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383 and the sibling pointer of that old index entry (which was originally FFFF as |
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parents:
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|
384 continuation objects have no siblings) is set to point to the new index entry |
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385 for the same chunk. The "descend" pointer in the new index entry is a copy of |
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386 that pointer from the old index entry. |
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parents:
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|
387 |
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388 The manner of chunk relocation just described has been observed in the FFS |
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parents:
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|
389 images read out of my most recent batch of Pirelli phones - the same ones in |
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390 which the root directory object is not at index #1. Thinking about it as I |
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parents:
diff
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|
391 write this, I've realized that the way in which continuation objects get |
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Mychaela Falconia <falcon@freecalypso.org>
parents:
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|
392 relocated is exactly the same as for other object types - thus the compaction |
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Mychaela Falconia <falcon@freecalypso.org>
parents:
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|
393 code in the firmware doesn't need to examine what object type it is moving. |
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parents:
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|
394 However, the case of continuation chunk relocation deserves special attention |
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Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
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|
395 because it affects a read-only implementation like ours - the utilities whose |
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Mychaela Falconia <falcon@freecalypso.org>
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396 source accompanies this document used to fail on these FFS images until I |
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397 implemented the following additional handling: |
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398 |
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399 When following the chunk chain of a file, normally the only object type that's |
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400 expected is F4 - any other object type is an error. However, as a result of |
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401 chunk relocation, one can also encounter deleted objects, i.e., type == 00. |
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402 If such a deleted object is encountered, follow its sibling pointer, which must |
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403 be non-nil. |
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404 |
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405 Journal file |
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406 |
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407 Every Mokopir-FFS image I've seen so far contains a special file named |
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408 /.journal; this file is special in the following ways: |
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409 |
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410 * The object type byte is E1 instead of F1; |
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411 * Unlike regular files, this special file is internally-writable. |
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412 |
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413 What I mean by the above is that regular files are mostly immutable: once a |
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414 file has been created with some data content in the head chunk, it can only be |
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415 either appended to (one or more continuation chunks added), or overwritten by |
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416 creating a new file with the same name at the same level in the tree hierarchy |
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417 and invalidating the old one. But the special /.journal file is different: I |
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418 have never observed it to consist of more than the head chunk, and this head |
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419 chunk is pre-allocated with some largish and apparently fixed length (4 KiB on |
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420 my GTA02, 16 KiB on the Pirelli). This pre-allocated chunk contains what look |
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421 like 16-byte records at the beginning (on the first 4-byte boundary after the |
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422 NUL terminating the ".journal" name), followed by blank flash for the remainder |
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423 of the pre-allocated chunk - so it surely looks like new flash writes happen |
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424 within this chunk. |
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425 |
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426 I do not currently know the purpose of this /.journal file or the meaning of the |
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427 records it seems to contain. This understanding would surely be needed if one |
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428 wanted to create FFS images from scratch or to implement FFS write operations, |
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429 but I reason that a read-only implementation can get away with simply ignoring |
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430 this file. I reason that this file can't be necessary in order to parse an FFS |
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431 image for reading because one needs to parse the tree structure first in order |
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432 to locate this journal file itself. |
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433 |
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434 ------------------------------------------------------------------------------- |
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435 |
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436 That's all I can think of right now. If anything is unclear, see the |
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437 accompanying source code for the listing/extraction utilities: with the general |
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438 explanation given by this document, it should be clear what my code does and |
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439 why. And if a given piece of knowledge is found neither in this document nor |
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440 in my source code, then I don't know it myself either, and my read-only |
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441 Mokopir-FFS implementation makes do without it. |
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442 |
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443 All knowledge contained herein has been recovered by reverse engineering. |
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444 Believe it or not, I have figured it out by staring at the hex dump of FFS |
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445 sectors, reasoning about how one could possibly implement an FFS given the |
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446 requirement of dynamic writability and the physical constraints of flash memory, |
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447 and writing listing/extraction test code iteratively until I got something that |
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448 appears to correctly parse all FFS images available to me - the result is the |
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449 code in this package. |
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450 |
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451 I never got as far as attempting to locate the FFS implementation routines |
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452 within the proprietary firmware binary code images, and I haven't found an |
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453 implementation of this particular FFS in any of the leaked sources yet either. |
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454 The TSM30 code doesn't seem to be of any use as its FFS appears to be totally |
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455 different. As to the more recently found LoCosto code leak, I found that one a |
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456 few days *after* I got the Moko/Pirelli "MysteryFFS" reverse-engineered on my |
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457 own, and when I did look at the FFS in the LoCosto code later, I saw what seems |
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458 to be a different FFS as well. |
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459 |
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460 Michael Spacefalcon |
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461 SE 52 Mes 16 |