IBoot (Bootloader)

iBoot is Apple's stage 2 bootloader for all of the devices. It runs what is known as Recovery Mode. It has an interactive interface which can be used over USB or serial.

Bootrom
The bootrom also goes by the name "iBoot." The list of bootroms can be found on their own page.

Extract and Disassemble
To extract the bootloader and disassemble using IDA, follow the following steps: "iBoot for ...., Copyright 2011, Apple Inc." if you cat (i.e. type) the file.  remove the img3 header - the good stuff starts at offset 0x40 (i.e. 64) - using dd (skip=1 bs=64) or some other tool Load in IDA. Set processor to ARM. Rebase program (Edit&#8594;Segments&#8594;Rebase Program) to 0x5FF00000 (for iBoot in iOS 5). You should see something like:
 * 1) obtain the bootloader from the iPSW. This file is in the  subdir, e.g. , where the "n81ap", "k90", etc.. are for the i-Device type
 * 2) run xpwntool with the proper key (from elsewhere in this Wiki)
 * 3) Make sure the decryption was successful - if it is, you should see:

ROM:5FF00000 loc_5FF00000                           ; CODE XREF: ROM:5FF00078�j ROM:5FF00000                B       loc_5FF00040        ; Used for Reset - This is where we start ROM:5FF00004 ; --- ROM:5FF00004                LDR     PC, =sub_5FF16FB4   ; Used for Undef ROM:5FF00008 ; --- ROM:5FF00008                LDR     PC, =sub_5FF16FEC   ; Used for SWI ROM:5FF0000C ; --- ROM:5FF0000C                LDR     PC, =sub_5FF17024   ; Used for Prefabt ROM:5FF00010 ; --- ROM:5FF00010                LDR     PC, =sub_5FF17060   ; Used for DataAbt ROM:5FF00014 ; --- ROM:5FF00014                LDR     PC, =loc_5FF17098   ; Used for AddrExc ROM:5FF00018 ; --- ROM:5FF00018                LDR     PC, =loc_5FF16F24   ; Used for IRQ ROM:5FF0001C ; --- ROM:5FF0001C                LDR     PC, =sub_5FF16F6C   ; Probably FIQ, need to verify this ROM:5FF00020 ; --- ROM:5FF00020                SVCPL   0xF00040 ROM:5FF00020 ; --- ROM:5FF00024 off_5FF00024   DCD sub_5FF16FB4        ; DATA XREF: ROM:5FF00004�r ROM:5FF00028 off_5FF00028   DCD sub_5FF16FEC        ; DATA XREF: ROM:5FF00008�r ROM:5FF0002C off_5FF0002C   DCD sub_5FF17024        ; DATA XREF: ROM:5FF0000C�r ROM:5FF00030 off_5FF00030   DCD sub_5FF17060        ; DATA XREF: ROM:5FF00010�r ROM:5FF00034 off_5FF00034   DCD loc_5FF17098        ; DATA XREF: ROM:5FF00014�r ROM:5FF00038 off_5FF00038   DCD loc_5FF16F24        ; DATA XREF: ROM:5FF00018�r ROM:5FF0003C off_5FF0003C   DCD sub_5FF16F6C        ; DATA XREF: ROM:5FF0001C�r ROM:5FF00040 ; --- ROM:5FF00040 ROM:5FF00040 loc_5FF00040                           ; CODE XREF: ROM:loc_5FF00000�j ROM:5FF00040                ADR     R0, loc_5FF00000   <-- The address we rebased to ROM:5FF00044                 LDR     R1, =loc_5FF00000 ROM:5FF00048                CMP     R0, R1 ROM:5FF0004C                 CMP     R0, R1 ROM:5FF00050                 BEQ     loc_5FF0007C ... ... ROM:5FF000E8 loc_5FF000E8                           ; CODE XREF: ROM:5FF000F0�j ROM:5FF000E8                CMP     R0, R1 ROM:5FF000EC                 STRLT   R2, [R0],#4 ROM:5FF000F0                BLT     loc_5FF000E8 ROM:5FF000F4                LDR     R0, =(_ibootStart+1) ROM:5FF000F8                MOV     LR, PC ROM:5FF000FC                 BX      R0 ; _ibootStart ROM:5FF00100 ROM:5FF00100 loc_5FF00100                           ; CODE XREF: ROM:loc_5FF00100�j ROM:5FF00100                B       loc_5FF00100

Where iBootStart (not the official Apple Symbol, of course) can be seen at:

ROM:5FF00BA4 _ibootStart                            ; CODE XREF: ROM:5FF000FC�p ROM:5FF00BA4                                        ; DATA XREF: ROM:5FF000F4�o ... ROM:5FF00BA4                PUSH    {R7,LR} ROM:5FF00BA6                MOV     R7, SP ROM:5FF00BA8                 LDR     R0, =aIbootStart ; "\niBoot start\n" ROM:5FF00BAA                BL      loc_5FF233C4 ROM:5FF00BAE                MOVS    R0, #0 ROM:5FF00BB0                BL      loc_5FF16E54 ROM:5FF00BB4                BL      loc_5FF1570C ROM:5FF00BB8                BL      loc_5FF143A8 ROM:5FF00BBC                BL      unk_5FF15264 ROM:5FF00BC0                LDR     R0, =aMain      ; "main" ..

Flow of iBoot (1219 - 5.0.x)
iBoot is quite a complicated binary, which spawns several ARM tasks to enable the boot process:

- iBootStart (disassembly started above) - starts main (5FF00BCA) - which calls the main function at 5FF00C14 - main: Does the good stuff (loading the kernel, etc) starts the poweroff task (5FF00EF2) - calls (sub_5FF00FD0+1) In recovery mode (failed boot): starts command (5FF00F0A) - calls 5FF15928 starts idleoff (5FF99F2E) - calls 5FF01060

Revisions
iBoot-99             1.0b    (Build 1A420) [Unreleased] iBoot-159            1.0     (Build 1A543a) 1.0.1  (Build 1C25) 1.0.2  (Build 1C28) iBoot-204            1.1     (Build 3A100) 1.1    (Build 3A101) 1.1.1  (Build 3A109a) iBoot-204.0.2        1.1.1   (Build 3A110a) iBoot-204.2.9        1.1.2   (Build 3B48b) iBoot-204.3.14       1.1.3   (Build 4A93) 1.1.4  (Build 4A102) iBoot-204.3.16       1.1.5   (Build 4B1) ?                    1.2b    (Build 5A147p) ?                    2.0b2   (Build 5A225c) ?                    2.0b3   (Build 5A240d) ?                    2.0b4   (Build 5A258f) ?                    2.0b5   (Build 5A274d) ?                    2.0b6P  (Build 5A292g) ?                    2.0b6F  (Build 5A308) ?                    2.0b7   (Build 5A331) ?                    2.0b8GM (Build 5A345) iBoot-320.20         2.0     (Build 5A347) 2.0.1  (Build 5B108) 2.0.2  (Build 5C1) ?                    2.1b    (Build 5F90) iBoot-385.22         2.1     (Build 5F137) 2.1.1  (Build 5F138) ?                    2.2b    (Build 5G29) iBoot-385.49         2.2     (Build 5G77) 2.2    (Build 5G77a) 2.2.1  (Build 5H11) 2.2.1  (Build 5H11a) ?                    3.0b    (Build 7A238j) iBoot-594.2~1        3.0b2   (Build 7A259g) iBoot-596.6~3        3.0b3   (Build 7A280f) iBoot-596.16~2       3.0b4   (Build 7A300g) iBoot-596.20~1       3.0b5   (Build 7A312g) iBoot-596.24~1       3.0     (Build 7A341) 3.0.1  (Build 7A400) iBoot-636.26~2       3.1b    (Build 7C97d) iBoot-636.??~? 3.1b2  (Build 7C106c) iBoot-636.47~1       3.1b3   (Build 7C116a) iBoot-636.65~2       3.1     (Build 7C144) iBoot-636.66~1       3.1.1   (Build 7C145) 3.1.1  (Build 7C146) iBoot-636.66~5       3.1.2   (Build 7D11) iBoot-636.66.33~4    3.1.3   (Build 7E18) iBoot-817.28~18      3.2     (Build 7B367) iBoot-817.29~2       3.2.1   (Build 7B405) 3.2.2  (Build 7B500) iBoot-822.2.1        4.0b    (Build 8A2180g) [Unreleased] iBoot-872~12         4.0b    (Build 8A230m) iBoot-889.3~2        4.0b2   (Build 8A248c) iBoot-889.12~2       4.0b3   (Build 8A260b) iBoot-889.19~1       4.0b4   (Build 8A274b) iBoot-889.24~4       4.0GM   (Build 8A293) 4.0    (Build 8A293) 4.0.1  (Build 8A306) 4.0.2  (Build 8A400) iBoot-931.18.1~1     4.1b    (Build 8B5080c) iBoot-931.18.15~2    4.1b2   (Build 8B5091b) iBoot-931.18.27~1    4.1     (Build 8B117) 4.1    (Build 8B118) iBoot-931.67~2       4.2b    (Build 8C5091e) iBoot-931.71.80~1    4.2b2   (Build 8C5101c) iBoot-931.71.13~3    4.2b3   (Build 8C5115c) iBoot-931.71.16~9    4.2GM   (Build 8C134) 4.2GM  (Build 8C134b) 4.2.1GM (Build 8C148) 4.2.1  (Build 8C148) 4.2.1  (Build 8C148a) iBoot-931.72.14~6    4.2.5   (Build 8E128) 4.2.6  (Build 8E200) 4.2.7  (Build 8E303) 4.2.8  (Build 8E401) iBoot-931.72.14~10   4.2.9   (Build 8E501) 4.2.10 (Build 8E600) iBoot-1072.33~1      4.3b    (Build 8F5148b) iBoot-1072.38~2      4.3b2   (Build 8F5153d) iBoot-1072.49~2      4.3b3   (Build 8F5166b) iBoot-1072.58~4      4.3GM   (Build 8F190) 4.3    (Build 8F190) iBoot-1072.59~2      4.3     (Build 8F191) 4.3.1  (Build 8G4) iBoot-1072.61~2      4.3.2   (Build 8H7) 4.3.2  (Build 8H8) 4.3.3  (Build 8J2) 4.3.3  (Build 8J3) iBoot-1072.61~6      4.3.4   (Build 8K2) 4.3.5  (Build 8L1) iBoot-1219.35.80~1   5.0b    (Build 9A5220p) iBoot-1219.40.25~4   5.0b2   (Build 9A5248d) iBoot-1219.41.11~1   5.0b3   (Build 9A5259f) iBoot-1219.42.8~1    5.0b4   (Build 9A5274d) iBoot-1219.43.9~3    5.0b5   (Build 9A5288d) iBoot-1219.43.18~3   5.0b6   (Build 9A5302b) iBoot-1219.43.27~1   5.0b7   (Build 9A5313e) iBoot-1219.43.32~15  5.0GM   (Build 9A332) [Unreleased] 5.0GM  (Build 9A334) 5.0    (Build 9A334) iBoot-1219.43.32~27  5.0.1b1 (Build 9A402) iBoot-1219.43.32~29  5.0.1b2 (Build 9A404) 5.0.1  (Build 9A405) 5.0.1  (Build 9A406) iBoot-1219.61.19~6   5.1b    (Build 9B5117b) iBoot-1219.62.1~2    5.1b2   (Build 9B5127c) iBoot-1219.62.8~5    5.1b3   (Build 9B5141a) iBoot-1219.62.15     5.1     (Build 9B176) iBoot-1219.62.15~2   5.1     (Build 9B179b) 5.1.1  (Build 9B206) iBoot-1537.1.60~15   6.0b    (Build 10A5316k) iBoot-1537.2.11~5    6.0b2   (Build 10A5338d) iBoot-1537.2.81~1    6.0b3   (Build 10A5355d) iBoot-1537.2.41~2    6.0b4   (Build 10A5376e) iBoot-1537.4.18~2    6.0GM   (Build 10A403) 6.0    (Build 10A403) iBoot-1537.4.19~1    6.0     (Build 10A405) 6.0    (Build 10A406) iBoot-1537.4.20~1    6.0     (Build 10A407) iBoot-1537.4.21~3    6.0.1   (Build 10A523) 6.0.1  (Build 10A525) iBoot-1537.4.21~2    6.0.1   (Build 10A8426) 6.0.2  (Build 10A8500) iBoot-1537.4.21~3    6.0.2   (Build 10A550) 6.0.2  (Build 10A551) iBoot-1537.9.40~3    6.1b    (Build 10B5095f) iBoot-1537.9.46~8    6.1b2   (Build 10B5105c) 6.1b3  (Build 10B5117b) 6.1b4  (Build 10B5126b) iBoot-1537.9.55~4    6.1b5   (Build 10B141) 6.1b5  (Build 10B142) 6.1b5  (Build 10B143) 6.1b5  (Build 10B144) 6.1    (Build 10B141) 6.1    (Build 10B142) 6.1    (Build 10B143) 6.1    (Build 10B144) 6.1.1b (Build 10B311) 6.1.1  (Build 10B145) 6.1.2  (Build 10B146) 6.1.2  (Build 10B147) iBoot-1537.9.55~11   6.1.3b2 (Build 10B318) 6.1.3b2 (Build 10B318a) 6.1.3  (Build 10B329) 6.1.4  (Build 10B350) 6.1.5  (Build 10B400) 6.1.6  (Build 10B500) iBoot-1940.1.8~44    7.0b    (Build 11A4372q) iBoot-1940.1.35~9    7.0b2   (Build 11A4400f) iBoot-1940.1.46.1.1~1 7.0b3  (Build 11A4414e) iBoot-1940.1.66~9    7.0b4   (Build 11A4435d) iBoot-1940.1.75~3    7.0b5   (Build 11A4449a) 7.0b6  (Build 11A4449d) iBoot-1940.1.75~20   7.0GM   (Build 11A465) 7.0    (Build 11A465) iBoot-1940.1.75~93   7.0.1   (Build 11A470a) 7.0.2  (Build 11A501) iBoot-1940.3.5~1     7.0.3   (Build 11B511) 7.0.4  (Build 11B554a) 7.0.5  (Build 11B601) 7.0.6  (Build 11B651) iBoot-1940.10.51~3   7.1b    (Build 11D5099e) iBoot-1940.10.57~8   7.1b2   (Build 11D5115d) iBoot-1940.10.58~11  7.1b3   (Build 11D5127c) iBoot-1940.10.58~32  7.1b4   (Build 11D5134c) iBoot-1940.10.58~70  7.1b5   (Build 11D5145e) iBoot-1940.10.58~115 7.1     (Build 11D167) 7.1    (Build 11D169) iBoot-1940.10.58~122 7.1.1   (Build 11D201) iBoot-1940.10.58~132 7.1.2   (Build 11D257) iBoot-2261.1.6.0.1~45 8.0b   (Build 12A4265u) iBoot-2261.1.31~21   8.0b2   (Build 12A4297e) iBoot-2261.1.46~31   8.0b3   (Build 12A4318c) iBoot-2261.1.57~43   8.0b4   (Build 12A4331d) iBoot-2261.1.64~28   8.0b5   (Build 12A4345d) iBoot-2261.1.67~8    8.0GM   (Build 12A365) 8.0    (Build 12A365) 8.0    (Build 12A366) iBoot-2261.1.68~1    8.0.1   (Build 12A402) 8.0.2  (Build 12A405) iBoot-2261.3.31~3    8.1b    (Build 12B401) iBoot-2261.3.31~9    8.1b2   (Build 12B407) iBoot-2261.3.32~2    8.1     (Build 12B410) 8.1    (Build 12B411) iBoot-2261.3.33~13   8.1.1b  (Build 12B432) iBoot-2261.3.33~14   8.1.1   (Build 12B435) 8.1.1  (Build 12B436) 8.1.2  (Build 12B440) iBoot-2261.3.33~39   8.1.3   (Build 12B446) iBoot-2261.5.34~3    8.2b    (Build 12D436) iBoot-2261.5.41~10   8.2b2   (Build 12D445d) iBoot-2261.5.47~1    8.2b3   (Build 12D5452a) iBoot-2261.5.54~3    8.2b4   (Build 12D5461b) iBoot-2261.5.58~25   8.2b5   (Build 12D5480a) iBoot-2261.5.64~15   8.2     (Build 12D508) iBoot-2261.??.??~?? 8.3b   (Build 12F5027d) iBoot-2261.??.??~?? 8.3b2  (Build 12F5037c) iBoot-2261.20.19~16  8.3b3   (Build 12F5047f) iBoot-2261.20.20~9   8.3b4   (Build 12F61) iBoot-2261.20.20~14  8.3     (Build 12F69) iBoot-2261.30.33     8.4b    (Build 12H4074d) iBoot-2261.30.34~8   8.4b2   (Build 12H4086d) iBoot-2261.30.35~21  8.4b3   (Build 12H4098c) iBoot-2261.30.37~17  8.4b4   (Build 12H4125a) iBoot-2261.30.37~34  8.4     (Build 12H143) iBoot-2261.30.37~39  8.4.1b  (Build 12H304) iBoot-2261.30.37~55  8.4.1b2 (Build 12H318) iBoot-2261.30.37~58  8.4.1   (Build 12H321) iBoot-2817.0.0.1.2   9.0b    (Build 13A4254v) iBoot-2817.1.41.1.1~1 9.0b2  (Build 13A4280e) iBoot-2817.1.55~10   9.0b3   (Build 13A4293g) iBoot-2817.1.73~9    9.0b4   (Build 13A4305g) iBoot-2817.1.89~3    9.0b5   (Build 13A4325c) iBoot-2817.1.93~1    9.0GM   (Build 13A340) iBoot-2817.1.93~1    9.0     (Build 13A340) 9.0    (Build 13A342) 9.0    (Build 13A343) 9.0    (Build 13A344) iBoot-2817.1.94~1    9.0.1   (Build 13A404) 9.0.1  (Build 13A405) iBoot-2817.10.26~8   9.1b    (Build 13B5110e) iBoot-2817.10.29~16  9.1b2   (Build 13B5119e)

Apple TV (iOS)
iBoot-931.44.21~1   4.0     4.1     (Build 8M89) iBoot-931.71.16~9   4.1     4.2     (Build 8C150) 4.1.1  4.2.1   (Build 8C154) iBoot-1072.33~1     4.2b    4.3b    (Build 8F5148b) iBoot-1072.38~2     4.2b2   4.3b2   (Build 8F5153d) iBoot-1072.49~2     4.2b3   4.3b3   (Build 8F5166b) iBoot-1072.59~2     4.2     4.3     (Build 8F191m) 4.2.1  4.3     (Build 8F202) 4.2.2  4.3     (Build 8F305) 4.3    4.3     (Build 8F455) iBoot-1219.35.80~1  4.4b    5.0b    (Build 9A5220p) iBoot-1219.40.25~4  4.4b2   5.0b2   (Build 9A5248d) iBoot-1219.41.11~1  4.4b3   5.0b3   (Build 9A5259f) iBoot-1219.43.9~3   4.4b5   5.0b5   (Build 9A5288d) iBoot-1219.43.18~3  4.4b6   5.0b6   (Build 9A5302b) iBoot-1219.43.27~1  4.4b7   5.0b7   (Build 9A5313e) iBoot-1219.43.32~21 4.4     5.0     (Build 9A334v) iBoot-1219.43.32~22 4.4.1   5.0     (Build 9A335a) 4.4.2  5.0     (Build 9A336a) iBoot-1219.43.32~29 4.4.3   5.0.1   (Build 9A405l) 4.4.4  5.0.1   (Build 9A406a) iBoot-1219.62.1~2   5.0b2   5.1b2   (Build 9B5127c) iBoot-1219.62.8~5   5.0b3   5.1b3   (Build 9B5141a) iBoot-1219.62.15~2  5.0     5.1     (Build 9B179b) iBoot-1537.1.60~15  5.1b    6.0b    (Build 10A5316k) iBoot-1537.2.11~5   5.1b2   6.0b2   (Build 10A5338d) iBoot-1537.2.81~1   5.1b3   6.0b3   (Build 10A5355d) iBoot-1537.2.41~2   5.1b4   6.0b4   (Build 10A5376e) iBoot-1537.4.19~1   5.1     6.0     (Build 10A406e) iBoot-1537.4.21~3   5.1.1   6.0.1   (Build 10A831) iBoot-1537.9.40~3   5.2b    6.1b    (Build 10B5095f) iBoot-1537.9.46~8   5.2b2   6.1b2   (Build 10B5105c) 5.2b3  6.1b3   (Build 10B5117d) 5.2b4  6.1b4   (Build 10B5126d) iBoot-1537.9.55~4   5.2     6.1     (Build 10B144b) iBoot-1537.9.55~11  5.2.1   6.1.3   (Build 10B329a) iBoot-1537.9.55~11  5.3     6.1.4   (Build 10B809) iBoot-1940.1.8~44   5.4b    7.0b    (Build 11A4372q) iBoot-1940.1.35~9   5.4b2   7.0b2   (Build 11A4400f) iBoot-1940.1.66~9   6.0b3   7.0b4   (Build 11A4435d) iBoot-1940.1.75~3   6.0b4   7.0b5   (Build 11A4449a) iBoot-1940.1.75~93  6.0     7.0.1   (Build 11A470e) 6.0    7.0.2   (Build 11A502) iBoot-1940.3.5~1    6.0.1   7.0.3   (Build 11B511d) 6.0.2  7.0.4   (Build 11B554a) iBoot-1940.10.51~3  6.1b    7.1b    (Build 11D5099e) iBoot-1940.10.57~8  6.1b2   7.1b2   (Build 11D5115d) iBoot-1940.10.58~11 6.1b3   7.1b3   (Build 11D5127c) iBoot-1940.10.58~32 6.1b4   7.1b4   (Build 11D5134c) iBoot-1940.10.58~70 6.1b5   7.1b5   (Build 11D5145e) iBoot-1940.10.58~115 6.1    7.1     (Build 11D167) iBoot-1940.10.58~122 6.1.1  7.1.1   (Build 11D201c) iBoot-1940.10.58~132 6.2    7.1.2   (Build 11D257c) 6.2.1  7.1.2   (Build 12A365b) iBoot-2261.1.31~21  7.0b    8.0b    (Build 12A4297e) iBoot-2261.1.46~31  7.0b2   8.0b3   (Build 12A4318c) iBoot-2261.1.57~43  7.0b3   8.0b4   (Build 12A4331d) iBoot-2261.1.64~28  7.0b4   8.0b5   (Build 12A4345d) iBoot-2261.1.67~8   7.0GM   8.0GM   (Build 12A365b) 7.0    8.0     (Build 12A365b) iBoot-2261.3.31~3   7.0.1b  8.1b    (Build 12B401) iBoot-2261.3.31~9   7.0.1b2 8.1b2   (Build 12B407) iBoot-2261.3.32~2   7.0.1   8.1     (Build 12B410a) iBoot-2261.3.33~13  7.0.2b  8.1.1b  (Build 12B432) iBoot-2261.3.33~14  7.0.2   8.1.1   (Build 12B435) iBoot-2261.3.33~39  7.0.3   8.1.3   (Build 12B446) iBoot-2261.?.??~?? 7.1b   8.2b5   (Build 12D5480a) iBoot-2261.5.64~15  7.1     8.2     (Build 12D508) iBoot-2261.?.??~?? 7.1b2  8.3b2   (Build 12F5037c) iBoot-2261.20.20~9  7.1b3   8.3b4   (Build 12F61) iBoot-2261.20.20~14 7.2     8.3     (Build 12F69)

Apple TV (tvOS)
iBoot-2817.10.22~26 9.0b     9.0     (Build 13T5347l) iBoot-2817.10.29~9  9.0b2    9.0     (Build 13T5365h)

Haywire
iBoot-1537.9.55~3     1.0.0   (Build 10B7129)

Apple Watch
iBoot-2261.5.64~16    1.0        8.2      (Build 12S507) iBoot-2261.5.64~49    1.0.1      8.2.1    (Build 12S632) iBoot-2817.0.0.2.1~1  2.0b2      9.0b2    (Build 13S5255c) iBoot-2817.2.2~2      2.0        9.0      (Build 13S344)

Exploits
On 1st February, 2014, iH8sn0w found a very powerful iBoot exploit that allows any iDevice with an A5 or A5X chip to be jailbroken, regardless of the iOS version. He used it mainly to grab AES decryption keys. However, according to this tweet from winocm, the exploit will never go public. Once he cleans it up a bit, the decryption keys will be available here. He mentioned here that it will work on A6 and A7 chips soon, but it will require some minor modifications.

Commands used as an exploit vector

 * diags: Until 2.0 beta 6, the diags command would jump to code at the address provided to it. For example, if you sent "diags 0x9000000", it would directly jump to the code at 0x9000000. There is now a check that only allows engineering devices to utilize this backdoor.
 * arm7_go: For firmware 2.1.1, the iPod touch 2G iBoot contains the ARM7 Go command, which could be used to run a payload on the ARM7 in the device.

OpeniBoot
There is an open source version of iBoot designed so that custom kernels can be run on the iPhone/iPod/iPad. You can check out the source here. It is VERY useful if you are ever reversing iBoot and do not feel like finding out what certain hardware registers are yourself. OpeniBoot currently supports all S5l8900, S5l8720, S5l8920 and S5l8930 devices. More info can be found about OpeniBoot and Linux on these devices on the iDroid-Project website.

Remappings
// n88 (3GS) 0x4FF00000 => 0x0 0x40000000 => 0xC0000000